Water Resources and Water Management

WATER RESOURCESAND WATER MANACEMENT DEVELOPMENTS I N WATER SCIENCE, 28 OTHER TITLES I N THW SERIES 1 G. BUGLIARELLO ...

Author: Milan K. Jermar

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WATER RESOURCESAND WATER MANACEMENT

DEVELOPMENTS I N WATER SCIENCE, 28 OTHER TITLES I N THW SERIES

1 G. BUGLIARELLO AND F. GUNTER COMPUTER SYSTEMS A N D WATER RESOURCES H.L. GOLTERMAN PHYSIOLOGICAL LIMNOLOGY

2

Y.Y. HAIMES, W.A. H A L L AND H.T. FREEDMAN MULTIOBJECTIVE OPTIMIZATION I N WATER RESOURCES SYSTEMS: THE SURROGATE WORTH TRADE-OFFMETHOD

3

J.J. FRIED GROUNDWATER POLLUTION

4

N. RAJARATNAM TURBULENT JETS

5

6 D. STEPHENSON PIPELINE DESIGN FOR WATER ENGINEERS

v. HALEK AND J. SVEC 7 GROUNDWATER HYDRAULICS 8 J.BALEK HYDROLOGY A N D WATER RESOURCES I N TROPICAL AFRICA 9 T.A.McMAHONANDR.G.MElN RESERVOIR CAPACITY A N D YIELD

10 G.KOVAC5 SEEPAGE HYDRAULICS 11 W.H. GRAF AND C.H. MORTIMER (EDITORS) HYDRODYNAMICS OF LAKES: PROCEEDINGS OF A SYMPOSIUN 12-13 OCTOBER 1978, LAUSANNE, SWITZERLAND

12 W. BACK AND D.A. STEPHENSON (EDITORS) CONTEMPORARY HYDROGEOLOGY: THE GEORGE BURKE MAXEY MEMORIAL VOLUME 13 M.A. M A R I ~ ~AND O J.N. LUTHIN SEEPAGE A N D GROUNDWATER 14 D. STEPHENSON STORMWATER HYDROLOGY A N D DRAINAGE 15 D. STEPHENSON PIPELINE DESIGN FOR WATER ENGINEERS (completely revised edition of Vol. 6 i n the series) 16 w. BACK AND R . L ~ T O L L E(EDITORS) SYMPOSIUM ON GEOCHEMISTRY OF GROUNDWATER 17 A.H. ELSHAARAWI (EDITOR) I N COLLABORATION WITH S.R. ESTERBY TIME SERIESMETHODS I N HYDROSCIENCES 18 J.BALEK HYDROLOGY A N D WATER RESOURCES I N TROPICAL REGIONS 19 D. STEPHENSON PIPEFLOW ANALYSIS I.ZAVOIANU MORPHOMETRY OF DRAINAGE BASINS

20

21 M.M.A. SHAHIN HYDROLOGY OF THE NILE BASIN

22 H.C.RlGGS STREAMFLOW CHARACTERISTICS

23 M. NEGULESCU MUNICIPAL WASTEWATER TREATMENT L.G. EVERETT GROUNDWATER MONITORING HANDBOOK FOR COAL AND O I L SHALE DEVELOPMENT

24

25 W. KINZELBACH GROUNDWATER MODELLING: A N INTRODUCTION WITH SAMPLE PROGRAMS I N BASIC D. STEPHENSON AND M.E. MEADOWS KINEMATIC HYDROLOGY AND MODELLING

26

27 A.M. E L SHAARAWI AND R.E. KWIATKOWSKI (EDITORS) STATISTICAL ASPECTS OF WATER QUALITY MONITORING - PROCEEDINGS OF THE WORKSHOP HELD A T THE CANADIAN CENTRE FOR INLAND WATERS, OCTOBER 1985

WATER RESOURCES AND WATER MANAGEMENT MILAN K. JERMAR Becker Gundhalstr., 18,0-8000Munchen 71, F.R.G.

E LSEVl E R Amsterdam - Oxford - New York

- Tokyo

1987

ELSEVIER SCIENCE PUBLISHERS B.V. Sara Burgerhartstraat 25 P.O. Box 21 1, 1000 AE Amsterdam, The Netherlands

Distributors for the United States and Canada: ELSEVIER SCIENCE PUBLISHING COMPANY INC. 52, Vanderbilt Avenue New York, N.Y. 10017, U S A .

Lihrsrv I d C(r*i!gressCataloginl-in-Publicofion Data

J e r m a r , M i l a n K. W a t e r r ~ s o u r c e s a n d w a t e r management. ( D e v e l o p m e n t s in w a t e r s c i e n c e ; 28) B i b l i o g r a p h y : p. I n c l u d e s index. 1. Water-supply. 2. H y d r o l o g i c cycle. .. 1 1 . Series.

TD345.Jh7 1987 553.7 ISBN 0-444-42717-1 (U.S.)

1. Title.

86-24114

ISBN 0-444-42717-1 (Val. 28) ISBN 0-444-41669-2 (Series) 0 Elsevier Science Publishers B.V., 1987 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the publisher, Elsevier Science Publishers B.V./Science & Technology Division, P.O. Box 330, 1000 A H Amsterdam, The Netherlands. Special regulations for readers in the USA - This publication has been registered with the Copyright Clearance Center fnc. ICCC), Salem, Massachusetts. Information can be obtained from the CCC about conditons under which photocopies of parts of this publication may be made in the USA. All other copyright questions, including photocopying outside of the USA, should be referred to the publisher. Printed in The Netherlands

V

C O N T E m Page Chapter 1

WATER OCCURRENCE AND ITS FUNCTION I N NATIJRAL SYSTENS

1.1

SYSTEMS OF THE NATITRAT, ENVIRONMENT

1.2

ENERGY INPUT AS A CALJSE OF

1.3

HYDROLOGIC CYCTX SYSTEM

THE HYDROIBGIC CYCLE

1

3 8

1.3.1

Evaporation

10

1.3.2

Precipitation

18

1.3.3

Interception

21

1.3.4

Depression and Detention Storage; Overland Flow

22

1.3.5

Infiltration

23

1.3.6

Subsurface Water Movement

25

1.3.7

Flow i n Channel Network

32

1.4

INTERREMITION OF SURFACE AND GROUNDWATER RUNOFF

1.5

GROUNDWATER LEVEL REGTJTATION, SOIL kDISTURE AND SOIL

33

STRUCTURE FORMATION

40

1.6

CLIMATOLOGICAL FUNCTIONS OF WATER

45

1.7

AICGEOCHENICATJ CYCLE SYSTEM

50

1.7.1

Cycle

55

Water Quality a s a Product of i t s C i r c u l a t i o n

60

HYDROLOGIC CYCLE AS REGULATOR OF B1OZI)GICAL PROCESSES

71

1.7.2

I .8

Water Erosion a s a Process Evoked by t h e Water

1.8.1

I n t e r r e l a t i o n s h i p s of Aquatic Ecosystems and Water Q u a l i t y

1.9

RUNOFF PROCESS AS REGITLATOR OF THE LIVING ENVIRONMENT

77

83

VI

Chapter 2

WATE3 AND ITS FLWCTION I N SOCIA;, SYSTENS

2.1

CATEGORIES OF WATER mILIZATION

86

2.2

WATER REQUIREYEFTS AND WATER CONSUMPTION

88

2.3

IN-STRmY AND ON-SITE WATER USE

93

2.3.1

Waste Disposal

94

2.3.2

Inland \.!a t e r Transport

103

2.3.3

Water Power U t i l i z a t i o n

111

2.3.4

Water f o r Recreation

115

2.4

X D I C I P A L AND RURAL WATER REQUIREMENTS

2.4.1

2.5

Nater Requirements f o r Drinking and Cooking Purposes

121

2.4.2

Water Requirements f o r Other Domestic Uses

130

2.4.3

Urban Public Water Requirements

134

2.4.4

Management of Water Delivery and Disposal

139

INDTJSTRIAL WATER SUPPLY

2.5.1

AND RE-USE SYSTEMS

144

Water f o r Processing, Nining and Hydraulic Transport

153

2.5.2

Cooling Water

155

2.5.3

Boiling and Steam Power Water

157

2.5.4

Water Losses i n Industry and F l m Chart of

2.5.5 2.6

120

Water Use

160

Waste [.la ters and Was t e - f r e e Technologies

165

WATER I N A G R I C I L T U W L SYSTEE

169

2.6.1

A g r i c u l t u r a l Production and A g r i c u l t u r a l Yield

I72

2.6.2

E f f i c i e n c y of I r r i g a t i o n Water IJse

181

2.6.3

Water for I r r i g a t i o n and i t s Q u a l i t y

185

VII

Chapter 3

2.6.4

I r r i g a t i o n a s Supplementary Watering

187

2.6.5

F e r t i l i z i n g and Remedial I r r i g a t i o n

191

2.6.6

Protective Irrigation

194

2.6.7

Soil kaching IrriEation

195

2.6.8

Irrigation bsses

197

2.6.9

Water f o r Livestock and Processing

2 04

2.6.10

Water P o l l u t i o n from Agricultural Production

2 01

WATER BALANCE AND WATER SYSTm

3.1

CHARACTERISTICS OF SURFACE AND GROUNDWATER RESOURCES

211

3.2

SAFE YIELD

213

3.3

BALANCE OF WATER RESOURCES AND NEEDS

220

3.4

MINIMUM WATER TABLE . &TI MINIMUM DISCHARGES

225

3.5

ACTIVE AND PASSIVE WATER BAIANCE

229

3.6

PROBABILITY OF THE SATISFACTION OF bJATER REQUIREMEIVE

233

3.7

FLOW CONTROL AND OPERATING SCHEDIJLES

239

3.8

SYSTENS I N WATER RESOIRCES MANAGEMENT

245

3.9

ANAJJYSIS AND MODELLTNG OF WATER RESOURCES SYSTENS

247

3.10 ECONOMIC OPTIMIZATION AND FINANCIAL APL4LYSIS

3.11 Chapter 4

PLANNING WDEL BASED ON PHYSICAL PARAMETERS

255 259

IMPACT OF DEVEJDPWNT ACTIVITIES ON THE HYDROIXIC CYCLE

4.1

CHANGES I N THE HYDROJDGICAL DATA

262

4.2

CHANGES I N THE HYDROLCGICAL BALANCE

265

4.3

INFLUENCE OF FORESTRY AND AGRICULTURE

271

4.3.1

I n t e r c e p t i o n , Evapotranspiration and I n f i l t r a t i o n

274

4.3.2

Influence of t h e Vegetative Canopy on Floods and Erosion

4.3.3

277

Influence of t h e Vegetative Canopy on R a i n f a l l and Runoff

2 82

VIII

4.4

INFJ,UENCE OF URBANIZATION AND INDlJSTRIAL,IZATION

2 87

4.5

CHANGES I N WATER QIJALITY

2 92

4.6

ENVIRONMENTAT, IMPACTS OF WATER DEVELOPMENT PROJECTS

299

4.6.1

Effects of Reservoirs and I r r i g a t i o n Systems on Climate

4.6.2

Effect of Reservoirs and Dam on Sediment Transport

309

4.6.3

Effect of Reservoirs on Water Quality

316

4.6.4

Effects of Man-made Lakes on the Biosphere

324

4.6.5

Effects of Flow Control and Water TJithdrawals

330

4.6.6

Effects of River Training and @en Channel Water Conveyance

Chapter 5

3 03

336

WATER DEVEIOPMENT AND MANAGEMENT POLICY

5.1

WATER MANAGEMENT ACTIVITIES AND ORGANIZATIONS

341

5.2

PARADOXES OF WATER RESOURCES DEVEIBPMEXI'

344

5.3

STRATEGY OF WATER RESOURCES DEVEIOPMENT

346

5.4

TACTICS OF WATER MANAGEMENT

351

5.5

NON-CONVENTIONAL TECHNIQUES OF WATER SUPPLY

361

5.5.1

Long-Distance Water Conveyance and Transportation

361

5.5.2

Conjunctive Use of Surface and Groundwater

5.6

Resources

3 63

5.5.3

Groundwater Mining and A r t i f i c i a l Recharge

366

5.5.4

Watershed Management

368

5.5.5

Weather Modification

370

5.5.6

Desalination and Treatment of bw-Quality Waters

372

CONCLIJSIONS

IX

IITRODIJCTION

Water is a substance which plays a c r u c i a l p a r t i n the existence o f l i f e on Earth. I t forms t h e l i v i n g mass and, together with the s o i l and t h e a i r , r e p r e s e n t s t h e l i v i n g environment. The energy which is accepted by t h i s system from the universe helps t o s u s t a i n e s s e n t i a l l i f e processes. The hydrological cycle, o r the process of permanent movement and transformation of water, connects the human being with a l l t h e elements of t h i s environment i n such a manner t h a t any change r e s u l t s i n a chain of consequences which spread throughout the ecologic a l system. For b i l l i o n s of years t h e development of t h e ecosystem was determined by the i n t e r p l a y of uncertain causes. A fundamental change occurred w i t h the emergence of c i v i l i z a t i o n . Man s t a r t e d t o influence t h i s system i n t e h t i o n a l l y and systematically: gradually mankind's everyday existence came t o have a more s e r i o u s and detrimental e f f e c t on t h e environment. Up u n t i l now t h e energy which mankind used during h i s development has been n e g l i g i b l e i n comparison with the amount of energy used through n a t u r a l processes. Nevertheless, even t h e water management and a g r i c i i l t u r a l a c t i v i t i e s of a n c i e n t c i v i l i z a t i o n s already had a d r a s t i c and i r r e p a r a b l e impact on waste a r e a s a s a r e s u l t of systematic e f f o r t s over long periods of time. Today t h e march of technology appears i r r e p r e s i b l e and i r r e v e r s i b l e throughout t h e world. The process of d e f o r e s t a t i o n , land c u l t i v a t i o n , urbanization and i n d u s t r i a l i z a t i o n a r e r a p i d l y changing t h e c h a r a c t e r of t h e e a r t h ' s s u r f a c e and the q u a l i t y of t h e water, s o i l and a i r , a s well a s a f f e c t i n g t h e acceptance of s o l a r energy. The s c a l e of these human a c t i v i t i e s has now reached such a proportion t h a t t h e impact of one s i n g l e generation is comparable with t h e impact of a l l preceding generations. The a m u n t o f energy c u r r e n t l y manipulated by man

is no longer n e g l i g i b l e i n comparison with t h e t o t a l a m u n t of energy used d u r ing n a t u r a l processes. C i v i l i z a t i o n confines t h e world and mankind t o mnotonous, unambiguous s t r u c t u r e s which a r e very d i f f i c u l t t o control e f f e c t i v e l y . Man a l t e r s t h e n a t u r a l equilibrium without considering t h e global consequences of h i s a c t i o n s . I n t h e course of a few decades he i s a b l e t o exhaust some natu-

X

r a l resources and i r r e v e r s i b l y p o l l u t e h i s environment. An unfavourahle accumul a t i o n of the negative consequences of h i s a c t i v i t i e s , t r a n s f e r r e d i n t h e framework of t h e hydrological c y c l e , threatens hi:; own existence. Man has s t a r ted t o l i v e a t t h e c o s t of f u t u r e generations. The r o o t s of t h i s incomprehensible s i t u a t i o n l i e not only i n mankind's m i s guided endeavour t o achieve maximum economic b e n e f i t s through minimum e f f o r t s and without considering secondary e f f e c t s , b u t a l s o i n h i s t r a d i t i o n a l thinking processes. These were formed i n t h e period when man s t i l l observed n a t u r a l phenomena s e p a r a t e l y , without taking account of t h e i r i n t e r r e l a t i o n s h i p . I n the p a s t t h e observer of n a t u r a l phenomena i n one s c i e n t i f i c d i s c i p l i n e had no reason t o follow up t h e i r i n t e r - d i s c i p l i n a r y r e l a t i o n s h i p s . The i n t e r r e l a t i o n s h i p of n a t u r a l phenomena and t h e l i k e l y consequences of such a r e l a t i o n s h i p

were not taken i n t o consideration.

This s i t u a t i o n is a l s o r e f l e c t e d i n t h e f i e l d of water resources. The theor e t i c a l background t o t h i s f i e l d i s t r a d i t i o n a l l y formed by: - h y d r a u l i c s ( t h e study of t h e physical r e f l i l a r i t i e s of water motion and function) ; hydrochemistry ( t h e study of t h e p h y s i c a l , chemical, b i o l o g i c a l and bacte-

-

r i o l o g i c a l p r o p e r t i e s of water) ; - hydrology ( t h e study of t h e time and space d i s t r i b u t i o n of various aspects of t h e hydrological cycle) and

-

I

hydrogeology ( t h e study of t h e occurrence and mvgnent of subterranean

waters and t h e i r geological environment). ?he d e s c r i p t i v e s c i e n t i f i c d i s c i p l i n e s a r e concerned with t h e study of two d i f f e r e n t c a t e g o r i e s of phenomena. The f i r s t category comprises phenomena which a r e based on simple r e l a t i o n ships among s e v e r a l v a r i a b l e s . Here i t is necessary t o neglect those v a r i a b l e s whose influence is unimportant and t o d e r i v e the mathematical r e l a t i o n s h i p s among these v a r i a b l e s whose influence is decisive.

The second category includes phenomena with a high degree of occurrence. Here it i s n o t necessary t o t r a c e t h e i r mutual r e l a t i o n s h i p s , b u t r a t h e r t o study t h e r e s u l t of t h e i r i n t e r p l a y , when t h e r e l a t i o n s between causes and consequences a r e t o be determined and c l a s s i f i e d on t h e b a s i s of s t a t i s t i c a l methods and t h e theory of p r o b a b i l i t y . However t h e s i z e and number of water p r o j e c t s and o t h e r development a c t i v i ties which influence t h e hydrological cycle have reached such proportions t h a t the majority of problems involved extend beyond t h e boundaries of the above t r a d i t i o n a l d i s c i p l i n e s . These problems cannot be solved with t h e t o o l s of the above methods. Present-day water management problems a r e i n t e r d i s c i p l i n a r y i n n a t u r e and a s such include complex phenomena with complicated mutual i n t e r r e l a t i o n s h i p s . These i n t e r r e l a t i o n s h i p s a r e more important than t h e number of

XI

v a r i a b l e s involved. It is not enough t o i n v e s t i g a t e these problems by researching s e l e c t e d im portant v a r i a b l e s and r e l a t i o n s h i p s . Using s t a t i s t i c a l methods and t h e theory of p r o b a b i l i t y f o r t h i s purpose represents a complicated mathematical e x e r c i s e with only l i t t l e relevance t o r e a l i t y . Such an approach is unlikely t o lead to the desired goal. The s o l u t i o n of i n t e r - d i s c i p l i n a r y problems i n water development and management p r a c t i c e on the b a s i s of the t r a d i t i o n a l approach tends t o ignore the key development and environmental f a c t o r s . This leads among o t h e r things to : - the s e p a r a t e development of e i t h e r s u r f a c e o r groundwater resources, - t h e use of high q u a l i t y water f o r low q u a l i t y requirements and v i c e versa, - t h e over-excessive use of water f o r c e r t a i n purposes, thus i n h i b i t i n g o r excluding m r e valuable u s e s , - t h e neglecting of water re-use, water re-cycling, and waste material recovery p o s s i b i l i t i e s and o t h e r water saving p r a c t i c e s , - t h e l o s s of n u t r i e n t s or raw m a t e r i a l s from t h e place of i m e d i a t e o r potent i a l l y easy u t i l i z a t i o n , and t h e neglecting of important secondary a s p e c t s , c o n s t r a i n t s and hazards of

-

many water and o t h e r development p r o j e c t s . The t r a d i t i o n a l approach i s a l s o one of t h e reasons o f :

-

over-excessive use of n a t u r a l resources, t h e i n c r e a s i n g d e t e r i o r a t i o n of t h e n a t u r a l environment, and the economic f a i l u r e of many water development p r o j e c t s . When i n v e s t i g a t i n g contemporary water development and management problems

including t h e i r e c o l o g i c a l , economic and s o c i a l a s p e c t s , i t is necessary t o analyze a l a r g e n m b e r of elements whose i n t e r r e l a t i o n s h i p s depend on the prev a i l i n g conditions. Such problems can be solved by l i m i t i n g t h e problem a r e a , simplifying i t t o t h e p o i n t of a n a l y t i c t r a c t a b i l i t y , and defining systems which preserve a l l v i t a l a s p e c t s a f f e c t e d by various p o s s i b l e amendments. A l l important elements and dynamic i n t e r r e l a t i o n s h i p s should be analyzed and not j u s t g e n e r a l l y , but a l s o on t h e b a s i s of t h e i r s p e c i f i c behaviour. I t is necessary t o employ a combination o f d i f f e r e n t p r o b a b i l i s t i c and a n a l y t i c methods, including modelling and i n v e s t i g a t i n g the s e n s i t i v i t y of t h e outputs t o t h e assumptions rrade and t o f a c e t s of t h e problem excluded from t h e f o m l a n a l y s i s .

Ney s c i e n t i f i c methods f o r t h e s o l u t i o n of t h e contemporary problems i n water management include analogy, o p e r a t i o n research, system a n a l y s i s and cybernetics. The d i s t i n c t i v e f e a t u r e s of these methods a r e t h e i r emphasis on measurement and on t h e use of conceptual models described i n q u a n t i t a t i v e t e r n , the v e r i f i c a t i o n of t h e i r t h e o r e t i c a l p r e d i c t i o n s , and t h e i r awareness t h a t concepts a r e conditional and s u b j e c t t o growth and continuous change.

This new approach should be defined within the framework of water resources management, i . e . within a complex of a c t i v i t i e s whose objective i s the optimum u t i l i z a t i o n of water resources with regard to t h e i r q u a l i t y and a v a i l a b i l i t y and the requirements of society. These water management a c t i v i t i e s should a t the same time a l s o ensure an optimum l i v i n g environment, above a l l through prot e c t i o n of water resources against deterioration and exhailstion a s well a s through the protection o f society against the harmful e f f e c t s of water. In the course of these a c t i v i t i e s water resources management should a v a i l i t s e l f of the e n t i r e spectrum of e x p l i c i t sciences, gradually coming t o form the sphere of i t s own theory. The present monograph deals with the fundamental i n t e r d i s c i p l i n a r y problems of t h i s complex sphere, an understanding of which i s indispensable for successf u l water resources mnagement i n the widest sense of i t s s o c i a l functions and environmental consequences.

1

Chapter 1

WATER OCCIJRRENCE AND ITS FUNCTION I N NATURAL SYSTJZMS

1.1 SYSTFNS OF THE NAATURAZ, ENVIRONMENT Water e x i s t s a s s c a t t e r e d humidity and a s s p a t i a l l y limited water formations below, on and above the Earth's surface. Water resources a r e water formations which can be u t i l i z e d by human society. Water and water formations a r e dynamic; they a r e always i n motion and t h e i r s t a t e of aggregation is forever changing. R e s e processes continue without i n t e r r u p t i o n , change i n space and time and trans form the n a t u r a l environment. The natural environment i s formed by a number of systems, o r complexes of mutually i n t e r r e l a t e d elements, whose relationships within the framework of these complexes a r e more important than t h e i r relations with the elements of other systems. I n the important p a r t of the n a t u r a l environment which constitutes the object of the present investigation i t i s possible to distinguish: (a) a b i o t i c systems, created by water, s o i l and a i r elements and characterized by: - morphological (topographical) d a t a

-

pedological and geological data ( s o i l is a mixed abiotic-biological element) hydrogeological and hydrometeorological data (b) biotic-biological systems (ecosys tems) , originating with the develop-

ment of l i v i n g matter i n a defined p a r t of the a b i o t i c environment and (c) socio-economic sys tems , i e. administrative, econcmic and technica 1

.

systems (Fig. 1.1) originating with the formation of human society and possessing important interconnections with the above two systems. The natural environment of Earth represents a semi-closed system. The input of matter i n t o t h i s system from outer space is negligible. The movement of matter inside t h i s system i s enabled by an input of energy, consisting mainly of s o l a r energy and the i n t e r n a l energy of Earth i t s e l f . This system, due t o i t s own homeostatic mechanisms and d e t e c t o r s , tends t o achieve a s t a t e of equilibrium balancing accidental deflections from t h i s s t a t e . The material couplings which form i n t e r r e l a t i o n s among these systems include: - biotic-abiotic couplings, e.g. the quantity of dissolved oxygen caused by the decay of a biomass abiotic-biotic couplings, e.g. the dependence of the i n t e n s i t y of biological

-

processes on water temperature

-

socio-abiotic couplings, e.g. as manifested especially by the h p a c t of

urbanization, i n d u s t r i a l i z a t i o n and a g r i c u l t u r a l production on runoff and sedimen t transport

2

-

socio-abiotic-biotic couplings, e.g. a s manifested by the r o l e of urbani-

zation, industrialization and intensive agricultural production i n polluting c e r t a i n ecosys tans

.

\

SYSTEMS

Fig. 1.1. The penetration of matter and energy through the a b i o t i c and b i o t i c ( a l s o socio-economic) systems. The equilibrium of relevant systems and its recovery depend on the energy and matter input: R detector, HM - hornyostatic mechanisms.

-

These material couplings a l s o form complex i n t e r r e l a t i o n s , such a s the

socio-abiotic-biotic-social i n t e r r e l a t i o n manifested by the influence of industrialization and the subsequent water pollution and eutrophication on

.

water u t i l i z a t i o n . The task of analyzing these interrelationships among the various systems is complicated not only by the complexity of the couplings and interrelations concerned, but a l s o by the lack of data available (Fig. 1.2). As only selected couplings a r e operationally controllable, only a few can be checked systematically. Moreover, because data monitoring i s neither cmplex nor f u l l y systematic, the relevant s e r i e s of data i n the different categories do not mutually correspond and a r e therefore inadequate. Furthermore, frequently undesirable secondary couplings occur and have a negative influence on the function of the system i n question, sometimes bringing about a gradual change i n the sys tern's behaviour .

Ihe movement of water and other matter within and between these systems changes i n t i m e and space: The importance of individual relations i s variable. Regarded i n this way the doctrine of water management concerns the s t r u c t u r e and the function of systems, thus enabling the water t o f u l f i l l its natural functions and t o be u t i l i z e d f o r the various present and future requirements

3

Fig. 1 . 2 . Basic productive inputs and outputs of a b i o t i c and b i o t i c systems. Monitored, i . e . s y s t e m t i c a l l y checked inputs a r e marked by a c i r c l e ; accidental, undesired outputs a r e marked by white arrows. 1.2

ENERGY INPUT AS A CAUSE OF THE HM)RO-iDGIC CYCLE

The Earth r e f l e c t s a p a r t of the external energy input which it receives, d i s t r i b u t i n g the r e s t between the a i r , water, s o i l and geological formations and radiating p a r t of i t back i n t o the Universe. "he basic equation of the energy balance expresses t h e law of the conservation of energy (Fig. 1.3)

- Jg

Ju

.

Ju

- sun and other

9 J

z?

-

( 1

-9

=

6

.Jk

(m*.kg.s-*)

radiation from the IJniverse (short wave)

albedo ( c o e f f i c i e n t of r e f l e c t i o n ) global radiation (long wave)

- energy J2 - energy J3 - energy J1

)

supply t o the atmosphere supply t o the hydrosphere supply to the pedosphere and lithosphere

(1.1)

4

J4

- enera

supply to the biosphere

Fig. 1.3. Basic inter.rrlat.ions of the systecls of atmosphere, lithosphere and pedosphere a s well a s the hydrosphere: movement of m t t e r i n the gravi ational f i e l d , enabled by the supply of energy, forming the main input. The input of m t t e r from the universe i s negligible.

F

The Earth r e f l e c t s on average 34% of the energy input. The coefficient of reflection, the albedo, depends essentially on the character and morphology of the surface, the s t a t e and quality of the atmosphere above, as well a s on the angle of incidence of the rays. Stretches of water r e f l e c t 10%of the energy on average, lawns 15%, forests 20%, deserts 30%and snow 80%. The type of

energy u t i l i z a t i o n changes with the character of the surface: 90% of the energy input is consumed by evaporation above oceans, while above continents the figure i s only 50%. The global average temperature of the a i r is not changing a t present. The energy balance does not demonstrate any increment i n the component: JI = 0 . I n average the basic equation of the energy balance, a l s o taking i n t o account the fact that the energy supply to the biosphere is relatively small, can be simplified a s follows: . Je = J2 + J3 Je

-

(m 2 .kp.s-2 )

effective radiation

The r e s u l t of the acceptance of the effective radiation are fluctuations i n the s o i l and water temperature, accompanied by evaporation with sublimition.

5 These processes change the state of water aggregation i n t o a gaseous one. The s p e c i f i c weight of water vapour is lower than t h a t of a i r . Water vapour r i s e s and i n t h i s way i t acquires p o s i t i o n energy. The thermal energy thus regenerates the mechanical energy of water and causes the c i r c u l a t i o n of water. The hydrol o g i c a l c y c l e i s an uninterrupted process of water motion and changes of aggregation i n t h e systems of t h e b i o l o g i c a l and a b i o t i c environment. The d i f f e r e n c e between the s p e c i f i c and l a t e n t h e a t of fusion and vaporization, whose values a r e a p p r o x i m t e l y two and t h r e e orders high r e s p e c t i v e l y , balances t h i s process during a higher o r lower energy input. The mechanical energy c o n s i s t s of the p o s i t i o n energy, the pressure energy and the k i n e t i c energy. Jh = m.g.h

The p o s i t i o n e n e r a

(m2.kg.s-2)

m

- mass

(kg)

g

-

(9.81 m.s-2)

h

- head

g r a v i t a t i o n a l constant

(m)

Pressure energy p

J = m . L

9

P

- pressure

Kinetic energy

-

v e l o c i t y of flow

(m2.kg.s-2)

.

(m-l. kg sH2)

- water d e n s i t y , u n i t mass of water

v

(1.3)

J

k

2 = m V

T

(kg .m-3)

(m2. kg .s - ~ )

(1.5)

(m.s-l)

,

The q u a n t i t y of water i n water courses forms only 0.002% of the t o t a l global water reserves. The proportion of water power p o t e n t i a l of water courses is only 0.4% of t h e 6.4

. lo3'

of energy which the Earth continuously receives

from t h e Universe. But i t is twenty times higher than the percentage of water courses volume i n r e l a t i o n t o t o t a l global water reserves because of t h e high head formed by geomorphological conditions. P o s i t i o n energy a c t s a s pressure energy and changes i n t o k i n e t i c energy, depending on t h e physical conditions. This k i n e t i c energy together with chemical energy of water and changes i n volume during ice formation, transforms s o i l and rock formations a l s o forming and changing r i v e r beds. The growth and changes i n ecosystems a r e a l s o enabled by the e f f e c t of t h e mechanical, thermal and chemical energy of water. By accepting and e m i t t i n g energy, water molecules change t h e i r p o s i t i o n and

state of aggregation during their course through the b i o l o g i c a l and a b i o t i c systems of t h e n a t u r a l environment. The law of conservation of energy during t h i s cycle expresses the equation of hydrological equilibrium:

6

P1

- vertical

P2

- horizontal

Q,

-

precipitation precipitation (see paragraph 1.3.2)

surface outflow (channel and overland flow)

Q2 - subsurface outflow (groundwater runoff) Q3 - deep percolation and juvenile water inflow El

-

evaporation frcm bare s o i l surface

E2

-

evaporation from free water surfaces

E3

- evaporation

E

-

4

from snow and i c e

evapotranspiration

R 1 - water increment (or decrement) in s o i l s and rock formations R2

- water

R3

- water

increment (or decrement) i n the atmosphere

R4

- water

increment of the flora

R5

- water

increment of the fauna.

increment (or decrement) i n water courses and reservoirs i n c l . depression and detention storage

The area and period of application of t h i s equation can be established i n such a way that relevant increments or decrements i n volume and the deep percolation or water supply from deep s t r a t a are negligible, thus simplifying the formula : P 1 + P 2 = Q 1 f Q2 + k=l & E k

(m3

(1.7)

This hydrological equation simply s t a t e s that the t o t a l evaporation and the difference between t h e t o t a l inflow and outflow (concentrated and overland runoff, groundwater runoff) i s formed by the precipitation and the dew deposit.

Data on the e a r t h ' s water reserves vary within a range of 210%.KORZUN and SOKOIDV (1976) estimated them a t 1,386 mld. krn3 , of which sane 2.53% or only 35 m i l . k m 3 , are fresh water reserves. The t o t a l annual evaporation is 577,000

km3 : 505,000 km3 on sea surfaces, 72,000 km3 on continental surfaces. Groundwater reserves 'exceed five thousand times the amount of water i n a l l rivers, brooks and creeks. 50% of the groundwater is below the level of 1000 meters under the e a r t h ' s surface (Tab. 1.1). Of basic importance in t h i s context is the recycling r a t e , which indicates the duration of the natural exchange of the relevant volume of water: i n the case of water courses this r a t e i s 3.4 .104 times as high as for groundwater.

7

TABLE I.. 1 ~

5 P e of format ion

Areg (10 2

kn 1

Ocean

361

Brackish groundwater Lakes

134.8 0.822

'Total

497

Groundwater Soil water

134.8 82

Volume (1g3

Layer (m)

Share total water

3700

96.5

km)

1 3 3 8 000 12 870 85.4 1 351 000

10 530 16.5

96 103.8 3660 78 0.2

0.94 0.006

97.45

(%) on

fresh reserves

~

Period of replenishment (years)

0

2500

0 0

1400 17

0

-

0.76 0.001

30.1 0.05

1400 1

Icebergs : Antarctic Greenland Arctic Mountain

13.98 1.80 0.23 0.22

Permafrost

21

21 600 2 340 83 41

1540 1298 369 181

1.56 0.17 0.006 0.003

61.7 6.7 0.24 0.12

9700 9700 9700 1600

300

14

0.022

0.86

10000

73.6 4.28 0.014 0.002 0.025

0.007 0.009 0.0002 0.0001 0.001

0.26 0.03 0.006 0.003 0.04

Fresh water: Lakes Marshes Watercourses Biosphere Amsphere Fresh water reserves Total water reserves

1.236 2.682 148.8

-

510

91.0 11.5 2.1 1.1 12.9

148

35 029

235

510

1 386 000

2719

2.55

100

100

2.55

17 5 16 d l h 8 d

-

World,water reserves and the share of different water bodies i n the resewe of the t o t a l volume of water and i n the volume of fresh water according to Sokolov (1981). The period of exchange of t h e i r volume by natural recharge (d - days, h - hour)

a O f the 145.103 km2 of c o n t i n e n t a l s u r f a c e s only two t h i r d s (100.10 3 km2 ) a r e

s u i t a b l e f o r water development, 25.10 3 km2 being permafrost, 14.103 krn2 icebergs and 6.103 km2 extremely a r i d land.

1.3 HYDROLEIC CYCLE SYSTEM The complicated processes of t h e hydrologic cycle include evaporation, prec i p i t a t i o n , i n t e r c e p t i o n and s u r f a c e s t o r a g e , i n f i l t r a t i o n and p e r c o l a t i o n , s u r f a c e and groundwater runoff. The catchment a r e a , i . e . the area which d r a i n s i n t o one place and thus cont r i b u t e s t o t h e runoff i n the p r o f i l e i n question, is an open system whose boundary crosses energy, water, a i r and s o i l / r o c k p a r t i c l e s . P o t e n t i a l energy of p o s i t i o n , thermal and chemical energy w i t h i n t h i s system, is transformed i n t o k i n e t i c energy and h e a t . Water, suspended, wash and bed load a s well a s f l o a t i n g d e b r i s a r e transported from the upper elevations towards the sea (and p a r t i a l l y v i c e versa e.g. by sand dune movement) and transfomed. Erosion, crushing, chemical and biochemical processes a r e a n i n t e g r a l p a r t of the water cycle (Fig. 1.4). The system of t h e catchment a r e a tends to achieve a steady state of operat i o n , corresponding t o t h e conditions of c l b a te, topography, geology and ecology, c h a r a c t e r i z e d a l s o by the f a c t t h a t the water and d e b r i s output corresponds t o a s p e c i f i c energy input. Any change e.g. by r i v e r t r a i n i n g , r e s e r v o i r construction, land c u l t i v a t i o n , urbanization and i n d u s t r i a l i z a t i o n ,

is a change of system elements and of t h e energy i n p u t , thus r e s u l t i n g i n the change of output . The state of t h i s system is t o be followed i n i t s s p a t i a l elements (Fig. 1.4). Three equations of balance can be formulated f o r each of these elements: - hydrologic balance (Fig. 4.1) - f a l l - o u t , e r o s i o n and d e b r i s balance - e n e r g e t i c balance. I n any s p a t i a l e l e m e n t due t o t h e equilibrium of t h e atmosphere branch, the p r e c i p i t a t i o n , the evaporation and t h e increment of atmosphere moisture eqcal t o the d i f f e r e n c e of water vapour e n t e r i n g and leaving the element: An

- An+I

An

- water vapour

An+l

= Rn + Pn

- water

-

En

(m3)

e n t e r i n g t h e s p a t i a l element n

vapour leaving the s p a t i a l element n

Pn

- precipitation

En

- evaporation

R,

-

and dew d e p o s i t i n t h e element n

i n the element n

a i r moisture increment i n t h e element n .

9

n

n-l

Fig. 1.4. Equation of hydrological equilibrium, the transport of mss and biogeochemical cycles a s subsystems of the water cycle. Explanation of symbols and main equations is given i n the t e x t . Precipitation i s formed by external water vapour supply A - An+l and by intern ~l evaporation E .

n'

Pn = An

- An+l

+ En

-

Rn

(1.9)

but Pn = Q, + En (see equation 1 . 7 ) and, therefore, An

- An+l

+ En

An

- An+l

=

Internal

4,

- Rn +

Rn

= Qn + En

(1.10)

evaporation over continents is generally lower than the external

water supply, requiring m r e energy and resulting i n the generally prevailing evaporation on the sea surface. This f a c t can be expressed by the water circu-

10 lation r a t i o , defined as

(1.11)

The value of- t h i s r a t i o over vaste areas is quite stable, e.g. for North America mm = 1.25, Asia and Europe mae = 1.51. 1 . 3 . 1 Evaporation Evaporation is a physical process by which water changes from the liquid s t a t e t o the vapour s t a t e through the transfer o i thermal energy. The change from s o l i d s t a t e without passing the usual intermediate liquid aggregation i s called sublimation. Evaporation i s the key process i n the water cycle: (a) i t i s the only one of the processes i n t h i s cycle during which the energy input exceeds the energy output, (b) i t accounts for the creation of living m t t e r . Evaporation takes place particularly on the boundary of the atmosphere and the hydro-, pedo-, and biosphere, thus making it possible t o distinguish: evaporation from open water surfaces, evaporation from bare s o i l surfaces, evaporation from snow and i c e , evaporation of water intercepted by vegetation, evapotranspiration from s o i l and vegetative cover, evapotranspiration of vegetative cover on water surfaces, evaporation from organic bodies and moist materials, evaporation i n the atmosphere. Evapotranspiration includes s o i l evaporation and the evaporation of water which i s absorbed by crops, used i n the building of plant tissue and transpired. The quantity of water evapotranspirated by plants and relevant s o i l surfaces per annum with the increment i n plant t i s s u e i s the consumptive use of plants. The hydroloEic balance can be expressed generally o r f o r a limited element of the lithosphere by the f o l l m i n g equation: ET = E + T = P, + R~ +

ET E T P Ri W

-

w -Q -F

(m3

(1.12)

evapotranspiration evaporation transpiration

- precipitation

- irrigation -

increase of water moisture caused by capillary forces from the groundwater

11 (+) or decrease by water consumption of crops (-)

Q F

- deep p e r c o l a t i o n - water chemically

and drained water and b i o l o g i c a l l y absorbed and used i n the building of the p l a n t t i s s u e (+), o r eliminated from the organic matter (-), e . g . by gut t a t i o n .

The r a t e of evaporation depends on the state of the systems whose i c t e r a c t i o n enables i t s course. The atmosphere influences t h i s course by m e t e o r o l e g i c a l f a c t o r s , namely by s o l a r r a d i a t i o n , humidity and by a i r movement leading away water vapours. The r e l a t i o n s h i p between r a d i a t i o n and evaporation can be expressed f o r a l i m i t e d p a r t of the hydro- o r t h e l i t h o s p h e r e ( r e s e r v o i r , f o r e s t , f i e l d e t c . ) by the equation (1.13) Je

-

effective solar radiation

Jh

-

h e a t accepted by t h e hydro- o r l i t h o - and biosphere

Ja

- heat

Jx

- l a t e n t h e a t used

t r a n s f e r r e d back t o the atmosphere f o r evaporation and evapotranspiration

The value and r a t i o of a l l these f a c t o r s a l s o change a t the same place i n the course of the y e a r (Fig. 1.5) Ja

i

AT

(1.14)

x=Dp Albrecht (1951) s i m p l i f i e s t h e equation f o r evaporation E =

Je - Jh 1 +%d

- temperature increment - a i r pressure increment 0: - c o e f f i c i e n t

AT AP

(1.15)

(% (Pa)

The t r a n s f e r of s o l a r energy is g r e a t l y influenced by overshadowing and by meteorological f a c t o r s , namely by the humidity of t h e a i r , p r e c i p i t a t i o n , a i r temperature and pressure a s w e l l a s t h e v e l o c i t y of i t s movement. Temperature and a i r p r e s s u r e do n o t influence evaporation d i r e c t l y . They c h a r a c t e r i z e the quantity of accepted energy. The humidity and a i r flow which a c c e l e r a t e the evaporation by t h e exchange of s a t u r a t e d a i r s t r a t a above t h e evaporating surface a r e a l s o i n c i d e n t a l phenomena of the energy t r a n s f e r to t h e atmosphere. They function a s r e w l a t i n g f a c t o r s of t h e evaporation and t r a n s p i r a t i o n r a t e .

12

-2 h 0

P n

Y0 E

4

-3

"Q

0

-1

'

5

4

6

7

8

9

10

month

Fig. 1.5. The annual course of the energy balance (Lake Haussee according t o measurements of Czepa and Schellmbergpr (1956). The energy input Jg i s part i a l l y r a d i a t e d (Jr), p a r t i a l l y t r a n s f e r r e d t o the atmosphere (J,) by the cont a c t of the water t a b l e and t h e a i r m s s . Je i s used f o r evaporation and Jt causes t h e change of water temperature. The imnediate cause of the evaporation process is the d i f f e r e n c e i n humidity between the i n t e r n a l and e x t e r n a l

-

or the s a t u r a t e d and unsaturated

-

system

of environment. I t can be characterized by the evaporation from s u r f a c e a s rel a t i v e humidity, i , e . t h e r a t i o of the a c t u a l water vapour pressure e (Pa) and t h e maximum

pressure E (Pa) which t h e a i r i s a b l e t o accept a t the a c t u a l

temperature. The d i f f e r e n c e between these values is the s a t u r a t i o n complement d = E - e

/Pa)

(1.16)

Rraslavskij and Vikulina (1954) assessed t h e following p r a c t i c a l formula f o r t h e computation of the evaporation from open water surfaces on the b a s i s of the a i r humidity and wind v e l o c i t y

Eva = 0.013

.

(eo

-

e2)

.

( 1 + 0.72 v2)

(1.17)

(m p e r day)

EV,

- monthly

eo

- rraximum water

e,

-

monthly average of water vapour p r e s s u r e 2 m above the water surface (m)

v2

-

average wind v e l o c i t y a t an e l e v a t i o n of 2 m above the water surface(m.s-l)

average of evaporation

vapour pressure, corresponding t o the average temperature of the water s u r f a c e (m)

Sermer (1960) e s t a b l i s h e d t h e r e l a t i o n between t h e temperature and the evaporat i o n from open water s u r f a c e f o r the conditions of Central Europe a s follows (0,0452 T Evd = 10

-

0.104)

T - average monthly temperature 2 m above the water s u r f a c e

(1.18) (OC)

Evaporation from snow and ice i s f i v e t o ten times lower than evaporation

from f r e e water s u r f a c e s . Due t o t h e lower temperature and s o l i d s t a t e of snow

13 and i c e , much m r e energy i s needed f o r the same intensity of its course. The evaporation r a t e from ice i s about 50 t o 100% higher than the evaporation from snow under the same conditions, because the heat conductivity of snow i s lower. Therefore

EM > E I > ES

(m)

(1.19)

- evaporation from open water surface EI ES

-

evaporation from ice evaporation from snow surface.

The value of evapotranspiratior; from overgrown water surfaces depend on the kind and the t o t a l quantity of the vegetable m t t e r . The evaporation from overgrown surfaces does not d i f f e r greatly from the evaporation from open water surfaces, when the water surface is only covered by f l o a t i n g leaves. But i t exceeds i t twice i n the case of the densely overgrown edges of reservoirs. Therefore

m => -

(m)

ELl

(1.20)

evapotranspiration from overgrown water surface.

Evaporation frcm bare s o i l does not depend on heat input only, characterized by meteorological factors, but a l s o on the s o i l f a c t o r s , namely on - the structure and other physical properties of the s o i l , the s o i l moisture , the contact of the s o i l layer with the groundwater surface (Fig. 1.6).

-

-

w

E

rnrn

(010)

i6

E

% 50

12

40

8 4

0

40

20

30 t c

DEPTH

Fig. 1..6. (a) I n t e r r e l a t i o n of the evaporation from the free water surface, the a i r humidity and the a i r temperature according t o Dub (1957). (b) Relation of the evaporation from the groundwater table on i t s depth, expressed a s the r a t i o of the evaporation from free water surface. Derived according to White (1970). These internal factors function clearly i n the case of lower s o i l saturation. The evaporation from bare s o i l s a l s o depends on the velocity of water inflow t o the surface. Inadequate water inflow lowers the evaporation r a t e .

14 Actual evaporation from bare s o i l s is, t h e r e f o r e , lower than the p o t e n t i a l r a t e , whose value depends on the energy supply only. Values of t h e p o t e n t i a l evaporation from b a r e s o i l s almost equal those from open water s u r f a c e s , when water evaporates d i r e c t l y from t h e wetted topographic s u r f a c e . Under conditions of a dry s u r f a c e l a y e r s , a s Penman (1940) proved, water vapour p e n e t r a t e s t h i s l a y e r by d i f f u s i o n , which lowers the values of evaporation. Evaporation from bare s o i l s takes p l a c e ( a ) i n c o n t a c t with t h e groundwater s u r f a c e , r e g u l a t i n g the s o i l moisture, o r , more f r e q u e n t l y , (b) without outstanding c o n t a c t with the groundwater s u r f a c e , when the suspended c a p i l l a r y water of t h e s o i l p r o f i l e i s n o t connected with the c a p i l l a r y water supported by the groundwater l e v e l , and the r o o t system does n o t penet r a t e i n t o t h i s space, i . e . when t h e groundwater l e v e l is influenced by the conditions of t h e s o i l s u r f a c e by means of hygroscopic and osmotic forces and by the gas pressure only. Evaporation from groundwater s u r f a c e s depends namely on the depth of the groundwater l e v e l . The course of groundwater l e v e l changes i s not the same under the conditions of evapotranspiration: Relevant forces d i f f e r , e s p e c i a l l y during the day. They a l s o depend on the kind of vegetation, i t s root system, I

s t a g e of growth and q u a n t i t y of leaves.

Evaporation w i t h i n reach of a w e l l can be c a l c u l a t e d by neglecting the evaporation during the n i g h t , which i s comparatively low, a n t i c i p a t i n g t h a t the

rise i n water l e v e l i s uniform: El

El

Q,

.

v

s

.v

- evaporation well

Q,

(24

- s)

(1.s-I)

(1.21)

from t h e groundwater surface w i t h i n the reach of the measured (1.s-l)

- w e l l y i e l d during the decrease of water l e v e l by 1 m (1.s-I) - v e l o c i t y of water level r i s i n g during n i g h t (m per hour) - t o t a l i n c r e a s e of water l e v e l p e r day (m per day)

I n t h e most frequent case of evaporation from b a r e s o i l s without outstanding c o n t a c t w i t h ' t h e groundwater l e v e l , the value of the evaporation r a t e i n t h e i n i t i a l s t a g e is almost equal t o the p o t e n t i a i evaporation. The following s t a g e , beginning with a s u b s t a n t i a l lowering of t h e moisture of the s o i l surf a c e , is characterized by the decreasing v e l o c i t y of evaporation, which s t a b i l i z e s i n t h e f i n a l s t a g e a t a low value. Anticipating a uniform d i s t r i b u t i o n of t h e perpendicular v e l o c i t y , Kutilek (1978) proves t h a t

e = (Wi

5 - Wo) . 'n .)

(m.s-'>

(1.22)

15 e

-

W.

-W -

evaporati-on rate

(m.s-l)

d i f f e r e n c e of moisture content i n t h e s o i l s u r f a c e during time t (%)

0 -D1 - average

d i f u s s i v i t y of t h e s o i l w a t e r , depending on the s o i l category and kf . dh

moisture kf - h y d r a u l i c c o n d u c t i v i t y h

-

t

- time

M

- c o n s t a n t of

pressure h e i g h t

s o i l properties.

T r a n s p i r a t i o n , t h e evaporation of water absorbed by a crop and not used i n the b u i l d i n g of p l a n t t i s s u e , may be above a l l s t o m t a l b u t a l s o appears a s c u t i c u l a r o r a s g u t t a t i o n o r exudates from c u t s u r f a c e s of t h e p l a n t . Transp i r a t i o n depends on p h y s i o l o g i c a l and environment (meteorological) f a c t o r s , e . g . daytime. P h y s i o l o g i c a l f a c t o r s i n c l a d e ( a ) t h e physiological s t r u c t u r e of r e l e v a n t p l a n t types, the age of t h e i r organ.; and t h e n a t u r e of t h e i r c e l l u l a r membranes, (b)

t h e a c t u a l s t a t e of the r e l e v a n t i n d i v i d u a l p l a n t , i . e . the degree of

n u t r i t i o n , namely w a t e r c o n t e n t of i t s c e l l s and water vapoyr content i n t h e t r a n s p i r a tory organs. Under c o n d i t i o n s of s u f f i c i e n t moisture and n u t r i t i o n f o r t h e development of i n d i v i d u a l p l a n t s , t h e i n t e n s i t y of t r a n s p i r a t i o n depends e s p e c i a l l y on envir o m e n t a l f a c t o r s , namely on s o l a r r a d i a t i o n , wind v e l o c i t y and s o i l moisture. The temperature of t h e l e a f exposed t o t h e sun is h i g h e r than t h a t of the a i r . In the case of a n i n s u f f i c i e n t supply of water and n u t r i t i o n , t h e i n t e n s i t y of t r a n s p i r a t i o n depends more on t h e above-mentioned i n t e r n a l p h y s i c a l f a c t o r s (Tab. 1 . 2 ) . The p l a n t e x e r c i s e s a l i m i t e d c o n t r o l on the t r a n s p i r a t i o n r a t e . Stomata IJSlJallY

open i n t h e l i g h t . They c l o s e w i t h reduced moisture and when the sugar

content d e c r e a s e s , changing t o s t a r c h , as happens i n t h e dark o r a t t h e end of the v e g e t a t i o n season, when leaves t u r n yellow. T r a n s p i r a t i o n is a l s o reduced i n the case of abundant water. The movement of water from t h e r o o t zone, through t h e stem and l e a v e s , is enabled by d i f f u s i o n and osmosis. The r a t e of both these processes is influenced by a i r moisture and energy supply, r e s u l t i n g i n t h e removal of water vapour next t o t h e l e a f s u r f a c e . Van Den Honert (1948) expressed t r a n s p i r a t i o n by physiological analogy w i t h OHM'S law

(1.23) T

-

transpiration r a t e

16 TABLE 1 . 2

Term,

Definition

IJsage

Theoretical value derived from energy input

Energy budget

S I P

Po ten t i a l

evaporation (evapora t i v i t y ) ET1

Ap

-

s a t u r a t e d vapour pressure increment

r - psychrometric Js

-

constant

energy input

Jg - energy t r a n s f e r Po t e n t i a 1

Evapotranspiration from s o i l and

Water balances f o r

evapotranspiration

vegetation sys tern, s a t u r a t e d with

long term planning

ET P

water and nutriments , derived from l o c a l hydrometeorological ccfiditions .

Optimal evapotrans-

Evapotranspiration from a surface

Determination of

p i r a t i o n ET OP t

whose s o i l moisture i s managed i n

p l a n t water and

order t o increase a g r i c u l t u r a l

i r r i g a t i o n require-

and f o r e s t r y production

ments

Highest evapotranspiration t h a t

Resistance a g a i n s t

r e l e v a n t vegetation system i s a b l e

moisture. Dimen-

t o achieve, dependent on i t s s t a g e of growth and a c t u a l state

sioning of the drainage.

Evapotranspiration of a p l o t i r r i g a t e d only f o r s u r v i v a l of

Resistance a g a i n s t drought

Maximum evapotransp i r a t i o n ET IlUX

Minimum evapotransp i r a t i o n ETmin

r e l e v a n t p l a n t species Actual evapotrans-

Real evapotranspiration dependent

p i r a t i o n ETa

OP

the growth s t a g e and state of

the p l a n t , measured by s o i l mois t u r e sampling, large-size lys imeters, zroundwater f l u c tua tioris Glossary of evapotranspiration.

Determination of actual irrigation rates

17 TABJX 1.3 ~

Cover

Bare s o i l

Grassland

Pine f o r e s t

X

Ratio

28.6

6.6

2.98

1.9 2.69

13.0

3.0

5.00

2.0

0.5 3.33

8.5

1.9 14.20

1.00

3.7

1 . 0 18.50

12.1

2.8 60.50

2.4

1.00

5.1

1.4 1.21

13.4

3.1 3.18

10.2

5.7

1.00

16.7

4.7

1.64

25.4

5.8 2.49

April

23.1

13.0

1.00

37.6

10.5

1.63

41.0

9.4

May

23.9

13.5

1.00

62.6

17.5 2.62

69.9

14.7 2.92

June

24.4

13.7

1.00

51.6

14.6 2.12

58.6

13.4 2.40

July

29.9

16.8

1.00

57.4 16.4 1.91

61.5

14.2

August

27.0

15.2

1.00

55.2

15.5 2.04

61.1

14.0 2.26

September

22.1

12.4

1.00

39.5

11.1 1.78

48.4

11.1 2.18

mrn

%

Share

m

October

9.6

5.4

1.00

18.2

5.1 1.75

November

2.6

1.5

1.00

7.0

December

0.6

0.3

1.00

January

0.2

0.1

February

4.2

March

Yearly t o t a l

177.8 100.0

1.00 ~

Share from

Loamy s o i l

Share

355.6 100.0 2.00 ~

50%

%

~~~~

Loamy s o i l

~

87%

f r e e surfac? evaporation

m

1.78

2.05

435.5 100.0 2.44 ~

~~

Depending on

70%

forest Sand

26%

Sandy s o i l

26%

density and age

Seasonal d i s t r i b u t i o n of evaporation and evapotranspiration, i t s dependence on the s o i l s u r f a c e and cover according t o Wechman (1963, Eberswalde, GDR). The share of evapotranspiration compared with the f r e e s u r f a c e evaporation according to Krecmer (1980).

18

-

evaporation rate

(m.s-’)

ys -

s o i l moisture p o t e n t i a l - s u c t i o n pressure of the s o i l water

(J.kg-’)

ye -

moisture p o t e n t i a l of the leaves

( J .kg-’)

et

rs

-

f l m r e s i s t a n c e of the s o i l

(Pa.s-1)

r

-

f l o w r e s i s t a n c e of the p l a n t

(Pa. s - l )

P

bLv - u n i t mss of the s o i l water

(k~.m-~)

The r a t i o of t r a n s p i r a t i o n and evaporation from s o i l changes a t one p o i n t i n time, namely during the vegetation season. A t the beginning of t h i s season, the evaporation from bare s o i l s dominates. Transpiration increases with the growing vegetation. Under the conditions of coherent p l a n t cover, t r a n s p i r a t i o n generally p r e v a i l s . Overshadowing of the s o i l surface by the v e g e t a t i v e canopy decreases the s o i l surface temperature and the r a t e of water vapour removal, thus causing a decrease i n t h e evaporation r a t e . Transpiration a l s o drops duri n g t h e period of ripening. Evapotranspiration is a complicated phenomenon, e x p l i c a b l e by a few values only ( s e e Tab. 1.2) complying with t h e following unevenness

ET1

>

ET P

>

ETm

>

ETo

>

ETa

>

ETmin

(1.24)

Under Central European conditions evapotranspiration by vegetation is generally higher than evaporation from bare s o i l s , but lower than evaporation from open water s u r f a c e s . Evapotranspiration from a r i d zone p l a n t s is o f t e n lower than evaporation from bare s o i l s . Gilimeroth (1951) and Kramer (1969) state t h a t evapotranspiration from vegetation never exceeds evaporation from s a t u r a t e d s o i l s a t the same l e v e l of exposure. 1.3.2

Precipitation

The p r e c i p i t a t i o n process i s the t r a n s f e r of water eliminated from the a t mosphere system t o t h e system of the hydro- and l i t h o s p h e r e , characterized by an output of the l a t e n t h e a t of vaporization. The number of d i f f e r e n t forms of p r e c i p i t a t i o n i s very l a r g e , but b a s i c a l l y p r e c i p i t a t i o n can be ( a ) v e r t i c a l , i . e . p r e c i p i t a t i o n from the upper p a r t of the atmosphere system, characterized by a v e r t i c a l movement of drops: d r i z z l e , r a i n , snow, g l a z e , h a i l , sleet e t c . , (b) h o r i z o n t a l , i . e . water eliminated by condensation o r sublimation on the ground: dew, hoar f r o s t , rime, diamond d u s t e t c . Depending on i t s s t a g e of agglomeration, p r e c i p i t a t i o n is e i t h e r l i q u i d o r s o l i d . I t is measured i n terms of depth (mn), r a i n f a l l i n t e n s i t y i n t e r n of

19

mn per minute. Rainfall is produced by a cooling of the a i r as the r e s u l t of a decrease i n the b a r m e t r i c pressure, by r a d i a t i o n , by c o n t a c t with a colder land o r sea surface o r during mixing of a i r masses. Condensation of water vapour i n t o cloud droplets takes place on condensation n u c l e i , formed by hygroscopic s a l t p a r t i c l e s . The f a l l i n g speed of d r o p l e t s is a function of t h e i r s i z e and of the speed of the a i r stream. The coalescence of t h e d r o p l e t s t o Eom raindrops is accounted f o r by the coexistence of t h e i c e c r y s t a l s and water d r o p l e t s and by the differences i n speed between l a r g e and small drops. The l a t e n t h e a t of evaporation r e g u l a t e s the process of condensation (Fig. 1 . 7 ) .

Fig. 1 . 7 . The subsystem of p r e c i p i t a t i o n and i t s processes i n dependence on the a1 t i t u d e according t o Mason (1957).

20 To sununarize the tendemy of r a i n t o occur i n d e f i n i t e p a t t e r n s , i t i s

p o s s i b l e t o d i s t i n g u i s h between: ( a ) l o c a l convective r a i n f a l l masses,

- caused

by the upward movement of a i r

(b) orographic r a i n f a l l - influenced by the morphology of the exposed p a r t of the higher mountain ranges and characterized by longer duration and lower intensity , ( c ) cyclonic r a i n - caused by the air-mass c o n t r a s t of cold and warm r a i n , i . e . by the excess of surface h e a t i n g i n lower l a t i t u d e s and of cold i n higher l a t i t u d e s , characterized by moderate l a s t i n g r a i n f a l l over a l a r g e a r e a , but a l s o by heavy r a i n , h a i l o r snowfall over a small a r e a . R a i n f a l l o f t e n occurs a s a combination of the above mentioned forms. Its occurrence, i n t e n s i t y and frequency depends on zonal, regional and l o c a l factors. The c o n t r a s t between surface h e a t i n g i n the equatorial and p o l a r zones, o r the d i f f e r e n c e i n temperature between t h e continent and t h e s e a , causes subs t a n t i a l movement of the a i r , which manifests t h e homeostasis of t h i s system, i . e . i t s tendency t o achieve a balanced, s t a b l e state. This mowment of a i r i s influenced by the r o t a t i o n of t h e Earth and by regional thermal and orographic f a c t o r s . Regions with a high h o r i z o n t a l inflow of water vapour and an upward movement of a i r masses a r e characterized by frequent p r e c i p i t p t i o n . The important influence of a r e g i o n ' s l a t i t u d e on the r a i n f a l l frequency i s evident : (a)

t h e e q u a t o r i a l zone has the h i g h e s t annual p r e c i p i t a t i o n on average

(50%of the global r a i n f a l l occurs between 20' N.L. and 2 0 ' S.L.), (b) a r e a s which have considerable r a i n f a l l cover middle and higher l a t i tudes, oceans and the western p a r t s of c o n t i n e n t s , (c)

a r e a s with p a s s a t winds and s t r i p s along the t r o p i c s a r e r a i n l e s s .

(d) p o l a r a r e a s a r e a l s o r a i n l e s s , obtaining 4 % of the t o t a l global precip i ta t ion. I n c e r t a i n c l i m t i c regions, p r e c i p i t a t i o n and i t s s t a t e of aggregation depends t o a g r e a t e x t e n t on the a l t i t u d e (Fig. 1 . 8 ) . The increment i n the r a i n f a l l t o t a l , corresponding t o the d i f f e r e n c e i n a l t i t u d e , is the r a i n f a l l gradient. Local f a c t o r s which influence the s p a t i a l d i s t r i b u t i o n of r a i n f a l l include geographical and morphological f a c t o r s , such a s t h e area exposure ( t o the d i r e c t i o n of wind), the c h a r a c t e r i s t i c of i t s surface (roughness, vegetative canopy), and the g r a d i e n t of the slope. R a i n f a l l i n t e n s i t y , very o f t e n unevenly d i s t r i b u t e d i n space and time, decreases on average with the a r e a s a f f e c t e d and with the r a i n f a l l duration. The unevenness of the space-time d i s t r i b u t i o n of the r a i n f a l l r e s u l t s i n a f l u c t u a t i o n of p r e c i p i t a t i o n during the year and i n a

21 f l u c t u a t i o n of annual average. Diiring periods of d e f f i c i e n t p r e c i p i t a t i o n the deviation from average i s g r e a t e r f o r r i v e r runoff than f o r r a i n f a l l . The complicated mechanism of p r e c i p i t a t i o n can be influenced i n p a r t i c u l a r by

-

changes i n the h e a t i n p u t , changes i n the a i r mass movement, increasing o r decreasing t h e q u a n t i t y of condensation nuclei.

The r e s u l t of any of these measures i s n o t e x p l i c i t , because the r e l e v a n t i n t e r r e l a t i o n s h i p s of the atmospheric sys tem a r e complicated And zi c e r t a i n feedback e x i s t s , such a s the atmospheric system's external re1at;ons with the hydro- and l i t h o s p h e r e and t h e s o l a r system, whose energy supply i s n o t uniform.

1 . 3 . 3 Interception I n t e r c e p t i o n is a process of p r e c i p i t a t i o n transmission and r e d i s t r i b u t i o n on the boundary of t h e systems of t h e atmosphere and the lithosphere by t h e vegetative canopy. The q u a n t i t y of p r e c i p i t a t i o n which a c t u a l l y reaches the ground, e f f e c t i v e rain- and snowfall, c o n s i s t s of t h e - throughfall , which reaches the ground d i r e c t l y through intershrub spaces and drips from t h e leaves, twigs and stems, and of the - stemflow which reaches the ground by running dawn the stems. I n t e r c e p t i o n loss i s the p a r t of p r e c i p i t a t i o n r e t a i n e d by the vegetative canopy and then evaporated o r absorbed. Therefore

(W

P =P-I F e P

I

- net

precipitation

- actual precipitation - i n t e r c e p t i o n loss

(above t h e v e g e t a t i v e canopy)

(m)

I = I1 + I2 I1

- i n t e r c e p t i o n by

I2

-

S

(1.26)

the z e r i a l portion of the vegetative canopy

i n t e r c e p t i o n of t h e l a y e r of shedded leaves and needles

(1.27)

Pe = T + S - I 2 T

(1.25)

- throughfall - stemflow I n t e r c e p t i o n loss during one s i n g l e r a i n f a l l c o n s i s t s of t h e i n t e r c e p t i o n

capacity of the surface of l e a v e s , twigs etc. and the amount evaporated and absorbed by p l a n t s : (1.28)

I =. I + Iea I.

- interception

capacity of leaves, twigs e t c .

22 Iea

- i n t e r c e p t i o n loss by evaporation and absorption

Absorption of water by p l a n t s during one s i n g l e r a i n f a l l is n e g l i g i b l e . For t h i s reason Linsley derives the following equation f o r t h e i n t e r c e p t i o n during one s i n g l e r a i n f a l l : 1 = 1+

d . E T . t

(m)

(1.29)

d - r a t i o of t h e t o t a l evapotranspiration and the evaporation from t h e vegeta-

t i o n s u r f a c e , depending on the r a t i o of the vegetative and non-vegetative surface

FT t

(s-l)

- evapotranspiration - r a i n f a l l duration The i n t e r c e p t i o n capacity depends on the composition of the r e l e v a n t l e v e l s

of t h e v e g e t a t i v e canopy, i t s morphology arid development s t a g e . This c a p a c i t y , which can be reduiced by preceding r a i n f a l l , influences the n e t p r e c i p i t a t i o n i n dependence upon the a c t u a l r a i n f a l l iritensi t:y, duration and ccurse a s weJ.1 a s upon the wind v e l o c i t y . An o v e r f u l f i l i i n g of t h i s int.erception capacity is c h a r a c t e r i z e d by a remarkable i n c r e a s e of s ternflow and throughfall (dripping). It goes wj. thout saying t h a t the intierception loss nuy exceed the i riterception 1 capac ipy. ZinLe (1967) e s t i m a t e s , without including c.he capacity o€ the shedcled leaves

and needles, the average i n t e r c e p t i o n capacity of nmst g r a s s e s , t r e e s and shrubs a t 1.3 mn during one s i n g l e r a i n f a l l and 3.8 mn during snowfall. He a l s o s t a t e s t h a t the i n t e r c e p t i o n loss is twice a s high i n 20% of t h e observed cases. The average i n t e r c e p t i o n l o s s of a c e r t a i n a r e a depends n o t only on the compos i t i o n of the v e g e t a t i v e canopy, i t s development s t a g e and a c t u a l state, but a l s o on t h e t i m e d i s t r i b u t i o n of t h e p r e c i p i t a t i m and the i n t e r p l a y of the r a i n f a l l occurrence with the course of temperature, humidity and wind v e l o c i t y . Depression and Detention Storage; Overland Flow 1.3.4 The e f f e c t i v e p r e c i p i t a t i o n reaching the e a r t h ' s s u r f a c e is p a r t l y s t o r e d ( a ) a f t e r snowfall a s snmpack, whose f u r t h e r e f f e c t on runoff depends on energy supply, i . e . on

-

r a d i a n t hea.t frcm the sun l a t e n t h e a t of vaporization released by t h e condensation of water vapour,

(b) by depression s t o r a g e i n s u r f a c e puddles and by s u r f a c e d e t e n t i o n formed by a s h e e t of water on t h e s o i l s u r f a c e . ( c ) a s channel s t o r a g e i n stream channels, ponds, swamps, e t c . Depression s t o r a g e i s n o t d i r e c t l y measurable and even d e t e n t i o n s t o r a g e is usually derived from hydrograph a n a l y s i s r a t h e r than from observation. Surface

23 runoff usually c m e n c e s from one part of a catchment area before the interception and depression storages i.n other p a r t s a r e s a t i s f i e d . Detention storage depends on the slope and surface roughness of the area, i . e . on the s o i l conditions, the vegetative cover and i t s s t a t e . The difference between types of vegetation a r e caused by the e f f e c t s of the l i t t e r , which appears to be more s i m i . f i c a n t than i r r e g u l a r i t i e s i n the s o i l surface. The surface runoff does not occur whenever the rai.nfa11 i n t e n s i t y does not exceed the i n f i l t r a t i o n and evaporation inter1si.Q. I n t h i s case t.he sur€ace runoff does not occix oiily during the f i r s t p a r t of the storm, when the interception, depression and detention storage capacities a r e not exceeded. As the rain continues, puddles become f u l l and the s o i l surface becomes covered with a sheet of water and downhill flow begins towards an established surface channel. A level p l a i n can a c c m u l a t e 3-18 m of water, meadows and f i e l d s 12-42 mn and f o r e s t s much more water, which gradually i n f i l t r a t e s and evaporates. when these limits a r e exceeded, spa t i a l l y varied unsteady flow during r a i n f a l l occurs, i n which the r a t e and depth of flow increase dawn the length of the flow path. This depth a l s o increases with time, even when the i n t e n s i t y of the r a i n f a l l renairis unchanged. For these conditions the r e l a tionship becomes D e = R . L . q De L q K

- volume of - length of

(1.30) detention when equilibrium flow condition is established (m3) flow

(m) (m 3 .s -1)

- discharge per meter width a t equilibrium - c o e f f i c i e n t of

r a i n f a l l i n t e n s i t y , slope and roughness of the surface

Where steady uniform overland flow i s considered (Tab. 1.5), the following relationship between r a t e of discharge and depth of overland flow can be theoret ica 1ly derived: Q = K . H m Q

H

m

-

(m2. s-l)

overland flow depth of flow

- c o e f f i c i e n t of

(m’.

s-l)

(m) slope and roughness (involving v i s c o s i t y ,

m = 3 f o r laminar flow, m = 1.67 f o r turbulent flow)

1.3.5

Infiltration

I n f i l t r a t i o n is a process of unsaturated o r saturated flow during the movement of water i n t o the pedo- and lithosphere, detructing the s o i l water and groundwater from the n e t p r e c i p i t a t i o n . Water t r i e s t o achieve a s t a t e of minimmn energy i n these systems and moves from levels of higher energy to levels of

24 1mer energy. Saturation depends on the porosity of s o i l o r rock and the moisture content. When the moisture content i s smaller than the porosity, the flow i s unsaturated. \ h e n it equals the porosity, the flow i s saturated. I t s r a t e depends on the e f f e c t i v e porosity, which i s usually expressed a s a percentage and defined by

(1.30) n

-

Vv

- volume

Vo

-

e f f e c t i v e porosity

(%)

of water governed by gravity forces i n the saturated s o i l o r rock ( i . e . the volume of a l l connected e f f e c t i v e pores and voids) (m3)

t o t a l volume of the s o i l o r rock (the volume of a l l pores and voids plus the volume of a l l the grains and s o l i d s ) (m3)

The e f f e c t i v e porosity i s a p a r t of the t o t a l porosity which enables the g r a v i t a t i o n a l movement of water. I t depends on s o i l texture and s t r u c t u r e (grain-size d i s t r i b u t i o n , mutually connected pores and cracks e t c . ) I n f i l t r a tion a l s o depends on the s t a t e of the s o i l surface i n c l . density of vegetation, moisture d i s t r i b u t i o n i n the s o i l layer, the a i r content i n non-capil lary pores, the temperature, the depth of the groundwater table and the i n t e n s i t y of the r a i n f a l l (high i n t e n s i t y r a i n f a l l causing compaction of the suirface l e v e l ) . The i n f i l t r a t i o n r a t e i s the maxirnun r a t e a t which the s o i l can absorb prec i p i t a t i o n i n a given condition. The i n i t i a l high r a t e of i n f i l t r a t i o n decreases exponentially: rapidly a t the beginning and then more slowly u n t i l i t approaches a constant r a t e a f t e r a period of 20 t o 120 minutes. P h i l i p (1958) expresses the a c t u a l i n f i l t r a t i o n r a t e by the formula

(1.33)

- actual infiltration rate s - sorptivity t - time of the beginning of vi

vk

(m.s-l) (m.s> imfiltration

- final stable infiltration rate

(s) (m.s-l>

S o r p t i v i t y can be defined by the equation

s* = k;

2 k;.

(%+

H)

- coefficien of k f 6 W5

. (Wo - W i )

(1.34)

the hydraulic (unsaturated) conductivity

(m. s-l) JT

- soil c h a r a c t e r i s t i c

(m>

(1.35)

25 Wo Wi

H

- f i n a l moisture content - moisture content a t t h e beginning - depth of groundwater t a b l e

(3

(m)

P h i l i p (1969) expresses the total value of i n f i l t r a t i o n by the sequence i n which the f i r s t two component p r e v a i l N n = S . tS +

Wn

V k .

- infiltration

t

total

(m)

(1.36)

(m)

The following prlicesses of unsaturated subsurface flow a r e interconnected with the i n f i l t r a t i o n r e d i s t r i b u t i o n , when s o i l water e n t e r s the layers with lower moisture con-

-

tent, percolation, when water leaves the s a t u r a t e d s o i l layers and e n t e r s the

-

groundwater , c a p i l l a r y r i s e , when the nmisture of the upper layers is supplemented from

-

the lmer ones, o r from the groundwater.

1.3.6 Subsurface Water Movements Subsurface water forms the subsurface hydrosphere i n the heterogeneous environment of the s o i l and hydrogeological s t r u c t u r e s , which occurs i n d i f f e r e n t forms (Tab. 1:5). The subsurface hydrosphere is fomed by: - s o i l water, occurring i n the upper 2-4 m layer on the boundary of the atnosphere and the lithosphere. Water is r e t a i n e d i n s o i l by surface-tension forces, which a r e molecular ( e l e c t r i c a l ) by n a t u r e , i . e . o t h e r than those of gravity. The outflow of f r e e water from s o i l s occurs only i f the pressure i n the s o i l water exceeds the atmospheric pressure. S o i l water i s , therefore, uns u i t a b l e f o r water e x t r a c t i o n , b u t indispensable f o r the photosynthesis of a l l plants.

-

groundwater i n t h e perineab1.e formations of t h e E a r t h ' s crust., retained especially by g r a v i t a t i o n a l forces and, t h e r e f o r e , usable f o r e x t r a c t i o n (Fig.

1.8). Perfieable geological formations a r e k n a a a s aqui.fers and water occurs i n t h e i r i n t e r n a l void space, forming ( a ) voids o r pores i . e . s u b t l e , microscopic spaces, which originated simultaneously with the a s s o c i a t e d rocks , (b) cracks , i . e . breaches and o t h e r g e n e r a l l y multi-directional spaces of secondary, t e c t o n i c o r i g i n , ( c ) c a v i t i e s , o r spaces of exceptional dimensions, o r i g i n a t i n g mainly i n cars t i c formations.

26 TABLE 1.5 FOm c

Prevailing forces

Occurrence

Flovenient

Water vapour

pressure

gaseous s t a t e

by pressure g r a d i e n t , wind power

I c e , snow

gravity

by ~ g r a v i t y ,i n s o i l a f t e r h e a t input by g r a v i t y and tidal f o r c e s , earth surface, p o r e s ? f r a c t u r e s , p r e s s u r e , o s m t i c acd tern perature madient camties

Gravi tat iona 1 g r a v i t y

s o l i d state

Capillary

surface tens ion

-

Adsorbed

attractive (surface potential)

hygroscopic viscous

overrdrying a t 105°C

Structural

rno l e c u l a r

crystal1 ic chemically combined biological

a f t e r disintegration/integration

biochemical

suspended held i n the interstices, supported available for plants no c o n t a c t with gravitational

a f t e r disintegration

Modes of water occurrence above and under the ground.

TABLE I .6 Types of i n t e r s t i c e s

fractures-cavities

Graphical i n t e r p r e t a t i o n

-

x zc

11-

Categorization of combined permeability according t o Landa (1980)

I

27 P a r t of the water i n f i l t r a t e d i n t o the s o i l flows l a t e r a l l y a t shallow depths as interflow owing t o less pervious lenses below the s o i l surface.

Fig. 1.8. Schenatic r e p r e s e n t a t i o n of a c h a r a c t e r i s t i c arrangement of groundwater s t r a t a . (1) 1st (unconfined) aquifer, ( 2 ) depends on geographical length and geological s t r u c t u r e . The s i z e of c i r c l e s i s proportional t o the pressure (potential). Voids, cracks and c a v i t i e s form extremely complicated underground spaces, which a r e separated o r interconnected and which comnunicate e f f e c t i v e l y o r none f f e c t i v e l y . Water i n these i n t e r n a l spaces, whose permeability is combined (Tab, 1,6), i s influenced by

28

- acting a s

(a) gravity - acting as the water weight, surrounding geological f o m t i o n s ,

the pressure of

(b)

pressure of gases emitted by the water

( c)

surface-tension forces ( c a p i l l a r i t y ) molecular forces of the s o i l or rock p a r t i c l e s (hygrosc0pi.c forces e t c . ,

(d) primarily e l e c t r i c a l in nature) (e) osmotic forces, caused by the different qualilry (chemical composition) of water i n different parts of the geological. formations. Unless these forces are i.n a s t a t e of equilibrium, groundwater is in movement and a l s o influenced by ( f ) f r i c t i o n forces, caused by the roughness of the surface of the s o i l or rock p a r t i c l e s , (g) internal f r i c t i o n forces caused by the fluid viscosity. The flow in mutually comnunicating voids, cracks and cavities is i n d e t a i l non-unifoxm and unsteady. For practical purposes i t can be considered as uniform and steady on average. For groundwater movement Darcy's law i s applicable within the l.aminar range of flow where r e s i s t i v e forces govern flow and the s o i l /rock envirmment i s saturated Vf

(m.s-1 , m per day)

= g = k f . I

Q

- apparent velocity - flow r a t e

A

-

cross-sectional r a t e

I

=

dh ar; - hydraulic

kf

- coefficient

vf

(1.37) t

of f l o w

(m3 .s -1 , m3 per day)

gradient

of hydraulic conductivity (Tab. 3.6)

As velocity increases, i n e r t i a l forces change the linear relation to the apparent. velocity of flow a t the hydraulic gradient to the

1

L

vf=kf. I m m

- coefficient

-1

,m

per day)

(1.38)

(m.s -1 , m per day)

(l.39)

(m.s -+2

Similar equations can be derived for unsaturated flow

vf =

- Kf . g r a d y

grad?

ki

- gradient

- coefficient

of the t o t a l potential of the groundwater

of the unsaturated flow

(m.s-1 )

29 TABLE 1 . 6

Soil

C o e f f i c i e n t of hydraulic conduc-

Capillarity

t i v i t y k f (m.s-')

(nm)

Average poros i t y

2000

-

4000

50

-

95

5.10-6 -

700

-

1500

40

-

60

Compacted loamy sand

1 - 5.10-6

350

-

700

15

- 25

Fine and loose sand

1

5.10+

50

-

350

20

Coarse sand

1-

s.~o-~

10

50

25

Sandy gravel

2 . 1 0 - ~ - 1.10-~

-

- 45 - 35

20

-

1.

-

25

- 35

Clay

1.10-8

Silt

Clean gravel

-

40

Coefficients of hydraulic conductivity and average porosity and c a p i l l a r i t y of different soils. The t o t a l p o t e n t i a l of t h e groundwater i s the amount of energy needed t o

t r a n s f e r a u n i t of water q u a n t i t y from one place i n the system water-rock/soil I

to another one:

?'= t y k =y k . Fk

2 s-2 (J .kg-l = m )

. dl

.

-

t o t a l p o t e n t i a l of water i n tht. force f i e l d

(J.kg-')

Fk

-

u n i t force of t h e force f i e l d

(N. kg-l )

dl

-

distance

(1.&0)

O n the b a s i s of the d e f i n i t i o n s and formulas i n Tab. 1 . 7 , the t o t a l p o t e n t i a l

of groundwater under isothermic conditions is

Y'= g .

(x+z) +

1 d"'

(4P

-6 )

(J.kg-')

(1.41)

The groundwater mvement is s p a t i a l i n c h a r a c t e r . Depending on the governing p o t e n t i a l , the regime of flow can be

- where g r a v i t a t i o n a l and pneumatic forces a r e governing, - where t h e d i f f e r e n c e i n temperature is governing, hydrochemical - where osmotic forces a r e governing.

(a) hydrodynamic

(b)

hydrothermal

(c) The hierarchy of these groundwater movement regimes is interconnected with

the values of the a s s o c i a t e d p o t e n t i a l s , which used t o be remarkably d i f f e r e n t . The regime of groundwater flow depends on t h e homogeneity of the geological formations. The r a t i o of permeability of the r e l e v a n t formations and t h e i r

30 i n t e g r a t e d p a r t s influences the c r e a t i o n of the flow regime. Several regimes e . g . local, a r e a l and r e g i o n a l , can occur i n a heterogeneous environment (Fig. 1 . 9 ) . TABLE 1 . 7

Symbol

% rc

P'

Potential

Forces

Equation

gravita-

gravity

Y =g.dz

Explanatory notes =

g.z

g

-

z x

-

g

tional capillary

capillarity

Yc= g.x

pneurra t i c

pressure gradient of s o i l pases, atmospheric

qp=

k.3. d l

-_ -b' A P

=

gravitational constant head (m) c a p i l l a r y rise

r- u n i t weight

of

water

(kg.m -3) AP- pressure Eradient

(Pa = kg.rn-l.s-l)

yt

thermic

osmotic YO

wa tc?r dens i ty gradient d i f t erence i n chemical compos i t ion

Y

=

1 .AT

=

1r .J

t r

O

AT- tempera turc gradient

6- o s m t i c pressure (Pa)

Categpol-ization of' s o i i water p o t e n t i a l . The function of d i f f e r e n t forces i n the heterogeneous system of hydrogeologic a l formations depends on e x t e r n a l f a c t o r s , incluaing

-

c l i m t i c and meteorological f a c t o r s ,

-

\ r , r k t i o n s and o s c i l l a t i o n s i n the interconnected surface water levels of

s u r f a c e rim-off,

water courses, r e s e r v o i r s , lakes and s e a s , e x t e r n a l load. Where the s u r f a c e water is not i n contact with an unconfined a q u i f e r , the

-

p r e c i p i t a t i o n produces the gwerning iafluence. Seasonal v a r i a t i o n s i n r a i n f a l l and changes of groundwater i n s t o r a g e , m n i f e s t a t e d by changes i n groundwater t a b l e s , a r e c l o s e l y c o r r e l a t e d . This c o r r e l a t i o n is heavily influenced by the surface run-off:

the groundwater recharge depends on the r a i n f a l l i n t e n s i t y and

d i s t r i b u t i o n . The same monthly averages may produce d i f f e r e n t f l u c t u a t i o n s i n the water t a b l e .

31

0 -15

n - , 0

0.45

0.25

0.35

0.45

a.

0.55 0.65 t.

0.75

0.85

0.95

Fig. 1.9. Regional flow of groundwater (flow d i r e c t i o n marked f u l l y , equipotent i a l s dashed, system boundaries dash- and d o t t e d ) : a - hcmegeneous permeable s t r a t a according t o llubbert (1940), b - homogeneous i s o t r o p i c s t r a t a according to Toth (1962), c - heterogeneous s t r a t a according t o Freeze, Witherspoon (1966): local regimen dotted densely, intermediate medium, regional regimen dotted scarcely.

b. 5

h m (mm)

0.4

0.3

0.2 0.1 n

4920

1900

1940

1st WEEK

2nd WEEK

3rd WEEK

4thWEEK

Fig. 1.10. Reduction of values and t i m e delay of groundwater f l u c t u a t i o n i n rel a t i o n t o the r a i n f a l l occurrence ( d e v i a t i o n from the average) according t o Todd (1970). Relationship of the a i r pressure and the water t a b l e f l u c t u a t i o n i n an a r t e s i a n well according t o Robinson (1939). Atmospheric pressure has no e f f e c t on unconfined a q u i f e r s . I n the case of confined a q u i f e r s , increases i n atmospheric pressure cause a decrease i n water tables and v i c e versa (Fig. 1.10): Ah =

?.Apa

(m)

Apa

- change

i n atmospheric pressure

Ah

- water

level decrease or increase

(m of water)

(1.42)

32 1.3.7

Flow i n Channel Network

Overland flow i s eradiial~lvconcentrated by t h e topography o f t h e E a r t h ' s

siir

f a c e . Flow i n n a t u r a l channels whose p r o f i l e and head i s n o t s t a b l e due t o erosion and s i l t a t i o n is g e n e r a l l y non-uniform and tinsteady. The discharge and the medium averape v e l o c i t y a r e fimctions o f t i m e and space. The discharge i n n a t u r a l channels can f o r p r a c t i c a l . piirposes be considered a s gradually v a r i e d . In t h i s c a s e , the t o t a l head Ah a t n channel s e c t i o n can be expressed a s Ah

v:

.

I,

=

.

2 2 (v, - v l )

n

-+

= v1

k (1.43)

R v

.

2g

Rf +

"2

=

2

"2g.

Ah+k(vy

-

v;)]~

(m.s-')

& - t o t a l head a t a channel s e c t i o n

(m)

v I , v2 - mean v e l o c i t y i n t h e upper and lower p r o f i l e

T2 - length of t h e channel s e c t i o n

R - hydraulic r a d i u s ( A

(1.44)

m . n

=

A

-0

)

(m.s-l)

(m) (m)

- a r e a of t h e c r o s s s e c t i o n

(m2)

0 - wetted perimeter

(mi

k

-

n

- c o e f f i c i e n t of channel roughness ( s m o t h 0 , 0 1 , v a r i a b l e s e c t i o n s 0,05)

reduction c o e f f i c i e n t (

1 )

Under conditions o f a s t a b l e p r o f i l e , uniform s l o p e and roughness i n a channel without b a r r i e r s , t h e equation (1.43) can be s i m p l i f i e d a s follows v s = -n1.

I

R4

(m.2-l)

(1.45)

Ah - s l o p e of t h e channel

= -T;

The roughness c o e f f i c i e n t depends on geomorphological condi tioris: t h e riverbpd m t e r i a l , t h e unevenness of i t s s u r f a c e , t h e c h a r a c t e r of the p r o f i l e changes, t h e b a r r i e r s i n t h e r i v e r b e d , t h e r i v e r s i d e vegetatior., t h e meandering and sediment t r a n s p o r t (Tab. 1.8). The total roughness c o e f f i c i e n t can be a s s e s s e d on t h e b a s i s of t h e sripp1e~ientedforrrmla of Cowan (1957) n = m . s .

4

k=l "k

(1.46)

33 TABIE 1.8

Coefficient of

characteristics

Value

Coefficient of

Characteristics

Value

earth rock f i n e gravel coarse gravel

0,020

n4

"1 rmterial roughness

negligible small medium high

0,000-0,010 0,010-0,015 0,020-0,030 0,040-0,060

smooth, p l a i n smi11 r i p p l e s medium r i p p l e s dunes

0,000 0,005

lOW

"2 bed roiighnes s

0,005-0,010 0,010-0,02 5 0,025 ,0,050 0,050,0,100

"3 cross section changes

barriers

gentle o c c , ~iorlal s frequent

:):it

n5 vegetation canopy

0,WO

m

high medium

high and dense

mpandering

laJ medium high

1,000 1,150 1,300

low high muddy discharge

1.000 1 500

-0,015

S

sediment transport

; 2 -

100

P a r t i a l c o e f f i c i e n t f o r estimation of the roughness c o e f f i c i e n t f o r various boundaries according t o Cowan (1957) supplemented by t h e c o e f f i c i e n t of the sediment t r a n s p o r t impact. 1.4

INTERREIATIONS OF SLJRFACF WATER AND GROllNJWATER RLTNOFF

Runoff is a hydrologic process of r a i n f a l l d i s t r i b u t i o n by the E a r t h ' s sinface, which takes place i n thc system of the l i t h o - and hydrosphere. This system c o n s i s t s of n a t u r a l (m~r?tiological, geological, s o i l , vegetative) and anthropogenetic elements (urban, r u r a l and o t h e r c o n s t r u c t i o n s , dykes, r e s e r v o i r s , drainage and sewerage networks e t c . ) . The output of t h i s system depends on the input, which i s characterized by ( a ) meteorological data, e s p e c i a l l y r a i n f a l l d i s t r i b u t i o n ( b ) climatological data, or t h e supply of s o l a r energy, and on the a c t u a l s t a t e of t h i s s y s t e n , which depends on i t s previous function (degree of s a t u r a t i o n ) and anthropogenetic f a c t o r s (water management a c t i v i t i e s ) . Under n a t u r a l undisturbed condj t i o n s , the s u r f a c e outflow can be characterized by meteorological and cl irratological f a c t o r s (Tab. 1.9). Surface runoff equals p r e c i p i t a t i o n minus i n t e r c e p t i o n , depression and detention s t o r a g e , changing i n t o i n f i l t r a t i o n and evaporation. The r a t i o of the sur-

34 TABLE 1 . 9

Category

Area ( c l i m t e f

Sub-category

C h a r a c t e r i s t i c s of discharge occurrence

1.

discharges only i n r a i n f a l l periods

2.

high 6 is charges i n w i n t e r , extremely law i n suniner

t r o p i c a l and subtropical

3.

high discharges during sunmer

humid

4.

high discharges o u t of the sulmer season

cool humid

1.

peak discharges e s p e c i a l l y i n s p r i n g , influenced by r a i n f a l l

Rivers whose f l m depends

hilly, nor t h e m

2.

high discharpes influenced by r a i r fall

mainly on snowmelt and

high mountains

3.

high discharges from snowmelt i n smer

g l a c i e r runoff

pemfros

4.

temporary s treans downstream of glaciers

a r i d and semiarid

A. Rivers whose depends mainly on r a i n f a 11

B.

Categorization of r i v e r s according to meteorological and climatological f a c t o r s . I

TABLE 1.10 Type of a r e a

Slope f l a t 'average 1% 1-5%

Residential

closed blocks paved courts

Apparment dwe 11i n g

closed blocks with yards open blocks detached m l t i - u n i t s

0.70 0.60 0.50

steep

5% 0.90

0.40

0.80 0.70 0.60 0.50 0.40 0.30

0.50 0.40

0.90 0.50

-

Single-family houses with gardens

attached detached

0.30 0.20

Industrial

o l d type densely covered modern wi.th laws

0.60 0.40

0.80 0.70 0.60

~~

0.30 0.80 0.95 Railway a r e a s 0.30 0.40 Unimproved a r e a s 0.20 0.30 Grassland, f i e l d s sandy s o i l 0.05 0.10 0.15 0.17 0.22 0.35 heavy s o i l Forests 0.00 0.05 0.10 Values of runoff c o e f f i c i e n t i n r e l a t i o n t o the type of the drainage a r e a . Parks, cemeteries, playgrounds S t r e e t s , d r i v e s , walks , roofs

0.10 0.70 G.20 0.10

0.20

35 face runoff and t o t a l l o s s i s (recharge and evaporation) does n o t change when the s t a t e of t h e elements and t h e energy supply i n t o t h e system remains c onsta nt. For p r a c t i c a l reasons t h i s r a t i o i s considered a s s t a b l e even i n the case of a

s i n g l e r a i n f a l l . Such hypothesis leads t o the lollowing sim plifie d equations f o r each of the elements Q . = P . s1 g1

j:

- (I.1 + D.) = P. 1 1

(Kai

+ Ei)

(3

(1.47)

(1.48) and f o r the t o t a l a r e a n 5 c;

. Pi . Ai

Qs

=

1000.

Qs

-

s u r f a c e outflcw

(1.49)

(m3)

G - groundwa t e r / s o i l recharge

(m3 )

Pi - p r e c i p i t a t i o n i n element i

(m)

a

Ci

-

Ai

- area

runnoff c o e f f i c i e n t of element of e l eiaent

(IJ,

This s i m p l i f i c a t i o n n eg l ect s the time d i s t r i b u t i o n of tlle input data and the changing state of t h e runoff system. The a c t u a l runoff c o e f f i c i e n t is not s t a b l e . i t is not only a f u n ct i o n of t h e drainage a r e a roughness r (which chaiiges e . g . with t h e s e a s o n ) , i t s shape and s l o p e i , geology g but also a function of the soil state

Factors r , i , and g a r e r e l a t i v e l y s t a b l e and a r e almost independent of m e t e o r o l o g i a l conditions. r a c t o r sf depends on f r o s t an6 s a t u r a t i o n of s o i l . I t determines the a c t u a l runoff j n t h e s p e c i f i c hydrologic s i t u a t i o n . The t o t a l annual runoff can be determined on the b a s i s of the c lim a toloa ic a l input d a t a . Data en the l e f t s i d e of t h e s i m p l i f i e d equation o i the hydrologic balance i . e . p r e c i p i t a t i o n P and s u r f ace runoff Q

= G + E

P-Q

S

P

(m,m3 per ye a r)

(1.51)

can be measured q u i t e e a s i l y and p r e c i s e l y . They a r e i n mst cases measured i n the long term and s y s t e m a t i c a l l y , and a l s o analyzed statist.ically. Data on evaporation E and groundwater recharge G on the r i g h t sj.de of the equation, a r e 8’ d i f f i c u l t t o m a s u r e and, t h er ef o r e, n o t syste m a tic a lly f o l l m e d up. Groundwater recharge and evaporation can be expressed as a function of the l e f t s i d e o t the

36

equation 1.51 E = f l

(P-C,)

c, = f 2 ( P - 9s ) R

3

)

(1.52)

3 ( m v )

(1.53)

(m,ni

The maximum p o s s i b l e evaporation f o r the measured long-term d i f f e r e n c e of rainf a l l and the s u r f a c e runoff is

Em

3 (m,n )

=P-Qs

(1.54)

I n t h i s case G = 0, the groundwater i s without recharge. g

This phenomenon occurs i n d e s e r t catchment a r e a s , where a l l the i n f i l t r a t e d water evaporates. This can be graphically i l l u s t r a t e d by a s t r a i g h t l i n e with an angle of 4 5 ' (Fig. 1. 11).

E (mm)

I-

/

/

.-----

I

r -

P-Qs

(mm)

Fig. 1.11. Regional c h a r a c t e r i s t i c s of the runoff: E - evaporation, E T 1 - evapor a t i v i t y , P - r a i n f a l l t o t a l , G - groundwater recharge, os - s u r f a c e water runF: off. The second limiting- s t a g e could t h e o r e t i c a l l y be reached when the d i f f e r e n c e

of r a i n f a l l and s u r f a c e runoif recharges t h e groundwater without any ebaporation. This case is g r a p h i c a l l y illustra.ced by the h o r i z o n t a l a x i s . The p r a c t i c a l values of t h e function f l migrate between these two Limiting s t a g e s . They a r e a l s o l i m i t e d by t h e n1value of p o t e n t i a l evaporation corresponding t o the supply of s o l a r energy i n the a r e a . Curves f 1 and f ,2 express t h e average influence of the i n p u t data of the relevant runoff system and can, therefore, be used a s regional c h a r a c t e r i s t i c s f o r the assessment of the

groundwater runoff and evapo-

ration. The system of the r a i n f a l l / r u n o f f process can be modelled on a physical o r mathematical b a s i s . The b a s i s of the mathematical Tank blade1 assembled by

SWAWARA (1974) is hydraulic. This model represents the catchment area by a set

37 of tanks, arranged v e r t i c a l l y i a a row. The number of tanks, t h e i r grouping and conf iguratTon deperta

01: the

ca tclmeiit c h a r a c t e r i s t i c s . Experience shows t h a t

the following two b a s i c systems a r e s u i t a b l e f o r any p r a c t i c a l case (a) (b) areas.

four tanks arranged v e r t i c a l l y f o r humid a r e a s , s e v e r a l rows of four tanks arranged v e r t i c a l l y f o r semi-arid and a r i d

Fig. 1 . 1 2 . Separation of the runoff components, its course and physical principles of the mtheniatical m d e l of t h e runoff process according t o SUGAWAHA (1974): ql - s u r f a c e r u n o f f , % ground s u r f a c e , 93 - intermediate outflow groundwater runoff with short-term and q (above the groundwater t a b l e ) , with long-term delay before p e n 3 r a t i o n i n t o t h e r i v e r , 21 infiltration, 22,23 - p e r c o l a t i o n i n t o groundwater, 24 deep p e r c o l a t i o n . Water tables: hi a t low, h, - a t medim, h 3 - a t high r a i n f a l l .

-

-

-

.

Tanks a r e equipped with s i d e

-

o u t l e t s and bottom o u t l e t s . The outflow from

the s i d e o u t l e t s simulates t h e following components of t h e surface runoff (Fig. 1.12):

-

the top tank the s u r f a c e and ground s u r f a c e r u n o f f , reaching the channel i n

one t o t h r e e days,

-

the second tank the intermediate r u n o f f , reaching the channel i n a week's time.

- the t h i r d and f o u r t h tank t h e groundwater runoff, reaching t h e channel i n one month, o r i n a y e a r ' s time. The top tank generally has two s i d e o u t l e t s , while the o t h e r tanks a r e equipped w i t h one s i d e o u t l e t only. The bottom out1et:s of a l l tanks simulate the i n f i l t r a t i o n o r , i n the case of the f o u r t h tank, the deep percolation. The outf l m from o u t l e t s is simply e w r e s s e d by a l i n e a r o r square r e l a t i o n on the

38 storage amount :

qk

=ak. Xk

qk

-

outflow from the o u t l e t

Xlc

-

s t o r a g e :imunt

4( -

(1.55)

= f,(t)

outlet coefficient

The following simple square r e l a t i o n i s used whenever t h e l i n e a r r e l a t i o n does not generate s a t i s f a c t o r y r e s u l t s : qli =Nk

. Xk2

(m3.s-1)

= "-?+IT

- period

t

of progression

L

-

kf

- coefficient

h

- head

ne

(days)

effective porosity

(%)

s h o r t e s t d i s t a n c e from t h e stream channel (m)

Relationship

of hydraulic co n d u ct i v ity

(m pe r day) (m)

I

Disconnected

1

Mutual

1

Mixed

1

Complicated

Sc he m o t ~c representation (cross section)

hydrogroph

Impact o n

Groundwater o n

depends on the head

depends on the heo

Fig. 1.15. I n t e r r e l a t i o n s h i p s of r u n o f f , water t a b l e s and q u a l i t y of the groundwater. Water t a b l e s : 1 - water course, 2 - independent a q u i f e r , 3 - a q u i f e r dependent on the stream, 4 - confined a q u i f e r ,

The d i r e c t i o n of t h e flow between the s u r f a c e and the groundwater influences the water q u a l i t y : i n t r u d i n g water changes t h e water q u a l i t y of the e f f l u e n t . Both processes, and e s p e c i a l l y i n f i l t r a t i o n , the process of s u r f a c e water penet r a t i o n i n t o the groundwater can be slowed d m by clogging, i . e . the blocking of pores and cracks by suspended matter. During drainage, a re ve rse process occurs, s u f f u s i o n , which g r ad u al l y speeds up the groundwater movement. S o i l moisture, which is of b a s i c importance f o r the water supply of p l a n t s , is less supplemented by groundwater than by p r e c i p i t a t i o n . G ra vita tiona l potent i a l is less important f o r i t s e x p l o i t a t i o n by p l a n t s than the c a p i l l a r y and

42 osmotic f o r c e s , whose function can be measured a s the t o t a l s o i l suction. This t o t a l s o i l s u c t i o n c o n s i s t s of the matric s u c t i o n , numerically equal to the c a p i l l a r y pressure, and the s o l u t e s u c t i o n , numerically equal t o the osmotic pressure. These depend on the s o i l t e x t u r e and s t r u c t u r e , on the interconnection of pores and cracks, on the chemical p r o p e r t i e s and temperature of t h e s o i l and water, but e s p e c i a l l y on the moisture content expressed by the r a t i o w =

- . 100 "W

(7:)

(1.59)

VO

w V

W

V,

- moisture -

content (volumetric)

3 t o t a l volume of water i n pores and voids (m ) t o t a l volume of the rock o r s o i l

<m3)

The r e l a t i o n s h i p of the moisture content and the t o t a l s o i l s u c t i o n has t o be expressed using the n a t u r a l logarithm pF = In of the t o t a l s o i l s u c t i o n = 3 + 981 Pa (m of water)

(1.60)

(Tab. 1.11) TABLE 1.11

Hydrolimits

Full capacity (saturated)

Suction pressure PF

0

Moisture content % 25-60

Definition

I

S t a t e i n which pores and cracks a r e f i l l e d up with g r a v i t a t i o n a l and o t h e r water. Corresponds to the c a p i l l a r y porosity

.

Field capacity FC

2.5-3.0

10-40

S t a t e i n which water is held i n the s o i l a f t e r the g r a v i t a t i o n a l water has drained away.

Point of decreased availability

3.1-3.5

4-35

S t a t e i n which the c a p i l l a r y conductivity was i n t e r r u p t e d .

4.18

2-30

S t a t e i n which evapotranspiration exceeds the water i n p u t (depends a l s o on the p l a n t species).

4.8-5.2

1-15

S t a t e i n which the s o i l does not contain e i t h e r g r a v i t a t i o n a l o r c a p i l l a r y water.

Wilting point wp Adsorption water capacity

Categorization of s o i l state according t o its s u c t i o n pressure and moisture ret e n t i o n from p l a n t c u l t i v a t i o n . The changing s o i l moisture and t h e t o t a l s u c t i o n pressure form c h a r a c t e r i s t i c s i n t e r v a l s . On the boundaries of these i n t e r v a l s t h e water supply of the p l a n t s

43 changes i n a way which q u a l i t a t i v e l y influences the develop,nent of the p l a n t s . The c e n t r e of t h e j e i n t e r v a l s has a c h a r a c t e r i s t i c value of the t o t a l s o i l suc-

t i o n and moisture, depending on t h e s o i l category (Fig. 1.16).

Fig. 1.16. I n t e r r e l a t i o n s of t h e s o i l p o r o s i t y and humidity with the s u c t i o n pressure, p o t e n t i a l and s o i l moisture r e t e n t i o n data according t o Kutilek

(1979). The water regime of s o i l s depends on

-

s o i l category, i t s t e x t u r e , s t r u c t u r e and permeability, c h a r a c t e r i z e d by the

c o e f f i c i e n t of the h y d r a u l i c c o n d u c t i v i t y , o r by the course of the t o t a l s o i l suction, - the p o s i t i o n of the s o i l p r o f i l e w i t h regard t o the groundwater l e v e l and the reach of the c a p i l l a r y zone, - the rcot system of t h e p l a n t s ,

-

anthropogenetic f a c t o r s , i n c l u d i n g e s p e c i a l l y changes i n the s o i l t e x t u r e ,

s t r u c t u r e and moisture during i t s e x p l o i t a t i o n ,

-

climatological characteris t i c s . Rode (1556) c l a s s i f i e s the water regime of s o i l s on t h e b a s i s of the annual

r a t i o of t h e r a i n f a l l and e v a p o t r a n s p i r a t i o n (Tab. 1.12). I t i s u s e f u l to add the swampy regime to t h i s c l a s s i f i c a t i o n , which occurs when t h e water level permanently p e n e t r a t e s above t h e

s o i l s u r f a c e . 'Ihe gradual development of s o i l i s

i n t e r r e l a t e d w i t h t h e water regime and t h e a c t i o n of c l i m a t o l o g i c a l € a c t o r s (Tab. 1.13).

44

TABLE 1.12 Regime

Characteristics

1. Permafrost

The s o i l water is p e m n e n t l y frozen

>1

2 . Flushing

The s o i l is completely wetted s e v e r a l times a year

>1

Ratio of annual precipitation and evaporation total

3. I n t e r m i t t e n t S o i l is not flushed every year

tl

4 . Unflushed

I n f i l t r a t i o n does not recharge groundwater r e s e r v e s , the s o i l p r o f i l e being only p a r t i a l l y wetted

(1

5. Evaporative

S o i l p r o f i l e moisture is supplemented from groundwater

6. I r r i g a t i o n

S o i l r e g u l a r l y wetted by i r r i g a t i o n

A,K

-

s

-

constants the volume of suspended particles intercepted by the u n i t volume of the layer

The volume of intercepted p a r t i c l e s

;

- - - -vf

.

+

(1.79)

vf - apparent velocity of the groundwater flow (m per day) The above-mentioned physical and chemical processes usually determine the quality of

MtUrd

waters i n the underground:

on the Earth’s surface and above

it. These processes are often accompanied by biological, o r bacteriological processes. These usually depend not only on the thermal energy input or output, but a l s o on luminous energy.

67 F r m the biological point of view, the complex of local physical, chemical and other conditions i s named biotope. The development of a biocoenosis, a comnunity of organism, depends on t h i s biotope. Each type of biotope contains not only c h a r a c t e r i s t i c organisms, but a l s o organisms which a r e usual i n other biotopes and which have been brought i n by chance. The resulting water quality can be c l a s s i f i e d (a)

formally

(b)

genetically i n accordance with the p o s s i b i l i t i e s of i t s u t i l i z a t i o n ,

(c)

(d) i n accordance with i t s influence on biological factors. Systematic categorization, enabling an e x p l i c i t genetic c l a s s i f i c a t i o n on the basis of formal Thysical and chemical factors, has not y e t been developed. Different c l a s s i f i c a t i o n s a r e , therefore, used for the c l a s s i f i c a t i o n of surface waters and groundwa t e r s

.

Groundwater can, i n accordance with its chemical composition, be c l a s s i f i e d as

(a) plain - containing l e s s than 1 g of dissolved substances i n 1 l i t e r , (b) brackish - containing 1 t o 30 g of dissolved substances i n 1 l i t e r , (c) brine - containing more than 30 g of dissolved substances i n 1 l i t e r of water . Waters which contain m r e than 1 g of carbon dioxide CO2 i n 1 l i t e r a r e denoted as acidic. Natural mineral waters contain e i t h e r more than 1 g of dissolved substances o r of carbon dioxide. Waters whose healing properties have been s c i e n t i f i c a l l y proved m y be described as medicinal, o r curative. The c l a s s i f i cation and terminology of mineral waters can be derived from p a r t i a l c l a s s i f i cation according t o the content of dissolved gases, quantity of dissolved s o l i d s , main ion components, biologically and pharmaceutically important components, chemical reaction, radioactivity , osmotic pressure and temperature. T h e m 1 waters whose temperature generally exceeds 25OC can be c l a s s i f i e d as

- hypo t h e m 1

25-35OC

-

35-42OC

-

isotherm1 hyper t h e m 1

> 42OC. The c l a s s i f i c a t i o n of groundwaters on the basis of t h e i r chemical composition

is governed e i t h e r by the prevailing ions o r by the prevailing ion combinations. J e t e l (1975) connects both these principles i n the following way and differentiates: - classes S, C , N, C 1

-

-

accordinE t o the representative anion SO4, H a 3 , N, C1,

groups according t o the representative cation Na, K , M g , Ca.

Contents ( r ) of other ions a re t o be added t o the similar main ions: Mn" Fe2+ to Ca2+, NO t o C l - and alkalines t o Na', cO$- to HW;. 3

and

68

-

s p e c i e s according t o combinations of t h e m i n i o n s , m r k e d by Rown f i g u r e s

(Tab. 1.23). The symbol of groundwater q u a l i t y forms marks of the main a n i o n s , c a t i o n s , s p e c i e s and t h e value of t h e t o t a l m i n e r a l i z a t i o n , e . g . CINa - 0,014 g.1-'. i1

TABLE 1 . 2 3 Index 1

Hypothetical combinations of ions NaCl

Na2S04

Characteristic r e l a tionship

NaHW3

rHCQ3>

Mg(HC03)2

rNA

>

r(Ca+Mp) r(C1+S04)

(HCO3)2

I1

NaCl Na2s:4 MWq

Mg (Hm3 12 Ca(HC03)2

rHC03

rNa

>

MgS04

CaS04 IIIb

>

r(HC03+S04) i.e. r(Na+Mg)

MgS04 &SO4

H2S04 NaC 1 MgCl

rHm3

= 0

MgS04 Caso4

H2S04 NaCl

caso4

MgC12 CaCl2 Groundwater c a t e g o r i z a t i o n depending on ion c m b i n a tions according to Alekin (1970). I V . s p e c i e s c a t e g o r i z e d according t o F l o r e a (1970).

69 The q m l j t y o f s u r f a c e waters depends t o a g r e a t e x t e n t on h y d r o l o g i c a l , meteorological and antropogenetic f a c t o r s and changes considerably w i t h time. The chemical composition of these water i s n o t the p r e v a i l i n g agent of t h e i r quality . Their m i n e r a l i z a t i o n i s remarkably lower than t h a t of groundwaters. The q u a l i t y of siirface w a t e r , t h e r e f o r e , is t o be defined on the b a s i s of f u r t h e r c h a r a c t e r i s t i c i n d i c a t o r s : oxypen regime, microbiological and o t h e r i n d i c a t o r s (Tab. 1.24) and a l s o w i t h regard t o i t s p o s s i b l e u t i l i z a t i o n . Oxygen demnd i s the a b i l i t y of substances t o u t i l i z e t h e d i s s o l v e d oxygen f o r t h e i r s t a b i l i z a t i o n . Chemical oxygen denland (COD) i s a measure (mg 02, 1-l) of the m a t e r i a l s p r e s e n t i n water which may be r e a d i l y oxidized, i n order t o a s c e r t a i n the amount of o r g a n i c and reducing m a t e r i a l . Biochemical oxygen demand (BOD) i s t h e amount of oxygen used by a q u a t i c microorganisms i n t h e i r metabolic processes. The e v a l u a t i o n of t h e

ROD r a t i o o f f e r s the b a s i c informa-

t i o n concerning the c o n t e n t of b i o l o g i c a l l y degradable and r e s i s t a n t constituen ts . The amount o f d i s s o l v e d oxygen (mg.1-')

depends on t h e water q u a l i t y . The

d i f f e r e n c e between the maximum p o s s i b l e concentration of oxygen (depending on temperature - Tab. 1.24) and the a c t u a l c o n c e n t r a t i o n is termed oxygen d e f i c i t . Their r a t i o is marked a s s a t u r a t i o n r a t i o . Very important i n d i c a t o r s of t h e b a s i c chemical compositipn include the value o f t o t a l d i s s o l v e d s o l i d s TDS (mg.1-')

and t h e value of suspended r a t t e r :

The c o n c e n t r a t i o n of ions i s p r e s e n t l y followed i n m u l t i p l e s of the content of

rmtter i n a system, whose number of molecules is equal to the number of atoms i n 12.10%g Na+

of carbon i s o t o p e I2C a t 1 l i t e r ( m l . l - ' ) .

, Ma2+ are

, SO:-,

The ions C1-

followed i n p a r t i c u l a r .

C o n s t i t u e n t s which may s i g n i f i c a n t l y a f f e c t the a p p l i c a t i o n of water f o r b e n e f i c i a l purposes include c a t i o n s , namely sodium Na+, potassium K+ and Mn+

,

calcium Ca+ and magnesium Mp'

a m o n i a NH4; hydroxide OH

c h l o r i d e C1-

, are

, and

, further

,

i r o n Fe+

,

a n i o n s , namely n i t r a t e NO; and

a l s o bicarbonates HCO-

3

, carbonate

CO- and

3

g e n e r a l l y considered i n t h e l i g h t of t h e i r i n f l u e n c e on a l -

k a l i n i t y and hardness. Nonionic c o n s t i t u e n t s include e s p e c i a l l y d e t e r g e n t s , o i l y substances, phenols, cyanides and s i l i c a ( s i l i c o n dioxide Si02). The sum of t h e c a l c i i m and magnesium, expressed as a n e q u i v a l e n t amount of calcium carbonate, was i n the p a s t followed a s water hardness and is p r e s e n t l y replaced by a s e p a r a t e following up of both these c a t i o n s . An important i n t e g r a t e d property of water i s t h e hydrogen-ion concentration pH, the n e g a t i v e logarithm t o t h e b a s e 10 of t h e hydrogen-ion concentration. A balance between d i s s o c i a t e d hydrogen and hydroxyl ions denotes a pH value of

7.0, b u t t h i s value has no special s i p i f i c a n c e as a n expression of a l k a l i n i t y and a c i d i t y .

70 TABLE 1.24

Class

Ia

Characteris t i c s

very clean

a ) Indicators of the oxygen repime -1 Dissolved oxygen mg.1 -1 mg. 1 mD5 Oxidizability by mg.1 permangana t e Saprobi ty

Ib

I1 clean s l i g h t l y polluted

>o

>7 (2

5 25

> 0.

(1.82)

After t h i s i n i t i a l phase, the value of t h e b i o m s s increment decreases t o the value of the b i o l o g i c a l balance, characterized by = -o

dt

.

(1.83)

R e water q u a l i t y with regard t o i t s b i o l o g i c a l p r o p e r t i e s can be c l a s s i f i e d i n terms of i t s saprobity o r t r o p h i c i t y . The saprobity is the biological s t a t e of water, determined on the b a s i s of the presence o r absence of biocoenosis, t h a t i s c h a r a c t e r i s t i c f o r a c e r t a i n degree of biochemical decay, i . e . i n relation to the degree of p o l l u t i o n (Tab. 1.30). The saprobity c h a r a c t e r i z e s the changing p r o p e r t i e s of the water environment during a c e r t a i n period, thus d i f f e r i n g from the physical and chemical indicat o r s , which c h a r a c t e r i z e the a c t u a l s t a t e only. For t h i s reason, an e x p l i c i t r e l a t i o n between the s a p r o b i t y and r e l e v a n t physical and chemical i n d i c a t o r s does n o t e x i s t , though the c l a s s i f i c a t i o n sys t e m of saprobity is closely i n t e r r e l a t e d with the b i o l o g i c a l oxygen demand (BOD) of water (Fig. 1.28). The t r o p h i c i t y is the a b i l i t y of water to nourish water organisms. Nauman (1932) c l a s s i f i e d the t r o p h i c i t y on the b a s i s of the s u r p l u s , average o r undersized values of the b a s i c physical and chemical preconditions of the development of d i f f e r e n t biocoenosis. Seven b a s i c trophical types of stagnant and flowing waters follow a s a consequence of combining these c r i t e r i a (Tab. 1.31).

Some changes and combinations a r e chemically impossible, such a s a l k a l i t r o p h i c i t y with s i d e r o t r o p h i c i t y , a c i d o t r o p h i c i t y and d y s t r o p h i c i t y , o r acidotrop h i c i t y with e u t r o p h i c i t y . A p r a c t i c a l c l a s s i f i c a t i o n is based on t h e mean annual values. The views on t h e i n t e r r e l a t i o n s h i p of the saprobity and the t r o p h i c i t y have not y e t been u n i f i e d . Kolkwitz (1935), SlAdeCek (1961) and o t h e r s state t h a t the eutrophization and s e l f - p u r i f i c a t i o n processes are only two d i r e c t i o n s of one n a t u r a l process, r e l a t i n g i n t h i s way the denee of saprobity with the degree of t r o p h i c i t y . The scale of t r o p h i c i t y i s then the r a t i o of the production of l i v i n g nlatter to r e s p i r a t i o n , l i b e r a t i n g the organic energy, bonded by l i v i n g matter.

80

Fig. 1.28. C i r c u l a r r e p r e s e n t a t i o n of water q u a l i t y by degree of s a p r o b i t y and r e l e v a n t s tructrire of a q u a t i c ecosystems according t o Sl5deCek (1972): Linmosaprobity: (x-xeno, 0-oligo, B-brtamezo, d-alphameso, p-polysaprobitv), Eusaprobity ( i - i s o , m-meta, h-hyper, u - u l t r a s a p r o b i t y ) , Transaprobity (a-anti , r-radio, k-kryptosaprobity). Detrivore marked black: R-bacteria. Consiunersherbi-, carni-and omnivore niarked d o t t e d : Z-zooplankton, C - c i l i a t a , F-zooflag e l l a t a . Producers- Ereen p l a n t s and a u t o t r o p h i c b a c t e r i a m r k e d white: Pphytoplankton, M-mixotrophic f l a g e l l a t a . O-no l i f e . Arrows show the d i r e c t i o r i of e u t r o p h i z a t i o n (1) and f u r t h e r p o l l u t i o n (Z), decay and s e l f - p u r i f i c a t i o n ( 3 ) . Dsahed segment r e p r e s e n t s the i n c r e a s e i n m a t e r i a l i n p u t and output (and a l s o the i n c r e a s e i n t h e b i o l o g i c a l oxygen demand).

TABLE 1.30 Process

Symbol Saprobi t y

o

ri

P

Degree of saprobity

Pollution (degree)

BOD5 Plankton (in

5

mg.1-'

m

m1-I)

Primary production -3 3 . -3 (w.m ( R . m (mg.m ) .d-]) .yeard1

$

3 abiotic

29

L Limosaprobi ty

2 3

no l i f e completed .rl u oxyda t i o n .:completed greduction 0

a bstarting 33 . . z o x y d a t i o n d io . c 0

.," reduction 4-1

x

xenosaproblty

without pollution very l i g h t

';Ib i o l o g i c a l

54 2 J

3

m u

0 7

0

1

0

0

1

100

1

50

a

0 , 2 zatrophicity ultra-

10

ol i p t r o p h i c i t y o

fi

5

1o5

medium

10

lo6

5 100 30 (20) (1500) (5001 300 500 150 ( 1500) ( 12000) (40OO) 1000 1500 300-

heavy

50

lo7

10000

12000

4000

3

100

30

oligosaprobity l i g h t mesosaprobity

medium

d mesosaprobity p

i

polysaprobity isosaporbity

(ciliatic)

me tasaprobity

(hydrogen sulfidic)

hypersaprobity (bacteriologic) ultrasaprobity (abiotic) T Transsaprobity

a

0

2,5

1000

o l i g o t r o p h i c i ty

,L3 -eu t r o p h i c i t y

,d

! 2 . u predominant

E Eusaprobity

3 Trophici ty

2

i

C R

K Katarobity

U

Chlorophyle

Uchemical, u.d a b i o t i c ? anorganic, ffl a no l i f e

'G$2 .j 3

a

a n t i s a p r o b i ty

400 7 00 20G0

1000 0

+

+

M

t

' 4

rwt a t r o p h i c i t y

r

12 .lo4

toxic

radiosaprobity r a d i o a c t i v e k

kryp tosaprobi ty physical

Categorization of water q u a l i t y according to its saprobity and t r o p h i c i t y . Relationships of the metabolism, s e l f - p u r i f i c a t i o n processes and the t r o p h i c i t y . Values concerning chlorophyle and p r i m r y production a r e r e l a t e d t o the r e s u l t of the eutrophiza t i o n process.

2

82 TABLE 1.31 Physical and chemical i n d i c a t o r s

p~

Polytypus

Mesotypus

Oligotypus

15- 20 25-100 1- 0 1.5 25- 50

< 15 3- 25 0 0 25

-

N,P,Fe

S m e r temperature j u s t belaw the water t a b l e

> 20

OC

CaO

mg.1-1

Nitrogen

N

mg.1-I

Phosphorus

P

-1 mg. 1

Calcium oxide

>100 )40 >25 80-100

-1

mg. 1

Humus a c i d s Biotypus

Characteris t i c s Occurrence

a 1c a l i troph i c

poor plankton carst

PH )7

Ca

siderotrophic

l i m o n i t i c bed

Fe

a r g i l o trophic

high t u r b i d i t y loamy and s i l t sediments

humus mtter

eutrophic

high content of nutriments r i c h phytoplankton mud, m r s h e s bottom hydrogen sulphide c l e a r water, poor phytoplankton, poor f l o r a i n the neighbourhood new reservoirs, mountain lakes

01igo trophic

acido trophic

t u r f i c bed

dystrophic

browny water, poor phy to-plankton

>7

N,P

N,P

-7

< 5.5 3000

VI .

Classification of European waterways. and motor-driven tug. 'Itro categories can be distinguished on the basis of the biggest vessel (a)

European

(b)

Local

-

vessel E ( 82

.

vessel L ( 41

.

11.4 m ) 5.7 m )

The admissible draught on a canalized water course depends on the water stage: (m)

T = Hp - H d - M T

-

admissible draught of the vessel

(m)

H F: Hd

-

gauged water stage

(m)

M

- margin -

(2.30)

difference between the maximum draught and the gauged water stage (m) safety distance between the vessel bottom and the channel bottom

In the case of inland waterways with a fluctuating water table, the draught characteristic corresponds t o the draught secured during 240 days i n a hydrologically mean year. The network of inland waterways includes (a) (b)

r i v e r channels (natural, improved

-

trained, canalized)

canals ( a r t i f i c i a l water courses).

The basic parameters of these waterways, i.e. those which determine the carrying capacity, include the breadth and depth of the fairway, the corresponding minimum s i z e of the cross section, and the velocity of the flow. The other main dimensions determine the fluency, methods of operation, speed and safety of transport

.

The c r i t e r i a f o r a n assessment of the minimum dimensions a r e as follows (Fig. 2.4): (a) minimmn breadth of the fairway along s t r a i g h t stretches ( a t the level of bottom of the typical vessel): B = 2 b + 2 b'+ b"

(m)

(2.31)

105

Fig. 2 . 4 . Schematic cross section of an inland waterway. The relevant parameters are t o be derived from the parameters of the typical vessel. B

-

minimum breadth of the fairway

b

-

vessel width

b'

-

board space space between vessels

b"-

minimum breadth of the fairway i n a curved s t r e t c h

(b)

e

(2.32)

(m)

B ' = B + e

extension in curves n

L

- overall

length of the typical vessel formation

R - perimeter of the curve A

-

coefficient of the extension ( =

L* T

)

(m2)

(c) minimum depth of the fairway

T

- draught

M

- margin (d)

n P f

(2.33)

(m)

H = T + M

of the typical vessel safety distance between the vessel bottcxn and the channel bottom (0.3 0.5 m)

-

minimum cross section, limited by the water level

- hydraulic c h a r a c t e r i s t i c of the waterway nP = F = 5-7 - cross section of the typical vessel

106 p

- number

r

-

of vessels coupled side-by-side

reduction coefficient: two-way stretch one-way stretch waterway tunnel

(e)

-

vIpaX

= 1 r = 0.6

r = 0.5

admissible velocity of the flow

vmax = F + A F -Qp A

r

(2.34)

.b . T

enlargement of the minimum cross section corresponding to the discharge Q

-

velocity of f l a w

'he design speed of vessels should be

w

=

0.55

-1

(2.35)

,

The velocity of flcw i s limited by the follawing equations v = 0.5

.w

but a l s o by

, i.e.

v = 0.275

.V-

(2.36)

I

v - vmx

The f l m velocity not only determines the speed when loaded (10 t o 400 km per day), but a l s o the operation capability and manoeuvrability of vessels and a r t i culated formations, as well as the necessary energy i n p u t and fuel consumption. The required speed of vessels i n relation to the channel cross section influences the backflow and thus the erosion rate. ( f ) routing of the fairway: The routing of the fairway including i t s extension i n curves determines the speed, fluency, safety, method of operation and the energy consumption of the inland water transport. The s t r a i g h t route is most suitable: two l i m i t s e x i s t for the value of the perimeter:

-

the minimim perimeter, securing fluent and safe operation without any significant restrictions,

-

the exceptionally acceptable perimeter, requiring limited speed and thus re-

ducing the fluency of operation (Tab. 2 . 7 ) . ?he exceptionally acceptable perimeter has to be used i n built-up areas, deep narrow valleys and natural river beds. Secondary characteristics of water courses which have an impact on the course and safety of transport operation, the operation t i m e and period , interruptions to operation, its r e s t r i c t i o n to some 220 to 340 days a year and the different technical measures employed include

-

flood occurrence

107

-

periods of low discharges i n non-canalized r i v e r s

- ice-bound regime

-

meteorological f a c t o r s , e s p e c i a l l y fog and s t r o n g wind occurrence maintenance, r e p a i r and r e c o n s t r u c t i o n work, e s p e c i a l l y i n the case of one-

way s t r e t c h e s - technologically u n s u i t a b l e and obsolete c o n s t r u c t i o n s , such a s locks and weirs. The f r e i g h t turnover of a waterway depends on the s t r e t c h with the lowest f r e i g h t c a p a c i t y , i . e . on the locks i n the case of double-way canals. The capac i t y of a one-way canal i s generally smller than t h a t of the lock. 'he f r e i g h t turnover of the lock can be expressed by the formula ( t per year) tn

-

duration of the operation cycle (lockage)

nd

-

n m b e r of v e s s e l s per day

d - duration of the t r a n s p o r t season

(2.37)

(hours)

(days)

m

-

number of simultaneously locked v e s s e l s

W

-

carrying capacity of one v e s s e l (medium)

(t)

a

-

c o e f f i c i e n t of capacity u t i l i z a t i o n

(0.7-0.9)

b

-

c o e f f i c i e n t of the uneven u t i l i z a t i o n of the waterway (1.25-1.75)

t

-

average number of operating hours per day

(12-24 h)

The volume of water needed f o r one lockage is

(m31

V l = F . h + W = s . d . h L W

(2.38)

and f o r the s l a n t walls of the lock

.

.d .h

W

V1

= ( 8 +

V1

-

b

- lock width

(m)

a

-

(d

2 h

tg6)

volume of water needed f o r one lockage

lock lenpth

h - head

-

slope of the lock walls

d

)

(m3)

(m) (O)

The plus s i g n before the value of the c a r r y i n g capacity is used f o r the

108 passage upstream, because water i n the lock has to be replaced a f t e r its departure from the lock. The minus s i g n i s used f o r the passage downstream. Idhen technical measures safeguard reciprocal lockage i n both d i r e c t i o n s , only 50%of the volume i s needed

v2

1

=

2 . v1

and, therefore f o r p r a c t i c a l cases (m3 1

V = k . a . b . h

-

k

c o e f f i c i e n t of operation coordination

( 1 k

(2.39) 0.5

1

The f r e i g h t t u r n w e r i n a complicated network of inland waterways has to be expressed by a more complex formula

/)2. d

K = a

2

ms

.

.

t

. ms . Ws .

(wm + wn)

+ 2 Pn

( P m - P n ) . tl

.

( t per year)

(2.40)

c o e f f i c i e n t of the uneven u t i l i z a t i o n of the waterway throughout the year

. b,’ - annual

average of the carrying capacity of simultaneously locked

vessels

wm

, wn -

Pm

3

pm

+

tl

t2

Pn

u t i l i z a t i o n of the carrying capacity i n e i t h e r d i r e c t i o n (%)

,

- percentage of vessels i n e i t h e r d i r e c t i o n

pn = loo%, pm

- pn>

0

-

duration of one lockage i f lockage i n the same d i r e c t i o n follows

-

(hours) ( = L e t i - t3 t6) i=l duration of one lockage i f lockage i n d i f f e r e n t d i r e c t i o n follows

-

(=

5

ti

-

Tab. 2.7)

1=1 Bearing t h i s i n mind, the annual water requirement f o r a lock is = 2

R

. Ka . m

a

S

( Pn.V2

. Ws .

+

/Pm+Pn/.V1

(wm+ wn)

1

(m3 per year)

(2.41)

The operation of locks is an inherently in-stream use, but using water i n t h i s way r e s u l t s i n a loss of i t s p o t e n t i a l energy both i n the passage upstream and i n the passage downstream: J U = h . ( a . b . h + W ) . C J d = h . ( a . b . h - W ) . F Ju

- loss

of potential energy i n the passage upstream

109 Jd - loss of p o t e n t i a l energy i n the passage downstream

(kg .m-3)

b” - u n i t mass of water

R e passage upstream decreases the energy consimp t i o n ( i .e. a l s o f u e l consumption), the reverse operation of locks f o r the passage downstream has no e f f e c t on f u e l consumption. TABLE 2.7

Symbol

Duration

Opera t i o n

drift in d r i f t out tl(5) =

t5

+ (5-10).% r

(m. s-l)

see formula

r =0.6-1 1 r =0.8-2.2

t2

opening and c l o s i n g the upper g a t e

6C-120

t4

opening and c l o s i n g the lower gate

60-120

f i l l i n g the lock

t3 t6

emptying the lock t3(6) =

h

7

Velocity

(S)

5

300-900 ~0.02-0.06

Duration of one operation cycle of a navigation lock with two-way t r a f f i c . Symbols a r e i n t e x t . The water requirements f o r inland navigation a r e determined by the s i z e of the l a r g e s t l o c k , i . e . i n the case of u n i f i e d h o r i z o n t a l dimensions by the volume o f the lock with the h i g h e s t head i n c l . r e l e v a n t water l o s s e s . These water requirements can be reduced by (a)

two grouped locks

(b)

wa ter-saving tanks

Cc) pumping (d) v e s s e l l i f t s , canal i n c l i n e s , water slopes. The f i r s t two technical measures reduce the water requirements and simultaneously i n c r e a s e the duration of lockage. Pumping and mechanicel l i f t i n g equipment can shorten t h i s operation, b u t , unless a counterweight is used, t h i s is

.

energy-demanding By grouping two locks, i.e. by emptying one lock i n t o another, water requirements can be reduced by 50%. During r o u t i n e operation of grouped locks, the duration of t h e lockage is shortened by c l o s i n g the valve before equalizing the water l e v e l s , thus i n c r e a s i n g the water requirements t o the average value Ra = 0,53

k

-

.k .a .b .h

c o e f f i c i e n t of the operation coordination

(2.43) (1 > k > 0.5)

110 The e f f e c t of water-saving tanks on reducing water requirements depends on their s i z e , number and technical arrangement (Tab. 2.8). The water requirements of a lock with water-savinp tanks of the same s i z e R

S

=

(2.44)

n - nunbes of water-saving tanks

x =

9 - r a t i o of the s i z e of

Y

hn --

=

the lock to the s i z e of the tank

r a t i o of the water s t r a t a hn for particular tanks and of the difference of water tables ho reached a t the moment of the cmencement of f i l l i n g up fran the next tank for time-saving reasons

ho

TABLE 2.8

Number of reservoirs

Full levelling of water tables (y = 00 ) requirements

v,

:

\lo

P a r t i a l levelling of water tables (y = 1 0 )

Ratio of duration

requirements

tS : to

:

vs

vo

duration ts : to

0.687

1.145

1.414

0.523

1.276

1.581

0.423

1.395

0.355

1.505

1

0.666

1.225

2 3

0.5 0.4

4

0.333

1.732

Decrease i n water requirements and the extension i n duration of one operation cycle of a navigation lock with watersaving reservoirs, their area being equal to that of the lock. The following formula can be derived for the duration of the f i l l i n g up of the lock with wa ter-saving tanks

1

n

br;

-4+ y q Chrs )

to

- duration

(2.45)

of the f i l l i n g up of the lock without watersaving tanks (hrs)

Water requirements for lockage r e s t r i c t other in-stream uses, e.g. for hydropmer generation, and should only be considered when the natural supply by river discharges is not s u f f i c i e n t . Water losses of navigation operation are caused by (a)

leakage of gates and valves

(b)

seepage of the bottom and the banks of the canal

(c) evaporation from the free water surface and the increased evapotranspiration from banks affected by the impounded water.

111 'Ihe losses through the leakage of gates and valves depend on t h e i r construction, type of s e a l and technological s t a t e as well as on the lockage frequency. Their value fluctuates between 3 and 5 1.s-I f o r 1 m of head f o r locks 12 m wide. Higher values correspond to a higher frequency of lockage. Inland water transport does not make any important requirements on water quality, except recreational passenger transport, whose success i s closely interconnected with the quality of water. Water pollution fran inland navigation is mainly caused by the liquid fuels used i n vessels, chemical products incl. hydrocarbons and other dangerous substances transported as cargo, s o l i d wastes , degassing, washing and b a l l a s t water, but especially by accidental spillage d u r ing loading, unloading and transloading.

2.3.3

\dater Pmer Utilization

The potential energy of water can be converted i n t o pressure energy by concentrating the head and discharge and i n t o k i n e t i c energy by passing the concentrated discharge through water engines. Zhe value of the e l e c t r i c energy generated from this k i n e t i c energy reaches (2.46) Q

-

discharge

<m3.s-l)

H

-

net head (without intake losses)

(m)

i~ N

-

coefficient of efficiency (turbine, gears, generator)

.

u n i t mass of water

(kg m-3 )

power generated

(kw)

To e x t r a c t the maximum power and energy a t the optimum cost the design crit e r i a focus on the choice of the location, design discharge and head, lay-out, s i z e and number of units e t c . by suitable numerical techniques. This approach embodies an optimization of the power output/cost-benefit r a t i o e t c . on the

basis of a r e a l i s t i c operation of the plant, i n the framework of the topographic/ hydrological s i t u a t i o n and power market demands. The specific advantages of hydropower plants open up favourable p o s s i b i l i t i e s of application as

-

run-of-river

plants ( i n the original r i v e r bed o r i n a bypass canal, using

discharges which a r e available without considerable storage),

-

storage plants (using reservoirs f o r water accunulation and thus affording

the p o s s i b i l i t y of peak pmer generation)

-

pumped-storage plants (repumping accunulated water during a surplus of energy

i n the network and generating power during peak demand)

112 -

tidal power p l a n t s ( u t i l i z i n g the head and flow produced by the t i d e )

-

power s t a t i o n s using the energy of waves ( n o t f e a s i b l e y e t ) .

NATIONAL ECONOMIC, ENVIRONMENTAL AND SOCIAL POLICES

ENERGY DEMAND ANALYSIS AND FORECAST

ENERGY SURVEY

I EXISTING POWER SYSTEMS

POTENTIAL

Project catalog coal, gas,oil. nuclear,

PROJECTS

hydro, non-conventional

PROJECT SELECTION OPTIMIZATION OF POWER GENE RAT ION AND TRANSITION SYSTEM EXPANSION

Criteria

I Cover the growing energy demand 2 Minimize energy cost 3 Minimize investment cost 4 Maximize exploitation of the discharge and head available Security of the energy supply Local development Conservation of res-ources Protection of the environment Secondary benefits

5 6 7 8 9

I PRICING

ECONOMIC

POLICY

EVALUATION

Criteria Net present worth NPW Economic r a t s of return ERR Criteria. Capital available

RECOMMENDED POWER DEVELOPMENT PROGRAMMES TIMING

Fig. 2.5. Block diagram f o r the p r o j e c t s e l e c t i o n , optimization of power generat i o n and t r a n s i t i o n system expansion i n the framework of n a t i o n a l economic, environmental and s o c i a l p o l i c i e s . Hydropower i s the only dependable renewable source of energy and o f f e r s , i n a d d i t i o n i n comparison with thermal and nuclear power, a s w e l l a s with the unconventional energy o p t i o n s , the following b a s i c advantages : -

f l e x i b i l i t y of operation,

-

p o s s i b i l i t y of multipurpose u t i l i z a t i o n , high r e l i a b i l i t y and long s e r v i c e l i f e , p o s i t i v e o r almost n e g l i g i b l e environmental impact ( i f environmental f a c t o r s

a r e accordingly taken i n t o account during the design and o p e r a t i o n ) ,

-

low operating c o s t s , p o s s i b i l i t i e s of using l o c a l m a t e r i a l s and labour. The following i n d i c a t o r s a f f e c t i n g the choice of the optimum design discharge

113 and head have to be considered with a p o s s i b l e environmental h p a c t of the p m e r p l a n t layout: - u n i t c o s t of energy (kwh) should be competitive with o t h e r energy options,

-

i n s t a l l e d capacity (kwh) should be optimum f o r i n t e g r a t i o n i n t o the network

power market, - energy output i n the period o r season of maximum energy demand (kwh) should be optimum. Available simulation models have the c a p a b i l i t y of simulating any hydropower p l a n t o r e l e c t r i c a l system, Computations m y be performed a t a desired l e v e l of accuracy c o n s i s t e n t with the a v a i l a b i l i t y of the input d a t a . These programs may be used t o determine hydropower p o t e n t i a l , t o optimize design discharges, heads, d a m heights and r e s e r v o i r s i z e s , t o study the f e a s i b i l i t y of new developments

and t h e i r impact on e x i s t i n g systems, e f f e c t s of changes i n operational procedures i n e x i s t i n g systems e t c . (Fig. 2.5). MW

\ \

0

0 2

INCREMENTAL COST BENEFIT

-

0.4

06

08

10

Fig. 2.6. S e l e c t i o n of the optimum capacity of a hydropower p l a n t by superimposing the incremental cos t-benefit r a t i o function on t h e power duration curve according to Fahlbusch (1983). According t o Fahlbusch (1983) the optimum capacity of a hydropower p l a n t , i f the o b j e c t i v e i s the maximum e x p l o i t a t i o n of energy and n o t the provision of peak c a p a c i t y , is t h a t value of t h e o r e t i c a l capacity N f o r which the complemen-

tary emulative d i s t r i b u t i o n of power output equals t h e marginal benefit-cost ratio

(2.47) +f(x)dx =

C ") M. to

(2.48)

Solving t h i s equation f o r the optimum N requires superimposing the margiOP t ~l cost-benefit r a t i o function on the power duration curve (Fig. 2.6).

114

x

-

power output

f(x)

-

p r o b a b i l i t y d e n s i t y of power output x

C(N)

-

annual c o s t a s a function of capacity

- value of to - duration

M

energy per kwh of one year i n hours (8760 h r s )

AC

-

AB

- incremental

incremental c o s t s benefits

A hydropower development p r o j e c t may e x h i b i t an incremental cos t-benefit

r a t i o of less than u n i t y and s t i l l be uneconomical, r e q u i r i n g s u b s t a n t i a l investment f o r the construction of s t o r a g e and diversion f a c i l i t i e s , which may be l a r g e l y independent of the design capacity. The trouble-free and economic operation of power p l a n t s requires a low cont e n t of sediments (both bed load and suspended matter, e s p e c i a l l y hard minerals), a low content of f l o a t i n g d e b r i s and chemically non-aggressive water q u a l i t y , which means t h a t a low content of oxygen, low chemical a g g r e s s i v i t y and a low temperature i s required i n order t o r e s t r i c t : (a) (b)

c a v i t a t i o n and chemical d i s i n t e g r a t i o n of t u r b i n e s , abrasion of pressure p i p e l i n e s , s p i r a l c a s e , t u r b i n e s , l i n e r and o t h e r

technological equipment, ( c ) sedimentation i n water conveyance s t r u c t u r e s . The t r a n s p o r t of bed-load and suspended matter r e q u i r e s the construction of s p e c i a l i n t a k e s t r u c t u r e s and s i l t basins. I t a l s o requires a minimum flow r a t e of some 1 . 0 m.s-',

dependent on the c h a r a c t e r i s t i c s of the p r e v a i l i n g p a r t i c l e s ,

i n order t o avoid sedimentation i n the conduit system. The design dimensions of these s t r u c t u r e s should be determined i n t h e light of the s i z e and density of the p a r t i c l e s and t h e i r volume which can be allcwed t o e n t e r the system. No o p e r a t i o n a l troubles caused by sediment t r a n s p o r t occur i n s t o r a g e p l a n t s with a r e s e r v o i r which has a s u f f i c i e n t t r a p e f f i c i e n c y . Run-of-river

plants

cope with s e r i o u s sediment problem when t h e design discharge Qi exceeds the crit i c a l discharge Qs a t which the bed load starts t o move:

Q;

< 4,

(m3.s-l)

(2.49)

I n rivers with a heavy bed load t r a n s p o r t i t is useful t o l o c a t e t h e off-take i n an eroded s e c t i o n . I f the off-take i s located i n a s e c t i o n where sedimentation p r e v a i l s , i t is necessary t o narrow t h e r i v e r bed i n t h i s p a r t i c u l a r s e c t i o n . The bed load t r a n s p o r t normally needs the energy of some 50% of the discharge. To avoid sediment t r a n s p o r t problgns during a period of increased bed load trans-

li5 port (Qa

>

Q,),

the hydropower s t a t i o n may u t i l i z e some 50% of the discharges

available Qe =

1

7 . Qa

(m3. s-l)

(2.50)

even when t h e i n t a k e i s w e l l l o c a t e d . p l a n t i n a river with a heavy bed load The operation of a run-of-river t r a n s p o r t and f l u c t u a t i n g discharges i s , t h e r e f o r e , limited i n two time periods because of the lack of water during a period with a c t u a l discharpes Qa lower

-

1.3 3.4 - 5

I d e a l s h a r e of t h e water t a b l e area (%) 20%

40% 40% min 16.25.14 m

Required water depth and t h e i d e a l share of t h e water t a b l e area f o r r e l e v a n t c a t e g o r i e s of v i s i t o r s t o n a t u r a l and a r t i f i c i a l bathing pools. The q u a l i t y of n a t u r a l bathing pools depends on the morphological and aesthet i c conditions of the environment and on a favourable water depth f o r s w h e r s , non-swimmers, c h i l d r e n and d i v e r s (Tab. 2.11, 2.12). The a c t i v e a r e a on b i g r e s e r v o i r s i s a zone near the s h o r e , some 50 m wide. The s i z e of bathing and swinnning pools should correspond t o the length of race t r a c k s , which a r e r a t i o s of 50 m: 10 m, 12.5 m, 16.67 m and 25 m. I n a swimming pool of 50.21 m, a s recornended by FINA with a water depth above 1 . 8 m,

TABLE 2.10

1. Water p o l l u t i o n (class) 2. Water temperature

Ia

Ib

11

>25

> 18

> 14

(14

> 1.6

2. R a i n f a l l t o t a l i n s m e r (m)

(250 50 20 >10 5 1.5

> 2 >> scarce

partially

2

3. A i r temperature OC (% humidity)

nil

4. Air pollution

yes

5. Moise

Categories of parameters which determine q u a l i t y of r e c r e a t i o n .

21-26 (18-70) no

no

(2.52)

Rc - r e c y c l e d discharge A

- a r e a of t h e swimming pool

(mL)

Idhen water is being c i r c u l a t e d i n a n a t u r a l bathing pool, the recomnended 3 design discharge for t h e treatment p l a n t is 0.5 m per c a p i t a and day. Large %hrming pools r e q u i r e a continuous process of c i r c u l a t i o n ; an i n t e r r u p t e d process is r e c m e n d e d f o r srrall pools with only a 4 hour cycle.

As a w a t e r s a v i n g technique and i n o r d e r t o improve the water q u a l i t y , the c i r c u l a t e d water can be used f o r showers, flushing, f i l t e r washing and the cleaning of t h e r e c r e a t i o n a l amenities.

2.4

MUNICIPAL AND RURAL IdAER REQIJIREMEITE

The amount and q u a l i t y of water used i n human settlernents influences the soc i a l development of t h e s o c i e t y concerned and a f f e c t s t h e b i o l o g i c a l development of the i n d i v i d u a l human beings. The q u a l i t y and q u a n t i t y of drinking water supp-

121

l i e d t o organisms has a d i r e c t e f f e c t on h e a l t h . Water s u p p l i e s important minerals t o organisms. The long-term u t i l i z a t i o n of the same water f o r d r i n k i n g and cooking purposes by a n i n d i v i d u a l influences the development of the organism and i t s h e r e d i t a r y s i g n s . The amount and q u a l i t y of water used f o r washing and bathing has a considerable influence on h e a l t h conditions i n human s e t t l e m e n t s . The e x t e n t of these influences depends on the physiological a d a p t a b i l i t y and c h a r a c t e r i s t i c p r o p e r t i e s of m n i n t h e framework of the homeostasis of h i s own b i o l o g i c a l system, on the energy input and output of r e l e v a n t i n d i v i d u a l s , on the supply of nutriments, vitamins and on o t h e r s a n i t a r y conditions. The mode and frequency of t h e r e l e v a n t organism's c o n t a c t with water is a f u r t h e r important f a c t o r . Water demand i n households, workshops and public s e r vices has d i f f e r e n t q u a l i t y requirements f o r : ( a ) drinking (and o t h e r uses r e s u l t i n g i n i n t e r n a l c o n t a c t of water with the human body : mea 1 preparation) , (b) o t h e r domestic uses i n c o n t a c t with the s u r f a c e of the human body physical care : washing, showering, bathing d i s h washing laundry ( c ) using water i n systems where c o n t a c t with the body can be avoided

laundry house cleaning and c a r washing yard and park watering, street cleaning, sewer f l u s h i n g t o i l e t rinsing f i r e extinguishing (d) using water i n closed systems heating a i r conditioning. The supply of water of uniform q u a l i t y f o r each of these technologically d i f f e r e n t purposes is the simplest method t o safeguard a l l these requirements by means of one supply network. I n p r a c t i c a l cases t h i s method m y not appear

a s the most economic o r s u i t a b l e t o p o s i t i v e l y influence the development of human organisms and t h e i r h e a l t h .

2.4.1 Water Requirements f o r Drinking and Cookirg Purposes The physiological water requirements of a healthy i n d i v i d w l reaches a n average of 1.5 t o 15 liters p e r day. The metabolic processes of each individual tend to achieve a balanced s t a g e , depending on c l i m a t o l o g i c a l conditions personal weight and i n d i v i d u a l a c t i v i t i e s (profession, hobbies) and customs (drinking, e a t i n g , dressing) thus r e q u i r i n g a s t a b l e complementing o f water l o s s e s . The physiological water requirement of some 2.5 1 per c a p i t a and day is co-

122 vered 50%by food and 50% by beverages. I n addition t o t h i s , a healthy organism produces some 0.3 1 of metabolic water per day by processing the basic nutriments. The physiological water requirements per capita and day Ri can, therefore, be expressed by the following equation Ri = f (w, a , c , h , f , m)

- Rf

( 1 per capita and day)

(2.53)

w

-

individual weight

a

-

a c t i v i t i e s (profession, hobbies, age)

c

-

climate (especially temperature and humidity)

h

- personal habits (quality and quantity of dripking, dressing e t c . )

f

- food canposition

m

-

metabolic function (less important)

Rf

-

content of water i n food.

The hman organism is influenced by the amunt and quality of accepted water,

especially i f ancestors have been living i n the same place f o r generations. The anorganic and organic constituents of water have a d i r e c t influence on the hmlan organism, i.e. physiologically, and an indirect influence, i . e . psychically, both positively and negatively. The human organism generally, depending on i t s individual properties, may get accustomed t o the influence of natural water cons t i t u e n t s and their canbination, o r may produce relevant a n t i m a t t e r . But some constituents of water, especially those corning from pollution through wastes f r m industry and agriculture, m y cause diseases o r morbid changes, namely (a)

teratogenic (may induce morbid changes of the organism)

(b)

mutagenous matter (may produce hereditary changes)

(c) cancerogenous matter (may cause m l i g n a n t t m u r s ) . These matter and t h e i r function a r e not sufficiently known, because the reaction of any organism to such matter depends t o a considerable extent on t h e i r quantity, canbination and concentration, a s well as on the organism's health and habits. The degree of resistance depends on the health standard, hereditary and personal resistance o r disposition and age of the individual concerned. Occasional drinking of unsuitable water may not be dangerous when the relevant harmful concentrations a r e law and when the relevant organisms does not contain potentially dangerous germs. The organism's own bacteria l i m i t the development of the accepted bacteria. On the contrary, daily drinking of physiologically o r sensorially unsuitable though s a n i t a r i l y non-defective water which only corresponds t o basic standardized indicators may cause unexpected comequences

.

To achieve the healthy developmmt of the population, i t is e s s e n t i a l to

123 secure an everyday supply of physiologically b e n e f i c i a l and s e n s o r i a l l y aggreea b l e water, a t l e a s t f o r drinking purposes. I f the q u a l i t y of water i n the pipel i n e system does not correspond t o these c r i t e r i a , i t is v i t a l to supply b o t t l e d water of physiologically b e n e f i c i a l q u a l i t y , a t l e a s t f o r sucklings. For t h i s reason, i t is a l s o a d v i s a b l e t o organise t h e production of a l l beverages using, without exception, groundwater resources of the b e s t q u a l i t y a v a i l a b l e . The standards f o r water q u a l i t y should be derived from the mode of contact of hurnan organism with water, because t h i s is

-

( a ) r e g u l a r l y absorbed by the organism, without b o i l i n g a f t e r boiling, o r (b) i n temporary c o n t a c t with the whole s u r f a c e of the organism (and m y be

a c c i d e n t a l l y swallowed during showering, swimming e t c . ) ( c ) i n r e s t r i c t e d i n c i d e n t a l s u r f a c e c o n t a c t with a p a r t of the body (during washing, cleaning, s p r i n k l i n g e t c . ) (d) used i n closed systems, excluding c o n t a c t with the organism ( a i r cond i t i o n i n g , h e a t i n g , t o i l e t r i n s i n g , d r i p and subsurface i r r i g a t i o n ) . I n only one supply system is used f o r a l l the purposes of municipal o r r u r a l water supply, a s is u s u a l , the water q u a l i t y should correspond to the h i g h e s t q u a l i t y requirements, i . e . to drinking water requirements. I f such water is not I

a v a i l a b l e f o r a l l required purposes, s a n i t a r i l y non-defective water should be used f o r such purposes, where c o n t a c t with the organism cannot technically be excluded. The supply of the necessary amount of such water, whose value depends on l o c a l conditions , prevents the occurrence of w a t e r b o r n e diseases. The l e v e l of knowledge about t h e b i o l o g i c a l importance of the d i f f e r e n t elements and components p r e s e n t i n water and t h e i r canbination i s generally low, except the a p p r e c i a t i o n of the medical e f f e c t of some mineral waters. Not even the e f f e c t of such b a s i c components a s calcium Ca o r magnesium Mg has been s u f f i c i e n t l y i n v e s t i g a t e d . The knowledge on the e f f e c t of t r a c e elements and e s p e c i a l l y o f the s y n e r g e t i c o r anta,gonistic e f f e c t s of t h e i r combinations: iodin J and f l u o r i n e F, f l u o r i n e F and molybden Mb e t c . , is a l s o low. The r e a c t i o n of the organism t o the impact of these elements can have considerable individual o r h e r e d i t a r y e f f e c t s , a l s o i n canbination with o t h e r e x t e r

nal f a c t o r s such a s climate, overloading of the organism, the organism’s stage of developnent, h e a l t h state e t c . Water of a d i f f e r e n t q u a l i t y can be used f o r d i f f e r e n t purposes of domestic use and relevant q u a l i t y i n d i c a t o r s f o r any cate-

gory of i t s p a r t i c u l a r use can be derived frcm the (a)

s a n i t a r y non-defectiveness,

(b)

physiological b e n e f i t ,

(c)

s e n s o r i a l agreeableness (Fig. 2.8).

124

. toilet rinsing sprinkling

washing, bathing cleaning, laundry

meal preporation,

drinking

cooking

Fig. 2.8. Hierarchy of goals and requirements on water quality f o r municipal water supply and p o s s i b i l i t i e s of water delivering water of d i f f e r e n t quality f o r relevant purposes. The physiological benefit f r m water depends not only on i t s chemical and bacteriological canposition, but a l s o on its temperature, flavour and odour a s the cmponents of i t s sensorial properties. The q u a l i t y of water i n the supply network depends on the quality of raw water and can be defined by means of standards. The i n t e r s t a t e coordination of these values i s organized under the auspices of the World Health Organization and the International Standard Organization. The health and optimum development of the population can be permanently and e f f e c t i v e l y influenced through the u t i l i z a t i o n of appropriate water resources and through sophisticated water treatment (Tab. 2.14, 2.15, 2.16). Water q u a l i t y can be defined and standardized by means of indicators expressing the limiting concentrations of relevant components and other water proper-

ties with regard t o t h e i r health e f f e c t . Their values have t o be derived from the character and intensity of impact of the relevant canponents of the human organism. The number, type, methods and frequency of sampling and analytic methods a r e a l s o standardized. The relevant values can be standardized a s (a) maximum permissible values - water which exceeds these values may not be considered a s drinking water (mandatory l i m i t s ) , (b) reccmnended l i m i t s - the r a t e of t h e i r occasional o r permanent excess has to be analyzed individually i n consideration of local conditions (and o f f i c i a l l y approved). Relevant drinking- water quality requirements may d i f f e r f o r temporary o r in-

125 TABLE 2.14

Selected i n d i c a t o r s

Physical: - colour

'Pt

300

According t o the p l a tinurncobalt scale

Chemical : a ) matter influencing s u i t a b i l i t y f o r drinking: Total evaporation residium Iron (Fe) t o t a l Manganese )In Cu Copper Zinc Zn @SO4 + Na2S04 Sodium alkylbenzenesulphona t e b) matter a f f e c t i n g h e a l t h : N i t r a t e s NO;

Fluor F- d e r i v a t i v e s

c ) toxic matter : Phenol d e r i v a t i v e s Arsenic As Cadmium Cd Chromium Cr-6 Cyanids CNLead Pb Selenum Se Total -activity d) matter i n d i c a t i n g p o l l u t i o n : Oxidability Biochemical oxygen demand BOD5 Nitrogen N ( t o t a l ) h m n i a NH3 E x t r a c t a b l e m t t e r CCE Fat

1000 50 5 1.5 1.5 1000 0.5 45

Higher content when the anmonia content is below 0 . 5 mg.1-1, due t o the corrosion e f f e c t

1.5

G u s ing me tahenioglobinanemia i n s e n s i t i v e individuals i n concentration 100 rng.1-1. Higher concentration causes f l u o r o s i s , concent r a t i o n 0.8.-1.0 mg. 1-1 a r e a n t i c a r e t i c prevention.

0.002 0.05 0.01 0.05 0.20

gas works, chemical industry, volcanic waste from metal coating

0.05 0.01 1000 c.1-1

10.0 6.0 1.0 0.5 0.5 1. 0

Maximum peimissible content of chemicals i n raw water t h a t m y be t r e a t e d f o r drinking purposes, according t o the recomnenda t i o n of t h e World Health Organization. d i v i d u 1 water supply and for p e m n e n t c o l l e c t i v e municipal and r u r a l supply, where mre s t r i c t c r i t e r i a have t o be applied with regard t o possible i n f e c t i o n , epidemics e t c . From the metodological p o i n t of view i t is possible to d i s t i n guish such i n d i c a t o r s a s

126 TABLE 2.15 Class

Bacteriological pollution

Bacteria c o l i per 100 m l

Required treatment

I.

slight

0

-

50

11.

medium

50-

5000

current processes : coagulation, filtration

50000

special treatment water has t o be used i f inevitable only

111.

IV.

high excessive

500

-

>50000

disinfection only

Classification of raw water used f o r drinking purposes a f t e r i t s bacteriological pollution according t o the recomnendation of the World Health Organization. TABLE 2.16

Water course Chloride (CL-) Sulphide (SO); Calcium (Ca) Magnesium (Mg) Fluoride (F)

400 300 300

200

Raw water

Drinking water recom. max.

200 200 250 125

20 60 36 30 1.0 0 20

2.4

1.5

Ammonia (W3)

3

0.5

Nitrate (NO;) Nitride (NO;) Sulfate (SO$-)

50

-

25

-

-

30 70

60 1.3

0.2 30

0.01

0.05 50.0 0.02

1.5

0.5

0.05

0.1

Manganese (Mn) Cyanide (CN)

0.5 0.2

0.2 0.01

0.01

0.03

0.01

0.05

Zinc (zn) Nickel (Ni) Lead (Pb) Chromium (Cr) Arsenic (As)

2 0.1 0.1 0.1 0.5 0.2 0.1

2

1

2

fiospha t e (PO:-) Iron (Fe- t o t a l )

Copper (CU) Selenium (se) Mercury (Hg) Cadmium (b) Alluminiun (Al) Free Chlorine (c1) W g e n (02) (min 5.0)

25.0

0.05

0

0.04

0

0.04

0.05

0.05 0.04 0 0.003 0.0001 0

0.05 0.01

0.04 0.05 0.05

0.005

0.001

0.3

0.005

0.004 0.005 0.05

0.1

0.3

8.0

10.0

Selected admissible values of ion content (mg.1-I> i n water courses; surface Water used for municipal water supply and i n drinking water (recmended and maximum admissible values),

127 (a)

bacteriological and biological icdicators

(b)

chemical and physical indicators.

Drinking water may be defined as s a n i t a r i l y non-defective water when i t does not cause any health troubles o r diseases, even a f t e r lorg-term u t i l i z a t i o n . I n addition, water delivered f o r municipal and domestic purposes should be wholesome and palatable. Water from underground sources i s preferred t o surfacewater delivery. Groundwater contains more bioelements important t o human organism, has a s t a b l e temperature, and is l e s s subject to contanination than surface water resources. But the very high deman-d f o r municipal water frequently precludes the exclusive use of groundwater f o r municipal water supply because of the limited capacity of groundwater resources. Bacteriological non-defec tiveness i s an indispensable requirement. Physical and chemical indicators tend to demonstrate possible pollution i n the water resource o r during water purification and transport. The term raw water refers to water from the surface or under,eround resource, whose q u a l i t y only depends on natural factors and possible anthropogenetic pollution. Water treatment or water purification is a combination of technological processes aimed a t changing the quality of raw water to the required level (Fig. 2.9). The quality of treated water depends on the quality of raw water: not only

on the content of undesirable matter not removed during waOer treatment, but a l s o on the content of desirable matter which was removed during treafment or which does not appear i n the raw water. For example, the lack of minerals in drinking water, c h a r a c t e r i s t i c f o r treated water from surface resources, incidentally causes h e a r t and vessel diseases. The basic requirement for the quality of raw wter intended f o r municipal water supply is its non-defectiveness frcm the toxicological point of view and the s a f e running of technological processes during its purification. The values f o r the maximuin permissible concentration of harmful matter a r e gradually being defined with mre precision. Particularly important is the quant i t y of harmful bacteria and of organic ratter, whose concentration increases the probability of noxious e f f e c t s . The harmfulness of t h i s matter a l s o depends on its combination. Unpleasant flavours and odours which a r e d i f f i c u l t to remove a r e another important factor. Water treatment decreases the content of undesirable components to below the

level of maximum permissible concentrations and increases the s u i t a b i l i t y of the water f o r transport i n the pipeline network. A l l pathogenetic organisms, in particular the large group of Salmonella-Shigella bacteria and viruses, have to be removed by disinfection. Viruses a r e often r e s i s t a n t to current disinfection methods , including :

128

WATER

PRETREATMEN MICROF ILT RAT 10N

PRETREATMEN SEDIMENTATI0 N INFILTRATION, SLOW F ILT RAT I0N

OXIDATION

0 XI D AT ION

C 0AGULATION, SOFTENING

F ILTR AT I0N

'4

A DSORPTON

INFILTRATION, SLOW F ILT R A T 10N

SEDIMENTATION

DES INFECTION

TREATED WATER

Fig. 2.9. Basic ccmbinations of methods of water treatment for municipal water supply. (a)

physical ( l i g h t u l t r a v i o l e t rays, radioactivity

ultrasound, e l e c t r i c i t y ) (b) mechanical ( f i l t r a t i o n

clarification

-

r-radiation, heat,

sedimentation, u l trarnicrof i l t r a -

tion, reverse osmosis, capable of removing 95-99% of bacteria) (c) chanical (chlorination, i . e . addiqg of i t s compounds, other halogens, oxygen e tc. ) (d) oligodynamic (katadynisation and other disinfection methods using various heavy metals: s i l v e r , copper and t h e i r s a l t s ) . An excess of disinfection matter, e.g. chlorine, forms a protection against

pollution during transport i n the pipeline network. Its extinction a t the end of the network m y indicate relevant pollution, which may be of pathogenetic ori-

gin. But chlorination m y a l s o produce adverse effects: trichlorine methane derivatives , produced by reacting chlorine on humine acids, currently occurring

in surface waters, cause the dissemination of cancer according to Maugh I1 (1981). Apart from sanitary requirements, the quality of drinking water should cor-

129 respond to the requirements of economical and continuous transport i n the pipeline system, not causing corrosion or clogging. The optimum water quality for this purpose depends especially on the degree of over-saturation and undersaturation with calcium carbonate CaC03. This s t a t e can be characterised by langelier's index, i . e . by the difference between the actual pH factor of water and balanced pHs, when the protecting a l k a l i n i t y corresponds to tke concentration of carbon dioxide C02

Is

=

PH - PHs

(2.54)

TABLE 2.17

Material

Concrete

0

Saturation index

Asbestocement

Steel & cast iron

0

0

Glass & plastics 0

Oversa tura tion with calcium carbonate

-

as CaC03

- as

Ca

5-10 mg, 1-l

5-10 mg. 1-l 0.05-0.1 mol.1-I

5 rng.1-1

Aggressive C02 Calcium Ca Total a l k a l i n i t y Factor pH Sulpha tes SO:-

-

5 mg.1-1

5 mg.1-1 16 mg.1-I

-

0.8 mm01.1-~ 637

0.8 mnol.1-I 0.8 m1.l-l

-

6.0

250 mg.1-I

250 mg.1-l

15 mg. 1-l

15 mg. 1-l

Suspended matter COD (by pemnganate)

5-10 mg. 1-l 0.05-0.1 -1.1-I

1000 mg. 1-1 75 m g . P

-

15 mg.1-l

~ _ _ _ _ ~ _ _ _ _

~

Degree of aggressivity

5-10 mg. 1-1

Rate of uniform corrosion e m per year (water temperature below 25OC)

1. mild aggressivity 11. medium aggressivity 111. high aggressivity

50

50

-

150

150

Indicators for safeguarding the s t a b i l i t y of water quality during i t s transport and limiting the corrosion r a t e i n pipeline systems. Degree of agqressivity for determining the efficiency of the water treatment process to l i m i t the corrosion rate. The protection of metallic pipelines has to be achieved by a certain degree of oversaturation with calcium, forming a thin internal protective. This can be achieved under conditions of a high content of the t o t a l canponents of carbonic acid

According to S t m (1962), in the case of a low content of these components, a granular porous matter appears instead of a compact f i l m . The

130 aggressivity of water depends on the character of the material i t contains, and has t o be evaluated on the basis of the limiting values of the pH factor, sulphates SO-: and chlorides C1-. Pipes mde of p l a s t i c materials and glass are

chemically f a r more r e s i s t a n t (Tab. 2.17). For the most part domestic water requirements have to be covered by warm water supply. The mass supply of wann water is often accomplished by a s p e c k 1 pipeline network. The quality requirments for mass supply of warm water is a complex subject. Such water should correspond to drinking water standard and must The temperanot cause excessive corrosion o r clogging of the supply network. ture of warm domestic water should be about 6OoC, because higher temperatures increase the corrosion r a t e . Chemical indicators for warm water quality a r e , therefore, more complicated means of achieving the desired balance for limiting corrosion and clogging (Tab. 2.18). These c r i t e r i a a l s o include the content of magnesium Mg before warming and the mintenance of the diphosphorus oxide P205 concentration above 2 mg. 1-l to 3 mg. I-'.

TABLE 2.18

k

(2.79)

’he intensity with which water is recycled or successively re-used depends on the type and degree of pollution. The closed c i r c u i t operation often requires canplicated and expensive equipment. Water consumption i n industry consists of the consumption required to regenerate the consumption during processing C P ’ the water quality C and losses during treatment, distribution and recycling. q

c = cP + cq

+ k=l

The regeneration of the water treatment, clearing, dustry, water requirements by the supplementary water

k

(m3.sT1)

(2.80)

water q u a l i t y includes water treatment and waste sludge blow-off e t c . During water recycling in ina r e covered by the sum of the recycled water Ro and W abstracted from the resource.

The internal recycling coefficient is the r a t i o r.

1

= --RO

R

-w

W + Ro - 7

The.ratio of the water consmption is expressed by n (2.82)

The r a t i o of the water consumption f o r closed c i r c u i t systems equals almost 1.

A s was mentioned already, water consumption consists of the consmptive use by a product U1, a by-product U2 and by means of wastes U a s well as by return3 able and3non-returnable losses and, therefore Ui + A r + A n i=l (2.83) rc = W

The r a t i o of the water consmption has t o be analyzed separately for the supply, water treatment and recycling system and for water entering the product,

by-product and serving other functional purposes. The relevant values often depend on the season, being. higher i n sumner due t o the higher evaporation r a t e . The water consumption during water supply, recycling and water treatment consists of non-productive losses only. The consmptive use during the technological process of water treatment is a pure loss from the production point of view. These losses can be reduced by technological and operational measures including maintenance, a s well a s by a decrease i n water requirements i n the production processes. The beneficial use of water i n industry can also be expressed by the r a t i o of withdrawal u t i l i z a t i o n

w1

=

-

W - F W

(2.84)

and by the r a t i o of losses

w 2 =

W - F - W - F - R W + R0

(2.85)

Basic indicators of the economy of water use i n industry a r e the water requirements per u n i t of product and the water consumption per u n i t of such a product a s w e l l a s the waste load generated per u n i t of production. Their values depend on each o t h e r , on water recycling and on the technology of prQduction and of water supply. The basic interrelationships can be expressed conceptually i n the form of a j o i n t function:

R'

- water

requirements per u n i t of production

'C - water consmption per u n i t of production

3

(m . t

-1

3 -1

(m . t

)

)

'N

- waste

ri

-

i n t e r n a l recycling c o e f f i c i e n t

A

-

combination of production process and product mix

B

- nature

C

- producFion technology including technology of waste material processing, operating r a t e

load generated per u n i t of production (t.t-')

of raw material used, which a l s o influenced by-product production and waste material processing i n c l . material recovery

D - water q u a l i t y (water q u a l i t y indicators q l , q 2 , . E

-

M1

- water

P$

-

.. .qn)

law and order, administration, the e f f i c i e n c y of t h e i r function r a t e s and cost of water treatment

c o s t of waste water treatment and e f f l u e n t disposal r a t e s .

153 Water consumption, with t h e exception of cooling water, water f o r mining and the use of water i n t h e food i n d u s t r y , does not generally form a s u b s t a n t i a l p a r t of i n d u s t r i a l water demnd. Limiting water requirements serves t o decrease the q u a n t i t y of waste waters and water consumption, but need not n e c e s s a r i l y lead to a decrease i n the waste load generated, whlch depends more on the production technology. The i n t e r r e l a t i o n s h i p between wa tsr requirement and water consumption is complicated, not only i n terms of the q u a n t i t y of waste water, but a l s o of its q u a l i t y , e . g . the environmental need t o d i l u t e waste water. The s e l e c t i o n of a s u i t a b l e technology from the water resources point of view requires an a n a l y s i s of the combinations of water requirements, water consimption and waste loss penerated per u n i t of production. The decision has to be taken on t h e b a s i s of an economic evaluation of the environmental a s p e c t s of relevant production scenarios (Fig. 2.18). Water f o r Processing, Mining and Hydraulic Transport 2.5.1 I n t h e course of mining and hydraulic t r a n s p o r t water comes i n t o d i r e c t cont a c t with the intermediate or f i n a l product without any thermic impact. During processing water comes i n t o c o n t a c t with t h e product o r e n t e r s the product m i n l y a s a c c o l i n g o r heat-carrying m a t e r i a l . The q u a l i t y requirements f o r water which comes i n t o c o n t a c t with o t h e r products without any therinic changes depend s u b s t a n t i a l l y m the nature , q u a n t i t y and maximun s i z e of the s o l i d p a r t i c l e s , which should be s p e c i f i e d f o r t h e relevant use. No treatment i s required f o r some i n d u s t r i a l u s e s , e . g . f o r the h y d r a u l i c

t r a n s p o r t of s l a g o r coke cooling. Simple pretreatment, e . g .

mechanical, is

of ten s u f f i c i e n t f o r a considerable number of technological processes, e s p e c i a l l y f o r cooling, mining and h y d r a u l i c t r a n s p o r t . During t h i s p r e t r e a m e n t the cont e n t of iron Fe, manganese Mn and aluminium A 1 has t o be reduced. Pretreatment should include processes aimed a t removing ingredients which m y i n t e r f e r e with f u r t h e r water treatment processes. Water which comes i n t o d i r e c t c o n t a c t with the product by mining, benefic i a t i o n of o r e , t r a n s p o r t of ashes and coal , cleaning of gases e t c . , accepts p o l l u t i o n from the raw m a t e r i a l o r the intermediate product. I t has t o be t r e a t e d before the new cycle of use. Heterogeneous q u a l i t y requirements on water f o r processing, which a l s o depend on its t r a n s p o r t i n the p i p e l i n e system, o f t e n r e q u i r e the a p p l i c a t i o n of mu1 tigrade treatment technologies, including (a)

mechanical processes,

(b)

thermic processes ,

(c)

magnetic processes ,

154 (d) chemical processes, (e) biological processes. Chemical water treatment includes softening, decarbonization, deioniza t i o n , demineralization and other processes aimed a t decreasing the content of organic matter and dissolved oxygen, especially by using macromolecular ion exchangers. TABLE 2.24

Interference agents

Negative impact on

Iron (Fe) Manpanese ( h ) Humines

t a s t e and/or colour of tee, coffee, y e a s t , dough, m a l t , beer, milk, cheese, s t a r c h , sugar, tinned food ca t h a l y t i c d i s i n t e g r a t i o n of f a t s , reduction i n d u r a b i l i t y of food

~~

~

~ l c i u m / m f m eium s carbonate

tas t e / f l o c u l a tion of cacao t a s t e of b u t t e r , other milk products, and beer turbiditv/colour of alltoholic beverages, bottom sediments

(caw3 + MgC03)

Chlorides (C1-)

1)

t a s t e of coffee and tea

Natrium (Na) Hydrogencarbona t e

s t a b i l i t y of vitamins

Nitrates

production processes

Oxygen (02)

1)

Putrefactive and iron bacteria, mold fungi, dregs e t c .

oxidation of fats, decomposition of proteins (acce lera tion) negative impact on t a s t e , cause of health d i f f i c u l t i e s , disturbance i n production processes

Negative impact of selected agents on food products:

1) high content

Multigrade water treatment processes combine cheap processes f o r removing a s u b s t a n t i a l p a r t of the undesirable components with m r e expensive processes aimed a t achieving the desired q u a l i t y f o r a limited volume of water f o r cert a i n s i n g l e , s p e c i f i c process. The f i n a l product of this treatment is water of d i f f e r e n t q u a l i t i e s which is s u i t a b l e f o r c e r t a i n s p e c i f i c technological processes. During the use of water i n contact With the product and a s a cooling and heat carrying medium, i t is possible t h a t carbonates, o t h e r s a l t s , gases and organic matters may separate. I n t h i s way water is used during catching, cooling and cleaning of gases, extinguishing of coke etc. a l s o i n the food industry. The q u a l i t y requirements i n t h i s g o u p a r e complex and should correspond not only t o the previous ones, but a l s o to the requirements f o r cooling and h e a t carrying

155 matter. These requirements, which a r e p e c u l i a r t o each production process,

have t o be determined s e p a r a t e l y . For the p h a m c e u t i c a l and food industry drinking water is used and addit i o n a l q u a l i t y requirements applied f o r i n order to safeguard the appropriate standard of these products (Tab. 2 . 2 4 ) . 2.5.2 Cooling \*later Cooling water, which accepts and removes the excess h e a t during i n d u s t r i a l production, forms some 60-80% of the water quantity needed i n industry. This water undergoes t h e m 1 changes and o f t e n requires thennal treatment, including a l l the processes of water warming, cooling, d i s t i l l i n g , mixing with vapour and degasifying. Cooling by water i n contact with the semi-finished product a s c o n t a c t cooling i s a p a r t of processing. TABLE 2.25

Losses through

Requirements of cooling

\*later consumption ( l o s s e s )

Type of losses

water (m3.s - l ) Oncethrough sys tems

Ae - ce

R

(m3.s-l

. (T2 - T1) . R

Ae = 0.001. (T2-T1+10) .R

0.241. J

Open circuit SYs tern

Ae =

0.002.(T2-T1+13) .R

evapora t i o n Leakage evapora t ion wind ( c m c eimDact ntration)

T2 - T1 spreading, leakage, mud discharge

Closed circuit sys tern

evaporation (concentration) 1eaka ge mud discharge

Ae = 0.01.R

Losses through

J

I. wind impact 11. spreading

T

AI-Iv

=

C~-~”.R

T

111. leakage

I V . mud discharge (sludge)

- heat -

1

diverted (J.S-’) water inflow temperature

2- water outflow temperature (OC)

R

- cooling water requirements

Water requirements and l o s s e s i n d i f f e r e n t cooling s y s t e m . Water requirements i n once-through systems are permanent, i n c i r c u i t systems once per operation cycle. Systems f o r cooling without any c o n t a c t with the product a r e l i k e o t h e r ind u s t r i a l water systems, namely

(a)

open c i r c u i t sys tems,

156 (b) r e c y c l i n g sys tern - open, when the h e a t is removed by the d i r e c t c o n t a c t of water and a i r , - c l o s e d , when the h e a t is removed without any d i r e c t c o n t a c t with a i r , i . e . i n a closed h e a t exchanger. Cooling i s needed e.8. i n steam and nuclear power p l a n t s , during vapour condensation, bearing and o i l cooling, a s well as f o r the i n d i r e c t cooling of gases and l i q u i d s , furnaces, k i l n s e t c .

Water requirements depend primarily on the technological process and i t s -1 temperature, i . e . on the q u a n t i t y of h e a t J (J.s ) t o be removed and, secondly on the type of cooling system (Tab. 2.25, 2.26). They a r e s u b s t a n t i a l l y lower i n r e c y c l i n g systems . Closed systems prevent evaporation, thus f u r t h e r decreasing both water consumption and water requirements. Between 80 and 400'C

air

cooling is more advantageous than water cooling. TABLE 2.26

Cooli n p sys tern

Evaporation losses a t the a i r temperature

'0 C

10' C

20'

C

Losses through wind impact

30' C

Cooling towers n a t u r a l draught

- with

0.001-0.003

0.0010 0.0012 0.0014 0.0015

o.oo5

Outdoor s p r i n k l e r s

0.0020 0.0024 0.0028 0.0030

0.015-0.020

Cooling ponds and tanks

0.0007 0.0009 0.0011 0.0013

- a i r blmers

0

Water loss c o e f f i c i e n t s through wind impact cI evaporation ce and t h e i r dependence on a i r temperature and type of the system. The q u a l i t y requirements f o r water used a s a cooling mediim without any con-

t a c t with the product a r e derived i n such a way a s t o ensure the s a f e and e f f i c i e n t operation of t h e system (Tab. 2.27). They may be low f o r open c i r c u i t systems and must be high f o r recycling systems, preventing e s p e c i a l l y t h e i r corrosion and clogging. The q u a l i t y requirements f o r water used i n h e a t exchangers should s a f e w r d i t s t h e m s t a b i l i t y , i.e. eliminate the growth of biorrass, the s e p a r a t i o n of carbonates and o t h e r s a l t s and gases, e t c . , even under cond i t i o n s of multiple cycles of warming and cooling (Tab. 2.23).

A cumulation of the f o l l m i n g suspended mtter occurs i n t h e recycled water: ( a ) c r y s t a l s of s a l t s , e s p e c i a l l y of calcium carbonate CaC03 which a r e d i f f i c u l t t o dissolve, (b)

t h e prcducts of corrosion,

(c) microorganism, (d)

d u s t and s o o t ( e s p e c i a l l y i n open systems).

157 Cooling water has t o be t r e a t e d mechanically hy f i l t r a t i o n , by a l k a l i n e c l a r i f i c a t i o n , by ion exchangers, o r m ~ e t i c a l l y ,i n o r d e r t o decrease the sedimentation, e s p e c i a l l y of the calriwn carbonate. The sedimentation r a t e j n a closed system is e s s e n t i a l l y lower than i n an open system. TARLE 2.27

Velocity of water

Permissible c o n c e n t r a t i o n of p o l l u t i o n

flow (m.s-l)

Continuously

(0.01 0.01-0.2 0.2-0.5

c 5

(me.1-l)

Short-term

< 20

- 20

50

30 - 50

100

10

Permissible c o n c e n t r a t i o n of p o l l u t i o n i n c o o l i n g water and i t s dependence on the c o o l i n g water f l m v e l o c i t y . For the treatment of water f o r c o o l i n g , i t is necessary t o remove organic components, which a r e a b l e t o form porous d e p o s i t s i n a warm environment, thus clogging t h e c r o s s p r o f i l e o f the p i p e l i n e system, i n c r e a s i n g t h e f l a g r a t e and decreasing i t s h e a t c o n d u c t i v i t y . I n the closed c i r c u i t r e c y c l i n g system i t is n o t necessary t o rernove the i n f e c t i o u s b a c t e r i a : t h i s i s only indispensable when the water comes i n t o d i r e c t c o n t a c t w i t h t h e product o r w i t h t h e s t a f f i n some i n d u s t r i a l branches, e s p e c i a l l y i n the food and pharmaceutical i n d u s t r i e s . B o i l i n g and Stream Power h'ater 2.5.3 Roiling water is used as a h e a t c a r r y i n g medium without any c o n t a c t with the and undergoes s i m i l a r changes a s c o o l i n g water. B c i l i n g mmter and steam d u r i n g processing, f o r h e a t i n g and v e n t i l a t i o n , f o r power g e n e r a t i o n , as warm service w a t e r . The temperature of water i n t h e supply network of warm water systems general l y depends on the energy i n p u t and o f t e n reaches 150OC. Temperatures not exceeding 100°C are a d m i s s i b l e i n networks whose o u t p u t does n o t exceed 1 . 7 G J per hour. IJam water f o r i n d u s t r i a l purposes is seldom supplied by t h e municipal supply s y s tem. ' h e water q u a l i t y requirements follcw

-

the decrease i n corrosion the decrease i n clogging. Corrosion is supported by f r e e CQ2,

low pH f a c t o r ( < 8 ) , iron Fe and copper

Cu c o n t e n t , and by a h i g h e r Oxygen c o n t e n t ( > 0,OZ mg 02. 1-l).

Clogging is

158 caused rrainly by CaC03, MgCQ3,

€i2Si03, sediments, organic colloids and o i l .

The quantity of water i n power generating systems is formed by feed water t o f i l l the system and supplementary water to cover water losses, caused especially by leakage and evaporation: Vo = R f + R s

Vo

-

-

/Ad,

n

volume of water i n the recycling system

Rf - feed water (for the f i r s t f i l l i n g up) Rs

-

A

- water

t

-

(m3

(m3 .s -1)

losses

(s)

time

-

(m')

<m3 )

supplementary water

After the f i r s t f i l l i n g of the system Vo Rs

(2.86)

(m3)

Jddt

=

Rf and, therefore, (2.87)

(m3)

Total water requirements, corresponding t o the water withdrawal, a r e W

= Rf

+

(2.88)

Rs

?he q u a l i t y requirements of the feed and supplementary water should also safeguard its t h e m s t a b i l i t y , limiting the content of suspended m t t e r , o i l and chemically aggressive components t o almost n i l . Such water should be c l e a r and without any colour. The t o t a l content of ions is limited t o 10-14 mn01.1-~, ions of calcium Ca2+ and t o t a l carbon dioxide C02 t o l e s s than 3 . 6

- 7.0

ml.l-'. h e r values correspond t o the density of the energy output above

23 kW.m-2 (Tab. 2.28). The content of gases and organic m t t e r i n condensed steam depends on the nominal pressure and on the thermal scheme of the system

-

i t exceeds the water

content. The feed water of these systems i s a mixture of the returned condensed steam and the supplementary water

.

Methods of t r e a t i n g the condensed steam include f i l t r a t i o n , demineraliza tion and deoxygenation. Steam treatment i n heating plants and pcwer plants often includes the softening and removal of organic matter and o i l . Steam systems have to be protected from the aggressivity of water by m i n t a i n i n g the protect i v e a l k a l i n i t y , which can be achieved by dosing s o l i d o r v o l a t i l e deoxigenation

or other agents. This protection can a l s o be achieved under a neutral regimen by the removal of corrosive gases, s a l t s and other aggressive p a r t i c l e s , i . e .

by the treatment of the condensed steam and by the demineralization of the supplementary water.

159 TABLE 2.28

W

bi C

"

X

m a r

\dater q u a l i t y indicator

0

!i

w

.r

i

rou0l.l

-1

fig.1-l

c2

15 15 50

50

15 1.5

50 500 100 20

Fe

mg. 1-1 pcg. 1-1

1 20

cu

f i g . 1-1

5

0.25 2.5 1 . 5 1 0.5 10 20 10 10 ZC 0.5 5 20 30 5 1

C k i d i z a b i l i t y CODFln'mg 02.1-l Swpended matter Specific e l e c t r i c a l conductivity S i02

103

9'

9'

13'

-

50

50

5 2 50

0.3

10' 0.5

ps cm-l &. 1-1

20

20

p-apparent a l k a l i n i t y rran0l1-l Surplus of P20 5 Oil

0.5 0.5 20 20

1 0 5 5 5 3 2

50

g.1-l

1 20

mg.1

-1

-1

mg. 1

6'

2.5' 0.6'0.3' 0.05-1.5 < 0.05 2-10

3

3

3

1-3 0.5-2 0.3-1

3

Water q u a l i t y i n d i c a t o r s f o r feed and b o i l e r water (+) depend on the type and o u t p u t of the thermal economic system. Heated water and steam form a medium which enables the transformation of chemical and nuclear energy i n t o e l e c t r i c a l energy i n thermal and nuclear p m e r p l a n t s . According t o Minasian e t a l . (1977), t h e water requirements reach

-

i n a t h e m 1 p w e r plant i n h e a t and power p l a n t s i n nuclear power p l a n t s

A t present 0.127

i n 2000 0.104 m3 .ldnl-l

0.101

O.C.50

rn3.k1h-'

0.200

0.125

m3 .kWh-l

The r a t i o of water consumption i n t h i s case reaches 0.01 t o 0.02. Davis and Wood (1974) estimate water consumption during power generation a t 10 km3yearly

"he water demand f o r t h i s purpose i n developed countries is gradually reaching

160 the water demand f o r i r r i g a t i o n . Rut the use of water for power generation purposes is not a s consumptive. Water Losses i n Industry and F l a g Chart of Water Ike

2.5.4

Because of the prevailing percentage of water used for cooling purposes, the prevailing losses of water i n industry a r e formed by Percentane of the volume of water used

(a)

evaporation

(b)

(c)

escape and spreading leakage and leaching

(d)

mud discharge

c(O/O)

(Ole)

5

1.5 X 0.L-0.8 % 1 - 2 % up to

87 6 5 4% 3.5 3%

6 %.

2.5%

ne

2 O/O

4

3

2 I

0I

1.8

02

2.6

3.4

Aes+

Fig. 2.16. I n t e r r e l a t i o n s of evaporation, spreading and wind action losses and of the concentration of s a l t s i n a water cooling system: e - evaporation, es - spreading and cscape, s - Sludge, c - concentration of s a l t s . The prevailing losses a r e those caused by evaporation. They depend not only on the type of the system and i t s equipment, but a l s o on the method of i t s operation. Minimum losses can be achieved i n closed recycling systems by uninterrup ted opera tion. Losses through evaporation and corrosion cause the concent r a t i o n of s a l t s which may exceed the relevant mximm permissible values i n the recycling system

(Fig. 2.16). This concentration is defined by the f o l l w

ing conceGtration r a t i o ( f o r a ccoling or s i m i l a r system)

fA i

c

=

9 i=l

j

A1

- losses

*2

-

losses throuFzh spreading

A3

-

evaporation losses

through escape

(2.89)

161 Losses through w a t e r escape may a r i s e i n open systems only when the a i r flow takes away droplets and carries them outside the cooling system. The value of this loss depends on the a i r flow r a t e , i , e . on the gradient of temperatures and the type of system. Losses through spreading a r i s e as a r e s u l t of the influence of wind, i . e . again i n open systems only. The value of t h i s loss depends on the construction of the spray cooler and on the velocity of the wind. I t s value is not constant and, therefore, cannot be replaced by an estimated average. Unproductive leakage m y not only a r i s e i n cooling systems, but a l s o in lagoons, oxidation ponds e t c . , i . e . a f t e r processing. They do not necessarily increase the relevant water requirement. Their values reach a maximum a f t e r the f i r s t f i l l i n g up of the reservoir and then gradually decrease due to clogging. Losses during water purification or waste water treatment a r e caused by using water as a medium f o r collecting waste material and sludge. They occur periodically o r permanently, depending on:

w

-

t

- the time period of t h e i r accumulation

N

=

m

the volume of removed waste material the moisture content of the waste m t e r i a l

N . w t 100

(m3 (%) (s)

(m3.s-')

.

(2.90)

Water consumption and mud discharge water i n a recycling system has to be replaced by supplementary water Rs

F,

- mud

U1-3-

3 -1)

discharge water, replaced f o r improving water q u a l i t y

(m .s

consunptive use by a product, by-product and by means of wastes

(m3.s-l)

The function of i n d u s t r i a l water supply and disposal systems using water i n contact or without any contact with the product can be analyzed by means of modelling. The model using water without any contact with the product includes e.g. a spray cooler, treatment plants f o r the recycled and feed water and f o r mud discharge. Inputs of such a model include (Fig. 2.17) feed (supplementary) water, characterized by

-

Ro

-

co

- concentration of d i s s o l w d - water temperature

To

discharge

(m3.s-l) solids

(mg.1-9 ("C)

162

-

l i q u i d and s o l i d p a r t i c l e s entering the system from the a i r characterized i n

the same way, Qa, ca, Ta -

t h e m 1 energy: J,

Jar . , J

(J)

~TARYWATEF

Fig. 2.17. Simple model of water usage i n industry with m e water recycling and one water re-use c i r c u i t , i l l u s t r a t i n g the balance of water q u a n t i t i e s , of the diluted and suspended r a t t e r and of the energy input and output. Inputs i n a system using water i n contact with the product include, i n addition to this, liquid and s o l i d p a r t i c l e s entering the system from the raw material and

-

semi-finished product (Qm, G, T ~ ) Outputs of a model of i n d u s t r i a l water supply and disposal system without any contact w i t h the product include:

-

waste water, characterized by

R8 - discharge

- concentration of dissolved T8 - water temperature c8

-

(m3, s-l) solids

(w.1-5 ("C 1

mud discharge (from the treatment of the recycled water, sludge treatment

etc.)

- water

-

losses through evaporation Ae, escape and spreadingAes losses of energy (e.g. by evaporation Je>

163 Outputs i n a system using water i n c o n t a c t with the product include, i n a d d i t i o n to t h i s ,

-

consumptive use u1 , IT2 , [I3. IJsing such a model, the balance (a) (b)

of the water q u a n t i t i e s (water d e l i v e r y , r e c y c l i n g and d i s p o s a l ) , of the d i l u t e d and suspended matter

( c ) of energy i n p u t and output can be analyzed i n d i f f e r e n t p a r t s of the system. (a) The volume o r discharge of t h e supplementary water can be determined on the b a s i s of the balance

(2.92)

(m3. s - l )

Apart from the supplementary water R1 the recycled water R7 and re-used water R

5

also e n t e r the subsystem, thus

The o u t f a l l from the i n d u s t r i a l water system is the waste water R

8

=

R3

- R5

(2.94)

(m3.8)

-Ao2

and mud discharge

N = A01.'01 (b)

+A02'c02

+

(2.95)

A03'C03

The chemical balance can be analyzed by equations of the following type

R2.c2 = R 3 .c3 + R 6' c 6 +

*. c i

+ Q,c,,

+

Qaca

(2.96)

The water q u a l i t y i n the system changes a s a r e s u l t of the i n p u t of energy and matter. I n the case of a cooling system (U = 0), the r a t e of d i s i n t e 112 ?3 g r a t i o n , caused by d i f f e r e n t chemical and biochemical processes r e s u l t i n g i n changes i n water q u a l i t y , depends on t h e discharge t o w l u n e r a t i o i n the cooling p l a n t . This can be expressed by a d i f f e r e n t i a l equation

(2.97) c.

-

concentration of t h e water q u a l i t y i n d i c a t o r i (mg.1 -1 )

V

-

volume of water i n the system

164 The r a t e of concentration changes i n the canponent i depends on the o r i g i n a l maximum concentration ci(o, a t the moment to (2.98)

The trouble-free operation of an i n d u s t r i a l water supply, and re-cycling and d i s p o s a l , system requires a s t a b l e water q u a l i t y , which should be m i n t a i n e d by - a s o p h i s t i c a t e d water recycling and re-use system

-

a p p r o p r i a t e d e l i v e r y of the supplementary water maintenance of water q u a l i t y by an appropriate dosage of relevant chemical

substances . The dose of the chemical substance to maintain i t s required concentration ( t o p r o t e c t the water supply and recycling system o r t o maintain the q u a l i t y required f o r processing) i s , t h e r e f o r e , (2.99)

The influence of water l o s s e s on water q u a l i t y d i f f e r s : evaporation losses change the concentration of most water q u a l i t y i n d i c a t o r s , while seepage, escape and spreading do n o t . To maintain the required water q u a l i t y , the necessary input of the supplementary water is t o be derived from evaporation losses

A,

and

t h e d i f f e r e n c e s i n the i n p u t and output concentration C,

R1 = Ae

3 . c -c

(2.100)

3 2

When the water treatment p l a n t of both the supplementary and the recycled water a r e a b l e t o maintain a constant water q u a l i t y , the changes i n concentrat i o n depend mainly on t h e evaporation r a t e and on the matter input from the

water re-use c i r c u i t . The q u a l i t y of water t h a t can be recycled depends on the permissible concentration of t h e suspended matter and on the e f f i c i e n c y of f i l t r a t i o n i n the treatment p l a n t of the recycled water. High e f f i c i e n c y of f i l t r a t i o n helps t o increase the r a t i o of the recycled water R

f 6 =

R3+4?s f

-

?2

(2.101)

e f f i c i e n c y of f i l t r a t i o n

( c ) The water temperature i n d i f f e r e n t p a r t s of the system and the temperat u r e of the waste water can be determined from d i f f e r e n t equations of the e n e r *tic balance, e.g.

165 J

n = J o + J p - X A J i + aJ + Jm 8 i=l

(2.102)

(J.S-')

Water recycling and re-use r e q u i r e higher funds to be a l l o c a t e d by the user f o r the investment, enabling him t o make savings i n operation c o s t s . The applic a t i o n of these technologies r e s u l t s i n a reduction of water withdrawals with a subsequent improvement of water balances and of the water q u a l i t y i n surface and groundwater resources. Was te Waters and Mas te-free Technologies 2.5.5 Idas te water which is discharged i n t o streams c o n s t i t u t e s an ever-increasing proportion of water supply. With regard t o the s e l f - p u r i f i c a t i o n and water treatment process, the r e l e v a n t waste p a r t i c l e s can be considered a s (a)

b i o l o g i c a l l y degradable,

(b)

b i o l o g i c a l l y undegradable.

I n e f f e c t , the contamination caused by i n d u s t r i a l waters can be categorized as ( a ) chemical - d i l u t e d and suspended chemicals, (b) b i o l o g i c a l - b a c t e r i a , viruses and o t h e r pathogenic organisms, ( c ) thermal. I n d u s t r i a l waste waters a r e generally mixed. The contamination is mostly t o x i c ; but the harmfulness OE the wastes depends not only on t h e i r t o x i c i t y , but a l s o on t h e i r a b i l i t y t o slow down o r t o s t o p t h e processes of s e l f - p u r i f i c a t i o n i n r i v e r s , o r of b i o l o g i c a l water treatment i n r e l e v a n t p l a n t s . TABLE 2.29

Waste water groups Cooling Mining and hydraulic transport

F_

Origin

S u i t a b i l i t y f o r r e - u s e and re-cyc 1ing

cooling systems

good, occasionally without s p e c i f i c

lagoons, s e t t l i n g tanks

good, simple treatment technologies

q u a l i t y depends on raw m a t e r i a l and technology applied

generally demanding treatment technologies : food.~.paper and pulp industry' waste waters s u i t a b l e f o r irrigation; possibilities for material recoven

F,LLL

Processing incl. rinsing 'F

P Sewage Other waste wa terS

F R Fb

1

not s u i t a b l e f o r i n d u s t r i a l re-use, suitable for irrigation feed,yter? precipitation

n o t s u i d b l e , a c c i d e n t a l occurrence, requires a c c m u l a t i o n

C l a s s i f i c a t i o n of i n d u s t r i a l waste waters with regard t o p o s s i b i l i t i e s of t h e i r re-use and re-cycling. See Fig. 2.15.

166 ?he p o s s i b i l i t i e s of waste water re--use o r recycling depend on the q u a l i t y of the waste waters concerned, i . e . on t h e i r o r i g i n and on the type of the ind u s t r i a l process (Tab. 2 . 2 9 ) . The o u t f a l l of the system is treated waste water: (m3.3) This quantity, o r p a r t of i t can be re-used,

(2.103)

thus decreasing the quantity of

waste waters discharged i n t o water resources (Fig. 2.15) :

FA

= Fo

.f? i = f Ai

- Rw

(2.104)

(x3.s-1)

Data on the chemical and biological composition of waste waters can be derived by an analysis of the relevant technological processes on the basis of the material balance. The degree of pollution of i n d u s t r i a l waste waters can be compared with domestic sewage by means of population equivalent values. The population equivalent value of i n d u s t r i a l pollution corresponds to the number of inhabitants producing pollution whose biological oxygen demand BOD has the same

5

value a s waste waters frcm the relevant i n d u s t r i a l production processes. This population equivalent value E can be r e l a t e d t o the d a i l y production o r to the production mi t :

3

E =

ROD5(g.m )

54 F:

.

3

Q(m )

(per u n i t of production, per day)

(2.105)

The sewerage system normally discharges d i f f e r e n t kinds of sewage water, or discharges d i f f e r e n t types of sewage waters separately. Nevertheless i t is necessary t o prevent the penetration of aggressive substances i n t o the sewerage system, o r to prevent the penetration of waters containing (a) matter which destroys sewerage s t r u c t u r e s or damages the materials of the sewerage system, (b)

m t t e r which causes breakdowns i n the waste water treatment processes.

(c) matter which is infectious, contaiminated, poisonous , narcotic o r radioa c t i v e t o such a degree t h a t i t threatens the health of the s t a f f i n the treatment plant or of the population, o r forms these substances i n admixture with waste waters from other processes

,

(d) explosive o r combustible substances, o r ccmpounds which form such substances with water o r a i r o r other substances which can penetrate i n t o the Sys tern , ( e ) substances with a n extremely offensive odour o r which cause such an odour i n admixture with waste waters from other production processes. These waters a r e a l s o n o t s u i t a b l e f o r re-use or recycling. The penetration of waste waters i n t o water resources leads to a d e t e r i o r a t i o n i n t h e i r q u a l i t y , a s w ~ l al s i n the qimlity of the o t h e r compounds of the biosphere.

167

Output data: Water withdrawals

w

Water consumption C

Final effluent F ( waste load N ) Waste water quality q, - q,

Water rates MI-Ms Penalties etc P4-P4

R,C,N,r- f 4 - 4 ( A , B , C,D, E , M I - 6 Investment and operation casts.

Fig. 2 . 1 8 . Block diagram f o r the determination of water requirements and m ~ g e ment of water deliveries as w e l l a s waste water disposal i n industry in accordance with the hierarchy of goals and the basic limitations. In order t o reduce the negative impact on future development, the u t i l i z a t i o n of water i n industry should be ratio&lized, especially by means of the f o l l o w ing wa ter-saving measures (Fig. 2.18) : (a) reducing water wastage, (b) limiting the duration of water u t i l i z a t i o n during technological processes to the absolute minimum,

(c) selecting processes which e n t a i l minimum water consunption and minimum Water pollution, (d) applying internal recycling and waste water re-we,

168

(e) decreasing the requirements on water quality t o the technologically permissible l i m i t and by using available resources of low quality, ( f ) using industrial waste waters i n other branches of the national economy, especially i n agriculture. A decrease i n the volume of wastes i n industrial production can be achieved bY

-

a change of technological processes, a change of product mix, enabling the u t i l i z a t i o n of waste material as raw

material f o r other products, - a reduction i n the weight of products - water recycling and waste water re-use,

-

using selected waste nlaterial a s f e r t i l i z e r s i n agriculture. Liquid, s o l i d and gazeous wastes a r e often suitable as raw material f o r other production processes,

for m t e r i a l reiovery, f o r s o i l regeneration, - for power generation. -

These problems a r e interdisciplinary, having an impact not only on water management, but a l s o on the biogeochemical cycles and the exhaustion of the natural resources. To moderate t h i s problem, the production processes should be gradually, as f a r as possible, incorporated i n t o natural biogeochemical cycles. Production processes which a r e aimed a t the maximum u t i l i z a t i o n of a l l raw materials on the one hand and a t the re-use of material products a f t e r t h e i r u t i l i z a t i o n on the other hand gradually lead t o waste-free technologies. Their introduction requires the variety of products and the system of t h e i r u t i l i z a tion t o be changed, i n order t o enable t h e i r return into the production cycle o r t h e i r unexceptional coalescence with the environment. This goal can partly be achieved by the higher service l i f e of products, i f t h e i r repair is economically feasible. The issue of energy consumption i s also interconnected with these problems, because power generation likewise leads t o the over-utilization

of available natural resources and t o environmental pollution (Fig. 2.19). The necessary reorganization of production can be achieved by grouping relevant production processes i n t o integrated schemes. I n such a way i t is possible t o apply continuous technologies , which may be financially less feasible, but r e s t r i c t the negative impact on the environment. But there are limits t o production concentration. A high concentration, even i n the case of a low production of wastes per product, causes such a high concentration of waste material and waste waters t h a t t h i s cannot be locally a d economically disposed of without harmful effects on the environment. The step-by-step introduction of waste-free technologies requires a systema-

169

Fig. 2.19. Schematic r e p r e s e n t a t i o n of t h e conventional n a t u r a l resourcesdemanding production and consumption process which leads t o accumulation of wastes (black arrows) and t o an excessive environmental p o l l u t i o n . IJnconventional waste-free technologies (hatched arrows) decrease t h e environmental p o l l u t i o n a n d t h e n a t u r a l resources exhaustion. t i c approach, which must consider a l l t h e s c i e n t i f i c , t e c h n i c a l , economic, s t r u c t i i r a l and s o c i a l a s p e c t s of human development: i n d u s t r i a l production, t r a n s p o r t and power g e n e r a t i o n , covering t h e sphere of a l l u s e r s : i n s h o r t , the everyday l i f e o f a l l i n h a b i t a n t s . The t r a n s i t i o n t o t h i s p r o s p e c t i v e technoloey

i s a n i n t e g r a t e d and gradual process aimed a t c l o s i n g the c i r c l e between t h e sphere of production and t h e sphere of u s e r s . 2.6

WATER I N AGRICULTITRAL SYSTENS

A g r i c u l t u r a l production is a r e s u l t of the f u n c t i o n of a g r i c u l t u r a l systems and has t o be managed w i t h i n t h e i r framework. An a g r i c u l t u r a l system can be defined as a s e t of interconnected s o i l and m i c r o b i o l o g i c a l , p l a n t , mechanical and human elements whose i n t e r a c t i o n produces o r g a n i c matter f o r t h e nourishment of man on t h e b a s i s of t h e supply of s o l a r , mechanical and human energy and matter i n c l u d i n g water, f e r t i l i z e r s and agrochemicals (Fig. 2.20). This system can also be expressed a s t h e i n t e r s e c t i o n of p l a n t ecosystems, t h e microbiolog i c a l system of s o i l and t h e l i v e s t o c k breeding a s w e l l a s agrochemical producing system AS = PE n MS n LA AS - a g r i c u l t u r a l system

(2.106)

170

PE - p l a n t ecosystems MS - microbiological system of s o i l

LA - l i v e s t o c k breeding and agrochemical producing system

VESTOC

Fig. 2.20. A g r i c u l t u r a l system, i t s environment and b a s i c i n t e r r e l a t i o n s h i p s of i t s subsystems (microbiological s o i l system, p l a n t ecosystem, l i v e s t o c k breeding system). Basic inputs (energy and labour, sediments and f a l l - o u t , f e r t i l i z e r s and p e s t i c i d e s ) and outputs ( p l a n t and a n i m l products, eroded and leached material).

The process of the accumulation and transformation of s o l a r , mechanical and human energy and matter takes place e s p e c i a l l y on t h e a c t i v e s u r f a c e of s o i l minerals, i n t h e i r microbiological communities, i n the r o o t s , stems, leaves and f r u i t s of p l a n t s and i n the d i g e s t i v e organs of l i v e s t o c k . Plant ecosystems transform s o l a r energy, water and nutriments i n t o organic matter. This p l a n t

matter, decomposed e s p e c i a l l y by t h e d i g e s t i v e organs of p o l y g a s t r i c l i v e s t o c k , is transformed i n t o mre complicated p r o t e i n s , sacharides and animal f a t . Waste matter which has not been incorporated i n t o t h e r e s u l t i n g animal matter contains mainly carbon and nitrogen. I t r e t u r n s i n t o t h e s o i l i n the form of manure, d u n p a t e r e t c . and i s subseqiiently transformed i n t o polymolecular rratter, o r humus, by t h e microbiological communities i n s o i l . This process regenerates t h e bioenergetic p o t e n t i a l of the s o i l , which depends on t h e e x t e n t of the a c t i v e surfaces and t h e s t r u c t u r e of the s o i l compo-

171 nents and may be c h a r a c t e r i z e d as

E = - t Y

(2.107)

XN I Y - dry wei&t o f y i e l d I N - weight of main n u t r i e n t s ( n i t r o g e n N , phosphorus P , potassium K)

(t) (t)

The s t a b i l i t y o f t h e a g r i c u l t u r a l system and t h e permanent course of t h e a g r i c u l t u r a l prodiiction process depend on t h e equilibrium of t h e r e l e v a n t s o i l , p l a n t and animal subsystems and on t h e equilibrium of t h e a g r i c u l t u r a l system and i t s environment w i t h i n t h e framework of t h e n a t u r a l hiogeochernical cycles: Basic i n p u t f a c t o r s , i . e . energy, water and l a b o u r , must safeguard a permanent and s u f f i c i e n t supply of r e l e v a n t matter from one subsystem t o another. I n the case of an i n s u f f i c i m t o r i n t e r r u p t e d supply, t h e system becomes u n s t a b l e and can e n t e r a n u n c o n t r o l l a b l e s t a t e .

Two o f t h e e x i s t i n g feedbacks i n an a g r i c u l t u r a l system a r e p a r t i c u l a r l y important and r e g e n e r a t e t h e b i o e n e r g e t i c p o t e n t i a l E PE

-

(2.108)

MS

(2.109)

IA-MS-PE-IA

The a g r i c u l t u r a l production gradually t a k e s away, f o r t h e sake o f hunlan s o c i e t y , a c e r t a i n a m u n t of m a t t e r i n t h e form of p l a n t and animal products, thus destroyinq t h e n a t u r a l balance. Where t h i s production i s very i n t e n s e , t h e missing matter is not s u f f i c i e n t l y replaced by the biogeochemical c y c l e s . It h a s , t h e r e f o r e , t o be replaced a r t i f i c i a l l y , by means o f f e r t i l i z e r s and i r r i g a tion.

A p o s i t i v e biogeochemical development o f t h e t e r r i t o r y sets i n whenever the functions of t h e a p - i c d t u r a l system g r a d u a l l y b r i n g mre and more m a t t e r i n t o the hiogeochernical c y c l e s . This p r o c e s s , which r e s u l t s i n a n extension of t h e b i o l o g i c a l p r o d u c t i v i t y of t h e t e r r i t o r y , can be achieved (a)

extensively

-

by t h e extension of a g r i c u l t u r a l l a n d ,

(b) i n t e n s i v e l y - by t h e i n t e n s i f i c a t i o n of t h e a g r i c u l t u r a l and agroi n d u s t r i a l p r o c e s s e s , i . e . by a n increased i n p u t of energy and m a t t e r , e s p e c i a l l y

water, f e r t i l i z e r s and forage. A g r i c u l t u r a l water requirements a r e frequently s a t i s f i e d by a combination of on-site and e x t e r n a l s u p p l i e s . The r e g u l a t i n g f u n c t i o n of water has t o be achieved by a n e x t e r n a l w a t e r supply f o r (a) (b)

r e g u l a t i n g t h e s o i l moisture by means of i r r i g a t i o n and drainage,

(c)

f i s h and w a t e r p o u l t r y breeding,

l i v e s t o c k and p o u l t r y breeding,

172 td)

p r o c e s s i n g , b o i l i n g , c o o l i n g , h e a t i n g , waste d i s p o s a l ,

(e)

p u b l i c uses i n a g r i c u l t u r a l s e t t l e m e n t s .

A g r i c u l t u r a l Production and A g r i c u l t u r a l Y i e l d 2.6.1 The subsystem of t h e l i t h o s p h e r e and atmosphere where p l a n t prodiiction takes p l a c e includes (a)

2 - 4m deep and, e x c e p t i o n a l l y , deepcr s o i l l a y e r with t h e r o o t svsteni

and microbiolopical communities, ( b ) 2 - 6rn high and, e x c e p t i o n a l l y , h i g h e r l a y e r of t h e atmosphere containi n g t h e upper p a r t of t h e p l a n t s . Present-day a g r i c u l t u r a l production i s becoming a m r e and iinre complicatpd process with i n d u s t r i a l c h a r a c t e r , which h a s , i n t e r a l i a f o r economic reasons, to t a k e rnaxinium advantag? of n a t u r a l f a c t o r s and must n o t be allowed t o adversely a f f e c t t h e environment. The a g r i c u l t t i r a l y i e l d i n a given a r e a is a function of eight factors

Y =

Y - yield

s -

s o i l t y p e , i t s t e x t u r e and s t r u c t u r s , i t s water holdinE capacity ( r p l a t i v e ly stable)

w - weather,

siipply of energy and water ( v a r i a b l e , c o n t r o l l a b l e onlv i n hot-

houses)

c -

q u a l i t y and s u i t a b i l i t y of p l a n t s and t h e i r seeds ( c o n t r o l l a b l e i n advance’,

F - q u a l i t y and s u i t a b i l i t y of f e r t i l i z e r s ( c o n t r o l l a b l e i n advance) M - machinery and i t s proper i i t i l i z a t i o n ( o p e r a t i v e l y controllable’,

H - human labour ( o p e r a t i v e l v c o n t r o l l a b l e ) 0

- water supply and i t s a p p r o p r i a t e timing, water q u a l i t y and a p p r o p r i a t e irrigation practices. Veather and s o i l , s t a b l e w i t h i n the framework o f crop r o t a t i o n c y c l e s , a r e

key f a c t o r s i n t h i s equation. The o t h e r f a c t o r s , e s p e c i a l l y t h e s e c o n t r o l l a b l e i n advance, have t o be adapted t o t h e i r c h a r a c t e r i s t i c s . Operatively c o n t r o l l a b l e f a c t o r s have t o be nunaged with p a r t i c u l a r regard t o t h e weather, which is a v a r i a b l e and u n c o n t r o l l a b l e f a c t o r . The e x p l o i t a t i o n of s o i l and water demand c l o s e l y depends on both these key f a c t o r s . F e r t i l e s o i l s g e n e r a l l y have h i g h e r water requirements per h e c t a r e of l a n d , p e r m i t t i n g h i g h e r s p e c i f i c y i e l d s t o be achieved ( t p e r h e c t a r e ) . T h e i r s p e c i f i c water demand p e r u n i t of product (m 3 p e r t ) i s , t h e r e f o r e , a b s o l u t e l y lower. These s o i l s permit t h e achievement of h i g h e r y i e l d s with a lower dose of f e r t i l i z e r s (Fig. 2 . 2 1 ) . IJnder t h e conditions of a wanner c l i m a t e , evapotransp i r a t i o n i s more i n t e n s i v e due t o t h e h i g h e r i n p u t of s o l a r energy. R e s u l t i n g y i e l d s a r e h i g h e r a s f a r as r e l e v a n t h i g h e r water requirements a r e s a t i s f i e d .

173

yield

r

I

I

I

I

90

150

1

( t . ha’)

I

0

30

1

210

(kg)N

Fig. 2.21. I n t e r r e l a t i o n s of y i e l d , s o i l q u a l i t y and t h e q u a n t i t y of f e r t i l i z e r s according t o RuliCek ( 1 976) : h i g h e r y i e l d s are achieved by lower f e r t i l i z i n g r a t e s under b e t t e r s o i l c o n d i t i o n s (a - medium q u a l i t y s o i l , b - high q u a l i t y s o i l ) . An i n c r e a s e i n f e r t i l i z i n g r a t e s above t h e optimum value increases water resources contamination, thus reducinp both t h e y i e l d and economic e f f i c i e n c y . Tne water requirements Ra of p l a n t s a r e p r i m a r i l y c o n t r o l l e d by t h e p r e v a i l ing weather and a l s o depend on t h e s o i l conditions when water supply is iinlimited. T r a n s p i r a t i o n i s p r o p o r t i o n a l t o r a d i a t i c n and can be q u a n t i t a t i v e l y a s s e s s e d from t h e r e l e v a n t weather elements. The w a t e r requirements Ra c o n s i s t - of t h e t r a n s p i r a t i o n T of t h e p h y s i o l o g i c a l l y a c t i v e p l a n t and

- of t h e evaporation E R~ k

=

T

+ E

-ke.

from t h e a d j o i n i n g s o i l s u r f a c e T

(m3. ha-’ )

(2.111)

- s o i l q u a l i t y c o e f f i c i e n t , a l s o depending on a g r i c u l t u r a l p r a c t i c e s , overshadowing, the presence of weeds, g e n e r a l l y ke = 1.2 - 1.5. The growth of p l a n t s i n terms of n e t a s s i m i l a t i o n or dry-matter increment,

a l s o depends on t h e energy i n p u t , b u t does n o t commence u n t i l r a d i a t i o n reaches a c e r t a i n minimum i n t e n s i t y . I t reaches a maximum rate a t moderate r a d i a t i o n i n t e n s i t i e s , i n c r e a s i n g only a l i t t l e a t high i n t e n s i t i e s . Y e t y i e l d does n o t only depend on a s u f f i c i m t and adequate supply of energv

and w a t e r , b u t a l s o on a s u f f i c i e n t supply o f a i r t o t h e r o o t zone. This f a c t

i s expressed by t h e i n t e r p l a y of t h e f a c t o r s S - s o i l q u a l i t y and Q - water supply - of t h e v i e l d equation (Eq. 2.110). llnder e f f i c i e n t a g r i c u l t u r a l pract i c e s the amount o f water slipplied corresponds t o t h e a c t u a l e v a p o t r a n s p i r a t i o n ; l o s s e s are n e g l i g i b l e . Water consumption i s alrnos t equal t o water requirements. I r r i g a t i o n is an i n h e r e n t l y consumptive w e , l a r g e l y reducing t h e p o s s i b i l i t i e s f o r t h e m u l t i p l e u t i l i z a t i o n o f water. Maximum y i e l d s can be achieved under s o i l moisture conditions of t h e f i e l d c a p a c i t y FC. When t h e value of humidity i s h i g h e r , t h e a e r a t i o n i s i n s u f f i c i e n t . I n heavy s o i l s , t h e a e r a t i o n i s a l r e a d y i n s u f f i c i e n t i n t h e conditions of t h e

174 f i e l d capacitv, thirs decreasing y i e l d s considerably. The s i z e of the pores is too small t o enable the necessary degree of a e r a t i o n . Light s o i l s a r e f a r more t o l e r a n t t o an increase i n s o i l humidity above t h e limits of the f i e l d capacity. The s i z e of the pores enables a s u f f i c i e n t supply of both water and a i r (Fig. 2.22). yield ( t . ha’)

I

3

2

4

Fig. 2 . 2 2 . I n t e r r e l a t i o n s of y i e l d , s o i l humidity (expressed a s the s u c t i o n pres s u r e pF), and s o i l type according t o Kutilek (1963): ( a ) sandy s o i l s form b e t t e r conditions f o r achieving higher y i e l d s a t lower s o i l humidity due t o the b e t t e r a e r a t i o n , i . e . t h e same y i e l d i s achieved with lower water requirements. - Ib) heavy clayey s o i l s . The maintenance of t h e moisture capacity between t h e l i m i t s of t h e f i e l d capacity under t h e v a r i a b l e conditions oE weather e s p e c i a l l y of uneven precipit a t i o n and evaporation, has t o be achieved not only by i r r i g a t i o n , but a l s o by drainage. Yields depend on the maintenance of adequate s o i l moisture l e v e l s duri n g the various s t a g e s of p l a n t growth. The water requirements of p l a n t s depend ( a ) on the i n t e r p l a y of the t r a n s p i r a t i o n r a t e and the supply of water from the root zone, i . e . on t h e r e s i s t a n c e of the p l a n t body t o the penetration of water from t h e s o i l t o the atmosphere, f b ) on the a c c e s s i b i l i t y of t h e s o i l p r o f i l e t o water, depending on the development o f the r o o t system, f c ) on t h e evapotranspiration r a t e , depending on weather conditions. The water reqi;irements of p l a n t s R,

and t h e i r consumptivr! use T I a r e a com-

bined function Ra = lJa

=

f (S

,

C

, A , IJ)

3 -1 (m .s )

(2.112)

S

-

C

- p l a n t type: morphology of l e a v e s , stem, r o o t zones etc.

A

- a g r i c u l t u r a l and i r r i g a t i o n p r a c t i c e s (see Eq. 2.110 - M, H, Q) - weather conditions ( s o l a r r a d i a t i o n , temperature, wind e t c . ) .

W

s o i l type, i t s t e x t u r e and s t r u c t u r e , i t s w a t e r h o l d i n g capacity

175 The a c t u a l water requirements of p l a n t s depend on weather: on the v a r i a b l e energy input o r output from the atmosphere. water and s o i l , i . e . mainly on the i n t e n s i t y of t h e s u n l i g h t , but a l s o on t h e i r r i g a t i o n water temperature, a i r hinriidity and wind v e l o c i t y . Their c h a r a c t e r i s t i c course shows a maximum during the sumner months i n a l l t h e c l i m a t i c zones of t h e northern hemisphere. A s t r a n s p i r a t i o n a f t e r sowing i s almost n i l , water requirements cover evaporation from the s o i l s u r f a c e i n o r d e r t o maintain s u f f i c i e n t s o i l moisture. I n the next period t r a n s p i r a t i o n i n c r e a s e s , reacliinp a maximum s h o r t l y before t h e period of maximum growth (Fig. 2 . 2 3 ) . mm monthly 125

evaporation

100

50

I

' I

' 2

'

I

3 ' 4 ' 5 ' 6

I

I

9 ' 1 0 '11 ' 1 2

7 ' 8

months

Fig. 2.23. Representation of t h e evapotranspiration of an annual p l a n t . The a c t u a l evapotranspirationET, approaches t h e value of t h e p o t e n t i a l evapotransp i r a t i o n ETp i n t h e period of maturing: FC - f i e l d capacity, WP - w i l t i n g point. Water is t h e r e g u l a t i n g f a c t o r of e n e r g e t i c processes during t h e t r a n s f o m t i o n of the organic matter i n a g r i c u l t u r a l systems. These e n e r g e t i c processes a r e c o n t r o l l e d by thermodynamic laws.

The expected y i e l d of the dry mtter can

be derived from t h e c h a r a c t e r i s t i c s of the change of t h e i n t e r n a l energy y

y

*n

hn

(7 - -Fi-

=

)

.

(2.113)

ymx

T - temperature t o t a l i n t h e r e l e v a n t period n T - temperature t o t a l during t h e y e a r of t h e maximum y i e l d

(OC)

(O)

hn

-

p r e c i p i t a t i o n i n t h e r e l e v a n t period

(m>

h

-

p r e c i p i t a t i o n t o t a l during t h e y e a r of t h e maximum y i e l d

(m)

-

( t ha-'

YmX

long-term maximum y i e l d of the dry

.

/ year)

matter The course of t h e change of t h e i n t e r n a l energy i s c h a r a c t e r i s t i c f o r t h e periods of growth and t h e p l a n t s i n question. Thermodynamic curves l i m i t t h e

176 c r i t i c a l periods i n which the lack of w a t e r considerably d e c r e a s s the y i e l d s . D i f f e r e n t p l a n t s require d i f f e r e n t amounts of s o i l moisture i n d i f f e r e n t periods of growth and seasons of t h e y e a r . They show a p r e f e r e n c e f o r a p a r t i c u l a r s o i l t e x t u r e , s t r u c t u r e and o t h e r p h y s i c a l c o n d i t i o n s . Some p l a n t s t h r i v e on well-drained s o i l , coarse-textured and w i t h a poor water-holding c a p a c i t y . Others show b e t t e r development i n more f i n e l y textured s o i l , with a h i g h e r d e r ree of moisture. The r o o t system of p l a n t s p e c i e s i s adapted t o a c c e p t

-

t h e r a i n from t h e s u r f a c e (shallow, dense, v a s t r o o t system)

-

the s o i l water

-

t h e groundwater (deep-rooted s p e c i e s ,

phreatophytes)

The arrangement and t h e d e n s i t y o f t h e r o o t system v a r i e s from s p e c i e s t o s p e c i e s . A r e l a t i o n s h i p between root systems and t h e water regime can be traced: s p e c i e s which prosper i n r a i n f a l l

may have a comparatively poor and shallow

system, while s p e c i e s i n a n a r e a where t h e r a i n f a l l does n o t p e n e t r a t e t o a g r e a t e r depth have a v a s t s u r f a c e system, Other s p e c i e s develop two t o t h r e e r o o t systems, which are s u p p l i e d fron! r a i n f a l l , groundwater and t h e s o i l moist u r e . The r o o t depth of one s i n g l e s p e c i e s dependson t h e s t r u c t u r e and depth of t h e s o i l p r o f i l e and i s influenced by t h e moisture conditions and groundwater t a b l e , which a r e interconnected with t h e c l i m a t e . I n deep well-drained s o i l s i n himid c o u n t r i e s p l a n t s a r e a b l e to accept water from a depth ranging from 0.3 t o 1 . 8 m , depending on t h e p a r t i c u l a r species and l o c a l c o n d i t i o n s . 'Re r o o t depth of semi-arid t o a r i d a r e a s exceeds t h e r o o t depth i n humid a r e a s by up t o two times. Seeds and s e e d l i n g s a r e a b l e t o accept water from t h e i r proximity o n l y . With t h e development o f t h e p l a n t , the r o o t s p e n e t r a t e i n t o deeper l a y e r s and spread h o r i z o n t a l l y .

A decrease i n the groundwater t a b l e has a n important e f f e c t on t h e y i e l d i n the case o f l i g h t and medium s o i l s . IJnder conditions o f heavy s o i l s , t h i s influence i s n o t s o s u b s t a n t i a l (Fig. 2 . 2 4 ) . R u t heavy soils do n o t allow a s u f f i c i e n t water supply i n dry seasons - y i e l d s a r e then considerably a f f e c t e d by weather c o n d i t i o n s . Light s o i l s , r e q u i r i n g high water t a b l e s , because of t h e i r low c a p i l l a r y r i s e , do n o t allow t h e necessary development o f t h e r o o t system. A decrease i n t h e water t a b l e under conditions o f a shallow r o o t system r e s t r i c t s y i e l d s because of the l a c k of water, w h i l e an i n c r e a s e has t h e same impact because o f the l a c k of a i r . Yields cannot be expected when t h e upper s o i l l a y e r , whose depth is 0 . 1 m i n t h e case of l i g h t and 0.4 m i n t h e case of heavy s o i l s , i s completely wetted because of t h e lack o f a i r i n t h e r o o t zone. I t is r a r e f o r a n uninterrupted supply of s o i l moisture from groundwater t o occur. Rut when t h e c a p i l l a r y r i s e and t h e s u c t i o n p r e s s u r e ensure an adequate supply of groundwater even i n dry p e r i o d s , n o t l i m i t i n g a s u f f i c i e n t supply o f a i r , t h e groundwater t a b l e is i n

177 the optimum p o s i t i o n f o r t h e s p e c i e s o f p l a n t i n q u e s t i o n t o achieve t h e rraximum y i e l d s . To achieve h i g h e r y i e l d s under t h e s e c o n d i t i o n s , t h e f l u c t u a t i o n of t h e groundwater t a b l e must b e r e s t r i c t e d ( F i g . 2 . 2 4 ) .

yield I00 O/O e

d 60°/0

2 0O/O 0.40

0.80

1.20

1.40

1.80

2.20 m

Fig. 2.24. I n t e r r e l a t i o n g h i p of y i e l d , s o i l q u a l i t y and depth of groundwater t a b l e according to Renetin (1963): a - sand, b - sandy loam, c - loamy c l a y , d - clayey loam, e - c l a y . A f a l l i n t h e groundwater t a b l e has a g r e a t e r e f f e c t on y i e l d from s o i l s w i t h lower c a p i l l a r i t y . A t t h e same l o c a t i o n , c h a r a c t e r i z e d by t h e s o i l q u a l i t y , t h e weather condit i o n s , t h e s i t i t a b i l i t y of p l a n t s and t h e q u a l i t y of seeds t h e r e l a t i o n s h i p between t h e water supply and t h e y i e l d can be expressed under s i m p l i f i e d condit i o n s , n o t t a k i n g i n t o account a g r i c u l t u r a l p r a c t i c e s i n c l u d h g t h e s u i t a b i l i t y , q u a l i t y and q u a n t i t y o f f e r t i l i z e r s , a s follows: Y

=

f

rn)

Y

- yield

D

- water d e l i v e r y ( n a t u r a l and a r t i f i c i a l ) and i t s timing

( t .ha-’ )

(2.114)

3 -1 (m .ha )

The course of t h i s f u n c t i o n !Fig. 2 . 2 5 ) proves t h a t maximum y i e l d s can only be achieved with an optimum water supply. A decrease below o r an i n c r e a s e above t h i s o p t i m m v a l u e c u t s y i e l d s . m e r i n g t h e water supply below t h e mentioned optimum v a l u e can i n c r e a s e t h e c o s t - b e n e f i t r a t i o , i . e . t h e f i n a n c i a l o r t h e economic y i e l d . Taking i n t o account economic reasons, i t i s necessary t o mention t h a t a long term oversupply of abundant water n o t only causes economic l o s s e s , but a l s o t h e gradual degradation of t h e s o i l l a y e r . IJnder t h e s e s i m p l i f i e d c o n d i t i o n s , f o r t h e purpose of water balances compilat i o n o n l y , t o t a l water requirements can be derived d i r e c t l y from the y i e l d R a = me ’ Y

(m3.ha-’)

m

- c o e f f i c i e n t of water requirements

(m3. t-’)(Tab.

Y

-

( t ha-1)

total yield

.

(2.115) 2.29)

178

yield

ha'

1.

water deliveries ( m3. h i ' 1 reduction in area

R~GIME

reduction unrestricted no in irrigation rdgirne more water rates needed

A

B

C

0

Fig. 2.25. I n t e r r e l a t i o n s h i p o f t h e y i e l d and t h e adequacy of the water d e l i very. The decrease i n water d e l i v e r y below minimum water requirements r e s u l t s i n no y i e l d . Regime: A - reduction of t h e area i r r i g a t e d , R - reduction i n i r r i g a t i o n r a t e s , C - u n r e s t r i c t e d regime, D - no mre water need+. Symbols: Y ,, - maximum y i e l d , Ymin - minimum y i e l d , ET - optimum evapo?P t - optimum water d e l i v e r y , - minimum (unavoidable) transpiration, D OP t water requirements. The c o e f f i c i e n t of water requirements depends on c l i m a t i c f a c t o r s . The equation was adapted f o r p r a c t i c a l a p p l i c a t i o n and c o e f f i c i e n t s derived e . g . Cherkasow (1950) (Tab. 2.30) Ra

k

t

=

-

0.1

. me . kt . Ye

3

y

c o e f f i c i e n t of t r a n s p i r a t i o n

(m3.ha-')

(2.116)

.

( 1 kg-')

ye - c o e f f i c i e n t of y i e l d Under the same c l i m a t i c conditions the transpiration/assimilation r a t i o of d i f f e r e n t s p e c i e s v a r i e s considerably. Some species a r e more e f f i c i e n t producers of dry matter than o t h e r s , with t h e same expenditure of water. This d i f f e r e n c e depends on t h e given morphological c h a r a c t e r i s t i c s , e.g. on the l e a f , stem and r o o t arrangement. As was shown above, t h e r a t e of t h e physiological processes, i.e. the trans-

piration/assimilation/production processes depends mainly on the supply of energy and moisture, and on the wind speed. Rut i t a l s o depends on the duration

179 TABLE 2.30

Prcduc ts

Coefficients k t (1.kg-’)

Yield Ye

mecd.kg-l)

Y(t.ha-])

Cereals : wheat

271-639

2.14

0.8-1.1

3 - 6

rye

431-634

2.25

0.8-1.1

3 - 6

barley oats

404-664 432-87 6

1.77 1.35

3 - 6 3 - 6

co rns

239-495

1.28

0.8-1 .1 0.8-1.1 0.7

5 - 8

Root crops: sugar b e e t

304-377

0.35

0.8-0.9

PO t a toes

285-575

0.25

0.8-1.0

50-90 40-80

Vegetables: Cucumbers

713

0.08

1.2-1.3

30-70

Tom toes

500- 650 250-600

0.10 0.15

1 .o-1.2

30-60 40-90

Cabbage

0 7-1.0

Table of transpi r a t i o n c o e f f i c i e n t s k t , y i e l d c o e f f i c i e n t s ye, water requirement c o e f f i c i e n t s me according t o Cherkasow (1950) and r e l e v a n t y i e l d depending i n a d d i t i o n on s o i l q u a l i t y , f e r t i l i z i n g and adequate s o l a r r a d i a t i o n . of t h e d a y l i g h t . The course of water requirements can, t h e r e f o r e , be derived from astronomic and meteorological f a c t o r s . The Hargraeves (1955) formula is based on an optimum s i m p l i f i c a t i o n of i n t e r n a l p l a n t and external environmental factors: R

opt

=

45.?

.

k

.

d

.T .

(0.38 - 0.0038 h )

(m)

k

- monthly consumptive-use c o e f f i c i e n t

d

- nonthly daytime c o e f f i c i e n t dependent upon l a t i t u d e

T - mean monthly temperature i n

(2.117)

OC

h - mean monthly r e l a t i v e humidity a t noon i n p e r cent (Tab. 2.31). To achieve optimum crop y i e l d s

( a > i n c l i m a t i c conditions, where t h e r e l e v a n t p l a n t s can be c u l t i v a t e d without a r t i f i c i a l watering, i r r i g a t i o n supplements t h e n a t u r a l water supply, ( b ) i n adverse c l i m a t i c conditions, where p l a n t s cannot be c u l t i v a t e d without an a r t i f i c i a l water supply, i r r i g a t i o n safeguards the undisturbed growth of p l a n t s . Under such conditions, i r r i g a t i o n r a t e s should be adequate t o achieve a t l e a s t minimum y i e l d s . I f t h e water q u a l i t y a v a i l a b l e i s n o t s u f f i c i e n t t o cover these minimum requirements, i t is vital t o reduce t h e e x t e n t of the a r e a irrigated.

180 TAULE 2.31

Consumptive use c o e f f i c i e n t s

3

Crop /Mon t h

4

5

6

7

0.11 0.25 0.29 0.33 0.31 0.41 0.70 0.64 0.67 0.74 0.12 0.38 0.32 1.34 1.42 1.40

Pasture Alfalfa Corn

Rice

8

9

10

0.32 0.67 0.42 I .44

0.32 0.64 0.26 0.51

0.22 0.40

11 Seasonal 0.14 0.41

0.10

0.55 0.72 0.73 0.62 0.28 0.45 0.30 0.31 0.28

Potatoes e a r l y Onions e a r l y Carrots

0.16 0.28

Peas

0.18 0.36

0.19

0.49

Reans Tom toes

0.52 0.31

0.66 0.32

0.64

0.28

0.15 0.28

0.66 0.71

0.51

0.33 0.36 0.40

0.67

0.58

0.81 0.19 0.27 0.36 0.15 0.10 0.03 0.25 0.51 0.17 0.34 0.34 0.50 0.48 0.32 0.42 0.48 0.24 0.22 0.45 0.43 0.46 0.51 0.51 0.38 0.60 0.41 0.41 0.69 0.15 0.18

0.32 0.55 0.87

Sugar b e e t s Ida ter melons Prunes Peaches

0.25 0.41 0.26 1.07

0.36 0.27 0.37 0.44

Monthly daytime c o e f f i c i e n t s Nlatitude

'5 25' 50'

1

2

1.01 0.91 0.91 0.86 0.72 0.76

3

4

1.02

5

0.99 1.03 1.01 1.03 1.12 0.99 1.11 1.28

6

7

1.03 1.11 1.13 1.32 1.32 1.00

1.0

11

12

1.03 0.98 1.02 1.09 1.00 0.97 1.20 1.01 0.89

0.98 0.89 0.73

1.00

8

9

0.89 0.68

Consumptive use c o e f f i c i e n t s a t Davis, C a l i f o r n i a and monthly daytime coeffic i e n t s i n the Hargreaves (1955) equation f o r the determination of t h e p o t e n t i a l evapotranspiration.

The a c t u a l water requirements depend on the f i e l d conditions, which change with the weather conditions. A p l a n t requires d i f f e r e n t q u a n t i t i e s of s o i l moist u r e , depending on t h e species and the s o i l , during i t s d i f f e r e n t stages of growth. Maximum t r a n s p i r a t i o n r a t e s appear i n a developing crop before assimilat i o n has reached i t s peak. The a c t u a l problems of how t o supplement these requiranents by i r r i g a t i o n and of how t o overcome adverse c l i m a t i c , s o i l and water conditions should be worked o u t on t h e t a s k of d a i l y measurements i n the course of t h e i r r i g a t i o n season.

181

Basic decisions include

-

amount of water required t o moisten the desired depth of s o i l (not smaller

and n o t g r e a t e r ) - a p p r o p r i a t e method and timing of i r r i g a t i o n ( a l s o t o reduce evaporation and percolation losses) - the coordination of o t h e r a g r i c u l t u r a l treatment processes w i t h the i r r i g a t i o n method and t h e timing of r a t i o n s .

2.6.2 Efficiency of I r r i g a t i o n Water IJse The e f f i c i e n c y of i r r i g a t i o n water u t i l i z a t i o n i s presently t h e key problem of water vanagemen t , because ( a ) i r r i g a t i o n water forms the main element i n water requirements on a global s c a l e . The e x t e n t of both t h e i r r i g a t e d land and the i r r i g a t i o n i n t e n s i t y

is increasing because of t h e increasing demand f o r food, caused p a r t l y by the world population boom and p a r t l y by improving l i v i n g standards; (b) i r r i g a t i o n i s an inherently consumptive use which considerably reduces the p o s s i b i l i t y of f u r t h e r re-use o r recycling; i r r i g a t i o n networks and t h e i r supply systems have a s u b s t a n t i a l and

(c)

l a s t i n g impact on t h e n a t u r a l environment. The economy of i r r i g a t i o n i s characterized by the r a t i o of t h e water withdrawal and t h e market u n i t , i . e .

wi l 1 = Y-Yo Y

- y i e l d under conditions of i r r i g a t i o n

Y

-

'

( t . ha-')

y i e l d under t h e same conditions, but without i r r i g a t i o n

Idi - water withdrawal f o r i r r i g a t i o n purposes

(m 3 .ha-'

per y e a r )

From t h e p o i n t of view of t h e p o p u l a t i o n ' s nourishment t h i s economy can be expressed by the r a t i o of t h e water withdrawal and the n u t r i t i v e value of the product

i'

=

I

I . (Y - Yo>

- n u t r i t i v e value of 1 t of t h e produced plant

(m 3 .J-1 )

(2.119)

(J.t-')

The b e n e f i t s of a l l investments i n i r r i g a t i o n p r o j e c t s depend on proper

water use i n t h e f i e l d i n conjunction with o t h e r a g r i c u l t u r a l inputs and cultur a l practices.

182

The planning and d e s i m of water development p r o j e c t s i n a g r i c u l t u r e should t h e r e f o r e be based on a water-use concept and should r e f l e c t t h e planned developnent of a g r i c u l t u r e r e s u l t i n g from t h e need f o r a f u r t h e r i n t e n s i f i c a t i o n and d i v e r s i f i c a t i o n of production, and t h e r e s u l t i n g changes i n a g r i c u l t u r a l practices.

Hulrar. s o c i e t y can determine only two o u t of t h e f o u r i n p u t v a r i a b l e s of t h e equation 3.112 namely: C - p l a n t s (seeds’ and

A - a g r i c u l t u r a l and i r r i g a t i o n

p r a c t i c e s . Hor.:ever, the nlutual r e l . a t i o n s h i p o f t h e s e v a r i a b l e s i s complex and can be solved r e l i a b l v enough on t h e b a s i s of system a n a l y s i s alone. This corn p l e x r e l a t i o n s h i p i s o f t e n n o t r e f l e c t e d by c u r r e n t p r a c t i c e . The s t r u c t u r e of a g r i c u l t u r a l systems and crop p a t t e m s is o f t e n s t i l l t h e r e s u l t of

-

t h e t r a d i t i o n a l food p a t t e r n ,

-

the given economic i n t e r e s t s ,

-

the t radi t i o n al ag r i cu l t u r al p r act i ce s, t h e l o c a l degree of r e l e v a n t know-how e t c . The equation of water balance and t h e optimum use of t h e s o i l moisture

a v a i l a b l e i n t h e absence of i r r i g a t i o n , o r t h e optimum use of n a t u r a l discharges a v a i l a b l e without s t o r a g e a r e seldom included among t h e r e l e v a n t d e c i s i o n c r i t e r i a i n a g r i c u l t u r e and i r r i g a t i o n development p r o j e c t s . The r e s u l t s of such a r o u t i n e approach a r e excessive i r r i g a t i o n requirements without s u f f i c i e n t c a m e and exaggerated claims on water withdrawal and s t o r a g e .

A change i n t h e r e l e v a n t engineering approach is needed, i n c l u d i n g a n o p t i mization of cropping p a t t e r n s and a harmonization of t h e r e s u l t i n g t o t a l water requirements w i t h t h e course of n a t u r a l w a t e r supply: s o i l moisture, p r e c i p i t a t i o n , d i s c h a r g e s and groundwater resources a v a i l a b l e d u r i n g t h e v e g e t a t i o n season. This harmonization o f i r r i g a t i o n requirements with a v a i l a b i l i t y of w a t e r without s t o r a g e may a l s o r e q u i r e changes i n t h e t r a d i t i o n a l food p a t t e r n : e . g . i n a r i d c o u n t r i e s w i t h heavy r a i n f a l l and high r i v e r discharges a t t h e beginning of t h e v e g e t a t i o n season, t h e i n t r o d u c t i o n of precocious p o t a t o e s i n s t e a d of r i c e c u l t i v a t i o n can h e l p t o ensure t h e food supply without extensive water s t o r a g e , which r e s u l t s i n high evaporation l o s s e s ( F i g . 2.26). Arrangements f o r i n c r e a s i n g t h e e f f i c i e n c y of water u t i l i z a t i o n d u r i n g a g r i c u l t u r a l production i n c l u d e - t h e c r e a t i o n of a n optimum s t r u c t u r e o f a g r i c u l t u r a l s y s t e m , i.e. the optimum r a t i o of t h e producers and consumers of carbonic matter,

-

t h e o p t i m i z a t i o n of t h e crop p a t t e r n , p r e f e r r i n g p l a n t s and seeds with lower

water requirements corresponding t o t h e p a t t e r n o f water occurrence, thus ensuring a n optimum u t i l i z a t i o n of t h e s o i l moisture, r a i n water and n a t u r a l s u r f a c e water d i s c h a r g e s , - t h e a p p r o p r i a t e p r e p a r a t i o n of t h e land, i n c l u d i n g e f f i c i e n t measures t o i n c r e a s e i n f i l t r a t i o n and transform overland flow i n t o subsurface r u n o f f ,

183 POPULATION NUMBER FINANCIAL RESOURCES

TRADITION

I

I

-*

FOOD

FOOD QUANTITY 8 STRUCTURE

IMPORT

,q 1 ,'

I

I

iTRIBUTION OF

RAINFALL

IRRIGATION

I I

CROP

)stNc

STORAGE

6 t h No

Fig. 2.26. Block diagram d e p i c t i n g t h e h i e r a r c h y of necessary b a s i c measures f o r safeguarding of food f o r population.

-

t h e c o n s t r u c t i o n of small r e s e r v o i r s , d i v e r s i o n dams etc. i n o r d e r to de-

c r e a s e t h e s l o p e of t h e t e r r a i n and slow down t h e s u r f a c e r u n o f f . - t h e u t i l i z a t i o n o f a p p r o p r i a t e water-saving i r r i g a t i o n methods, corresponding t o t h e s p e c i e s of t h e crops c u l t i v a t e d and t h e r e l e v a n t c u l t i v a t i o n practices, - t h e r e d u c t i o n of water l o s s e s d u r i n g conveyance by a d a p t i n g t h e design of conveyance s t r u c t u r e s t o l o c a l conditions e . g . l i n e d c a n a l s i n pervious s o i l s , closed c u l v e r t s i n a r i d c l i m a t e and by a p p r o p r i a t e maintenance and by economic a l operation, - t h e management o f a g r i c u l t u r a l s y s t e m on t h e b a s i s of d a i l y agrohydrometeorological d a t a , i . e . by watering only i n p e r i o d s of a s u b s t a n t i a l decrease i n s o i l m i s t u r e below t h e optimum v a l u e , without any o v e r i r r i g a t i o n ,

-

t h e drainage and re-use o f excess i r r i g a t i o n w a t e r ,

184

Investment a n d

Fig. 2 . 2 7 . Block diagram of water d e l i v e r y management i n a g r i c u l t u r e t o safeguard t h e environmental equilibrium of t h e a p i c u l t u r a l system.

-

the reduction of evaporation l o s s e s , e . g . by p r o t e c t i n g t h e s o i l s u r f a c e by

means of wind-breaks, i r r i g a t i o n a t n i g h t e t c . , - the re-use of municipal, i n d i i s t r i a l and a g r i c u l t u r a l waters f o r the purpose of i r r i g a t i o n ,

-

the observation of optimum a g r i c u l t u r a l p r a c t i c e s during f e r t i l i z e r and

pesticide application. There a r e e s s e n t i a l l y three ways of ensuring t h e adequate nourishment of t h e population : ( a ) s e l f - s u f f i c i e n c y across the e n t i r e range and assortment of necessary a g r i c u l t u r a l products, cb)

over-production and export of s e l e c t e d a g r i c u l t u r a l goods, thus forming

f i n a n c i a l resources t o supplement t h e lacking v a r i e t i e s by means of import, ( c ) exporting i n d u s t r i a l goods o r raw m a t e r i a l s with t h e same goal. The o v e r - i n t e n s i f i c a t i o n of a g r i c u l t u r e , namely t h e over-application of fert i l i z e r s and chemical substances i n p l a n t p e s t control a s well a s i n s u f f i c i e n t p r o t e c t i o n measures r e s u l t i n g i n s o i l wash,the wastes from farm rrachinery and r e p a i r shops and highly concentrated l i v e s t o c k production r e s u l t s i n s u r f a c e

185 and groundwater p o l l u t i o n and threatens t h e q u a l i t y of products and of t h e environment. The s c i e n t i f i c coordination

of the crop p a t t e r n with both t h e agropedologic a l and t h e hydrometeorological conditions r e s u l t s i n an increase i n y i e l d s without a s u b s t a n t i a l increase i n water requirements for i r r i g a t i o n , a s w e l l a s i n an increase i n the t o t a l n u t r i t i v e value p e r h e c t a r e c u l t i v a t e d . It helps t o maintain the equilibrium of the biogeochmical cycles i n t h e a g r i c u l t u r a l system, whose l a s t i n g function i s p o s s i b l e only under the conditions of the s t a b i l i t y of energy and matter input and o u t p u t , and under t h e conditions of an e q u i l i b r i i m of t h e system and i t s environment (Fig. 2 . 2 7 ) .

2.6.3

Water f o r I r r i g a t i o n and i t s Quality

The supplementation of s o i l moisture t o s a t i s f y crop water requirements is the main, but not t h e s i n g l e purpose of i r r i g a t i o n . By means of i r r i g a t i o n bioelements and o t h e r matter which improves p l a n t production o r s o i l conditions can e i t h e r be n a t u r a l l y o r a r t i f i c i a l l y supplied, favourable microclimatic cond i t i o n s t o support p l a n t growth maintained, and m t t e r including p e s t s which jeopardizes t h e s o i l s t r u c t u r e and t e x t u r e o r the h e a l t h of p l a n t s removed. From t h i s p o i n t of view, i r r i g a t i o n can be categorized a s follows (a)

proper i r r i g a t i o n (supplementary watering),

(b)

f e r t i l i z i n g and remedial ( p l a n t h e a l t h promoting) i r r i g a t i o n ,

(c)

protective irrigation,

(d)

s o i l leaching i r r i g a t i o n .

The q u a l i t y of t h e water used f o r i r r i g a t i o n depends on the required purpose, on t h e s o i l p r o p e r t i e s and on t h e i r r i g a t i o n operation. The b a s i c requirements a f f e c t i n g t h e qiiality of water used f o r i r r i g a t i o n can be surrmarized as follows:

(a) i t should favourably influence p l a n t growth and t h e q u a l i t y of the prodiicts grown,

(b) i t should not cause breakdowns during t h e i r r i g a t i o n operation, ( c ) it must n o t cause s a n i t a r y complaints, e i t h e r during i t s operation o r during the processing and consimption of the r e l e v a n t a g r i c u l t u r a l products, (d) water,

i t should not endanger t h e q u a l i t y of the s u r f a c e water and t h e ground-

l e ) i t must not d e t e r i o r a t e t h e s t r u c t u r e , p o r o s i t y and o t h e r agrochemical p r o p e r t i e s of the s o i l p r o f i l e . The q u a l i t y of t h e water used f o r i r r i g a t i o n has t o be categorized on the basis of i t s r e l e v a n t physical, chemical, biological and b a c t e r i o l o g i c a l prop e r t i e s (Tab. 2.32). An important property of water, deciding on i t s s u i t a b i l i t y f o r i r r i g a t i o n , i s t h e s a l i n i t y , frequently expressed a s t h e sodium percentage, t h e amount of sodium Na p r e s e n t i n r e s p e c t of t h e c a t i o n i c concentration. Rut generally mre important is t h e sodium- adsorption r a t i o SAR, which expresses

186 TABIE 2.32

ategories

Indicators A good Oxygen content (mg.1-I) a t IOOC a t 20’~

> 11

Dissolved matter (mg.1-I) Chlorides (mg .1-l)

9

1200 > 400 > 300 C 0 2 , C1

H2S, F

(Img.l-l) Radioactivity

Razz’ S r88

Odour Temperature

i n spring

OC

in s m e r

OC

Sediment s i z e

C1

c2 c3 c4

Salinity

Low Medium High Extreme

mediocre

1C-15 15-20

15-35

I a , I b , I1

Electrical conductivity fmnhos.cm-J >

0 0.25 0.75 2.25

slight

- 0.25 - 0.75 - 2.25 - 6.0

s1

offensive

>35

0.005-0.1 0.001-0.0051’

Inn’)

Water p o l l u t i o n c l a s s Degree

3. 3.

(Curie)

0.12 ) IV

111

Alkali hazard

s2

s3

s4

bw

Medium

High

Extreme

(9

9 - 17

la 7> D 7> R > R;

$

$ QP

(3.12)

The r e l a t i o n between t h e water q u a l i t y i n d i c a t o r s i n these categories can be expressed i n a s i m i l a r way:

N~ " l . . . n - planned water needs and planned water q u a l i t y i n d i c a t o r s , A, 7'

a l . . .n- o f f i c i a l l y approved water demand and approved q u a l i t y i n d i c a t o r s , Wl...n

- water withdrawal, a m u n t of water d i v e r t e d from a stream o r a groundwater resource and i t s water q u a l i t y i n d i c a t o r s ,

delivery,amount of water supplied t o t h e water u s e r and releD, d l . . . n - water vant water q u a l i t y i n d i c a t o r s ,

R, rl*..rl

' 'il..

- water

requirement, t h e amount of water required by t h e water user under t h e given economic and production conditions,

. i n - indispensable water requirement, t h e amount of water which i s indispensable t o .ensure t h e technological process, by applying a l l known water-saving techniques,

222 IJ’

U’’‘’n

QP, qp!.

- w a t e r u s e , the amount of water r e a l l y used f o r the r e l e v a n t purpose and a c t u a l water q u a l i t y i n d i c a t o r s ,

. .n

- a m u n t of water paid f o r and corresponding water q u a l i t y indicators.

The econoniy of the water development process depends on the m u t u a l r e l a t i o n s between the above values. The necessary water supply can be determined from the (indispensable) water requirements with a reserve f o r l o s s e s e t c . , deducing the amounts supplied from in-plant resources such a s water reiise and re-cycling, storage e t c . A c e r t a i n r e s e r v e , marked by the s i g n

>

between water demnd, water with-

drawal, water supply and water requirements forms the conditions f o r a f u t u r e extension of the production. Idhen t h e s i g n < occurs between these values, operational troubles m y occur. With regard t o water q u a l i t y i n d i c a t o r s , a reserve is necessary i n each case f o r manifold and multipurpose water use, o r to t r e a t water f o r any of these d i f f e r e n t purposes. The problem with t h e present p r a c t i c a l compilation of the balance of water resources and needs m i n l y a r i s e from t h e i r inadequacy i n r e s p e c t of the following p o i n t s : ( a ) r e l e v a n t s u r f a c e and groundwater resources a r e not analyzed from the point of view of t h e i r economic f e a s i b i l i t y , but i n the hierarchy of t h e i r c o g nizance/present u t i l i z a t i o n , depending mainly on the i n e r t i a of the p a s t development and on the e x t e r n a l influences of o t h e r braches of the n a t i o n a l economy, (b) t h e motivation of relevant water needs i s not s u f f i c i e n t l y analysed, r e s i l t i n g i n the approval of t h e excessive water demands and i n an extensive

development of i n d u s t r i a l o r a g r i c u l t u r a l production on account of the water (and o v e r a l l ) development, financed generally from s t a t e f i n a n c i a l resources, ‘c) d i f f e r e n t methodological conditions of occurrence and s t a t i s t i c a l i n t e r p r e t a t i o n of t h e s u r f a c e mter and groundwater ( e . g . groundwater and surface water including r e - u s e of waste waters both from s u r f a c e water and groundwater a r e analysed s e p a r a t e l y . The overdevelopment of one of these resource categories m y be a consequence of o r the reason f o r t h i s p r a c t i c e ) . ‘d) non-conventional water resources a r e n o t taken i n t o account s u f f i c i e n t l y . The problem of t h e compilation of t h e balance of water resources and needs does not concern s u r f a c e and groundwater resources only, b u t a l s o s o i l water and r a i n f a l l . S o i l water safeguards the majority of p l a n t water requirements. I n a r i d and s e m i a r i d a r e a s , t h e problem of the m i n t e n a n c e of t h e vegetative canopy has to be included i n t h e r e l e v a n t water balance considerations. The water requirements of t h e v e g e t a t i v e canopy can be included i n t h e framework of the i r r i g a t i o n water requirements. S o i l water including t h e stock of the

capillary r i s i n g groundwater can a l s o be excluded a t t h e beginning of the compi-

223 l a t i o n p r o c es s , because t h e water which i s a v a i l a b l e f o r the e va potra nspira tion depends on local co n d i t i o n s , thus forming

2

closed system of l o c a l water supply

and production, and water balances a r e ge ne ra lly compiled f o r s u p e r i o r land complexes. The h e t e r o g en ei t y of t h e a v a i l a b l e d a t a , t h e diffe re nc e s i n the e x t e n t and frequency of measuring, and t h e d i f f e r e n t methods of data recording and statist i c a l e v a l uat i o n a l l tend t o complicate t h e common compilation of s u r f a c e and groundwater balances. The b a s i c inequation f o r t h e compilation of water balances and needs is / m3 . s-l , m3 )

Q

$

N

Q

- a v a i l a b l e water resources

N

- w a t e r needs (water withdrawals W)

(3.14)

3 -1 , m3 ) ( m3.s-l , m3 ) (m .s

This b a s i c inequation can be

formulated f o r both t h e surfa c e and groundwater resources of a c e r t a i n geographical u n i t f o r a lim ite d pe riod i n t h e following way Qs + Qsr + G

.s

+ G

gr

+ L +

F

5

W

+

bQ + G (m 3 pe r period) go

13.15)

Qs - s u r f a c e water inflow Qsr - s u r f a c e wat er i n reservoirs G - groundwater inflow g G - groundwater r es er v e

F

L

- water conveyance i n t o t h e area

F

- r e t u r n flow - waste water

I4

- water withdrawals i n cl u d i n g water conveyance from the a r e a

l Q - r e q u i r ed minimum d i s ch ar g e G

go

-

groundwater outflow

The b a l a n ce f o r s u r f a c e water is expressed as follows: Q, + Qsr

+

L - I + F = Ids + N)

(m3 p e r pe riod)

(3.16)

(m’ pe r pe riod)

(3.17)

and f o r groundwater resources

G +G g

gr

+I

=

W +G g

go

I - i n f i l t r a t i o n i n t o groundwater resources from s u r f a c e re sourc e s, waste water and water conveyance

224 W

- w a t e r requirements covered by s u r f a c e water resources

LJ

-

S

F:

water requiremets withdrawn from groundwater resources.

Class

Water q u a l i t y

Characteristic suitability

TJsage

I.

a . very clean

drinking water

b . clean slightly polluted

domestic uses l i v e s t o c k breeding

urban and r u r a l supply, food and p h a m c e u t i c a l i n d u s t r y , swimming pools l i v e s t o c k breeding, water s p o r t s and recreation

111.

intensively polluted

o t h e r uses

i n d u s t r i a l supply, irrigation

IV.

deteriorated

s e l e c t e d in-stream uses

n o t s u i t a b l e f o r withdrawal uses, only f o r n a v i g a t i o n , hydropower generation, waste disposal

11.

Categories of water q u a l i t y according t o i t s e f f i c i e n t usage ( s e e Tab. I . 2 4 ) . TABLE 3.5

Group

Characteristics

A.

Water acceptable f o r r e l e v a n t purposes of usage without treatment o r a f t e r simple pre-treatment

B.

Water acceptable f o r relevant purpose of usage a f t e r inexpensive, simple treatment

C.

Water acceptable f o r r e l e v a n t purpose of usage a f t e r s p e c i a l , but economical l y f eas i b 1e treatment

D.

Water acceptable f o r r e l e v a n t purposes of usage a f t e r an economic a l l v u n f e a s i b l e treatment

Groups of water q u a l i t y according t o t h e f e a s i b i l i t y of water treatment f o r t h e required purpose of usage. The purpose of the compilation f o r m t h e b a s i c d i f f e r e n c e between t h e hydrol o g i c a l balance and t h e balance of water resources and needs: The hydrological balance analyses t h e q u a n t i t y of water i n t h e hydrologic c y c l e , i . e . t h e inflow i n t o and t h e outflow from c e r t a i n geographical u n i t and simultaneously the increment o r decrement of water i n s i d e . The balance of water resources and needs analyses t h e q u a l i t y and q u a n t i t y of a v a i l a b l e water resources and t h e i r seasonal f l u c t u a t i o n , comparing them with t h e course o r development of t h e r e l e v a n t water needs (demands, with-

225 drawals, requirements) i n relevant categories of water q u a l i t y (Tab. 3 . 4 ) . I n addition to t h i s available water resources can f o r water development purposes be categorized according t o the f e a s i b i l i t y of water treatment for the required purpose of usage (Tab. 3 . 5 ) .

3.4

PIINIMUM WATER TABLE AND MINIElUM DISCHARGES

The functions of water a r e manifold and any u t i l i z a t i o n of water resources must not be allowed to hinder e i t h e r the natural functions of water o r i t s genera1 u t i l i z a t i o n by human society. It i s , therefore, of paramount importance to safeguard the s o c i a l functions of water and i t s e s s e n t i a l ecological functions, especially f o r

( a ? the conservation of the natural ecosystem i n the rived bed, (b) the conservation of the sediment transport, (c) the conservation of the hygienic and a e s t h e t i c functions of water, Id> the conservation of the natural vegetative canopy within the sphere of influence of groundwater withdrawals, ( e j conservation of the groundwater t a b l e and the natural ecosystems along water courses. The water regime has a b a s i c influence on the biological balance i n ecosystens. Changes i n the water regime occur a s changes i n flooding, the season of i t s occurrence, i t s duration and frequency, the

-

depth and velocity of flow i n the flooded area, the water and sediment q u a l i t y ,

-

i n the groundwater regime: i n the groundwater recharge, groundwater level

fluctuation and q u a l i t y , especially i f t h i s water supplies the s o i l moisture of the s u p e r f i c i a l layer. The occurrence of a minimum water table i n a r i v e r , and a minimum groundwater table along i t s course, depends on the occurrence of minimum discharges, provided t h a t the water t a b l e is not impounded a r t i f i c i a l l y . Therefore, during minimum discharges a c r i t i c i a l s i t u a t i o n occurs, whose long-term influence on the e x i s t i n g naturzl conditions determines the c q o s i tion of the relevant ecosystems. When the values of water discharges influenced by human a c t i v i t i e s such as reservoir operation o r water withdrawals exceed the yearly minimum, the balance of ecosystems m y not be disturbed, even i n the case of an increase i n the frequency of the occurrence of low discharges o r i n the case of an extension of t h e i r duration. In many cases, depending on the n a t u r a l conditions and adaptability of ecosystems, even a decrease i n n a t u r a l discharges below the value of t h e yearly minimum need not necessarily have a s i g n i f i c a n t l y harmful e f f e c t . Taking t h i s i n t o account, the value of t h e admissible minimum discharge can be derived from the minimum yearly discharges i n the following way:

226

Im3 . s -7 )

(3.78)

PQ

- minimum admissible discharge (minimum acceptable flow?

r

t h e n a t u r a l minimum y e a r l y discharge, usually 9 355d the r a t e of minimum discharge reduction ( r 5 1)

sin-

I n t h i s way the minimum acceptable flow can be derived frcm t h e minimum monitored discharees only (Tab. 3 . 6 ) . I n rmny cases such a n o v e r s i m p l i f i c a t i o n does not lead t o a p p r o p r i a t e res u l t s . The r a t e of minimum admissible discharge reduction i s a function of - climatic factors

*C

-

geomorphological f a c t o r s ‘m b i o l o g i c a l f a c t o r s ( a d a p t a b i l i t y , drought r e s i s t a n c e ) Xb - groundwater regime and s u r f a c e water regime

%d

- water q u a l i t y ( n a t u r a l p o l l u t i o n ) X 9 - anthropogenic f a c t o r s ( a r t i f i c i a l p o l l u t i o n , required water u t i l i z a t i o n

xx

etc.) I t goes without saying t h a t t h e minimum admissible discharge o f t e n depends

on t h e season and may, t h e r e f o r e ,

Xn=fm (Xc

Xm

>

m - month (1,2,3

xb

Xw

3

Xq

d i f f e r f o r each month Xx)

.

m Qmin (m3.S-l)

,....... 12)

(3.19)

ctm

Furthermore, t h e maximum admissible duration of t h e minimum discharges a l s o depends on t h e season and can be expressed a s a function of t h e degree of the discharge reduction tm= Fm (XC

, xm , xb , xw , xq , XX) “tn

!days?

(3.20)

Tnin

Vmin- n a t u r a l

minimum discharge i n t h e month m

The above f a c t o r s o r t h e r a t e of t h e minimum discharge reduction and its adm i s s i b l e d u r a t i o n h a s , t h e r e f o r e , t o be derived on the b a s i s of t h r e e groups o€ criteria : (1) c r i t e r i a of environmental p r o t e c t i o n , (2) criteria of in-stream water u t i l i z a t i o n ,

(3)

criteria of withdrawal p r i o r i t i e s .

The criteria of environmental p r o t e c t i o n include:

227 (a)

t h e c r i t e r i o n o f b i o l o g i c a l equilibrium i n t h e stream channel, i.e. corn

p l i c a t e d problems w i t h regard t o t h e undistrubed development of a q u a t i c l i f e , ‘b)

t h e c r i t e r i o n o f t h e e x t e r n a l e q u i l i b r i u m i n t h e landscape, i . e . con-

s e r v a t i o n o f n a t u r a l t e r r e s t r i a l ecosystems, ( c ) t h e c r i t e r i o n o f t h e physical e q u i l i b r i u m i . e . determination of minimum discharges which do n o t upset t h e balance of t h e erosion and sedimentation processes i n t h e r i v e r bed, Id)

t h e f i r s t c r i t e r i o n of w a t e r q u a l i t y , i . e . n o t allowing i t t o exceed t h e

mximum a d m i s s i b l e chemical, b i o l o g i c a l and h e a t p o l l u t i o n l e v e l s , i n o r d e r t o p r o t e c t groundwater resources ( e ) t h e f i r s t c r i t e r i o n of water t a b l e a l t i t u d e , required f o r a e s t h e t i c enj oymen t . The c r i t e r i a of in-stream water u t i l i z a t i o n i n c l u d e : (a)

t h e c r i t e r i o n of hydrolof.ica1 balance, i .e. deterinination of minimum

discharges which l i m i t e x c e s s i v e drainage of groundwater o r permit t h e i n e v i t able i n f i l t r a t i o n , (b’

t h e second c r i t e r i o n of t h e m t e r t a b l e , required f o r t h e general water

u t i l i z a t i o n i n t h e r i v e r channel, a s w e l l a s f o r navigation and r e c r e a t i o n . fc)

t h e f i r s t c r i t e r i o n of d i s c h a r g e s , necessary f o r power g e n e r a t i o c , t h e second c r i t e r i o n of water q u a l i t y , i . e . determination of the nece-

(d) ssary d i l u t i o n of waste waters t o safeguard t h e undisturbed course of n a t u r a l

s e l f - p r i r i f i c a t i o n processes and enable general water u t i l i z a t i o n , f i s h e r y . recreation e t c . , The c r i t e r i a of withdrawal p r i o r i t i e s i n c l u d e : la)

t h e second c r i t e r i o n of discharges t o cover r e l e v a n t downstream water

withdrawals, (b)

t h e t h i r d c r i t e r i o n o f water q u a l i t y , i . e . determination of t h e waste

water d i l u t i o n which would permit s a f e and economic water treatment processes f o r f u r t h e r water u t i l i z a t i o n by the p o l l u t i o n and i n d u s t r y . A l l these c r i t e r i a depend on l o c a l c o n d i t i o n s . Tne e s t a b l i s h e d values may d i f f e r , depending on t h e above f a c t o r s (Xc,. . . .Xx). The problem of minimum adm i s s i b l e discharge is g e n e r a l l y considered as a hygienic and economic one. I n such a way, t h e environmental f a c t o r s a r e n o t accordingly taken i n t o account. Tne a p p r o p r i a t e determination of t h e minimum admissible discharge is hampered by inadequate information, i n a d d i t i o n t o t h e economic o b s t a c l e s , l e g i s l a t i v e and i n s t i t u t i o n a l problems and t h e lack of r e s p o n s i b i l i t y of t h e a u t h o r i t i e s towards t h e needs of t h e s o c i e t y . Depending on t h e given economic p o s s i b i l Lties, t h e approved minimum admissib l e discharge can be used t o s e r v e environmental purposes, o r t o cover e s s e n t i a l withdrawals, i . ? . t o f u l f i l l only some or a l l t h e above-mentioned c r i t e r i a . Taking mainly economic f a c t o r s i n t o account, minimum admissible discharges a r e

228 determined on t h e b a s i s of a compromise between t h e c o s t of waste water t r e a t ment on t h e one hand and the economic l o s s e s which m y occur a s a r e s u l t of t h e d e t e r i o r a t i o n i n water q u a l i t y and t h e subsequent l i m i t a t i o n s of water supply t o lower r i p a r i a n users on the o t h e r hand. A p r a c t i c a l assessment of t h e minimum acceptable flow depends i n t e r a l i a on water requirements f o r e f f l u e n t d i l u t i o n t o achieve t h e requested water q u a l i t y , characterized e . g . by 8 mg of t h e b i o l o g i c a l oxygen demand BOD5 i n e f f l u e n t s , whose q u a l i t y depends on t h e admissible waste water p o l l u t i o n i n t h e a r e a i n question. Discharges w i t h i n t h e l i m i t s of Q355d

t o Q270dcan a l s o be assessed,

depending on the type and s t a t e of geological formations which do n o t destroy the groundwater regime andlor which safeguard the conservation of the charact e r i s t i c ecosystem e t c . !Tab 3.6). TABLE 3 . 6 \dater course

Minimun discharge

Mountain creeks

0.'

Water courses with a r e l a t i v e l y steady flow

0.5 0.8 - '1.0Omin

Other water courses

%in

Rin

Minimum acceptable discharges MQ according to t h e recomnendation t o the Economic Conmission f o r Europe of the United Nations (1970). When t h e minimum admissible discharge i s e s t a b l i s h e d , n o t respecting the c r i t e r i a of in-stream water u t i l i z a t i o n and t h e c r i t e r i a of withdrawal p r i o r i t i e s , p r a c t i c a l discharge l i m i t s should be determined f o r each stream s e c t o r t o safeguard a l l e s s e n t i a l requirements f o r in-stream water u t i l i z a t i o n and essent i a l water withdrawals. I n such a way a minimum value of n o t less than Q355d

can be accepted a s

l i m i t i n g j u s t below t h e d a m p r o f i l e . Corresponding t o t h i s i n a s e c t o r of a stream n o t influenced by t h e e f f e c t of a r e s e r v o i r the minimum admissible discharge may be assessed w i t h i n t h e l i m i t s (3.21) I n t h e intermediate s e c t o r s , t h e r e l e v a n t values decrease down t o the p r o f i l e , where the reservoir impact i s n o t apparent. I n any case, the minimum admissible discharge should a l s o depend on t h e water q u a l i t y , i.e. be higher f o r low water

I quality, e.g. Q355d i n s t e a d of I Q364d. An assessment of the minimum admissible discharge m y make i t necessary t o take measures t o change e x i s t i n g r e s e r v o i r operation and t o l i m i t water withdrawals so as t o r e s p e c t t h i s value e t c . A u t h o r i t i e s might approve of a drop

229 below these values i n exception c a s e s , b u t l i m i t it t o some lower values. Every appropriate measure should be taken t o safeguard the necessary minimum discharge including t h e construction of r e s e r v o i r s o r conjunctive use of groundwater and surface water discharges whenever t h e p o s s i b i l i t y of f u r t h e r water withdrawals occurs. ACTIVE AND PASSIVE WATER B A M C E

3.5

The equilibrium of water balances and needs s i g n i f i e s t h a t no a c t i o n has t o be taken t o s a t i s f y e x i s t i n g needs i f no f u r t h e r uses a r e planned. For such a s t a t e an i n t e r v a l of 2 10%has t o be introduced t o make allowances f o r the elast i c i t y of demand and i t s adaptation t o water shortages and a l s o f o r the unc e r t a i n t i e s of data c o l l e c t i o n and processing. Water demands can be c u t by up t o 20%without any important negative operational and economic consequences (Fig. 3.2). The minimum admissible discharge f o r environmental p r o t e c t i o n and in-stream water u t i l i z a t i o n (not including any withdrawals) has t o be regarded a s an indispensable water need. Bearing t h i s i n mind, t h e balance of water resources

and needs may be considered t o be i n equilirbium i f

(3.22)

i n each of t h e l o c a l i t i e s ( r i v e r s e c t o r s ) considered Wi - water withdrawals (W.
1.1 Q

- PQ

(3.24)

i=1

A favourable balance of water resources and needs i n d i c a t e s t h a t a b s t r a c t i o n

f o r e x i s t i n g water uses can be extended and new uses can be s a t i s f i e d , including water conveyance i n t o neighbouring a r e a s with passive balances. The unfa-

230 Water d e l i v e r y

Average decrement

Losses of water u s e r s

Measures

No economic

Un im p o r t o , ti only short- t e r m 'decrease

Nil

losses

Medium decrease o r long p e r i o d o f low

of decrease

Substantial but short-term decrease *

Substantial and long term limitation or c u t t i n g the delivery

-

Losses do not excees the expenses for emergency water supply

-

for development of new resources

Losses exceed the development expenses for additional resources

Genera I l i m i t a t ion of d e l i v e r y

Emergency delivery, general substantial limifations

Development of additional resources, their mutual interconnection

*

Fig. 3.2. Consequences of a decrease i n water d e l i v e r y and necessary operational o r investment measures (p - r a t e of guarantee, R - water reqtiirements). vourable 'passive) water balance i n d i c a t e s t h e need f o r a development of new water resources o r f o r water conveyance from neighboilring catchments with an a c t i v e water balance. From t h e operational point of view i t i n d i c a t e s the need f o r r e s t r i c t i n g present water uses and f o r c u t t i n g down e x i s t i n g water uses e . g . by excluding i n e f f i c i e n t uses and through the introduction of water-saving techniques. 'when compiling

balances of water resources and needs, the balancing e f f e c t of

o u t l e t discharges should be taken i n t o account F

=

C

- water consumption

Id-C

("3 \,

(3.25)

(m3)

The compilation of s t a t i s t i c s of the i n t e r r e l a t i o n s h i p s between water supply (amour.t of water siipplied) and water conslimption gives a b a s i c p i c t u r e of deve-

23 1 lopment p o s s i b i l i t i e s by t h e a p p l i c a t i o n of water re-use and recycling techniques i n the sphere of water u s e r s , Nevertheless, i t does n o t mirror the possibi-

l i t i e s of o t h e r water-saving techniques which a r e t o be considered s e p a r a t e l y , i n connection with r e l e v a n t technological processes (Tab. 3.7). TABLE 3.7 ~

Balance of water resources and needs

Basic equation

c)

Favourabl e (active) In equilibrium Ilnfavourab l e (passive)

>

1.1 I\r

Q

< 0.9 ld

>

~~~

Measures

9

New water uses can be developed

0.1 Q

1x1 < 0.1 x

~

Coefficient of usage of water resources

/do.

x>O X

Q 5 1 .lId

0.9W

Water surplus or deficit

0.9&p& 3.1

Q

NO a c t i o n necessary

Water .us: restriction, water r e s o u r ces development

( 0

1x1 > 0.1

p1.1

Q

~~~~~

Q u a n t i t a t i v e indices of t h e balance of water resources and needs. I n p r a c t i c e , t h e d i f f e r e n c e between usable water resources and demnds i s o f t e n used a s an important q u a n t i t a t i v e i n d i c a t o r . It i s c a l l e d water s u r p l u s i f p o s i t i v e , o r water d e f i c i t i f negative, and is t o be derived from s t a t i s t i c a l records i n t h e following m n n e r

X

Q-W+F

x

=

X

- water

i.e. (,,3 , m 3. s -1

Q-c surplus f + ) , water d e f i c i t (-)

(3.26)

(m3 , m3 .s -1 )

On t h i s b a s i s , t h e r a t e of usage of a water resource i s t o be defined by the

ratio

f W; i=l

0

n

t F;

i=1

(3.27)

(3.28) expresses t h e degree o f water re-use of r e l e v a n t resources. The reversed value of t h i s r a t i o , applied t o the whole country and covering an average year, was introduced by Balcerski (1968) for comparing water resources u t i l i z a t i o n i n different countries:

232

(3.29)

cm- index of water management k

Qi - mean annual surface and groundwater (m3 per year)

J=1

f i=1

runoff of the whole country IJi - annual water needs of the whole

(m3 per year)

country

This index of water management does not express the a c t i v i t y or passivity of water balances and needs. It characterises the r a t i o of surface and groundwater resources development and u t i l i z a t i o n - a t the beginning of economic development and - the re-use of water a t further stages of development. This index does not include the internal recycling, i . e . the repeated use of the same water inside a closed c i r c u i t of different water users. It characterizes the development of water management i n the relevant country/area and the coordination of the repeated use of the same water by the different users, but does not characterize the efficiency of water use by relevant water users. Quantitative indices of water u t i l i z a t i o n depend on the season, especially i f i r r i g a t i o n requirements prevail. This unevenness can be expressed by the r a t i o of a summer r (April to September) and wlnter rw (October t o March) w i t h drawals o r by the r a t i o of summer cs and winter water consumption cw: n ws; ww; iwa; r = i=l r = i=1 1=1 (3.30)

f

S

W

f

i=l wai

f f wa;

1

i=I

i=l

(3.31)

c S

IJai - annual water withdrawals Idsi,

Idwi - water withdrawals i n the summer

3 !m ? (m3)

and winter season

3

Fai - return flows

(m per year)

Fsi,Fwi- return flows i n the sumer and winter season

rm'

per season)

23.3 PROBABILITY OF THE SATISFACTION OF WATER REQUIREPEN'S

3.6

The course of water a v a i l a b i l i t i e s Q and of water consumption C can be ex-

pressed as a function of t i m e

(3.32)

Their d i f f e r e n c e water s u r p l u s o r d e f i c i t X i s , t h e r e f o r e , a l s o a function of time

X

=

Q - C

=

fl (t) - f2 (t)

=

f

(3.33)

3 (t)

The p o i n t s of i n t e r s e c t i o n of t h e time function of a v a i l a b l e water resources and the time function of t h e i r consTmption d i v i d e the period of the a c t i v e and passive water balance. The d u r a t i o n of the p a s s i v e balance, i . e . of nonguaranteed water supply, depends n o t only on t h e q u a n t i t a t i v e v a r i a t i o n of water resources i n time, b u t a l s o on the course of water withdrawals and consumption, i . e . on the s t r u c t u r e of water u s e r s . S i m i l a r s t r u c t u r e s of water users under the same c l i m a t i c conditions produce similar time functions of water consumption. RATE OF GUARANTEE FOR DIFFERENT DELIVERY REGIMES

FLUCTUATION OF WATER DELIVERIES (REQUIREMENTS) AND WATER AVAIL ABI L IT IE S

equi-

equilibriurn for DI

equilibriurn for D2

.....- ...... ........- ............. .............. passive balance ective balance for DI

b

%

t

rate of guarontee

for DI

Fig. 3 . 3 . Chronological r e p r e s e n t a t i o n of the course of water d e l i v e r i e s . (requirements), water resources a v a i l a b i l i t y and the d u r a t i o n curve of r e l e v a n t water balance states: DL-3 - water d e l i v e r i e s (requirements), 3 average values, Q - a v a i l a b l e wa er r e s o u r c e s , t - time.

234 Fluctuation i n water consumption can therefore be characterized by average values and by the r a t e of t h e non-guaranteed water supply evaluated i n the same rranner as t h e course of discharges i n hydrology: by the duration curve. Such a duration curve i n d i c a t e s t h e duration of the non-guaranteed water supply (%) i n the given long-term period f o r the relevant course of the water consumption, characterized by t h e average value (Fig. 3.3). The decrease i n water requirements increases t h e r a t e of guarantee and extends t h e duration of t h e favoura b l e balance of water resources aiid needs [requirements). P r a c t i c a l l y , the i n t e r v a l

2

10% f o r t h e equilibrium of water balances and

needs has t o be considered and r e l e v a n t curves derived from values correspondi n g t o t h e increased values of water a v a i l a b i l i t y by 10%and average values of

water consumption ( o r f o r c h a r a c t e r i s t i c water resources data and water consump t i o n ) decreased by 10%. The r a t e of guarantee of t h e water supply has t o be economically considered from t h e p o i n t of view of - t h e water u s e r , - the w a t e r supply o r g a n i s a t i o n , - t h e n a t i o n a l economy. The c o s t of water f o r i t s u s e r can be expressed a s t h e function M = f(W) M

W

(3.34)

- c o s t p e r u n i t o f production ($ p e r t ) - amount of water suppljed t o t h e (per u n i t of product m p e r t , m .etc. water withdrawal W, d e l i v e r y D , or water demand A, depending on methods of payment and nasurement)

yter

A g r i c u l t u r e and industry can operate without r e s t r i c t i o n o r i n t e r r u p t i o n s ,

i . e . a t f u l l capacity, when D => R i =< R Ri - t h e minimum discharge with which the user is a b l e t o operate without l i m i t i n g t h e production f indispensable water requirement) ( 2 . s - l , m

D - water d e l i v e r y R

-

(D

< W)

t h e discharge which meets t h e user's requirenents without using watersaving techniques

.t-1 )

f r n3 .s -1)

(m3 .s -1 )

A l i m i t a t i o n o r i n t e r r u p t i o n of t h e water supply causes economic losses i n industry and a g r i c u l t u r e . A decrease i n t h e water supply beneath the lower l i m i t R . r e s u l t s i n a n inmediate, non-proportional increase i n c o s t s p e r u n i t of production '%I. The production r a t e decreases , a l s o o f t e n influencing the

235 q u a l i t y of production, both i n a g r i c u l t u r e and i n industry. A f u r t h e r decrease i n water supply can r e s u l t i n a similar non-proportional inc re a se i n c o s t s

Of3>, because production can be ensured e . g . by a n emergency w a te r supply only, and i n a g r i c u l t u r e by c u t t i n g down t h e a r e a under i r r i g z t i o n . I t is q u i t e obvious t h a t a decrease i n water supply below a c e r t a i n l i m i t i n g value de finit e l y i n t e r r u p t s t h e production p r o ces s , b u t a minimum discharge Rmin may s t i l l be r e q u i r e d f o r t h e maintenance of some processes i n industry and f o r conserv a t i o n a l purposes i n a g r i c u l t u r e !Fig. 3 . 4 ) .

3 m nax

PRODUCTION R~GIME c

c

Fig. 3 . 4 . Graphical r ep r es en t at i o n of t h e influe nc e of l i m i t i n g water d e l i v e r i e s on o p er at i n g c o s t : Rmin - i n d i s p e nsa ble water requirements (e .g. with - water requirements w ith no re c yc ling, Ro t rmximum r e c y c l i n g ) , ,R, optimum discharge t o be a b s t r a c t e d fronrr! t h e u s e r s viewpoints, M 1 - operating c o s t s under d i f f e r e n t production and water de live ry regimes, )&,in - minimum c o s t f o r t h e u s er .

4

The guarantee rate of water requirements s a t i s f a c t i o n is simply t h e proba b i l i t y of s a t i s f y i n g t h e q u a n t i t a t i v e conditions of water requirements L

P

= L1 t . 100%

p

- t h e guarantee rate of water requirements s a t i s f a c t i o n

(3.36)

tl - t h e d u rat i o n of t h e s a t i s f a c t i o n of water requirements (days) t

- t h e analysed long-term period

(days)

236 By optimizing water use i n a g r i c u l t u r e and i n d u s t r y , a n optimum discharge can be determined, thus safeguarding the required production a t minimum c o s t f o r t h e u s e r , 5 . e . optimum discharge t o be a b s t r a c t e d from the u s e r ' s viewpoint, o r f o r the n a t i o n a l economy, i . e . from the s u p e r i o r nation-wide p o i n t of view ( R . ) . m e o v e r a l l e f f i c i e n c y of the water supply does n o t depend on the water c o s t borne by t h e water u s e r , b u t on the r e l e v a n t c o s t of t h e water resources development and operation and on t h e losses r e s u l t i n g from t h e c u t t i n g down of production borne by t h e n a t i o n a l economy. But t h e economic r e l a t i o n s between the water iisers and organisations respons i b l e f o r the water supply a r e one-way. Relevant economic and l e g a l feedback is not s u f f i c i e n t t o p r o j e c t accordingly t h e l o s s e s t o t h e water s u p p l i e r : These organisations a r e only a f f e c t e d by t h e decrease i n income from r e s t r i c t e d water siipply o r by t h e p o s s i b l e duty t o safeguard a compensatory emergency water supply. A decision on t h e r a t e o f guarantee has t o be taken from t h e over-all p o i n t of view of t h e n a t i o n a l economy: Supplementary water resources development, generally borne by the national economy, i s economically f e a s i b l e i f the t o t a l losses cause by the i n t e r r u p t i o n o r the decrease i n the water supply exceed t h e t o t a l construction and operation c o s t s . TAB11 3 . 8

Water u s e r

Rate of guarantee (%)

Population:

Water u s e r

Rate of guarantee (%)

Power production :

Big c i t i e s

95

I n t e r s t a t e sys tem

99

Small c e n t r e s

so

Local system

90

Agriculture:

Industry :

F i e l d crops

75

Intensive cultivation

85

Interstate importance

97

Local importance ~

Water t r a n s p o r t :

Int e r m tiona 1 National Local importance

Recreation

90

~~~

80

95 85 60

The recomiended guarantee rate of water requirements s a t i s f a c t i o n f o r b a s i c categories of water u s e r s . The f u l l s a t i s f a c t i o n (100%) of water requirenients f o r t h e n a t i o n a l economy is completely uneconomic, r e q u i r i n g a disproportionate developnent of water resources, i n c e r t a i n cases a l s o emergency r e s e r v o i r s and networlts. It is very

237 important t h a t an increase i n the guarantee r a t e of a few per cent within the l i m i t s from 80 t o 95, and especially from 95 t o 99 per cent r e s u l t s i n a disproportionate increase, i n a doubling o r even i n a higher increase of construction and operation c o s t s . I t is therefore indispensable to accept t h a t the water supply could be decreased and even interrupted during periods of a lack of water o r during necessary maintenance and reconstruction works. The l i m i t s of t h i s guarantee r a t e depend on the relevant economic and s o c i a l losses (Tab.

3.8). The r a t e of guarantee does not only depend on q u a n t i t a t i v e , but a l s o on q u a l i t a t i v e parameters. The conditions f o r s a t i s f y i n g the quality requirenients With the necessary degree of probability a r e of two types; i . e . for quality indicators, which must (a)

2

q;

-

be g r e a t e r than the necessary concentration (oxygen content e t c . )

q;,

(3.37)

not be g r e a t e r than the allowable concentration

(b)

(3.38)

(i= 1,2..., n-l,n

thermal, chemical, biological and bacteriological pollution).

The r a t e of guarantee f o r q u a l i t a t i v e conditions represents the probability of exceeding the necessary and not exceeding the admissible indicators. The guarantee r a t e of water requirements s a t i s f a c t i o n i s therefore a function of many randcm variables f(R)

=-

probability

(Q

2

R

,

' I '

To determine t h i s probability with the necessary accuracy requires daily records of q u a n t i t a t i v e data concerning water resources and water requirements. The density of water q u a l i t y data need not be even, but must embrace any occurrence of pollution which exceeds the accepted l i m i t s . The guarantee r a t e of water requirements s a t i s f a c t i o n m y be p r a c t i c a l l y expressed i n three ways: ( a ) guarantee of duration (b)

guarantee of volume

(c)

guarantee of frequency

X

t

xV

xf The guarantee of frequency, expressed by the r a t i o of the number of years (or days) with a c t i v e balance o r balance i n equilibrium and the t o t a l nunber of years of the given period, defines n e i t h e r the r e a l frequency of the interruption of the water supply, nor the depth of the water deficiency, nor i t s r e a l

238 duration. The economic e f f e c t i s q u i t e d i f f e r e n t i f these days a r e spread o r accumulated. The r a t e expressed by the r a t i o of the number of years, though used q u i t e o f t e n , is almost without p r a c t i c a l use (Tab. 3.9). TABTX 3.9 Rate of guarantee

Formula

Guarantee of duration

x

t

t' = --

t

Guarantee of volume

%=F

Guarantee of frequency

Xf

=

Y' y-

Remarks

t - t o t a l duration of the period t ' - accumulated duration of the periods i n which the use i s s a t i s f i e d

w

- t o t a l volume of water requirements W ' - volume of water a c t u a l l y supplied Y - t o t a l number of years i n the period Y ' - number of years i n which the water use is completely s a t i s f i e d

Rate of guarantee f o r q u a l i t a t i v e water requirements expressed a s a percentage o r f r a c t i o n of the whole according t o the Economic Commission f o r Europe (1973). The guarantee of duration and of volume have the same disadvantage, namely t h a t of expressing neither the frequency nor the duration of the relevant disturbances of supply. The r e l a t i o n between the three mentioned r a t e s i s : Xf

% > E c > E d ; Q s a < Q s b < Q s c < Q s d ;G a > C;b’ G c ) d ‘ Q b < Q a H c > Hd P - p r e c i p i t a t i o n , H - vapour condensation, E - w a p o r a t i o n , QS - surface r u n o f f , G - poundwater r u n o f f , 9 - t o t a l runoff and maxirnuni discharges.

n

Accumulation on a f f o r e s t e d land occurs to a more s i g n i f i c a n t e x t e n t during lower r a i n f a l l and runoff than during extreme r a i n f a l l and maximum floods. Floods with a one y e a r frequency of occurrence may increase a f t e r c l e a r i n g more than t e n times

and floods with a hundred

y e a r frequency of occurrence s e v e r a l times,

i n i n h e r e n t dependence on t h e s i z e of the catchment, the depth of the s o i l and i t s moisture before the r a i n f a l l . Forests with shallow s o i l s have no important i n f l u e n c e on the decrease i n discharges i n comparison with deforested a r e a s . The accumulation and r e t a r d a t i o n e f f e c t l a r g e l y depends on the s a t u r a t i o n of the s o i l s , i . e . on the frequency of r a i n occurrences and on the i n t e r v a l between them. I f the accumulation capacity is exceeded, t h i s causes a n immediate increase in

the s u r f a c e runoff.

The water management function of f o r e s t s depends considerably on h m n a c t i v i t i e s and e s p e c i a l l y on f o r e s t management. IJndis turbed f o r e s t c u l t u r e s a r e character-

279 ized by t h e i r important

protection effects

a e a i n s t floods and erosion. Multi-

s t o r e y f o r e s t s c u l t u r e s transform floods more e f f e c t i v e l y than c u l t i v a t e d s i n g l e s t o r e y monocul t u r e s , and f a r more

efficiently

than pastures o r

cultivated

a g r i c u l t u r a l land (Fig. 4 . 8 ) .

600

400

200

0

C A N O P Y REDUCTION

Fig. 4 . 8 . (a) The increase i n the t o t a l annual s u r f a c e runoff and i n the f l u c t u a t i o n of discharges a s a consequence of c l e a r i n g an a f f o r e s t e d catchment according t o Zelen9, KPeEek and Kretmer (1979); p - the decrease i n the biomass ( % ) , Qr - t o t a l y e a r l y r u n o f f , ()f - flood discharfres. (b) The increase i n t h e t o t a l annual runoff Qa as a consequence of c l e a r i n g accordine to Rosch and Hewlett (1982): 1 - coniferous, 2 - deciduous, 3 - bush.

Mechanized

c l e a r i n g , the t r a n s p o r t of timber and the network of t r a n s p o r t

c o m n i c a t i o n s decrease t h i s p o s i t i v e function. The a c t i v i t i e s of c l e a r i n g , tend t o compact the s o i l , destroying

h a r v e s t i n g , t r a n s p o r t and o t h e r machines

i t s s t r u c t u r e , which is conducive t o i n f i l t r a t i o n , both i n f o r e s t r y and agric u l t u r e . The movement of t r a n s p o r t machines, such a s f o r towing logs, form

r i l l s , g u l l i e s and channels f o r t h e concentration of surface r u n o f f , whose increased

tractive

force a c c e l e r a t e s the erosion process.

The d i r e c t r e l a t i o n s h i p between t h e runoff c o e f f i c i e n t and s o i l wash and t r a n s p o r t was proved by means land grading f o r the

of measurement. Murzaev (1977) i n d i c a t e s t h a t the

mechanized a f f o r e s t a t i o n increases the runoff c o e f f i c i e n t

of f o r e s t land by up to 0.8 (Tab. 4 . 5 ) . VeEetative canopy forms an e f f e c t i v e p r o t e c t i o n a g a i n s t

erosion f o r the land

s u r f a c e . The b e s t p r o t e c t i o n i s formed by n a t u r a l ecosystems. The r e s i s t a n c e of c u l t i v a t e d f o r e s t s without

comprehensive anti-erosion measures i s r e l a t i v e l y

s m a l l e r , because of t h e i r gecmetrical arrangement, monotonous p l a n t species and human a c t i v i t i e s during t h e i r c u l t i v a t i o n . an e f f i c i e n t

4.6).

Nevertheless, f o r e s t s generally form

p r o t e c t i o n a g a i n s t erosion, i f n o t destroyed by harvesting (Tab.

2 80 TABLE 4.5

croup

characteris tics

I

F o r e s t s of c a t c h ments used f o r

Water E~Mgeme tn function

Timber production

superior

inferior

Piirpose

Exclude s o i l e r o s i o n , n o t

rmmicipal w a t e r

t o r e s t r i c t runoff , s a f e guard the water q u a l i t y

supply F o r e s t i n zones of

Ia

s a n i t a r y protec-

exceptional conditioned

t i o n of water quality Forests in

I1

balanced

Balance the runoff fluctuat i o n , p r o t e c t the land

upper catchmen ts

a p a i n s t erosion

111

111-1

protectinp

S o i l p r o t e c t i o n , r i v e r bed

canopy

IIIa IIIb

IIIc

s t a b i l i z a t i o n , bank protec-

Rank. canopy

e x r e n t i o n a l condi tioTed t i o n , s a n i t a r y p r o t e c t i o n

Canopy protectin:. loca 1 water

of l o c a l water resources, exceptional conditioned t r a n s f o m t i o n of s u r f a c e

resources I n f i 1t r a t i o n forest belts

water i n to groundwater runoff excepticnal conditioned

Cateporization o f f o r e s t canopy a s a function of i t s water wnagenient function according t o KreEmer and BPle (1975).

Pastures have s i m i l a r p o s i t i v e e f f e c t s , i f n o t destroyed by being o v e r n a z e d o r trampled d m by herds. The r e s i s t a n c e of c u l t i v a t e d f i e l d s a g a i n s t e r o s i o n

is s u b s t a n t i a l l y Imier. The a n t i - e r o s i o n e f f e c t s of the v e g e t a t i v e canopy have a favourable e f f e c t on the q u a l i t y o f t h e s u r f a c e water. Its high i n f i l t r a t i o n c a p a b i l i t y s i m i l a r l y influences the proundwater of eroded m a t e r i a l i n w a t e r in brooks, creeks

q u a l i t y . The decreased e r o s i o n decreases the volume , thereby reducinp the d u r a t i o n of water t u r b i d i t y

and r i v e r s

. The

seven times due t o d e f o r e s t a t i o n .

c o n t e n t of sediments m y increase f i v e t o

Also important a r e o t h e r changes i n water

281

TABLE 4.6 t / 106 b 2 / y r

l a n d use

8.5

Forest

85

Grassland Abandoned s u r f a c e mines

850

Cropland

1700

Harvested f o r e s t

4250

Active s u r f a c e mines

17 000

Construction

17 000

Relative to forest = 1

1 10 100 200 500

2000 2000

R e p r e s e n t a t i v e r a t e s of e r o s i o n from various land uses according t o Canter (1983) quality a f t e r

clearing,

caused by the

decay of orpanic

increased l e a c h i n g of nutriments: - the i n c r e a s e i n the c o n c e n t r a t i o n of n i t r i d e s e . g . from (Hubbard Brook - IJSDA F o r e s t S e r v i c e 1975)

-

m a t t e r and by t h e lmg/l t o 60-80 mg/l

the i n c r e a s e i n the phenol c o n c e n t r a t i o n t o 0.6 m g / l (Kyomiqe,

Hart e t . a l . ,

1981).

-

f i v e t o t h i r t y f o l d i n c r e a s e i n the calcium, mgnesium and

potassium content

i n t h e outtlow (Sopper, 1975). The i n f l u e n c e of a q r i c i i l t u r e and s i l v i c u l t u r e on f l o o d s , e r o s i o n and water q u a l i t y can be mnaged, i n p a r t i c i i l a r : ( a ) by the s e l e c t i o n of s u i t a b l e p l a n t s and woods and by the arrangement of r e l e v a n t c u l t u r e s and p l o t s , and of the c o m n i c a t i o n and drainage network, by s u i t a b l e c u l t i v a t i o n p r a c t i c e s , namely by ploughing a l o n g isohyets and horizontal f r i r r m s , by sowing without plouging, by the r e s t r i c t i o n of land c u l t i v a t i o n , by a r a t i o n a l crop r o t a t i o n , by

c i i l t i v a t i o n i n s t r i p s , by i n f i l t r a t i o n s t r i p s

arranged a l o n g water c o u r s e s , by the

p r o t e c t i v e c u l t i v a t i o n of g r a s s , by wind

b e l t s , i n f i l t r a t i o n and overshadowing of f o r e s t b e l t s , c u l t i v a t i o n of r i l l s , by t e r r a c e s , d i k e s , channels and by

p r o t e c t i n g t h e d e s t r u c t e d land s u r f a c e to

l i m i t erosion, ( b ) by measiires which l i m i t the compacting of the s o i l s u r f a c e and improve the s o i l q u a l i t y and humus content s o a s t o i n c r e a s e the r a t e and t h e degree of e x p l o i t a t i o n of mineral

fertilizers,

by the c u l t i v a t i o n o f r e s i s t e n t f o r e s t c u l t u r e s , which remain s t a b l e i n

(c) winds and d i f f i c u l t snow and i c e c o n d i t i o n s , by pref f e r i n g s e l e c t i v e and p a r t i a l c l e a r i n p , and by t h e inmediate r e c u l t i v a t i o n of c l e a r i n g s i n vast a r e a s .

282 4.3.3

Influence of the Vegetative Canopy on R a i n f a l l and Runoff

The roughness of the f o r e s t cover, higher i n comparison with deforested a r e a s , has an important influence on the p r e c e p i t a t i o n process. I t decreases the r a t e of motion of the lowest l a y e r of the atmosphere and causes turbulence of the a i r , thus improving t h e conditions f o r the condensation of t h e water vapour. This influence has been proved n o t only t h e o r e t i c a l l y ,

but a l s o s t a t i s t i c a l l y , hcw-

ever f o r extremely v a s t f o r e s t a r e a s only. Kalinin (1968) mentions t h a t the influence of l a r g e pine f o r e s t s increases the level of p r e c i p i t a t i o n by about

20% i n the sumner season and by some 8-10% i n winter. The impact of deciduous and mixed f o r e s t s can be estimated a t about one h a l f of the above values. The influence of spruce f o r e s t s is higher, assessed a t a roughly 30% increase i n p r e c i p i t a t i o n i n the sumner season i n comparison with deforested a r e a s . This positive influence on r a i n f a l cannot be considered i n a r e a s With s c a t t e r e d , rel a t i v e l y small f o r e s t s . I n a d d i t i o n t o t h i s , f o r e s t s increase h o r i z o n t a l p r e c i p i t a t i o n , depending on the a l t i t u d e and d i s t a n c e from the sea. F o j t and KreEmer (1976) estimated, f o r c e n t r a l European conditions and mountanuous humid a r e a s , the influence of f o r e s t s a s having a supplement of almost 400 mn t o the values of v e r t i c a l r a i n f a l l i n comparison with deforested a r e a s . Karpov (1962) estimated the value of annual h o r i z o n t a l p r e c i p i t a t i o n by a 13%increase i n the yearly t o t a l r a i n f a l l (Fig.

4.7). The influence of f o r e s t s on a i r motion has a remarkable e f f e c t on snowfall d i s t r i b u t i o n . Snow accumulates i n f o r e s t s t o the detriment of deforested p l o t s . Roughton1(1970) mentions the following fundamental p o i n t s : ( a ) Snow accumulates mainly i n small openings i n f o r e s t s , e s p e c i a l l y a t l m e r a l t i t u d e s . The optimum s i z e of opening f o r snow accumulation i s about one t o ten

times the h e i g h t of the surrounding f o r e s t cover. Targe openings do not have such a p o s i t i v e i n f l u e n c e because of the wind e f f e c t . (b) The e f f e c t of f o r e s t s on snowfall i s more a r e d i s t r i b u t i o n of the snow, r a t h e r than any o v e r a l l i n c r e a s e i n p r e c i p i t a t i o n . It appears a s a p o s i t i v e supplement t o the water balance i n smll catchments only. The r e d i s t r i b u t i o n of snow i n t o deeper f a l l s over smaller a r e a s attenu-

(c)

ates

t h e runoff from t h e melting of the s n m , thus decreasing the s p r i n g peak

discharges, Forests with i n t e r m i t t e n t deforested p l o t s have a favourable e f f e c t on extending the duration of t h e s n m melt. The decreased r a t e of melting c o n t r i b u t e s t o the good accurmilation and r e t a r d a t i o n function of f o r e s t s , m n i f e s t a t e d by a more s t a b l e regime of noundwater, springs and s u r f a c e water. The runoff from a f f o r e s t e d a r e a s is g r e a t l y influenced by the high evapotranspiration

of ecosystems , generally

exceeding t h e c o n t r i b u t i o n of the increased

2 83 precipitation.

The i n c r e a s e i n t h e t o t a l y e a r l y runoff from a f o r e s t e d a r e a s i n

comparison w i t h a r e a s without f o r e s t has been s t a t i s t i c a l l y determined only f o r extremely l a r g e catchments w i t h moderate e v a p o t r a n s p i r a t i o n a s a consequence of h i g h e r v e r t i c a l and h o r i z o n t a l p r e c i p i t a t i o n . I n the c a s e of small a f f o r e s t e d a r e a s a lower y e a r l y runoff has been statist i c a l l y documented i n comparison w i t h a r e a s of the same s i z e and c h a r a c t e r , but without f o r e s t s , a s a consequence of h i g h e r e v a p o t r a n s p i r a t i o n . ‘lc Arthur and Cheney (1965) have measured a n i n c r e a s e i n the t o t a l y e a r l y runoff of between 43 and 235 of t h e h y p o t h e t i c a l runoff of the a f f o r e s t e d catchnent a f t e r a f o r e s t f i r e . Higher values have been measured i n t h e f i r s t years

a f t e r a con-

f lagra tion. The v a l u e s of t h e i n c r e a s e i n the t o t a l y e a r l y runoff due t o d e f o r e s t a t i o n depend n o t only on the percentage of the r e d u c t i o n i n the f o r e s t cover and i t s type ( c o n i f e r o u s , deciduous, b u s h ) , but also on the t o t a l annual p r e c i p i t a t i o n and i t s state of

aggreqation ( F i g . 4 . 9 ) .

The impact of the s i l v i c u l t u r a l a c t i v i t i e s on the runoff c o e f f i c i e n t c depends on t h e following groups of f a c t o r s

(4.12)

c

=

L

-

S

1

-

s i l v i c u l t u r a l p r a c t i c e s and conservation s e r v i c e s , namely the s t a n d d e n s i t y ,

S2

-

ratio

IPS(L’S1,S*,

R1’R2,P)

s t a b l e l o c a l f a c t o r s , e s p e c i a l l y t h e drainage a r e a shape and s l o p e i , s o i l depth and type

s and eeology g ,

type and d e n s i t y o f f o r e s t r o a d s , movement and type of t r a n s p o r t mechanisms, and type of d e f o r e s t e d p l o t s , extending the d u r a t i o n of snow melting,

R1 - type of c u l t u r e , i t s r o o t system and the amount of biomass,

R2 - the r a t i o of middle-aged tree c l a s s e s , which have the h i g h e s t i n t e r c e p t i o n and t r a n s p i r a t i o n l o s s e s , P - the s t a t e of a g g r e g a t i o n of t h e p r e c i p i t a t i o n and i t s coincidence w i t h the season and s a t u r a t i o n p e r i o d s . The decrease i n r a t i o on t h e a r e a s u r f a c e by 30% i n dependence on o t h e r cond i t i o n s causes a n i n c r e a s e i n flood discharges of s i x times o r even more. The f a c t t h a t r a i n f o r e s t s are being destroyed by man a t the r a t e o f about llxl06ha every Rut

y e a r appears a l s o a s a warning i n t h i s connection. under c o n d i t i o n s of a n i n t e n s i v e f o r e s t e x p l o i t a t i o n and f o r e s t manage-

ment, the r a t i o of a f f o r e s t e d a r e a s is n o t the only d e c i s i v e f a c t o r of the water regime. This depends s u b s t a n t i a l l y on t h e depth of t h e s o i l , the age, s p e c i e s and c o n d i t i o n of the f o r e s t , and on c u l t i v a t i o n p r a c t i c e s (Tab. 4 . 7 ) . F u l l y a f f o r e s t e d a r e a s may have a n i n s u f f i c i e n t i n f l u e n c e t o balance the water regime as a consequence of wrong f o r e s t r y p r a c t i c e s which c o n c e n t r a t e the runoff.

To i n c r e a s e the t o t a l y e a r l y runoff from a f f o r e s t e d areas where spruce i s the main wood, without i n c r e a s i n g the flood d i s c h a r g e s , P e r i n a and Krecmer (1973)

2 84 TABLE

Class

4.7

Years

Clearing period 100 years decreased f o r e s t density

Clearing period 120 years f u l l f o r e s t density

Area

Area

Biomass Annual water concen- consumption t r a tion

CX) I. 11. 111.

IV V. VI. I

(&.ha-’)

0-20 20-40 40-60

20

1.0

20 20

0.8

60-80

20 20 0

0.8

80-100 1oc-120

T o t a l annual consmpti on

100

0.8

0.9 0.0

-

3 60 520

(XI

Biomass Annual water concen- consumption tration factor (2.ha-l)

10

1.0

180

20

1.0

560 800 720

730 670

20

1.0

20

1.0

560 0

20 10

1.0 1.0

2 60

2840

100

-

3300

600

The impact of f o r e s t density ( b i o m s s concentration measured i n t per hectare and compared with theoretical values of f u l l density according t o Schwabach (1890) on t o t a l annual runoff. Pine f o r e s t i n area with t o t a l annual r a i n f a l l 1200 mm. r e c m e n d the following biotechnical measures : ( a ) The c u l t i v a t i o n of f o r e s t s with a low stand density i n areas with low horizontal p r e c i p i t a t i o n i n order to decrease the interception losses. (b) To increase the r a t i o of younger tree classes and the r a t i o of clearing (openina) surfaces, and to l i m i t the r a t i o of the middle-aged t r e e classes, which have highest interception and transpiration losses, i . e . to shorten o r to extend the period of clearing i n areas with low horizontal p r e c i p i t a t i o n . ( c ) The change of tree species i n areas with low horizontal p r e c i p i t a t i o n , i .e. t o replace species with high interception and transpiration losses with species which have low interception and transpiration, to s u b s t i t u t e deciduous trees f o r spruces. (d) A considerable increase i n the r a t i o of the old spruce forests i n areas with high horizontal p r e c i p i t a t i o n and high stand density, and a decrease i n the r a t i o of the youngest growth and clearings destined f o r a f f o r e s t a t i o n . ( e ) The deforestation of s u i t a b l e areas i n accordance with the planned extension of the cultivated land, pastures , towns, industry and recreation development

.

The runoff c o e f f i c i e n t on a g r i c u l t u r a l lands depends on the cultivated species, t h e i r r o o t system: deep, shallow, i n t e r m i t t e n t , surface e t c . , t h e i r stage of

285 TABLE 4.8 Month

4

5

6

7

a

9

10

Grass land

6

13

37

li

12

16

16

Winter r y e

2

4

0

0

0

3

25 24

8

Spring wheat and b a r l e y Po t a toes

17 10

16

0

0

0

0

2

9

26

30

14

The impact of f i e l d crops on water accumulation i n s o i l (%) according to Rulavko (1971). Erowth and on the course of the p-owth depending on the s o i l thickness and type, the aRricultiira1 p r a c t i c e s and the s t a t e of aggregation of p r e c i p i t a t i o n . Measurements on a g r i c u l t u r a l s o i l s docment a considerable l o s s of water accumulat i o n i n comparison with s a s s l a n d , whose value depends on the season (Tab. 4.8). The change of pastures with a deep r o o t system i n t o a g r i c u l t u r a l f i e l d s m y r e s u l t i n a 30% i n c r e a s e i n the t o t a l yearly r u n o f f , when the r a i n f a l l occurs mainly i n the vepetation period. Also important a r e a g r i c u l t u r a l p r a c t i c e s : crop r o t a t i o n , weed removal, the depth and period of ploughing, a g r i c u l t u r a l c o m e r vation s e r v i c e s . h o w i t c h (1968)

shows t h a t deep ploughing can decrease the

y e a r l y runoff depending a l s o on the r a i n f a l d i s t r i b u t i o n by sme 25 t o 75%. Nevertheless compacting of t h e deeper soil l a y e r s by heavy t r a c t o r s and o t h e r a g r i c u l t u r a l machinery increases the s u r f a c e runoff. The i n t e n s i f i c a t i o n of a p r i c u l t u r a l production, r e s u l t i n g i n a n increased yield: - is either

accompanied by a growing evapotranspiration, enabled by an increa-

sed i n f i l t r a t i o n r a t e and higher moisture content i n the r o o t zone due t o a g r i c i i l t u r a l p r a c t i c e s loosening the s o i l l a y e r , thus l i m i t i n g the interflow and decreasing the recharpe of the groundwater, which r e s u l t s i n a decrease i n the t o t a l annual runoff and a decrease i n low discharges i n water courses, - o r caused by b e t t e r u t i l i z a t i o n of water by p l a n t s . I n t h i s second c a s e , the change ( i n c r e a s e o r even decrease) of the evapotransp i r a t i o n is less important, because the i n f i l t r a t i o n r a t e enables a n adequate recharge of groundwater and hemp has no s i g n i f i c a n t impact on the t o t a l annual runoff.

The impact of a g r i c u l t u r a l a c t i v i t i e s on the runoff c o e f f i c i e n t depends on four groups of f a c t o r s

c = c

-

f a ( L , A, R, P

runoff c o e f f i c i e n t

(4.13)

286 L

-

s t a b l e l o c a l f a c t o r s , e s p e c i a l l y the drainage a r e a shape and slope i , s o i l depth and typp d , geology g ,

A - a g r i c u l t i i r a l p r a c t i c e s and conservation services, e.g. contour or o t h e r

method of ploughinp, i t s depth and p e r i o d ,

R - p l a n t s p e c i e s , the depth and type of t h e i r r o o t system, the i n t e n s i t y of c u l t i v a t i o n , e.g. the y i e l d - b i o m s s r a t i o , P

-

the p r e c i p i t a t i o n aggregation, occurrence, i n t e n s i t y , d u r a t i o n and coincidence with p l a n t growth, s o i l processing and s a t u r a t i o n periods e t c .

TABLE 4.9

Area

Decrease i n t o t a l annual runoff

steppe ( c u l t i v a t e d land) F i e l d s and f o r e s t s Southern edpe of f o r e s t s

66 - 74 40 - 66 20 - 40

The decrease i n t o t a l annual runoff a s a r e s u l t of deep ploughinp of f i e l d s , expressed a s a percentage of o r i p i n a l v a l u e s , according to h o w i t c h (1965). The s e l e c t i o n of the p l a n t s p e c i e s and v a r i e t y a l s o depends on a g r i c u l t u r a l p r a c t i c e s and on the p o s s i b i l i t y of conservation s e r v i c e s , which have a b a s i c impact on the runoff c o e f f i c i e n t . An e v a l u a t i o n o f the i n f l u e n c e of the v e g e t a t i v e canopy on runoff leads to the following conclusions: ( a ) The consunption of water by p l a n t a t i o n s , f o r e s t s and o t h e r p l a n t n i t i e s depends m i n l y on the amount a v a i l a b l e i n the s o i l .

COIITTNJ-

(h) P l a n t ccmnunities of t h e same e c o l o g i c a l o r d e r use approximately equal volumes of water. Fast-prowing tree s p e c i e s do n o t u s e more water than slow m m i n p ones. (c)

Tne decrease i n the volume of t h e biomass i n c r e a s e s the t o t a l y e a r l y

runoff i n the same way a s the change of deep-rooted s p e c i e s i n t o s h a l l o w r o o t e d ones. ( d ) Tne a f f o r e s t a t i o n of prassland o r c u l t i v a t e d land decreases both s u r f a c e runoff and i n f i l t r a t i o n i n t o the groundwater. ( e ) The chanpes of the water regime a s a consequence of t h e f o r e s t and a g r i c u l t u r a l p r a c t i c e s a r e heteroEeneous and depend on s o i l , geomorphological and climatological conditions.

?he v e g e t a t i v e canopy a l s o has a s i g n i f i c a n t i n f l u e n c e on t h e a l t i t u d e of the moundwater t a b l e . A developed f o r e s t can cause i t to drop to sane ten meters

287

below the land s u r f a c e . Clearinp and thinning r e s u l t s i n a rise i n the groundwater t a b l e , depending on the geomorphological , hydrogeological, c l i m t o l o g i c a l and s o i l conditions. The deep r o o t system of the f o r e s t cover takes o f f the water from the lower s o i l l a y e r s . A f t e r c l e a r i n g a f o r e s t t h e groundwater table may r i s e over the land s u r f a c e . Such a r i s e , i n the case of low water q u a l i t y o r i f the water rises through s a l t y l a y e r s , a f f e c t s the q u a l i t y of the s o i l , inc r e a s i n g its s a l i n i t y . INFLIJENCE OF URBANIZATION AND IND~JSTRIALI7ATION

4.4

Urbanization and i n d u s t r i a l i z a t i o n influence a l l t h e f a c t o r s i n the equation

( 4 . l o ) , determining peak discharpes QmX, t o t a l runoff Q , minimum discharges -erosion i n t e n s i t y I,, groundwater regime G , water q u a l i t y q and the t o t a l r a i n f a l l P i . e . climatological f a c t o r s Xc, the f a c t o r of the vegetative canopy Xv, s o i l f a c t o r X,, morphological f a c t o r G, geological f a c t o r X,, and the water management f a c t o r X ,.

amin,

3

2

min Q r w 1

4

5

6h

Fig. 4.3. 'The increase i n flood discharges a s a consequence of urbanization: P - r a i n f a l l curve, Q - r i v e r discharge, W - detention s t o r a g e and water accumulation i n the s o i l l a y e r , C, soundwater accumulation, A accumulation i n the seweraEe network. P = Wo + Go = W, + Ax + G,. IMXF'X maxPo; tp. >ho;

-

-

minQx

< rninQo; (& < Go;

tqx

< tqo;

ql0...

q,

0, - mean annual discharge

( m 3 . s-l)

e

-

ss

-

s

s h a r e of the eroded m a t t e r forming the suspended and wash load

( < 1)

s h a r e of the suspended load t h a t has n o t s e t t l e i n the mediate r i v e r s t r e t c h

(< 1 )

% 100 W

5 3

J

0

> 80

-

[L

0

> a w

v)

W

60

[L

40 60

50

40

30 20 D I S T A N C E FROM D A M

FiR. 4.16 Geographical r e p r e s e n t a t i o n of sediment d e p o s i t i o n i n r e s e r v o i r s and the decrease i n s e t t l i n g r a t e . Sediments are b u i l t up t o a n e l e v a t i o n dependinp on s l u i c i n g l e v e l , b u t channel i s maintained through t h e s e . Mo - monolimnion, ce - c i r c u l a t i o n i n epilinmion. I t i s very important from the o p e r a t i o n a l p o i n t of view t h a t the r a t e of s t o r a g e reduction i s h i g h e r i n t h e i n i t i a l period of t h e r e s e r v o i r ' s operation

314 and depends on t h e g r a i n s i z e d i s t r i b u t i o n (Fig 4.15,. The bed load and coarse f r a c t i o n s of t h e suspended load a t t h a t time e n t e r t h e upper parts of t h e s t o r a g e only, reducinr: f i r s t the v o l m e of t h e s t o r a g e zone reserved f o r flood c o n t r o l and then, i n t h e second s t a g e , a l s o t h e conservation s t o r a g e . IJnder t h e s e circums t a n c e s only f i n e f r a c t i o n s a r e a b l e t o reach t h e i n e f f e c t i v e p e m r e n t s t o r a g e . For rivers with a r e g u l a r sediment t r a n s p o r t t h e coiirse of t h e decrease i n t h e t o t a l s t o r a g e may be considered a s l i n e a r : Vt

=

vy .

t

(m

3

(4.27)

I n t h e t h i r d phase o f t h e s t o r a g e reduction p r o c e s s , t h e movement o f t h e bed load reaches t h e i n e f f e c t i v e permanent s t o r a g e and then t h e dead s t o r a g e , decr e a s i n g the r a t e of reduction i n t h e a c t i v e ( f l o o d c o n t r o l and conservation) s t o r a g e . In t h e f o u r t h phase, t h e sediment t r a n s p o r t

e n t e r s t h e storaEe and t h e

space of t h e dynamic i n f l u e n c e of t h e t u r b i n e s , o u t l e t s and s p i l l w a y s , r e s u l t i n g i n a f u r t h e r d e c r e a s e i n t h e r a t e of diminuation o f the r e s e r v o i r volume ( F i g .

4.16). The rate o f s t o r a g e reduction by sedimentation depends e s p e c i a l l y on t h e proper design o f a p r o j e c t . Depending on t h e sediment t r a n s p o r t regime and on the requirements on r e s e r v o i r and dam o p e r a t i o n , a n optimum d e s i g h , i . e .

-

t h e s i z e of t h e reservoir and

-

a l a y o u t of t h e p r o j e c t ,

can be s e l e c t e d and r e a l i z e d i n such a manner t h a t almost no suspended and wash load i s k e p t back, w h i l s t s t o r i n g water i n t h e r e s e r v o i r . I n such a way only t h e t r a n s p o r t of t h e bed-load c o n t r i b u t e s t o t h e s t o r a g e reduction. The sedimentladen water o f t h e e a r l y flood is passed through low-level openings. This condit i o n r e q u i r e s a r e l a t i v e l y shallow r e s e r v o i r and a r e l a t i v e l y s h o r t r e s e r v o i r lake, n o t f i l l e d except i n l a t e f l o o d , when the flood water contains l e s s sediments. The dynamic i n f l u e n c e o f r e l e v a n t s p i l l w a y s and o u t l e t s must reach t h e sediment f l m . Their capacity, arrangement and r e l e v a n t o p e r a t i o n With t h e g a t e s

must n o t permit a d i v i s i o n of t h e s t r e a m l i n e , r e s u l t i n g i n a reduction i n t h e t r a c t i n g f o r c e s . An a p p r o p r i a t e s i z e , lay-out and equipment of t h e p r o j e c t ena b l e s t h e r e s e r v o i r t o i n t e r f e r e t o some 10%w i t h t h e regime of r i v e r s with a high level of suspended m a t t e r t r a n s p o r t , thus g r e a t l y c o n t r i b u t i n g t o t h e efficiency of the project. Other c o n t r o l measures can be grouped i n - c o n t r o l o f watershed (proper soil conservation, farming and f o r e s t i n g techniques, p r o t e c t i o n of r i v e r banks e t c . )

-

c o n t r o l o f inflow (by s e t t l i n g b a s i n s , by-pass c a n a l s , p r o v i s i o n of v e g e t a t i v e

screening, favourable l o c a t i o n of i n t a k e s t r u c t u r e s f o r off-channel reservoirs etc.)

315 -

removal of d e p o s i t s ( f l u s h i n g , s l u i c i n g , dredging, which i s economic i n

exceptional cases o n l y ) . The decrease i n r e s e r v o i r volume n o t only resLlts f r a n the sediment of the r e s e r v o i r ' s t r i b u t a r i e s , h u t also from the f a l l - o u t from t h e atmosphere, plankton,

washed up s o i l and a g r o c h m i c a l p a r t i c l e s from the a d j o i n i n p s h o r e s and

m a t e r i a l frcm the eroded r e s e r v o i r banks. The abrasion and l a n d s l i d i n g of shores

is a process of t h e i r d e s t r u c t i o n which is caused by the e f f e c t of water, wind, by the f l u c t u a t i o n of the water t a b l e , h y water flow, by the e f f e c t of waves and i c e and by the e f f e c t of human a c t i v i t i e s .

H

(rn)

0

time 100 O/O

Fig. 4.17. The e r o s i o n of r e s e r v o i r shores i n r e l a t i o n t o the f l u c t u a t i o n of the s t o r a g e l e v e l . z e d r a f t e d accordinp to Bayer ( 1 0 5 4 ) , 3 - pond l e v e l , F',axP intx-imim water l e v e l , A - a b r a s i o n s h o r e , l3 - s!iding a b r a s i o n s h o r e , C - shore with aCcUmUlation .Of sediments, B+C - a b r a s i o n and a c r i ~ r ~ i i l a t is~hno r e s .

An important d e s t m c t i v e e f f e c t is e x e r t e d e s p e c i a l l y by v a r i a b l e phenomena. The abrasion of the shores of a r e s e r v o i r starts s h o r t l y a f t e r the f i r s t f i l l i n g - u p of t h e r e s e r v o i r . The r a t e of t h i s process i n c r e a s e s step-by-step years of o p e r a t i o n , reaching a peak a f t e r

i n the f i r s t

sane t h r e e t o f i v e years and then

gradually, d e c r e a s i n g a g a i n . I n t h i s phase, t h e shape of the shores almost reaches a s t a t e of geomechanical equilibrium. The w e t t i n g of t h e shores r e s u l t s i n a change i n t h e i r geomechanical charact e r i s t i c s , e s p e c i a l l y i n t h e i r cohesive s t r e n g t h and c o e f f i c i e n t of f r i c t i o n .

New f o r c e s a c t i n g on t h e wetted m a t e r i a l d e s t r o y t h e o r i g i n a l balance, which may, under unfavourable geomorphological c o n d i t i o n s , a l s o r e s u l t i n the s l i d i n p of whole rock formations. Depending on t h e s l o p e of the s h o r e s , t h e i r exposure, t h e i r geological and s o i l c h a r a c t e r i s t i c s and t h e i r v e g e t a t i v e canopy, t h e r e s u l t of the process on

316 the shore formation a r e - abrasion w a t e r s i d e s , generally having a s t e e p s l o p e , whose m a t e r i a l i s eroded, transported and then deposited (Fig. 4,17 A) - abrasion and s l i d i n g watersides, when the change of gemechanical f a c t o r s r e s u l t s i n l a n d s l i d i n g (Fig. 4 . 1 7 B)

- accumulation w a t e r s i d e s , formed i n f l a t a r e a s , e s p e c i a l l y i n shallow coves, where t h e m a t e r i a l f r m t r i b u t a r i e s was deposited by wave a c t i o n (Fig. 4.17 C) - abrasion and accumulation watersides, which a r e s t e e p , with a platforni formed by the eroded m a t e r i a l . Abrasion phenomena do not occur whenever the slope of the shore is h e l m 3'. TJnder such conditions the a c t i n g f o r c e s , because of t h e i r almost p a r a l l e l direct i o n , a r e n o t a b l e t o destroy the surface l a y e r . E f f e c t of Reservoirs on Water Qliality

4.6.3

The sedimentation process i n a r e s e r v o i r i s accompanied by many o t h e r physic a l , chemical and b i o l o g i c a l processes of s e l f - p u r i f i c a t i o n , which causes mixing and thinning. 'The influence of the water l e v e l f l u c t u a t i o n on t h e mean conc e n t r a t i o n of dissolved m a t t e r i n the r e s e r v o i r can be determined on the b a s i s of the following formula (4.28)

q,,

qo

vt,

Vo

- concentration of dissolved m a t t e r i n t h e moment 0 and to

0

t t

- volume of s t o r a g e i n the moment 0 and to

(m )

(m3 )

- concentration of dissolved matter i n the inflow water

-

outflow frcm t h e r e s e r v o i r i n the period from

1-5

3

Q t - water inflow i n the period from 0 t o t-1

k

(g.

(g.1-l)

0 t o t-1 (m3 )

I n t h i s formula a constant concentration of outflcw is assumed during the period i n question. Chemical and b i o l o g i c a l processes, running simultaneously with the physical processes, r e s u l t i n ( a ) t h e m i n e r a l i z a t i o n of organic matter ( b ) t h e production of new organic matter. Some chemical substances, e . g . c h l o r i d e s , do n o t change durinp these self-puri-

f i c a t i o n processes. T h e i r concentration depends then on the r a t e of water exchange. The concentration of o t h e r m a t t e r increases o r mostly decreases and can thus be expressed by a dropping exponential function, e.g. i n sumnary by means of t h e b i o l o g i c a l oxygen demand BOD. The course of the p h y s i c a l , chemical and b i o l o g i c a l processes

is influenced

317 n o t only by t h e i n p u t of sediments, b u t a l s o by the i n p u t of s o l a r energy and by t h e oxygen and carbon d i o x i d e from the a i r . The content of o r g a n i c m a t t e r depends on the r a t e of the m i n e r a l i z a t i o n processes and on the production of o r g a n i c matter. The dependence of the c o n c e n t r a t i o n of organic m t t e r i n the outflow on t h e rate of water exchange i s hyperbolic. This concentration depends on the c o n c e n t r a t i o n of t h e organic matter i n the inflow, on the average water depth, on the b i o l o g i c a l oxygen demand ROD5 i n the r e s e r v o i r and on the r a t e of t h e water exchange. According t o Stragkrabovs (1976)

q t - c o n c e n t r a t i o n of o r g a n i c m a t t e r i n t h e outflow

-

qr

c o n c e n t r a t i o n of non-disintegrable matter

qo - c o n c e n t r a t i o n o f o r g a n i c m a t t e r i n inflow

te

-

r a t e of water exchange i n t h e r e s e r v o i r

h

-

p

- ROD^

mean depth of the r e s e r v o i r prodiiction i n the r e s e r v o i r

(mg.R3D5.1-') (ma. I-') (mg . 1-l) (days) (m)

(g.m

-2

per day)

'The r a t e of m i n e r a l i z a t i o n process i n r e s e r v o i r s with a high r a t e of water exchange i s h i g h e r than t h e production of organic m a t t e r during t h e f i r s t f i v e days a f t e r the inflow of o r g a n i c matter. I n shallow r e s e r v o i r s , with a depth d a m t o 5 m and a r a t e of water exchange i n excess o f 20 days, the production of o r g a n i c m a t t e r exceeds the r a t e of m i n e r a l i z a t i o n . A s h o r t e r r a t e of water exchange r e s u l t s i n a h i g h e r decomposition r a t e . The longer r a t e of water exchange r e s u l t s i n an i n c r e a s e i n c o n c e n t r a t i o n o f organic matter i n t h e outflow i n comparison with t h e inflow, e s p e c i a l l y when t h e BOD c o n c e n t r a t i o n i n t h e inflow 5 is lower. The c o n c e n t r a t i o n of organic matter i n the outflow depends on t h e r a t e of production of t h e o r g a n i c m a t t e r i n comparison w i t h t h e rate of t h e mineralizat i o n process:

(4.30)

- r a t e of o r g a n i c production qP qm - r a t e of t h e m i n e r a l i z a t i o n process

(ma.

. 1-l)

(mg. 1-l)

For longer p e r i o d s of water exchange than 14 t o 16 days t h e s h a r e of dis-

318 Sediment

Fig. 4.18. The impact of thermal s t r a t i f i c a t i o n and operation with spillway g a t e s , bottom and inedirm o u t l e t s on water q u a l i t y i n r s e r v o i r . River flow t l , t2 and water c i r c u l a t i o n c during s t a g n a t i o n , c i r c u l a t i o n ch during t h e period of homothemicity i s dotted. The seasonal changes i n thermal s t r a t i f i c a t i o n .

i n t e g r a t e d organic matter does not depend on t h e depth of t h e r e s e r v o i r . The e f f i c i e n c y of t h e mineralization process increases with t h e duration of t h e water exchange and i n r e s e r v o i r s with a r a t e of water exchange of 14 t o 1 6 days increases s u b s t a n t i a l l y with t h e i r averape depth. The upper l a y e r s of t h e r e s e r v o i r a r e trophogemc, i .e. n u t r i t i v e . Assimilation

is t h e i r p r e v a i l i n g process, while d i s s i m i l a t i o n occurs only p a r t i a l l y . Lmer layers a r e t r o p h y l i t i c , i . e . they support the d i s i n t e g r a t i o n of organic matter. The p r e v a i l i w process there is d i s s i m i l a t i o n , when d e s t r u e n t s d i s i n t e g r a t e t h e dead plankton and o t h e r dead organisms. Owing t o the water flow a c e r t a i n development of p h y s i c a l , chemical and h i o l o g i u l processes is observed from the estuary of t r i b u t a r i e s t o t h e dam. The r a t e of t h e r e l e v a n t biochemical processes depends l a r g e l y on the course of water tenperatures. The u n i t mass of water depends on t h e temperature, chemi-

cal composition and content of sediments and r e s u l t s i n thermal s t r a t i f i c a t i o n . The p a t t e r n of t h e m 1 s t r a t i f i c a t i o n i n r e s e r v o i r s depends on t h e

- r e s e r v o i r depth and geometry - s o l a r r a d i a t i o n and a i r temperature - wind v e l o c i t y - r e s e r v o i r o p e r a t i o n , i . e . on t h e flow t o volume r a t i o .

319 The degree of s t r a t i f i c a t i o n depends on tlie densimentric Froude number Fr which can be approximated by

(4.31)

T,

-

PI

- mean r e s e r v o i r depth

Q

-

v

- reservoir volme

r e s e r v o i r lenptk discharge

According t o Canter (1983) i f F r i s less than

1 E ,

s t r a t i f i c a t i o n is expected,

with the depree o f s t r a t i f i c a t i o n i n c r e a s i n g with the d e c r e a s i n p densimetric Froude number. The thermal s t r a t i f i c a t i o n i n r e s e r v o i r s is more marked i n deeper r e s e r v o i r s . The d i f f e r e n c e i n temperature between t h e s u r f a c e and t h e bottom l a y e r s may exceed 15OC diirine high siimner and 10°C diiring s p r i n p . This d i f f e r e n c e i s about 4-5OC d u r i n g w i n t e r .

Temperature g r a d i e n t s , i . e . t h e d i f f e r e n c e of temperature i n t h e v e r t i c a l d i r e c t i o n , a r e n o t regiilar. Idhen t h e temperature regime i s s t a b l e , a c h a r a c t e r i s t i c zone c a l l e d t h e m e t a l i m i o n o r thermoclina occurs a t a depth of some 5 t o

15 m. I t s thickness v a r i e s and may even reach 6 m. This l a y e r i s c h a r a c t e r i z e d by a quick decrease i n water temperature with t h e depth, e x c e p t i o n a l l y reaching 8OC a t 0.3 m. (Fig. 4.18

T5e upper l a y e r , above t h e m e t a l i m i o n , is t h e epilimnion, where t h e e f f e c t s of s o l a r r a d i a t i o n a r e i n t e n s i v e , e s p e c i a l l y i n the sumer season. This l a y e r extends t o a depth of some 4 t o 15 m. I n t h i s l a y e r , t h e stock of oxyEen is supplunented from t h e atmosphere by d i f f u s i o n as w e l l a s by t h e photosynthesis of t h e water organisms. During the s u m e r season the water temperature of this upper l a y e r is h i g h e r , and i n w i n t e r larder, than the temperature of the lowest l a y e r , the hypolimnion. The temperature of t h e s u r f a c e of t h e epilimnion is decreased from t h e s u r f a c e by evaporation, thris causing an upward flow of water. The wind p r e s s u r e on t h e water s u r f a c e r e s u l t s i n a t u r b u l e n t flow, catisinp tog e t h e r with t h e water inflow from t r i b u t a r i e s a mixing of water and a downward t r a n s f e r of h e a t and k i n e t i c energy. The changes of water q u a l i t y may r e s u l t i n t h e c r e a t i o n of a c m p a r a t i v e l y h e a v i e r , c o o l e r l a y e r a t t h e r e s e r v o i r bottom, enriched by products from the m i n e r a l i z a t i o n and decomposition processes. The chemical composition of t h i s l a y e r causes t h i s water t o reach i t s h i g h e s t d e n s i t y a t a temperature s l i g h t l y above 4OC. This l a y e r , the monolimnion, mostly does n o t take part i n the process of water c i r c u l a t i o n . Jmcal c i r c u l a t i o n flows may occur i n any p a r t of the reservoir, b u t the overa l l c i r c u l a t i o n is a r e s u l t of the d e s t r u c t i o n of t h e balance which arises from

320 s t r a t i f i c a t i o n by e x t e r n a l forces. The p r o b a b i l i t y of the occurrence of an overturn i s , t h e r e f o r e , g r e a t e r a t the time of a non-marked s t r a t i f i c a t i o n . This time occurs mostly i n s p r i n g o r autumn, when the upper and lmer l a y e r s oE the r e s e r v o i r have the s m e temperature, i . e. during the pcriod of homothemicity (Fig. 4 . 1 9 ) . Such a s t a t e occllrs once o r s e v e r a l times during s p r i n g o r autumn. During these periods of s p r i n g and a\itumn c i r c u l a t i o n , the flow caused by the wind e f f e c t mixes the whole vollme of the r e s e r v o i r , mostly with t h e exception of t h e monolimnion.

300

0

0 4

3;

0

30°C

SPRING STAGNATION

HOMOTHER-

STAG NAT I ON

MlClTY

7

0

(:I

C

0.06 -

20

(mg. I-’)

0.f

0..2 0,3

,

100 200 300

I7 BENTHOS

20 (mg. 1-t)

Fig. 4.19. Seasonal changes i n thermal s t r a t i f i c a t i o n i n deep r e s e r v o i r s . Oxygen content and o t h e r q u a l i t y i n d i c a t o r s depend on depth and r e s e r v o i r operation (x). According t o Chen and Orlob (1980). I n s u m e r and a l s o during w i n t e r , when the r e s e r v o i r is not covered by ice, winds cause water c i r c u l a t i o n i n the l a y e r of the e p i l h i o n only. During these periods of s t a g n a t i o n , the h e a t balance of t h e r e s e r v o i r is influenced by the h e a t exchange between t h e b o t t a n and water and by the h e a t i n p u t o r output from the water l e v e l o r ice cover, i . e . n o t by o v e r a l l water c i r c u l a t i o n . The motion

of the suspended matter, t h e i r f l o a t i n g and sedimentation, depends on these

32 1 c i r c i i l a t i o n phenomena. I n s i i m e r w a t e r from t r i b i i t a r i e s , iisiially c o o l e r than the water i n the res e r v o i r , p e n e t r a t e s below t h e warn epilimnion, follovin,c the d i r e c t i o n of the o r i g i n a l r i v e r channel. Diirinp t h i s season the water t e w e r a t r i r e in a s i n g l e , deep man-made l a k e is comparatively h i g h e r than i t would be i n a n a t u r a l lake iinder the same topographical and c l i m a t o l o g i c a l c o t d i t i o n s . The outflow of the c o o l e r water frmi t h e hypolimnion through tiirbines i n a n i n c r e a s e i n t h e .average t m p e r a tiire

,2f

and bottom o i i t l e t s results

tt:e r e s e r v o i r .

Diiring w i n t e r , t h e bottmi o u t l e t s and turbines r e l e a s e water which i s warmer i n comparison w i t h the upper l n y p r s , r e s u l t i n g i n a decrease i n t h e water temper a t i i r e . The average water temperature of man-made lakes i s . diiring the winter season, t h e r e f o r e lower than t h a t of n a t u r a l lakes. F l m conditions r e s u l t i n g from t h e inflow of t r i b u t a r i e s a r e s i i b s t a n t i a l l y more complicated as CornFred with the simple p e n e t r a t i o n of the c o o l e r infloKbelow t h e equilibrium i n s u m e r . A f t e r the s p r i n a c i r c u l a t i o n a s u b s t a n t i a l l y l m e r flow occurs i n the r e s e r v o i r . The s i t i i a t i o n i s quite d i f f e r e n t i n a cascade of man-made lakes. The temperat u r e i n t h e second and f u r t h e r r e s e r v o i r s is g r e a t l y influenced by the i n p u t of

cool water from the iipper r e s e r v o i r . I t changes n o t only v e r t i c a l l y , biit a l s o i n the l o n g i t u d i n a l p r o f i l e . The average of t h i s temperatiire, and the temperature of the s u r f a c e l a y e r , is also lower than i t would be i n a n a t u r a l lake under si mi l ar conditions. The s u r f a c e temperatures and of ten also average temperatures reach t h e i r minimum i n summer j u s t damstream of the upper clam. The l o c a t i o n of a r a p i d inc r e a s e i n temperature, corresponding t o a drop of the streamline and the forrnat i o n of a n epilimnion, changes w i t h t h e values of inflow from the upper r e s e r v o i r . Increased discharges u p s e t the ups trearn zone of the metalimnion i n t h e d i r e c t i o n of the flow and extend the zone with low s u r f a c e temperatures, thus r e s t r i c t i n g the p o s s i b i l i t i e s of bathing. For s i m i l a r reasons, the s u r f a c e tern p e r a t u r e decreases i n t h e d i r e c t i o n of the main flow downstream of the upper reservoir. The q u a l i t y of water i n r e s e r v o i r s is determined by the i n t e r p l a v of

-

the water exchange r a t e ,

-

t h e q u a l i t y of water e n t e r i n p the r e s e r v o i r , the climate and weather,

-

-

-

the hours of sunshine, the r e s u l t i n g water temperature, the morphological c h a r a c t e r i s t i c s of t h e r e s e r v o i r , e s p e c i a l l y i t s depth, the m a t e r i a l of t h e r e s e r v o i r b o t t m , t h e a q u a t i c ecosystem and ecosystem of the surroundings the impact of human a c t i v i t i e s . The q u a l i t y of t h e water e n t e r i n g the r e s e r v o i r varies considerably with the

322 season, being considerably influenced i n dry periods by t h e qtiality of e f f l u e n t s from i n d u s t r i a l and a g r i c u l t u r a l e n t e r p r i s e s . I n a r i d c o u n t r i e s , the s a l i n i t y of t h e inflow may i n c r e a s e considerably i n t h i s period. I n high-flow periods, the q u a l i t y of t h e inflow depends t o a g r e a t e x t e n t on the erosion r a t e , i . e . on the m a t e r i a l of t h e riverbed and wash from ciiltivated and f e r t i l i z e d land, depending

on the season, a g r i c u l t u r a l p r a c t i c e s and on the r a i n f a l l i n t e n s i t y .

The s e l f - p u r i f i c a t i o n process i n r e s e r v o i r s with the exception of sedimentat i o n is negatively influenced by t h e g r e a t e r depth of water, r e s u l t i n g i n lower oxygen content and lower temperature i n canparison with the o r i g i n a l conditions of the riverbed. Reduced flow v e l o c i t i e s r e s u l t i n higher sedimentation with a lonp period of s e t t l i n g , hence reducing the t u r b i d i t y of water. The increased d e t e n t i o n time leads t o increased b i o l o g i c a l a c t i v i t y . A higher nitrogen content, e n t e r i n g the r e s e r v o i r mainly a s a r e s u l t of wrong c u l t i v a t i o n p r a c t i c e s , and higher s u r f a c e temperatures with slmer watcr flow i n the epilimnion r e s u l t i n the over-development of a l g a e . The decay of these organisms causes secondary p o l l u t i o n , decreasing the oxygen c o n t e n t , poisoning o t h e r organisms and d i s n i p t i n p t h e b i o l o g i c a l balance. Serious t r o u b l e may be caused by the over-development of weeds i n t h e shallow p a r t s of the r e s e r v o i r . ' h e t h e m 1 s t r a t i f i c a t i o n r e s u l t s i n t h e forma t i o n of zones of d i f f e r i n g water q u a l i t y (Fig. 4.19).

These zones d i f f e r not only chemically, but a l s o i n t h e

content of various water organisms and can be modelled mathematically (Fip.4.20). The hypolimnion may be, and the monolimnion c e r t a i n l y is characterized by anaerobic

conditions and high concentrations of iron Fe, manganese rln and s i l l -

phides; t h i s causes q u a l i t y deterioration, e s p e c i a l l y during the n a t u r a l autumn overturn o r during excessive water withdrawals. This d e t e r i o r a t i o n may occur a s a low level of dissolved oxygen, high Fe, 'ln and hydrogen siilphide concentration and i n o r g a n i c and inorganic tastes and odours. \ h e n a cool water input o r c i r c u l z t i o n does n o t destroy the n a t u r a l t h e m 1 s t r a t i f i c a t i o n , a decrease i n the oxygen content of the epilimnion occurs i n the

s m e r season. During t h a t period t h i s l a y e r l o s e s , w i n g t o c i r c u l a t i o n , up to

50% of the oxygen content acquired i n s p r i n p . The c h a r a c t e r of the biochemical changes i n the water q u a l i t y i n the e p i l i m nion depends mainly on the course and type of processes, e s p e c i a l l y those which occur i n the sumner season. Nutriments e n t e r the f r e e space of t h e r e s e r v o i r , a l s o from i t s bottom, by means of the c i r c u l a t i o n , thus c o n t r i b u t i n g t o the a c t i v a t i o n o f the b i o l o g i c a l process. Oxygen l o s s e s a r e balanced by t h e decrease i n temperature i n autumn. The hypolimnion, having no c o n t a c t with t h e atmosphere, loses i t s Oxygen content a s a r e s u l t of decomposition processes, which occur e s p e c i a l l y i n the bottom sediments, The decrease i n oxygen content may r e s u l t i n an oxygen d e f i c i t , and i n the decay of a e r o b i c organisms. The thermal s t r a t i f i c a t i o n influences a l l t h e

323

* INPUT General controls, System geometry, co e f f i c ient s WEATHER INFLOWS,

QUALITY

I

I

DEPOSITION OF INFLOWS CALCULATE VERTICAL ADVECTON

TEMPERATURE

Matrix

PROF I L E

Operation Module

L

CONS E RVAT I V E SUBSTANCES

I.

T D S , ALKALINITY

Form matrix coefficients

NO CONS ERVAT I V E SUBSTANCES

2 . S o l v e for *d/t t 3. Solve

c /t

+At/ for t a t /

4 . R e t u r n with new concent r a t ions NUTRIENTS P , N /NH3 NOZ,

,

NO/,

C

RES U LT S

Fig. 4.20. Flowchart diagram ( t h e lake ecological model) f o r determining the changes i n water q u a l i t y and the biomass production according t o Chen and Orlob (1973).

324 chemical and b i o l o g i c a l p r o c e s s e s , determining the w a t e r q u a l i t y and t h e r a t e of b i o l o g i c a l production (Fig. 4 . 2 0 ) . Human a c t i v i t i e s a l s o c o n t r i b u t e t o the occurrence of zones with an oxygen d e f i c i t , e s p e c i a l l y e f f l u e n t s , p i t s and dikes a t the bottom of the r e s e r v o i r , impeding the water c i r c u l a t i o n . S i m i l a r e f f e c t has the inexpediency of t h e res e r v o i r o p e r a t i o n , e . g . i t s emptying by upper o l i t l e t s and s p i l l w a y s , which i s required n o t only during floods but a l s o t o i n c r e a s e the water temperature i n

s m e r f o r b a t h i n g downs treams . The thermal s t r a t i f i c a t i o n is less s i p n i f i c a n t , o r does n o t occur a t a l l , i n

shallow r e s e r v o i r s (see Eq. 4.31). The c o o l e r water is g e n e r a l l y a t the end of the backwater. The temperature i n c r e a s e s i n t h e d i r e c t i o n of therrain flow, i . e . to the d a m , s p i l l w e i r o r o u t l e t . The h e a t i n e r t i a of shallow r e s e r v o i r s is low. The decrease i n temperature a t n i g h t may r e s u l t i n the f o r n i t i o n of homother-

m i c i t v , enabling i n t e n s i v e water c i r c u l a t i o n . The h i g h e r day temperatures r e s u l t i n the formation of an inexpressive metalimnion. A s i t grows i n s i z e , t h e m e t a l i m i o n reaches the bottom, and e r a d u a l l y disappears. The r e s i i l t i n p homothermicity permits freqiient c i r c u l a t i o n , thereby i n c r e a s i n g t h e b i o l o g i c a l production of shallow r e s e r v o i r s . An improvement i n water q u a l i t y i n r e s e r v o i r s can be achieved by mechanical d e s t r a t i f i c a t i o n , by t h e use of a i r and mechanical piimps o r by treatment with I

copper s u l p h a t e CriSO with o r without c i t r i c a c i d , lime and aliim. The c o n t r o l of 4 a l g a e g r m t h can a l s o be achieved by l i r n i t i n p t h e nutri-ent i n p u t i n t h e major t r i b u t a r i e s , e s p e c i a l l y by 1imit.ing t h e i n p u t of phosphonis.

4.6.4 I n f l u e n c e of Plan-made L.akes on t h e Riasphere and S o c i e t y ' h e development of aqiiatic l i f e i n a new r e s e r v o i r i s g r e a t l y influenced, and the water q u a l i t y i s determined, by t h e followinp f a c t o r s : - topographical, geological and s o i l c o n d i t i o n s of t h e l o c a l i t y and its vegeta t i v e canopy - c l i m a t o l o g i c a l conditions of t h e s i t e , e s p e c i a l l y t h e d u r a t i o n of sunshine - water q u a l i t y of i t s t r i b u t a r i e s and t h e r e s u l t i n g water temperature - the o r i g i n a l ecosystems i n t h e r i v e r and on t h e s h o r e

-

c l e a r i n g , removinp of stamps, l i t t e r , humus, c l e a n i n g and o t h e r measures

undertaken by man t o decrease s a n i t a r y hazards - measures taken by man t o a c c e l e r a t e t h e development of d e s i r a b l e s p e c i e s i n the ecosystem o f t h e new r e s e r v o i r

-

o p e r a t i o n ol t h e r e s e r v o i r , o f t e n causinp a p e r i o d i c d a i l y , weekly and sea-

sonal d r a w - d m and rise of t h e water t a b l e - a p p r o p r i a t e h u m n a c t i v i t i e s d u r i n g t h e r e s e r v o i r ' s o p e r a t i o n , namely those r e s u l t i n g i n water p o l l u t i o n . (Tab. 4.19).

325 TABLE 4.19 ~~

Category

Factor

Category

Factor

;{qua t i 2 :

Terres t r i a ! : P-pula t i o n

Crops 1Va::ml v e g e t a t i o n Herbivorous mammals Carnivorous mamals 1Jpland game b i r d s Predatory b i r d s

Habitat/land use

Bottmland f o r e s t ( a ) Ilpland f o r e s t 6) Dnen !non-forest)lands(c) Drawdown zonc TAnd u s e

Land qiiality! S o i l e r o s i o n s o i l e r o s i o n S o i l chemistry Mineral e x t r a c t i o n Species d i v e r s i t v C r it ica 1 ccmmuni ty r e l a t i o n sh i p s Air: hiality

Carbon monoxide Hydrocarbons Oxides of n i t r o g e n P a r t ici I 1a tes

Climatology

Diffusion f a c t o r

Hiunan Interface.

No;i e

Noise

Aesthetics

IhJidth and alignnimt Variety w i t h i n vegetation tyne Animals-domestic M a tive Fauna Appearance of water Odor and f l o a t i n g mterials Odor and v i s u a l q u a l i t y Sound

Historical

Internal & external s i t e s

P o p l a t ions

k t u r a l vegethtion Wet land Lrege t a t ion Zoopi an’:to? Phy torrla-+ton Sport f i s h Comercia 1 f i s h e r i e s I n t e r t i d a 1 rrgmisms SenthosjE-i br,n tlios Wat p r f ow 1

Flab i t a t s

Stream ( ~ 1 ) Freshiwter lsite ’e) ‘River Swamp ‘f) Non-river Swamp ‘P)

Water q u a l i t y PI! ievel. Tiirbiaity Silspended solids Water temperature Dissolved oxygen Biochemical oxygen demand Dissolved s o l i d s Inorganic n i t r o g e n Inorganic phosphate Salinity I r o n and mnganese Toxic substances Pesticides Faecal coliforms Stream a s s i m i l a t i v e ca pa c 1t y Water quantity

Stream flaw v a r i a t i o n Rasin hydrologic loss

Critical Species d i v e r s i t y community relationships

Archaeolopkal I n t e r n a l & e x t e r n a l s i t e s C h e c k l i s t of bio-physical and c u l t u r a l environment f a c t o r s f o r impoundment proj e c t s accordinp t o Canter (1983). E x p l i c a t i o n s f o l l m .

32 6 (a)

A composite of the species a s s o c i a t i o n s : percentage mast-bearinr

trees;

percentage cowred by imderstory; d i v e r s i t y of understory; percentage covered by groundcover: d i v e r s i t y of groiindcover : number of trees 2 0 . 5 m diameter per ha ; percentage of t r e e s 2 0.5 m diameter; frequency of inundation: edge (qriantity) and edge f q r i a l i t y ) . ( b ) A composite of t h e following: species a s s o c i a t i o n s ; percentage mstbearing t r e e s ; percentage coverage of understory; d i v e r s i t y of understory; per-

centage coverage of groundcover : d i v e r s i t y of groundcover; ntniber of t r e e s 0 . 5 m diameter/ha; percentage of trees 2 0 . 5 m diameter; q u a n t i t y of edqe; and, mean d i s t a n c e t o edge. ( c ) A composite of the following: land use: d i v e r s i t y of land use; quantity of edge; and, mean d i s t a n c e t o edge. (d) A composite of the followin?: s i n u o s i t y ; dominant centarchids; mean low water width; t u r b i d i t y ; t o t a l dissolved s o l i d s ; chemical type; d i v e r s i t y of f i s h e s ; and d i v e r s i t y of benthos. ( e ) A composite of the following mean depth: t u r b i d i t y ; t o t a l dissolved s o l i d s ; chemical type; shore development; spring flooding above veget.ation l i n e ; s t a n d i n e crop of f i s h ; standing crop of s p o r t f i s h ; d i v e r s i t y of f i s h ; , and, d i v e r s i t y of benthos. (f)

A composite of the followinR: species a s s o c i a t i o n s ; percentage f o r e s t

cover; percentage flooded annually; groundcover d i v e r s i t y ; percentage of groundcover; and, days s u b j e c t t o r i v e r overflow. (g)

A composite of t h e f o l l m i n g ; species a s s o c i a t i o n s ; percentage f o r e s t

cover; percentage flooded annually ; groiindcover d i v e r s i t y and percen tape o€ groundcover. Non-influenced ecosystems i n the man-made r e s e r v o i r tend i n the long term to achieve b i o l o g i c a l eqtJilibrillm, corresponding t o a n a t u r a l lake under s i m i l a r conditions. Man-made r e s e r v o i r s can t h e r e f o r e be cate,gurized i n t h e same way a s natural lakes (Tab. 1.31). As soon a s t h e f i l l i n g up of a r e s e r v o i r begins, the o r i g i n a l ecos!;stem

of

flowing r i v e r water changes, gradually being replaced by a new ecosystem of stagnant water. Within a period of several weeks, an overdevelopment of some plankton species usually oc.curs. This hoom a f f e c t s the s p e c i e s , h i c k do not encounter impol-tznt l i f e concurrence and f i r s t find t h e r i c h stock of nutriments i n t h e newly

flooded s o i l l a y e r s and t h e i r p a r t l y ranoved vegetation canopy.

The development boom of t h i s species is i n t e r r u p t e d i n t h e n e x t s t a g e by an overdraw of the o r i g i n a l nutriments, leading t o t h e development of o t h e r species. This s i t u a t i o n gradually tends towards a b i o l o g i c a l equilibrium, with a more r i c h a q u a t i c l i f e i n the area of the e s t u a r i a e s of the r e s e r v o i r t r i b u t a r i e s , where the nutriment i n p u t is more i n t e n s i v e .

327 The a q u a t i c l i f e of man-made lakes i s g r e a t l y influenced by a frequent d r a w darn and rise of the water l e v e l . This r e s u l t s i n the poorer heterogeneity of ecosytems i n the upper l i t t o r a l zones of man-made r e s e r v o i r s i n comparison with n a t u r a l ones: these ecosystems do n o t include species which a r e not r e s i s t a n t t o the

f l u c t u a t i o n of the water l e v e l and which c a m n t follow the water l e v e l

o r f i n d a temporary s h e l t e r i n the denuded s u r f a c e cover. This is the reason why a niunber of c u r r e n t species a r e disappearing a s a res u l t of the a c t i o n of the f l u c t u a t i n g water l e v e l , including weed, rush e t c . ,

and t h e r e only remain some unwanted species of i n s e c t s (some midges and m a t s ) and worms ( e . g . l e e c h e s ) . The occiirrence of m s q u i t o s can be s i g n i f i c a n t l y reduced by a managed draw-down and r i s i n g up of the water level.. The occurrence of aqiiatic species depends mainly on (a)

c r i t i c a l physical and chemical f a c t o r s , i . e . on the occurrence of n u t r i -

ments which are indispensable f o r t h e r e l e v a n t species i n q u a n t i t i e s exceeding the necessary minimum, (b)

the ecological valency, i . e . on the e x t e n t of the tolerance of the re-

l e v a n t organisms t o these f a c t o r s and t o t h e occurrence of o t h e r unwanted corn ponents of t h e i r l i v i n g environment. C r i t i c a l limits and optimum conditions a r e s p e c i f i c f o r the species i n qiiestion. Approaching these l i m i t s , l i v i n g phenomena become more demanding, e s p e c i a l l y e n e r g e t i c a l l y . I h d e r favourable conditions,

less energy i s required, leaving a q u a t i c aninals t h e necessary reserve f o r findi n g and consuming food. A s u f f i c i e n c y of food and energy supply and an appropriate environment form t h e optimum l i v i n g conditions f o r t h e species i n questivn.

lhe existence of r e l e v a n t f i s h species depends on the water q u a l i t y , - mainly ,on i t s temperatune and oxygen content, on t h e water depth, r a t e of flow, morphology and macerial of t h e bottom and the banks, and on t h e occurrence of

aquatic

f l o r a . The construction and operation of a r e s e r v o i r changes a l l these conditions.

A dam o r a weir fonns an i n v i n c i b l e o b s t a c l e f o r the draw of migratory f i s h e s , e . g . e e l s , salmon. Fish t r a p s , e l e v a t o r s and o t h e r equipment constructed t o enable the migration of f i s h e s do n o t form an adequate s u b s t i t u t e f o r such a purpose. There a r e a l s o problems with t h e optimum location of such equipment and t h e i r capacity, espec i a l l y i n t h e period of the draw, i s o f t e n n o t s u f f i c i e n t . The migration of f i s h e s is already r e s t r i c t e d during t h e construction period. The development of some f i s h species i s even c u r t a i l e d . Fish species t h a t a r e not ?ble t o accept the changed conditions d i e o u t , changing i n t h i s way the s t n i c t u r e of the ecosystem and conditions f o r the developmnt of o t h e r h e r b i w r e s , carnivores and d e t r i v o r e s . The conditions f o r f i s h occurrence i n fish-ponds d i f f e r completely from those

in r e s e r v o i r s used f o r water supply and flow c o n t r o l . High inflow and

outflow r e s u l t i n a high r a t e of water exchange and i n water q u a l i t y which i s characterized by a lack of nutriment content. Fresh water f i s h e s usually l i v e

328 n e a r s h o r e s , and n o t i n t h e f r e e space, where a l a c k o f n u t r i t i o n occurs. Tnls r e s u l t s , togei-her with the lack o f s o l a r r a d i a t i o n , low temperature and lack of oxygen, i n a s u b s t a n t i a l drop i n p r o d u c t i v i t y i n r e s e r v o i r s deeper than f i f t e e n meters. The water l e v e l f l u c t u a t i o n reduces t h e production s u r f a c e and destroys zooplankton, t h e b a s i c component of t h e f i s h e s ' food. Tne p r o d u c t i v i t y of a reserv o i r does n o t depend on t h e extend and frequency of t h e water l e v e l f l ~ i c t u a t i o n o n l y , b u t also on t h e p e r i o d of i t s occurrence. Shores covered by a dense veget a t i v p canopy form favourable conditions f o r f i s h s h e l t e r s , spawn deposition and f o e t u s development. The decrease i n t h e water l e v e l iisually d e s t r o y s spawn and foetiis, e s p e c i a l l y i n i t s e a r l y s t a g e of development. The drop i n t h e water t a b l e a l s o has c e r t a i n p o s i t i v e e f f e c t s on f i s h production, fomiinp s u i t a b l e conditions f o r fauna development i n t h e uncovered s u r f a c e . The inundated g r a s s e s c r e a t e a favourable environment f o r t h e development o f some f i s h s p e c i e s , a s w e l l a s o f f e r i n g them food. The population boom of some f i s h s p e c i e s , e . g . of p i k e , a f t e r the f i r s t f i l l ing of t h e r e s e r v o i r i s also caused by t h e abundance of nutriments i n the newly inundated s o i l s u r f a c e and by t h e number of s h e l t e r s . This population boom l a s t s s e v e r a l y e a r s , then g r a d u a l l y

diminishes.

Ichthyofauna o f man-made lakes can be categorized a s follows: ( a ) f i s h e s which occur i n t h e r e s e r v o i r from t h e o r i g i n a l ecosystem of t h e stream and which a r e a b l e t o adapt t o t h e changed environment and breed n a t u r a l l y , h ) fishes

which have extremely favoiirable conditions f o r t h e i r natiiral

breeding and development and a r e a b l e t o exterminate o t h e r f i s h s p e c i e s ,

(c\

f i s h e s of t h e o r i g i n a l ecosystem which a r e a b l e t o adapt to t h e changed

conditions only i n r e s t r i c t e d a r e a s of stream e s t u a r i e s , where conditions have not been changed d r a s t i c a 1l y , ( d ) f i s h e s which a r e a b l e t o l i v e i n the reservoir, b u t do r:ot have the abil i t y t o breed n a t u r a l l y , thiis r e q u i r i n g a r t i f i c i a l breeding f o r replenishment of t h e i r occurrence, ( e ) f i s h e s which a r e imported a r t i f i c i a l l y from o t h e r ecosystems and, being adaptable t o t h e r e s e r v o i r c o n d i t i o n s , a r e a b l e t o f u l f i l l t h e required function i n t h e r e s e r v o i r ecosys t e m : weed r e d u c t i o n , maintenance of ecosystem equilibrium,

meat production e t c . The ecosystem of a r e s e r v o i r includes (a)

f i s h e s intended f o r breeding,

'b) supplementary f i s h e s , u s i n g food which i s n o t u t i l i z e d by t h e r a i s e d fishps. The e x t e n t and i n t e n s i t y of changes i n t h e landscape caused by t h e r e s e r v o i r depend n o t only on t h e topography, c h a r a c t e r and a c c e s s i b i l i t y o f t h e a r e a and

on t h e d e n s i t y of popillation and communication l i n e s , b u t a l s o

OR

t h e s i z e of the

329 r e s e r v o i r , e s p e c i a l l y on i t s s u r f a c e a r e a . The following occurs a f t e r the const r u c t i o n and o p e r a t i o n of a r e s e r v o i r : (a\

-

changes i n t h e inundated a r e a :

flooding o f f o r e s t s , c r i l t i v a t e d and urbanized l a n d , comnunications, b u i l d i n g s

and o t h e r engineerinE works, landmarks and h i s t o r i c p l a c e s , - flooding of mines and mineral d e p o s i t s e t c . ,

-

t h e e x t i n c t i o n of t h e o r i g i n a l ecosystems, t h e d e s t r u c t i o n of dry land species

of f l o r a and fauna, i n c l u d i n g t h e r a r e ones, -

t h e i n c e p t i o n of a q u a t i c

f l o r a and fauna, a s w e l l as t h e extension and chanEe

of i t s environment, i n c l u d i n g t h a t f o r fowl and i n s e c t s .

-

Ib) changes i n t h e r e s e r v o i r environment c r e a t i o n of new scenery, influenced by the water l e v e l f l u c t u a t i o n ,

- changes i n t h e hydrogeological and hydropedological c o n d i t i o n s , new b a l l a s t of t h e E a r t h ' s c r i i s t ,

-

changes i n t h e groundwater l e v e l , s o i l misture and a i r hiunidity, changes i n

tempera tiire, r e s u l t i n g i n a change of ecosys tems ,

-

chanzes i n the l i v i n g environment o f man: change i n dwelling environment, i n

h e a l t h and r e c r e a t i o n a l c o n d i t i o n s , and a s e v e r i n g of comnunication l i n e s , - change i n t h e conditions f o r economic development: t h e economic impact of the dam c o n s t r u c t i o n and r e s e r v o i r o p e r a t i o n causes a c o n s t r u c t i o n boom, a s t h e equipment used on t h e b u i l d i n g s i t e o f f e r s p o s s i b i l i t i e s f o r f u r t h e r u t i l i z a t i o n , and t h e c o n s t r u c t i o n of new comnunications i n c r e a s e s t h e a c c e s s i b i l i t y of t h e a r e a and i t s consequent u t i l i z a t i o n f o r r e c r e a t i o n purposes, which leads t o a modernization of t h e l i f e s t y l e of t h e population. The r e s e r v o i r ' s environment i s n e g a t i v e l y a f f e c t e d by t h e water l e v e l fluct u a t i o n , e s p e c i a l l y a t t h e end of backwater and i n f l a t a r e a s . When t h e banks a r e s t e e p , l a n d s l i d i n g may occur. The n e g a t i v e consequences o f t h e w a t e r l e v e l f l i i c t u a t i o n should be r e s t r i c t e d by overflow dams, d i k e s , banks, ramparts, and by excavation i n shallow flooded a r e a s e t c .

D r y land ecosystans a r e a f f e c t e d n o t only by t h e r i s e i n t h e groundwater l e v e l and by an i n c r e a s e i n s o i l moisture 2nd a i r humidity, but a l s o by t h e flooding of p a s t u r e s and dens, by complications a s s o c i a t e d with t h e access of shy animals t o water, by t h e worsening i n t h e l i v i n g c o n d i t i o n s , e s p e c i a l l y of r a r e spec i e s , through t h e i n c r e a s e i n population d e n s i t y and economic a c t i d t i e s . Ln s p a r s e l y populated a r e a s r e s e r v o i r shores form favourable conditions f o r n e s t i n g and r e s t i n g p l a c e s f o r migratory b i r d s . The s o c i a l , group and personal i n t e r e s t s of t h e population a r e a f f e c t e d by the c r e a t i o n o f new s h o r e s , by t h e i n c r e a s e i n s o i l m i s t u r e , by changes i n the microclimate e t c . The i n c r e a s e i n dwelling value of a r e a s n o t adversely a f f e c t e d by water l e v e l f l u c t u a t i o n waterlogging o r o t h e r n e g a t i v e e f f e c t s r e s u l t s i n an i n c r e a s e d d e n s i t y of h a b i t a t i o n . The change i n the dwelling value has an i m p o r

330 t a n t impact on the l i f e s t y l e , supporting i t s r e c r e a t i o n a l a s p e c t s . The reserv o i r c r e a t e s o r supports favourable conditions f o r f i s h i n g , camping, hunting, and o t h e r types of

veelrend and vacational r e c r e a t i o n . The space f o r water t o u r

i n c r e a s e s , but the r e c r e a t i o n a l value is sometimes prejudiced by the change

ism

of the flowing water i n t o s t a g n a n t water. The increased d e n s i t y of h a b i t a t i o n has a s a secondary e f f e c t a breaking down of t h e n a t u r a l v e g e t a t i v e canopy, an i n c r e a s e i n the erosion r a t e . a rise i n the t r a n s p o r t d c n s i t y , an increase i n n o i s e d e n s i t y , a gradual p o l l u t i o n of the environment, with t h e

concomitant need f o r a mass water supply, orEanized waste

and waste water removal. Depending on t h e water q u a l i t y and p r e v a i l i n g s a n i t a r y conditions, the reserv o i r operation can c r e a t e o r strengthen the conditions f o r t h e dissemination of germs o r th&

b e a r e r s , e s e p c i a l l y i n t r o p i c a l and s u b t r o p i c a l a r e a s . Negative

circiimstances may resiil t i n economic, cul tiiral and s o c i a l l o s s e s , e i t h e r permanent o r temporary, e s p e c i a l l y i n the period during and s h o r t l y a f t e r the cons-

true t i o n . Some of t h e expected economic e f f e c t s nay be not achieved due t o v a r i o i s planning, f i n a n c i a l and organizational obstacles o r due t o t h e unexpected react i o n of the population. This ,nainly concerns the immediate surroundings of the r e s e r v o i r , which sometimes f a i l t o a t t r a c t s u f f i c i e n t i n t e r e s t among p o t e n t i a l investors. [Jncoordinated planning and lack of investment i n f u r t h e r Construction acciviw o r i n s t i t u t i o n a l gaps may cause discrepencies i n t h e area i n question, r e s t r i c t i r l g o r even c a n c e l l i n g t h e p o s i t i v e impact of t h e r e s e r v o i r i n t h e border a r e a s , o r even a l t o g e t h e r .

4.6.5

E f f e c t of Flow Control and Water Withdrawals

Downstream of t h e dam p r o f i l e the r e s e r v o i r operation and water withdrawals affect, especially, - the water and i c e regime, the t r a n s p o r t of sediments, and t h e water q u a l i t y , - the a q u a t i c f l o r a and t h e r i v e r s i d e canopy, - t h e a q u a t i c fauna including f i s h e s ,

-

the dwelling value of t h e relevant a r e a (Tab. 4.20). Changes i n the water regime a r e m n i f e s t a t e d mainly by changes i n discharges,

dependent on t h e r e s e r v o i r operation, and on the t i m e d i s t r i b u t i o n of water withdrawals and e f f l u e n t s . These changes r e s u l t e s p e c i a l l y i n ( a ) a d e c l i n e i n peak discharges and r e l e v a n t water l e v e l s downstream, usually with t h e exception of superfloods and floods of long d u r a t i o n , because these o f t e n exceed t h e capacity of t h e r e s e r v o i r , (b)

an increase i n low discharges,

(c)

a water deficiency i n the case of excessive water withdrawls.

33 I TABLE 4.20

Impact o f r e s e r v o i r o p e r a t i o n and water withdrawl on downstream water course \dater q u a n t i t y

[dater q u a l i t y

Flora/Fishes Change i n water t a b l e and groundwater t a b l e

h e 1l i n g

Decrease i n hi&er discharges

Increase i n low discharges

Ilecrease i n Decreased sediment salinity transport of low discharges

Restricted floodinp

Improved water supply

Oecrease water t a b l e o f floods

I n c r e a s e i n Chanze i n salinity.by aquatic evaporation f l o r a

Improved flood control

Restricted natural fertilization

Improved navigation and power generation

Decrease i n sedimentat i o n flooded land

Increase i n nitrogen, i r o n and mangan content

Restricted s o i l regenera t i o n

Restricted erosion

Decrease i n sedimentation Decrease i n oxygen content

Increase i n yield

Changes i n p a t t e r n of wa tertourism

Restricted groundwater recharge

I n c r e a s e i n Decrease i n Decrease i n water tani n f i l t r a t i o n clogging perature i n summer

Interrupted draw o f , fishes

Restricted sumner recreation

Restricted waste disposal

Improved sanitary conditions

Increase i n Water tanperature i n winter

Restricted migration O f fishes

Restricted skating i n winter

Decrease.in evaporation

Slight increase i n evaporation

Change i n i n c e format i o n and

Change i n zones of fish occurrence

Extended period o f high turbidity

flow

Change i n coastal

flora

Decrease i n water t a b l e and d i s c h a r g e f l u c t u a t i o n P e r i o d i c f l u c t u a t i o n of water t a b l e and discharges i n c a s e of hydropower genera t i o n C h e c k l i s t o f t h e probable impact o f reservoir o p e r a t i o n and water withdrawal on downs tream water course.

332 Water withdrawals do n o t g e n e r a l l y r e s u l t i n a s i i b s t a n t i a l d e c r e a s e i n flood

d i s c h a r g e s , a s they a r e u s u a l l y comparatively s m a l l . Big withdrawals, such a s those used f o r i r r i g a t i o n purposes, reduce t h e value o f low discharges i n t h e siimer season, thus causing a n i n c r e a s e i n t h e s e discharges i n t h e w i n t e r season

on account o f t h e g r e a t e r groundwater oiitflow from i r r i m t e d land a t t h a t t i m e . I r r i g a t i o n may a l s o i n c r e a s e flood d i s c h a r g e s , because watered land has a l i m i ted i n f i l t r a t i o n c a p a c i t y , thus causinq a n i n t e n s i v e outflow of t h e rainwater. The flood c o n t r o l e f f e c t of the r e s e r v o i r r e s u l t s i n fa, (b,

a d e c l i n e i n t h e flooded a r e a , a d e c l i n e i n t h e e x t e n t and frequency of i r r i g a t i o n by flood water sprea-

d i n g and s o i l regeneration by s i l t sediments, (c)

a d e c l i n e i n t h e r a t e of n a t u r a l r i v e r s i d e i n f i l t r a t i o n ,

( d ) a d e c l i n e i n t h e e r o s i o n r a t e , and a n i n c r e a s e i n t n e sedimentation r a t e . The d e c l i n e i n t h e flooded a r e a r e s u l t s i n a reduction i n flood l o s s e s . N e v e r t h e l e s s , i r r i g a t i o n by flood water spreading i s r e s t r i c t e d , thus reducing t h e r e g e n e r a t i o n r a t e of t h e s o i l p r o f i l e . I n t h i s c a s e , t h e n a t u r a l watering and s o i l r e g e n e r a t i o n process has t o be replaced by a r t i f i c i a l i r r i g a t i o n and f e r tilizing,

which r e s u l t s i n high

o p e r a t i o n c o s t s and a l s o r e q u i r e s a p p r o p r i a t e

o p e r a t i o n s k i l l , a s w e l l as being connected with a change i n i r r i p a t i o n methods and i n t h e cropping p a t t e r n . The necessary measiires f o r t h i s purpose require the supply o f a r t i f i c i a l f e r t i l i z e r s , energy f o r t h e i r production, manpower and s k i l l and may appear t o be o p e r a t i o n a l l y , f i n a n c i a l l y o r o r g a n i z a t i o n a l l y rinsiritable, e s p e c i a l l y i n develop i n g c o u n t i r e s . They are f e a s i b l e f.sr i n t e n s i v e production, but a r e n o t satisf a c t o r y from t h e environmental p o i n t of view, a s they m y supply t h e requested q u a n t i t y o f anorganic n u t r i m e n t s , b u t n o t t h e necessary volume of organic m t t e r . Flood c o n t r o l r e s u l t s i n t h e d e c l i n e i n t h e n s t u r a l r i v e r s i d e i n f i l t r a t i o n , r.ediiction i n t h e groundwater recharge and subsequent n e g a t i v e influerice on a g r i c u l t u r a l production, e s p e c i a l l y i n f l a t r i v e r v a l l e y s . I n the case of the low q u a l i t y of r i v e r w a t e r , t h e drop i n t h e i n f i l t r a t i o n r a t e r e s u l t s i n an improvement of t h e groundwater q u a l i t y . The d e c l i n e i n t h e e r o s i o n r a t e and i n t e r r u p t i n g of t h e sediment t r a n s p o r t which r e s u l t from t h e flood c o n t r o l functions

of t h e reservoir serve the m i n -

tenance of r i v e r b e d s . As a consequence o f the r e d u c t i o n i n high d i s c h a r g e s , a n i n c r e a s e i n t h e sedimentation r a t e may occur r e s u l t i n g i n a decrease i n t h e channel c a p a c i t y downstream of t h e dam p r o f i l e and thus i n f l u e n c i n g water l e v e l hydrographs, n a v i g a t i o n conditions e t c . As a r e s u l t of the decreased discharges and a t t e n d a n t h i g h e r sedimentation, the rate of t h e s e l f - p u r i f i c a t i o n processes f a l l s , thus causing a d e t e r i o r a t i o n i n t h e water q u s l i t y . The decrease i n the e r o s i o n , and i n c r e a s e i n t h e sedimentation r a t e n e g a t i v e l y i n f l u e n c e t h e r r e n c e of f i s h s h e l t e r s , thus l i m i t i n g t h e f i s h population.

OCCII-

333 Depending on the given c o n d i t i o n s , the r e s e r v o i r with a low impact on flood discharges m y on the c o n t r a r y , owing t o i t s t r a p e f f i c i e n c y d e p r i v i n e the downstream flow of i t s sediment content, increase t h e erosion r a t e downstream. The increase i n low discharges i s caused not only by the r e s e r v o i r operation, but a l s o by the influence of water u t i l i z a t i o n processes between the water withdrawal and e f f l u e n t , the second process having a negative e f f e c t on the water qua 1i ty . The i n c r e a s e i n low discharges, being accompanied by a r a i s i n g of minimum

water l e v e l s , c r e a t e s more favourable conditions f o r water withdrawals, navigat i o n and water power generation, a s w e l l a s having a favourable impact on the groundwater regime, and therefore a l s o on a g r i c u ~ t u r eand f o r e s t r y . such a r a i s ing of the water t a b l e m y sometimes r e s u l t i n advancing p e r c o l a t i o n and evapor a t i o n , i . e . i n growing water l o s s e s . The flow r a t e i n c r e a s e s , a u p e n t i n g sediment

t r a n s p o r t and t h e r a t e of s e l f - p u r i f i c a t i o n processes, and thereby improv-

i n g the s a n i t a r y conditions and the a e s t h e t i c value. TJnder c e r t a i n circumstances the flow r a t e may exceed the relevant l i m i t i n g values of the r i v e r bottom stab i l i t y , thus causinz erosion. \dater w i thdr;wals t r a t i o n of

and subseqijent u t i l i z a t i o n frequently increase the concen-

dissolved o r susperided w t t e r i n t h e remaining discnarges. Water

u t i l i z a t i o n decreases the oxygen content e s p e c i a l l y and increases the nitrogen content. The r e g u l a t i n g e f f e c t of t h e r e s e r v o i r with a longer : r a t e of water exchange mostly reduces the l e v e l of water p o l l u t i o n . The a u p e n t a t i o n of low discharges a l s o d i l u t e s the p o l l u t i o n i n water from t r i b u t a r i e s and e f f l u e n t s . The sedimentation and s e l f - p u r i f i c a t i o n processes i n the r e s e r v o i r generally have a favourable e f f e c t on t h e q u a l i t y of t h e water outflow, even i n the case of a low q u a l i t y

inflow. I n semi-arid and a r i d a r e a s t h e concentration of

dissolved and suspended matter can nevertheless be increased by passing through the r e s e r v o i r with a high evaporation r a t e . The value of t h e water p o l l u t i o n downstream of the r e s e r v o i r , a t the conf1.uence o r a t t h e e s t u a r y of e f f l u e n t s , can be determined o r its course m d e l l e d on the b a s i s of the mixing formula

i

q l ' ici

iq i

3

-

',-

the concentration of r e l e v a n t i n d i c a t o r s before the confluence o r before the estuary of e f f l u e n t r e s u l t i n g concentration downstream

r e s u l t i n g concentration downstream

- l , 2 , 3

Q1 - Q,

.....,n

order of water q u a l i t y i n d i c a t o r s

- discharges upstream of t h e confluence.

The r e a l course of t h e water p o l l u t i o n i n t h e longitudina1 p r o f i l e of t h e

water course d i f f e r s from t h e computed on account of t h e s e l f - p u r i f i c a t i o n '

process incluclim sedimentation. The r e l e v a n t computed values should, t h e r e f o r e , be checked and c o r r e c t e d i n t h e seqiience from t h e upper p r o f i l e t o t h e e s t u a r y . On t h i s b a s i s , t h e course of t h e water q u a l i t y can a l s o be c o n t r o l l e d and i t s

improvement during c r i t i c a l p e r i o d s achieved by r e s e r v o i r o p e r a t i o n . Such an emptying o f t h e s t o r a g e is t o t h e detriment of t h e water supply. The f e a s i b i l i t y o f such o p e r a t i o n depends on t h e course of t h e decomposition processes and on the evaporation r a t e i n t h e r e s e r v o i r , and r e s u l t i n g w a t e r q u a l i t y . The changes i n water temperature dowristream o f t h e dam s i t e a r i s e froin t h e r e s e r v o i r o p e r a t i o n . With t h e power g e n e r a t i o n o r w i t h t h e bottom o u t l e t open, t h e deep water l a y e r s , i . e . t h e hypolimnion, a r e emptied, which r e s u l t s i n a cooling of the r i v e r water i n t h e summer season and i t s warming durinp w i n t e r , i n comparison with t h e o r i g i n z l s t a t e bpfore t h e r e s e r v o i r o p e r a t i o n . This water a l s o contains more n i t r o g e n and i r o n and less oxypen. The d i f f e r e n c e i n water q u a l i t y , i n c l u d i n g temperature, i s s u b s t a n i o n a l , e s p e c i a l l y i n t h e case of a cascade of r e s e r v o i r s . The water of the epilimnion, whose temperature does not d i f f e r as much from t h e o r i g i n a l one, e n t e r s t h e r i v e r channel downstream of the r e s e r v o i r by means of s p i l l w a y s ,

mainly during f l o o d s , i . e . not so f r e q u e n t l y .

Temperature changes have a n i n f l u e n c e on, e s p e c i a l l y , la)

water i i t i l i z a t i o n a f t e r its withdrawal

(b)

f i s h occiirrence and f i s h breedinp

Cc) o t h e r in-stream water u s e s , e s p e c i a l l y water s p o r t s , r e c r e a t i o n , navig a t i o n , and a l s o waste d i s p o s a l . The decrease i n water temperature i s f a w u r a b l e f o r both municipal and indust r i a l w a t e r siipply, namely f o r cooling purposes. For i r r i g a t i o n purposes, warmer water i s more convenient. Changes i n water temperature and water q i i a l i t y a l s o i n f l u e n c e t h e ichthyofauna. They may cause a change i n the zones of f i s h occurrence. The changes i n w a t e r temperature mostlv have a n e g a t i v e e f f e c t on rec r e a t i o n and water s p o r t s ; the cool water i n simmer s p o i l s the conditions f o r b a t h i n g and o t h e r water s p o r t s ; w h i l e t h e i n c r e a s e i n w i n t e r temperature rest r i c t s t h e f r e e z i n g o f t h e water pool and s k a t i n g i n w i n t e r , b u t tempers t h e i c e bound regime, thus c r e a t i n g more favourable conditions f o r water t r a n s p o r t . Water temperatures are a l s o a f f e c t e d d i r e c t l y by water withdrawals, decreasing w a t e r d i s c h a r g e s , w a t e r depth and flaw r a t e s with consequent temperature i n c r e a s e , a l s o caused by t h e high temperature of e f f l u e n t s from cooling systems. These temperature changes depend t o a g r e a t e x t e n t on t h e r a t i o of discharges and withd r a w a l s a n d o n t h e q u a n t i t y and temperature of e f f l u e n t s . Water withdrawals a l s o i n c r e a s e t h e c o n c e n t r a t i o n of sediments i n t h e remaining discharge, aggravated by material i n p u t from e f f l u e n t s , i n c r e a s i n g t h e sedimentation r a t e and causing the f i l l i n g o f r i v e r b e d s .

335 The drop i n t h e sediment content i n discharges caiised by the sedimentation i n the r e s e r v o i r reduces the course of water l e v e l s i n comparison with t h e s t a t e prior

LO

the r e s e r v o i r o p e r a t i o n . The f a l l i n t h e water t a b l e reduces t h e poten-

t i a l energy, and augments the k i n e t i c energy of water. This i n t e n s i f i e s t h e eros i o n p r o c e s s , e n t a i l i n g a g r a d m l i n c r e a s e i n sediment and bed-load t r a n s p o r t downstream, where, depending on t h e c o n d i t i o n s , t h e water l e v e l may gradually approach t h e o r i g i n a l one of the same discharge. Downstream of t h e r e s e r v o i r , the p e r i o d of t u r b i d water discharges i s u s u a l l y longer because of t h e g e n t l e sedimentation of f i n e p a r t i c l e s i n t h e r e s e r v o i r . The n a t u r a l r i v e r channel downstream of t h e r e s e r v o i r i s a l s o a f f e c t e d by the c o n s t r u c t i o n o f many o f f t a k e and o u t l e t s t r u c t u r e s , sane s t r e t c h e s being regulated o r paved i n t h i s connection. The n a t u r a l r i v e r s i d e canopy, whose development and s t a t e depends on c l i m a t o l o g i c a l conditions , a l t i t u d e , s o i l and geomorphologic a l c o n d i t i o n s , bank s l o p e s ,

e x p o s i t i o n o f t h e l o c a t i o n and the water regime

changes under t h e long-term i n f l u e n c e of t h e w a t e r l e v e l a l t e r a t i o n s and conseqiient changes i n groundwater t a b l e . Vegetation s p e c i e s which a r e n o t adaptable

t o t h e new c o n d i t i o n s gradually e x p i r e , a f f e c t i n g t h e scenery and t h e r e l e v a n t dwelling and r e c r e a t i o n a l c o n d i t i o n s . The l i v i n g conditions f o r f i s h e s i n t h e s t r e t c h which i s a f f e c t e d by the oper a t i o n of t h e r e s e r v o i r and e s p e c i a l l y by

-

chanpes i n water q u a l i t y , i n c l u d i n g temperatiire i n c r e a s e i n t h e minimum and decrease i n t h e maximum flood discharges and t h e i r

occurrence, - changes i n t h e r i v e r b e d and a s s o c i a t e d f l o r a , - c o n s t r u c t i o n of o b s t a c l e s f o r the movement o f f i s h e s upstream, a r e d r a s t i c a l l y changed. Thpse consequences include a decrease i n the tieterog e n e i t y of t h e p r e v a i l i n g ecosystems, i n c l u d i n g t h e e x p i r i n g o f migratory f i s h e s . The improvement of t h e water q u a l i t y and t h e decrease i n water temperature may r e s u l t i n t h e formation of a t r o u t zone i n t h e s t r e t c h downstream of t h e dam s i t e . I n t e n s i v e s p o r t f i s h i n g is o f t e n recorded i n t h e s e s t r e t c h e s , e s p e c i a l l y when t h i s a c t i v i t y is n o t permitted on t h e r e s e r w i r , e . g . because i t s water i s used f o r d r i n k i n g purposes. The flood c o n t r o l , water supply o r multi-purpose e f f e c t o f t h e r e s e r v o i r

o p e r a t i o n i n c r e a s e s t h e dwelling value o f t h e a f f e c t e d a r e a . Rut, downstream of the r e s e r v o i r , t h e r e o b t a i n s t h e r i s k o f a p o s s i b l e dam d e s t r u c t i o n . The probab i l i t y of such an event i s very low, b u t i t s consequences may be c a t a s t r o p h i c , d e s t r o y i n g economic values and t h r e a t e n i n g the population. The e f f e c t s of very l a r g e r e s e r v o i r s appear even a s f a r down as t h e e s t u a r y of t h e r i v e r i n t o t h e s e a , o r where i t e x p i r e s i n an a r e a without outflow. The drop i n t h e nutriment i n p u t and p o s s i b l e d e t e r i o r a t i o n i n water q u a l i t y by h w n a c t i v i t y m y l i m i t t h e e x t e n t and h e t e r o g e n e i t y o f the q u a t i c fauna including

336 f i s h e s , as w e l l as r e s t r i c t i n g f i s h prodiiction i n the c o a s t a l zone. The decrease i n sediment t r a n s p o r t may r e s u l t i n e r o s i o n , deepening t h e e s t u a r y and aggrav a t i n g sea-wave a c t i o n . The decrease i n discharges caused by t h e r e s e r v o i r o p e r a t i o n o r by water withdrawals r e s u l t s i n a n i n c r e a s e d p e n e t r a t i o n o f seawater upstream, w i t 6 a consequent i n c r e a s e i n s o i l s a l i n i t y , a l s o l e a d i n g t o a degradation of s a l t - r e s i s t e n t p l a n t s p e c i e s i n c l u d i n p e . g . d a t e palms. The s a l i n e e f f l u e n t s from i r r i g a t i o n schemes m y a l s o c o n t r i b u t e to t h i s degradation, a process which is more evident i n t h e dry period of low r i v e r discharges. ' h e r e s u l t i n g s t a g e i n the e s t u a r y l a r g e l y depends on the o p e r a t i o n both of

the r e s e r v o i r and t h e a s s o c i a t e d water users, The i n c r e a s e i n 1m discharges may cause a decrease i n t h e average s a l i n i t y , i . e . i t may shorter1 the period of upstream p e n e t r a t i o n of t h e s a l t y back w a t e r , which reduces t h e acreage of t h e a f f e c t e d a r e a . Another consequence may be t h e r a i s i n g of t r a c t i n g f o r c e s , and t h e i n t e n s i f i c a t i o n of t h e s e l f - p u r i f i c a t i o n p r o c e s s . I n t h i s way, a balanced r e s e r v o i r o p e r a t i o n can a l s o improve t h e conditions f o r c o a s t a l f l o r a , thereby augmenting

4.6.6

both a g r i c u l t u r a l and f i s h production.

E f f e c t of River T r a i n i n g and Open Channel Water Conveyance

The formation of r i v e r b e d s depends on hydrometeorologicel, hydrogeological, geomorphological and s o i l c o n d i t i o n s . I t i s a l s o a f f e c t e d by t h e occiirrence and s p e c i e s of t h e v e g e t a t i v e canopy

011

t h e r i v e r banks. The b a s i c n a t u r a l functions

of streams c o n s i s t o f (a)

drainape and water conveyance

(b)

i c e t r a n s p o r t during t h e w i n t e r and s p r i n g season,

Cc)

sediment and bed-load t r a n s p o r t , s o i l q u a l i t y r e g e n e r a t i o n ,

( d ) groundwater t a b l e and s o i l moisture r e g u l a t i o n , i . e . maintenance of cond i t i o n s f o r the r i v e r s i d e vegetation, ( e ) maintenance of c o n d i t i o n s f o r a q u a t i c l i f e and of envi.ronmenta1 balance. I n c i d e n t a l phenomena of t h e s e n a t u r a l f u n c t i o n s , such as floods, r e s t r i c t the p o s s i b i l i t i e s of u t i l i z i n g the a d j a c e n t a r e a f o r t h e various a c t i v i t i e s of human s o c i e t y , e . g . f o r i n t e n s i v e s e t t l e m e n t , i n d u s t r i a l and i n t e n s i v e a g r i c u l t u r a l prodtiction, mining, u n i n t e r n i p t e d in-stream water u t i l i z a t i o n e.g. navigation and water power g e n e r a t i o n . The v a r i a b i l i t v of t h e channels of n a t u r a l water c o u r s e s , t h e i r f l u c t u a t i n g water l e v e l s , changinE discharges and a l s o i c e phenomena n e g a t i v e l y i n f l u e n c e t h e socioeconomic fiinctions of w a t e r . For t h i s reason water courses a r e t r a i n e d and c a n a l s f o r water conveyance constnicted with t h e aim o f ( a ) improving t h e conditions of water supply and drainage, in-stream and on-side water u s e , (b)

r e s t r i c t i n g inundations and conseqiient economic l o s s e s ,

337 ( c ) adapting t h e r i v e r b e d t o t h e changing d i s c h a r g e s , inland water t r a n s p o r t requirements, power genera t i o n , sediment t r a n s p o r t o r ice regime phenomena, (d)

increasin,q t h e dwelling value o f the a d j a c e n t a r e a , s t a b i l i z i n g t h e r i v e r banks and r i v e r bottom, achieving d i r e c t i o n a l

(e) s t a b i l i z a t i o n , r e s t r i c t i n g t h e e r o s i o n process and removing i t s consequences, (f)

improving t h e groundwater regime,

(g)

adapting the riverbed t o t h e consequences of d i v e r s i o n dams and weir

c o n s t r u c t i o n , as w e l l as of the c o n s t r u c t i o n of comnunication l i n e s , urban, indirs t r i a l and a g r i c i i l t i i r a l development, (h)

improvinp t h e water q i i a l i t y , safemiarding t h e d e s i r e d s a n i t a r y conditions

and t h e requirements o f a e a t h e t i c enjoymentlTab. 4 . 2 1 ) . The

unavoidable

precondition f o r ensuring the d e s i r a b l e e f f e c t of r i v e r

t r a i n i n g i s t h a t n a t u r a l fimctions of t h e stream mustnot come i n t o c o n f l i c t with t h e d e s i r e d goals. The flow of n a t u r a l r i v e r s and streams is f r e q u e n t l y almost s t e a d y , i . e . changes very slowly with time. Tlnsteady flow occiirs as flood waves o r t r a v e l l i n e siirges. In natiiral r i v e r b e d s , t h i s flow i s non-uniform,

changing

slowly o r suddenly i n t h e magnitiide and d i r e c t i o n o f t h e v e l o c i t y along t h e s t r e a m l i n e . S t r i c t l y iiniforni flow r a r e l y e x i s t s i n such channels. The cross sect i o n of a t r a i n e d stream u s u a l l y has a simple geometric shape. The f l o w i n such a canal i s g e n e r a l l y considered t o be uniform, only having slaw changes of t i j r e c t i o n and no changes with d i s t a n c e i n t h e value of t h e v e l o c i t y along a s t r e a m l i n e , with t h e exception of s t r e t c h e s upstream of drops, weirs and d i v e r s i o n dams, where non-uniform flow occurs. The n a t u r a l r i v e r b e d , though o f t e n n o t s i i f f i c i e n t l y s t a b l e i n t h e short-term,

is a r e s u l t of the a c t i v i t i e s of e x t e r n a l n a t u r a l f o r c e s , and may be considered t o h e i n long-term e q i i i l i b r i i m with them. The p r i s m a t i c channel of a t r a i n e d r i v e r with a iiriiform flow cannot correspond t o t h e complicated conditions of the o r i p i n a l s t a t e and, d e s t r o v i n p t h i s long-term balance, freqiiently has a n e g a t i v e e f f e c t on some of the h a s i c natiiral functions of the stream o r r i v e r .

The b i o l o g i c a l eqiiilibrium i n t h e o r i g i n a l ecosystems on t h e banks is a result of an i n t e r p l a y of t h e o r i g i n a l groundwater l e v e l and corresponding s o i l moistlire f l u c t i i a t i o n . The conditions f o r t h e e q i i i l i b r i i m of a q u a t i c ecosystems depend on t h e i n t e r p l a y of water depth, flow r a t e s , the morphology and m a t e r i a l of t h e channel, and on t h e a q u a t i c f l o r a . E c o s y s t e m , both a q u a t i c and on t h e banks, g e n e r a l l y need heterogeneous c o n d i t i o n s f o r t h e i r development o r s u r v i v a l . These conditions a r e u n i f i e d by r i v e r t r a i n i n g , o r newly and uniformly e s t a b l i s h e d by t h e headrace o r t a i l r a c e c o n s t r u c t i o n .

l h i f i e d conditions a r e not acceptable

f o r many r e l e v a n t s p e c i e s . This r e s u l t s i n a d e c l i n e i n t h e i r h e t e r o g e n e i t y , s i g n a l i z i n g t h e d i s t u r b e d b i o l o g i c a l balance. These changes occur gradually from t h e beginning of t h e c o n s t r u c t i o n work. RiTJer t r a i n i n p , i f n o t accompanied hv t h e c o n s t r u c t i o n of weirs and dams t o

338 TABLE 4.21

Impact of r i v e r t r a i n i n g Hydraulic parame t e r s

Discharges

Water Table

Increased slope of t h e channel

Limited flooding

Extended cross s e c ti o n

Restructed Change i n water tempenatural fer- r a t u r e t i l i z a tion

Increased velocity of f l m

Restricted groundwater recharge

Increased drainage rate

Decrease i n Rise i n b a s e flow groundwater d u r i n g vepe- t a b l e tation period

Increase

Increase i n winter discha rres

Decrease

Change o f sedimentation and e r o s i o n

Increase i n infiltration

F l o r a and Fauna

helliqg value

Change i n water q u a l i t y

Increased flood control

Change i n water f l o r a

Improved a g r i c u l tiire

Decrease i n Change i n infiltrawater fauna including tion f i s h species

Deteriorated s o i l regenera t i o n

Drop i n gromdwater table

Improved navigation and hydropower genera t i o n

Waterlogging Excessive drainage

Chang? of riparian vegetation

improved a c c e s s i b i l i ty Negative impact o f water tourism

C h e c k l i s t of t h e probable impact of r i v e r t r a i n i n g on t h e w a t e r cycle and ripar i a n environnier.t. s w e l l t h e water t a b l e , results i n a s u b s t a n t i a l drainage e f f e c t . Such an e f f e c t m y be supported by t h e a s s o c i a t e d i r r i g a t i o n network and r e s u l t i n a 10-20% i n c r e a s e i n annual outflow i n the f i r s t 4-5 y e a r s a f t e r c o n s t r u c t i o n . I n the n e x t p e r i o d , t h e drainage impact on t h e annual outflow i s n o t as s u b s t a n t i a l and mainly occurs as a r e g u l a t i n g e f f e c t , i n c r e a s i n p low d i s c h a r g e s . Its e f f e c t on flood occurrence i s c o n t r o v e r s i a l . Decreased moisture content i n t h e upper s o i l l a y e r i n c r e a s e s t h e i n f i l t r a t i o n c a p a c i t y , thus lowering t h e s u r f a c e r u n o f f . The increased flow c a p a c i t y o f t h e r i v e r b e d , and e s p e c i a l l y o f t h e a s s o c i a t e d drainage network, i n c r e a s e s t h e flow v e l o c i t y and c o n t r i b u t e s t o t h e i n c r e a s e i n flood d i s c h a r g e s . The drainage e f f e c t of r i v e r t r a i n i n g and a s s o c i a t e d network i n c r e a s e s t h e p r o b a b i l i t y o f flood occurrence and t h e value of flood discharges, depending on t h e s o i l and moistlire c o n d i t i o n s , i . e . depending on t h e share of t h e balancing e f f e c t of t h e increased i n f i l t r a t i o n c a p a c i t y o f t h e drained s o i l layer.

339 River t r a i n i n g d r a s t i c a l l y changes t h e conditions f o r sediment t r a n s p o r t . This can also b e analyzed on t h e b a s i s of t h e following simple formula, derived from t h e water depth, the flow r a t e and t h e g r a i n s i z e o f t h e bed-load mixture

(4.33) de - c h a r a c t e r i s t i c g r a i n s i z e of t h e bed-load mixture h

- water depth

(m) fm)

v X - minimum flow r a t e causing the o n s e t of bed-load t r a n s p o r t (m. s-1 ) K

-

c o e f f i c i e n t o f t h e sediment t r a n s p o r t (almost s t a b l e and = 216 according t o Scharnow)

s-3)

River t r a i n i n g i n f l u e n c e s both t h e water depth and t h e flow r a t e s , and i n t h i s wav changes also t h e c h a r a c t e r i s t i c s i z e of t h e bed-load mixture and t h e i n t e n s i t y of t h e bed-load

t r a n s p o r t . T h i s change i n t h e bed-load t r a n s p o r t may

r e s u l t i n demands f o r f u r t h e r r i v e r t r a i n i n g i n t h e s t r e t c h downstream. River t r a i n i n g u s u a l l y has a p o s i t i v e i n f l u e n c e on t h e i c e regime i n t h e r e g u l a t e d s t r e t c h , b u t due t o i t s a c c e l e r a t i n g e f f e c t has n e g a t i v e impact on unregulated s t r e t c h e s downstream; Ttie n e g a t i v e impacts o f r i v e r r e p i l a t i o n r e s u l t mainly from t h e reduction of

the stream l e n g t h , frcm the extension o f t h e c r o s s s e c t i o n and from the renroval of t h e r i v e r s i d e v e g e t a t i v e campy. This augments t h e drainage e f f e c t , increases t h e flow r a t e s , a c c e l e r a t e s t h e outflow and, l i m i t i n g groundwater recharge, res u l t s i n the r e d u c t i o n of evaporation nad e v a p o t r a n s p i r a t i o n . River t r a i n i n g may r e s u l t i n c u r t a i l i n g t h e d u r a t i o n o f runoff from the source t o t h e e s t u a r y , even t o t h e e x t e n t of reducing i t t o h a l f the o r i g i n a l diiration. The decrease i n groundwater recharge l i m i t s t h e r e g u l a t i n g e f f e c t o f groundwater on s u r f a c e water d i s c h a r g e s , r e s u l t i n g i n a decrease i n average discharges d u r i n g t h e sumner p e r i o d and i n an i n c r e a s e i n discharges i n w i n t e r , thus causing

a drop i n a g r i c u l t u r a l production i n t h e a d j a c e n t a r e a . The impact o f

headrace, t a i l r a c e and f e e d e r , l i n k and o t h e r conveyance canals

i s more d r a s t i c : They change the groundwater regime and a s s o c i a t e d ecosystems, they may cause waterlogging with a s s o c i a t e d s a l i n i t y hazards i n v a s t a r e a s , they change t h e i n f r a s t r u c t u r e of t h e a r e 3

-

s e v e r i n g t h e cornminication network and

r e s t r i c t i n g t h e a c c e s s i b i l i t y of c e r t a i n a r e a s both f o r t h e population and the w i l d l i f e . T h e i r c o n s t n i c t i o n restricts w i l d l i f e occurrence, worsening t h e l i v i n g c o n d i t i o n s , e s p e c i a l l y o f r a r e s p e c i e s , and permits f i s h t o escape from r e s e r v o i r s and r i v e r s . Conveyance c a n a l s enable t h e t r a n s f e r of p o l l u t i o n and under c e r t a i n circumstances form favourable conditions f o r the occurrence o f i n s e c t s and f o r desease dissemination. Nevertheless, an improvement i n the conditions f o r water trans-

340 p o r t , power g e n e r a t i o n , o t h e r multi-purpose u t i l i z a t i o n o f w a t e r , s e t t l e m e n t , a g r i c u l t u r a l and i n d u s t r i a l production, r e c r e a t i o n form t h e precondition f o r a development boom i n the a d j a c e n t a r e a (Tab. 4.20). River t r a i n i n g has to be r e a l i z e d only as a n i n t e g r a l p a r t of an improvement i n t h e water regime i n t h e a d j a c e n t a r e a . I t i s , t h e r e f o r e , indispensable ( a ) t o simultaneously a c c e p t measiires f o r changinp t h e s u r f a c e runoff i n t o groundwater r u n o f f , e s p e c i a l l y on t h e f o r e s t and a g r i c u l t u r a l lands, (b)

t o simul taneously a c c e p t measures f o r achieving a b i o l o g i c a l equilibrium

i n t h e ecosystems of t h e r i v e r v a l l e y and t h e catchment, e s p e c i a l l y by d e t e m i n i n g t h e e c o l o g i c a l l y optimum r a t i o o f a r a b l e land, ( c ) t o s o l v e r i v e r t r a i n i n g problems n o t only h y d r a u l i c a l l y , t e c h n i c a l l y and economically, b u t a l s o from a n environmental p o i n t of view. Streams and r i v e r channels a r e formed by t h e lonffterm impact of hydrometeor o l o g i c a l , geological and b i o l o g i c a l processes. S u b s t a n t i a l changes i n the o r i g i n a l r i v e r bed, i n its r o u t e and i n t h e accompanying v e g e t a t i v e canopy during r i v e r t r a i n i n p m y d i s r u p t t h e balance which has been e s t a b l i s h e d by n a t u r a l f o r c e s and endanger t h e course of n a t u r a l f u n c t i o n s . Only when t h e c o n s t r u c t i o n r e s p e c t s t h e o r i g i n a l s t a t e , the main n a t u r a l functions

and b a s i c i n t e r r e l a t i o n s h i p s , a s occurs a f t e r minor amendments t o t h e

o r i g i n a l r i v e r bed and through t h e c o n s t r u c t i o n of p r o t e c t i o n dykes adapted t o the topography of t h e t e r r a i n , can t h e consequent state be p r e d i c t e d with s a t i s f a c t o r y accuracy and t h e r e f o r e be mnaged t o o f f e r maximum b e n e f i t s With minimized environmental l o s s e s .

341 Chapter 5

WATER DEVETBPMENT

5.1

ANI)

MANAGEMENT POLICY

WATER MANAGmW ACTIVITIES

ORGANIZATIONS

Water mnagement i s a complex of a c t i v i t i e s , designed t o meet t h e demands of economic development and aiming a t a n optimum development and u t i l i z a t i o n of water r e s o u r c e s , depending on t h e i r q u a l i t y and a v a i l a b i l i t y i n space and time, and a t t h e c r e a t i o n of an optimum l i v i n g environment, through t h e conservation of water r e s o u r c e s , t h e i r p r o t e c t i o n a g a i n s t exhaustion and d e t e r i o r a t i o n , and through t h e p r o t e c t i o n of human s o c i e t y a g a i n s t t h e harmful e f f e c t s of w a t e r . The r a t i o n a l management of water resources u t i l i z a t i o n has a s i t s aim, i n cormion with development g e n e r a l l y , an enhancement of t h e conditions f o r h w n l i f e and must, t h e r e f o r e , be recopnized as an i n t e g r a l p a r t of s o c i a l and economic development. I n periods of predominantly single-purpose water u t i l i z a t i o n , i n a r e a s with abundant w a t e r r e s o u r c e s , low population d e n s i t y , s c a t t e r e d snBll-scale i r r i g a t i o n networks and a l o w degree of i n d u s t r i a l i z a t i o n , s o c i a l and i n d i v i d u a l water requirements can be s a t i s f i e d by t h e a c t i v i t i e s of water u s e r s o r d i f f e r e n t l o c a l o r g a n i z a t i o n s . To achieve a h i g h e r production and a b e t t e r water u t i l i z a t i o n , various s p e c i a l i z e d o r g a n i z a t i o n s a r e formed w i t h t h e aim of ensuring water supply, and/or d i s p o s a l , i r r i g a t i o n development, power g e n e r a t i o n , inland n a v i g a t i o n , p r o t e c t i o n a g a i n s t floods e t c . I n t h e n e x t development s t a g e , r i v e r boards and o t h e r a u t h o r i t i e s a r e formed i n o r d e r t o achieve a g r e a t e r e f f i c i e n c y i n t h e management of w a t e r development t o c o o r d i n a t e t h e multipurpose water u t i l i z a t i o n and p r o t e c t t h e s o c i e t y a g a i n s t t h e harmful

( e f f e c t s of w a t e r .

The supreme r e g u l a t o r y a c t i o n concerning w a t e r , i n o r d e r t o meet t h e dernands

a r i s i n g o u t of h w n a c t i v i t i e s and t h e necessary p r o t e c t i o n of t h e environment,

is a government r i g h t and o b l i g a t i o n . The del-egation of a u t h o r i t y from t h e c e n t r e v a r i e s f r m country t o country and, i n t h e case of f e d e r a l i z e d and developing c o u n t r i e s , even w i t h i n t h e same c o u n t q , depending on t h e given soc i a l and p o l i t i c a l framework, t h e l e g a l regime of water management, t h e a v a i l a b i j i t y of w a t e r i n r e l a t i o n t o i t s u s e , and o t h e r r e g i o n a l d i v e r s i t i e s . Jxgal and i n s t i t u t i o n a l f a c t o r s p l a y an important r o l e i n t h e o r g a n i z a t i o n of t h e r e s p o n s i b i l i t i e s f o r water resources management. The i n s t i t u t i o n a l framework Is aimed a t s a t i s f y i n g t h e d i f f e r e n t i n t e r e s t s of all w a t e r u s e r s , and a l s o a t f a c i l i t a t i n g t h e c o r r e c t implementation of a l l water-related progranunes. Decision-<ing

p o l i c i e s and

i s i n v a r i a b l y c l o s e l y linked with t h e r e l e v a n t poli-

t i c a l , economic and s o c i a l processes which a r e t h e r e s u l t o f t h e i n t e r a c t i o n of

a niunber o f bodies (Tab. 5.1).

LAW cons ti t i i t ion c i v i l law p u b l i c works law labour l a w t a x a t i o n law

CIAKING

WATER ETANAGENENT water law enforcement r e g i s t r y of w a t e r r i g h t s c a d a s t e r of water r i g h t s r i g h t s of way f o r water uses

POTdlCY-PIAKING, n a t i o n a l water p o l i c v i n t e r n a t i o n a l waters policy water management strategy

& PLANNIVG n a t i o n a l o b j e c t i v e s and goals i n t e r n a t i o n a l poIicy s e c t o r a l development policy

water p r i c i n g legal tools reimbursement of c o s t s water a d m i n i s t r a t i o n

waterway development and maintenance hydrographical services water p o l l u t i o n control

inland navigation timber f l o t a t i o n r a i l way, highway and a i r t r a n s p o r t development

water supply f o r industry water p o l l u t i o n control

r i g h t s of way f o r water uses g r a n t i n g o f water r i g h t s water d i s p u t e s d e c i s i o n s

hydropower g e n e r a t i o n thermal and nuclear water f o r thermal & power development n u c l e a r power d i s t r i b u t i o n networks genera t i o n water p o l l u t i o n con t r o 1

water supply f o r irrigation l i v e s t o c k , processing and f i s h breeding water p o l l i l t i o n control

approval of w a t e r development p r o j e c t s p r o j e c t design project construction p r o j e c t operation technical a s s i s t a n c e

w a t e r law water uses law flood c o n t r o l law p o l l u t i o n control

law

IVTERIOR municipal developurban & r u r a l water ment SupPlY waste water t r e a t ment and d i s p o s a l water p o l l u t i o n control 1

w a t e r supply and use waste water d i s p o s a l

w

c N

~

AGRI( agricultural development i r r i g a t i o n drainage fisheries river training watershed management

1

E N V I R ONME NT P R 0 TE C T I 0 N n a t u r a l resources flood c o n t r o l erosion control

RECREATION

pol 111t i o n c o n t r o l

L

I

I

hydrologj c a l s e r v i c e s hydrogeological s e r v i c e s d a t a monitoring & processing h y d r a u l i c and hydrologic

research I n t e r r e l a t i o n s h i p between water management and o t h e r sectors.

I water supply f o r recreation waste water treatment and d i s p o s a l

recreation services n a t i o n a l parks administration tourism p r o m t i o n s p o r t promotion

I

343 Four basic groups can be distinguished among water management a c t i v i t i e s : (a)

legal administration,

(b)

development a c t i v i t i e s ,

(c)

economic a c t i v i t i e s (Tab. 5.2),

(d) o t h e r mnagement a c t i v i t i e s ( i n c l . services - Tab. 5.3). Depending on the individual c h a r a c t e r i s t i c s of a given country, the i n s t i t u t i o n a l framework f o r water resources management includes the agencies with polit i c a l and regulatory functions, working e . g. under regional a u t h o r i t i e s , and l e g i s l a t i v e bodies, working under a centralized water o r other national authori-

ty. I n order t o r e s t r i c t possible c o n f l i c t s and provide a view which unifies nationwide i n t e r e s t s , the supreme coordination is usually entrusted t o a spec i a l national authority, t o one of the ministries responsible f o r the various water development aspects such a s the Ministry of Water and Energy / Agriculture / Forestry / Public Works or t o a multi-sectoral commission o r special i n s t i t u t e . To avoid any ambiguity, the exercising r e s p o n s i b i l i t y has t o be separated from the administering arid controlling/monitoring responsibility. The d i v e r s i t y of i n s t i t u t i o n a l integration i n water management depends on the separate consideration of such s p e c i f i c problems as municipal and industrial water supply arid waste water disposal, groundwater development, i r r i g a t i o n and drainage, f o r e s t management, hydropower generation, inland navigation e t c . , and m y be r e f l e c t e d by the existence of various organizations fqr some of these purposes. Nevertheless, a l l matters r e l a t i n g to water should be regarded as forming p a r t of an i n t e g r a l whole based on the unity of the relevant catchments. The s t r u c t u r e of r i v e r boards corresponds t o t h i s t e r r i t o r i a l principle, whereas the i n s t i t u t i o n a l s t r u c t u r e of water supply and waste water disposal organizations o f t e n depends on the p a r t i c u l a r in-house p o l i t i c a l arrangements. I n order t o achieve the economic and s o c i a l goals of a country i n consideration of i t s environmental l i m i t a t i o n s , e x i s t i n g surface and groundwater resources have t o be assessed, t h e i r q u a l i t y , n a t u r a l functions and present uses for a l l purposes i d e n t i f i e d , the future demands i n the medium and l o n g t e r m estimated, and both the medium and long-term plans formulated on the basis of an optimization process. Water resources planning 3s an i n t e g r a l p a r t of water development and management i s a continuous process, whose implementation basically requires: (a) a fixed s t r a t e g y of water resources development and environmental protection, (b) a f l e x i b l e t a c t i c s of water requirements and withdrawals management, (c) an operational control and checking of water q u a l i t y and occurrence, water withdrawals, e f f l u e n t s and t h e i r q u a l i t y , in-stream water uses and of measures of environmental protection.

344 5.2

PAltZT,OXES

OF WAl'ER RESOTRCES DEVEILX'PEhT

The course of water requirements and water withdrawals is g e n e r a l l y d e t e r m i n i s t i c , whereas t h e course of water a v a i l a b i l i t y i s d e t e r m i n i s t i c only within the l i m i t s of t h e r e a l i s t i c f o r e c a s t o f groundwater and s u r f a c e water a v a i l a b i l i t y , which g r e a t l y depends on weather ( r a i n ) f o r e c a s t s . I t i s , t h e r e f o r e , b a s i c a l l y stochastic: i n t h e long teim. The occurrence of w a t e r requirements and s u r f a c e a v a i l a b i l i t y is u s u a l l y c o n t r a d i c t o r y : t h i s leads t o t h e f i r s t paradox which has t o be d e a l t with i n water resources development: IN THE PERiOD O F HIGH WATER REQUIREMENTS A S U B S T A N T i A L L Y LOWER WATER QUANT I T Y E X I . ~ T S I N I I A T U R A L UNREGULATED RESOURCES T.YAN .rtJ PERIODS

OF LOW WATER

PEOIJIRE,'IE:iTS.

A gradual i n c r e a s e i n t o t a l water requirnierlts freqiiently r e s u l t s i n

3

situa-

t i o n where, during water u t i l i z a t i o n , a p o i n t is reached when water requirements cannot be s a t i s f i e d by an i n c r e a s e i n water withdrawals from groundwater o r un-. r e g u l a t e d discharges only. The water a v a i l a b i l i t y has t o be r e g u l a t e d by a r t i f i c i a l water accunnilation. Daily and weekly f l u c t u a t i o n s can e a s i l y be balanced by small r e s e r v o i r s o r water tanks. Seasonal f l u c t u a t i o n s i n water requirements irlanifest a cornparatively high d i s p e r s i o n of minimuni and m x i m m v a l u e s , which c a l l f o r a n overu t i l i z a t i o n of a v a i l a b l e water resources and claim a s u b s t a n t i a l i n c r e a s e i n t h e parameters of r e l e v a n t development p r o j e c t s .

As the number of r e s e r v o i r s i n c r e a s e s , g r a d u a l l y less and less f e a s i b l e l o c a l i t i e s o r less f e a s i b l e arrangements f o r supplementing t h e required supply a v a i l a b i l i t y have t o be used, including d i s t a n t water r e s o u r c e s , deep groundwater s t r a t a , and, i n t h e l a s t s t a g e of development, even resources w i t h low q u a l i t y and unconventional water r e s o u r c e s . This is t h e reason f o r t h e rise i n t h e average investment, o p e r a t i o n a l and w i n t e n a n c e c o s t s f o r water resources withdrawal, conveyance, p u r i f i c a t i o n and d i s t r i b u t i o n . I n a d d i t i o n , e f f l u e n t s d e p r e c i a t e t h e q u a l i t y of a v a i l a b l e water resources and waste water treatment becomes necessary, thus f u r t h e r i n c r e a s i ~ n g r e l e v a n t c o s t s . This l e a d s t o t h e second paradox which has t o be d e a l t with i n water resources development: THE AVERAGE INVESTMEtJT AND OPERATIONAL CDSTS PER CUBIC METER OF WATER SUPPLIED GROWS E X P O l I E N T l A L L Y , EVEN

THOUGH THE S P E C I F I C COST OF WATER SUPPLY

FOR I N D I V I D U A L WATER DEVELOPMENT PROJECTS DECREASES DOWN TO A CERTAIN LEVEL WITH THE I N C R E A S I N G QUArJTITY OF WATER S U P P L I E D .

Problems a s s o c i a t e d w i t h a l a c k of water o r inadequate water q u a l i t y a r e solved by t h e c o n s t r u c t i o n and subsequerit o p e r a t i o n of water p r o j e c t s . Water development p r o j e c t s which have i n good time been implemented c r e a t e a temporaty surplus of w a t e r t h a t cannot be f u l l y u t i l i z e d inmediately a f t e r t h e i r com-

3 45 p l e t i o n . This leads t o t h e t h i r d paradox which has t o be d e a l t with i n water resources development : THE TEMPORARY SllRPLlJ.5 OF hA.TER OWER~TMG211 I!..TE?Z :Z< FOR WATER O V E R U T I L I Z A -

T I O l i WirTHOUT AIJY IMPORTAlr'T NEGATIVE E:CONOMIC ZFFECYZ, Fi..?l.!S

PRECO?:DITlONS FOR A

SUBSEQUENT WATER S C A R C I T Y .

Any p e r i o d of temporazy surplus of water ends by achieving an equilibrium between w a t e r resources and over-excessive water requirements. Any f u r t h e r lack of water i s again solved by c o n s t r u c t i n g a new p r o j e c t ( F i g . 5.1). This c y c l e

is t o be r e p e a t e d , extending t h e water resources development t o more d i s t a n t areas, u n t i l a s t a g e of a u t i l i z a t i o n o f economically f e a s i b l e water resources

is achieved. This leads t o t h e f o u r t h paradox t h a t has t o be d e a l t with i n water resources development: A L L A V A I L A B L E WATER RESOURCES A R E USEL, BEFORE E F F I C I E N T WATER-SAVING

TECM-

NIQUES A R E A P P L I E D .

1

I

I

Active balance

Gradual increase in

of water resaurces

water utilization

and needs

(and project efficiency)

investment and

P a ssive ba I a nc e

construction process

of water resources and needs

F i g . 5.1. Schematic i n t e r p r e t a t i o n of t h e c y c l e of water resources development and water use r a t i o n a l i z a t i o n . A s o c i e t y should form pre-conditions for i t s sound development by adapting

i t s w a t e r requirements t o water a v a i l a b i l i t i e s . But t h i s r u l e f u n c t i o n s under extreme s i t u a t i o n s only: When water a v a i l a b i l i t i e s are sharply r e s t r i c t e d , water

is used for indispensable u s e s only. The increased a v a i l a b i l i t i e s cause water t o be used f o r less and less necessary uses. Under t h e s i t u a t i o n of a long-term water s u r p l u s , growing w a t e r withdrawals d i f f e r more and more from t h e i n d i s pensable water requirements. This f a c t , accompanied by an exponential i n c r e a s e i n s p e c i f i c investment and o p e r a t i o n a l c o s t s caused by u t i l i z i r g less and l e s s f e a s i b l e p r o j e c t sites f o r growing t o t a l water withdrawals, leads t o t h e f i f t h paradox that has t o b e d e a l t w i t h i n water resources development:

346 GRADUALLY I N C R E A S I N G DEVELOPMENT COSTS GRADUALLY SAFEGUARD L E S S AND L E S S IMPORTANT WATER REQUIREMENTS.

STRATEGY OF WATER RESOURCES DEVELOPMENT

5.3

By formulating t h e desired water res'ources development o b j e c t i v e s , i t is possible t o e s t a b l i s h a s t r a t e g y f o r t h e r a t i o n a l conservation and step-by-step development of those resources: i . e . t o e s t a b l i s h procedures f o r i n c r e a s i n g the a v a i l a b i l i t y and subsequent u t i l i z a t i o n and d i s p o s a l of water re5ources. A conunon o b j e c t i v e is f o r example t h e conservation of t h e n a t u r a l functions of water resources w i t h i n t h e framework of t h e n a t u r a l environment, e s p e c i a l l y of the q u a l i t y and optimum a l l o c a t i o n of these water resources among present and p o t e n t i a l water u s e r s , i . e . t h p i r optimum multi-purpose u t i l i z a t i o n w i t h i n the framework of the e x i s t i n g and expected s o c i a l and economic s t r u c t u r e (Fig.

5.2). Tang-term planning, a b a s i c t o o l f o r helping t o achieve t h r s e o b j e c t i v e s , c o n s i s t s of the f o l l m i n g s t e p s : ( a ) i d e n t i f i c a t i o n of a v a i l a b l e s u r f a c e and groundwater resoiirces, evaluat i o n of t h e i r q u a l i t y and uses i n relevant categories of water u t i l i z a t i o n , which r e q u i r e s an information system o r i t s establishment; (b) evaluation of water denmnds i n t h e medium texm ( f i v e y e a r s ) and of water needs i n t h e long term, t o match t h e physical and socio-economic condit i o n s , n a t i o n a l and regional development plans ; t r e a t i n g i n t e r r e g i o n a l and i n t e r n a t i o n a l problems i n the context of n a t i o n a l i n t e r e s t s ; ( c ) compilation of balances of water resources and needs, d e t e c t i n g c r i t i c a l a r e a s , p r e s e n t and f u t u r e problems; (d) formulation of a l t e r n a t i v e scenarios and s t r a t e g i e s , appropriate f o r solving p a r t i c u l a r n a t i o n a l , regional and l o c a l problems; ( e ) optiniization and evaluation of these scenarios and s t r a t e g i e s , with respect t o t h e i r advantages and disadvantages, environmental and socio-economic after-effects,

o t h e r implications and unavoidable repercussions, b e n e f i t s and

l o s s e s , and, l a s t but not l e a s t , t h e investment, operation and associated costs required f o r t h e f u l l completion and successful operation of t h e p r o j e c t o r cornplex implenientation of required arrangements i n t h e framework of the present and f u t u r e socio-economic s t r u c t u r e ; (f)

s e l e c t i o n of t h e optimum scenario and s t r a t e g y , i . e . t h e most appro-

p r i a t e f o r s o l v i n g p a r t i c u l a r regional and l o c a l problems, capable of being pursued on a phased and f l e x i b l e b a s i s , taking i n t o account environmental and socio-economic l i m i t a t i o n s i n c l . t h e lack of s k i l l e d human resources and t h e i n e r t i a of l o c a l c u s t o m , obsolete s o c i a l s t r u c t u r e , t r a d i t i o n a l labour methods, jeopardizing e s p e c i a l l y t h e successful i n t r o d u c t i o n of modern a g r i c u l t u r a l p r a c t i c e s , and t h e implementation and operation of modem i r r i g a t i o n systems;

347

DE V ELOPM ENT SC ENA R I0S

!

Fig. 5.2. Block diagram f o r a l l o c a t i o n of water resources i n l i n e with development of t h e s o i l resources and i n d u s t r y . Any r a t i o n a l development tends t o the u l t i m a t e s t a g e of a sustained u t i l i z a t i o n of t h e n a t u r a l p o t e n t i a l by using the mininim [ratter and e n e r w , which should be checked i n relevant time horizons. (g) approval and acceptance of the p r e f e r r e d scenarios and s t r a t e g y by a l l c e n t r a l and regional a u t h o r i t i e s , involving t h e existence of an appropriate l e g a l and i n s t i t u t i o n a l framework and two-way co-ordination among a l l l e v e l s of responsible a u t h o r i t i e s during t h e planning process; (h) budgeting t h e gradual implementation w i t h i n t h e framework of medium-term p l a n s , whose aim i s t o i n t e g r a t e planned programes of d i f f e r e n t s e c t o r s , define i n f i n a n c i a l terms t h e annual n a t i o n a l , regional and l o c a l o b j e c t i v e s , and t o a l l o c a t e funds f o r achieving those medium-term objectives ; (i)

monitoring the p e r f o m n c e of t h e plan, modifying i t , i f required by

348 changed circunls tances, needs and p r i o r i t i e s . Significant goals i n mediiun-term plan implementation include the hannonization o f : ( a ) the development of the natural environment, balancing the needs of the u t i l i z a t i o n of natural resources and the necessity of environmental protection i n order t o decrease t h e negative impact of water u t i l i z a t i o n on the hydrolog i c a l cycle, which reduces the volume of water available and leads t o a deterioration i n its quality, (b) the water needs of present and potential water users with a view t o the required water q u a l i t y and quantity and to the optimum economic conditions.

To achieve the above goals, the following three principles have t o be respected: F i r s t principle of water development strategy: KEEPING THE DEVELOPMENT OF WATER RESOURCES I N L I N E WlTH THE OVERALL S O C I O ECONOMIC DEVELOPMENT

BY RESPECTING THE D I V E R S I T Y OF THE OCCURRENCE OF WATER

RESOURCES UNDER NATURAL C O N D I T I O N S .

direct pr 0 duct ion costs

3

Fig. 5.3. Graphic representation of the r e l a t i o n of the t o t a l d i r e c t production cost and the expenditure on inf r a s t r u c t u r a l investment and opera t i o n according t o Czuka (1975). Excess i n f r a s t r u c t u r a l capacity (path A A2 B B2 C) enables lower production costs. Economic development requires a proportional development i n the f i e l d s of both productive and i n f r a s t r u c t u r a l projects. Expenditures i n the sphere of the i n f r a s t r u c t u r e decrease the cost of d i r e c t production a c t i v i t y . Production costs

349 increase with decreasing i n f r a s t r u c t u r a l costs u n t i l a minimum infrastructtiral value is attained which is indispensable f o r obtaining any output from the d i r e c t production a c t i v i t y .

The national objective i s to increase production a t the minimum t o t a l c o s t , i . e . including the expenditures both i n d i r e c t production a c t i v i t y and i n the i n f r a s t r u c t u r e . The curve expressing t h e r e l a t i o n between d i r e c t production c o s t s , investment and operation costs i n the sphere of i n f r a s t r u c t u r e , a l s o including investment and operation costs f o r water development projects, is hyperbolic. It moves gradually away from the zero point i n time, due t o more developed and f i n a n c i a l l y more and more demnding investments. The way to technically more developed production may be twofold: ( a ) with d e f i c i e n t i n f r a s t r u c t u r a l capacity, requiring higher d i r e c t production c o s t s , (b) with excess i n f r a s t r u c t u r a l capacity, permitting d i r e c t production costs t o be maintained a t a low level. The development scenario with excess i n f r a s t r u c t u r a l capacity (A A2 R B2 C)

-

(Fig. 5.3) enables lower production c o s t s , thus forming more favourable product i o n s , a t t r a c t i n g productive investments and dynamically increasing living standards. The development scenario with d e f i c i e n t i ? f r a s t r u c t u r a l capacity, which appears i n countries with slowly developing economies (path A B1 B C1 C ) , leads to higher production c o s t s , which a r e then d i f f i c u l t to reduce i n the period of a s u f f i c i e n t i n f r a s t r u c t u r e . I t is therefore advantageous t o develop water investments belonging p a r t l y , i n some economic models, t o the production sphere, f i v e t o ten years before the f u l l development of the production sphere. Second principle of water development strategy: RESPECTING THE L I M I T S OF THE NATTIRAL ENVIRONMENT I N THE STAGE OF I T S FULL, RATIONAL A N D LASTING U T I L I Z A T I O N FOR THE SAKE O F HUMAN SOCIETY.

The basic objective of water development a s an integral p a r t of s o c i a l and economic development can be defined simply e i t h e r a s

-

the maximization of the l i v i n g standard f o r the population o r i n i t s second

extreme, under completely d i f f e r e n t local o r environmental conditions,

-

the safeguarding of the survival of the population. The second objective may appear a s decisive, not only under the s p e f i c i c con-

d i t i o n s of underdeveloped populated countries o r areas with extreme c l i m t o l o g i c a l conditions, but a l s o i n the conditions of some developed areas whose development has already exceeded the environmental l i m i t s , i . e . the potential of renewable n a t u r a l resources. As mentioned before feedbacks e x i s t , causing a d e t e r i o r a t i o n i n the environmental q u a l i t y a s a r e s u l t of any o v e r - u t i l i z a t i o n . The resources p o t e n t i a l of a c e r t a i n area can be defined as its a b i l i t y to s a t i s f y permanently t h e needs of society, a r i s i n g from its socio-economic deve-

3 50 lopment. I n can be expressed by a m u l t i t u d e of p h y s i c a l , chemical, b i o l o g i c a l and a e s t h e t i c values and be simply represented by t h e number of i n h a b i t a n t s whose nourishment and economic development i t i s p o s s i b l e t o p e i m n e n t l y s u s t a i n by a g r i c u l t u r a l o r o t h e r production. Overproduction i n excess of t h i s resources p o t e n t i a l i s t h e r e f o r e p o s s i b l e , but r e l e v a n t feedback causes a temporal o r perm n e n t d e t e r i o r a t i o n i n t h e environmental q u a l i t y . Water p o t e n t i a l , which forms an i n t e g r a l p a r t of t h i s resources p o t e n t i a l , can be defined by t h e - annual discharge of t h e s u r f a c e water and by t h e t a b l e and q u a n t i t y of t h e groundwater , - annual r a i n f a l l and t h e discharge c o e f f i c i e n t s ,

- minimmi discharges arid t h e flow d u r a t i o n curve - water q u a l i t y r e l e v a n t t o q u a n t i t y records o r t o t h e depth below t h e s u r f a c e . O v e r - u t i l i z a t i o n of t h e water p o t e n t i a l causes f i r s t t h e d e c l i n e i n t h e water q u a l i t y , and t h e second d e c l i n e of t h e environment. During t h e development of water resources l o c a l resources a v a i l a b l e nearby a r e used f i r s t . The u t i l i z a t i o n of t h e s e l o c a l water resources i s , i n t h e next development s t a g e , o f t e n replaced by mass water supply from s u b s t a n t i a l resources of g e n e r a l l y lower q u a l i t y . The i n t e r c o n n e c t i o n of these mass water supply networks g r a d u a l l y c r e a t e s r e g i o n a l w a t e r supply s y s t e m . The p o s s i b i l i t i e s of f u r t h e r e x t e n s i v e development a r e exhausted by long-distance water conveyance and by t h e c r e a t i o n of a n i n t e r r e g i o n a l system. Respecting t h e l i m i t s of the n a t u r a l environment means a r a t i o n a l approach frcm t h e s t a g e of a non-systenlatic u t i l i z a t i o n of water resources, depending on t h e i r a v a i l a b i l i t y and economic f e a s i b i l i t y , t o t h e u l t i m a t e development s t a g e of t h e f u l l , r a t i o n a l and l a s t i n g u t i l i z a t i o n of water resources without any important long-term impact on t h e n a t u r a l e q u i l i b r i u n . Third p r i n c i p l e of water development s t r a t e g y : MAXIMIZATION OF THE REQUIRED OK P O S I T I V E EFFECTS f3F THE PROJECT AND MINIM I Z I N G I T S S I Z E A N D NEGATIVE IMPACT.

This p r i n c i p l e is derived n o t only from t h e need of economic f e a s i b i l i t y , but a l s o from t h e previous p r i n c i p l e of r e s p e c t i n g t h e environmental l i m i t s . Ey d e c r e a s i n g t h e s i z e o f t h e p r o j e c t , i t s n e g a t i v e impact may a l s o be reduced and

reserves l e f t f o r t h e d i v e r s e f u t u r e needs of t h e s o c i e t y .

351 nutriment

inte r r u Dted

fertilizers-

compensatory link

Fig. 5.4. An indisperisabie precondition f o r t h e e f f i c i e n c y of any water development measures i s t h e maintenance of the uninterrupted s t r u c t u r e s of t h e system: i n t e r r u p t e d s t r u c t u r e s have t o be replaced by new ones, e.g. f e r t i l i z ing e f f e c t of floods a f t e r completed flood control measures has t o be compensated by a r t i f i c i a l f e r t i l i z e r s , which i s energy- and labour-intensive.

5.4

TACTICS OF WATER WNAGEMENT Water requirements and water withdrawals usually exceed, or tend t o exceed,

the r a t i o n a l water requirements. I n a d d i t i o n t o t h i s , e f f l u e n t s and excessive

water consumption impair water q u a l i t y , r e s t r i c t i n g i t s f u r t h e r u t i l i z a t i o n . The need t o search f o r means of managing a water economy usually a r i s e s a s a r e s u l t of an a c t u a l o r expected d e t e r i o r a t i o n i n water resources caused by the p o l l u t i o n of t h e area i n question or of a whole country. An adequate u t i l i z a t i o n of water resources and a proper c o n t r o l of the use of water a r e impossible without an adequate u t i l i z a t i o n of a l l a v a i l a b l e means, which a r e b a s i c a l l y : 1

(a) (b)

legal i n s t i t u t i o n a l (and o r g a n i z a t i o n a l )

i

(c)

technical

t

(d)

economic

e

( e ) personal and moral P The l e g a l , i n s t i t u t i o n a l , o r g a n i z a t i o n a l , t e c h n i c a l , economic and personal arrangements and c r i t e r i a which a r e required t o provide e f f e c t i v e t o o l s f o r the r a t i o n a l and i n t e g r a t e d development, use and conservation of water resources a t

352 the n a t i o n a l l e v e l a r e riot veiy d i f f e r e n t from those required a t t h e l o c a l l e v e l . Water withdrawals W, water consumption C and water p o l l u t i o n N a r e a function of the indisperisable water requirements Ri and of t h e above v a r i a b l e s :

From a s o c i a l p o i n t of view, i t is indispensable t o safeguard f i r s t of a l l t h e r e l e v a n t personal water requirements of any individuum a s a b a s i c precondition of h i s l i v i n g standard. This b a s i c q u a n t i t y i s t o be offered t o the individuum i n t h e optimum q u a l i t y and a t a r a t e which does not s u b s t a n t i a l l y restrict h i s l i v i n g standard. Water requirements and uses i n i n d u s t r y , a g r i c u l t u r e , e n e r g e t i c s and t r a n s p o r t a r e t o be safeguarded under d i f f e r e n t economic conditions, because these bodies d i r e c t l y b e n e f i t from water u t i l i z a t i o n . On the o t h e r hand, it is indispensable t o use a l l t h e above tools f o r t h e

p r o t e c t i o n of human s o c i e t y before tinuseful wastage, misuse and depreciation of water resources and before overexcessive water withdrawals, demands and arrangements t h r e a t e n o r have a negative impact on t h e environment, thereby restricting the f u t u r e development o r negatively influencing t h e l i v i n g standard o r l i f e - s t y l e of t h e s o c i e t y concerned.

A dominant economic c h a r a c t e r i s t i c of water u t i l i t i e s is t h e l a r g e investment i n fixed c a p i t a l , characterized by the capital-turnover r a t i o , i . e . gross annual revenues divided by t o t a l investment, ranging from 0.15 - 0.25 comparing with 0 . 3 t o 0.5 f o r o t h e r u t i l i t i e s and 2 . 0 f o r manufacturing i n d u s t r i e s . A negative r e l a t i o n s h i p e x i s t s between water p r i c e and t h e wzter quantity demanded. An increase i n p r i c e is a s s o c i a t e d with a reduction i n t h e q u a n t i t y demanded. P r i c i n g p o l i c y , by a f f e c t i n g water requiremerits, i s t h e e f f e c t i v e t o o l which can, i n r e l a t i o n t o o t h e r t o o l s , s a t i s f y t h e varied goals of water mnagemen t . Domestic, i n d u s t r i a l , a g r i c u l t u r a l and i n f r a s t r u c t u r a l water requirements a r e responsive t o p r i c e changes. Concerning domestic water requirements, the change frcm f l a t r a t e s t o metered r a t e s may r e s u l t i n a permanent decrease of sane 30 t o 40% i n water use. A decrease exceeding 60% was recorded a s a res u l t of warm water supply metering and paying s e p a r a t e l y f o r each f l a t , being a r e s u l t of a l t e r i n g b a s i c uses, e.g. using stoppers, dishpans etc. instead of constant flaw, r e p a i r i n g leaks i n t h e domestic p l m b i n g system etc. When t h e r a t i o of water management c o s t s t o t h e t o t a l s o c i a l property is r e l a t i v e l y small, water development and management expenses can be f u l l y covered e i t h e r from p r i v a t e o r from comon funds. There is a g r e a t d i v e r s i t y i n the degree of i n s t i t u t i o n a l i n t e g r a t i o n i n water mnagement, but t h e growing c o s t s of water development and management r e s u l t i n increasing s t a t e and internationa l coordination and f i n a n c i a l i n t e r v e n t i o n , and i n a general tendency t o ensure

3 53 t h a t t h e u s e r s who d i r e c t l y b e n e f i t frcm such c o n t r o l cover t h e cost. TABLE 5.2 Product

[.hit

m3

Definition Water-withdrawn from a stream. (delivered t o the user)

1.

Surface (raw, irr i g a t ion ) water

2.

Groundwater

3.

Drinking water

m3 m3

4.

Process water

m3

5.

Waste water

m3

6.

Treated waste water

7.

Sliidge

t

U t i l i s a b l e waste from waste water treatment and p u r i f i c a t i o n p l a n t s i n c l . recovered m a t e r i a l .

8.

Hydropower

liwh

Energy (average coiitiniious , peak, breakdown) generated by c o n c e n t r a t i o n of head and by s t o r a g e , i f r e q u i r e d .

m3

Symbol

Water withdrawn from a n a q u i f e r .

\dater corresponding t o d r i n k i n g water q u a l i t y standards, delivered t o the water u s e r .

Treated water d e l i v e r e d t o t h e watei u s e r f o r i n d u s t r i a l use. Waste water taken away by t h e sewerage system t o t h e stream o r waste water t r c a tment p l a n t .

Waste water t r e a t e d i n t h e waste water treatment p l a n t .

C l a s s i f i c a t i o n of w a t e r management products This tendency r e s u l t s i n t h e formation of river boards and water supply/ disposa 1 a u t h o r i t i e s a s econcmic o r g a n i z a t i o n s safeguarding t h e r e q u i r e d prod u c t s , productive and unproductive s e r v i c e s (Tab. 5 . 2 , 5.3). Hence, t h e t a s k of economic management t o o l s i s as follows: (a)

they p a r t i a l l y o r f u l l y f i n a n c e t h e main a c t i v i t i e s of water mnagement

o r g a n i z a t i o n s , which r e g u l a t e water development a c t i v i t i e s , (b)

they r e g u l a t e water withdrawals, water consumption and t h e q u a n t i t y and

quality of e f f l u e n t , ( c ) they r e g i l a t e i n d u s t r i a l and a g r i c u l t u r a l development, municipal and r u r a l development, water power g e n e r a t i o n , i n l a n d n a v i g a t i o n , water r e c r e a t i o n , thus also i n f l u e n c i n g t h e l i v i n g standard of the population, which is a l s o d i r e c t l y a f f e c t e d by t h e i r impact on t h e dom(-.stic water requirements. The determination of charges f o r water withdrawals, water consumption, in-

stream water u s e , water p o l l u t i o n , e f f l u e n t d i s p o s a l , as w e l l as v a r i a t i o n s and exemptions i n t h e s e charges and r a t e s , and using water f o r any of t h e mentioned purposes without charges, i n f l u e n c e s t h e s o c i a l e f f i c i e n c y of water u t i l i z a t i o n . Rut the degree of such i n f l u e n c e depends on l o c a l , and e s p e c i a l l y economic con-

354 d i t i o n s . These charges and r a t e s influence t h e water requirements of t h e populat i o n i n connection with the l i v i n g standard and s t y l e , i . e . t h e n e t income, standard of dwelling and s o c i a l customs. The influence of water r a t e s on a g r i c u l t u r a l water requirements rrainly depends on the cost-benefit r a t i o , on expenses f o r o t h e r arrangements needed f o r an increase i n a g r i c u l t u r a l y i e l d , on t h e market and c r e d i t p o s s i b i l i t i e s , and

on the I n e r t i a of t r a d i t i o n a l i r r i g a t i o n and o t h e r a g r i c u l t u r a l p r a c t i c e s .

TABLE 5.3 Water management services

Unit

Definition

symb0 I

Productive s e r v i c e :

2

1. Flood c o n t r o l

km

2.

s o i l protection

km2

3.

Maviga t ion

tkm

4 . Aquatic l i f e management

m3 .s -1

3 s-l

5.

P o l l u t i o n control m

6.

Other productive services

.

rn3 .s-l

Water resources rnanagement aimed a t p r o t e c t i o n a g a i n s t floods and erosion. Drainage and s o i l p r o t e c t i o n . Improvemerit of wateiways , operation of locks and flow c o n t r o l . Water d e l i v e r y and water resources mnagemeri t t o increase e specia 1l y f i s h production. Management of water resources t o restrict water p o l l u t i o n . Management of water resources t o enable production i n o t h e r product i o n s e c t o r s , e.g. water d e l i v e r y f o r pump storage p l a n t s etc.

N1

N2 N3

N4 N5

N6

Unproductive services : ~~

7.

Recreation and water s p o r t s

8.

Hydrmeteorolog i c a l services

9.

Other unproduc-

capita Per season

Management of water courses t o enable o r improve recration.

N7

Collection and processing of hydrometeorological data.

N8

Categorization of water management services. The impact of w a t e r rates on i n d u s t r i a l water demands depends on t h e r a t i o of the water supply and e f f l u e n t d i s p o s a l c o s t t o the t o t a l c o s t of production, on t h e i r influence on t h e development of t h e r e l e v a n t i n d u s t r i a l p l a n t , on the water-saving technology a v a i l a b l e , on t h e i n e r t i a of t r a d i t i o n a l production p r a c t i c e s , and, l a s t but not l e a s t , on t h e i r influence on t h e n e t income of t h e r e l e v a n t milagers ,

355 P r a c t i c a l water p r i c i n g systems generally represent combinations of the following watei p r i c i n g p o s s i b i l i t i e s : (a) (b)

Free of charge, i . e . p r i c e of water included i n general t a x e s ,

(c)

\dater r a t e s

S p e c i f i c water t a x ,

- per u n i t of water -

per u n i t of product

($ per 1 . s - l ) ($ per 1000 pc, per kldh)

- per u n i t of s e r v i c e s (tb) - lump sum, without r e l a t i o n t o t h e q u a n t i t y of water supplied. Rates can take the following f o r m ( a ) uniform r a t e s , dependent on t h e quantity supplied i n t h e r e l e v a n t categ o r i e s of water u s e r s , (b)

r a t e s with increase f o r increased q u a n t i t i e s (supporting water s a v i r g )

(c)

r a t e s with reductions f o r increased q u a n t i t i e s (supporting t h e develop-

ment i n the r e l e v a n t category of water u s e r s ) (d) seasonal (depending on t h e balances of water resources and requirements and supporting water saving i n t h e period of i t s d e f i c i e n c y ) . !dater r a t e per u n i t can be (a)

uniform

f o r a l l water u s e r s ,

( b ) d i f f e r e n t i a t e d (dependent on t h e s t a t e social and development policy: b a s i c q u a n t i t y f r e e clf charge, lower p r i c e s f o r p r e f e r r e d water u s e r s , e.g. f o r a g r i c u l t u r e , higher f o r high-income producers etc. ) (c)

dependent on water q u a l i t y (surface water, groundwater, t r e a t e d water

e t c . , c l a s s Ia, I b , 11, 111, I V ) , (d) dependent on t h e q u a l i t y of t h e product ( i n energetics f o r kbJh b a s i c , peak, breakdown e t c . ) ( e ) dependent on water consumption ( i n industry and e n e r g e t i c s ) . I n t h e case of water r a t e s per u n i t of water consumption, these can be (a)

uniforni,

(b)

categorised on t h e b a s i s of t h e consumption r a t i o ,

( c ) with a n i n c r e a s e f o r increased water consumption and a decrease f o r decreased consumption), ( d ) seasonal (increased during unfavourable balance of water resources and needs ) . Rates per u n i t of e f f l u e n t can be

(a) uniform, (b) w i t h l i n e a r or exponential progressive increase f o r increased p o l l u t i o n , ( c ) categorized according t o the category of p o l l u t e r ( a g r i c u l t u r e , industry, m u n i c i p a l i t y ) , (d) categorized on t h e b a s i s of t h e water q u a n t i t y and q u a l i t y i n the recip i e n t , c l a s s I a , l b , T I , 111, I V ,

356 ( e ) categorized on t h e b a s i s of t h e e f f l u e n t q u a n t i t y and q u a l i t y . J-egal t o o l s can achieve similar s t i m u l a t i n g fiirictions t o those of economic t o o l s namely through:

(a) o f f i c i a l d u t i e s ( f o r u t i l i z a t i o n permissions, discharge p e r m i t s , r u l ings e t c . ) p1 ( b ) s a n c t i o n rates, assessments p2 ( c ) f i n m ( e . g . f o r u t i l i z a t i o n of water i n v i o l a t i o n of v a l i d r e g u l a t i o n s ) (d)

recompenses e t c .

p3 '4

Expenses connected w i t h water development and management include (a)

management and c o n t r o l c o s t s

01 ( b ) o p e r a t i o n a l c o s t s f o r water withdrawal, d i s t r i b u t i o n , p u r i f i c a t i o n , waste water d i s p o s a l e t c . 02 ( c ) maintenance and reproduction c o s t s of water development p r o j e c t s (depreciation costs e t c . ) (d)

investment c o s t s

O3

O4

The balance of r e l e v a n t b e n e f i t s and expenses can be expressed by a simple equation

S

- s u r p l u s r e q u i r e d ( i f riecessary)

k - g r a n t s from o t h e r s e c t o r s and bodies

G

0

k

- expenses

ilk - accumulated charges f o r products connected with t h e water u s e

Nk

-

accuniulated charges f o r s e r v i c e s connected w i t h t h e water use

Pk - d u t i e s , f i n e s , recomperises e t c . ( i f incorporated i n economic t o o l s ) . The economic b a s i s f o r water resources development and management has t o be e s t a b l i s h e d by i n c l u d i n g o r excluding t h e above mentioned components i n t h e equation. Hence, t h i s i n c l u s i o n o r e x c l u s i o n and t h e l e v e l of t h e r e l e v a n t charges n o t only decide on t h e c r e a t i o n of f i n a n c i a l r e s e r v e s , on a timely a c q u i s i t i o n of t h e necessary means f o r o p e r a t i o n , maintenance, investment, adm i n i s t r a t i v e and o t h e r c o s t s , but a l s o on t h e u t i l i z a t i o n of water resources i n

a s o c i a l l y d e s i r a b l e manner, on t h e c o o r d i n a t i o n of t h e development r a t e , and, l a s t b u t n o t least, on t h e development of l i v i n g s t a n d a r d s . Bearing t h i s i n mirid, water rates should be determined on t h e b a s i s of t h e f o l lowi.ng f a c t o r s : (a)

reimbursement of expetises f o r :

357

-

operation,

-

administration,

-

investment f o r f u r t h e r development,

reproduction and modernization,

TAEU 5.4 Basic a i m i n

Factor water supply

waste water disposal

Reimbursement o r p a r t i a l reimbursement of emenses f o r : 1. F i n a n c i a l balance

a ) management and c o n t r o l

a ) maiiqyment and control

b ) operation and maintenance of water supply networks and f a c i l i t i e s

b) operation and maintenance of sewerage systems

c ) t h e i r modernization

c ) t h e i r modernization d) new waste water disposal proiects

d) new water supply p r o j e c t s

2. Factors of time

a ) seasonal l i m i t a t i o n s of availability b ) seasonal and d a i l y limitat i o n of requirements c ) long term l i m i t a t i o n of water needs due t o limited resources

3. Factors of c o n s u q t i o ? and concentration

4 . Factors of quality

5. Policy

a ) r e s t r i c t i o n of environmental p o l l u t i o n b ) seasonal and d a i l y cont r o l of waste water d i s posal c ) l i m i t a t i o n of l a s t i n g p o l l u t i o n due to r e s o u r ces p o t e n t i a l

a ) l i m i t a t i o n of concentrat i o n of t o x i c and o t h e r substances i n waste waters b) l i m i t a t i o n of water consum- b ) r e s t r i c t i o n of change i n p t i o n i n t h e long term ecosys term a ) l i m i t a t i o n of a c t u a l water consumption

decrease i n w a t e r r e q u i r e ments i n t h e production sphere

a ) decrease i n water pollut ion b) m a t e r i a l recovery

E f f e c t of water and waste water d i s p o s a l p r i c i n g on general ecoiponiic development and on the l i v i n g s tandard of population, e s p e c i a l l y on l w i n c c m e groups. E f f e c t of p b n a l t i e s and s u b s i d i e s on water use from e n v i r o p i e n t a l l y , r e g i o n a l l y and s o c i a l l y d e s i r a b l e viewpoint.

Categorization of t h e b a s i c f a c t o r s of water and waste water disposal p r i c i n g policy. (b) (c)

p a s s i v i t y of t h e balance of water resources and needs, l i m i t a t i o n of water consumption,

358 r e s t r i c t i o n of water resources pollution,

(d) (e)

overall development goals

The influence of economic tools on water withdrawals Id, water consumption C and water pollution N (BOD .nid3) 5 i n t h i s way W

C

5

N

9

can be expressed by a simplified equation 5.1

(m3.s-l, BOD5.

fl-3(%)-

=

(5.6)

An increase i n water r a t e s r e s u l t s i n a decrease i n water withdrawals, i n a decrease i n e f f l u e n t quantity and i n a decrease i n water consmption.

An exponential increase i n r a t e s f o r water pollution r e s u l t s i n a d r a s t i c

decrease i n water pollution

The a t t r i b u t e s of efficiency a r e associated with competitive prices. Theref o r e , the r a t e s should be varied with the required changes i n denland, consumpt i o n , water pollution and cost conditions. Water consmption can be influenced, i . e . decreased, by the introduction of special r a t e s or by associating water r a t e s with the value of the water consumption r a t i o 'MC>

'?Ic>

0

c1 < c2 < c3

(5.9)

Applying the forces of supply and demand, water withdrawals W can be expressed, according t o Hanlce and Davis (1971), a s a reversed and exponential funct i o n of p r i c e (5.10)

M

-

e K

- price e l a s t i c i c y or water withdrawals - constant, expressing t h e combined e f f e c t of other tools

unit r a t e

K = f ( l , i , t , e , p ) , and can be simply derived f r m indispensable water require-

ments Ri

K

=

k; 1

. Ri

(see paragraph 3.2)

(5.11)

359 I f price is t o be changed from 'M t o 2FI, the expected water withdrawal W2 can be estimated by taking the log transform

LO^ w1

=

Log K - e l ~ M 'g

Log W2

=

Lcg K

-

e log 2M

(5.12)

as well as by subtracting and rearranging t o find the water withdrawal W2 from the known values of the other variables: ~ o w2 g

=

e

.

(log 'M - log 2M) + log

w1

I n the water resources u t i l i z a t i o n secr-or of the econony prices a r e generally not determined by objective factors of supply and demand, but s e t by the pricing policies of u t i l i t y mnagers. They r a i n constant from the season of peak a v a i l a b i l i t y t o t h e season of peak demand. Available resources a r e used ine f f i c i e n t l y and inequities a r e imposed on the u t i l i t y ' s consumers. The season of peak water demands frequently occurs i n the period of low water a v a i l a b i l i t y . Water withdrawals i n the season of peak water dernand o r i n the period of low water a v a i l a b i l i t y a r e economically d i f f e r e n t fran those i n other periods: This water is high-cost water, because additional capacity must be provided i f requirements exceed the original capacity. By not varying water r a t e s t o r e f l e c t these cost differences, investments a r e larger than econanically j u s t i f i e d . The e l a s t i c i t y of water requirements and t h e i r s e n s i t i v i t y t o changes i n water r a t e s w r y according t o the d i f f e r e n t categories of water users. But i n any case the seasonal regulation of water r a t e s decreases the difference between the maximurn and ninimurn values of t o t a l withdrawais

(5.14) provided t h a t

Nf

and W correspond t o seasonal and constant prices respectively

which reimburse the same t o t a l amount. The application of seasonal water r a t e s f o r a hypothetical u t i l i t y can be i l l u s t r a t e d by two curves: mmin - curve representing off-peak water requirements (fcr the period of an e f f e c t i v e balance of u a t e r resources arid needs)

mmay. - curve representing peak water requirements ( f o r the period of a passive balance of water resources and needs) (Fig. 5.5). The constent average cost pricing l i n e is horizontal and implies that capac i t y stands a t some constant r a t i o t o peak water requirements. The average variable costs a r e assumed t o be constant and equal t o marginal costs. The in-

360

M water rates

3-

-3

m

S

M eonst

5

rn

P

I

Fig. 5.5. The e f f e c t of an increase i n water prices i n the season of increased water requirements and drop i n water a v a i l a b i l i t y and its off-seasonal decrease, safeguarding the same p r o f i t but increased efficiency i n water use according t o Hanke and Davis (1971). cremental costs of expansion a r e depicted by a proxy, average variable costs plus recorded capacity costs distributed over s i x months. Constant average prices r e s u l t i n inefficiencies during the period of peak The use of water requirements, demanding the needlessly excessive capacity W P' water i n the period of excess a v a i l a b i l i t y i s needlessly limited, leading t o withdrawals Wm. Seasonal prices produce higher off-peak requirements l d i and lower water re+ quiranents W during the period of lack of water. Water use i n the off-peak P season should be allowed u n t i l the relevant incremental costs a r e equated t o incremental value. By allowing t h i s expansion i n off-peak use there would be an efficiency gain, represented by the t r i a n g l e 123 (Fig. 5.5). I n the case of m x i m withdrawals during constant prices W the loss generated by the needP' lessly excessive capacity pricing r u l e is postulated f o r future years, s i g n i f i cant reductions i n water requirements can be expected, resulting i n investment savings. To relieve the problem of peak requirements occurring i n the period of low water a v a i l a b i l i t y and safeguard a dynamic water development (a) the water r a t e s should r e f e r t o the actual cost structure and actual cost of resources used o r saved by consumer decisions, (b) the water r a t e s should r e f l e c t operating costs with no, o r only a part i a l contribution t o capacity costs, i f the capacity of the available resources i s not adequately u t i l i z e d ( i . e . i n the period of a highly a c t i v e balance of water resources and needs), (c) the period of an equilibrium of water resources and needs, o r i f requirements exceed capacity a t the relevant price, the price should r e f l e c t both

361 operation and capacity c o s t s and should be adjusted upward t o r e s t r a i n water withdrawals t o t h e capacity l e v e l , and seasonal r a t e s should be determined t o r e s t r i c t t h e f l u c t u a t i o n of water withdrawals during peak and off-peak periods of demand. A s i m i l a r policy should be accepted to decrease water p o l l u t i o n by industry. NON-CONVENTIONAL TECFNIQIJES OF WATER IJSAGE

5.5

The programne i n keeping with t h e f i n a l phase of water development, when a l l s u r f a c e and groundwater resources a r e f u l l v u t i l i z e d i n the conventional way, includes

-

the general extension of w a t e r s a v i n g technologies, including non-convention-

a 1 water u t i l i z a t i o n and - using non-conventional water resources o r non-conventional techniques of water supply, i . e . (a) water, (b)

long-distance water conveyance and long-distance t r a n s p o r t a t i o n of conjunctive u t i l i z a t i o n of surface and groundwater resources,

( c ) groundwater mining and a r t i f i c i a l recharge, ( d ) watershed management aimed a t modifying t h e q u a n t i t y and timing of water production, ( e ) changes of t o t a l r u n o f f , namely changes of evaporation o r evapotranspir a t i o n r a t e , changes of snow and i c e melting,

(f) (g)

weather modification, d e s a l i n a t i o n , renovation of waste water, treatment of o t h e r l o r q u a l i t y

water .

5.5.1

Long-Distance

Water Conveyance and Long-Distance Transportation of Water

The problem of the long-distance conveyance and t r a n s p o r t a t i o n of water is b a s i c a l l y economic. During t h e conventional water supply t h e c o s t s f o r water withdrawals and treatment p r e v a i l :

Mw

+

Mt

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