CHARACTERISTICS AND
POLLUTION PROBLEMS
OF
IRRIGATION RETURN FLOW
U. S. DEPARTMENT OF THE INTERIOR
FEDERAL WATER POLLUTION CONTROL ADMINISTRATION
ROBERT S. KERR WATER RESEARCH CENTER
ADA, OKLAHOMA
MAY 1969
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CHARACTERISTICS AND POLLUTION PROBLEMS
OF
IRRIGATION RETURN FLOW
Prepared by
UTAH STATE UNIVERSITY FOUNDATION
The research upon which the publication is based
was performed pursuant to Contract No. 14-12-408,
with the Federal Water Pollution Control Administration,
U. S. Department of the Interior.
Copies of this report are available at the
Robert S. Kerr Water Research Center
P. 0. Box 1198, Ada, Oklahoma 74820
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This report has been reviewed in the Federal
Water Pollution Control Administration and approved
for publication. Approval does not signify that the
contents necessarily reflect the views and policies
of the Federal Water Pollution Control Administration.
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VI1
ACKNOWLEDGMENT
This study of the "Characteristics and Pollution Problems of
Irrigation Return Flow" was made by staff members of Utah State
University, Logan, Utah, under a Utah State University Foundation
contract with the Federal Water Pollution Control Administration
(Contract No. 14-12-408). The study was under the leadership of
A. Alvin Bishop and Howard B. Peterson of the Department of Agri-
cultural and Irrigation Engineering, who organized the report and
supervised the technical editing.
The following staff members contributed to the report: Jay M.
Bagley, Director, Utah Water Research Laboratory; J. E. Christiansen,
Professor of Irrigation Engineering; David Hendricks, Professor of
Sanitary Engineering; C. Earl Israelsen, Research Engineer, Utah
Water Research Laboratory; Norman B. Jones, Professor of Sanitary
Engineering; Jerome J. Jurinak, Professor of Soils, John Neuhold,
Director, Ecology Center; Clyde E. Stewart, Professor of Agricultural
Economics; and D. W. Thorne, Vice President for Research. Special
credit is due to Dr. Dean F. Peterson, Dean of the College of
Engineering, who, although receiving no compensation from the pro-
ject, helped in its initial organization and gave suggestions con-
cerning the outline and scope as well as contributing to the body
of the report.
The report was prepared in close cooperation with Dr. James
P. Law, Jr., Project Officer and Research Soil Scientist, Robert S.
Kerr Water Research Center, Federal Water Pollution Control
Administration, Ada, Oklahoma. His assistance is gratefully
acknowledged.
In preparation of the report, extensive use has been made of
pertinent literature, and a conscientious effort has been made to
cite all source material.
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IX
TABLE OF CONTENTS
Page
TABLE OF CONTENTS ix
LIST OF FIGURES xvii
LIST OF TABLES xix
SUMMARY GENERALIZATIONS xxiii
INTRODUCTION 1
Development of Irrigation in the United States ... 1
Economic Importance of Irrigation 2
Importance and Mechanics of Return Flow .... 4
Nature and Extent of the Pollution Problem of
Irrigation Return Flows 7
Relation of Irrigation Return Flow Problems to Present
Legislative Water Quality Standards and General
Pollution Control Problems ....... 9
Special Problems Due to Consumptive Use .... 10
IRRIGATION PRACTICE 13
Mechanics of Irrigation Practice 13
Application methods 13
Soil moisture storage 14
Evapotranspiration 15
Salt Balance Concept 15
Concentration of salts 16
Leaching 16
Ion exchange 17
Chemical fixation and precipitation 18
Nutrients 19
Pesticides 20
Consequences to Irrigation Return Flow 21
Soil moisture regime 23
Drainage water 24
Drainage water from surface sources ... 24
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X
Page
Drainage water which has moved through
the soil profile 24
Impact of Poor Water Quality on the Irrigation
Farmer 25
Principal Effect of Salinity 26
Distribution and concentration of salts in the
root zone 27
Adequacy of drainage 27
Quality of irrigation water 28
The amount and frequency of water applied . .29
Irrigation method 29
Effect on seed germination 30
Other farm management practices to offset effects
of salinity 30
THE QUALITY PROBLEM 33
Scope and Magnitude 33
Acreage affected by salinity .33
Areas adversely affected by return flow . . . .35
Salt balance and quantities of salt involved . . 36
San Joaquin Valley drainage and salt balance
problems 37
Irrigation water and return flow in the Yakima
Valley, Washington 40
Salt balance and return flow to groundwater basin . 42
Water Quality Requirements for Crops 43
Plant response 44
Osmotic effects 44
Phytotoxic substances 44
Nutritional imbalance 45
Soil physical properties 45
Presently accepted criteria for irrigation . . . .46
Proposed changes in criteria 50
Nature of Pollutants Involved 50
Salinity, hardness, and plant nutrients 50
Phytotoxic elements 53
Pesticides 56
Sediments and turbidity 56
Organic matter, taste, odor, and color .... 57
Thermal pollution by irrigation 57
SOURCES AND DETECTION OF POLLUTANTS 60
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XI
Page
Sources of Pollutants in Irrigation Water and
Return Flow 60
Soil derived 60
Concentration by evapotranspiration 64
Fertilizers and amendments 64
Pesticides 67
Municipal and industrial supplies 69
Nature and extent of practice of using
waste waters 69
Characteristics of municipal waste waters • • 73
Characteristics of industrial waste waters • • 75
Fate of municipally and industrially derived
pollution 75
Irrigation supplies from used water .... 82
Testing and Monitoring 82
History of water quality monitoring in western
United States 82
Beginning of systematic effort for a
national picture 83
Water quality for reclamation 83
Data retrieval, initial efforts 83
First permanent monitoring network ... 84
Establishment of a permanent national
network 84
Permanent network established for irrigation
return flows 84
Pollution-oriented national water quality
network 85
Project-oriented data collection activities • • 86
Groundwater 86
Data retrieval 86
Continuous instrumental monitoring .... 88
Remote sensing 89
EFFECTS OF POLLUTANTS IN IRRIGATION RETURN
FLOWS ON OTHER BENEFICIAL USES 91
Quality Requirements for Municipal Water Supplies • . 92
Quantitative limits 92
Nature of limits 92
Physical quality 92
Chemical quality 94
Bacterial quality 94
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Xll
Page
Summary of Effects of Potential Pollutants in
Irrigation Return Flows on Municipal Water
Supplies 94
Quality factors 94
General discussion 98
Quality Requirements for Industrial Water
Supplies 99
Effects of Potential Pollutants in Irrigation Return
Flows on Industrial Water Quality Require-
ments 102
Effects of Return Flow on Fish and Wildlife ... 103
Chemical effects 104
Pesticide effects . 105
Osmotic effects 107
Sediment effects 108
Temperature 108
Interaction effects 109
Water Quality Requirements for Aquatic Life . . . 110
Water Quality Requirements for Farmstead and
Lifestock Ill
Quality for livestock Ill
Quality Requirements for Recreational and Aesthetic
Uses of Water 114
Effects of potential pollutants in irrigation return
flows on recreational and aesthetic use . 115
MAXIMUM USE AND QUALITY MANAGEMENT OF
IRRIGATION WATER 119
Maximum Use of Water for Irrigation 119
Quality Management 122
Natural dilution 123
Limitations in the effectiveness of dilution . 123
Streamflow regulation for water quality control . 123
General water quality considerations related to
the storage and release of waters from
reservoirs 124
Legal development of streamflow regulation
for water quality control 124
Problems of interpretation of the 1961
legislation 125
Present status of streamflow regulation for
quality control 127
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Xlll
Page
Evaluation of the feasibility of the streamflow
regulation for water quality control of
irrigation return flow 129
Return Flow Control 130
Canal lining to prevent seepage 130
Bypassing downstream diversions 131
San Luis or San Joaquin master drain . . .131
Wellton-Mohawk drainage solution .... 131
Evaporation '. 132
Mineralized springs 133
Control of leaching 134
Desalinization and Contaminant Removal 135
Treatment for pollution control in San Joaquin
Valley 135
Treatment for water supply 136
Pesticide removal 136
Nutrient removal technology 137
Removal of minerals 139
Energy requirements 141
Sources of energy 141
Dual plants 141
Cost of desalted water 143
Conventional water 146
ECONOMIC ASPECTS 153
Economic Considerations 153
Analytical techniques 154
Economic projections 155
Agricultural Income Impacts 156
Production and damage functions 156
Farm incomes 156
Profitable farm adjustments 157
Other Impacts 157
Local and regional economies 157
Alternative Courses of Action 158
"Optimum" levels of water quality 159
Institutions 160
Selected Research and Literature on the Economics
of Irrigation Return Flow and Water Quality . • 160
Research in process 162
LEGAL ASPECTS 165
Legal Framework for Irrigation Water Use .... 165
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XIV
Page
Legal and hydrologic compatibility 165
Water rights doctrine 167
Riparian and appropriation doctrines .... 167
State water right structure and administration . 169
Interstate compacts 169
Federal Views on Water Rights 171
General Rules of Law Relating to Waste, Seepage
and Return Waters 173
Owners' rights on lands of origin 174
Continuance of supply 174
Recapture 174
Discharge of waste waters 174
Users' rights to waste and seepage water . . . 174
Return water 175
Appropriability 175
Return water within the watershed 175
Return flow from foreign water 175
Rights of those who import foreign water . . . 176
Discharge into natural channel 177
Legal Recognition of Water Quality Criteria . . . 177
State water quality management 178
Legal Conflicts Between Irrigation Water Rights
and Water Quality Standards 179
RESEARCH NEEDS AND RECOMMENDATIONS 183
Quantity of Return Flow 183
Recommendations 184
Quality of Return Flow 184
Recommendations 185
Leaching and Salt Balance 185
Recommendations 186
Precipitation and Exchange Reactions 186
Recommendations 187
Translating to the Field 188
Recommendations 188
Organic Wastes 189
Recommendations 189
Thermal Pollution 189
Recommendations 190
Matching Use to Quality 190
Recommendations 191
Treatment and Management of Return Flow Waters . 192
Recommendations 192
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XV
Page
Ground-water 193
Recommendations 193
Public Health . 194
Recommendations 194
Legal and Economic Considerations 195
Recommendations 195
GLOSSARY OF TERMS 197
REFERENCES 203
BIBLIOGRAPHY 223
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XV11
LIST OF FIGURES
Figure Page
1. Irrigated land in farms in the United States ... 3
2. Model of the irrigation return flow system .... 5
3. Approximate relationship of salt production to water
production for several rivers in the western United
States 8
4. Prevalent types of salts in river waters (drawn from
USGS Atlas HA-61) 52
5. Major drainage regions, industrial definitions . . 72
6. Summary of standards for use of reclaimed waste
water 74
7. Typical fuel energy required by various desalting
processes to produce 1, 000 gallons of fresh water
(in kilowatt-hours) 142
8. Projection of sea water desalting costs for a range
of plant sizes 145
9. Desalting product water costs versus year .... 145
10. Cost of conventional water versus water from
desalinization plants 147
11. Cost of fresh water -- conventional and converted . 148
12. Exemplary costs of conventional supply at Pierre,
South Dakota 151
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XIX
LIST OF TABLES
Table Page
1. Status and extent of saline and sodic areas in the
seventeen western states and Hawaii I960 .... 34
2. Drainage and salt balance in the Imperial Irrigation
District 37
3. Salt balance constituents, 1966 38
4. Comparative concentration and irrigation and drainage
waters, Imperial Irrigation District, 1966 .... 38
5. Comparison of irrigation •water and drainage •water,
6.
7.
8.
9.
10.
11.
Yakima Valley, Washington
Salt balance, Yakima Valley
Suggested guidelines for salinity in irrigation water
Trace element tolerances for irrigation waters
Levels of herbicides in irrigation water at which crop
injury has been observed
Levels of herbicides in irrigation waters ....
Chemical analyses of important streams from which
41
42
46
47
48
49
water is diverted for irrigation 51
12. Relative tolerance of plants to boron in the irrigation
water 54
13. Potential pollutants with indication of degree of toxicity
and mode of action 55
14. Incremental salt concentration attributable to specific
sources, Colorado River at Hoover Dam .... 60
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XX
Table Page
15. Acres of irrigated and tiled land, and inputs and
outputs of water and salt for irrigated land by years,
1957-1965, Coachella Valley, California 61
16. Comparison of the composition of Colorado River water
with that of drainage water 62
17. Rates of runoff and solute erosion for the period 1952-
1957 (except as noted) 65
18. Plant nutrients applied in 1965 66
19. United States: Estimated water use, 1900-1975
(Billions of gallons; daily average) 70
20. Regional incidence of industrial waste discharge, by
major industrial sectors, 1964 71
21. Average increments added by community use of
water 76
22. Summary of mineral increments in domestic waste
water for 15 California communities 77
23. Sources and amounts of salt pickup in two sewage
systems 77
24. Comparison of tap water and sewage effluent ... 78
25. Some significant chemical in industrial waste waters - 79
26. Summary of industrial waste: Its origin, character,
and treatment 80
27. Probable fate of municipal and industrial pollutants
after irrigation 81
28. Surface water criteria for public water supplies . . 93
29. Chemical standards of drinking water 95
30. Threshold odor concentrations of pesticides and sol-
vents in water 98
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XXI
Table Page
31. Preferred limits for several criteria of water for
use in industrial processes 100
32. Summary of specific quality characteristics of raw
waters that have been used as sources for industrial
water supplies 101
33. Guides to the quality of water for livestock . . . .113
34. Tentative guides for evaluating recreational waters . . 116
35. Summary of national technical advisory committee
report on water quality criteria for recreation and
aesthetics 118
36. Processes used for the removal of nitrogen and
phosphorus 138
37. Distribution of desalting plants by type of process . . 140
38. Typical rates for water in western United States . . . 149
39. Illustrative annual costs of impoundment 150
40. Costs of water conveyance by pipeline 150
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XX111
SUMMARY GENERALIZATIONS
This report represents an extensive review of the present state
of scientific knowledge and technology regarding water pollution prob-
lems associated with the practice of irrigation and occurring in irriga-
tion return flow. A large volume of literature was reviewed. Much of
the information relating to return flow was found in obscure publications
and reports not included in abstract journals or other-wise readily avail-
able. Most of the information contained in this literature was only in-
directly related to return flow. Examples of such information include
that on the persistence of pesticides in soils and their transport in
water, the adverse effects of plant nutrients in water, and the disposal
of sewage effluent by irrigation. There was evidence of considerable
current research being conducted on pollution problems of the Colorado
River Basin, in the San Joaquin Valley of California, and in the Columbia
River Basin. Most of the data and conclusions are for the western United
States, where most of the irrigated acreage is located and where the
number and magnitude of the problems associated with irrigation return
flow are concentrated. Most of the information can, however, be applied
to specific situations in the more humid sections.
Irrigation return flow is water diverted for irrigation purposes
that finds its way back into a supply. It includes bypass water, seepage,
deep percolation and tailwater runoff. Through irrigation return flow
salts are concentrated by evapotranspiration, and other substances, are
conveyed from irrigated lands to the common stream or to the ground-
water supply. Return flow from irrigated land may be augmented and
polluted from sources not concerned with irrigation, such as rainfall,
groundwater seepage, runoff from urban and industrial sites, highways,
non-agricultural lands, and discharges from municipal and industrial
sources.
The acreage irrigated and the water consumed are indicative of
the magnitude of the return flow problem. In 1965 there were 110. 8 bgd
diverted to serve 42 million acres. Of this an estimated 64. 7 bgd were
consumed. The pollution aspect of irrigation return flow deals with the
ineviaBtble concentration of soluble salts caused by the consumption of
water. The major problems associated with the quality of return flow
are primarily in the arid portions of the western states where users
compete for the supply. Of the irrigated acreage within the conterminous
United States, about 80 percent falls within the area in which the water
demands exceed or will exceed the supply by 1980. This report deals
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XXIV
with the complicated problems related to the quality of return water
and the effect on water used for irrigation and other purposes.
Many water quality changes and combinations of changes take
place during irrigation. These changes are influenced by: (a) bio-
chemical action such as fixation of nitrogen, mineralization of organic
matter, reduction of nitrate and biodegradation, (b) erosion, (c) evap-
oration and transpiration, (d) filtration, (e) heat transfer, (f) ion ex-
change, (g) leaching, (h) precipitation, and (e) sorption and chelation.
Not all of the effects are harmful. Although salts are being concentrated,
other pollutants may be removed. Nutrients and organic wastes depos-
ited on the land may be used by the crops, fixed by the soil, or degraded
so they are not combined in the return flow. Residual salts often become
a part of the return flow.
Irrigation drainage water which has moved through the soil has
quality characteristics different from the surface runoff. The following
changes can be expected in drainage water passing through the soil:
1. Greater concentration of dissolved solids than in
the applied water.
2. Different proportion of the various ions, with a
likely increase in the proportion of sodium and
chloride.
3. Total salt load increased or decreased, depending
on the amount of leaching.
4. Little or no colloidal or sediment material.
5. More or less nitrate content than in the applied
water, depending on the original content of the
water and the fertility of the soil. The most likely
situation for an increase is when an abundance of
fertilizer is applied to a high value crop grown on
an open or sandy soil and lavishly irrigated. Seasonal
variation is usual.
6. A decrease in phosphorus if the content in the applied
water was high, and an increase if low.
7. A reduction in all degradable pesticides and deter-
gents is most likely.
8. A decrease in the oxidizable organics, pathogenic
organisms and coliform bacteria.
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XXV
9. Chlorinated hydrocarbons do not move through the
soil in appreciable concentrations and into drainage
effluent. If appreciable concentrations are present
in the irrigation water they will be largely removed
by the soil.
10. When sewage effluent is used for irrigation it is
probable that there will be a reduction in the con-
centration of all pollutants except the common
soluble salts.
The following changes can be expected in surface runoff from
irrigated land:
1. Highly variable in amount and composition for any
given area.
2. Total dissolved salts only slightly greater than in
the applied water. Can be less when diluted by
rain or mixed with other runoff water.
3. Phosphorus and persistent pesticides are sorbed
and are likely to .move with soil particles and,
therefore, their pollution presence in surface water
is correlated with the amount of erosion.
4. Colloidal content and sediment load can be more or
less than the applied water, but greater than in sub-
surface flow.
5. Surface water is subject to receiving pollutants
directly during application from accidental dis-
charge, from cleaning equipment, and from water
to which pesticides and fertilizers are being applied.
6. Urban and rural runoff becomes commingled with
irrigation return flow. These waters may carry such
pollutants as plant nutrients, pesticides, and animal
wastes.
7. Sporadic use of fertilizers and pesticides accounts
for considerable variation in the composition of sur-
face return flow.
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xxvi
Only a limited amount of data is available on the nutrient content
of return flow water and on the effects of kinds of fertilizers and methods
of application. The effects of slow release fertilizers on pollution reduc-
tion has not been determined. Some confusion exists as to the basis of
reporting the nitrate and phosphate. In some instances, nitrate is re-
ported as nitrogen and in others as nitrate. For phosphorus it is not
always clear as to whether the data is in terms of P, PO,, or P O .
Little or no data are reported where phosphate concentrations are less
than one mg/1.
Sprinkler application, pump back, reuse of tail waters, etc. ,
results in greater application efficiency. As the efficiency is increased,
an increase in the salt concentration of the return flow can be expected.
An improvement in conveyance efficiency should result in less seepage
loss and leaching from non-irrigated soils, with a Somewhat offsetting
reduction in salinity.
Salt balance evaluation of a given area or basin is of limited value.
If the outflow of salt is less than the inflow, then salts are accumulating.
If the outflow is greater there is still no assurance that salt is not ac-
cumulating in some of the irrigated land and being leached by seepage,
etc. from non-irrigated portions of the basin. It is also possible to
have salt accumulating in a portion of the soils and being leached from
others with an overall balance. Applying the salt balance concept to
other pollutants is meaningless because of the many interactions and
reactions by the pollutants within the soils and the conveyance water.
There appears to be only a limited basis for the often quoted
conclusion that salt concentrations in return flows are from five to 10
times higher than in the original water. In several controlled studies
the range was 2. 5 to 5. More cases would probably fall within the range
of two to seven. The concentration varies greatly with time and space.
Even after careful study it is difficult to predict the composition of the
drainage water for a given area; e. g. , the variation in estimates of the
salt content of the San Luis drain and the change of concentration with
time.
Data in the review indicate that salt concentration in the drainage
water for a given area, when irrigated and adequately drained, decreases
with time. This decrease should continue to an equilibrium. The con-
centration at equilibrium should be approximately equal to the mass of
salt in the irrigation water, plus the mass of salt being released by
contemporary weathering of the soil, divided by the quantity of drainage
water. Thus, the concentration increase should be only slightly greater
than the volume decrease. Deviation from such a concentration is de-
pendent on the amount of residual salt being removed from the irrigated
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XXVll
soils and the amount coming froin the non-irrigated areas. The only
fundamental management change to reduce the salt load and concentra-
tion without additional water or desalting would be to reduce the salt
contribution from the non-irrigated areas and/or eliminate the irrigated
acreage having a high residual salt content.
Changes in use patterns such as the current decrease in the use
of chlorinated hydrocarbon pesticides and a tendency to more carefully
follow application instructions alter the pesticide pollution problems,
new materials and methods of pest control will require continuing re-
search to regulate the impact on the quality of return flow.
There is little information on which to base conclusions as to the
effect of irrigation on the temperature of return flow water, except
that there seems to be a moderating effect. Through water storage
there is an opportunity to regulate temperature of release water by
drawing water from different levels of the impoundment.
Impoundment of water in multipurpose reservoirs has numerous
effects on the quality of water, both beneficial and detrimental. Among
the beneficial effects are decreases in coliform bacteria, color, turbid-
ity, suspended matter, BOD, and a leveling effect on temperature and
chemical quality. The adverse effects usually include a decrease in
oxygen and increases in alkalinity, iron, manganese, algae, and total
salinity. Often there is precipitation of calcium carbonate, resulting
in an increase in the proportion of sodium ions in solution.
Studies have been made on the feasibility of treating and disposing
of return flow water having salt concentrations too great for further use.
Desalting for irrigation does not appear to be an economical solution
except under unusual circumstances and then only where dual purpose
plants are used. Bypass drains are used in the San Joaquin Valley of
California, where the nitrate is removed before discharge, and for the
Wellton-Mohawk project in Arizona.
Pollutants in return flow water can have adverse effects on other
water uses and on re-use for irrigation. Likewise, pollutants from
other sources may have adverse effects on irrigation agriculture. This
is particularly true of the boron discharged by municipalities and
industry. In general, the more numerous the pollutants and the greater
the concentration, the less the value of an increment of water for irri-
gation or for any other use.
The unique and extremely difficult economic problems related to
irrigation return flows involve external economies and diseconomies.
The market and price system does not function well in resolving these
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XXV111
problems. Apparently special institutional and organizational arrange-
ments must be devised. Basic to these programs are appraisals of
economic impacts of various alternatives. These appraisals involve
complex conceptual considerations and difficult empirical relations.
Critical methodology and data needs are apparent.
A substantial conceptual economic framework related to this
problem has been developed. Some experimental work on basic
physical relationships is available and in process. However, prac-
tically no empirical study has been made of the economics of irriga-
tion return flows. Increased attention is being given to research
projects of a related nature. A need exists for economic research
explicitly concerned with the subject.
From the legal standpoint, irrigation return flows have been
regarded as part of the water resource and laws have been on the
statute books for over half a century outlining how rights to these
waters can be obtained. Statutes and court decisions have been con-
cerned with the quantity of return flow and the laws have been virtually
silent on the quality aspects of the return flow problem. National con-
cern over water pollution has led to state and national legislation con-
cerning quality standards which are becoming the concern of all irri-
gation projects.
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INTRODUCTION
The nation's growing determination to control or abate pollu-
tion, culminating in the Water Pollution Control Act of 1965 which
provided for state water quality standards, has raised many ques-
tions about the nature and extent of water quality changes resulting
from irrigation. This is a complex subject. It has economic,
political, legal, and philosophical implications, as well as physical
and technological ones. For more than a century irrigation has been
utilized in developing the land and water resources of the West.
Recently irrigation to supplement rain and alleviate drought has been
initiated throughout the usually humid East.
In irrigation, pure water is extracted by the plants from the
water supply, resulting in an inevitable concentration of those dis-
solved solids which are characteristic of all natural water supplies.
Other uses add something to the water, but irrigation basically takes
some of the water away, concentrating the residual salts. Irrigation
may also add substances by leaching natural salts or other materials
from the soil or washing them from the surface.
Irrigation return flow is a process by which the concentrated
salts and other substances are conveyed from agricultural lands to
the common stream or the underground water supply. This study is
concerned primarily with the physical and chemical processes as they
are now understood, with possible ways to alleviate detrimental
effects, and with economic and legal aspects of the problem.
Development of Irrigation in the United States
Irrigation is perhaps one of the most important practices
developed by man. It is an ancient art. Early civilizations in
Egypt, Mesopotamia, China, and America were founded on irriga-
tion. Reference to its use is found in the Bible. Many ancient
irrigation projects fell into disuse for reasons not now clear.
Drainage and salt problems were major factors. Greater produc-
tion control can be achieved under irrigation than with any other
system of farming. The importance of irrigation in maximizing
agricultural production can hardly be over-emphasized. Irrigation
was being practiced by the Indians of both North and South America
when Columbus made his historic voyage, and remnants of these old
systems can still be seen, some still being used, others barely dis-
cernable (1). Modern irrigation in the United States is generally
-------
recognized to have had its beginning during the middle of the nine-
teenth century with the settlement of Utah by the Mormons and the
"gold rush" to California. The expansion of irrigation in the United
States is shown in Figure 1.
In the past 75 years the total irrigated land in the United States
has increased from under four million acres to over 37 million acres,
or an increase of nearly 1,000 percent. Water diverted for irrigation
in 1965 amounted to 110. 8 bgd with consumption estimated at 64. 7 bgd
serving an area of 42 million acres (2). During the last two decades,
the value of supplemental irrigation has been recognized in the humid
eastern United States. This now totals nearly four million acres.
There is every reason to believe that the acreage of irrigated lands
will continue to increase as demands for food production increase.
Economic Importance of Irrigation
A detailed report of the economic importance of irrigation is
not appropriate in this report. However, some indication of the role
of irrigation in the agricultural and national economy seems in order.
The following statement from the Economic Research Service (3)
points this out:
First, yields per irrigated acre are often several
times those obtained for the same crop grown without
irrigation. For example, in 1954 yields of irrigated
cotton in the West were about two and a half times as
much per acre as non-irrigated cotton throughout the
United States. The U. S. Department of Agriculture
estimated for 1954 that irrigated pasture in the West
yielded about ten times as many pounds of forage per
acre as non-irrigated pasture throughout the United
States.
High-valued crops, combined with higher yields
per acre, are concentrated on irrigated land. Irrigated
cropland harvested made up less than ten percent of the
total cropland harvested in the United States in 1959.
Yet, well over a third of the total U. S. acreage in
orchards and vineyards and over 30 percent of the
acreage of vegetables harvested for sale were found
on irrigated land in the seventeen western states.
Finally, irrigated feed crops and pasture play a
significant part in stabilizing the western livestock
industry by providing a dependable feed base that per-
mits more effective use of the extensive pasture areas ,
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4O
CO
Ul
K
u
23
I 20
CO
o
o
Ul
15
10
•OUNCE Or DATA
f HOUR 1951 (1)
• ECONOMIC RESEARCH SURVEY
1
1
1890 (900 1910 1920 1930 1940 I960 I960 1970
IRRIGATED LAND IN FARMS IN THE
UNITED STATES
Figure 1.
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as well as the growth of large-scale livestock finish-
ing operations near western population centers.
It is reported (4) that 25 percent of the total value of all crop
production was derived from the irrigated cropland, representing ten
percent of the total crop acreage.
Importance and Mechanics of Return Flow
The importance of irrigation return flow as a source of supply
for downstream users was recognized early. Newell (5) states:
This effect of irrigation in increasing natural seep-
age is now well recognized, and it is often esteemed as
benefit to lower portions of a valley to have water applied
to lands higher up, since, by so doing, the amount avail-
able in the latter part of the crop season for the lower
land is increased.
Others, including Mead (6) and Wilson (7) have made similar observa-
tions .
Much of the water diverted for irrigation purposes is consumed
by the crop, but some of it finds its way back into a stream or the
underground source of supply and may be reused. Only that water
which is actually consumed is not subject to return flow.
Water consumed is considered to be that water which is changed
from the liquid to the vapor state by evaporation or transpiration.
Irrigation return flow may come from the following sources:
seepage -- water seeping from canals, ditches, and other structures
comprising the conveyance and distribution system; bypass water --
water which is returned directly to the river or source of supply with-
out being applied to the irrigated land; deep percolation -- applied
irrigation water which finds its way to the drainage system or con-
tributes to the groundwater recharge; tail water runoff (waste water) -•
that portion of the applied water that runs off the land surface. Thus,
irrigation return flow is defined as "any water diverted for irrigation
purposes that finds its way back into a source of supply -- stream or
groundwater basin" (see Figure 2).
Return flow from all of the above sources may be subject to
augmentation and pollution from sources not connected with irrigation;
i.e., precipitation, groundwater seepage, surface runoff from urban
areas, highways, and non-agricultural lands, and discharges from
industrial sources may commingle with irrigation return flow. Quan-
tity, quality, nature, and extent of pollution from commingled waters
-------
tnci«it«ti«i
UPSTREAM
FIGURE 2. MODEL OF THE IRRIGATION RETURN FLOW SYSTEM.
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have not been isolated or evaluated. This is difficult, but it is neces-
sary to properly assess the quality and pollution role of each water
use affecting the water supply.
As indicated by the definition, and as shown in Figure 2, the
mechanics of irrigation return flow are not simple. The operation
of the canal system itself may modify the water supply at the field,
both in amount and quality. A portion of the water diverted will be
lost as seepage through the canal bed and banks. Part of this "seep-
age water" will be transpired immediately by vegetation growing
along the canal right of way; the balance will find its way into some
groundwater system and may ultimately appear as irrigation return
flow. In open conveyance systems, a portion of the water diverted
will be evaporated from the free water surface. In all irrigation
systems both seepage and evaporation losses usually occur. Par-
tially offsetting these losses, the canal may receive water directly
from precipitation, through influent seepage, from cross-drainage
inflows or drainage from lands and other sources along the canal.
Some of the water diverted to an irrigation canal is used only to main-
tain head in the system for one purpose or another (i. e. , flow regula-
tion, measurement, screening, etc. ) resulting in operational losses
which are returned directly to the river.
Of the water applied to the land for irrigation, a portion is
stored within the root zone and consumptively used by the crop.
Water not so stored may percolate below the root zone (deep perco-
lation losses) or a part of it may run off the field at the end of the
irrigation run (tail water runoff) to be pumped back and reused. Tail
water runoff not reused will find its way into surface or underground
drainage systems, ultimately to appear as irrigation return flow, but
the quantity and quality will very likely be changed en route. The
water percolating below the root zone may move laterally to seepage
areas or deeply into the groundwater basin to join other water and
become a part of the hydrologic system.
The model of the irrigation return flow system proposed in
Figure 2 indicates that the water diverted for irrigation at any point
along a stream may be comprised of both virgin flow of the stream and
return flow. The proportion of applied water appearing in return flow
may vary from zero to nearly one-hundred percent. For example,
on the lower Sevier River in Utah, practically all of the water diverted
at certain seasons of the year is return flow. It is mostly from irri-
gation, but it also comes from such other sources as municipal and
industrial waste water. The cycle of diversions and return flow illus-
trated in Figure 2 is repeated many times on the Sevier River, for
there are numerous diversions, seven of which take the entire flow
at the point of diversion (8).
-------
The diversion-return-flow cycle shown in Figure 2 is typicaKof
many western rivers. The water in the river at any point is com-
posed of natural inflow, irrigation return flow, and return flow of
other used water, the proportions depending upon the number of
diversions, the extent and diversity of use, the position on the stream,
and the natural inflow or "make" of the stream.
Nature and Extent of the Pollution Problem
of Irrigation Return .Flows
Although there are many aspects of irrigation return flow, the
principal two are the quantity of water and the salt content. Salt is a
natural product of geologic weathering. Pillsbury (9) developed a
relationship between water production and salt production on several
western watersheds. Figure 3 indicates that salt production in the
streams studied varied from 0. 1 tons/a. f. on streams producing
1000 a.f. /sq. mi to over 5 tons/a. f. on streams producing only
1.0 a. f. /sq. mi.
Over the ages the rivers have carried this salt load to the oceans,
This important role of precipitation and drainage into streams and
rivers, although coming about naturally, maintains the quantity of dis-
solved minerals in the soil at levels which permit plant growth. In
changing from natural vegetation to agricultural crops and imposing
irrigation, man has diverted the salt with the irrigation water and
applied it to agricultural land. The diverted salt must be removed
from the agricultural land; otherwise, the lands become too saline
for continued agriculture. The major problem is in transporting this
total salt in the reduced streamflow and dealing with the increased
concentration of the salts downstream. Many agriculturalists ques-
tion whether this concentration effect really should be called pollution.
Pollution or not, the salts must be dealt with, they must be removed
from the agricultural land and disposed of in acceptable ways. In
commenting on this problem, Quigley (8), formerly Commissioner of
FWPCA, had the following to say:
Salt-laden return flows from irrigation systems
admittedly constitute a difficult technical and engineer-
ing problem, but here too there is room for improve-
ment in the overall management of many of our irriga-
tion systems. Once it has been accepted that the problem
must be dealt with, both the economics and the technology
will be worked out, just as the economics and the tech-
nology of dealing "with many industrial wastes will be
worked out.
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2!02
CL
CO
o 10
O
o:
a.
(SP)- 10 WP
00
71
Figure 3.
I 10 To5" 103
WATER PRODUCTION (WP)- Ac. ft./miVyr.
Approximate relationship of salt production to water production for several
rivers in the Western United States (9).
10
-------
Normally, salt diverted in the practice of irrigated agriculture
is returned to the river with a portion of the water diverted. Thus,
the salts are linked back to the water course in which they would have
been transported naturally, but by a smaller quantity of water. This
increases the concentration which often is objectionable to certain
downstream users. Each successive diversion and irrigation cycle
on a stream further increases the salt concentration. Under ideal
salt balance conditions (no buildup of salt in the lands), the residual
flow entering the oceans would contain all of the salts that would have
been transported by the pristine river if none of the water had been
diverted and consumptively used to produce crops. "Return flow is
the mechanism by which all the salt imported to the project through
the diversion can be returned to the river" (9).
Superimposed upon the interruption in the natural flow of salts
to the sea by the irrigation diversion is the imposition of fertilizers
and pesticides into the cycle. The extent to which these are dissolved
or suspended and transported by irrigation water to appear in irriga-
tion return flow has only been partially investigated. The implications
have not yet been well defined. Nevertheless, to the degree these are
a source of added pollution, they must be dealt with in the interest of
society.
Relation of Irrigation Return Flow Problems to
Present Legislative Water Quality Standards
and General Pollution Control Problems
Irrigation return flow has long been considered to be beneficial
because it was a recognized source of supply for the irrigated areas
further downstream. This was observed by Newell (5), Mead (6),
Wilson (7), and was further emphasized by Hutchins (10) in the follow-
ing quote:
Return flow is a common phenomenon in western
irrigated regions and many water rights are predicated
wholly or partly upon it. For example, on streams such
as the Provo River in Utah, downstream development
occurred first, and return flow from junior upstream
diversions not only satisfied the requirements of earlier
downstream appropriation, but actually benefited them by
prolonging the seasonal supply. On the other hand, on
the South Platte in Colorado, upstream development
occurred first and the increasing return flow made pro-
gressive downstream development possible and eventually
added materially to the value of the junior downstream
rights.
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10
Most of the western states have legislation dealing with the
procedures for acquiring rights to return flow. In addition, numerous
court decisions have been rendered regarding the ownership of return
flow water. In most all cases, the return flow was considered to be
a beneficial resource and its ownership was highly valued. The major
concern of water rights legislation and administration has been with
ownership and total water supply. At this level, little thought or
attention has been given to water quality and pollution, although qual-
ity has been considered in irrigation projects planning for a number
of years, and state health authorities have been concerned about pol-
lution of water for domestic supplies. Interstate compacts, treaties,
and irrigation water rights have generally been silent on the matter
of quality and especially so as it concerns dissolved salts. However,
the mounting public concern over water pollution and resulting legis-
lation in recent years requires a consideration of all possible vectors
in the pollution spectrum. Thus irrigation return flow, because of
its generally high salt content and the possibility of transmitting other
agricultural pollutants into public water supplies, has come under
increasing scrutiny.
The Federal Water Pollution Control Act (1948) with amend-
ments marked a major entry of the federal government into active
participation in water quality control. However, the issue of dis-
solved solids in irrigation return flow as a pollutant was hardly
raised. The Water Quality Act of 1965 authorized the states to estab-
lish water quality standards on all interstate streams and coastal
waters, thus including irrigation return flow. Irrigated agriculture
must, therefore, become concerned with water quality standards
and with general pollution control legislation. National policy, philos-
ophy, and legislation concerned with the pollution aspects of irriga-
tion return flow must be developed carefully in order not to jeopard-
ize the vast economy that is based on irrigated agriculture. It must
permit the wise and prudent use of water and still maintain or sub-
stitute for the natural processes in the undepleted rivers in keeping
the salt balance of the river drainage basins.
Special Problems Due to Consumptive Use
The quality problem raised by irrigation return flow is of
special concern because irrigated agriculture is the largest con-
sumer of public water supplies. Most municipal, industrial, and
recreational uses of water do not consume much of the water; that
is, they do not change it from the liquid to the vapor phase, but only
use the water for the purpose intended, adding various pollutants in
the process, but returning most of the used water. Irrigated agri-
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11
culture, on the other hand, diverts large quantities of water, con-
sumes from one-third to one-half or more of the total water diverted,
and returns the balance to the streams and underground supply as
irrigation return flow, presumably transporting all of the dissolved
solids diverted back into the stream. Water consumption by agricul-
tural crops may range from 5,000 to 10,000 gallons per acre per day,
whereas the actual consumption by man to satisfy his normal body
functions is less than one gallon per person per day.
While increasing salt concentration, the agricultural process
may, on the other hand, remove other pollutants. For example,
nutrients and other organic wastes deposited on agricultural land with
irrigation water may be used by the crop, fixed by the soil, or de-
graded so that they are not contained in the irrigation return flow.
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13
IRRIGATION PRACTICE
Mechanics ot Irrigation Practice
Irrigation practice involves the control of water on the Land in
order to manage the soil moisture environment to maximize agricul-
tural production. This control extends from the diversion at the river
or other source of supply to the drainage of water from the soil profile.
Irrigation practice, therefore, includes diversion, conveyance, meas-
urement, application, cultivation, pump back or reuse, runoff, and
drainage. The complexity of the irrigation process and the age-old
custom it represents has led many to refer to irrigation as an "art"
rather than a science. True, many of the principles of good irriga-
tion practice have been handed down from generation to generation,
and only in recent years have the various sciences been applied to the
practice of irrigation. Today's irrigation engineer, designing and
operating irrigation projects, should have knowledge or professional
support in the following technical areas: hydrology, fluid mechanics,
water requirements of crops, methods of water delivery, methods of
water application, water rights, soils, plants, fertilizers, pesticides,
soil physics, infiltration, movement of water in soils, drainage, cul-
tivation requirements, and a general knowledge of agricultural produc-
tion under irrigation.
Most important from the standpoint of irrigation return flow are
the problems of water application methods, soil moisture storage,
evapotranspiration, salt balance concepts, nutrients, pesticides,
drainage, and their interrelationships which alter the quality of the
irrigation return flow.
Application methods
In the process of irrigating crops, water is applied to the soil by
one of several methods, including surface irrigation (furrows, basins,
borders, etc. ), sprinkler irrigation and subsurface application.
The effect of the method of application on quality and quantity of
irrigation return flows has not been given detailed study. However, it
stands to reason that surface methods of application will be most
important in relation to tail water runoff and may, therefore, have a
more prominent role in transporting pollutants originating or available
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14
above or at the soil surface. Modern methods of irrigation and empha-
sis on irrigation efficiency have greatly reduced the proportion of sur-
face runoff. In many systems, such as furrow irrigation, farmers
have collected the surface runoff and employed "pump back" systems
to salvage water formerly lost. In other systems the plans of the
irrigation layout have been made to prevent or recapture the runoff.
This is only natural since surface runoff is the one loss the irrigator
can observe, while seepage and deep percolation are not so obvious.
Sprinkler irrigation and subirrigation methods will affect the
quality of waters infiltrating in and percolating through the soil, for
surface runoff should not be a factor -with these methods. Sprinkler
irrigation may also be a factor in washing pesticide residues from
plant leaves or in washing certain pollutants from the air.
Soil moisture storage
Irrigation is the practice of supplementing natural precipitation
by applying water to the soil. Water is stored within the root zone
and later used by agricultural crops. During the irrigation process,
the soil is seldom completely saturated, although during and
immediately following irrigation considerable gravitational or free
water may be found in the pore space of the soil. Depending upon
internal drainage conditions and the use of water by crops, the
gravitational water moves below the plant root zone and the remain-
ing water surrounding the soil particles is held by capillary forces
under tension. This capillary moisture moves only slowly if at all
through the soil and is said to be stored in the soil. This moisture is
available for use by agricultural crops which must exert tension forces
to extract it from the soil. As water is taken up by the plant roots or
evaporated, the tension on the remaining water gradually increases
until the plants can no longer extract sufficient amounts to meet their
daily requirements. Wilting takes place and unless additional water
is provided, the plants die. To characterize these various soil mois-
ture levels, irrigation scientists have defined the following terms:
saturation -- water within the soil profile completely filling all of the
pore space, a condition generally considered to exist below the water
table; water table -- the level at which the soil water is maintained at
atmospheric pressure, the boundary line between saturated and un-
saturated soil; field moisture capacity -- usually considered to be the
amount of water (percentage) that a well-drained agricultural soil will
hold within the root zone against gravitational forces, and also con-
sidered to be a moisture tension in the soil of 0. 1 to 0. Z atmospheres;
wilting point -- the moisture retained by the soil after permanent wilt-
ing of plants, and this varies with different plants (approximately 15
atmospheres); available moisture -- the water stored in the plant root
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15
zone under tension forces between 0. 1 and 15 atmospheres. Con-
sidered to be the capillary water existing between field capacity and
the wilting point; readily available moisture -- that portion of the
stored water that can be used by crops without developing high tension
forces; and stored water -- water stored within the plant root zone to
be used by agricultural crops.
Evapotranspiration
In irrigated agriculture "evapotranspiration" refers to the
evaporation or transpiration of water in the crop-producing area. It
is dependent upon many factors, primarily the energy from incoming
solar radiation, but available soil moisture, temperature, crop vari-
ety, stage of crop growth, length of growing season, wind, relative
humidity, and other factors are involved. Evapotranspiration results
in consumptive use of water averaging as much as 0.25 inches (6,700
gallons per acre) per day during the peak growing season. Daily maxi-
mums of as much as 1. 0 inch per day (27, 000 gallons per acre per day)
have been reported. The consumptive use of water by crops (evapo-
transpiration) varies from 15 to 20 inches for a crop of grain to more
than 60 inches for citrus and alfalfa which grow all year.
The most important factor in the relationship of evapotranspira-
tion and irrigation return flow is that the water consumed is relatively
pure water, the dissolved solids being left in the soil as precipitates or
dissolved in the water not consumed. Thus, the process has the effect
of concentrating the total salt load in the fraction of the water returned
to the stream as return flow.
Salt Balance Concept
The general salt balance concept introduced by Schofield (11)
relates the amount of soluble salt brought into a given area by irri-
gation water to the amount discharged by the drainage water. Unless
the same quantity is removed that is added an accumulation of salt
occurs and the land cannot be kept permanently in crops. This con-
cept can be applied to a given piece of land or to an entire watershed.
For the common salts in river water, the concept is expressed by an
equation:
Q.C + S + others - (Q ,C + S + S ) = 0
i w d ppt c
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16
where
Q. = quantity of irrigation water
Q , = quantity of drainage water
C = concentration of salt
S = salt from weathering
S , = salt precipitated
S = salt in the crops
This concept is intended as a useful tool in the control of
salinity on the land and for water management. Wilcox and Resch (12)
pioneered a salt balance and leaching requirement study on the Rio
Grande Project and concluded that salt balance is a reliable and use-
ful indicator of year-to-year trends in salinity conditions. When
applied to a large area it can be misleading because inadequate leach-
ing and salt accumulation can occur in one portion of the region while
leaching of previously accumulated salt can occur from another por-
tion, with a resulting apparently favorable overall balance.
Concentration of salts
A concentration of soluble salts is an unavoidable result of con-
sumptive use of water by irrigated crops. As water is evaporated or
transpired by the crop, salts in the irrigation water applied to the
land are necessarily concentrated. The major portion of the mass of
salts in the applied irrigation water remains soluble in the soil solu-
tion. Some of the less soluble salts, such as calcium carbonate, may
precipitate in the soil. To maintain a favorable salt balance, and a
permanent agriculture, a more saline water must leave the land area
as "return flow" either by percolating below the root zone into the
ground water or through a natural or artificial drainage system.
Leaching
To prevent an accumulation of soluble salts in the soil and thus
maintain a favorable salt balance in the root zone, the land should
receive water in excess of that required by the crop so that the ex-
cess can pass through the soil profile and leach out the soluble salts.
The amount of water required for leaching, known as the leaching
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17
requirement, is determined by the concentration of salt in the irriga-
tion water and the concentration in the soil solution that can be toler-
ated by the crop. As defined by the U. S. Salinity Laboratory (13),
the leaching ratio (LR) is the proportion of the irrigation water that
must pass from the soil as drainage •water in order to maintain a
favorable salt balance in the soil. This can be expressed as:
LR = D,/D. = C./C ,
d i id
where
LR = leaching ratio
D , = depth of drainage water removed
D. = depth of irrigation water applied
C. = concentration of salts in the irrigation water
C , = concentration of the drainage water
The ratio may also be expressed in terms of electrical conductivities
EC./EC ,. In this equation, only the water and salt added as irriga-
tion water and the salt removed by the drainage water are considered.
Where other salts are involved or the rainfall is appreciable, adjust-
ments, such as shown by Reeve and Fireman (14) or by Bouwer (15),
can be made. Where the quality of the return flow water for reuse is
of concern, the amount of leaching water may need to be increased in
order to provide dilution of the salts. In practice, maintaining the
salt balance has been given priority, and the resulting quality of drain-
age water has seldom been considered. The leaching requirement is
specific for any specified conditions of crop tolerance, concentration
of irrigation water and quality of the return flow. The usual range is
10 to 30 percent. The amount of leaching water provided under usual
irrigation practices (irrigation efficiency 50 to 70 percent) is 30 to 50
percent.
Ion exchange
Normal soils contain appreciable quantities of calcium, mag-
nesium, potassium, and hydrogen in ionic form held to the soil
particles in an exchangeable form. As irrigation water is evaporated
and transpired, the concentration of salts in the soil solution increases.
These salts are in ionic form and some of the cations in solution re-
place some of the cations held by the soil. The equilibrium level of
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18
sodium on the soil depends on the proportion of sodium in the soil
solution. A high proportion induces a replacement of calcium and
magnesium on the soil particles by sodium. Both soils and plants
are adversely affected by high levels of exchangeable sodium. The
U. S. Salinity Laboratory (13) developed the exchangeable sodium
adsorption ratio (SAR) for irrigation waters:
Na+
SAR = .
Ca++ + Mg++
2
the Na , Ca and Mg are expressed as milliequivalents per liter.
As an index of the danger of adverse sodium effects, for sensitive
fruit crops, the tolerance limit for SAR may be as low as 4. For
more tolerant general field crops, the limit is likely to be within the
range of 8 to 16. This, however, varies with such soil factors as
texture and the kind of clay minerals present.
Chemical fixation and precipitation
In addition to concentrating salts and altering the proportion of
calcium and sodium by ionic exchange, there are several other pos-
sible changes in the composition of irrigation water as it passes on to
the return flow. One of these changes is the precipitation of calcium
carbonate. In the presence of bicarbonate ions in the water, calcium
is precipitated as the relatively insoluble carbonate and the sodium
salt remains in solution. This results in an increase of the proportion
of sodium in the soil solution in a higher SAR value, and an increased
sodium hazard.
Phosphates in water at relatively high concentrations may be
reduced by precipitation as slightly soluble calcium phosphates and
iron and aluminum phosphates, or be "fixed" by lime in the soils.
Whether drainage water contains more or less phosphate than the
irrigation water depends on such factors as the amount in the irriga-
tion water when applied and the nature of the soil being irrigated.
A number of other soluble constituents in the irrigation water,
such as the heavy metals, are likely to occur in less concentration in
the return flow than in the applied water when there are appreciable
amounts in the irrigation water. Sources of heavy metals in the
irrigation water are pesticides, impurities in fertilizers, particularly
phosphates, wastes from gasoline combustion and coal combustion,
metal smelting, etc. , and washed from the air by rain and snow. In
the process of irrigation the metals are largely removed by the soil
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19
as precipitates, as chelation in living organisms, or by the organic
matter in the soil. Heavy metals held by the soil are difficult to
remove and tend to stay in the soil as pollutants rather than move out
with the drainage water.
Nutrients
The plant nutrients nitrogen and phosphorus stimulate aquatic
plant growth in water of storage and conveyance systems. Nitrate-
nitrogen is highly soluble and moves with water. The salt balance
concept is difficult to apply to nitrate because of the many sources
as well as possible losses. The nature of the complexity is indicated
in a nitrate balance equation:
(Q.C + NO, +NC> + NO. ) - (N0_ +NC> ) = Q C
in 3 3.3. 3 3. dn
om rf f c f
where
Q. = quantity of irrigation water
C = nitrate concentration
n
NO = nitrate from organic matter
om
NO, = nitrate from rain and fixation
rf
NO = nitrate from fertilizers
3f
NO = nitrate removed by crops
c
NO = nitrate removed by reduction
r
Q = quantity of drainage water
It is evident that irrigation may add to or remove nitrate from water
being used for irrigation so the nitrate concentration of the return
flow may be either greater or less than in irrigation water. An
important aspect in nitrate pollution abatement is the identification
and control of the major sources.
As previously indicated, phosphate does not behave as a soluble
salt, such a sodium chloride, which is relatively easy to leach from
the soil and into the return flow. Evaluations are further complicated
by the fact that phosphorus can exist in water in at least five norms:
soluble orthophosphates, soluble organics, insoluble organics, ad-
sorbed on suspended materials, and as a component of suspended
minerals and organic matter.
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20
The salt balance concept is likewise difficult to apply because of
the many sources of phosphate to the soil and the numerous reactions
influencing its concentration in the soil solution. This is illustrated
by the following terms which are dynamic and difficult to evaluate:
Vp.' "
where
Q. = quantity of irrigation water
C . = phosphate concentration in Q
Pr - phosphate from fertilizer
P = phosphate from organic matter
P - phosphate from pesticides
P = phosphate from soil minerals
Qj = quantity of drainage water
C j = phosphate concentration of drainage water
P = phosphate precipitated and absorbed
pa
P = phosphate removed by crop
P = phosphate removed by erosion
It is evident that there are many possible sources of phosphorus
in water pollution as well as several likely ways to remove soluble
phosphorus from soil and water.
Pesticides
Numerous compounds are used to control weeds, insects, etc.
Some are decomposed or degraded biochemically and photochemically.
Others are relatively unaltered and are adsorbed by the soil and move
only with the soil. Few, if any, move through the soil in proportion
to the .amount of leaching. Because these processes are insufficiently
understood, it is impossible to apply the salt balance concept to most
of the pesticides.
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21
Consequences to Irrigation Return Flow
The intricate nature of the water-soil-quality complex makes
the prediction of the return flow variables extremely uncertain.
Irrigation return flow is a dependent function which may be expressed
by the following relationship:
IRF=f(Q.,C ,B,T ,M ,S ,S , ET.D , C, F )
is aamc p p
where
IRF = irrigation return flow (quantity)
Q. = quantity of irrigation water diverted
C = canal seepage
S
B = bypass water
T = time of application
M = method and rate of application
S = soil moisture
m
S = soil characteristics; i. e. , depth, permeability,
Q
structure, texture, stratification, etc.
ET = evapotranspiration
D = deep percolation
P
C = type of crop
F = farm practices
P
Likewise, the quality of irrigation return flow is a dependent function,
being controlled by the quantity of irrigation return flow as expressed
above with additional quality inputs. The following relationship shows
its complexity:
IRF =f(Q. , C ,B,T,M,S ,S ,ET,D , C ,F , F ,P . r, O.)
q iq sq q a a mq cc pq q pq a a" f i
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22
where
IRF = irrigation return flow quality
Q.. = quality and quantity aspects of applied irrigation
water
= canal seepage quality change
sq
B = bypass water quality
T = time of application
3,
M = method and rate of application
S = soil moisture quality
mq ^ '
S = additional soil characteristics such as cation
cc
exchange capacity, basic soil compounds,
bacteriological activity, chelation, fixation,
oxidation, and other factors which may alter
the soil-chemistry-bacteria-water system
ET = evapotranspiration
D = quality of water percolation below the root zone
pq
C = crop influence on quality
F •= farm practice effect on quality
F = fertilizer application
P = pesticide application
cl
C,. = climatological factors; i. e. , temperature,
precipitation, wind, sunshine, etc.
O. = other influences; i. e. , elements carried from
the air to the farmland by precipitation, indus-
trial pollution of soils or water, municipal inputs
from runoff or sewage, etc.
Both the quantity and quality of irrigation return flow are
dependent variables, with the soil and soil moisture playing important
roles as shown in the above functional relationships. The soil is a
dynamic chemical mass capable of exerting a major change in the
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23
quality of any water passing through it. The soil moisture regime
is also undergoing constant change, with the net result being a highly
variable output so far as quality and quantity of irrigation return flow
are concerned.
Soil moisture regime
The soil root zone is often referred to as the storage reservoir
for moisture used by the plants. Maximum storage in this reservoir
is considered to be field capacity, with the minimum being the wilting
point, although soils may be dried below the wilting percentage by
evaporation. In the management of irrigated soils, water is usually
added to the soil by precipitation or by any of several irrigation
methods before the plants have depleted the moisture to the level of
wilting. Sufficient moisture is usually added to bring the root zone
soil to "field capacity. " At this point the soil water within the root
zone contains a given quantity of dissolved solids, nutrients, and
other constituents, depending upon the interaction expressed in the
above function for IRFQ . Irrigations in excess of the amount needed
to bring the moisture level to field capacity will cause deep percolation
below the root zone, with quality constituents representing the particu-
lar condition for that particular time.
If only enough water is added in a given irrigation to bring the
soil to field capacity there may be little or no movement of water
below the root zone. The salts and other impurities applied with the
water remain in the soil, to be concentrated in the constantly decreas-
ing amount of soil water or precipitated in the soil. Some of the
cations may become associated with the soil particles in the base
exchange reaction. Continued irrigations of this type coupled with the
constant removal of relatively pure water by plants in the evapotrans-
piration process induces a salt buildup in the soil, increasing the
concentration of the soil water and ultimately presenting the possibility
of inhibiting plant growth. Irrigation experts have been primarily con-
cerned with achieving the type of irrigation outlined above to eliminate
deep percolation losses and only refill the root zone to field capacity
at a given irrigation. It is now recognized that some water must move
through the soil profile, otherwise a salt balance in the soil profile
cannot be maintained.
It can be seen from the above that the time, amount, and
frequency of irrigation which result in movement of water below the
root zone will greatly influence the concentrations in the water mov-
ing below the root zone. Thus, the quality of the drainage water leav-
ing the area and the resultant quality of the irrigation return flow will
be affected.
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24
Drainage water
In irrigated areas, drainage water may come from either sur-
face sources or water which has moved through the soil profile. In
either case the water may undergo substantial but different quality
changes due to the unique exposure condition.
Drainage water from surface sources. This source of irrigation
return flow consists mainly of surface runoff from irrigated land.
Because of its limited contact and exposure at the soil surface, one
might expect the water to contain the following:
(a) Dissolved solids concentration only slightly
greater than in the applied irrigation water.
(b) Variable and fluctuating amounts of pesticides
that have been applied.
(c) Variable amounts of fertilizers.
(d) Organic and foreign matter from households,
barnyards, adjacent lands, etc.
(e) Variable amounts of sediment, colloidal and
adsorbed material.
(f ) Debris, crop residue and other substances floated
from the soil surface.
Drainage water which has moved through the soil profile. Be-
cause of its more intimate contact with the soil and being subject to
the dynamic soil moisture regime outlined above, this source of
irrigation return flow water might have greatly different quality
characteristics from the waters originating mainly from surface run-
off. In the case of water passing through the soil profile, one might
expect:
(a) The water to be higher in dissolved solids than
the applied irrigation water.
(b) The distribution of various cations and anions
to be different than in the applied water.
(c) The total salt load to be greater or less, depend-
ing upon whether there has been deposition or leach-
ing.
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25
(d) The water to contain'little or no sediment or
colloidal material.
(e) The nitrate content to be less than in the applied
irrigation water if the irrigation water was initially
high in nitrate and, conversely, the nitrate content to
be greater if the applied irrigation water had little
or none.
(f ) A general reduction in phosphorus unless the
applied irrigation water had little or no phosphorus.
(g) A reduction of all bio-degradable material such as
detergents, etc.
(h) A general reduction of oxidizable organic sub-
stances.
(i) A reduction of pathogenic organisms and coliform
bacteria.
Many other changes are also likely.
Drainage water from either source discussed above will have an
effect upon the receiving water in proportion to respective discharges
and the relative quality of the receiving water. The composite flow
below the point of confluence may contain proportionately more or fewer
undesirable constituents than originally.
Impact of Poor Water Quality on the Irrigation Farmer
The use of saline waters for irrigation imposes extra burdens
on the irrigation farmer. Salinity generally reduces growth and yield.
It may restrict production to the more tolerant crops. Generally, the
farmer must apply an additional amount of water to maintain the salt
balance at an acceptable level of soil salinity hence each unit of water
has a lower value. Better drainage conditions may be required, and
sometimes the adequacy of drainage cannot be controlled by an
individual farmer, but requires group action. Outlets and collectors
generally must be provided on a project or district basis to enable
individual farmers to provide the necessary additional farm drainage.
The farmer using low quality water may be restricted in his irrigation
methods, or he may have to adopt special practices to obtain germina-
tion. Since the irrigation method must be suited to the crop grown,
this may further restrict the crops that can be grown economically.
Sprinkling may not be practical because of the accumulation of salts,
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26
especially chlorides, on the leaves, and the resulting leaf burn or
defoliation.
In some instances, and where this is possible, the more saline
water may have to be mixed with a water of better quality in order to
use it for irrigation. In most cases, however, the farmer has no
opportunity to dilute undesirable water and must use what is available.
When a farmer has a well for supplemental supplies, but uses gravity
supplies to the extent available, mixing the two may be feasible to
produce an acceptable quality. Often groundwater is more saline than
gravity supplies. It can be used to provide the required drainage by
pumping it into the canal system and m'ixing it with the gravity supply.
This practice provides adequate control of the water table (drainage),
and appreciable additional water supply to several irrigation districts
in California, including the very successful operations of the Turlock
and Modesto Irrigation Districts.
The leaching required when using moderately saline waters may
impose an additional burden in the form of a greater fertilizer require-
ment. Leaching salts from the soil also removes nutrients, especially
nitrates. Sometimes, heavier than normal applications of phosphate
fertilizers improve the production on saline or sodic soils. In general,
the farmer often must practice special techniques to cope with the ad-
verse effects of salt and other pollutants.
Principal Effect of Salinity
The worst effect of poor water quality is a lowered agricultural
production. Reduced yields result when the total salinity of the soil
solution in the root zone exceeds certain values (13). It must be
emphasized that it is not the quality of the irrigation water per se,
but the concentration of the salts in the root zone, that is important.
The increased osmotic concentration of the soil solution inhibits entry
of water into the root system and restricts growth and yield. Direct
measurement of the salt concentration in the root zone is difficult,
and usually not practical under field conditions. The standard proce-
dure is to prepare a saturation extract (13) from a soil sample and to
determine the electrical conductance (EC) of the extract. The salinity
of the soil saturation extract is much less than the actual salinity of
the soil solution, for the soil moisture ranges between field capacity
and wilting percentage. The ratios depend on the relative values of
wilting percentage, field capacity and saturation, and on the composi-
tion of the salts present. The use of saline waters for irrigation may
be a principal cause of high soil salinity Levels and result in an
appreciable reduction in yield, which often goes unnoticed because
salinity may not result in any distinct symptoms even though reduction
in growth and yield may be significant.
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21
In 1945, Magistad (16) published a review of the Literature on
plant growth and salinity relations, containing 362 references. A
similar review, to bring the subject up-to-date, published by Hayward
and Bernstein (17) in 1958, included Z21 references. Many of these
references stress the complex relationships between plant growth,
soils, salinity, and sodic or alkali conditions.
Distribution and concentration of salts
in the root zone
Since it is the salinity of the soil solution rather than that of the
water applied that affects production, some knowledge of factors that
affect the concentration and distribution of the salt in the root zone is
important from the farmer's point of view. The more important of
these factors are: adequacy of drainage from the soil profile; quality
of irrigation water applied; ratio of the depth of water applied to the
actual evapotranspiration; and the irrigation method.
Adequacy of drainage. Adequate drainage of the soil profile is
essential to a permanent irrigation agriculture. Unless the excess
water applied is removed from the soil, the water table will rise and
the salt concentration will increase. The adequacy of drainage can
best be judged by the depth of the water table below the ground surface.
This is often greatly influenced by soil texture and topography.
When the water table is near the surface, less than four to six
feet, there usually will be an appreciable fluctuation in water table
depth between irrigations. Each irrigation will cause a rapid rise in
the water table, followed by a period of decline which is due both to the
removal of moisture from the root zone by evapotranspiration and the
resulting upward movement of soil moisture from the saturated zone
into the root zone, and to the removal of groundwater from the satu-
rated zone by drainage, either natural or man-made. The water
removed by the drainage carries with it the salt in solution, but the
moisture removed by evapotranspiration leaves the salt in the soil
in the form of increased concentration of the soil solution, and some-
times as precipitates of the less soluble salts of calcium and magne-
sium.
When drainage is impaired, the salt concentration in the root
zone generally increases, and unless a salt balance can be established
through better drainage, the salinity will increase to such a degree
that no crops can be grown. Sometimes serious salinity problems
result from poor drainage even when the irrigation water is of excel-
lent quality (18). Adequate drainage is essential before soil salinity
can be improved by leaching. Better drainage, with a lower water
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28
table and better control of the water table, is more important where
the irrigation water is of poor quality than where it is of good quality.
Increased costs for drainage may be a necessary burden on the irriga-
tion farmer using low quality water.
Quality of irrigation water. Because of the concentrating effect
of evapotranspiration, quality of irrigation water directly affects the
concentration of salts in the root zone. For example, water with a
conductance of only 100 |j.mhos would have to be concentrated to 1/20
of its volume, providing none of the salts precipitated, in order to
reach a conductance of 2 mmhos, while water with a conductance of
1 mmhos would only have to be concentrated to half its volume to reach
the same concentration in the soil. Actually, the difference would be
greater than this. Water with a conductance of 100 |j.mhos would prob-
ably have a much higher percentage of calcium and bicarbonate ions
than one with a conductance of 1 mmhos, and since some of these
would precipitate on concentration, the water with an initial conductance
of 100,|a.mhos might have to be reduced to 1/40 or 1/50 of its original
volume to reach a conductance level of 2 mmhos. Examples were cited
in a discussion by Christiansen and Thome (19). This means that the
leaching requirement, the excess water that must be applied in addi-
tion to the evapotranspiration to maintain a given level of soil salinity,
increases faster than the salinity of the water. This imposes an added
burden on the farmer.
The term "quality of irrigation water" implies other factors
besides salt concentration, such as the composition of the salts,
especially with respect to the presence and percentage of sodium,
presence of residual sodium carbonate, and toxic substances such as
boron and/or pesticides. Several schemes have been proposed for
evaluating, or classifying, waters with respect to their use for irri-
gation. None of them completely satisfy all requirements and should
be used only as a tentative guide. For permeable soils with excellent
drainage, and where adequate applications are made to insure leach-
ing, water of poor quality may result in greater production than would
much better water where drainage is impaired.
The amount, or percentage., of sodium in the water is very
important. Water with a fairly high sodium percentage, say greater
than 50 percent, will generally increase in sodium percentage upon
concentration in the soil to levels that produce relatively high exchange-
able sodium percentages in the soil. Soils that become high in ex-
changeable sodium are more difficult to leach, for two reasons: they
tend to disperse, with a resulting reduction in permeability when leach-
ing is attempted, and they may require the addition of an amendment,
such as gypsum, to replace the exchangeable sodium. Soils that con-
tain more than 15 percent exchangeable sodium are classified as sodic
(13).
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29
The presence of toxic substances such as boron, or possibly a
pesticide that degrades slowly, may limit the usefulness and value of
poor quality water even more than do normal salts. Many crops are
very sensitive to boron and concentrations of more than 1 ppm in the
irrigation water may restrict production to the more tolerant crops.
The amount and frequency of water applied. The amount of water
applied and the degree of leaching accomplished in the root zone have a
major effect on the concentration and composition of the salts left in the
root zone. Even though extra water might be available to the farmer,
the drainage conditions may Limit the amount of water that can be used
effectively for leaching.
In 1943, Wilcox and Christiansen (unpublished data) found well
water being used for irrigation in the Wellton-Mohawk area in southern
Arizona with a total salt content of more than 10, 000 mg/l (EC > 15
mmhos/cm). Because of excellent drainage and soil conditions,
saturation extracts from soil samples obtained were not as high as for
many soils where waters of much lower salt content are used. The
relatively low salt content in the root zone was attributed to the large
amount of water used for irrigation and to the excellent drainage.
The amount of water that can be applied by a farmer is frequently
limited by his water right or by the available supply. Sometimes, how-
ever, he can take advantage of available supplies during the non-
irrigation season to thoroughly leach his soil, providing drainage con-
ditions permit. Where the farmer has control of his water supply,
such as when he obtains the water from his private well, he can better
manage his soils by a proper degree of leaching, and can offset to a
considerable extent the detrimental effects of salinity, especially
where he is not plagued by lack of drainage. Areas that depend on
groundwater for all, or an appreciable part of, the water supply often
are free from drainage problems, and can be leached more effectively
because of the low water tables. Generally, however, pumped water
is more costly than gravity supplies, and this also is an added burden
to the farmer. Leaching may be partly or completely taken care of by
seasonal rainfall, although irrigation may be required during the dry
season.
Irrigation method. The irrigation method used has an appreci-
able effect on the resulting concentration and distribution of salts in
the soil profile. Furrow irrigation, for example, is not as effective
for leaching and may result in high concentrations of salt near the
surface of the beds between the furrows. Rotation of crops from those
conventionally irrigated by furrows, such as corn, cotton and vege-
tables, to alfalfa or other crops that can be irrigated by flooding
(border strips or basins) is an effective way to prevent continuous
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30
buildup of salts in the soil profile. For high salt waters, the furrow
method is usually less satisfactory. Salt-tolerant crops that can be
flooded should be grown when possible.
Sprinkling is also a good method to provide leaching when ade-
quate amounts of water are applied. Sometimes, however, because
of a user's ability to spread water effectively in small applications by
sprinkling, he may not apply an adequate amount of water, and there
may be a buildup of salts even though drainage is entirely adequate.
There are other limitations in the use of sprinkling with water of
poor quality. Salts may precipitate on the leaves of crops and produce
leaf burn and defoliation. This is especially true where "under tree"
sprinklers are used in orchards. Leaves on the lower branches are
often wet only very lightly and salts precipitate and accumulate on
these leaves because they are never thoroughly washed by the sprinklers.
On field crops less trouble is experienced and, except for relatively
saline waters, sprinkling should be satisfactory because the salts are
thoroughly washed from the leaves.
Effect on seed germination
The salinity effect on plant growth is often more pronounced on
germination and during the seedling stage. Where salts have accumu-
lated in the soil near the surface as a result of a high water table, it
may be difficult to obtain satisfactory germination without pre-
irrigation which temporarily reduces the salt content of the soil near
the surface. Unfortunately, under conditions of poor drainage, heavy
applications before planting will cause an additional rise in the water
table and may do more harm than good.
Under some saline soil conditions, satisfactory germination of
certain row crops can be obtained by planting along the edge of the
furrow that has been pre-irrigated instead of in the top of the bed where
the salt concentration is greater. This is a standard practice in some
areas where there is appreciable salinity and where the water supply
is not of the best quality.
Other farm management practices
to offset effects of salinity
In addition to the management practices that have been suggested
to offset some of the detrimental effects of salinity and/or sodic condi-
tions, such as increased water use for leaching, the need for better
drainage, and proper irrigation methods, there are some additional
practices that are helpful under certain conditions.
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31
Where soils have developed low infiltration rates as a result of
an increase in exchangeable sodium, or because of detrimental
management practices such as excessive cultivation, it is especially
important for the farmer to recognize the problem, and to do all
possible to correct the difficulty. Some silt soils are readily dis-
persed, and develop infiltration problems under ordinary management
practices. This is especially true under furrow irrigation where the
amount of water applied is not adequate because of low infiltration
rates. The problem becomes more intensified with time as a result
of a buildup in salinity, and especially in exchangeable sodium.
A problem of this kind was experienced in the Coachella Valley
in California (20) where a date garden had been irrigated by the furrow
method for a number of years. Production was quite variable and un-
satisfactory. A study indicated that the infiltration rates were ex-
tremely Low, possibly as a result of the application of low salinity-
high sodium water, and under the practices being followed, salts were
accumulating in the soil because no leaching occurred. Applications of
gypsum and heavy applications of organic matter increased infiltration
rates, but more effective drying of the soil in the early spring before
the hot weather set in was even more effective. The practice of per-
mitting effective drying of the soil between irrigations improved soil
aggregation and infiltration rates. Basin irrigation was required to
obtain adequate applications and penetration of the water.
Where infiltration rates are low, and effective penetration of
water into the soil is a problem, excessive cultivation of the soil
should be avoided, especially when the soil is wet, and the soil should
be allowed to dry periodically to a point where the crop shows visible
stress. Improved soil aggregation is difficult to obtain without the
drying action.
Crop rotation, which includes those that improve soil aggregate
stability or structure, should be practiced where it proves effective
in offsetting the effects of poor water quality. Soils with a poor
physical condition, which may have resulted from an increase in ex-
changeable sodium, are sticky and plastic when wet. They develop
large cracks with very hard clods when they dry. Often it is very
difficult to achieve satisfactory germination of seeds in such soils,
and cultivation must be very timely to prevent detrimental results.
A change to sprinkler irrigation, with a low application rate, may
prove effective in decreasing the physical degradation of the soil
caused by saturating the soil during flood irrigation.
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33
THE QUALITY PROBLEM
Scope and Magnitude
In one sense, the scope of the problem of return flow and
degradation of water quality from irrigation is as large as the
scope of irrigation itself. All irrigation water contains dissolved
minerals (salts). When applied to soils, some of these salts will
accumulate in the soil unless leached from it by excess irrigation
water or by natural precipitation. A permanent productive agricul-
ture under irrigation is basically dependent upon a salt balance in
the root zone of the crops grown (12, 13, 14, 15, 21, 22).
The concentration of the salt in the soil solution will usually
be in the range of four to 10 times the concentration of the irriga-
tion water; hence, the solution draining from the soil profile is
usually much higher in salt content than the water applied. Where
the drainage from the root zone is impeded by a high water table,
the concentration of the soil solution may be 40 to 80 times the
concentration of the irrigation water (21).
Fortunately, the concentration of salt in many irrigation
waters is so low that the leachate under normal irrigation practice
is much less concentrated than theoretically permissible, and when
returned to the stream, or the groundwater body, the effect on the
quality of the resulting water is often negligible. The scope of the
problem of return flow is, therefore, limited from a practicable
standpoint to those areas and conditions where water quality be-
comes so degraded that further use of the water constitutes a
nuisance or hazard.
Acreage affected by salinity
Irrigated soils are scattered throughout most of the United
States. The major areas are in the seventeen western states.
Many of the irrigated soils contain enough salt to be classed as
saline or have enough exchangeable sodium to be sodic. An esti-
mate of acreage of salt-affected soils is given in Table 1. Califor-
nia, with the greatest acreage of irrigation land, also has the most
acreage affected by salt. From such soils may come the increase
in salt in the return flow, over and above the concentrating effect
of evapotranspiration.
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Table 1. Status and extent of saline and sodic areas in the seventeen western states and Hawaii I960.
State
Arizona
California
Colorado
Hawaii
Idaho
Kansas
Montana
Nebraska
Nevada
New Mexico
North Dakota
Oklahoma
Oregon
South Dakota
Texas
Utah
Washington
Wyoming
TOTAL
Unpublished
Irrigable
3Arable
Area reported
Statewide
Statewide
Statewide
7 areas
Total
acreage2
1,565, 000
11, 500, 000
2, 811,532
117,418
All but 3 counties 1, 880, 063
Statewide
4 areas
Statewide
Statewide
Statewide
6 areas
Statewide
Statewide
Statewide
4 areas
7 areas
23 counties and
Columbia Basin
Statewide
data from the U. S
421, 545
1,242,7283
1,218,385
1, 121,916
850,000
2, 636, 5003
826,650
1,490,394
1,697,974
2,198,950
1,390,222
the 2,221,484
1,261, 132
36,451,893
. Salinity Laboratory
Salt-free
Acres
1, 166, 170
7, 755,049
1, 829, 704
71,868
1, 627, 118
319,215
1, 045, 057
928, 385
646, 316
659, 000
1,819,870
632, 900
1, 387, 033
501, 708
1,923,096
877,440
1,955,230
981,429
26, 126,588
%
74.5
67.4
65.1
61.2
86. 5
75.7
84. 1
76.2
57.6
77.5
69.0
76.6
93.1
29.5
87.5
61.1
88. 0
77.8
71.6
Saline-all classes
Acres
398. 830
3, 744, 951
981,828
45,550
252, 945
102,330
197, 671
290, 000
475,600
191, 000
816, 630
193,750
103, 36l
1, 196,266
275,854
512,782
266,254
279, 703
10, 325, 305
%
25.5
32. 6
34. 9
38.8
13.5
24. 3
15.9
23.8
42.4
22.5
31. 0
23.4
6.9
70.5
12.5
36. 9
12. 0
22.2
28.4
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35
Areas adversely affected by return flow
Areas most adversely affected by irrigation return flow are
those in the lower reaches of the larger river systems of the south-
western United States: in the lower basin of the Colorado River, the
Gila and Salt Rivers of Arizona, the Rio Grande in New Mexico and
Texas, the San Joaquin River in California, and similar streams.
In all of these river basins there is a progressive deterioration in
water quality as it flows downstream. In many instances, quality of
water in the headwater tributaries is excellent: low in total dissol-
ved solids, and usually with low sodium to calcium ratios. As the
total concentration of salts increases downstream, there is also a
gradual increase in the sodium percentage due to precipitation of
low solubility calcium salts in the soil and sometimes because of
cation exchange reactions. It is not, however, until the total salt
concentration, and/or the sodium percentage, reaches a level where
management of the soil, or loss of productivity, becomes a problem
that much thought is given to the problem of degradation of water
quality as a result of return flow. More commonly, the problems
associated with drainage and with maintaining a favorable salt bal-
ance in irrigated areas have been given the most attention, but not
always before the effects of water logging and salinity have become
acute in the lower portions of the irrigated area. In some locations,
natural drainage of the irrigated lands has become adequate; the
groundwater table has remained, well below the ground surface, and
the leachate has moved vertically through the soil profile to the
groundwater body, thence laterally toward the stream channel where
it augments the stream flow and usually degrades the quality.
The greatest effect on quality is during the periods of low
flow in the streams. As the water resources are more fully devel-
oped, and upstream reservoirs are constructed to even out the flow
of the streams, there is a stabilizing effect on fluctuations in salinity
of the waters. For example, before construction of Hoover Dam on
the Colorado River, there •were wide fluctuations in both stream flow
and water quality in the lower reaches of the river. Now, with
storage at Flaming Gorge Reservoir, Lake Powell, Lake Mead and
on tributary streams in Colorado and New Mexico, the flow has been
regulated to meet the demand, and the quality stabilized to a salinity
level somewhat above the weighted mean value prior to development,
but well below the levels reached during the late summer before the
construction of Hoover Dam. Hill (23) has estimated that the salt
concentration of the Colorado River on Lake Havasu, which averaged
about 10.75 milliequivalents per liter (me/1) for the 1940-1960
period, may increase to about 15 me/1 with full development of the
upper basin.
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36
In other areas, such as the Salt River Valley in Arizona, the
San Joaquin Valley of California, and the high plains area of Texas
and New Mexico, only a small part of the leachate from the irrigated
lands has rejoined the river systems. Most of it has rejoined the
underlying groundwater body. Because of the large storage capacity
of some of the underground reservoirs, and the kind of geologic
formations present, the effects of this natural downward drainage
of the leachate has been hardly noticeable on changes in groundwater
quality. In other areas, however, where the underground storage
capacity is limited, and/or the salinity of the groundwater has been
higher, the recirculation of groundwater has rapidly increased the
salinity of the water (24). In many areas, where groundwater has
been of good to fair quality, there is a lack of long-time records
from which the magnitude of changes in groundwater quality can be
assessed.
Salt balance and quantities of salt involved
To illustrate the magnitude of the problems of salinity of
irrigation waters, of salt balance, and of drainage requirements
of irrigated areas, one can cite data for the Imperial Irrigation
District in southern California, where records have been kept since
1944 (25). Imperial Valley was a barren desert in 1900. With the
construction of the diversion works on the Colorado River in 1901,
water -was first brought into the valley. In 1905 the headworks on
the Colorado River were washed away by a large flood, and the
river flowed uncontrolled into the valley for two years before being
brought under control. This flood formed the Alamo and New
Rivers, and the Salton Sea.
Problems of silt and salt plagued the valley for many years.
The silt problem diminished with the completion of Hoover Dam in
1936, but the salinity and drainage problems continued to increase.
In 1940, the U. S. Soil Conservation Service began an investigation
of drainage and salinity problems. A salt balance study was under-
taken in 1943 when about 500 miles of subsurface tile lines had been
installed, supplementing more than 1, 000 miles of open collector
drains. As the number of tiled acres increased, the salt balance
improved as indicated in Table 2.
These data indicate that during the 24-year period a total of
more than 46 million tons more salt left the area than came in with
the irrigation water. In this instance the return flow of saline water
was not detrimental to downstream areas, as there were no diver-
sions of this water for irrigation or other purposes. All of it
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37
entered the Salton Sea, where the water evaporates.
Table 2. Drainage and salt balance in the Imperial Irrigation
District1 (25).
Year
1943
1947
1949
1953
1957
1961
1963
1966
1966 (exclud-
Tile drainage
total installed
miles
536
1,109
1,959
4,242
6,340
9,029
10,405
12,662
acres
_
53,640
92, 530
177, 150
232,760
286, 634
30.8,248
335,547
Salt balance
inflow
1000 tons
2, 158
2,795
2,653
3, 348
3,789
3, 330
3, 379
3,650
3, 384
outflow
1000 tons
1,999
2,431
2,798
3,758
3,993
3,573
4, 050
4,149
3,921
Net
balance
-159
-364
+ 145
+410
+204
+243
+671
+499
(+537)
ing Mexico)
TOTAL net balance for all 24 years 1943-1966
46,247
Including small amount of water and salt from Mexico
In 1966, Colorado River water entering the district had an
average salt content of about 900 ppm, or 1. 20 tons per acre foot.
The salt balance in terms of constituents for 1966 is given in Table 3.
Table 3 clearly indicates a phenomenon that usually takes
place in an irrigated area. There was precipitation and deposition
of 427, 668 tons of Ca, HCC>3, and 804 ions in the area, and a net
outflow of 944, 594 tons of Na, K, and Cl ions. The composition of
the water changed accordingly as recorded in Table 4.
San Joaquin Valley drainage and salt balance problems
In recent years, major concern has been voiced regarding
problems of drainage, return flow and salt balance in the San
Joaquin Valley of California (26, 27, 28). This valley contains
more than 4. 5 million acres of irrigated land, or more than half
of the total irrigated area of the state. The valley is composed of
two major basins, the Tulare Lake Basin in the southern end, and
the San Joaquin Basin to the north. Tulare Lake Basin does not
-------
38
TableS. Salt balance constituents, 19661 (25).
Ion
Cations;
Ca
Mg
Na+K
Total
Anions:
HCO3
S04
Cl
Total
TOTAL salt
Inflow
tons
403,593
136,264
564,231
1, 104,088
349,625
1, 332, 132
598,785
2,280,542
3,384, 626
Outflow
tons
311,395
156, 024
848, 172
1,315,591
168, 171
1, 178, 116
1,259,483
2,605,725
3, 921,316
Net
tons
-92,198
+19,760
+283,941
+211,503
-181,454
-154,016
+660,653
+325, 183
+536,690
Excluding water and salt from Mexico.
Table 4. Comparative concentration of irrigation and drainage
waters, Imperial Irrigation District, 1966 (25).
Ion
Inflow
Outflow
t/af. me/1
t/af. me/1
Ratio
OutfL o w / Infl o w
t/af. me/1
Cations:
Ca
Mg
Na+K
Total
Anions :
HCO3
so4
Cl
Total
TOTAL salt
SAR2
Class.3
EC-mmhos/25
0. 143
0. 048
0.200
0.392
0. 124
0.473
0.212
0.809
1.201
3.
5.24
2. 06
5.841
13. 141
1.49
7.25
4.40
13. 14
05
C3-S1
1.
30
0.310
0. 155
0. 844
1.309
0. 167
1. 173
1.254
2.594
3.903
7.
11.38
9.38
25. 211
45. 971
2.02
17.95
26.00
45.97
85
2.17
3.23
4.22
3.34
1.35
2.48
5.92
3.21
3.25
2.
2. 17
4.55
4. 321
3.501
1.36
2.48
5.91
3.50
57
C4-S3
4.
30
3.
30
Estimated from total anions.
%odium adsorption ratio.
3U. S. Salinity Laboratory classification.
-------
39
have surface drainage into the San Joaquin Basin, and because of
the lowered ground-water levels due to pumping for irrigation, it has
no subsurface drainage.
A large part of the valley is irrigated from ground-water,
either for the full supply, or to supplement surface water supplies.
In some instances, as in the Turlock and Modesto Irrigation Districts,
the groundwater is pumped primarily as a means of water table
control (drainage), but the pumped water is discharged back into the
irrigation canals and reused. Some years nearly a third of the water
distributed to farmers is from the pumping operations. The balanced
groundwater and surface water development has completely eliminated
the need of other subsurface drainage for most of the irrigated area,
and has provided an economical source of supplemental water supply.
The groundwater quality for most of the area is good, although it
becomes progressively more saline from east to west.
A larger percentage of the Tulare Lake Basin is irrigated
with groundwater, and this has caused an overdraft on ground-
water supplies, estimated at more than two million acre feet per
year. In some places wells are more than 2, 000 feet deep, and
pumping lifts are from 400 to 600 feet (27).
The total groundwater storage capacity of the valley, to a
depth of 200 feet, has been estimated at 93 million acre feet, or
nine times the storage capacity of the existing and proposed surface
reservoirs of the valley. More than half of the water used for
irrigation in the valley is pumped from the groundwater (27). The
total value of agricultural production in the valley in 1963 was
estimated at more than $1. 7 billion with Fresno, Kern, and Tulare
counties ranking 1, 2, and 3 in value of agricultural production in
the United States.
To alleviate the groundwater overdraft, and permit more
complete development of the irrigable area, water has been im-
ported from the Sacramento River Basin through the combined ef-
forts of the U. S. Bureau of Reclamation and the State of California.
The most recent area to be developed is the San Luis Project on
the west side of the valley. The subsoils in this area are less per-
meable, and experience has shown that subsurface drains are
required. Because of the high salt content of this drainage water,
it cannot be returned to the San Joaquin River for disposal to the
San Francisco Bay area, but will have to be transported there by
the proposed San Luis Drain, or by a larger drain, the San Joaquin
Master Drain (21, 26, 28), designed to provide for the eventual
needs of the entire valley. The latest available information (29) is
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40
that the U. S. Bureau of Reclamation is proceeding with construction
of the San Luis Drain, and that the San Joaquin Master Drain will be
deferred.
The San Joaquin Valley drainage investigations (26) indicate
that eventually there will be more than 1. 5 million acres of irrigated
land in need of drainage, and that by the year 2000, the required
drainage outflow will approximate one-half million acre feet per
year. The salt concentration of this drainage outflow is expected
to reach a maximum of about 6, 500 ppm as new irrigated areas are
brought into production, then decrease within a 50-year period to a
level of about 2, 500 ppm. This would indicate that such a master
drain might transport as much as two million tons of salt annually.
This is about half of the total amount of salt estimated to be coming
into the valley annually from all sources (29). Where there is a
large overdraft on the groundwater, as in the Tulare Lake Basin,
and no natural outflow of groundwater, a salt balance may never be
achieved, and as the groundwater in various parts of the area
becomes too salty for further use, the irrigated area may decrease
unless surface supplies of better quality can be substituted, and
adequate drainage provided.
Irrigation water and return flow in
the Yakima Valley, Washington
A comparison of the irrigation water quality and return flow
in the Yakima Valley, Washington, was made by Sylvester and
Seabloom (30). In this instance, the irrigation water had a very
low salt content (EC = 83 (junhos). Analyses were made of the return
flow from seven subsurface (tile) drains, and five open drains near
their exit. The water in these open drains presumably included
drainage water from tile drains and waste water from canals and
field runoff. A condensation of the results of the analyses and con-
version of the units to me/1 is given in Table 5.
An estimate of the water and salt balance for the valley
indicated that the total annual diversion was 6. 6 acre feet per acre,
and the return flow was 4. 0 acre feet per acre, leaving 2. 6 acre
feet per acre as the evapotranspiration. Computed from the average
composition, according to the analyses, the inflow and outflow of
salt from the 385, 280 acres of irrigated land is shown in Table 6.
Tables 5 and 6 are interesting in that they illustrate changes
that occur when irrigated waters have a very low salt content, but
with about the same amount of HCO?" as Ca plus Mg"'"'". In this
-------
41
Table 5. Comparison of irrigation water and drainage water,
Yakima Valley, Washington (30).
A
Constituent
Cations :
Ca
Mg
Na
K
Anions:
HCO,
,5
Cl
S04
NO3
EC jJimhos 3
o
Temperature C
Oxygen, mg/1
pH
COD, mg/11*
Hrdness as CaCO_
3
Turbidity units
Total PO4, mg/1
Coliforms
per 100 ml
.pplied Water1
me /I %
0.50 44
0.41 36
0. 18 16
0.04 4
0.92 86
0.03 3
0.11 10
0. 01 1
83. 0
16.0
10.2
8. 1
7. 0
46.0
37. 0
0. 32
1,070.0
Tile Drains2
me /I %
2.24 40
1.62 29
1.62 29
. 11 2
4.31 78
0. 33 6
0.84 15
0.06 1
420. 0
13.3
6.8
7.7
9.0
186.0
12.0
0. 86
103. 0
Open Drains1
me/1
1.54
0.99
1. 13
. 13
2.76
0.22
0.77
0.03
283.
17.
9.
8.
10.
121.
130.
0.
10,600.
%
41
26
30
3
73
6
20
1
0
9
0
2
0
0
0
83
0
Average for 7 stations,
2Average for 5 stations
3Electrical conductance in ^mhos per cm at 25 C.
Chemical oxygen demand.
-------
42
Table 6. Salt balance, Yakima Valley (30).
Constituent
Cations:
Ca
Mg
Na
K
Anions:
HCO3
Cl
SO4
NO3
TOTALS
Inflow
tons
33,600
16, 900
13, 700
4, 700
190, ooo
3,400
18,200
3, 600
281, 100
Outflow
tons
73, 000
33,400
60,500
7, 800
430, 000
22, 000
65, 000
16, 300
708, 000
Net
tons
+ 39,400
+ 16,500
+ 46,800
+ 3,100
+240, 000
+ 18,600
+ 46,800
+ 12, 700
+426, 900
Ratio
0/1
2. 17
1.97
4.42
1.66
2.26
6.48
3.57
4.53
2.52
instance it is understood, but not mentioned by the authors, that
before the present drainage facilities were installed large areas of
irrigated land were water-logged and saline. Apparently, under
present conditions, the outflow of salts greatly exceeds the inflow.
The effluent from the tile drain is, however, not highly saline and
could be used for irrigation without dilution. The ratio of outflow
to inflow for all ions exceeds the ratio of the inflow of water to the
outflow, which was 1. 65. This situation occurs where lands that
have become saline because of inadequate drainage are being
reclaimed after the construction of such facilities, and where new
lands with soils containing large amounts of soluble minerals are
first brought under irrigation and adequate drainage is provided.
Salt balance and return flow to groundwater basin
Problems of return flow and salt balance for groundwater
basins are very complicated and depend on specific conditions,
so that only a very general discussion appears warranted. As
previously mentioned, reliable data from which the rate of increase
in salinity of the water can be determined, and from which pre-
dictions for the future can be made, are limited. It would appear
that inevitably, in any groundwater basin that is pumped to the
extent that there is no natural subsurface outflow, the water quality
would gradually become degraded by the amount of salt in the re-
charge flow whether from surface or subsurface sources. The rate
of degradation would depend on many factors, such as the capacity
-------
43
of the ground-water reservoir as compared with the annual draft,
the general quality of the ground-water and the depth of the producing
aquifers and presence or absence of confining strata of low per-
meability above the aquifers. The rate of degradation would prob-
ably be exponential with respect to time, rather than linear.
The difficulty in arriving at any generalized rate of increase
in salinity of groundwater is illustrated by Huffman (28 - closure)
who says:
It is difficult to estimate when, on the average,
the groundwater of the southern part of the San
Joaquin Valley will no longer be suitable for use
without being diluted. The unconfined aquifers will
go first. In some places, high concentrations have
already appeared in pumped water and the wells are
now abandoned. . .
The Department has studied the idea of in-
creasing concentrations of salts in the groundwater,
with time, as sampled from key wells. It initiated
its groundwater quality data program in 1952,
although records of groundwater qualities have
been obtained since the mid 1930' s. The large
variability of groundwater quality in the valley
precludes any generalized statement of quality
trends.
fiuffman showed that five of the seven wells reported had
increases in salinity ranging from 1.4 to 9. 6 percent per year.
One well showed an increase from 964 to 2, 050 jjtmhos in a two-
year period, a gain of 46 percent per year. The other well showed
a decrease in salinity from 564 to 490 (amlios in two years, or 7.4
percent per year. No explanation for such a decrease was given.
Water Quality Requirements for Crops
Pollutants in irrigation water can adversely affect crop
growth and quality; they affect the soil, which indirectly affects the
crop, and they affect the consumer of the crop. Some pollutants do
not actually impair growth or impart harmful constituents to the
crop, yet may affect the acceptability of the crop to man or animal.
-------
44
Plant response
Crops may be adversely affected by high concentrations of
salts due to development of abnormally high osmotic pressures in
the soil solution, or by the presence of toxic substances in the soil
water. The crops may be indirectly affected through the influence
of irrigation water on the soil. Such a condition is developed when
the proportion of sodium, in the water is proportionally greater than
calcium plus magnesium and the adsorbed sodium causes dispersion
of the clay fraction of the soil. This results in land that tends to
form surface crusts and is impermeable to air and water.
There are other quality factors that adversely affect plant
growth, such as temperature extremes, nutrient imbalance, and
lack of oxygen induced by oxidizable organic matter in the water.
Osmotic effects
The total concentration of soluble salts is probably the most
significant criterion of irrigation water quality. This is related to
salinity in the soil solution, which is further concentrated by evapo-
ration and transpiration. Plant growth may be seriously reduced or
even prevented because the salts increase the osmotic pressure of
the soil solution, making it difficult for plants to obtain water, thus
inducing physiological drought.
Electrical conductivities of the water or soil solutions are
directly correlated with osmotic pressures. For this reason easily
determined conductivity measurements can be substituted for tedious
osmotic concentration measurements when determining the salt
content of soil or water. Conductivity is usually expressed as
millimhos per centimeter for soil solutions and as micromhos per
centimeter for water.
Phyotoxic substances
Many substances can occur in irrigation waters in concen-
trations which cause direct toxic damage to plants. Included are
boron compounds and chlorides, which occur in natural waters and
trace elements, heavy metals, and pesticides which are artificially
applied or washed out of the atmosphere. Plant pesticides may be
spread by irrigation, especially by sprinkler irrigation. Chlorides
are not particularly toxic to most crops, but certain crops, such as
citrus, stone fruits, and almonds, are sensitive. Chloride damage
-------
45
often may not be distinguished from osmotic effects. Damage to
plants can result from absorption of chlorides from salty water
applied through a sprinkler system. High concentration of bicar-
bonate ions may induce iron chlorosis in sensitive plants. Toler-
ance limits are difficult to establish because calcium salts in the
water will reduce bicarbonate ion concentration by the precipitation
of calcium carbonate. Considerable information is available on the
levels of concentration of boron which will be toxic to different
plants. In contrast, very little is known about the levels of other
substances harmful to different crops or the mode of damage, and,
therefore, establishment of meaningful tolerance limits of the
different materials for the different plant species is difficult. The
amount of pollutants in the soil may be more critical than the amount
in the water.
Nutritional imbalance
Most crops require a relatively well balanced nutrient con-
tent in the soil solution. Salty irrigation water may significantly
upset the balance if the composition and concentration are unfavor-
able. High concentrations of sodium salts may cause a deficiency
in calcium and magnesium. High proportions of calcium salts in
the water may prevent plants from obtaining enough potassium.
The effect of different salts and varying concentrations on the
magnitude of nutritional imbalance induced is difficult to evaluate.
Except for a few sensitive crops, or with waters of high salinity,
there is no evidence of a serious problem of nutritional imbalance
in irrigation agriculture.
Soil physical properties
The sodium content of irrigation water influences the per-
meability of the soil. Soils with a high percentage of exchangeable
sodium have physical properties generally unfavorable for water
intake, drainage, and plant growth. This condition may be induced
or aggravated when there is an unfavorable ratio of sodium to cal-
cium plus magnesium.in the water. Permeability of the soils,
particularly the clay soils, is reduced because of increased disper-
sion. Such soils tend to puddle easily when wet and form hard crusts
and clods when dry. Waters, although relatively low in total soluble
salt, may induce adverse physical effects due to adsorbed sodium.
Conversely, the salt content may be high enough to cause adverse
osmotic effects with no particular deterioration of the physical
properties.
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46
Presently accepted criteria for irrigation
Differences in water quality for irrigation have been recog-
nized by users of the water and by scientists. Schofield (31) in
1936 established a system for rating waters which ranged from
excellent to unsuitable. A number of later systems have been pro-
posed which were largely empirical. Most of the systems have
recognized the adverse osmotic effects of soluble salts, the unique
effects of sodium on the soil, the direct and indirect effects of
bicarbonate ions, and the specific toxic effects of boron. Current
systems attempt to indicate the effects water will have on the soils
and crops and also recognize pollutants that normally do not occur
in natural waters.
Recently, a National Technical Advisory" Committee to the
Secretary of the Interior (3) reviewed the variously proposed criteria
and classifications. This committee recognized the interacting
effects of soil, climate, and plants. It acknowledged that no set of
criteria could be used to evaluate all water quality characteristics
for irrigation, and suggested guidelines or tolerance limits for
salinity, trace elements, herbicides, and sodium hazard. Some
of these guides are reproduced as Tables 7, 8, 9, and 10. The
committee cautioned that the values suggested should be used in
combination with the discussions in the text of the report. Besides
providing guidelines on maximum permissible levels, Table 10
shows the variety of substances involved and sources of origin of
pesticide materials.
Table 7. Suggested guidelines for salinity in irrigation water (3).
EC1
Crop response TDS mg/1 mmhos/
cm
Water for which no detrimental
effects will usually be noticed <500
Water which can have detrimental
effects on sensitive crops 500-1000
Water that may have adverse effects
on many crops and requiring
careful management practices 1000-2000
Water that can be used for salt-
tolerant plants on permeable soils
with careful management practices 2000-5000
<0.75
0.75-1.50
1.50-3.00
3.00-7.50
1Electrical conductivity.
-------
47
Table 8. Trace element tolerances for irrigation waters (3).
Element
Aluminum
Arsenic
Beryllium
Boron
Cadmium
Chromium
Cobalt
Copper
Fluorine
Iron
Lead
Lithium
Manganese
Molybdenum
Nickel
Selenium
Tin
Tungsten
Vanadium
Zinc
For water used
continuously on all
soils
mg/1
1. 0
1. 0
0.5
0. 75
0. 005
5. 0
0.2
0.2
i
i
5.0
5. 0
2. 0
0. 005
0. 5
0. 05
i
i
10.0
5. 0
For short-term use
on fine textured
soils only
mg/1
20. 0
10. 0
1. 0
2. 0
0. 05
20. 0
10. 0
5.0
i
i
20. 0
5.0
20.0
0.05
2.0
0. 05
i
i
10. 0
10. 0
1See text of original.
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48
Table 9.
Levels of herbicides in irrigation water at which crop
injury has been observed1 (3).
Herbicide
Crop injury threshold in
irrigation water mg/1
Acrolein
Aromatic solvents
(xylene)
Copper sulfate
Amitrole-T
Dalapon
Dequat
Endothall Na and K
salts
Dimethylamines
2,4-D
Dichlobenil
Fenac
Picloram
Flood or furrow: beans-60, corn-60,
cotton-80, soybeans-20, sugar
beets-60.
Sprinkler: corn-60, soybeans-15,
sugar beets-15.
Alfalfa->1, 600, beans-1,200, carrots-
1,600, corn-3, 000, cotton-1, 600,
grain sorghum->800, oats-2,400,
potatoes-1, 300, wheat- >1, 200.
Apparently, above concentrations used
for weed control.
Beets (rutabaga)->3. 5, corn->3. 5.
Beets->7. 0, corn-< 0. 35.
Beans-5.0, corn 125.0.
Corn-25, field beans-< 1. 0, alfalfa-
>10. 0.
Corn->25, soybeans->25, sugar beets-
25.
Field beans->3. 5< 10, grapes-0. 7-1. 5,
sugar beets-3. 5.
Alfalfa-10, corn->10, soybeans-1. 0,
sugar beets-1. 0-10.
Alfalfa-1.0, corn-10, soybeans-0. 1,
sugar beets-0. 1-10.
Corn->10, field beans-0. 1, sugar beets-
< 1. 0.
lData submitted by crops research division, ARS, USDA (unpublished).
Note: Where the symbol ">" is used, the concentrations in water
cause no injury. Data are for furrow irrigation unless otherwise
specified.
-------
Table 10. Levels of herbicides in irrigation waters (3).
49
Herbicide
Ac role in
Aromatic •olvent*
(xylene).
Copper *ulfate
Amitrol-T
Dalapon
Diquat
Diuron
Monuron
Eodothal Na and
K aalt*.
Dim ethylamine a
2.4-O
Silvex
Dichlobenll
Fenac
Pichloram
Site of u.e
In water from cylinder
under nitrogen gaa
pressure.
EmuUifi.d in flowing
water.
In flowing water canal*
On bank weed* along
Irrigation canal*
and on cattail in
drain canal*.
do
face of canal* and
re*ervoir*.
On bottom* and bank*
of iinalL canal*
when no water la
in canaL
Same a* for diuron
In pond* and reaer-
voir* moitly in
Eastern State*.
In water control canal*
in Florida. Promia
ing uae in weatern
cftnala.
Weed* along canal
bank*.
Floating and emeraed
weed* in aouthern
canal*.
Phreatophytea on
floodwaya, along
canal*, reaervoir*,
and *t ream*.
Floating and emeried
weeda in southern
waterway*.
Promising bottom
treatment* In
canal* without
water.
Same a* dichlobenll
For control of bruih
and weeda on
watershed area*.
'Data aubmitted by F. L. Tlmmoa*. Crop*
aion, ARS. USDA (unpublished).
Type of Treatment
formulation rate
• Soluble liquid IS mg/lX4
hour*.
0.6 mg/lXB
hour*.
0. 1 mg/lX46
liquid. 30-60 mini-
mum (300-
750 mg/1).
Coarie penta- 0.5 to 3.0 mg/1
hydrate (contlnuou* ).
cryital*. 1/3 to 1 lb/cf*
(•lug).
Foliage *pray 6 to 16 Ib/A
Liquid 3.5 mg/1 or
1-1.5 Ib/A.
Wettable powder 64 Ib/A
suspension
eprayed
Same aa for 64 Ib/A
dluroa.
Liquid or 1-4 mg/1
granule.
ally aa amini
do do
Liquid *pray a* 2 to 4 Ib/A
e*ter.
Liquid ipray 2 to 8 Ib/A
over surface.
table powder
a pray.
Same aa dichle- 10 to 20 Ib/A
bonll.
Liquid spray or 1 to 3 Ib/A
granule*.
Protection Branch, Crops Research Divi-
•11 heroic Idea except when sprinkler Irriga-
Likely concentration in Crop Injury threshold
irrigation water in irrigation water
reaching crop or field (mg/1)2
10 to 0. 1 mg/1 Flood or furrow:
cotton-80, foy-
beans-20, sugar
beet*. 60.
beet*. IS.
0.05 to 0. 1 mg/1
1.200. carrot* -
1,600. corn-3,000.
•orghum->800,
oat.-Z.400, pota-
toe.-l, 300. wheat-
>1,200.
9. 0 to 0. 08 mg/1 for weed control.
in 10 to 20 mile*.
Uiually le.i than Beet* 3.5. corn->3.5.
0.5 mg/1. 3 <0. 35.
0.1 mg/1.
Below crop injury No data
threshold.
do do
ing period.
and K salt*. >25, *ugar beeta-
25
B. 2 to 10 mile* < 10.
below treat- Crape*-0. 7-1. 5.
ment.
0. 1 mg/1 or les* to Sugar beeU-3.5
none in 3 weeks.
No data. Probably No data
le** than 0. 1
mg/1.
From 10 to 1.600 do
ug/1, 1 day after
application. 1 to
70|iB/l. 5 weeka
after treatment.
Alfalfa -10. corn->10,
beets -1.0 to 10.
0.66 to 1.8 mg/1 Alfalfa. t.O. corn- 10,
below treated aoybeana-0. 1,
area. 0.007 to *ugar beet*-0. 1 to
0. 100 mg/1 10.
2 hour* later.
No data Com->10. field bean. -
0. I. sugar neet*-
< 1.0.
Remark*
Canal* up to 200 cf* con-
mile*.
minimum in 20 to 30
mile*.
Canal* 1, 000 cfi and larger
in 30 to SO mile*.
idly from point of applica-
tion within 2 to fa mile*
6 to 10 miles.
rapidly with distance from
tlug application*.
but actually u*ed for con-
trol of bank weeds along
control of submersed
Do not u*e for 10 day*.
Ration systems.
Used mostly in .mall larm
ditches with intermittent
water How.
(ir*t water through canal
for irrigation.
for irrigation or domcn*tic
purposes.
pending on concentration)
after treatment before us-
ing water.
not contaminate water to
b« used for irrigation.
A minimum waiting period of
3 weeka before uaing
tion.
Silvex registered only for
control of aquatic weeds
in noaflowing water at
4 Lb/100 gallons of water.
do not use In water to be
domestic purposes.
Registered for control of sub-
ponda, and drainage
domestic purposes.
Same as dichlobenil.
Civet excellent control of
Canada thistle and other
canals hazardous.
either temporary or permanent injury. Often thi* concentration did not cauie final
reduction in crop yield or quality.
tion i* Indicated for acroleln. Threihold of injury la loweit concentration that cau*cd
-------
50
Proposed changes in criteria
Current research is being directed toward relating the
quality of water to specific crop and soil conditions and for different
methods of application as well as amounts of water required. Much
is known regarding salinity and its effects on soils and plants. In
contrast, there is a paucity of knowledge of the effects of trace
elements and heavy metals in irrigation water on growth and quality
of plants. Little is known about the effects of organics having a
biochemical oxygen demand (BOD) and other pollutants in irrigation
water. Until more information is available, little can be done to
improve on the guidelines and refinements of criteria now available.
Weed seeds in drainage water, particularly water to be
reused for irrigation, should be classed as a pollutant and some
criteria established for evaluation. Most other additions and
changes in criteria will likely come gradually as the necessary
research information becomes available.
Nature of Pollutants Involved
The quality of irrigation water and return flow is largely
determined by the amount and nature of the dissolved and suspended
materials they contain. In natural waters, the materials are largely
dissolved inorganic salts leached from rocks and minerals of the
soils through which the water passes. Use and reuse of water for
irrigation and industry concentrates these salts and adds additional
kinds and amounts of pollutants. Many insecticides, fungicides,
bactericides, herbicides, nematocides, as well as plant hormones,
detergents, salts of heavy metals, and many organic compounds,
render water less fit for irrigation and other uses.
Salinity, hardness, and plant nutrients
The greater portion of the dissolved solids in most natural
waters used for irrigation are sodium, potassium, calcium, and
magnesium sulfates, chlorides, carbonates, and bicarbonates.
There are wide variations in concentration and proportion of these
salts, as indicated in Table 11 (32). The relative prevalence of the
different kinds of salts in the streams of the United States is indi-
cated in Figure 4.
Hardness is a significant quality characteristic of waters to
be used for domestic or industrial purpose. Ordinarily hardness is
-------
Table 11. Chemical analysis of important streams from which water is diverted for irrigation (32).
No.
1
2
3
4
5
6
7
8
9
10
11
12
Stream
Yakima '
Sacramento 2
Columbia 3
Yellowstone *
North Platte s
Cache Creek6
San Joaquin*
Arkansas '
Rio Grande '
Colorado 10
GUa"
Pecos I2
Conductance _
(KxlO5 B°'°n
at 25° C) Ppm
11.
15.
15.
19.
28.
50.
76.
93.
112
117
133
542
7
0
1
1
0
8
4
3
0.02
0.05
0.05
0.06
0.03
1.78
0. 18
0.08
0.20
0. 16
0.20
0.37
Percent TT
.. pH
sodium
23
18
13
29
22
32
52
25
50
39
60
40
7.6
7.9
7.0
7.5
7.5
-
7.0
8.2
8.3
7.8
-
-
Silica
ppm
19
25
-
-
15
-
19
22
41
-
15
22
Calcium
epm
0.56
0.63
0.90
0.89
1.61
1.31
1.79
5.06
4. 14
5.06
3.39
25.06
Magne-
sium
epm
0.35
0.51
0.39
0.59
0.57
2.40
1.58
2.66
1.49
2.30
1.59
12.66
Sodium
epm
0.28
0.26
0.19
0.61
0.63
1.77
3.84.
2.63
5.77
4.70
7.75
25.79
Potas-
sium
epm
0. 04
0. 04
-
0
0.07
-
0. 16
0.21
0.21
-
0.25
0.61
Total
Cations
epm
1.23
1.44
1.48
2.09
2.88
5.48
7.37
10.56
11.61
12.06
12.98
64. 12
Car-
bonate
epm
0
0
0
0
0
0.40
0
0.05
0.25
tr
0. 30
-
Bicar-
bonate
epm
1.00
1.22
1.26
1. 18
1.59
3.37
2.50
2.70
3. 33
2. 52
2.75
1.34
Sulfate
epm
0.07
0. 13
0.21
0.52
1. 12
0.61
3.90
7. 39
4.97
7. 16
2.29
35.64
Chloride
epm
0. 15
0. 12
0.07
0. 10
0.09
1.05
1.04
0.47
3.02
2.30
7.07
26. 79
Nitrate
epm
tr
tr
tr
0.03
0.03
tr
0.04
tr
0. 03
0. 03
0. 01
0
Total
Anions
epm
1.22
1.47
1.54
1.83
2. 83
5.43
7.48
10. bO
11.60
12.01
12.42
63.77
* Yakima River from main canal on Sunnyside Project; composite sample for August, 1943.
2Sacramento River at Tisdale, approximately 35 miles above Sacramento, July 13, 1945.
'Columbia River at Wenatchee, Washington, November 25, 1935.
'Yellowstone River from canal at Huntley, Montana, June 7, 1940.
'North Platte River from canal near Scotts Bluff, Nebraska, May 23, 1945.
"Cache Creek at Capay Dam, Yolo County, California; composite sample for August, 1941.
7 San Joaquin River near Vernalis, California, August 10, 1933.
"Arkansas River at point of diversion of Rocky Ford High Line Canal, Pueblo County, Colorado, July 21, 1944.
'Rio Grande at El Paso, Texas; composite sample for August, 1945.
"Colorado River at Yuma, Arizona; composite sample for August 1-10, 1942.
"Gila River at Ashurst-Hayden Dam, Arizona, August 2, 1933.
12Pecos River near Orla, Texas, 19 miles downstream from Red Bluff Dam; composite sample for August 1-10, 1943. Analysis by U. S. Geological
Survey (Water-Supply Paper 970, p. 70).
-------
Calcium and magnesium salts
Sodium potassittm
Solfat* and chl«ride
Sodium and potassium
Carbeoat* and bicarbonate
Figur* 4. Pr«r«l«at typ«« of salts in rir«r waters (drawn from
USGS Atlas HA-61)(7).
-------
53
considered as the capacity to neutralize or precipitate soap. In
irrigation waters, hardness is usually attributed to calcium and
magnesium. Ions of iron, copper, barium, etc. , are also respon-
sible for hardness. It is expressed in terms of ppm calcium
carbonate equivalent. Hardness is likely to be increased through
the use of water for irrigation. Eldredge (33) indicates that usually
a hardness of 75-150 ppm in water does not interfere with its use
for most domestic purposes. Hardness of 150 ppm is marginal,
and if above 200 ppm water usually should be softened. Hardness
induced by calcium and magensium reduces the harmful effects of
exchangeable sodium in soils.
Plant nutrients of major concern in irrigation waters are
nitrogen in the form of nitrate and phosphorus as soluble phosphate.
Usually the amounts of these nutrients in irrigation water will have
little or no adverse effect on crops or soils. The harmful effects
are reflected by the stimulation of growth of aquatic plants in lakes
and in storage reservoirs and in conveyance canals and drains.
Compounds of nitrogen and phosphorus have adverse effects when in
water intended for uses other than for irrigation. An example is
the toxic effect of nitrate consumed by infants. The quantity in
most natural water is usually very low and an appreciable quantity
generally indicates pollution. Evidence indicates that vigorous
algae growth can be expected if water contains 0. 1 mg/1 phosphorus
and that levels must be below 0. 02 mg/1, if growth is to be com-
pletely inhibited (34).
Phytotoxic elements
Many substances appear in water at low concentrations and
have specific adverse effects on plants. Boron is an example. It
occurs in toxic concentrations in certain natural irrigation water
and is introduced as a pollutant from many sources. Crop plants
differ in their tolerance to boron, as indicated in Table 12 (35).
When excess boron occurs in the water, tolerant crops may still be
grown while sensitive crops could not. Boron does not leach from
the soil as readily as do many other salts (36).
Many substances such as trace elements and/or heavy metals
that are not in natural waters in toxic concentrations, are introduced
as pollutants and may be harmful to plants and animals. Some crops
are particularly sensitive to sodium and chloride ions and the ad-
verse effect is due to specific toxicity rather than to increased
osmotic pressure. A list of many of the known pollutants and their
mode of actions is given in Table 13 (37).
-------
54
Table 12. Relative tolerance of plants to boron in irrigation water (35).
Tolerant
Semitolerant
Sensitive
4. 0 ppm of boron
2. 0 ppm of boron
1. 0 ppm of boron
Athel (Tamarix aphylla)
Asparagus (Asparagus
officinalis)
Palm (Phoenix
canariensis
Date palm (Phoenix
dactylifera)
Sugar beet (Beta vulgaris)
Mangel (Beta vulgaris)
Garden beet (Beta
vulgaris
Alfalfa (Medicago
sativa)
Gladiolus (Gladiolus spp. )
Broadbean (Vicia faba)
Onion (Allium cepa)
Turnip (Brassica rapa)
Cabbage (Brassica oleracea
var. capitata)
Lettus (Lactuca sativa)
Carrot (Daucus carota)
2. 0 ppm of boron
Sunflower (native)
(Helianthus annuus)
Potato (Solanum
tuberosum)
Cotton (Acala and Pima)
(Gossypium spp. )
Tomato (Lycopersi cum
esculentum
Sweetpea (Lathyrus
odoratus)
Radish (Raphanus sativus)
Field pea (Pisum sativum)
Ragged-robin rose (Rosa)
Olive (Olea europaea)
Barley (Hordeum vulgare)
Wheat (Triticum vulgare)
Corn (Zea mays)
Milo (Sorghum vulgare)
Oat (Avena sativa)
Zinnia (Zinnia elegans)
Pumpkin (Cucurbita pepo)
Bell pepper (Capsicum
frutescens)
Sweet potato (Ipomoea
batatas)
Lima bean (Phaseolus
lunatus)
1. 0 ppm of boron
Pecan (Carya pecan)
Walnut (black and Persian or
English)) Juglans spp. )
Jerusalem artichoke
(Helianthus tuberosus)
Navy bean (Phaseolus
vulgaris)
American elm (Ulmus
americana)
Plum (Prunus domestica)
Pear (Pyrus communis)
Apple (Pyrus malus)
Grape (Sultanina and Malaga)
(Vitis vinifera)
Kadota fig (Ficus carica)
Persimmon (Diospyros spp. )
Cherry (Prunus avium)
Peach (Prunus persica)
Apricot (Prunus armeniaca)
Thornless blackberry
(Rubus spp. )
Orange (Citrus sinensis)
Avocado (Persea americana)
Grapefruit (Citrus paradisi)
0. 3 ppm of boron
-------
55
Table 13. Potential pollutants with indication of degree of toxicity and mode of action (37).
Material
Acids. Sulfuric, hydrochloric, nitric, acetic, and hydrogen sulfide.
Beneficial to alkali soils. Excessive acidification of some soils
might bring into solution toxic substances such as heavy metals
Barium. Would be precipitated from most natural waters
Beet-Sugar wastes
Calcium. Desirable in reasonable concentrations
Calcium Chloride. Tox' to some stone fruits
Chloride. Toxic to some plants
Dissolved Solids. 90 percent of all irrigation waters contain less than
2, 000 ppm
Magnesium. Desirable in reasonable concentration
Nitrate. A fertilizer and beneficial in moderate concentration, toxic
to some plants at higher concentration
Phosphate. A fertilizer and beneficial in reasonable concentration.
Precipitated from most irrigation waters
Potassium. A fertilizer and beneficial in small amounts
Sulfate
Alkalinity. May be beneficial in small amounts for acid soils
Ammonium Salts. Soil impairment not as pronounced as with sodium
salts. Beneficial as a. fertilizer in reasonable quantity
Bicarbonate. In addition to soil impairment it may cause a
"bicarbonate-induced chlorosis" on some plants
Fluoride. May precipitate as CaF2 causing calcium deficiency or
soil impairment
Sodium Salts. Soil impairment is the principal hazard, although
sodium is moderately toxic to some plants
Sodium Carbonate
Aluminum. Less toxic in alkali soil or in alkaline solution
Arsenic. Less toxic in alkaline solution. Can accumulate in soil
to toxic levels
Beryllium. Less toxic in alkali soil or in alkaline solution
Boron Compounds
Cadmium. Less toxic in alkali soil or in alkaline solution
Chemical Warfare Agents
Chlorine. No toxic effect at concentration below 50 ppm
Chromium. Less toxic in alkali soil or in alkaline solution
Cobalt. Less toxic in alkali soil or in alkaline solution
Copper. Less toxic in alkali soil or in alkaline solution
Gallium
Halogenated Hydrocarbons. Might impart objectional flavors or odors;
weed killers, DDT, Lindane, BHC, Chlordane, Gammexane,
Benoclor
Indium
Iron. Less toxic in alkali soil or in alkaline solution
Lead. Less toxic in alkali soil or in alkaline solution
Lithium
Manganese. Less toxic in alkali soil or in alkaline solution
Molybdenum. Less toxic in acid soil or in acid solution. Accumulates
in plant tissue; forage toxic to animals
Nickel. Less toxic in alkali soil or in alkaline solution
Nitrite
Oil, Petroleum
Palladium. Toxic "at comparatively low concentrations"
Rubidium
Selenium. Accumulates in plant tissue; forage toxic to animals
Sodium Carbonate. Also impairs soil
Sodium Chloride. Also impairs soil
Strontium
Tellurium. "Low concentration of B^jTeOj in culture solution
reduced growth"
Thorium
Tin. Less toxic in alkali soil or in alkaline solution
Titanium
Zinc
Degree of
Toxicity '
S to N
S
S to N
S to N
S to N
S
S to N
S to N
S to N
N
S to N
S to N
M
S
S
M
S
S
Ex
Ex
M
Ex
S
Ex
S
M
Ex
Ex
Ex
M to S
Ex
S
S
Ex
Ex
M
Ex
M
S
. . .
S to N
M
M
S to N
S
. . .
S
M
S to N
M
Mode of
Action 2
Os
Os
Os
Os
Os
Os to Tox
Os
Os
Os
Os
Os
Os
Soil
Soil
Soil
Soil
Soil
Soil
Tox
Tox
Tox
Tox
Tox
Tox
Tox
Tox
Tox
Tox
Tox
Tox
Tox
Tox
Tox
Tox
Tox
Tox
Tox
Tox
Tox
Tox
Tox
Tox
Tox
Os to Tox
Tox
Tox
Tox
Tox
Tox
Tox
'Ex, estreme toxicity; M, moderate; S. slight; N, nontoxic.
'Mode of action; Oi, osmotic; S, soil impairment; Tox, phytotoxic.
-------
56
Pesticides
Bactericides, fungicides, insecticides, nematocides, roden-
ticides, and herbicides as a group of pesticides include both organic
and inorganic compounds that can pollute soils or water. These can
be classed in four broad groups:
(a) Halogenated hydrocarbons are compounds of carbon
hydrogen and chlorine, or bromine used as insecticides or herbicides.
They are used in the largest quantities and are likely to be found
most in the soil. Some of the common named products are: endrin,
toxaphene, dieldrin, aldrin, DDT, methoxychlor, heptachlor, lindane,
chlordane, and BHC.
(b) Qrganophosphates are compounds of carbon, hydrogen,
oxygen, and phosphorus. Most are readily decomposed in the soil
or water and serve as a source of phosphorus pollution. In common
use are: EPN, para-oxon, TEPP, parathion, chlorothion, systox,
methyl parathion, malathion, dipterex, and OMPA.
(c) Other organics include such compounds as carbamates,
phenoxys, thocynates, substituted ureas, triazines, organic mer-
curials, and nicotine.
(d) Inorganics include such compounds as lead and calcium
arsenate and copper sulfate.
Sediments and turbidity
Sediments are as variable as the soils from which they are
derived. Suspended solids in water can affect the use of water in
many ways. In surface irrigation, the solids can interfere with flow
in conveyance systems and structures. Deposits can reduce the
capacity of reservoirs and distribution systems. Suspended minerals
may cause undue wear on sprinkler nozzles and pumps, clog screens,
and adversely affect water for most domestic and industrial uses.
Sediments may be relatively large mineral particles that tend to
settle out of suspension or fine colloids that remain in suspension.
Algae growth can cause turbidity in water. Heavy metals and many
pesticides are absorbed by organic and mineral soil particles,
transported while adsorbed on soil particles, and contaminate sur-
face waters as a result of erosion (38).
-------
57
Organic matter, taste, odor, and color
Taste, odor, and color are of little concern in the use of
water for irrigation. The prime objections are raised by other
users and they vary with the nature of the compounds responsible
for the objectionable characteristics. Biodegradable organic matter
is of concern to most water users. Soil aeration and availability of
oxygen is usually no problem in well structured soils. Where drain-
age is poor, the oxygen supply may be limited. Waters containing
organics with high BOD aggravate soil aeration and availability of
oxygen in the soil. Organics with a wide carbon-nitrogen ratio
could also induce a deficiency of nitrogen in a growing crop.
.Decomposing organic matter causes objectionable taste, odor, and
color. Pesticides in the water can kill fish and plants, resulting
in disagreeable odors and tastes. Some pesticides impart disagree-
able odors and tastes directly due to the materials themselves.
Thermal pollution by irrigation
Relatively nothing is known concerning the temperature
changes that might take place in return flow waters between their
point of diversion and subsequent return to the supply system. Irri-
gation is applied under a wide range of temperature conditions
involving water temperature, soil temperature, and air temperature.
Late fall and winter irrigations might have a general cooling effect
on the total return flow, depending upon the lag time between the
diversion and return. On the other hand, summer irrigations on
hot soils might produce warmer return flows. The cooling effect
produced by the "latent heat of vaporization" for all water transpired
or evaporated may be significant under certain conditions. Depend-
ing upon the initial temperature (soil, water, and air), the thermal
pollution could be either positive or negative. Relatively hot waters
produced in cooling requirements of industry would probably be
cooled substantially if used for irrigation. The general thermal
pollution effect of irrigation on the return flow portion is believed
to be of a moderating type with the irrigation process being either
a positive or negative contributor of heat, depending upon initial
conditions.
A substantial increase in the temperature that would adversely
affect the water for future use can be considered as thermal pollution.
The major effect of thermal pollution seems to be on cooling water
and on aquatic life in streams and reservoirs.
-------
59
SOURCES AND DETECTION OF POLLUTANTS
Sources of Pollutants in Irrigation
Water and Return Flow
Pollutants in irrigation or drainage waters come from many
sources before, during, and after irrigation. They come from
animals, soils, both irrigated and non-irrigated, fertilizers and
amendments, pesticides, as well as from industrial and municipal
wastes. Some pollution is natural, such as from mineral springs,
lightning, fixed nitrogen, etc. An example of the diverse contribu-
tions to salinity increase in the Colorado River is given in Table 14.
Soil derived
As irrigation and rain water percolate through the soil mantle,
the soluble mineral constituents of weathered rocks are dissolved and
move with the water. Some salts may have been transported to the
soil and accumulated where the water was consumed, or they may
have been released from •weathering of rocks and minerals. Soils
containing considerable gypsum will contribute soluble calcium sulfate
for an extended period as indicated by Doneen (36), except where
saline soil is being leached. Most of the salt in drainage water from
irrigated fields was at one time or another in the irrigation water.
Where drainage is established and salty soils are leached, the salt
load in the drainage water will be much greater than in the irrigation
water, and there will be a favorable salt balance for the area and a
greater than normal concentration in the return flow. This was shown
by Bower, Spencer, and Weeks (39) in their salt balance study in the
Coachella Valley, California, Table 15. As the proportion of the
land with tile drainage increased so did the salt removal until there
was a favorable salt balance established. The data undoubtedly indicate
that some saline soils were being reclaimed after drainage was estab-
lished.
The data in Table 16 (39) shows the accompanying changes in
composition of Colorado River water as a result of use in the
Coachella Valley. Most striking is the increase in sodium and the
decrease in calcium and magnesium. The nitrate ion is completely
soluble in the soil solution and generally moves with the soil solution.
Nitrates are formed in soils when organic matter is nitrified by soil
-------
60
Table 14. Incremental salt concentration attributable to specific
sources, Colorado River at Hoover Dam (40) (1942-
1961 period of record adjusted to I960 condition)1.
„ Total dissolved solids
bources ,n
mg/1
Natural Sources
Diffuse Sources 274
Point Sources (mineral springs,
wells, etc. ) 69
Irrigation
Consumption 88
Leaching 165
Municipal and Industrial Sources 10
Water Exports 22
Evaporation and Phreatophytes 97
TOTAL 725
on data from: USGS Professional Paper 441, Water
Resources of the Upper Colorado River Basin, 1965; USDI,
Progress Report No. 3, Quality of Water, Colorado River Basin,
January 1967; FWPCA records on open files.
-------
Table 15. Acres of irrigated and tiled land, and inputs and outputs of water and salt for irrigated
land by years, 1957-1965, Coachella Valley, California (39).
Year
1957
1958
1959
I960
1961
1962
1963
1964
1965
Irrigated
land
52, 329
53,592
55, 527
54,333
53,990
53,443
57, 773
60, 053
59,890
Irrigated
land with
tile drainage
acres
10, 835
14,585
19, H5
22, 285
24,857
27, 071
28, 984
30,686
32, 080
Inputs to irrigated land,
(Colorado River plus wells)
5 Water
Salt
ac-f t
tons /ac -ft tons
299,590
348, 590
358, 641
368, 926
366, 315
389, 877
370, 014
359,989
341, 165
1. 234
.968
. 972
. 987
1. 066
1. 122
1. 058
1. 128
1. 193
369, 655
337, 340
348,543
364,265
390, 522
437, 313
391,459
406, 110
406, 992
Outputs from
irrigated land
Water
Salt
ac -ft
tons/ac-ft tons
32,578
46,467
47, 188
61, 327
75,597
101, 169
110, 627
113, 104
124, 128
3. 065
3. 369
3. 530
3. 721
3.666
3.425
3. 640
3.660
3.423
99, 847
156, 542
166, 553
228,215
277, 169
346, 506
402, 685
413, 978
424, 837
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62
Table 16. Comparison of the composition of Colorado River water
with that of drainage water (39).
Equivalent percentage
of total cations
Ca
Mg
Na
K
Colorado River (Coachella Branch of
Aug.
Mar.
Aug.
Feb.
Aug.
Apr..
Aug.
1963
1964
1964
1965
1965
1966
1966
Ave.
37.
38.
35.
41.
34.
36.
33.
36.
22
49
22
06
50
46
81
68
20.28
20. 73
19.25
13.20
19. 34
18.91
19.07
18.68
41.41
39.23
44.33
43.99
45. 18
43.42
46.09
43.38
1.
1.
1.
1.
*
1.
1.
1.
Coachella Valley
Aug.
Mar.
Aug.
Feb.
Aug.
Apr.
Aug.
1963
1964
1964
1965
1965
1966
1966
23.
25.
23.
29.
24.
28.
24.
24
95
06
03
53
08
10
10.54
6.23
9.84
4.38
10. 64
7.49
10.42
65.35
66.55
66. 00
65.46
63.97
63.06
64.53
.
1.
1.
1.
.
1.
*
09
55
19
76
98
22
03
26
Main
87
27
10
12
86
37
95
Equivalent percentage
of total anions
C03+
HCO3
S°4
All -American
22. 04
22.20
18. 10
20.57
17. 19
19.55
18.94
19.80
Drain
15. 05
14. 89
14. 98
15.91
15. 14
15.26
13.79
53. 83
50.77
53.70
50.55
54. 61
50. 91
52.57
52.42
52. 82
44.29
51. 09
46.53
50. 70
40.24
53.75
Cl
Canal)
23.97
26. 80
27.90
28. 66
28.20
29.33
28.28
27.45
32. 13
40. 15
33. 94
36.84
34. 16
43.60
32.46
H03
. 17
.23
. 15
. 22
. -
.21
.20
.20
-
.67
-
.73
-
.90
-
Ave. 25.43 8.51 64.99 1.08 15.00 48.49 36.18 .77
Average for Main Drain Minus Average for Colorado River
-11.25-10.17 21.61 -.18 -4.80 -3.93 8.73 .57
-------
63
organisms. Nitrates move with water and other soluble salts into
the drainage system, unless the nitrate ions are used by the growing
crop, by micro-organisms, or undergo dentrification in a reducing
atmosphere. The possibilities for some nitrate to get in the drainage
or groundwater are so numerous that it is difficult to generalize on
the amounts contributed by the soil as a result of irrigation.
The soluble phosphorus content of the soil solution of most soils
is Low. Biggar and Corey (41) report that the soluble phosphorus in
the soil solution of surface soils seldom exceeds 0. 2 mg/1 with a com-
mon range of 0. 01 to 0. 1, with displaced soil solutions of 0. 03 for
surface soils and subsoil soil solutions frequently Less than 0. 01 mg/1.
Except for very coarse soils, most have a high fixing capacity for
phosphate. If irrigation water contains appreciable amounts of phos-
phorus, 1 mg/1 or more, the concentration in the drain would likely
be Less than in the original water as a result of the "fixation" of
phosphorus by the soil. If the phosphate content of the irrigation
water is nil, then there may be an increase in the phosphate content
of the drainage water as a result of release of phosphorus from the
soil particles, from organic matter, and from the phosphorus in the
soil solution. Whether phosphorus is added to or removed from the
water is dependent on the concentration of phosphorus in the irrigation
water and on the nature of the soil through which the water percolates.
Phosphates are carried into water with sediments and dust from the
land and also in the form of organic materials. Oxidation of the
organics in the water can account for some of the soluble phosphate
in the return flow. Some phosphorus can also come from the soil
materials in the bottom and banks of ditches and drains. Sorption and
release of phosphorus have a vital influence in increasing or decreas-
ing the amount of phosphorus in solution.
Climate has a major effect on the kind of soils produced and on
the kind and amount of salts in the return flow when the soils are
irrigated. In the weathering process of rocks and minerals, the highly
soluble salts of sodium and potassium are first to be released. These
are leached from the profile and carried to the ocean, moved by water
to another position, or accumulate in the profile if precipitation is Low.
In humid climates weathering and leaching progress much faster than
in dry and/or cold climates.
When soils in humid areas are irrigated, climate also influences
the composition of the return flow. The amount of irrigation water
required is small compared to that required in warm and dry areas,
and there is a low concentration of salts in the drainage water. The
proportion of sodium and potassium salts in the drainage water is
small in comparison to iron and aluminum. In a warm-dry climate
the soils are less mature and contain considerably more salts of
-------
64
sodium, potassium, calcium, and magnesium. When irrigated, the
natural waters likely contain more salt than in humid areas, and more
irrigation water is required for crop production.
Climate, then, is a major factor responsible for the salinity and
sodium problems found in the arid irrigated areas of the West. Climate
can have many indirect effects on pollution. The amount and intensity of
precipitation can also influence the amount of erosion and the accompany-
ing sediment load of the return flow. Many of the pesticides are moved
with the eroded mineral and organic soil particles.
Van Denburgh and Feth (42) estimated the annual solute erosion
in 11 important river basins, Table 17. The wide range in tonnage
was attributed to a complex of causes, among which were differences
in geology, climatic environment, and the activities of man. Rates of
solute removal were highest in areas of abundant precipitation and run-
off, in contrast to rates of sediment removal, which are characteris-
tically highest in basins subject to 10-15 inches effective annual precip-
itation.
Concentration by evapotranspiration
Consumptive use of water by evaporation and/or transpiration
concentrates the pollutants in the water. Unless the pollutants pre-
cipitate, are adsorbed or decompose, the concentration will be in
proportion to the amount consumed. When water is used to irrigate
soils, most salts in the water will be concentrated in the drainage
water. Many other changes in the water may occur as a result of
passing the water through the soil, as previously explained under
"Irrigation Practice. "
Fertilizers and amendments
To understand the problem of pollution of drainage water from
fertilizers, it is necessary to understand the factors which affect the
forms and solubilities of the plant nutrients and the manner in which
these are transported into the return flow. The nutrients of major
concern as pollutants are nitrate-nitrogen and phosphorus. Nitrate
in the drainage water can originate from rain, dust, soil, organic
matter; manures, an accumulation in the soils prior to irrigation,
fixation by micro-organisms, fertilizers, and from the wastes in
urban and industrial runoff. It is removed from the soils by crops,
by dentrification, and by drainage water. It is, therefore, difficult
to determine the source of nitrate in drainage water.
-------
Table 17. Rates of runoff and solute erosion for the period 1952-1957 (except as noted)1 (42).
River and Station
Columbia near Rufus, Oregon2
Willamette at Salem, Oregon
Rogue at Grants Pass, Oregon3
Sacramento at Knights Landing, Calif.
San Joaquin near Vernalis, Calif.
Colorado near Grand Canyon, Arizona
Gila below Gillespie Dam, Arizona
Rio Grande at El Paso, Texas'*
Pecos near Red Bluff, New Mexico
N. Platte below Guernsey Res. , Wyo.
Yellowstone near Sidney, Montana
Entire 11 -Basin Area
Drainage
basin
area
mi2
177, 000
7, 300
2,420
15, 000
14, 000
138, 000
49, 600
36, 600
19, 500
16, 200
69,400
545, 000
Average
yearly
runoff,
acre-ft
66, 600,000
19, 600, 000
3, 180, 000
7, 860, 000
3,240,000
11, 300, 000
46, 800
523, 000
73, 600
949, 000
8, 000, 000
121,000, 000
Weighted
Average solute load removed solute-
Concen-
tration,
ppm
132
50
77
168
167
615
327
896
4, 630
406
419
192
Tons
per
year
12, 000,000
1, 340, 000
335, 000
1, 320, 000
738, 000
9,460, 000
208, 000
638, 000
464, 000
524, 000
4,560, 000
31, 600,000
CO. U&1UJ.1
Tons rate,
. 0
mi"*- tons
yr-1 mi yr
68
MO } 1?°
11 } -
68
4.Z1
17 S 12
24 ]
32 ) 59
66 f V
58
*Data from U. S. Geological Survey (1956-1961), except as noted.
2Data do not include contributions of Columbia River basin upstream from station at international
boundary.
3Data for 1953-1957 only.
''Data for 1931-1936; from National Resources Committee (1938).
cr*
en
-------
66
The presence of plant nutrients in surface water is often attri-
buted to a seemingly large tonnage of fertilizers applied to the land
for maximum crop production. Yet, the amount of fertilizers applied
to the soils of the United States is low compared to the amount used
in the Netherlands, as shown in Table 18 (34).
Table 18. Plant nutrients applied in 1965 (34).
Average pounds per acre
Nutrient United States Netherlands
Nitrogen 22 244
P_O 17 93
CA O
K O 13 116
C*
On much of the land the amount of fertilizer applied is less than
that used by the crop. A low average application, however, does not
exclude the possibility of excessive amounts being used on some acre-
age. On some high value crops, such as celery, the common practice
is to make heavy applications of fertilizers, particularly nitrogen,
coupled with frequent irrigations. In such cases it is likely that con-
siderable nitrate may be leached with the excess water and appear in
the drainage system.
Doneen (36) concluded from a careful study in the San Joaquin
Valley of California that in one field receiving heavy application of
fertilizer a large portion of the nitrate in the drainage water was from
the fertilizer. In two other fields recently drained, he could not come
to the same conclusion because nitrates had been accumulating in the
subsoil and groundwater for a long time. It is estimated that from
combined sources the nitrate-nitrogen content of the water in the San
Luis drain will be 20 mg/1 (43).
Phosphate fertilizers can increase the phosphorus content of
drainage water in several ways: percolating water passing through a
heavily fertilized sandy soil low in fixing capacity will carry soluble
phosphorus into the drains. Fertilizers applied to the surface of soils
tend to stay near the surface and saturate the "fixing"site. When the
fertile surface particles are eroded by wind or surface runoff, the
phosphorus is carried with the sediments into the drainage system.
Here the phosphate equilibrates with the phosphorus in the drainage
-------
67
water and may increase the concentration in solution unless the con-
tent of the water is at or above the equilibrium concentration.
Biggar and Corey (41) speculate that runoff water in contact with
fertile surface soils can pick up soluble phosphorus as it moves over
the surface of the land and that the concentration in the runoff water
might range up to a few tenths of a mg/1.
Phosphate fertilizer can also have a less direct effect: it can
stimulate plant growth, and then parts of the plant, such as dried
leaves, are carried by wind or water into the drainage water where
the plant material is mineralized by micro-organisms, with the re-
sulting accumulation of soluble inorganic phosphorus in the water.
Johnston e_t al (44) studied N and P loss in tile drainage effluents
from a number of tile drainage systems in irrigated areas in the San
Joaquin Valley of California. A number of cropping practices, with
crops (cotton, alfalfa, rice), fertilizers and irrigation water applica-
tions as variables were involved in the study. Initial tile effluent
analysis in a previously unirrigated noncropped area showed an N
concentration of 1 mg/1. Another system that had been cropped to
alfalfa and had a low discharge over the period of a year yielded a
range of N between 2. 0 and 14. 3 mg/1. On systems where high rates
of N fertilizer were applied, the concentrations ranged up to 62.4 mg/1.
In the systems reported, the range of concentrations of nitrates varied
from 1. 8 to 62.4 mg/1, with a weighted average of 25.1. The loss of
nitrogen in the drainage flow was significant, but the percentage loss
of phosphorus was not.
Both nitrogen and phosphorus can be carried directly into the
surface drains with the tail water from fields where the fertilizer is
being applied in the irrigation water. Other sources of nutrient pol-
lution are the animal wastes in runoff from, pastures and feedlots which
may be commingled with the irrigation return flow.
Pesticides
Pesticides are recognized potential pollutants in water. As with
nutrients the origin is not restricted to agricultural usage. Pesticides
are used in cities, industrial areas, and forests as well as on farms.
They can enter the water by direct application from drift during appli-
cation or be washed in from adjacent lands adsorbed to-eroded sedi-
ments. Pesticides can thus also pollute the waters of irrigation return
flow. There is nothing unique about pesticide pollution and irrigation
except perhaps where pesticides are used to control weeds and insects
along irrigation canals and open drains.
-------
68
Many of the pesticides used are sorbed chemically and physically
by the soil particles. Those thus sorbed are not likely to enter sub-
surface drainage waters. LeGrand (45) reporting on movement of
pesticides in soils suggests that it is likely that most pesticides in
streams result from overland flow. Nicholson (46), in discussing
pesticide pollution control, states:
The two principal sources of water pollution by
pesticides today are runoff from the land and discharges
of industrial waste, either from industries that manufac-
ture or formulate pesticides or from those that use these
compounds in their manufacturing processes. Less
important causes of pollution are (i) activities designed to
control undesirable aquatic life, (ii) careless use of pesti-
cides, and (iii) occasional accidents in transportation.
Johnston ei^ al (47) analyzed drainage effluent from systems located
on irrigated land in the San Joaquin Valley of California. On experi-
mental areas the insecticides DDT, Parathion, and Lindane had been
added. Only relatively small quantities of chlorinated hydrocarbon resi-
dues were found in the tile drainage effluent, but higher concentrations
were found in the effluent from open drains where both surface and sub-
surface drainage waters were collected. Traces of residue were found
in the irrigation water applied to tile-drained farms. When the con-
centration factor was considered, i. e. , depth of irrigation water
applied / depth of drainage water removed, on a unit basis, the total
quantity of insecticide residue in the tile drainage effluent did not ex-
ceed, and was generally less than, the total quantity of residue applied
in the irrigation water. Tail water, or surface runoff, contained from
seven to 12 times more residue than the applied water when DDT was
used on the land, and as much as 85 times more residue than the irri-
gation water when Lindane was applied to the land. Relatively large
concentrations of residue were found also in the surface soil of the area
studied.
As a generalization, it appears that the chlorinated hydrocarbons
such as DDT persist in soils (48, 49) and do not move in appreciable
concentrations through the soils and into the drainage effluent as ground-
water. Movement is primarily with suspended sediment, either organic
or inorganic materials in streams and open drain flow. The thiophos-
phates such as Parathion decompose rapidly and do not persist in soils
or water.
Pesticides can be transported in the air while applications are
being made and be deposited in water remote from the area of applica-
tion (50). Wind can remove surface soil to which is adsorbed pesticides
and this can be deposited by rain or the settling dust.
-------
69
Faulkner (51) found large numbers ofnematod.es, including plant
parasites, in irrigation and drainage waters. There is no indication
yet as to the nature and magnitude of any pollution problems that might
accompany the treatment of water for the control of nematodes.
Indirectly, pesticides may add other pollutants to soil and water.
The organic phosphorus insecticides and miticides readily decompose
in soil and release soluble phosphorus. Other organic pesticides are
composed of compounds containing mercury, zinc, manganese, copper,
chromium, cadmium, and tin. When the organic compounds are de-
composed, the metal ions are released.
Municipal and industrial supplies
The occurence of municipal and industrial waste waters in water
supplies used by irrigated agriculture may be the result of incidental
discharges into a common receiving water subsequently used for irri-
gation or from direct, intentional application of such waste waters as
a prime source of supply. In either case, the nature and concentra-
tion of any constituent that may be considered as a potential pollutant
will depend upon the specific characteristics and origin of the waste
water; i. e. , whether (a) of purely domestic origin, (b) a combination
of domestic and industrial origin, or (c) essentially an industrial dis-
charge. In addition, the characteristics of the waste water may be
ameliorated by the degree of treatment and/or dilution afforded the
effluent prior to use.
Nature and extent of practice of using waste waters. The prac-
tice of using municipal waste waters for irrigation purposes in the
United States evolved during the latter part of the nineteenth century,
following the advent of the water-carriage system of domestic waste
disposal. While historically this practice probably originated from
considerations of the fertilizer value of sewage, the primary impetus
for using municipal sewage for irrigation in this country stemmed
from the need to augment the limited water supplies and inadequate
rainfall associated with the arid and semi-arid areas of the West.
Table 19 indicates that in terms of overall quantity needs for
irrigation, the contribution possible from reuse of municipal supplies
would be extremely modest even if it were all available for this pur-
pose. On the other hand, the magnitude of industrial use of water and
the relatively small consumptive losses from such use might make
this appear promising as a source of supply. Unfortunately, the rela-
tionship between location of major water-using industries and irrigated
agricultural areas, as shown in Table 20 and Figure 5, limits this
possibility. An additional difficulty in using municipal and industrial
-------
Table 19. United States: Estimated water use, 1900-1975 (Billions of gallons; daily average)(6l).
-o
o
Year
1900
1910
1920
1930
1940
1944
1945
1946
1950
1955
I960
1965
1970
1975
Irrigation
20.2
39.0
55.9
60.2
71.0
80. 6
83. 1
86.4
100. 0
119. 8
135. 0
148. 1
159. 0
169.7
Public
Water
Supplies
3.0
4.7
6.0
8.0
10. 1
12.0
12,0
12. 0
14.1
17, 0
22.0
25.0
27.8
29.8
Domestic
2. 0
2.2
2.4
2.9
3. 1
3.2
3.2
3.5
4.6
5.4
6.0
6.5
6.9
7.2
Self -Supplied
Industrial
and
Miscellaneous
10.0
14. 0
18. 0
21. 0
29.0
56. 0
48.0
39.0
46. 0
60.0
71. 9
87.7
103. 0
115.4
Steam -
Electric
Power
5.0
6.5
10.0
18.4
22.2
35.9
28.8
26.9
38.4
59.8
77.6
92.2
107.8
131.0
Total
40. 2
66.4
92.3
110. 5
135.4
187.7
175. 1
167. 8
203. 1
262. 0
312. 5
359. 5
404. 5
453. 1
-------
Table 20. Regional incidence of industrial waste discharge, by major industrial sectors, 1964 (40).
Percent of Discharge of Industry's
Industry
Regionally North. South.
Assignable ea(jt ^
Discharge
Meat products
Dairy products
Canned & frozen foods
Sugar refining
All other food products
Textile mill products
Paper & allied products
Chemical & allied products
Petroleum & coal
Rubber & plastics, n. e. c.
Primary metals
Machinery
Electrical machinery
Transportation equipment
All other (plus unassignable)
Total industrial discharge
90.6
64.0
68.8
56.7
95.1
98.4
98.3
100.0
97.6
76.8
87.8
100.0
99.0
98.2
-
5.0
10.3
2.4
6.3
21.0
31.1
23.5
12.8
26.8
22.6
7.4
49.6
35.2
31.2
95.7
19.9
7.0
3.4
18.4
.
4.3
55.6
26.4
5.0
.4
3.9
1.0
.7
3.3
1.7
4.0
6.9
Great
Lakes
4.0
22.4
8.0
-
15.5
1.5
12.4
13.0
19.7
36.8
38.4
16.8
19.8
46.8
18. 1
23.4
Ohio
6.0
3.4
-
-
7. 1
.6
2.6
19.7
1.8
5.8
33.4
8. 1
28.6
5.9
8.7
18.2
Upper Lower
Missis- Missis-
nessee . . .
sippi sippi
32.3
7.2
3.4
-
.9 20.1
8. 1
3.4 5.6
6.7 1.6
.8
2,6
.5 2.3
22.8
1.1 6.6
2.1
8.1 11.9
2.4 3.5
1.0
-
-
36.4
4.3
1.5
1.6
5.4
9.1
2.6
-
-
-
-
35.6
3.7
Wastewater
Arkansas,,, . Colorado Pacific .
Ml8: White- W'8 "n and North- {^~2
Red Gulf Great west1 f°mia
23.2
5.2
-
10.4
4.9
-
. 1
. 4
1.6
1.9
.3
-
1. 1
-
1.7
1. 2
4.0
-
-
-
1.0
-
3.4
1.3
1. 1
-
-
-
1. 1
.8
6.6
1.4
2.0
-
-
-
1.5
-
1.4
32.0
25.5
-
3.2
.7
-
-
4.3
12.0
5. 1
5.2
14.9
-
1.5 5.0
-
16.7
. 1 1.2
.2 .2
-
.2 .9
.7
-
1.7
7.2 18.8
.3 4.1
1.0
6.9
20.7
3.6
7. 1
-
1.2
.8
10.5
.6
.2
. 7
2. 2
8.0
8. 1
2.7
-------
-
ARKANSAS-WHITE AND RED
* INCLUDES ALASKA
I INCLUDES HAWAII
fcv"
Figure 5. Major drainage regions, industrial definitions (40).
-------
73
effluents for irrigation is the poor correlation between crop needs and
waste water flows. In some instances, however, ground-water re-
charge and storage of these effluents for subsequent use is feasible.
Thomas and Law (52) recently reported that of about 1, 300 soil
systems receiving surface applications of waste waters in the United
States in 1964, about two-thirds of these systems were being used
specifically for waste water treatment, while in the remaining one-
third of the systems, irrigation of crops was the primary objective.
Use of municipal and industrial waste waters for irrigation sup-
ply is currently of minor importance in the total needs of irrigated
agriculture, although these sources may be significant in certain
localities. Dual purpose use of effluents for crop irrigation, as well
as economical and efficient method of treatment and disposal, appears
to be emerging as an attractive concept for some municipalities and
industries, and may become a significant factor in the extent of this
reuse practice.
Before examining the characteristics of municipal and industrial
waste waters, it is appropriate to review the potential pollutants in
irrigation waters summarized by Wilcox (37) in Table 13 as a basis
for evaluation of the suitability of these waste waters as a source of
supply.
Characteristics of municipal waste waters, (a) Biological con-
siderations. In the United States the practice of using raw sewage for
irrigation was essentially abandoned in the early part of this century,
and by the 1930 "s a minimum of primary treatment was required (53).
Early requirements for the use of municipal sewage effluents were
primarily concerned with the health hazards involved and, in general,
limited the use of such water to crops other than those used for human
c on sumption.
An example of a recent coliform requirement for water used for
various irrigation purposes, established by the California State Depart-
ment of Public Health in 1967, is shown in Figure 6 (54). Compliance
with this requirement is accomplished by primary and secondary treat-
ment, disinfection with chlorine, minimizing public contact with the
reclaimed water, irrigation during non-use periods, as well as other
measures.
(b) Chemical quality. The composite chemical quality of raw
municipal waste water is only slightly affected by conventional primary
and secondary treatment and thus is basically the sum of the constit-
uents comprising the chemical quality of the original water supply and
the constituents added through municipal use. This "municipal use
-------
Figure 6. Summary of standards for use of
reclaimed waste water (54)
-------
75
increment" may be partly of domestic origin, concentration due to con-
sumptive loss (normally 10-30 percent), from industrial and commer-
cial contributions, and/or groundwater infiltration of the waste water
collection system. Since the quality of any municipal water supply may
vary significantly, depending upon the nature of its source as well as
upon the municipal use increment, the reported chemical quality of any
municipal waste water effluent may vary considerably. However, since
most municipal water supplies represent water of excellent quality for
irrigation use, it is generally the chemical increment picked up through
municipal use that will adversely affect the quality for reuse.
In most water-short areas where reuse of water is a practical
necessity there is a growing concern for controlling the magnitude of
the municipal use increment by careful regulation of undesirable con-
tributions of highly mineralized wastes. Several studies of mineral
increments from community use have been made (55, 56, 57; 58, 59,
60) and examples of data reported are shown in Tables 21, 22, 23 and
24. The most important potential pollutants in municipal waste water
effluents affecting an irrigation supply would include total dissolved
solids, sodium, chloride, alkalinity and boron.
Characteristics of industrial waste waters. Characterization of
industrial wastes is exceedingly difficult for several reasons: (a) the
numerous water-using and waste-producing varieties of industries,
(b) the wide range and spectrum of potential pollutants that are involved,
sometimes varying significantly within the same industry, and (c) the
paucity of factual data available on the volume and pollutional character-
istics of many industrial wastes.
Examples of important water-using industries and associated
pollutional characteristics of their waste waters are shown in Tables
25 and 26.
Potential pollutants of industrial origin that are of particular
concern to irrigated agriculture include: (a) total dissolved solids,
sodium, and chlorides, (b) boron, (c) heavy metals, (d) pesticides,
and (e) radioactivity.
Fate of municipally and industrially derived pollutants in irriga-
tion return flows. Certain pollutants, initially derived from the use of
municipal and industrial effluents as a source of irrigation supply, re-
appear in the return flows in essentially the same form, but possibly
in increased concentrations. Other pollutants are degraded during the
course of the irrigation use to where they are no longer capable of be-
ing identified. Other pollutants may be taken up by the crops or fixed
more or less permanently in the soil. Table 27 depicts the probable
fate of some common pollutants occurring in irrigation supplies orig-
inating from municipal and industrial effluents.
-------
76
Table 21. Average
increments added
Overall
Average
BOD
COD
ABS
Na+
K+
NH4+
Ca++
Mg++
Cl"
NO3"
N02~
NCO3"
i5 \_^ j
/\.
SiO3 =
P04E (total)
PO,= (ortho)
Hardness
(CaCO3)
Alkalinity
(CaC03)
TDS
22
111
6
69
10
19
17
7
75
9
1
104
-1
28
16
24
22
69
85
323
Range
8- 45
36-218
2- 10
8-115
7- 15
3- 50
1- 44
0- 24
14-200
0- 26
0. 1- 2
-44-265
0--10
10- 57
13- 22
2- 50
7- 34
10-185
-35-217
128-541
by community use of
Eastern
Averag
21
96
5
59
9
21
24
8
53
11
0.8
147
-1
28
15
19
20
95
121
287
e Range
8- 33
36-159
2- 10
42- 98
7- 12
9- 29
1- 44
3- 11
14-102
0- 26
0. 1- 2
49-265
0- -5
12- 52
15
2- 35
12- 34
15-151
40-217
128-457
water (60).
Western
Average Range
23
218
8
74
11
18
13
7
92
7
2
81
-1
29
17
28
25
58
66
352
10- 45
218
6- 9
8-115
7- 15
3- 50
2- 30
0- 24
20-200
0- 15
2
_44_247
0--10
10- 57
13- 22
7- 50
7- 34
10-185
-36-203
194-541
-------
77
Table 22. Summary of mineral increments in domestic waste water
for 15 California communities (56).
. , . Minimum
Analysis
range
Dissolved solids ppm Trace
Conductivity K x 105
Boron (B) ppm
Percent sodium, percent
Sodium (Na) ppm
Potassium (K) ppm
Magnesium (CaCC>3) ppm
Calcium (CaCO3) ppm
Total Nitrogen (N) ppm
Phosphate (PC>4) ppm
Sulfate (SO4) ppm
Chloride (Cl) ppm
Total alkalinity (CaCO3) ppm
30
.1
1
30
12
2
20
Maximum Normal range
range domestic sewage
1200
240
3. 8
42
290
22
110
250
42
50
75
550
230
100-300
30-
. 1-
5-
40-
7-
15-
15-
20-
20-
15-
20-
100-
60
.4
15
70
15
40
40
40
40
30
50
150
Table 23. Sources and amounts of salt pickup in two sewage systems
(55).
Source of pickup
Contribution to total pickup
Los Angeles
Regeneration waters
Oil brines
Domestic use
Commercial and industrial
Seawater infiltration
County
mg/1
25
640
225
350
-
City
mg/1
14
356
153
112
TOTAL pickup
1240
635
-------
00
Table 24. Comparison of tap water and sewage effluent * (58).
Test
COD-unfiltered
COD -filte red
COD-filtered, corrected for Cl"
Anionic detergents (ABS)
Hydroxylated aromatic (tannic acid)
Carbohydrated (glucose)
Reducing sugars (glucose)
Organic nitrogen (N)
Nitrate (N)
Nitrite (N)
Ammonia (N)
Total alkalinity (CaCO3)
Calcium (Ca++)
Magnesium (Mg++)
Potassium (K+)
Sodium (Na+)
Phosphate (PO4=)
Total
Ortho
Sulfate (SO4=)
Chloride (Cl")
Residue 105°C
Residue 600°C
Loss on ignition
pH
Specific conductance, micromhos/cm
Tap water sources
Batavia
7.8
4.5
0.03
0.04
0.05
<0.005
0. 15
0.03
0.008
<0. 02
22
20
5
2.0
8.5
6.045
0.004
56
11.5
98
78
20
9.4
193
Dayton Hamilton
5.7
1.4
0.02
0.01
0.06
<0. 005
0. 04
1.41
0.003
<0. 02
38
22
11
2.1
17.5
0.051
0.009
79
16.8
177
149
28
8.4
307
2.3
0,3
0. 03
0.01
0. 04
<0. 005
0.02
1. 18
0.040
<0. 02
40
12
11
2.0
17.3
0.038
0. 005
56
9.0
140
133
7
8.5
236
Lebanon
8.2
2.7
0.02
0.07
0.08
<0. 005
0.09
0.08
0.095
<0. 02
311
108
30
1.6
13.9
0.022
0.006
96
22.5
520
368
152
7.7
750
Lov eland Average Batavia
5.4
1.7
0. 01
0. 11
0.03
<0. 005
0.07
0.62
0.008
<0. 02
294
96
21
1.8
10.5
0.58
0.032
53
15.7
344
262
82
7.4
622
6.0
2.0
0.02
0.05
0.05
<0. 005
0. 07
0.67
0.031
<0. 02
141
52
15
1.9
13.5
0. 043
0.011
68
15.1
256
198
58
8.3
422
171
128
116
10. 1
2.9
2.6
<0. 005
4.1
3.1
0.59
6.8
174
63
14
13.7
50
34.6
33.8
95
51.8
472
359
113
7.5
730
Sewage effluent source
Dayton Hamilton
169
114
99
7.2
1. 3
2.2
<0. 005
1.4
4.9
0. 10
16.3
198
53
21
9.3
68
19.4
17.9
91
67.3
5'25
380
145
7.3
864
165
92
79
6.2
2.0
5.0
<0. 005
3.5
0.2
0.08
22. 1
257
54
22
11.2
63
19.5
18.9
108
49.4
597
445
152
7.8
796
Lebanon
92
78
49
4.6
0.6
1.0
<0. 005
1. 1
7.8
0. 34
19.4
351
109
33
9.8
112
18.5
15.6
111
124
648
526
122
7.8
1, 185
Loveland Average
146
92
78
9.0
1.5
1.5
<0. 005
1.5
4.6
0.56
15.7
335
97
22
11.8
55
29.5
27.5
99
62.0
492
389
103
7.4
1,003
149
101
84
7. 4
1. 7
2.5
<0. 005
2.3
4. 1
0.33
16. 1
263
75
22
11.2
70
24. 3
22.8
101
70.9
547
420
127
7.5
916
'Table values are mg/1 except pH and specific conductance.
-------
Table 25. Some significant chemical in industrial waste waters (61).
79
Chemical
Industry
Acetate rayon, pickle and beetroot manufacture.
Cotton and straw kiering, cotton manufacture,
mercerizing, wool scouring, laundries.
Gas and coke manufacture, chemical manufacture.
Sheep-dipping, fell mongering.
Laundries, paper mills, textile bleaching.
Plating, chrome tanning, aluminum anodizing.
Plating.
Soft drinks and citrous fruit processing.
Plating, pickling, rayon manufacture.
Plating, metal cleaning, case-hardening, gas
manufacture.
Wool scouring, laundries, textiles, oil refineries.
Gas and coke manufacture, chemical manufacture,
fertilizer plants, transistor manufacture, metal
refining, ceramic plants, glass etching.
Manufacture of synthetic resins and penicillin.
Petrochemical and rubber factories.
Textile bleaching, rocket motor testing.
Battery manufacture, lead mining, paint manu-
facture, gasoline manufacture.
Oil refining, pulp mills
Chemical manufacture, mines, Fe and Cu pickling,
DDT manufacture, brewing, textiles, photoengraving,
battery manufacture.
Plating.
Explosives and chemical works.
Distilleries and fermentation plants.
Gas and coke manufacture, synthetic resin manu-
facture, textiles, tanneries; tar, chemical and
dye manufacture, sKeep-dipping.
Plating, photography.
Food textile, wallpaper manufacture.
Dairies, foods, sugar refining, preserves, wood
process.
Textiles, tanneries, gas manufacture, rayon manu-
facture.
Wood process, viscose manufacture, bleaching.
Tanning, sawmills.
Dyeing; wine, leather and chemical manufacture.
Galvanizing, plating, viscose manufacture, rubber
process.
Reproduced by permission Butterworths. "River Pollution. 2: Causes
and Effects," Klein.
Acetic acid
Alkalis
Ammonia
Arsenic
Chlorine
Chromium
Cadmium
Citric acid
Copper
Cyanides
Fats, oils, grease
Fluorides
Formalin
Hydrocarbons
Hydrogen peroxide
Lead
Mercaptans
Mineral acids
Nickel
Nitro comp.
Organic acids
Phenols
Silver
Starch
Sugars
Sulfides
Sulfites
Tannic acid
Tartaric acid
Zinc
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80
».,..<».,......
Food and drugs.
Canned goods Trimming, culling, juicing, and High in s
Dairy products Dilutions of whole milk, separated High m d
ewed and distilled Steeping and proving of grain. High in dissolved organic solids. Recovery, concentration by centrif-
Apparel-
Textilei
Photographic
products
mdensates, grease and wash and (at*
High in dii
extracted sugar
Evaporation and drying: feed*
BOD filtration
Lime water; brine, alum and Variable pH, high suspended solids. Good housekeeping, screening.
Coffee Pulping and fermenting of coffee High BOD and suspended solids
bean
fish, evaporator and other
water waste*
High in BOD, total and suspended Lime coagulation, dlgeatioi
solids, (mainly starch)
Bottle- washing, floor and equipment High pH, suspended solids and BOD Screening, plus dischari
Leather good*
Laundry trade.
Chemicals.
Detergents
bating o{ hides
dilute acids
lime and BOD
solids flotation, and adsorption
detergents with CaCl,
Corns tarch Evaporator condensate, syrup from High BOD and dissolved organic Equalization, biological filtratic
final washes, waste* from "bottling matter, mainly starch and related
up" proces.
Explosives Washing TNT and gun cotton for
of cartridges from powder and cotton. meUl. acid, chlorination ol TNT. neutralization
oils, and soaps
Phosphate and Washing, screening, floating rocV, Clay*, slimes and tall oils, low pH, Lagooning, mechanical ctanficatioi
silic* and fluoride waste
irptioi
Materials:
Pulp and paper Cooking, refining, washing of fibers. High or low pH; colored; high Settling, lagooning, biological tr«at-
icreenmg of paper pulp suspended, colloidal, and dissolved ment. aeration, recovery of by-
solids; inorgan.c filler, produU.
Coking
steel
Metal-plated Stripping of oxides, cleaning and Acid, metals, toxic, low volume. Alkaline chlorination of cyanide.
products plating of metals mainly mineral matter reduction and precipitation of
other metal*
product* discharge sand, some clay and coal reclaimed sand
Oil Drilling muds, salt, oil, and some High dissolved salts from field. Diversion, recovery, injection of
natural gase, acid sludge* and high BOD, odor, phenol, and sulfur salts; acidification and burning of
miscellaneous oils from refining compounds from refinery alkaline sludge*
Polishing and cleaning of glass Red color, alkaline nonnettl- able Calcium chloride precipitatic
Washing of stumps, drop solution. Acid, high BOD By-produi
solvent recovery, and oil recovery recirculat
water filtration
Steam power Cooling water, boiler blowdown. Hot, high volume, high inorganic Cooling by t
and dissolved solids neutralitatu
Coal processing Cleaning and classification of coal. High suspended solids, mainly Settling, froth, flotation, drai
leaching of sulfur strata with water coal; low pH. high H2SO4 and FeSO4 control, and scaling of mines
laminated clothes, research-lab acid and "hot" dilution and dispenioi
wastes, processing of fuel, power-
plant cooling waters
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81
Table 27. Probable fate of municipal and industrial pollutants
after irrigation.
Pollutants of Municipal
and Industrial Origin
Probable Fate After Irrigation Use
Total dissolved solids
Sodium
Chlorides
Sulfates
Boron
Reappears in surface and sub-
surface return flows in increased
concentrations (32,40,57,62)
Heavy metals
Phosphorus
Bacteria
Radioactivity
Pesticides and exotic
organic chemicals
Precipitated and fixed in soil;
some may persist in surface
return flow (62, 63, 64, 65)
Removed in soil; some may per-
sist in surface return flow (66,
67,68, 32, 64,61,69, 62)
Removed in soil; taken up by crops;
some may persist in surface return
flow (70, 71, 72,62)
Many removed in soil; will persist
in surface return flow; some may
possibly persist in subsurface
return flow (73, 64, 61, 62)
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82
Irrigation supplies from used water. In many arid and semi-arid
regions of the United States, it has become increasingly necessary to
use and reuse water supplies to the fullest extent possible. Municipal
waste water effluents have been satisfactorily used by irrigated agri-
culture in many instances with few adverse effects. The use of indus-
trial effluents has not been so widely reported, perhaps due to the more
apparent inherent hazards associated with certain readily identifiable
pollutional constituents. In addition, most of the major water-using
industries and irrigated agriculture are not so located with respect to
each other that direct reuse of industrial effluents is physically pos-
sible.
In view of current water pollution control legislation and the high
degree of treatment and removal of potential pollutants being required,
it appears that in the future a marked increase in the utilisation of
available municipal and industrial effluents for irrigation supplies in
water-short areas is inescapable and may even be highly desirable.
Testing and Monitoring
Assessment of the cause and effect relationship between irriga-
tion and water quality, as affected by irrigation return flows, is based
upon the existence of adequate water quality data in time and space.
Insight into the gross adequacy of such data can be provided best by
means of a historical outline of water quality monitoring in the United
States, with special reference to the seventeen western states.
History of water quality monitoring in
western United States
Analyses of the chemical composition of natural waters in the
western United States goes back to the work of Hilgard in the 1800's
(74). He published results of 55 analyses from springs and wells, in
relation to use of such waters for irrigation. He also published seven
University of California Agricultural Experiment Station reports
(75, 76, 77, 78, 79, 80, 81) which contain results of water analyses.
In 1891 a program in water quality analyses with respect to irri-
gation was begun at the Agricultural Experiment Station in Arizona (82).
Similarly, in 1900 a water quality program was begun in New Mexico
(83). In 1903, analyses were made of some Oregon waters (84) with
reference to irrigation. These analyses were valuable from the stand-
point of initiating programs and providing data as a reference for meas-
uring changes.
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83
Beginning of systematic effort for a national picture. In 1903,
R. B. Dole of the U. S. Geological Survey initiated plans to system-
atically sample all major waters of the United States on a recurrent
basis (85). This was to be done slowly and through cooperative agree-
ments with state agencies and others. The first results were published
in 1907 (86) and contained data for 92 stations scattered throughout the
United States east of the one-hundredth meridian. Dole also provided
an extensive treatise on methods of analyses.
Dole's work in 1909 was the beginning of systematic water qual-
ity investigations. The following year Van Winkle and Eaton (87) pub-
lished the first comprehensive water quality survey of waters in
California, involving 37 rivers. These rivers were sampled on a
recurrent basis for one year or more. The analyses were interpreted
in the context of such natural influences as climate, geologic condi-
tions, and vegetation, of potential industrial and other uses, and of
the economic significance. The effect of irrigation on mineral compo-
sition of some waters is also mentioned. Similar studies followed in
Oregon (88), Washington (89) and other states.
Water quality for reclamation. The above investigations were
to establish the value of various state waters as water resources per
se, with some industrial orientation, and to provide a background of
basic data. Other investigations were initiated by the Reclamation
Service to ascertain the value of various waters for irrigation. In
1905 and 1907, Stabler (90) of the U. S. Geological Survey supervised
a systematic sampling program for a 55-station network having wide
coverage throughout the West. The waters chosen for sampling were
those likely to be utilized by the Reclamation Service; the sampling
program was to assess potential salinity and silting problems.
The various agricultural experiment stations were also active
in assessing water qualitywith respect to irrigation, beginning with
Hilgard in 1886. One of the most recent works of this nature is by
Thorne and Thome (91).
Data retrieval, initial efforts. In 1924, Clarke (85) compiled
and published all known analytical data for waters of the United States
with comments concerning land use and other lithologic factors rele-
vant to the water quality characteristics of the respective waters.
In 1926, Collins and Howard published "Index of Analyses of
Natural Waters in the United States" (92) which was intended to in-
clude reports of all federal and state surveys, experiment stations,
health departments, and references to journal articles. This was an
important landmark in that it was the first attempt to aid "informa-
tion retrieval" of water quality data -- an obviously important contri-
-------
84
bution as the amount of studies proliferated, such that works similar
to Clarke's (85) were no longer feasible. The publications listed in
this Index are in the form of an annotated bibliography. Collins and
Howard updated their Index in 1932 (93).
First permanent monitoring network. In 1931 the first perma-
nent water quality monitoring network was established by the Inter-
national Boundary Commission to monitor streams flowing into
Mexico with respect to chemical, sanitary, and physical character-
istics (94). Each of the major streams were monitored at several
points to a considerable distance upstream and annual reports
published.
Establishment of a permanent national network. The first
permanent national water quality network was established by the U.
S. Geological Survey in 1941. Annual records of chemical quality,
suspended sediment, and water temperature have been published
since 1941 (95). From 1941 to 1963 these records were published
annually as water supply papers (95). By 1963 the Geological Survey
maintained 419 stations on 270 streams. Samples were collected
daily and monthly at 276 of these locations for chemical-quality
studies.
Beginning with the 1964 water year, these records were
published as a new series on a state boundary basis (96). The pri-
mary purpose of this series is to make the data available for im-
mediate use. These same records are to be published in Geological
Survey Water-Supply Papers ate five-year intervals.
Permanent network established for irrigation return flows.
A major contribution to the study of irrigation return flows was
initiated in 1951 with the selection of 100 permanent monitoring
stations by the Subcommittee on Hydrology, Water Resources
Council). In 1957 data for 82 irrigation network stations were
reported in the annual water supply paper, "Quality of Surface
Waters for Irrigation, Western United States" (97).
The purpose is indicated in the 1957 report: "A need was
recognized for comprehensive continuing information about the
chemical quality of surface waters used for irrigation and the
changes resulting from the drainage of irrigated lands. In recogni-
tion of this problem, the Subcommittee on Hydrology, Interagency
Committee on Water Resources on February 6, 1950, approved a
list of 106 network stations on streams in western United States at
which water samples were to be collected and analyzed with partic-
ular reference to the use of these stream waters for irrigation" (97).
-------
85
It is significant that among the criteria for selection of net-
work stations, two are quite relevant to today's thinking: (a)
"Consideration should be given to the location of irrigation develop-
ment areas that are now affecting or are likely to affect the chemical
quality of the river water," and (b) "Only those stations should be
proposed that are likely to reflect important changes in chemical
quality over a period of years." According to Love (98), "These
long-term records will assist in the determination of quality of
water prior to irrigation development, the extent of impairment of
water quality due to drainage return, requirements for maintaining
proper salt balance, and the equitable division of water between
projects, states, and adjoining nations." Discussion of salinity
conditions is given for each of the major river basins in the
respective annual reports (97).
Pollution-oriented national water quality network. The next
major impetus in the direction of systematic water quality monitoring
was the establishment of the National Water Quality Network in 1956
under Public Law 660, by the U. S. Public Health Service (99),
Division of Water Supply and Pollution Control. (This activity was
transferred to the Department of the Interior in 1966 as the Federal
Water Pollution Control Administration. ) For the initial phase of
the program, 50 sampling stations were established, beginning
operation October 1, 1957.
The significance of this national network is partly that it
adds to the wealth of information through enlargement of the existing
networks; but more important, this network was established to
monitor the nation's water in terms of pollution relevance, and to
provide comprehensive analyses in order to assess the expanding
dimensions of the water pollution problems -- some of which are
relevant to irrigated agriculture. The routine analyses include:
(a) Radioactivity (weekly).
(b) Plankton populations (monthly or semi-monthly).
(c) Coliform organisms (weekly).
(d) Organic chemicals (monthly).
(e) Biochemical, chemical, and physical measurements,
including bichemical oxygen demand, dissolved oxygen, chemical
oxygen demand, chlorine demand, ammonia nitrogen, pH, color,
turbidity temperature, alkalinity, hardness, chloride, sulfate, and
total dissolved solids (weekly).
-------
86
(f) Trace elements (two-month composite of weekly samples).
Project-oriented data collection activities. The Colorado
River is one of the most intensively studied streams with respect
to salinity. A sampling program was begun by Collins and Howard
in 1925 (100) and has continued intermittently. The data have been
summarized by lorns, _et al. (101). Presently, the Colorado River
Basin Project of the Federal Water Pollution Control Administration
maintains a sampling network for the comprehensive study of salinity
in the Colorado River System. This network, operated since 1965,
contains 35 stations in addition to the USGS network. Common
cations and anions are measured from monthly samples.
Some western states have very modest data collection pro-
grams, others moderate, and some, such as California., extensive.
Using Utah as an example, Stewart and Hirst (102) and later Greaves
and Hirst (103) reported analyses of a number of irrigation waters
in the state. The next activity was not until 1951 with the extensive
sampling survey of Thorne and Thorne (91). In 1958 Conner and
Mitchell (104) compiles results to that date of all available analyses
for surface and groundwaters in Utah.
G r oundwater. Monitoring activities related to groundwater
have been much less systematic than activities in the surface water
area. The pattern appears to consist of assessment of groundwater
quality characteristics on an area-by-area basis as the need arises
-- which need may be related to project investigations or to suitability
for resource development.
California, through its Department of Water Resources,
has had one of the most comprehensive systematic sampling programs
of any state. Its plan to sample all groundwater of the state was
initiated in 1952 as a cooperative program with the U. S. Geological
Survey.
Data retrieval. Data availability is of parallel importance
with sampling activities. A large amount of data is available through
the annual reports of basic data of the U. S. Geological Survey and
the Federal Water Pollution Control Administration, and from annual
reports of some states. These are mostly data taken from permanent,
federally operated, water quality networks. Much data are published,
however, as supportive of project investigations, and some are
maintained within the files of organizations only for internal use.
Knowledge of such efforts sometimes requires determination to
acquire.
-------
87
The first attempt to facilitate data retrieval was Clarke's
1925 compilation (85) of all analyses known from all sources to
1925. Thus all data taken in the United States prior to 1925, avail-
able through normal federal, state, and local channels, were pre-
sented in his report. The next significant effort at data compilation
was lorns1, _et_al (101) report of basic data for the Colorado River.
Since nationwide and even, in some cases, basinwide all
inclusive data compilations today are unfeasible as a matter of
routine, inventories of data sources have' been compiled. The first
was that of Collins and Howard in 1926 (92), which listed all known
reports containing water quality analyses, from federal, state, and
other sources. This listing was updated by Collins and Howard in
1932 (93) to cover the intervening years. The next publication of
this type was Bulletin 2 (104) "Inventory of Published and Unpublished
Chemical Analyses of Surface Waters in the Western United States."
The report was prepared by the Hydrologic Subcommittee of the
Federal Interagency River .Basin Committee, and agricultural use of
western waters was preeminent in the thinking of the committee in
sponsoring the report development. A supplement was the "Inven-
tory of Published and Unpublished Chemical Analyses of Surface
Waters in Western United States, 1947-55" Bulletin 9 (106). The
next supplement was USGS WSP 1786 by Woodward and Heidel (107),
which covers the period October 1, 1955 to September 30, 1961,
for states west of the Mississippi River.
In 1964 the Bureau of the budget authorized (in Circular A-67)
the Department of the Interior to coordinate federal activities in the
acquisition of certain water data (108). Implementation of the cir-
cular became the responsibility of the U. S. Geological Survey,
which established the Office of Water Data Coordination (OWDC).
The OWDC undertook the preparation of a Catalog of Information on
Water Data. Initially,- information was listed under one of four
categories, which include: water quality-stations, surface water
stations, groundwater stations, and results of aerial hydrologic
investigations. Input to the catalog consists of information supplied
by those federal agencies that acquire data either directly or in
cooperation with state or local agencies. Access to the catalog is
provided by OWDC through the use of indexes, such as "Index to
Catalog of Information on Water Data-Water Quality Stations, " 1966
ed. (108). The first catalog appears in 1966 for "water quality
stations" and other volume for "surface water stations" (109).
More water quality data and related water resource data are
being collected now than ever before. In addition to those collections
being made by the U. S. Geological Survey, the Division of Pollution
Surveillance of the Federal Water Pollution Control Administration
-------
88
is establishing additional water quality monitoring stations in the
national network. These two agencies of the Department of the
Interior are now making use of a new data storage and retrieval
system named STORET. Automatic data processing provides a rapid
and efficient means of storage and retrieval of data for visual exam-
ination and for further processing and analysis. STORET is part
of a large integrated system designed for the storage, retrieval,
processing, analysis, and reporting of water quality data. A wide
variety of data may be stored in the system, and subsequently sub-
jected to almost any desired statistical analysis for which a computer
program is prepared. It is anticipated that in the near future the
capabilities of the system may be expanded to include such things
as municipal water treatment and waste treatment^inventories, water
use data, state water quality standards and implementation plans,
and extended biological parameters of water quality importance.
Continuous instrumental monitoring. According to McCallum
and Stierli (110), water quality instrumentation for in situ monitoring
began in I960. First, a symposium "Water Quality Measurement and
Instrumentation" was held in I960 in Cincinnati (111). This brought
into focus the many facets of automated instrumentation systems
for in situ water quality surveillance. The same year the PHS
installed 65 battery-operated conductivity recorders at remote
locations in the Arkansas-Red River basins to continuously measure
salt pollution. By I960 a commercial system also had been developed
for continuous measurement of temperature, pH, specific electrical
conductivity, dissolved oxygen, turbidity, and sunlight intensity (HO).
The Division of Water Supply and Pollution Control, U. S.
Public Health-Service (now FWPCA), has provided continued stimulus
in development of such automated systems. It has also provided
leadership in developing specifications for operable systems (112).
Private manufacturers have developed comprehensive sensing systems.
One such system (line-operated) was installed in the Pautexent River
in 1963 by the U. S. Geological Survey (113). This was an eight-
parameter package system, with continuous recording by a multi-
point analog recorder. The cost, including housing structure, was
about $10, 000 per station. This system required only monthly
maintenanc e.
While the telemetry capability described above has been line-
operated, the development of a battery operated sens or-telemetry
system has been progressing (114), using commercially available
battery-powered sensors. Presently, continuous data recording
must be done by battery-operated strip chart recorders located in
the field. Two such stations were established for a water quality-
-------
89
hydrology modeling project (115). The existence of these stations
allows the evaluation and simulation modeling of diurnal variation
for several parameters (dissolved oxygen, temperature, conductivity,
pH). In addition, continuous monitoring permits evaluation of
stochastic variations in the measured parameters. These data,
coupled with conventional sampling, provide a well defined picture
of the water quality characteristics of a stream.
The value of continuous monitoring with respect to irrigation
return flow would have to be assessed in the light of the objectives
of the sampling network and available funds. Strategic placement
of such stations and judicious use of data could be of significant value
in evaluating the timing of shock loads and the effects of the pollutants.
Remote sensing. The application of remote sensing and
continuous monitoring of water quality changes have many possibilities
for use in identifying the source and concentration of pollutants in
return flow. Remote sensing, by use of infrared photography and
imagery, utilizing airplanes or satellites offers some new techniques
for pollution identifications. Robinove (116) reports that infrared
imagery has been used in hydrologic studies. Use of this technique
is illustrated by the detection of diffuse groundwater discharge having
a small temperature differential from the recipient water body. The
method is discussed more explicitly in terms of water pollution by
Van Lopik, Rambie, and Pressman (117).
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91
EFFECTS OF POLLUTANTS IN IRRIGATION RETURN FLOWS
ON OTHER BENEFICIAL USES
Purpose of this chapter is to relate the potential pollutants in
irrigation return flows to water quality criteria and standards estab-
lished for the protection of other beneficial uses, including the
rationale underlying the quantitative limitations imposed on the
various quality factors. Hopefully, by this comparison of irrigation
return flow quality and the quality needs of other legitimate water
uses, one may have a reference by which to measure the magnitude
of the pollutional problems identified with irrigation return flows.
As previously delineated, certain substances found in irrigation
return flows are considered to be pollutants in that when discharged
into a receiving water they may adversely affect subsequent use of
that water. Whether these potential pollutants actually do cause any
objectionable effects will depend, in part, upon the water quality
requirements of the downstream uses of these waters. Recognizing
that any substance if sufficiently dilute may not necessarily be a
pollutant, the nature of any adverse effects will also be dependent
upon the receiving water conditions; i. e. , whether a surface flow or
groundwater, and the extent of any dilution and commingling. Further,
the concept of water quality increment to the original water supply
quality, valuable in characterizing municipal and industrial waste
waters, generally is not useful for irrigation return flows due to
sampling and monitoring problems associated with the diffuse nature
of the return flow. Actual changes in water quality resulting from
irrigation use thus are not always subject to evaluation, and in some
instances are indistinguishable from water quality changes due to
natural phenomena.
The principal beneficial uses of water are listed below, not
necessarily in order of importance:
(a) Municipal water supplies
(b) Industrial water supplies
(c) Fish and other aquatic life
(d) Livestock watering
(e) Recreation and aesthetics
(f ) Irrigation water supplies
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92
Quality Requirements for Municipal Water Supplies
In evaluating water quality criteria for domestic use, two condi-
tions of the water must be considered: (a) its quality at the source of
supply, and (b) its quality at the tap or point of use (118). To be suit-
able for domestic purposes, i. e. , at the tap, the raw water supply
should be of such quality that it meets the Public Health Service Drink-
ing Water Standards (119) in all factors where absolute limits are
specified, or achievable by normal water treatment technology, i. e. ,
coagulation, sedimentation, filtration, and chlorination (6l). Table
28, taken from a recent report of the National Technical Advisory
Committee on Water Quality Criteria (4) suggests a list of water
quality criteria applicable to surface waters used for public water
supplies.
While originally applicable only to the quality of supplies used
by interstate carriers and others subject to Federal Quarantine
Regulations, the Public Health Service Drinking Water Standards have
been voluntarily accepted by most of the states as a basis for stand-
ards used for all public water supplies. The Standards delineate the
required physical, chemical, and bacterial quality for drinking water,
including a considerable amount of data on sampling techniques,
frequency, and methods of analysis as well as an appendix devoted to
background material and rationale.
Quantitative limits
Nature of limits, (a) Mandatory: limits which, if exceeded,
shall be grounds for rejection of the supply having adverse effects on
health; (b) recommended: limits which should not be exceeded when-
ever more suitable supplies are available at reasonable cost. Sub-
stances in this category, when present in concentrations above the
limit, are either objectionable to an appeciable number of people or
exceed the levels required by good water quality control practices.
Physical quality. Water should not contain material offensive to
the sense of sight, taste, or smell. Limits are recommended for each
of the following physical factors in terms of numerical values (118):
Turbidity (silica scale) 5 units
Color (standard cobalt scale) . . . 15 units
Threshold odor number not to exceed. . 3 units
-------
93
Table 28. Surface water criteria for public water supplies (4).
Physical:
Color (color units)
Odor
Turbidity
Mic robiological:
Coliform organisms
Fecal coliforms
Inorganic chemicals:
Alkalinity
Ammonia
Arsenic*
Barium*
Boron*
Cadmium*
Chloride*
Chromium, * hexavalent
Copper*
Dissolved oxygen
Fluoride*
Hardness*
Iron (filterable)
Lead*
Manganese* (filterable)
Nitrates plus nitrites*
pH (ranEEe)
Phosphorus*
Selenium*
Silver*
Sulfate*
Total dissolved solids*
(filterable residue).
Uranyl ion*
Zinc*
Organic chemicals:
Carbon chloroform extract* (CCE)
Cyanide*
Methylene blue active substances*
Oil and grease*
Pesticides:
Aldrin*
Chlordane*
DDT*
Dieldrin*
Endrin*
Heptachlor*
Heptachlor epoxide*
Lindane*
Mathoxychlor*
Organic phosphates plus
carb&mates*
Toxaphene*
Herbicides:
2,4-D plus 2.4,5-T, plus
2,4,5-TP*
Phenols*
Radioactivity:
Gross beta*
Radium-226*
Strontium-90*
Permissible
criteria
75
Narrative
do
do
10,000/100 ml**
2,000/100 ml**
(mg/1)
0.5 (as N)
0.05
1.0
1.0
0.01
250
0.05
1.0
> 4 (monthly mean)
> 3 (individual sample)
Narrative
do
0.3
0.05
0.05
10 (as N)
6. 0-8. 5
Narrative
0.01
0.05
250
500
5
S
0. 15
0.20
0.5
Virtually absent
0.017
0.003
0.04Z
0.017
0.001
0.018
0.018
0.056
0.035
0. 1***
0.005
0. 1
0.001
(pc/1)
1,000
3
10
Desirable
criteria
<10
Virtually absent
Virtually absent
<100/100 ml**
<20/100 ml**
(mg/1)
<0.01
Absent
do
do
do
<25
Absent
Virtually absent
Near saturation
Narrative
do
Virtually absent
Absent
do
Virtually absent
do
Absent
do
<50
<200
Absent
Virtually absent
<0. 04
Absent
Virtually absent
Absent
do
do
do
do
do
do
do
do
do
do
do
do
do
(pc/1)
<100
<1
<2
Permissible criteria—Those characteristics and concentrations of substances in
raw surface waters which will allow the production of a safe, clear, potable,
aesthetically pleasing, and acceptable public water supply which meets the limits
of Drinking Water Standards after treatment. This treatment may include, but
will not include more than, the processes described.
Desirable criteria — Those characteristics and concentrations of substances in the
raw surface waters which represent high-quality water in all respects for use as
public water supplies. Water meeting these criteria can be treated in the defined
plants with greater factors of safety or at less cost than is possible with waters
meeting permissible criteria,
*The defined treatment process has little effect on this constituent.
^^Microbiological limits are monthly arithmetic averages based upon an adequate
number of samples. Total coliform limit may be relaxed if fecal coliform
concentration does not exceed the specified limit.
***As pa rath ion in cholinesterase inhibition. It may be necessary to resort to even
lower concentrations for some compounds or mixtures.
-------
94
Chemical quality. In Table 29 recommended and permissible
concentrations of chemical substances are reproduced from the 1962
Drinking Water Standards. Considerations of radioactivity were
included in the 1962 standards for the first time, and in general the
standards require that added radiation shall not bring the total from
all sources above that specified by the Federal Radiation Council.
Bacterial quality. The bacterial standards, although founded
on statistical probability, represent maximum permissible rather
than recommended maximum limits. In effect, these requirements
limit the most probable number (MPN) of coliform organisms to one
per 100 ml. of water.
Summary of Effects of Potential Pollutants in Irrigation
Return Flows on Municipal Water Supplies
Quality factors
Total dissolved solids (salinity): 500 mg/1, recommended limit,
due to objectionable physiological effects and taste. The increase of
total dissolved solids or mineral content in irrigation return flows is
one of the major adverse effects on municipal water supplies. The
TDS of water is unaffected by conventional water treatment.
Hardness: 150-500 mg/1 as CaCO , suggested as limit (4, 118),
in view of such economic factors as cost of soap, water softening,
and incidental damage. The increase of hardness in irrigation return
flows is of major importance as it affects municipal water supplies.
One report (33) considers increases in hardness as the most impor-
tant single adverse effect contributed by irrigation return flows.
Chloride: 250 mg/1, recommended limit, due to objectionable
taste. The increase of chloride in irrigation return flows may be
several-fold and the resulting concentration maybe above the limits
in many cases. It is unaffected by conventional water treatment.
Sulfate: 250 mg/1 recommended limit due to objectionable
physiological affects -- laxative and taste. The readily soluble
nature of sulfate compounds in natural waters and the concentration
effect from irrigation use frequently cause this anion to be present
in return flows in concentrations well above the 250 mg/1 limit. It
is unaffected by conventional water treatment.
-------
95
Table 29. Chemical standards of drinking water (119).
The following chemical substances should not be present in a water
supply in excess of the listed concentrations where, in the judgment of the
Reporting Agency and the Certifying Authority, other more suitable sup-
plies are or can be made available.
Concentration
Substance . ,.
in mg/1
Alkyl Benzene Sulfonate (ABS) 0.5
Arsenic (As) 0. 01
Chloride (Cl) 250
Copper (Cu) 1
Carbon Chloroform Extract (CCE) 0. 2
Cyanide (CN) 0. 01
Fluoride (F) (See 5.23)
Iron (Fe) 0. 3
Manganese (Mn) 0. 05
Nitrate ' (NO,) 45
Phenols 0.001
Sulfate (SO4) 250
Total dissolved solids 500
Zinc (Zn) 5
In areas in which the nitrate content of water is known to be in excess
of the listed concentration, the public should be warned of the potential
dangers of using the water for infant feeding.
The presence of the following substances in excess of the con-
centrations listed shall constitute grounds for rejection of the supply:
f. , . Concentration
Substance . .,
in mg/1
Arsenic (As) 0. 05
Barium (Ba) 1. 0
Cadmium (Cd) . 0.01
Chromium (Hexavalent)(Cr ) 0. 05
Cyanide (CN) 0.2
Fluoride (F) See below
Lead (Pb) 0. 05
Selenium (Se) 0. 01
Silver (Ag) 0. 05
Fluoride--When fluoride is naturally present in drinking water,
the concentration should not average more than the appropriate upper
limit. Presence of fluoride in average concentrations greater than two
times the optimum values shall constitute grounds for rejection of the
supply.
Where fluoridation (supplementation of fluoride in drinking water)
is practiced, the average fluoride concentration shall be kept within the
upper and lower control limits.
Annual average of Recommended control limits -
maximum daily air Fluoride concentrations in mg/1
temperatures 2
50,0-53.7
53.8-58. 3
58.4-63. 8
63.9-70.6
70.7-79.2
79.3-90.5
Lower
0.9
0.8
0.8
0.7
0.7
0.6
Optimum
1.2
1. 1
1.0
0.9
0.8
0.7
Upper
1.7
1.5
1. 3
1.2
1.0
0.8
2Based on temperature data obtained for a minimum of five
years.
-------
96
Sodium: May be harmful to persons suffering from cardiac,
renal, or circulatory diseases (118). Since sodium salts are readily
soluble, concentrations expected in return flows may be several
hundred milligrams per liter.
Nitrate: 45 mg/1 as NO , recommended limit due to possibility
of intantile nitrate poisoning (methemoglobinemia, cyanosis). There
appears to be conflicting opinions with respect to the importance of
return flow contributions of nitrate, but many recent reports (30, 66,
120, 121, 122, 123, 124) indicate that concentrations, in the limits
prescribed, are appearing in both surface and groundwater return
flows. It is usually not removed by conventional water treatment.
Phosphate: Causes algae blooms, tastes and odors, slime
growths, and may adversely influence the coagulation process. It is
present in most return flows in sufficient concentrations that it is not
limiting to aquatic plant blooms although the content in the return flow
may be even less than in the irrigation water.
• Turbidity: Five units are the recommended limit. The major
consideration is an aesthetic one, and that of consumer acceptance.
Varying turbidity must be expected in return flows, but generally
turbidity is not considered a major problem. Readily removed by
conventional water treatment.
Tastes and odors: A threshold odor number of 3 is recommended
as a limit, but it should be limited to consumer acceptance and good
aesthetics. Contributing causes of tastes in irrigation return flows
may be associated with the mineral content (TDS, chloride and sulfate).
Nutrients (nitrate and phosphate) found in most return flows are suf-
ficient to support objectionable aquatic growths and are indirectly
responsible for tastes and odors. Decomposition products of organic
debris in return flows may also contribute. The problem may be
further aggravated by chlorination.
Color: Recommended limit is 15 units. Con'sumer acceptance
and aesthetics again are the major considerations. Generally, an in-
crease in color is noted in surface return flows. However, the prob-
lem is not of major importance. Conventional water treatment will
adequately reduce color.
Coliform organisms: Less than 1/100 ml is mandatory limit for
protection of public health. The presence of coliform organisms in
return flows may result from a variety of coliforms of soil origin or
municipal and industrial effluents present in the original supply. In
either case, generally no problem occurs in the subsurface return
flows due to the excellent removals by the soil mantle. Significant
-------
97
coliform concentrations may persist in surface return flows, but
limited data indicate that they are usually within the removal capabil-
ity of conventional water treatment.
Temperature: Increased temperature adversely affects palat-
ability, and accentuates tastes and odors. Limited data suggest that
there may be a slight increase in temperature associated with surface
return flows and that there may be a slight decrease in subsurface
return flows.
Pesticides: No limits established but the objective is to have
none. An indirect measure of carbon chloroform extract at 0. 2 mg/1
is a guide. Toxicity, taste and odor are key considerations. There
is nothing conclusive on this subject yet. Perhaps the problem is
summarized best by recent FWPCA report (40):
Numerous studies have shown that repeated appli-
cation of pesticides, particularly of the chlorinated
hydrocarbons, has resulted in residues of some of these
compounds being found in soil layers corresponding to
plow and cultivation depths. These compounds are
generally resistent to biological degradation. The ex-
tended persistence of these coupounds has increased
the chance of water contamination. Current knowledge
as to the extent and amount of pesticide residues in
water resources is meager, and knowledge about the
significance of these residues and their effect on water
supplies even more so. The committee which reviewed
and updated the USPHS Drinking Water Standards in 1962
concluded that the information available at that time was
not sufficient to establish specific limits for pesticidal
chemicals in drinking water. Only the concentration
that will produce a perceptible odor in water has been
determined for several pesticides (Table 30).
A study conducted by FWPCA personnel at the
Taft Sanitary Engineering Center assessed the effect
of various treatments on concentrations of dieldrin,
endrin, lindane, DDT, 2,4, 5-T, and parathion from
water. The study indicated that, while each part of
the treatment plant may have potential for reducing
certain pesticides, no effective practical treatment
is known for large volumes of water containing pesti-
cides.
-------
98
Table 30. Threshold odor concentrations of pesticides and solvents
in water (40).
_. ,. . , Threshold Odor
Pesticides _
Concentration
in ppm
Parathion (technical grade) . 003
Parathion (pure) .036
Endrin . 009
Lindane .330
Formulation components
Sulfoxide (synergist) .091
Aerosol OT (emulsifier) 14. 600
Commercial Solvents:
Deodorized Kerosene .082
Solvent 1 - 016
Solvent 2 13.900
Solvent 3 .090
Source: U. S. Department of Agriculture report prepared for FWPCA.
General discussion
The water quality factors in irrigation return flows considered
of most significance to municipal water supplies are total dissolved
solids, chlorides, sulfates, and hardness. While technology is avail-
able to remove or reduce the concentrations of these constituents, only
hardness is capable of being removed by what is currently considered
conventional water treatment processes within the range of economic
feasibility. (There may be a slight reduction of TDS result from hard-
ness removal. )
Quality factors considered of secondary significance, primarily
because their effects are presently difficult to assess, are nitrates,
phosphates and pesticides. Again, removal of these constituents is
not effective by conventional treatment means.
Evidence indicates that the remainder of the potential pollutants
discussed in this section are not serious water quality degradation
factors for municipal use, either because of their low concentration
and intensity or ease of removal by conventional treatment.
-------
99
Quality Requirements for Industrial Water Supplies
By far the most varied spectrum of quality requirements of
beneficial users is found in industrial water needs (61). Water is
used as an ingredient with other raw materials in the finished product,
as a buoyant transporting medium, as a cleansing agent, as a coolant,
and as a source of steam in heating and power production.
Two examples of industry's varied water quality requirements
are presented in Table 31 which summarizes preferred quality limits
for certain process waters, and in Table 32 which reports quality
characteristics of raw waters used as sources of supplies by various
industries. It is impossible to organize into a single set of standards
the quality requirements of water used for each of the many different
industrial processes. Such quality requirements differ far too much
to allow any broad generalization or simplification (118). Further,
quality requirements within the same industry may vary considerably,
depending upon the technology utilized.
Von Frank and Fawcett (125) point out that water used for cool-
ing accounts for about 90 percent of the total supply withdrawn by the
manufacturing and thermal-electric power industries combined, yet
despite this massive use quality criteria for industrial cooling waters
have received relatively little attention. This lack of rigorous criteria
for industrial cooling water is, perhaps, not surprising when one views
its wide variety of supply.
Regarding the lesser quantities of process waters used by indus-
try, Partridge (125) states:
The quality of water adequate for use in specific
process operations throughout industry ranges from
untreated surface water carrying pollution from natural,
municipal, or industrial sources to completely demineral-
ized water. A similar broad spread is found within many
individual plants with varied process steps.
To write general criteria for industrial process
water representing other than the lowest common
denominator accordingly seems useless. The mini-
mum conditions applicable to all waters at all places
at all times of the Ohio River Valley Water Sanitation
Commission (ORSANCO) provide an example of such
general criteria seasoned by 17 years of experience.
-------
Table 31. Preferred limits for several criteria of water for use in industrial processes (123).
O
O
Turbidity,
max
Aluminum (hydrate wash)
Baking
Boiler feed
0 to 150 psi
150 to 250 psi
250 to 400 psi
400 to 1000 psi
> 1000 psi
Brewing
Carbonated beverages
Confectionery
Dairy
Electroplating and finishing, rinse
Fermentation
Food canning and freezing
Food processing, general
Ice manufacturing
Laundering
Malt preparation
Oil well flooding
Photographic process
Pulp and paper
Groundwood paper
Soda and> sulfate pulp
Kraft paper
bleached
unbleached
Fine paper
Sugar manufacture
Tanning operations
Textile manufacture
10
80
40
5
2
10
2
low
10
10
low
50
25
40
100
10
20
0.3
25
TaBte H
Color, and
max odor,
mm max
max
10 low
8.0
8.4
9.0
9.6
10 low 6.5 7.0
10 low
low 7. 0
none none
low
low 7. 5
10 low
6.0 6.8
low
7.0
low
30
5
25
100
5
100 6.0 8.0
0
70
Dissolved
Solids, Oxygen,
mg/1 max ml/1
low
3000 <2
1500 <0. 2
2500 0
50 0
<0. 5 <0. 05
1500
100
500
low
850
170 to 1300
500
250
300
500
200
low
Note: The values in this table are derived from summaries in the comprehensive review by McKee and
Wolf. They should be used only after study of these summaries and of the original references
cited in them.
-------
(Unless otherwise
indicated.
units are mg/1 and values are maximums. No one water will have all the maximum values shown. )
Boiler Make-up Water
Characteristic
Silica (SiO,)
Aluminum "(Al)
Iron (Fe)
Manganese (Mn)
Copper (Cu)
Calcium (CaJ
Magnesium (Mg)
Sodium fc Potassium (Na+K)
Ammonia (NH3I
Bicarbonate (HCO,)
Sulfate (SO4)
Chloride (Cl)
Fluoride (F)
Nitrate (NO})
Phosphate (PO.)
Dissolved Solids
Suspended Solids
Hardness (CaCOj)
Alkalinity (CaCOj)
Acidity (CaCOj)
pH, units
Color, units
Industrial Utility
0-1500
psig
ISO
3
80
10
600
1.400
19,000
35, 000
15,000
5.000
500
1,000
1,200
Cooling Water
Fresh
700-5000 Once
P'ig Through
ISO
3
80
10
600
1.400
19.000
50
35, 000
15,000
5,000
SOO
1,000
1,200
50
3
14
2.5
500
600
680
60C
30
4
1.000
5,000
850
SOO
0
5.0-8.9
Process
Water
Brackish Textile Lumber Pulp b Paper Chemical Petroleum
Industry Industry Industry Industry Industry
Make-up Once- Make-up SI{. ^ 4 4
Recycle Through Recycle
150
3
80
10
500
600
680
SOO
30
4
1,000
15,000
850
500
200
3.5-9.1
1,200
25
1.
25
, 0 1.0 0.3
0.02 0.02 1.0
1,200
180
2,700
22, 000
S
35,000
250
7,000
ISO
0
5.0-8.4
0.5
1,200
180
2,700
22, 000
5
35,000 150
250 1,000 >
7, 000 120
150
0
5.0-8.4 6.0-8.0 5-9
50
2.6 5
2
50
15
Prim. Metals Food fc
Leather
Industry Kindred Products Industry
S1C-33 SIC-20 SIC-31
In general, the
quality of raw
surface supply
should be that
prescribed by
the NTA Committee
200
100
600
850
200 ' 500
1,080 2.500
10,000
475 1,000
500
4.6-9.4 5.5-9.0
360 500
220
85
230
480
570
1,600
1.2
8
3,500
5,000
900
6.0-9.0
25
on Water Quality
Requirements
Public Water
Supplies.
500
1.500
3,000
1.000
200
75
3-9
for
Organics
Methylene blue active
substances
10
1.3
1.3
1.3
Carbon tetrachloride
extract
100
No floating
oil
No floating
oil
100
30
Chemical oxygen demand
Hydrogen sulfide (H^S)
Temperature, °F
100 500 100 200
4 4
120 120 100 120 100 120
s
95
100
May be < 1, 000 for mechanical pulping operations.
Water containing in excess of 1,000 mg/1 dissolved solids.
% No large particles < 3 mm diameter.
One mg/1 for pressure up to 700 psig.
Applies to bleached chemical pulp and paper only.
Note: Application of the above values should be based on analytical
methods in ASTM Manual on Industrial Water and Industrial
Waste Water (2) or APHA Standard Methods for the
Examination of Water and Waste Water (1).
-------
102
These minimum conditions essentially state that such waters
shall be free from objectionable settleables, floatables, toxic sub-
stances, color, odor, and other nuisances. Beyond such minimums
are the criteria established by industry for specific operations.
In conclusion, industry likely will continue to treat available
water supplies in accord with specific needs. Fortunately, water
treatment technology available today permits use of a water supply of
almost any quality to produce water suitable to a given industrial use,
and while the cost of such treatment may be high, it is usually a small
part of the total production and marketing costs (4).
Effects of Potential Pollutants in Irrigation Return Flows
on Industrial Water Quality Requirement's
It would be difficult to concisely relate the effects of potential
pollutants in irrigation return flows to industrial water quality require-
ments. However, a qualitative evaluation follows:
Potential Pollutants
Total dissolved solids
Hardness
Chlorides
Sulf ate s
Sodium
Alkalinity
Nitrate
Phosphate
Tastes and odors
Turbidity
Color
Temperature
Coliform organisms
Effects
Affect many industrial uses adversely
and probably have the most significant
effect due to irrigation return flows.
Removal by special treatment is pos-
sible, although costly.
May be responsible for the development
of algal growths and bacterial slimes
which can adversely affect cooling water
use in particular, as well as process
waters such as used by the food and
drink industries. Effects can be con-
trolled by conventional treatment.
Objectionable for many industrial proc-
ess waters, but readily removed by con-
ventional treatment. Not significant to
cooling water use.
Not significant.
Little indication of any serious effects on
process water uses, although a potential
problem could exist. Probably of no sig-
nificance to cooling water use.
-------
103
Effects of Return Flow on Fish and Wildlife
The problem is complex. It involves not only changes in water
quality, but changes in quality of the ecological system affected. The
environment includes a given water flow, light, temperature, and
water quality regimen. A change in any of the four qualities can pro-
duce an effect on the aquatic biota. If the diversion for irrigation is
a significant portion of the stream flow, the effect of the reduced flow
on the biota below the diversion is immediate and significant. The
environment is changed; therefore, the life adapted to the previous con-
ditions must be changed. In the case of an irrigation storage dam, the
impounded water greatly changes the quality of that environment in addi-
tion to changing the volume of flow in the stream channel below. Below
the dam there may be a more even flow. Before dam construction, the
channel may have varied from flood flow to dry bed. Above the dam a
lake-type environment replaces a stream environment.
Should the source of irrigation waters be from a hydrologic sys-
tem other than the system in which the receiving waters are located,
the changes which could occur in the receiving waters still apply, and
in addition, the changes in quality represented by the differences be-
tween the source waters and the receiving waters from the two separate
systems is also a fact which must be considered. Whether irrigation
practices involve a single watershed or several watersheds, there can
be a marked effect of those practices on an ecological system in the
receiving waters.
All factors of irrigation practice should be considered in assess-
ing the effect of irrigation return flow on an ecosystem. For example,
water diversion on a rainbow trout stream may alter the stream below
the diversion from an ideal rainbow trout stream to one more suited to
brown trout. The return flow would have an effect on whatever system
developed in the receiving waters in place of the rainbow trout system
Diversions may upgrade water quality below the structure. The Flam-
ing Gorge Dam, for example, changed the quality of Green River from
sediment-laden water suitable only for minnows and suckers to clear
water suitable for rainbow trout.
Organisms respond to singular qualities in the water and also to
combinations of these qualities (126, 127). For example, chlorides may
act synergistically with fluorides to produce an effect on fish that neither
chloride nor fluoride produces alone (126). The effect of calcium on the
toxicity of boron, zinc, and copper is well documented (118, 128, 129).
-------
104
Chemical effects
Different concentrations of various compounds or elements will
affect different wildlife species as well as individuals within the species
in a variety of ways. Also, the concentration of a given chemical qual-
ity required to produce a toxic or lethal effect on the adult of a species
may be considerably more than the concentration required to produce
the same effect on the young of that species. Among the invertebrates,
different stages in the life cycle are differentially susceptible.
As Eldridge (33) observes, so many factors influence the effects
of water constituents on aquatic life that a concise statement of specific
requirements is impossible. Adverse water quality'may interfere with
the migration of fish, kill them, create pathological conditions, inter-
fere with spawning, or with the production of an adequate food supply.
Of the compounds listed as significant in irrigation return waters, only
the compounds of boron, fluorine, sulfur, and iron occur in concentra-
tions sufficiently great to be toxic to fish or to other components of the
aquatic ecosystem. Of the elements, the heavy metals which for the
most part appear as trace elements are universally toxic to both plants
and animals when sufficiently concentrated. Zinc, for example, is
toxic to fish in concentrations as low as 0. 3 mg/1; lead in concentra-
tions as low as 0. 1 mg/1; silver as low as 0. 005 mg/1.
An increase of the calcium concentration when return flow mixes
with receiving waters may affect the essential carbonate buffer system,
resulting in pH changes. Rapid changes in pH cause losses in the eggs
and fry of fish (130). Unbalancing the carbonate buffer system may
also reduce the carbon available for plants, particularly algae in the
aquatic system; thus, primary productivity can be reduced (4). Boron
may also occur in amounts toxic to vascular plants in the aquatic sys-
tem (128).
Both nitrate and phosphate- concentrations may be affected by
irrigation return waters. Thome and Thorne (91) present data indi-
cating that decreases may occur. Since nitrates and phosphates serve
as nutrients, particularly in the production of plants, either enrich-
ment or deprivation can yield startling results on the plant communi-
ties in streams or lakes. Increased production may have deleterious
effects on the habitat and food organisms of fish. High levels of these
nutrients favor growth of Sphaerotilus, algae and rooted aquatic plants
(131).
Little data indicate that organic loading is increased significantly
as a result of irrigation return flows. However, when organic loading
is increased, it also can serve as a nutrient. Organic material has a
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105
direct effect on the production-of such bacteria as Sphaerotilus which
are nourished directly on dissolved organics. An increase in plant
production in streams tends to clog streams with plant material and
debris. Subsequent oxidation of plant material decreases oxygen con-
centration in water (132). Once oxygen concentration is reduced in
streams, decomposition of organic material produced by the enrich-
ment will continue anarobically and may result in release of such
noxious gases as hydrogen sulfide, which is toxic to a variety of
aquatic organisms (133).
Increased production of plant material may result in production
of certain species of algae which produce toxins as secretions that
maybe toxic to invertebrates and vertebrates alike (33). Invertebrate
population in streams are changed in diversity by rapid growth of
certain algae. Many invertebrates are sensitive to decreases in dis-
solved oxygen concentration in the water; and where nutrient enrich-
ment has increased organic production, decrease in oxygen concentra-
tion is not uncommon. Wnen such change occurs in the environment,
the invertebrates with high oxygen requirements are eliminated from
the system and replaced by invertebrates of lower oxygen requirement,
thereby changing the ecological system and affecting the species feed-
ing upon the invertebrates.
This effect of enrichment on the animal community also occurs
among plants. Enrichment induces changes in the production of plant
materials including algae, and as a consequence, dominance in the
planktonic algaes. Enrichment also encourages growth of rooted,
vascular aquatic plants.
Optimum range of nitrate concentration for aquatic plant produc-
tion is between 0. 9 and 3. 3 mg/1; for phosphate between 0. 9 and 1. 8
mg/1 (134). Thorne and Thorne (91) show phosphate concentrations
in the irrigation waters of Utah to range between 0.2 and 0. 6 mg/1.
Nitrates above 17 mg/1 may cause inhibition of chlorophyll formation
(134).
Pesticide effects
Toxicity of pesticides depends on many different environmental
factors, all of which vary considerably in irrigation return flows.
These include temperature, pH, the amount of silt present, calcium,
magnesium, the species involved, age of organisms, and other pesti-
cides present (130).
Pesticides are concentrated in particulate matter or detritus and
utilized as food by the invertebrates. Once invertebrates feed on this
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106
detritus, the pesticides are concentrated. Concentrating effects up
to 10, 000-fold have been found in some invertebrates. Lethal levels
of all pesticides have been established and are presented in Water
Quality Criteria (118) and in the Report of a Committee on Water
Quality Criteria (4). Even in extremely low concentrations, pesti-
cides affect all levels of the ecosystem and sublethal doses produce
deleterious effects. Fish and other wildlife have been killed by pesti-
cides reaching streams from sprayed areas (135, 136). Residues of
pesticides have been found in most organisms examined (137). Keith
and Hunt (135) observe that fish exposed to residues in water absorb
pesticides directly through their gills or/and skin; or if residues are
present in feed, the pesticides are ingested.
Chlorinated hydrocarbons are very resistant to degradation.
Heptachlor, for example, was detected 25 months after application
(130). Dilution of chlorinated hydrocarbons apparently is not an ade-
quate means of avoiding adverse effects in the aquatic environment.
Since the chlorinated hydrocarbons are long-lived, they can persist
in the environment in diluted quantities; and eventually they may be
concentrated in animal tissues (46).
At sublethal levels, pesticides may produce toxic effects on fish
that affect the population's viability, and it is possible that pesticides
may also affect enzyme' activity and cell permeability within the cells
of organisms. Thus, the transfer of nutrients into and within the
organism maybe greatly influenced by pesticide-caused damage.
Eldridge (33) observes that the frequency and amplitude of electrical
output of certain fish were reduced by pesticides in general. Sublethal
levels of toxaphene were observed to produce effects on fish which
resulted in heightened responses to external stimuli, hyper sensitivity,
and certain behavioral changes (138). Dieldrin reduces predation on
young of guppies by the adults, and other changes in their feeding
habits (130). Prolonged exposure to low doses of dieldrin causes
lowering of resistance to disease (139). It also increases excitability
and respiratory difficulties in fish (130). Low doses of DDT interfere
with the normal thermal acclimation mechanism of fish (140). DDT
tends to collect in fat of eggs of developing fish where it produces no
effect until such time as the yolk materials are absorbed (141). The
DDT then is released, having a lethal effect on the young fry, and it
is inferred that the viability of sperm is reduced in males receiving
sublethal doses.
A second class of pesticides are the organophosphates, which
are highly toxic, but less resistant to degradation. Parathion is lethal
to bluegills at concentrations as low as 0. 2 mg/1 and to cutthroat trout
at 0. 1 mg/1. If exposure to the pesticide is transitory or momentary,
the fish can recover; however, it does take a relatively long time --
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107
as long as three weeks to return to normal (46). Certain herbicides
are very toxic to invertebrates. Diquat is particularly toxic to
cladocerans. DDD has a low toxicity for fish, but very high for
chironomids (130).
Among plants, dieldrin is rapidly absorbed by aquatic algae,
where it is concentrated. Since algaes in the aquatic system are the
base of the food chain, they are a constant source of contamination.
Dieldrin also tends to affect the plants' physiology. For example,
93 mg/I over a 24-hour period affected the respiration of algae (142).
Apparently many pesticides are concentrated by plants and invertebrates
in aquatic systems and thus provide a constant source of contamination
in higher levels of the food chain, such as fish (135).
Osmotic effects
All salts in solution, as well as any dissolved organics, contrib-
ute to osmotic concentration in the return flow. Since virtually all
aquatic organisms are hoeosmotic, the amount of work required by
these organisms to maintain their osmotic balance is altered with
changing osmotic concentrations in water. The effects of changes in
osmotic concentrations in water on respiration of fish are not clearly
understood, although changes do occur (130). Less than 1,000 mg/1
salts in drain water has little effect on fish and wildlife (21). Yet
changes as small as 20 mg/1 limit the growth of certain plant species
(4). Christiansen and Low (143) observed that germination, growth,
seed and tuber production decreased as salinity increased. Substantial
reductions in growth were observed at substrate levels exceeding 12
mmhos. Fresh water produced the best growth in all plants with the
exception of the Sago Pond Weed tubers which showed greatest growth
in slightly saline conditions (3,000 mg/1). Miller (21) lists salt toler-
ances for several species of aquatic plants: up to 7,000 mg/1 for Sago
Pond Weed, 9, 000 mg/1 for Horned Pond Weed, 45, 000 mg/1 for
Widgeongrass, 80, 000 mg/1 for Shoalgrass. Chapman (144) indicates
a similar relationship with osmotic concentrations for aquatic plants
throughout salt marshes and salt deserts of the world. Bolen and
Ungar (146) add that as salt concentrations increase, greater competi-
tion is offered by halophytic plants.
It is apparent that any increases in osmotic concentrations of
water will result in changes of metabolic rates of organisms. Since
plants and invertebrates exhibit limits to their euryhalinity, changes
in the structure of the community can occur. The base for production
can thus change and the quality of production of the entire system can
also change. This may result in changes of fish species and produc-
tion.
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108
Sediment effects
Where surface irrigation return flows are common, the sediment
load may be periodically high (33). The effect of diversion structures,
particularly dams, is to serve as settling basins for sediments and
stabilization of stream flows below the structure, resulting in reduced
corrosive action and a consequent reduction in sediment load. Where it
occurs the effect of silting or sediment loads in waters can be marked
on aquatic populations.
Tebo (147) observed 50 percent egg mortality in silt-covered
gravel, as opposed to clean gravel. The effect of sedimentation
on spawning beds is essentially to limit circulation of clean water about
the eggs, with a consequent mortality or pathological condition (133).
In larger fish, the silt or sediments tend to abrade and coat or clog
gills of many species. This results in suffocation or an increase in
the probability of secondary infections (148, 149) . In migratory
species, such as the salmon and the steelhead trout, streams with
exces*sive silt tend to repel fish migration (133).
Cordone and Kelley (140) also observed that 41 to 63 percent
fewer invertebrates were found in silty streams than in clear streams.
The invertebrates were either smothered or destroyed by molar action.
Larvae of the invertebrates are prevented from attaching to the bottom,
and in silty streams may be carried away more rapidly during flood
stages than in streams where rocks provide shelter. The effect of
sedmients on algae and rooted plants is one of destruction by molar
action. Sediments on underwater plant parts also exclude gaseous
exchange with water (150). Sediments also reduce light penetration
in water. The reduction of light results in disruption of the photo-
synthetic reaction and the production of plant materials. Any organic
compounds and nutrients carried from sediment-laden waters to clearer
waters downstream may encourage algae blooms (151). Even low
amounts of silt for short periods of time may adversely affect primary
productivity of streams (133).
Temperature
Depending upon the area, the temperature of return flow water
may be several degrees centigrade greater or lesser than the source
water. There is a marked effect of temperature changes on fish and
other aquatic organisms. Fish adapted to cold water are unable to
adapt to sudden increases in temperature, because of a thermal shock
which causes behavioral changes and a general increase in lethargy.
Fish are often disoriented, which may influence their migration (152).
Changes occur in metabolic rates and oxygen consumption. Huet (153)
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109
notes an increased oxygen requirement for fish subjected to rapid
changes in temperature.
Temperature changes may cause changes in timing of the stages
of development as well as in reproduction of fish, causing a feed prob-
lem and increased mortality. In addition, eggs and fry have far
narrower optimum range for temperatures than does the adult fish (152).
Life cycles of the invertebrates are often coltrolled by tempera-
ture variation. Certain species reproduce, hatch, pupate, and emerge
at specific temperatures. There is also a minimum temperature re-
quirement for many species during the winter months so that their life
cycles can be completed. Increase in water temperature in early spring
may cause emergence when air temperature is too cold for survival of
the adults (152).
An increase in ambient temperature may induce changes in plant
species dominance. When this occurs, a change in the base of the food
chain occurs and the entire system is again affected either qualitatively
or quantitatively. Temperature also causes a physical effect on the
environment in terms of gas solution. This is particularly serious
with oxygen and carbon dioxide concentrations, for as temperatures
increase the dissolved gases decrease.
Interaction effects
As Eldridge (33) points out, the complex relationship of aquatic
life to irrigation return flow waters is such that it is difficult to assess
effects without resorting to in situ bioassay efforts. Interactions be-
tween chemical and physical qualities can affect individuals within an
ecosystem as well as the system itself.
The toxicity to fish of such elements as boron, copper, zinc and
other heavy metals is affected by the calcium and magnesium concen-
tration in waters (118). Neuhold and Sigler (126) and Huet (154) report
that chlorides in water decrease the toxicity of fluorides to rainbow
trout, and that soluble calcium in water likewise decreases the toxicity
of fluoride. Katz et al (130) observed that increasing acidity tends to
increase the toxicity of heavy metals to aquatic organisms. The toxicity
of many pesticides is also influenced by the pH and the calcium and
magnesium present (130). Street et al (127) observed that rainbow
trout can tolerate dieldrin in higher concentrations when DDT is present.
Chemicals in the environment also interact with physical qualities
to produce quite different effects. The toxicity of any of the chemicals
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110
is related to the temperature. As temperatures increase, generally
the toxicity increases because of an increased metabolism of the
organisms (162). Silt and organic matter affect pH and oxygen levels
in water and thereby produce an effect on the system or/and on individ-
uals within the system. The presence of silt at times increases the
toxicity of certain of the heavy metals (133). The toxicity of heavy
metals is influenced by temperature and also by dissolved gases in
water (155). Increases in nitrates and phosphates produce plant
materials, which in turn reduce the light penetration and, upon sene-
scence and decay, utilize oxygen in the water, resulting in a subdued
light environment that is basically anaerobic in nature.
Water temperature influences the solubility of various chemicals.
As temperature of the water increases, many of the salts become more
soluble, thereby increasing the amounts which might be absorbed by
aquatic organisms. Physical interactions which are important to the
existence and functioning of an aquatic ecological system may also
occur.
Interaction effects should be an extremely important part of any
study of irrigation return flow effects on fish and wildlife. This is
perhaps why in situ bioassay techniques have been about the only tech-
niques effectively employed in the measurement of the effects of irri-
gation return flow on aquatic organisms.
Water Quality Requirements for Aquatic Life
Pertinent requirements for maximum fish production have been
published (4, 32). These include: temperatures of 60 to 68 F;
hydrogen ion concentration from 6.7 to 8. 6; dissolved oxygen con-
centration above 5 mg/1; specific conductivities at 25 C; 158 to 500
micromhos or 1,000 to 2,000 micromhos in alkaline areas; dissolved
solids up to 3, 000 mg/1, providing that none are toxic and all are
physiologically balanced; suspended solids or turbidity such that the
millionth intensity level for light will not be less than five meters;
carbon dioxide not above 30 mg/1; ammonium not over 1. 5 mg/1; DDT
concentrations less than 0. 1 mg/1; fluorides not over 100 mg/1; nitrates
and phosphates not toxic; calcium, magnesium, sodium, sulfate, and
chlorides apparently not toxic in normal conditions.
The Committee on Water Quality Criteria (4) excludes all settle-
able material and limits the turbidities in warm water streams to not
over 50 Jackson Units, and in cold water streams to not over 10 Jack-
son Units. Total dissolved solids are not to exceed 1, 500 mg/1 sodium
chloride equivalents. Calcium must not increase enough to precipitate
the carbonate, thus unbalancing the carbonate buffer system. Zinc is
-------
Ill
not to exceed U. 01 of the 96-hour TLm. if the zinc concentration is
continuous; copper, not more than 0. 1 of the 96-hour TLm or 1/30
of the TLm for 24 hours; pH must not go below 6 or above 9. Phos-
phates are not to exceed 100 mg/1 in streams. Pesticides are to be
0.1 to 0. 01 of the 48-hour TLm in streams. Maximum allowable
temperatures are 93 F for catfish and 80 F for catfish eggs; 68 F
for salmonids, 55 F for salmonid eggs. Dissolved oxygen require-
ments for streams should never be below 7 mg/1 for spawning or 4
mg/1 when fish are not spawning, and this level only for short periods.
Cold streams must be near saturation if eggs and fry are to develop.
Presumably if the criteria suggested by Eldridge and by the Com-
mittee for Water Quality Criteria are met, no serious effects •will occur
on the fish and wildlife in the area. These criteria, however, appear
to be developed for fish and are not oriented to the ecosystem. It is
quite possible that the minimum levels which are presented could still
produce significant effects on the production within any given system.
Conversely, the levels .mentioned may be transversed in either direc-
tion without producing significant changes in the ecosystem. The levels
listed here may be a reasonable reference but not inflexible.
Water Quality Requirements for Farmstead and Livestock
Where water on farmsteads is used in the household and/or for
washing dairy equipment, etc. , it should meet drinking water standards,
Ideally, water for livestock would also meet these standards. It is
generally recognized, however, that animals are exposed to many
pollutants and it is not practical to attempt to provide water that meets
all the standards for potable water.
Of the many possible pollutants in water, those associated with
return flow from irrigation seem to be limited to the general soluble
salts and nitrates in subsurface drainage waters. Seldom, if ever,
would the nitrate in drainage waters exceed the limit for animals.
Drainage from surface flow may, in addition to the above, contain
pathogenic organisms and pesticides, with the pesticides possibly
originating as a result of irrigation agriculture. These would appear
in the water only sporadically.
Quality for livestock
The tolerance of animals to salt and other pollutants in water
depends on many factors, such as species, age, physiological condi-
tion, content of the feed, as well as the kinds and amounts of salts.
Apparently animals can tolerate more salt than can humans and vary
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112
in tolerance to different substances. There is also evidence that they
can within limits adjust to saline waters. The general quality require-
ments are reviewed and discussed in publications (4, 6l, 118).
A tentative guide for evaluating the quality of water for livestock.
is given in Table 33. McGauhey (61) reports his conclusions for salt
tolerance:
Indications are that the maximum concentrations
of salts that can be tolerated by domestic animals with-
out danger of injury by osmotic effect lie between 15, 000
and 17, 000 mg/1. However, a value of 10, 000 mg/1 is
more realistic for sheep and perhaps 7, 000 mg-/l for milk
cows in production. Obviously, these values are con-
siderably higher than can be tolerated in humans.
The Committee on Water Quality Criteria (4) concluded that in
nearly all cases the decisive factor affecting suitability is the amount
of sodium, potassium, magnesium, and calcium, and that the adverse
effects are roughly proportional to the total of these minerals in ex-
cess of 1, 000 mg/1.
Because plants may supply enough nitrate to poison animals,
low concentrations of nitrate in the water are recommended. There
seems to be no general agreement as to the acceptable maximum.
After an extensive review of literature (6l), a range of 200 - 400 mg/1
was suggested.
Pesticides are largely absorbed by soils and do not pass through
soil with the leaching waters. It is possible to get toxic amounts in
the return flow from surface drainage. More likely sources are acci-
dental contamination of water supply by spillage, washing of equipment,
discharge of a surplus, and from applied materials falling into water-
ways. It is reported (4) that to date no recorded example has been
found of toxicity to livestock due to pesticide contaminants in water
supplies in general.
Even if specific toxic limits were established for all animals and
for each pollutant, the assay problem for continuing surveillance would
be considerable for each water source inasmuch as the toxicants would
likely occur only at sporadic intervals. It is suggested (4, 118) that
the presence of fish in a source of water for livestock may be an excel-
lent protective measure of toxicity, for evidence indicates that fish
have a lower tolerance to various pesticides than does livestock.
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113
Table 33. Guides to the quality of water for livestock (61).
Quality Factor
mg/1
Threshold1
Concentration
Limiting2
Concentration
Total dissolved solids (TDS)
Cadmium
Calcium
Magnesium
Sodium
Arsenic
2500
5
500
250
1000
1
5000
1000
500
2000
Bicarbonate
Chloride
Fluoride
500
1500
1
500
3000
6
Nitrate as NO,
Nitrite
Sulfate
Range of pH
200
none
500
6.0-8. 5
400
none
1000
5. 6-9. 0
threshold values represent concentrations at which poultry or
sensitive animals might show slight effects from prolonged use
of water. Lower concentrations are of little or no concern.
2Limiting concentrations based on interim criteria, South Africa.
Animals in lactation or production might show definite adverse
reaction.
3Total magnesium compounds plus sodium sulfate should not exceed
50 percent of the total dissolved solids.
-------
Quality Requirements for Recreational and
Aesthetic Uses of Water
Recreational uses of water as herewith discussed refers pri-
marily to water contact activities including swimming, wading, water
skiing, skin diving, boating, marinas, shoreline activities, and
aesthetic enjoyment, but not fishing. Of all beneficial uses of water,
perhaps the least progress has been made in recreational use, so far
as establishing rights and waber quality standards. Water quality
criteria for recreational uses have been limited and either very gen-
eral and qualitative in nature, or quantitative, based on arbitrary
assumptions. The plight of water recreation was summed up concisely
in a recent National Technical Advisory Committee Report (4) as
follows:
Recreation uses of water in the United States
have historically occupied an inferior position in
practice and law relative to other uses.
Where maintenance of recreation quality water
placed no significant burden on other water users,
recreation has customarily been considered an approp-
riate use. If other uses degraded quality below recrea-
tion quality, the recreation user has usually been
expected to seek alternative waters, a task constantly
rendered more difficult by rapidly expanding urbaniza-
tion, and industrialization.
In a number of western states, recreation does
not appear in the roster of ''beneficial usesff enumer-
ated by statute. The recognition of recreation as a
benefit and a purpose of water resource development
is a matter of recent history for such federal agencies
as the Corps of Engineers, the Bureau of Reclamation
and the Soil Conservation Service.
The reasons for these priorities in the uses of
water are found in the transition from an agrarian
to an industrial and urban society. Now the nation
faces a new order of social problems including, for
the first time in history, a serious concern for the
creative uses of the increasing amounts of leisure
available to our people. Today there is a growing
realization that recreation is a full partner in water
use; one that, with associate services, represents
a multi-million dollar industry with substantial
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115
prospects for future growth as well as an impor-
tant source of psychic and physical relaxation.
The NTAC Report (4) concluded that there was an urgent need
for systematic surveillance (traditional sanitary surveys broadened
to include aesthetic qualities) of waters and waste sources to make
effective use of criteria in practice. It also noted that the management
of water for aesthetic purposes must be planned and executed in the con-
text of land use, shoreline, and the water surface. Tables 34 and 35
reflect some recent thinking with respect to water quality criteria for
the protection of various uses of recreational waters.
Effects of potential pollutants in irrigation
return flows on recreational and aesthetic use
Due to a paucity of quantitative data on water quality criteria
for the protection of recreational ues of water, the following discussion
of the effects of potential pollutants in irrigation return flows is mainly
qualitative in nature. It should be acknowledged, however, that the set-
ting of limits on parameters describing minimum desirable water quality
for recreational uses is difficult because of variations in may of these
parameters, due soley to natural causes.
Potential Pollutants Adverse Effects
Total dissolved solids None
Hardness
Chloride
Sulfate
Sodium
Alkalinity
Nitrate Nutrients for the stimulation of
Phospate excessive aquatic plant growths
Tastes and odors and resulting tastes and odors.
Adversely affect practically all
recreational uses.
Turbidity Characteristic of many return
Color flows. Potentially serious ad-
verse effect on body contact
activities and aesthetic appeal.
-------
Table 34. Tentative guides for evaluating recreational waters (61).
Water-Contact
Boating and Aesthetic
Determination
Noticeable
Threshold
Coliforms, MPN/lOOml
Visible solids of sewage origin
ABS (detergent), mg/1
Suspended solids, mg/1
Flotable oil^and grease, mg/1
Emulsified oil and grease, mg/1
Turbidity, silica scale units
Color, std. cobalt scale units
Threshold odor number
Range of pH
Temperature, maximum C
Transparency, Secchi Disk, ft
10001
none
I1
201
O1
101
101
151
32 1
6. 5-9. 0
30
-
Limiting Noticeable
Threshold Threshold
2
none
2
100
5
20
50
100
256
6. 0-10.0
50
-
_
none
I1
201
0
201
201
151
321
6.5-9. 0
30
20
Limiting
Threshold
_
none
5
100
10
50
3
100
256
6. 0-10. 0
50
3
1 Value not to be exceeded in more than 20 percent of 20 consecutive samples, nor in any three
consecutive samples.
2No limiting concentration can be specified on basis of epidemiological evidence, provided no
fecal pollution is evident.
3No concentration likely to be found in surface waters would impede use.
Note: Noticeable threshold represents level at which people begin to notice and perhaps to complain.
Limiting threshold is level at which concentrations prohibit or seriously impair use of water
for recreation.
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117
Coliform organisms Assuming no unusual hazards,
a die-away pattern should exist
for any such organisms in the
irrigation water due to the un-
favorable conditions for their
existence. Apparently no gen-
eral evaluation can be made, but
conceivably a recreational health
hazard could be related to return
flows in certain situations.
Pesticides Suggested limits (4) for most
pesticides in municipal supplies
are very low. It appears im-
practical to impose the same
limits for recreational use be-
cause the water is not consumed
by man. There can be both a
direct and indirect adverse effect
on aquatic life, hence, the stan-
dards when established should give
primary consideration to toler-
ances of the aquatic life.
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Table 35. Summary of national technical advisory committee report on water quality criteria
for recreation and aesthetics (4).
00
Primary
Contact
Recreation
( wading
swimming
water skiing l
skin diving
Aesthetics
log mean of fecal coli-
forms less than ZOO
per 100 ml nor more
than 10 percent of
samples exceed 400
per 100 ml
pH range 6.5-8.3
(except from natural
causes)
Secchi disc visible at
minimum depth of
effect
(85°F)
Maximum water temp-
erature 30
(except by natural
causes)
log mean of fecal coli-
forms less than 1,000
per 100 ml and fecal
coliforms should not
exceed 2, 000 per 100
ml in more than 10
percent of samples
Average fecal coli-
forms less than 2, 000
per 100 ml
Maximum fecal coli-
forms 4, 000 per 100
ml
Freedom from:
All
Qualitative
Assessments
odor
color
turbidity
settleables
floatables
excessive aquatic plant nutrients
excessive, temperature
\
General
Recreation
Secondary
Contact
(boating \
marinas \
shoreline]
I activities I
Designated
Recreation
Secondary
Contact
| boating
] marinas
jshoreline
activities!
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119
MAXIMUM USE AND QUALITY
MANAGEMENT OF IRRIGATION WATER
Maximum Use of Water for Irrigation
Maximum use of available water results when the outflow is at
the highest possible salinity level without affecting crop production.
The return flow from an irrigated area usually is a combination of
drainage water from both tile and open drains, often mixed with waste
water from the canal system and runoff from irrigated fields, together
with the natural subsurface influents to the river system. So it is
difficult to place a specific value on the salinity level of the surface
outflow that might be tolerated. Effluent from drainage systems is
sometimes of a quality that cannot be used without dilution. Pillsbury
(21) reports that the average concentration of salts in tile effluent, in
a four-year study in California, was 5, 000 mg/1, (EC =7.4 mmhos/
cm at 25 C). Generally, after tile drainage systems are installed,
there is with time a gradual decrease in the salinity of the water due
to leaching of the salts stored in the soil before irrigation and drainage
began. Pillsbury found this reduction could be approximated by the
equation
-0 30
EC = 11. 74 y (Correlation coef. r = 0. 57)
where y was times in years after installation of the tile system. This
equation indicates that the average concentration for y = 1 year was
about 11.74, and after 10 years was 5.90 mmhos/cm.
These values might be compared with average values of the re-
turn flow from the Imperial Irrigation District (25) which averaged
4. 3 mmhos/cm in 1966. Improvements in the management of irriga-
tion systems to minimize operational wastes, and maximize applica-
tion efficiency of irrigation, will tend to increase the salinity of return
flows, but should have little effect on the resulting quality of the stream
flow. It would be of importance only in downstream areas where dilu-
tion and re-use are not possible.
In discussing water quality, Pillsbury and Blaney (9), consider
that water having a conductance of EC = 7. 5 mmhos/cm is "essentially
valueless for irrigation. " They point out, however, that under some
conditions water of higher salinity can be, and is being, used. An
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120
example was the former use of groundwater in the Wellton-Mohawk
area in Arizona, where Wilcox and Christiansen (unpublished) found
that the water from some of the wells being used for irrigation had a
salt content of more than 10, 000 rag/1. The use of such water was
possible because the groundwater level was far below the root zone,
the soils were highly permeable, a copious amount of water«-- possibly
in the range of two to four times the evapotranspiration -- was used for
each irrigation, and salt-tolerant crops were grown. Saturation extracts
from soil samples collected had lower salt concentrations than the irri-
gation water applied. This sample indicates that-under some condi-
tions fairly saline waters have value for irrigation, and where return
flows can be diluted to reasonable salinity levels, the resultant flow
is of value.
Bernstein (21) reasons that drainage water which passes through
the root zone under a system of maximum efficiency is of little or no
value even if diluted. He stated:
Drainage water, in the sense in which I shall use
the term, refers to the soil solution that has moved be-
low the root zone. Under conditions of maximum effi-
ciency of water use, the drainage water in passing
through the root zone will have had its salt content in-
creased by evapotranspiration to the maximum level
possible without unacceptable damage to the crop.
Such drainage water is spent and can contribute nothing
more to the water needs of crops of the same or lower
salt tolerance than the crop that it already nourished.
This is true even if the drainage water is diluted for re-
use with less saline water, for the concentration of salt
in the drainage water cannot be further increased with-
out damage to the crop. Therefore, if the water is
mixed and re-used, the. salt originally present in the
drainage water will reappear in the same volume of
drainage water that it was contained in after the first
passage through the root zone. Indeed, admixture of
such maximally used drainage waters with other irri-
gation water for re-use imposes burdens on the water
user, with no benefits. The user will have to apply
the extra volume of mixed drainage and fresh water
represented by the volume increment of re-used drain-
age water in the mixture in order to get the same
volume of usable water that he would have had if drain-
age water had not been mixed with the irrigation water.
And the drainage system will be burdened by the extra
volume of drainage water that it will have to carry.
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The situation changes, however, if the drain-
age water can be re-used on crops appreciably more
salt-tolerant than the initially irrigated crop(s).
Thus, if water with an electrical conductivity (EC)
of 1 mmho/cm has been maximally used for irriga-
tion of fruit crops whose tolerance is 4 mmhos/cm,
the water will have undergone a four-fold concentra-
tion as 75 percent of the water was evapotranspired.
(We neglect, at this time, salt precipitation and solu-
tion in the soil, and salt absorption by the crop. ) If
the drainage water from the fruit-crop area is avail-
able for irrigation of cotton, then 75 percent of the
drainage water can be used by the cotton crop as the
EC is increased further to the 16 mmhos/cm toler-
ance level of the cotton. Thus, for any succession of
crops, the fraction of maximally used drainage water
available for re-use is:
1 - EC /EC,
a b
•where EC values refer to allowable salinities for the
first crop, a, and the second crop, b. Maximum
allowable salinities that permit essentially full
yields (an estimated 90 percent, or more, of maxi-
mum obtainable yields) range from two to 18 mmhos.
This theoretical argument assumes that water of any quality can
be maximally used to obtain an effluent of such a concentration that it
has no further use for the same or less tolerant crops, and that the
leaching requirement formula (13), is valid for all water.
In practice, water of relatively low salinity cannot be used in
such a way that the effluent has the limiting value. Irrigation applica-
tion efficiency seldom exceeds 80 percent, and sometimes is less than
50 percent. This means that the quantity of effluent passing the root
zone under equilibrium conditions is generally from 20 to 50 percent
of the water applied; much more than required for a salt balance.
The electrical conductance (EC) of the effluent from a drainage sys-
tem, except during a period of reclamation of the soil after installa-
tion, will seldom exceed five time that of the irrigation water and is
often much lower. Thus, waters with an EC above 1 mmho/cm, should
have about the same practical value for irrigation as one with a conduc-
tance of 0. 1 mmho, assuming soil and drainage conditions are satis-
factory. Thus, it would be possible to increase the conductance of the
water in the main stream from very low values in the headwaters,
often less than 0. 1 mmho/cm, to a value of about 1 mmho, without
decreasing its value for irrigation of most crops.
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Further, many low salinity waters have fairly high percentages
of Ca and HCO,. When the Ca ions exceed the HCO ions, on an equiv-
alent basis, these waters are not objectionable, and upon use for irri-
gation, the salinity of the effluent does not increase in proportion to
the amount of evapotranspiration because of the precipitation of lime
in the soil. Thus, the formula for leaching requirement is not valid
for such waters. For example, Christiansen and Thome (9-discussion)
showed that upon concentrating the water of Logan River, Utah, 300
times, there was an increase in EC of the effluent from its initial value
of 0. 352 to a value of only 4. 12 mmhos/cm, or about 12 times. The
leaching requirement formula would imply an increase of 300 times.
Considering the solubility of the various salts in the water it was
predicted that a concentration of 300 times should have increased
the EC to 6. 6 mmhos, or an increase of 19 times the initial value.
That an appreciable amount of calcium salts present in the up-
stream water does not precipitate in the soil as the water is progres-
sively used and re-used downstream, is shown by the early salt
balance studies of Scofield on the Rio Grande, as reported by Branson
and Lunt (21). He showed that the increase in total salt concentration
between Del Norte, Colorado, and Fort Quitman, Texas, was 25-fold
(1.27 to 35.4 me/I),-while the increase in sodium was 57-fold (0.37 to
21. 3 me/I) and in chloride, 131 -fold (0. 16 to 21. 0 me /I). As previ-
ously mentioned, Table 4, for the Imperial Irrigation District, shows
that the ratio of increase in salinity from inflow to outflow was 1. 36
for HCO , 2. 17 for Ca, 3. 5 for total salts, 4. 32 for Na+K, and 5.91
for Cl. For some crops and conditions, the increase in the chloride
ion may be more limiting when considering re-use than the increase
in total salts.
Quality Management
Since irrigation return flow is an integral part of the hydrologic
system, it much be dealt with on this basis. In general, it cannot be
considered as a separate hydrologic unit, and therefore, methods to
control or manage the return flow must be consistent and compatible
with the hydraulic system containing the return flow. Salinity is the
major problem in irrigation return flow, and the two methods sug-
gested to control it (146) are "dilution (water supply increase) and
salt load decrease (desalinization). " Both control measures suggest
management factors which might be outside the hydraulic system.
While both control measures would be effective, management of the
salt load within the hydrologic system should be considered for the
required results.
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Natural dilution
Dilution of return flow occurs naturally in nearly all upstream
irrigated areas. Drainage waters, and other return flows, are
usually diluted in the main stream so that the resultant flow is of a
quality that can be used downstream for irrigation and other purposes.
For example, the water in the Colorado River at Parker Dam, which
contains all the return flow from the upper basin of the Colorado River,
is still of a quality that can be used for irrigation, domestic and
industrial purposes. This water enters the Metropolitan Aqueduct
which supplies a considerable portion of the needs of the southern
California area. Because of its hardness, however, some of it passes
through a water softening plant before entering the domestic distribu-
tion systems of L/os Angeles and other cities.
Limitations in the effectiveness of dilution. There are both
practical and theoretical limitations in the effectiveness of dilution as
a means of managing return flows. The practice is necessarily limited
to those places where downstream users can make beneficial use of
water if diluted to an acceptable salinity level. For example, the
highly saline drainage water from the Wellton-Mohawk Project (24)
could be used in Mexico when and if diluted to an acceptable salinity
level by Colorado River water.
In many upstream areas there is practically no choice; dilution
results naturally, and unless the resultant water is of a quality that
borders on the unacceptable, little or nothing can be done. In some
downstream areas there is no choice; there is no land or other poten-
tial use for the return flow, even if it could be physically diluted to
an acceptable salinity level. An example is in the Imperial Valley of
southern California. The return flow goes to the Salton Sea where the
water evaporates and the only use is for recreation. Another example
of using return flow, with or without dilution, is the use of water of
poor quality in the Grasslands area of San Joaquin Valley for irri-
gation of pastures and for wildlife. Large areas of waterflow marshes
are maintained in California, Utah, and other states, with water of
little value for irrigation.
Streamflow regulation for water quality control
Since the early 1900's streamflow regulation by the construction
of dams to impound flood flows for subsequent release for power gen-
eration and for low-flow augmentation as an aid to navigation has be-
come a well established practice on many rivers and streams through-
out the United States. Additionally, the provision of storage capacity
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for municipal, recreational, and irrigation use in such multi-purpose
reservoirs is now commonly included.
With respect to the impact of streamflow regulation on water
quality, it was not until sometime later that certain studies (157, 158)
illustrated the benefits to pollution abatement from augmentation of
low-water flows, although such benefits were incidental to other pri-
mary requirements for streamflow regulation.
General water quality considerations related to the
storage and release of waters from reservoirs
Impoundments may produce both beneficial and detrimental
effects on water quality(118, 159-176). Among the beneficial effects
are decreases in coliform bacteria, turbidity, suspended matter,
color, biochemical oxygen demand and the leveling out of variations
in chemical quality. The potential adverse effects on water quality
include a decrease in dissolved oxygen and an increase in carbon
dioxide, alkalinity, iron, manganese, and algae. Evaporation losses
result in an increased concentration of total dissolved solids. The
precipitation of calcium carbonate and silica will partly offset the
effect of increasing the salt concentration, and it also accounts for
the increase in the proportion of sodium salts. In some instances
the salt content of the water being stored is decreased. Bliss (176)
reported such a reduction for the Elephant Butte Reservoir. He
indicated that some of the apparent loss of salts could be accounted
for by the temporary bank storage during the filling period. Water
temperature may be increased or decreased, depending on the point
of release. This produces variable effects on water quality. Sub-
sequent uses and other factors should be considered.
Legal development of streamflow regulation
for water quality control
The concept of streamflow regulation as a specific measure for
water quality control emerged only after passage of the first Federal
Water Pollution Control Act of 1948. Amendments in 1961 first
authorized water quality control regulations as applied to streamflow
storage in federally constructed reservoirs. A comprehensive study
of low-flow augmentation, including legal aspects, state and national
policies, economic factors, technical considerations, and the overall
events leading up to its passage in the 196l act, is well documented
by Hull et al (178-183).
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Amendments concerning streamflow regulation, which now
appear in the act as section 3 (b), are set forth below:
In the survey or planning of any reservoir by
the Corps of Engineers, Bureau of Reclamation, or
other federal agency, consideration shall be given
to inclusion of storage for regulation of streamflow
for the purpose of water quality control, except that
any such storage and water releases shall not be pro-
vided as a substitute for adequate treatment or other
methods of controlling waste at the source.
The need for and the value of storage for this
purpose shall be determined by these agencies, with
the advice of the Secretary, and his views on these
matters shall be set forth in any report or presenta-
tion to the Congress proposing authorization or con-
struction of any reservoir including such storage.
The value of such storage shall be taken into
account in determining the economic value of the
entire project of •which it is a part, and costs shall
be allocated to the purpose of water quality control
in a manner which will insure that all project pur-
poses share equitably in the benefits of multiple-
purpose construction.
Costs of water quality control features incor-
porated in any federal reservoir or other impound-
ment under the provisions of this act shall be
determined and the beneficiaries identified and if
the benefits are widespread or national in scope,
the costs of such features shall be non-reimbursable.
Problems of interpretation of the 1961 legislation. Immediately
after the passage of the 19&1 amendments to the Federal Water Pol-
lution Control Act it became apparent that certain workings of the
legislation needed amplification, interpretation and quantification before
low-flow augmentation as a pollution control measure could be imple-
mented and administered properly. In recognition of the need for
better understanding of this newly authorized water quality management
tool, a symposium on streamflow regulation for quality control was
held in April of 1963, with subsequent publication of the proceedings
(184).
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Some pertinent comments reflecting the vagueness of the legisla-
tion were given by Smith (185):
The policy decisions posed can be divided into
three major categories, each of which involves a
number of associated economic and socio-political
questions. They are: a need to define adequate treat-
ment; a need to develop a basic engineering-economic
procedure for appraising the amount of storage required
and the value of the storage; and a need to define what
constitutes widespread or national benefits. The decision
made in each of these areas, regardless of the process
followed, represents a value judgment and hence influences
the cost-benefit ratio. The available options are many,
if not innumerable.
The lack of clear intent of the act was further illustrated by Towne
(186) who pointed out that:
When we try to compare the value of the benefits
from using a unit of storage for water quality control
with the value of using it to maintain a fishery, or for
water supply, or for flood control, or for any of the
other uses, we are in difficulty.
If we have to reduce or eliminate some uses be-
cause of limited storage capacity or limited runoff, how
can we compare the value of a unit of storage for quality
control with a unit of storage for some other purpose ?
Is flow regulation for water quality control to be placed
on a pedestal and considered worth the cost, regardless
of the value of competing uses ?
Another facet of the problem was recognized by Vanderhoof (170):
In some of the 17 western states, use of water for
quality control purposes is not recognized as a legitimate
use. If storage for regulation of streamflow for the
purpose of quality control is included in such a project,
it is not now apparent how such water can be reserved
for water quality control purposes when prior legitimate
water rights are not satisfied.
The regional nature of the conflict be.tween water rights and aug-
mentation of streamflow for water quality control was aptly described
by Stein (184):
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Increasing and often conflicting demands of
municipalities, industries, and agriculture for
water are making eastern water users acutely
aware of the lack of certainty of their water rights.
I would expect that in dealing with augmented
flows provided through flow regulation for water
quality control we will continue to have this uncer-
tainty in the East. I would also expect that with
its tradition an accommodation will be reached
in the East based on negotiation rather than on
legal action. In the 17 western states, however,
we are more likely to run into situations that will
involve legal actions. /It boils down to the fact
that there is more water in the East and therefore
more room for accommodations. In the West water
rights are essential to property rights and are
therefore a matter of life and death; every man is
fighting for every acre-foot of water he can get.
Present status of streamflow regulation
for quality control
The current status of storage and streamflow regulation for
water quality control can be best summarized perhaps by noting ex-
cerpts of remarks by Morgan (187) in June, 1968:
. . .the subject of "Reservoir Storage for
Flow Regulation for Water Quality Control" in
reservoir projects of federal agencies has been
a topic of extensive re-examination in recent
years. These efforts were intensified because of
recent criticisms by committees of the Congress
regarding inconsistencies of application of re-
imbursement control. Because these criticisms
were directed against Interior's Bureau of
Reclamation projects submitted to the Congress
for authorization, and because the responsibility
of administering Section 3 (b) of the Federal Water
Pollution Control Act had been transferred, in the
interim, to the Secretary of the Interior, the
Department undertook a searching re-examination
of past practices and of its own policy stance toward
proper application of the provisions of section 3 (b).
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As it now stands, no government-wide policy
on water quality control has as yet been formulated,
and to date no legislative changes have been recom-
mended to the Congress . . .
In the meantime, the Water Resources Council
is continuing and accelerating its efforts to formulate
a government-wide policy on the application of the
provisions of section 3(b) of the Federal Water Pol-
lution Control Act. It is not possible to predict what
that final policy will be.
Morgan noted that since 1961 two major water pollution control
laws have been enacted; the Water Quality Act of 1965 and the Clean
Water Restoration Act of 1966, in addition to Reorganization Plan No.
2 of 1966, which transferred the primary responsibility for administer-
ing the water pollution control act from the Department of Health, Edu-
cation, and Welfare to the Department of Interior. He concluded that
section 3(b) must be interpreted in the light of a new national policy:
In practice, this will mean a new baseline of
water quality, a new definition of what constitutes
"adequate treatment at the source" under the provi-
sions of section 3(b), and a new "pre-project" condi-
tion against which the additional benefits from quality
control storage in any federally-sponsored reservoir
must be measured and justified. To go below this base-
line of quality would mean that we had substituted
federally-financed "dilution" water for adequate treat-
ment at the source -- clearly contrary to the intent of
the law . . .
Noting that some states do not recognize water quality control by
low-flow augmentation as a legitimate beneficial use, Morgan opined:
We know this to be the case in a number of
states, and we are currently asking ourselves whether
or not it makes any sense at all to investigate possi-
bilities of storage for quality control where the legal
recognition of its status as a beneficial water use does
not exist.
On reflection, we believe it would still be neces-
sary to conduct whatever studies are needed so as to
reveal the total effects of the project on all water uses
and their quality components. On the other hand, of
course, a state with such legal barriers may indicate
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that it wishes to learn what opportunities it thus
foregoes -- with a view toward making such legis-
lative and institutional changes as may be needed
to avail itself of this added tool of water quality
management. A pre-project planning consultation
could establish this.
Evaluation of the feasibility of streamflow regulation
for water quality control of irrigation return flow
Original consideration and evaluation of the use of streamflow
regulation and low-flow augmentation for water quality control was
identified with problems of the eastern United States and viewed with-
in the framework of the riparian water rights doctrine. The consider-
ation centered mainly on the release of dilution water for maintaining
adequate dissolved oxygen levels in rivers and streams where residual
organic loadings were great enough to depress the dissolved oxygen
levels below an acceptable minimum or where projections into the
future predicted this type of problem would exist.
When later viewed within the framework of the western appropri-
ation water rights doctrine and for use on similar water quality control
problems, as well as irrigation return flow (e. g. salinity control), the
appearance of basic conflicts with state legislation and difficulty of
interpretation of the "substitution for adequate treatment" clause pre-
cluded any effective use of the law as originally worded. An exception
to such a generalization is the release of stored water on the Colorado
River to dilute the flow below the Wellton-Mohawk project in order to
keep below 1, 500 mg/1 the concentration in the water going to Mexico.
In general, low-flow augmentation or streamflow regulation for
water quality control in the West would result in a reduction in the
amount of water available for irrigation, municipal, industrial, and
other upstream uses. Since in many cases established rights to the
use of water far exceed the supply, such uses for quality control would
also be in conflict with the established water rights. Establishing
priority rights for quality control under the existing doctrine of
appropriation would be complex.
It appears that a revision of the original 1961 legislation is in the
offing. Hopefully this will be more definitive and reflect .the changes
that have since emerged in national policy toward water quality and
pollution control. Until that time streamflow regulation for water
quality control of irrigation return flows cannot be relied upon as a
useful or important management technique.
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Return Flow Control
Return flow control is important primarily in regard to its
effect on the quality and pollution vectors of the receiving water. The
diversion of water and its subsequent return to the stream without pol-
lution or changes in quality are problems only insofar as they change
the ecology of the undiverted water or dry stream bed. On the other
hand, methods of control should be sought to prevent undesirable
changes in the quality and pollution status of the receiving water. In
some hydrologic systems, reduction of the return flow by controlling
seepage from canals may be highly important in controlling salinity.
However, in some cases and for extreme conditions, it may be neces-
sary to capture, control, and dispose of, or desalinate, the return
flow. It is recognized that little can be done in this regard except
in the lower areas of the system where it is sometimes possible to
bypass, evaporate, desalinate, or otherwise control the return flow.
Canal lining to prevent seepage
Many unlined irrigation canals traverse long distances between
the diversion point and the farm land. Seepage losses may be consider-
able, with resulting low delivery efficiencies. Canal lining has tradi-
tionally been employed to prevent seepage and save water, and the
economics of lining have been justified primarily on the basis of the
value of the water saved. The possibility that water seeping from
canals may greatly increase the total contribution of dissolved solids
in the receiving waters has only recently been given serious attention.
Canal losses (.mostly seepage) may be measured using the inflow-
outflow method or the ponding method, or they may be estimated from
the following formula (188):
s = o. zcVoTv"
where
S = loss in cfs per mile of canal
Q = discharge of canal in cfs
V = mean velocity of flow in fps
C = cubic feet of water lost in 24 hours through
each square foot of the canal prism.
Houk (1) reports that the average seasonal' canal losses varied
from 13 percent of the diversions on the Uncompahgre Project, Colo-
rado, to 48 percent of the diversions on the Carlsbad Project, New
Mexico.
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If these losses occur mainly on the long diversion lines between
the diversion dam and the project and if the soils along the canal align-
ment are high in residual salts, the salt contribution from this source
could easily exceed that leached from the irrigated land to maintain a
salt balance. Whether or not the soils along the canal right-of-way are
high in residual salts, the salt from this source could be largely elim-
inated by canal lining. The value of improved water quality is another
benefit to be claimed in the economic justification of canal lining.
Bypassing downstream diversions
For areas in the lower part of the basin, bypassing the effluent
from drainage systems around downstream diversions and disposing
of it directly into the ocean, or back into the stream channel where it
will not be objectionable, is probably the most practical procedure.
After careful investigation, bypassing proved to be the least expensive
and the most practical solution of the San Joaquin Valley drainage prob-
lem (21, 124, 189-192).
San Luis or San Joaquin master drain. Several alternatives were
considered for removal of the drainage effluent from the San Joaquin
Valley. The most promising were bypassing the downstream diversion
and discharging the effluent directly into the Suisun Bay, transporting
the effluent directly westward to the Pacific Ocean by pipelines and
pumping, evaporation of the effluent and storage of the precipitated
salts, and desalting and evaporation of the concentrated brine. Investi-
gation revealed that the alternative methods would cost from 1. 5 to 8. 2
times as much as constructing a 280-mile master drain.
Wellton-Mohawk drainage solution. Another example of bypass-
ing downstream diversions is the solution of the problem in the Well-
ton-Mohawk district in southern Arizona (24). Irrigation of land along
the lower Gila River dates back to 1891 when a headgate structure and
a canal 10 miles long were constructed by pioneers. Shortly afterward,
a disastrous flood wiped out the canal system and a temporary weir
across the river. In 1908 a new river heading was constructed to
irrigate 1,200 acres south of the river. By this time, upstream devel-
opments made the water supply even less dependable. Farming stopped
until 1920 when development of groundwater began. The irrigated area
expanded rapidly to a peak of about 11, 000 acres during the early 1930's.
Then wells began to fail, and groundwater quality deteriorated rapidly
due to evapotranspiration and recirculation.
Construction of the Wellton-Mohawk project was authorized in
1947. This project provided for the irrigation of 75, 000 acres, includ-
ing 15, 000 acres on a mesa south of the valley. When the irrigation
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system was planned it was anticipated that drainage facilities would
be required, but because the groundwater level was then at a consider-
able depth it was decided to defer construction of a drainage system
until needed. A network of observation wells was installed to observe
the rise of the water table. The rate of rise of the groundwater was
much faster than had been anticipated. By 1958, the drainage prob-
lem had become serious, and investigations were started to determine
the most economical solution. The solution adopted was to construct
a concrete lined drainage channel through the district, 73 miles long,
and to control the water table by pumping from wells. This channel
was completed in July, 1961, by which time 62 drainage wells were
completed and were being pumped. An additional five wells were soon
added, for a total of 67 wells. In 1962, 26, 000 acres in the lower part
of the area had a water table less than eight feet from, the surface. By
1964, this area had been reduced to 7, 250 acres.
The salinity of the groundwater was very high. In the beginning,
the average salinity of the pumped water was 6, 500 mg/1, and it reached
a high of 17, 000 mg/1. The discharge of this highly saline water back
into the Gila River, above its confluence with the Colorado River and
Mexican diversions, caused an immediate salinity problem for Mexico.
A solution to this problem was worked out with Mexico in 1965, and
after a "crash program" of construction, a bypass channel was com-
pleted in November, 1965. This solution makes it possible to divert
the water to the Colorado River, or bypass it around Morelos Dam, at
Mexico's request. On this project, it is difficult to assess what costs
should be attributed to the pollution control phases, inasmuch as more
than 12 construction projects were involved and the overall project was
built in stages.
Evaporation
Evaporation is a natural way to dispose of unwanted waters, but
for many locations the area required to evaporate the quantities of
return flow involved would make the method impractical. For the San
Joaquin Valley problem(26), for instance:
Nearly 70, 000 acres would be required for total
evaporation of the waste waters from the Tulare Lake
Basin. Though selected sites contain some of the most
impermeable soils in the valley, it is technically pos-
sible to reclaim them for agricultural purposes. . .
The infiltration studies revealed rates of down-
ward water movement from a low of 0. 0001 to a high
of 0. 01 foot per day in the selected areas. Based on
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these results, infiltration rates over large areas
of the proposed sites were estimated to be from
0. 001 to 0. 002 foot per day.
Considering that evaporation rates during the summer months
might be in the range of 0. 02 to 0. 04 feet per day, it is clearly evident
that when the water becomes concentrated about 20-fold by evaporation,
an equilibrium would be reached and as much salt would then be pass-
ing downward into the groundwater basin as would be coming into the
evaporating area. To reduce this seepage of concentrated brine, it
was proposed that:
The evaporation system would consist of a series
of pon.ds, located at strategic places, such that the
progressively concentrated waters would be gradually
moved toward the safest areas for final evaporation.
Some of the ponds containing the most concentrated
brines might require lining.
Preventing seepage of the concentrated brines from returning to
the stream channel or to the underground water body would generally
be a major problem. Also, in many instances much of the return flow
from irrigated areas reaches the stream channels by natural means,
and not through man-made drainage channels. Except where salts in
the return flow were concentrated to approximately the upper permis-
sible limits by careful soil water management, the loss of all the return
flow by evaporation would be objectionable. Where dilution to safe
limits is possible, return flow has value to downstream users.
The area required for evaporation could be estimated by assum-
ing that annual rates from the large areas involved would be in the
range of 0. 6 to 0. 8 times the annual evaporation from class "A" pans.
Where pan evaporation data are lacking, estimates could be made using
reliable formulas. The depth evaporated would probably be in the range
of 40 to 100 inches per year.
Mineralized springs
Although evaporation of return flow might be impractical in most
cases, it could be useful where water from highly mineralized natural
springs that normally flow into streams are diverted for irrigation or
other purposes. For example, Milligan, et al (193) found that the
LaVerkin Springs in southern Utah produced about 100, 000 tons of salt
per year in a flow of about 12 cubic feet per second. The Bureau of
Reclamation studied the effect of this salt addition on the resultant
quality of the water and found that, after the development of the Dixie
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Project in southern Utah, the effect of removing the flow and salt of
LaVerkin Springs would be to reduce the weighted mean annual salt
content of the Virgin River at Littlefield, Arizona, from an estimated
2, 370 mg/1 to 1, 790 mg/1, or about 600 mg/1. During June and July,
the reduction would range from 800 to 1, 000 mg/1.
The physical accomplishment of the collection
and removal of LaVerkin Springs water would not be
simple. The springs emerge in a narrow steep
canyon Any removal scheme would likely involve
pumping the mineral water out of the river channel dur-
ing low flow periods. It might be possible to convey the
water to the Bench Lake area and there provide evapora-
tion opportunity (193).
Another example in Utah (193) would be the possibility of divert-
ing the highly mineralized water from Crystal Springs, which enters
Bear River above the Federal Migratory Game Bird Refuge at the
northeast end of Great Salt Lake. The flow of about 3. 5 cf/s with more
than 400 tons of salt per day, could either be evaporated, conveyed in
a separate channel to the Great Salt Lake, or temporarily stored during
the low flow periods and discharged back into the river during high flow
periods. The storage requirements for this third alternative would be
about 5, 000 acre feet. No estimates have been made of the cost or bene-
fits of these alternatives. However, if it is possible to control or elim-
inate natural mineral springs as a source of salt, the water in the sys-
tem would certainly be improved for irrigation and other uses.
Control of leaching
Another approach is to control the application of water to land
in order to minimize salt pickup in geologic formations. The most
drastic action is to eliminate irrigation in areas of high salinity such
as those where the soils are formed from salty shales. Preventing or
reducing the amount of water penetrating to deeper soil stratas high in
salt would also effectively reduce the salt load in the return flow. The
use of artificial or natural barriers below the root zone, coupled with
drainage systems to interupt water applied by irrigation before it
reaches the deeper stratas, would be effective. Regulating the amount
of water applied to the land and thereby regulating the amount of drain-
age water represents a combination of controlled leaching and dilution
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135
Desalinization and Contaminant Removal
The three major categories of contaminants relevant to irrigation
return flow quality are minerals, nutrients, and some pesticides (123).
While removal of these three contaminant categories is technically
feasible (194), the technologies are young and only recently have ad-
vanced beyond the pilot plant stage for some processes and are still
in the research and development stages for others. The two major
classifications of technology relevant to the above contaminant cate-
gories are desalting and advanced waste treatment. The desalting
technologies are oriented toward removal of "minerals," though desalt-
ing processes will remove most contaminants. The advanced waste
treatment technologies are oriented largely toward removal of nutrients
and other contaminants common to municipal and industrial waste
effluents. There has been but limited formal inquiry into the subject
of treatment of irrigation return flows. The results of two case studies
are presented to provide some insight into the cost of applying advanced
waste treatment and desalting technologies to irrigation return flows.
Treatment for pollution control in San Joaquin Valley
In the San Joaquin Master Drain study, pollution abatement was
the motivation for considering drainage water treatment.
Howe(195) has pointed out that desalting technology could well be
applied to irrigation return flows, with electrodialysis probably the
most suitable process. Applying this technology to the San Joaquin
Valley drainage problem, desalted drainage water could probably be
produced at about $117 per acre-foot. This plan was amplified by
Baker (196). The 195, 000-acre-foot per year of salvaged water would
have value for municipal and industrial use, leaving only 33, 000-acre-
foot per year of brine to be disposed of by transport to the sea. The
California Department of Water Resources concluded that treatment of
San Joaquin Valley agricultural waste water for consumptive re-use
was not economically sound (123, 124). Although this plan was not
economically feasible it was one of the first formal investigations for
desalting irrigation return flows.
This same study stimulated further formal investigation of treat-
ment of irrigation water. An alternative plan was to transport this
water to the San Francisco Bay delta, but it was found that this would
result in unacceptable nitrate levels in the receiving water. The con-
centrations of salts, phosphates, and pesticides were felt to be insig-
nificant problems to this receiving water (197). This led to the recom-
mendation that studies be pursued to establish the economic feasibility
of nitrogen removal of the San Joaquin Valley drainage water. Such a
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136
pilot plant study site has since been established at the Interagency
Agricultural Waste Water Treatment Center near Firebaugh.
Studies are being conducted to find the best method for removal
of nitrate from the waste water before it is discharged into San
Francisco Bay. Methods being considered include denitrification
(reduction of nitrate), "algae stripping" (the growing and harvesting
of algae), and the removal of nitrate by selective exchange resins
(123). Cost estimates indicate it would be cheaper to remove the
nitrate from the water and discharge the water into the bay than it
would be to leave it untreated and transport waste water into the ocean.
Treatment for water supply
Irrigation water supply augmentation was the primary motivation
of Maletic, Sachs, and Krous (198) in their study to evaluate the eco-
nomic feasibility of desalting drainage water, using a 10, 000-acre area
near Yuma, Arizona, as a case study. Benefit/cost ratios, using de-
salted drainage water as a supply for irrigation, ranged from 0. 86 to
1. 62. The most favorable B/C ratio resulted from utilizing the multi-
stage flash process and nuclear energy. Cost of energy was set at
3. 13 mills/kw hr. The calculation was based upon a feed water salt
concentration of 5, 330 mg/1, and a 50 mgd nuclear dual purpose plant.
Cost of this water was calculated at $109/acre-ft (34^/1, 000 gal)
using a cost formula developed by the Oakridge National Laboratory.
Benefits were fewer than costs for all salinity levels of product water
when the energy cost was 6. 0 mills/kw hr.
A further study (199) considers irrigated areas in Arizona and
California to examine benefits and costs associated with using desalted
water for irrigation. Value of desalted water for irrigation has been
considered also by Vilentchuk (200) and by Hammond (201).
It should be emphasized that desalting merely divides the stream
into two streams, a large one of desalted water, and a smaller one of
brine. This brine must then be disposed of by transportation to the
sea or other point of disposal, or it must be evaporated. For some
locations, the cost of either method would be prohibitively high (123).
Pesticide removal
There appears to be no concerted effort directed at developing a
technology aimed specifically at pesticide removal. Pesticides are
felt to be no problem for the San Joaquin Master Drain case (197).
Activated carbon columns have been used to concentrate pesticides,
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137
however, and could provide the basis for treatment, should pesticides
become a problem.
Nutrient removal technology
"Advanced waste treatment" is the term used by a research pro-
gram of that name (194) currently housed in the Federal Water Pollu-
tion Control Administration, to study treatment methods for removal
of water contaminants not normally removed sufficiently by the usual
water or waste treatment processes. The program had its beginning
in I960. As applied to waste water, these advanced waste treatment
methods often are called collectively "tertiary treatment." Pollution
control or water supply augmentation through re-use are the primary
incentives for application of advanced waste treatment methods. The
particular method chosen depends upon the constituent(s) which require
removal, as some of the methods are specific to particular water con-
stituents.
The water contaminants for which removal processes have been
and are being investigated include turbidity, hardness, phosphates,
nitrates, ammonia, and minerals (194). Among the processes investi-
gated (202) are micros.training (turbidity), diotomaceons earth,
(turbidity), granular activated carbon, powdered activated carbon
(soluble organics), chemical clarification (turbidity, phosphates,
hardness), biological nitrification-denitrification (nitrates), air strip-
ping (ammonia), and desalting (minerals). Costs of treatment range
from 1. 5£/l, 000 gal for micro straining to 15^/1, 000 gal for chemical
precipitation -- based upon projections from pilot plant operation for
plants of the 10 mgd size; the desalting cost projections include 16£/
1, 000 gal exclusive of pre-treatment and brine disposal for electrodi-
alysis, and 48£/l, 000 gal for freezing. More detailed cost figures and
the assumptions used are given by Smith (203). Research on these
various processes is continuing, while pilot plant experience is being
gained at such centers as Lebanon, Ohio and Pomona, California and
other locations operating single pilot plants.
A further listing of removal processes for nitrogen and phos-
phorus is given in Table 36 by Eliassen and Tchobanoglous (204), with
their cost figures.
The cost data in Table 36 give an order of magnitude estimates,
since full scale operating plants do not exist for several of the proc-
esses listed. In addition, costs are dependent upon physical and eco-
nomic circumstances unique to a particular site. It is clear also from
the data that many of the processes listed are not specific to either
nitrogen or phosphorus removal (for example, electrodialysis is an
expensive method of removing nitrates, if nitrate is the sole concern. )
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138
Table 36. Processes used for the removal of nitrogen and
phosphorus (Z04).
Substance
removed
Nitrogen
Removal process
Anaerobic denitrification
Algae harvesting
Ammonia stripping
Cost
£/l, 000 gal
2. 5- 3
2-3.5
.9-2.5
Phosphorus
Ion exchange
Electrochemical treatment
Electrodialysis
Reverse osmosis
Distillation
Land application
Chemical precipitation
Sorption (activated alumina)
Ion exchange
Electrochemical
Electrodialysis
Reverse osmosis
treatment
17- 30
.4- .8 (energy only)
10- 25
6. 5-9. 3
40-100
1-
4-
17-
7
7
30
.4- .8
10- 25
25- 40
Distillation
Land application
40-100
7.5- 15
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139
One well known plant (which began operation in 1965) having data
available for the chemical precipitation process and the activated car-
bon sorption process is located at South Lake Tahoe. Of interest here
is the phosphate content, which is reduced from Z5-30 mg/1 to 0.1-
1. 0 mg/1 in the chemical precipitation process; the carbon column
reduces total organic carbon from 30-60 mg/1 (205). Total costs (fixed
costs and operating costs) are estimated at 14£/1, 000 gal for phos-
phate removals by chemical precipitation and the final polishing for
other residuals with activated carbon, for this 2. 5 mgd plant. In
another study on this plant, Gulp and Slechta (206) found that carbon
treatment costs 6. 5£/l, 000 gal which includes both fixed and operating
costs; the latter includes carbon regeneration.
Phosphate removal processes and costs are summarized in more
detail in a feature article in Environmental Science and Technology
(207), which also summarizes data from eight pilot or newly operational
full scale plants employing a phosphate removal process. Costs re-
ported range from one to 10^/1, 000 gal with removal efficiencies mostly
90 to 95 percent. Probably most of the feasible processes for removal
of nitrates and phosphates have been explored, and the most promising
processes have been developed further on a pilot plant scale. The
major advances in technology will probably come from improving de-
sign and operating characteristics of these pilot and full scale plants
and in lowering costs of recycling chemicals. With a strong emphasis
on reducing nutrient levels in receiving waters, nitrate and phosphate
removal will surely be practiced on a much broader scale. Costs of
nitrate and phosphate removal presumably will be reduced because of
this increased practice; however, the amount of reduction and the lower
limits of costs are not implicit in the literature.
The advanced waste treatment technology gained through appli-
cation to municipal and industrial treatment can provide a basis for
projecting feasibility and cost for treating irrigation return flows.
The Firebaugh study is of great value in delineating the technology and
economics specific to irrigation return flows. The diffuse nature of
irrigation return flow is an aspect of the problem that is relevant to
treatment feasibility. Thus the extent to which return flows, for any
given irrigated area, are amenable to collection, and the cost of such
collection, should be evaluated prior to entertaining the concept of
treatment on a broad scale.
Removal of minerals
In Table 37 most of the basic desalting processes and the installed
capacity, through 1967, are indicated by type of plant. Technology is
probably most advanced for the multistage flash process (MSF). The
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140
Table 37. Distribution of desalting plants by type of process (213).
Number of Plant Capacity Percent
Plants MGD Total
Total all processes
Distillation
Multistage flash (MSF-D)
Submerged tube (ST-D)
Long tube vertical (VTE-D)
Flash (F-D)
Vapor compression (VC-D)
Membrane
Electrodialysis (E-M)
Reverse osmosis (R-M)
Crystallization
Secondary refrigerant
(SRF-A)
Vacuum freezing
Vapor compression (FV-A)
627
585
137
293
92
46
17
38
36
2
4
1
3
222. 3
216. 6
153. 3
37.5. .
16.6
7. 1
2. 1
5. 1
5. 0
0. 1
0. 6
0.2
0.4
100. 0
97.4
2. 3
0.3
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141
reverse osmosis process is classed as a irbreakthrough" in technology,
with the development of high flux membranes in I960 (208) and has
generated considerable enthusiasm because of its low energy require-
ment. A major technical problem involves membrane support to with-
stand the high pressures against the membrane; the solution must be
sufficiently economical that high capital costs do not nullify the low
energy requirements. The various processes listed in Table 37 are
described well In the booklet, A-B-Seas of Desalting (209).
Energy requirements. The reversible work required to remove
pure water from sea water is 2. 8 kw hr/kgal at 25°C. The degree to
which the particular equipment or process follows a reversible path
is a measure of its ''effectiveness of energy utilization." As a rule,
achieving higher thermodynamic efficiencies requires more capital
and maintenance expenditures, so there exists a practical limit as to
how far the ideal can be pursued.
Figure 7 Illustrates the comparative energy requirements for
the various major processes. It is immediately apparent why reverse
osmosis is so attractive, with an energy requirement of only 26 kw/
hr/kgal, as compared with about 290 kw hr/kgal for multistage flash
distillation (210). It is also apparent that an operating plant's energy
requirements far exceed the theoretical limit of 2. 8 kw hr/kgal. The
practical minimum is about four times the theoretical minimum, accord-
ing to Murphy (211).
Sources of energy. The source of energy bears on the problem
only as related to cost. Depending upon the situation, any one of
several fuels may be the most economical. Nuclear energy is easily
available to any remote location, while the economy of coal, oil, or
gas depends more on the degree of logistic support. The cost of
nuclear power is decreasing as technology advances; also cost of
energy declines as the plant scale increases. Plants in design of 500
to 1, 000 MW size have projected costs of 3. 5 to 5 mills/kwh, compared
to plants in operation in 1965 producing power at 5 to 10 mills/kwh
(212).
Dual plants. The dual purpose plant, which will produce both
electricity and desalted water, is strongly advocated (210). The water
production for such a plant bears only the incremental costs. Figure 7
shows that the energy utilized decreases from 290 kwh/kgal for a
water-only distillation plant to 170 kwh/kgal for a dual plant. It is
further suggested by Reichle that the established electric utility
companies can produce electricity and steam at the lowest cost. An
additional advantage exists in that off-peak energy production could be
utilized for desalting. No dual purpose plant has yet been built, but
projections (214) indicate that by 1975 to 1978 the nuclear and water
-------
4-
ro
FOSSIL FUEL ENERGY NEEDED
TO PRODUCE STEAM
NUCLEAR FUEL ENERGY NEEDED
TO PRODUCE STEAM
FOSSIL FUEL ENERGY NEEDED TO PRODUCE
ELECTRICITY OR MECHANICAL ENERGY
NUCLEAR FUEL ENERGY NEEDED TO PRODUCE
ELECTRICITY OR MECHINICAL ENERGY
WATER
ONLY
290
DUAL WATER ONLY
PURPOSE (IF STEAM
(NET FUEL IS GENE-
FOR WATER RATED
PPODUCTION) ELECTRI-
CALLY)
BRACKISH
WATER
SEA
WATER
750 775
255
170 152
450
to
530
to
440E#
to
203
«*»
141
r
MULTISTAGE FLASH EVAPORATOR
ELECTRODIALYSIS
VAPOR COM- FREEZING REVERSE
PRESSION OSMOSIS
DISTILLATION
Figure 7. Typical fuel energy required by various desalting processes to produce
1,000 gallons of fresh water (in kilowatt-hours)(2IO).
-------
143
technologies will be sufficiently advanced to permit such combina-
tions of the dual purpose plant.
Cost of desalted water
Cost of desalted water is related directly to the gross considera-
tions of process technology and scale of operation; other more detailed
operational considerations such as load factor, access to fuel and brine
disposal, also bear on the problem. For example, the cost reduction
from $4/kgal to $l/kgal from 1955 to 1965 was effected through im-
provement in process technology. The cost effect of scale and advance-
ments in technology can be seen in Figure 8, which is based upon
projections by the Office of Saline Water (215). It should be emphasized
that the cost projections of Figure 8 are indicative of a probable trend and
and that the cost figures probably are in the proper order of magnitude.
Additional insight into costs can be seen in Figure 9.
It should be noted also that most of the optimism for this low
cost water is based upon development of dual energy-desalting tech-
nology. Plans are being revived for the 100 mgd Bolsa Island dual
purpose plant of the Metropolitan Water District of Southern California.
Cost of water from this plant was anticipated originally at 25£/l, 000
gal; currently costs are anticipated at 32-35^/1, 000 gal.
There is considerable optimism for the reverse osmosis process,
because of its low energy requirement. The energy cost for reverse
osmosis, using say 30 kwh/kgal energy and 0. 5%/kwh energy cost, would
be 15^/kgal. Using the minimum energy projected for an electrodi-
alysis plant of 32 kwh/kgal, seen in Figure 7, gives about the same
value, 15^/kgal. Amortized capital costs and operation and mainten-
ance costs are not included in this rough calculation. The cost of
15^/1, 000 gal for energy gives some idea of the rock bottom price of
desalted water by reverse osmosis or electrodialysis.
In developing cost estimates for specific proposed MSF desalting
plants, the computer cost models developed by the Oak Ridge National
Laboratory (ORNL) should be mentioned. The ORNL program considers
many detailed factors, including feed water temperature, cost of
materials, load, size, cost of energy and interest rate. The program
optimizes plant design and gives fixed and operating costs. The pro-
gram was used by Maletic, Sachs, and Krous (198) in their feasibility
study for desalting irrigation return flows for recycle back into the
irrigation system. Desalting for irrigation does not appear to be an
economic solution, except under some unusual circumstances where
it may be combined with power production, dilution, and treatment of
water for domestic or industrial use.
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144
200
I
~J
-4
§
K
CO
'O
O
Q;
S
i
too
50
\0
5
1965
1970
1975
1980
1985
1990
Based on: |. Distillation technology
2. 6% fixed charge rate
3. U. S. construction and operation
4. Dual purpose plants
5. Most probable energy costs
Figure 8. Projection of sea water desalting costs for a range
of plant sizes (215).
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145
1.75
1.50
S
o
o
o
o
o
o:
UJ
o
o
tr
a.
1.25
1.00
.75
.50
.25
.00
X
MSF.
ED.
RO.
7% FIXED CHARGES, 7MILLPOWER
30c/m Btu FUEL.
1800 PPM FEED, 0.8$ KWH POWER,
7% FIXED CHARGE RATE, I MGD.
I MGD, 5.000 PPM FEED, 0.7$/
KWH POWER, 7% FIXED CHARGE RATE.
KEY WEST
(NORMALIZED)
VIRGIN ISLANDS
X
JIDDA
KEY WEST
• •^/'(REPORTED)
S
ROSAJirro
X
— I
SINGLE PURPOSE.
DUAL PURPOSE.
I I
I
I
I
I
1963
1964 1965 1966 1967 1968 1969
Figure 9. DESALTING PRODUCT WATER COST VS YEAR.
AFTER: OFFICE OF SALINE WATER, " SALINE WATER FIVE
YEAR PROGRESS REPORT JANUARY 1963 THROUGH
MARCH 1968" APRIL 1968.
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146
Conventional water. Cost of conventional water is relevant to the
irrigation return flow problem because of its potential value as a water
supply. As costs of incremental development of conventional supplies
exceed the costs of desalting, the water supply motivation will assume
increasing importance in alleviating the pollution problems of irrigation
return flows. This implies that a "systems" approach is warranted in
decisions concerning abatement of irrigation return flow problems.
Thus, damages due to pollution and benefits from water supply augmen-
tation should be weighed against the alternative cost of transporting
drainage water to the sea. Some insight into costs of conventional
water supplies is relevant,therefore to the problem of irrigation return
flow.
Figure 10 provides an order of magnitude cost estimate of con-
ventional water as affected by transportation, distance, and supply
needed. Figure 11 is an envelope curve assessing costs of conventional
supplies. An order of magnitude assessment of nominal costs of water
for various purposes is seen in Table 38.
Another insight concerning cost of conventional water supplies is
reported by Koenig (216), who analyzes costs of storage for more than
1,000 U. S. reservoirs. He converts the cost per acre feet for various
sizes of reservoirs to an annual basis, Table 39. Koenig further analyzes
conveyance costs, summarized in Table 40.
Koenig illustrates the types of final costs arrived at by his pro-
cedures for a hypothetical new conventional supply for Pierre, South
Dakota. Figure 12, taken from his work, shows the relationship between
water cost, production level, and conveyance distance. The zero convey-
ance costs consist largely of treatment for both the surface and ground-
water cases (softening for both and softening only for the latter), and
about 20 percent of the cost for impoundment. Conveyance costs are
seen to add the difference between the zero conveyance curves and the
100-mile and 500-mile curves.
-------
Population Receiving Water Supply
100
LTV - long tube vertical distillation process
MFD - multiflash distillation process
ED - electrodialysis process
I I
I
10
10'
10 10
Capacity-GPD
10
Figure 10. Cost of conventional water ve. water from deealinization
plants (212).
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148
$/1000 Gallons
5. 00
4.00
3.00
2. 00
1. 00
1952
Figure 11. Cost of fresh water--conventional and converted
(217).
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149
Table 38. Typical rates for water in western United States (from
report by Los Angeles Chamber of Commerce)(218).
Approx
Irrigated agriculture
Bureau of Reclamation,
charges (.
Independent districts,
charges (.
Individual wells,
costs (.
Municipalities
Cost of water to the city (.
Owens Aqueduct (L. A. )
Pasadena, MWD water
(1956)
Retail charge to con-
sumers (.
Industries, charges, or
costs (.
. Water Rates
Low
$1-2
003-.006) (
$2-5
006-.013) (
$2
006)
$2
006)
-
$5-10
015-. 03)
$2
006)
per acre
Average
$2-6
.006-. 02)
$5-10
.015-. 03)
$10
(.03)
$30
(.09)
$19
$44
(.13)
$50-100
(. 15-. 30)
$50-100
(. 15-. 30)
-ft/($/kgal)
High
$27
(.08)
$40
(.12)
$20
(.06)
$100
(.30)
-
$200
(.60)
$1000
(3. 00)
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150
Table 39. Illustrative annual costs of impoundment (216).
Capacity
(acre ft)
1, 000
10, 000
100, 000
1, 000, 000
10, 000, 000
Unit costs
(capital recovery and
($/yr/acre ft)
28.5
8.9
3. 1
1.3
0. 75
DM)
Table 40. Costs of water conveyance by pipeline (216).
Conveyance cost, Average Conveyance Rate
$/kgal/mile MOD
0. 032
0. 0083
0. 0031
0. 0012
0. 0005
0.
1
10
100
1000
1
-------
151
10
CO
rt
bO
CO
O
U
0. 1
0.01
sw
0.01 0.1 1 10 100 1000
Average production, Q, rngd
Figure 12. Exemplary costs of conventional supply at Pierre,
South Dakota (216).
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153
ECONOMIC ASPECTS
Economic Considerations
Practically no research has been done on economics of the prob-
lem of water quality and irrigation return flows. However, a great
deal of empirical and conceptual work has been accomplished which is
basic and of value in extension of research to more specific analyses
of the problem. Economic aspects of pollutional problems of irrigation
return flows include the economic impact of lowered water quality, and
economic feasibility of control measures and other adjustments.
The unique and extremely difficult economic problems related to
Irrigation return flows involve external economies and diseconomies.
These problems occur both with water quality and quantity considera-
tions. Both farm and non-farm business enterprises must be con-
cerned, for they are interdependent in the physical use of resources,
yet they make decisions independently. These problems frequently are
referred to In terms of Incidence of costs and incomes.
In irrigation return flows, a portion of the original water supply
Is re-used for Irrigation one or more times, and re-used water Is
usually of poorer quality than the original supply. The re-use of water
has important implications In the total supply and efficiency of use. A
given storage supply development may total more water for irrigation
than Is suggested by the reservoir capacity and project size. This re-
use has significant effect on the financial feasibility of the project.
This apparently has not been completely recognized in project formula-
tion.
Associated with these return flows and re-use for agriculture or
for other purposes is deterioration of water quality, although quality
changes cannot be analyzed without associated quantity considerations.
Water for re-use, then, has a diminished quality value which could
offset its quantity value.
A major hypothesis is that the re-use of water through return
flows shifts the cost of water quality deterioration from the upstream
to the downstream user. The upstream user applies water and makes
decisions without regard to disposal costs of such wastes as irrigation,
livestock, pesticides, andherbicides; thus, in terms of economic cri-
teria he seemingly overproduces since his costs are understated. In
-------
154
turn, the downstream user is affected by the quality deterioration
from upstream; his costs are overstated and production is less than
an economical optimum otherwise. To the extent that irrigation return
flow influences quality deterioration downstream, the costs of quality
deterioration are transferred from one unit or area to another through
the technical or physical linkage between the production processes.
The market price system does not reflect these conditions nor adjust
for these economic inefficiencies and incidences of costs and benefits.
Arrangements outside the regular market operations are required to
accomplish improved efficiencies and otherwise to alleviate problems
associated with water quality deterioration.
Absence of property rights in water quality complicates greatly
economic and institutional analyses and solutions to water quality prob-
lems. Water rights, compacts, etc., almost universally have been
expressed in terms of quantity. Responsibilities and obligations sel-
dom are attached with reference to water quality.1 Thus, if an up-
stream irrigator develops and applies water, part of which returns to
the stream in lower quality, the downstream user still has his quantity
right but the quality may be less than satisfactory. In an economic
analysis of such conditions, several questions need be answered, such
as:
a. How are costs and damages to be assessed and collected?
b. What are the net diseconomies ?
c. What remedial measures are warranted and feasible ?
Analytical techniques
A substantial need exists for continued efforts in improving and
developing analytical techniques for appraising the economic impact of
water quality deterioration in irrigation return flow. Farm and enter-
prise budgets have long been the basis for estimating benefits from
irrigation development. The Bureau of Reclamation has utilized them
extensively, as have agricultural economists generally in appraisal of
resource development. However, budgeting is cumbersome in terms
of the range and number of situations that can be analyzed readily.
This technique is not especially useful either in considering alternative
major uses of resources, in estimating secondary or side effects, nor
in estimating effects on related sectors of the economy.
are exceptions. For example, the New Mexico-Co lor ado Com-
pact on the Rio Grande does have a quality clause and the State Depart-
ment has imposed a maximum, of 1, 500 mg/1 on Colorado water de-
livered to Mexico.
-------
155
A more recently used technique for regional and small-area
analyses is the inter-industry input-output (I-O) model. The Colorado
Economic Base Study (219) which utilized the inter-industry technique
is the most notable analysis to date involving agriculture and other
water uses, water quality, and return flow problems. This analysis
shows inter-dependence among sectors of an economy. It estimates
total economy effects of a change in one or more sectors. It utilizes
gross magnitudes, for example, output (income), or employment. It
does lack inter-regional analysis usefulness. It does not provide a
measure of net benefits. It is expensive, especially in terms of meet-
ing data needs. There may be some problems in the input-output tech-
nique if only a small area were involved in the analysis. However, as
part of a larger I-O model, appraisals can be made for relatively small
areas and adjustments.
Economic projections
Feasibility of control measures, farm income appraisals,
management plans, and other aspects of benefit cost analyses usually
extend over at least a 50-year period. A major current effort on
national and regional projections is sponsored by the Federal Water
Resources Council. The Office of Business Economics, U. S. Depart-
ment of Commerce, has general leadership and is directly responsible
for the non-agricultural projections, including population, employment,
and income. Economic Research Service, U. S. Department of Agri-
culture, is responsible for agricultural and forestry projections, the
latter in cooperation with the U. S. Forest Service. Projections are
included for 1 67 economic areas covering the United States and for
hydrologic sub-regions within each water resource region. Type I
studies of the Water Resources Council should be useful for appraisal
of the impact of deteriorated quality of irrigation return flows. Addi-
tional adaptations are needed however, for these small-area analyses.
Literature is available on interest-rate considerations. A wide
difference of opinion is apparent among economists and others as to
the appropriate rate or rates. A proposal for a substantial adjustment
upward (from 3-1/4 percent to 4-5/8 percent in 1969) is under consider-
ation by the federal government. This rate will be specified for public
investments and project features. A different rate should likely be
applied for private capital involved, but difference of opinion exists as
to whether this rate should differ from the public rate, and if so,
what the rate should be.
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Agricultural Income Impacts
The irrigation return flow problem basically involves an area
approach. But in agriculture, the farm is the major unit and a source
of quality change and therefore, is the major point of emphasis.
Production and damage functions
Several state and federal agencies either have completed or have
in process fundamental and significant data relating salinity and water
quality to crop production rates. This material was used by Pincock
and Stewart in the Colorado Economic Base Study (220, 221). The
reports contain a large portion of the available material. Pincock
found major gaps in available data of the kind needed for farm income
analyses. Application of experimental data to actual farm conditions
seemed impossible in any direct sense because managerial adjustments
on farms removed direct comparison potentials; thus, his estimates of
quality impact were necessarily based on informed judgments. Inform-
ation is needed on production and damage functions (experimentally and
in experience), with several crops for various levels of water quality,
water quantity, soil quality and climate. There has been much valuable
research accomplished on an experimental basis relative to production
functions of specific crops under different water and land quality condi-
tions .
Farm incomes
Estimates of farm incomes are needed for relevant levels of
water quality under soil, cropping patterns, water use, etc. , condi-
tions relevant to the return flow situation at hand. There is need for
physical data and price and cost information and projections. Much of
this data could be derived from farm enumerative surveys, as a basis
of economic analysis of return flows. Information is also needed on
the effect that deteriorating quality has on land values. Although de-
creased land values obviously would have an adverse effect on land
owners, especially if they had occasion to sell, yet these lower net
incomes could be capitalized into lower values and new land owners
might be less adversely affected than appears from an income criterion,
assuming that water quality, or soil, or both, did not continue to dete-
riorate. Projection of water availability, crop requirements, efficiencies,
and net disappearance of particular land and water qualities are critical
inputs to the income analysis, both at the farm and area levels, and to
appraisal of farm adjustments and courses of action.
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Profitable farm adjustments
Profitable adjustments to various levels of water quality need
to be appraised. Adjustments made by farmers in actual operations
needed to be identified and evaluated as part of this total process.
These analyses are needed for appraising economic impact on agri-
culture and other segments of the economy from various changes in
quality deterioration. The estimates of income and other effects are
basic to feasibility appraisals and to adjustment programs. Estimates
are needed of the effect on upstream users who do not incur quality
control costs. In turn, there is a need to know the impact of quality
deterioration downstream as well as the kind of adjustments these
users would make. Such analyses have not been made except in the
Colorado Economic Base Study.
Other Impacts
The impact of water quality deterioration associated with return
flows can be widespread. We note briefly here both domestic and
industrial uses and then, in more detail, impact from an area or
regional standpoint which involves all water uses. Both domestic and
industrial users might incur added costs in using water polluted from
return flows. Since water usually has higher values in industrial and
domestic uses than in agricultural use, and involves smaller quantities,
several courses of action are more available than in the case of agri-
culture.
The downstream relationship gives rise to the basic externality
problem. Incidence of benefits and costs arise. Institutional and
financing arrangements for adjustments are prominent problems. Cost
allocations are difficult. Non-economic uses of farm and other re-
sources arise because of distortion of cost structures by disassociation
of benefits and costs. Some conceptual work is available on solution of
the externality problem. But concensus does not exist on the promi-
nent proposals.
Local and regional economies
Changes in the quality of water used for agricultural and other
purposes have impacts on local and regional, as well as national
economies. These changes produce either beneficial or adverse effects,
depending on their nature and magnitude. In resource evaluation termi-
nology, the effects are called secondary or indirect benefits or costs.
Like primary effects, they can be tangible (monetary) or intangible.
Public resource development agencies have long recognized these
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effects in their project evaluations; e. g. , the Bureau of Reclamation
has an explicit procedure and criteria for assessing dollar value and
for describing non-monetary effects. Senate Document 97 (222) rec-
ognizes secondary benefits in public investments to a greater extent
than did the Interagency Report (223). Views vary, from no recogni-
tion of secondary effects to placing great importance on them'but they
have gained increasing attention in recent years, A controversy
hinges primarily on the question of national vs regional goals in
resource development. No one doubts the local worth of resource
development, but it is argued that these effects cancel out at the
national level. Even assuming that the latter view is correct, a
particular development can be considered at the local level in terms
of effects, beneficiaries, and payments of investment and project
costs.
The input-output model is a means of recognizing and estimating
total effect on local economies of particular investments. This model
includes total economic activity and recognizes inter-relationships
between sectors and industries in the economy and the impact that
each has on the other. Basic direct effects or damages are estimated
outside the model and injected to arrive at a new transaction table and
new set of coefficients. The model then estimates total indirect effects
through the economy. Some direct and all indirect effects are expressed
in total gross output (dollars), and to the extent that this measure serves
the purpose, procedurally it is an adequate approach. However, gross
value output does not meet many needs in resource evaluations. A net
change is frequently needed. It is not evident yet whether data and co-
efficients that are available for I-O analyses are sufficiently refined
to permit the degree of "accuracy'r needed with reference to an invest-
ment that may be small compared with total economic activity in the
model.
The Colorado Economic Base Study utilized the I-O model for
estimating damage costs under various quality situations. Both direct
and indirect damages were defined for two fairly large sub-basins.
Alternative Courses of Action
Appraisal of these alternatives is part of the income and adjust-
ment features reviewed above. The major possibilities include:
1. Decreased total gross output -- lower incomes and
crop yields.
2. Treatment of water.
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3. Dilution through increased purchase and
use of water.
4. Bypass channels resulting in less •water of
improved quality.
5. Other increased input and consumer costs.
6. Use of less water in upstream areas.
7. Enforcement of standards in return flow quality.
This alternative is dependent on several others
in the listing.
Where alternatives are physically feasible, economic appraisals
are needed. Where only one possibility exists, estimates are needed
of the economic impacts of this course of action. The Colorado
Economic Base Study (219) appears to be a single effort of this kind
where agricultural water quality problems prevailed. The appropriate
value or price of water to use, especially in analysis of dilution and
treatment alternatives, poses a difficult problem in many areas.
Frequently a water market is not operational, so actual market sale
prices are not available. Payments and costs being made or incurred
by companies and districts probably do not coincide with actual water
values or with prices that would prevail in an active market. This
problem proved to be especially troublesome in the Colorado Economic
Base Study.
"Optimum" levels of water quality
Analysis of this goal would be part of the appraisal of alternative
levels of water quality and of alternative courses of action. It is sig-
nificant in establishing public standards of water quality. Both economic
and institutional elements are involved -- what is economically feasible
and desirable conditioned by institutionally permissible adjustments and
standards.
Levels and enforcement of water quality standards should be con-
sistent with established national and regional goals of economic effi-
ciency and other criteria. Achievement of this consistency involves
consideration of both benefit and cost functions. If the standards do
not achieve this purpose, serious mis allocations of resources could
result. To date, standards have been set on the basis of judgments
and criteria largely other than economic, at least in an explicit sense.
This situation applies especially to agriculture and quality of water.
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Institutions
Physical and economic appraisals are basic to water quality
appraisals and adjustments. However, farmers and others frequently
encounter obstacles and limitations in effecting adjustments even though
desirable economically. Institutions that either hinder or help relate
to investment and operating capital, water shortages, water rights and
appropriate organizations for group action. The Water Quality Act of
1965, Public Law 89-234, amended the Federal Water Pollution Control
Act to provide for the establishment of water quality standards for inter-
state water. Levels of quality established could influence economic
activity in areas where maintenance or improvement of quality poses
difficult adjustment problems to the users.
Selected Research and Literature on the Economies of
Irrigation Return Flow and Water Quality
The Colorado Economic Base Study was a joint effort of FWPCA,
several universities, and the Economic Research Service, USDA (219).
It was a large investigation in terms of budget, personnel, time, and
content. The input-output inter-industry technique was applied.
Separate base and projections analyses were made for six sub-basins
within the Colorado River Basin. The overall objective was to develop
an economic framework within which appraisals could be made of im-
pacts of water quality deterioration and water quality control measures,
investments and adjustments. The study and technique were extended
to estimate damages for two sub-basins -- Lower Main Stem and Gila --
where the analysis indicated that water quality deterioration would
further constrain economic activity in 1980 and in 2010. This study is
significant both in procedures and content. In the two sub-basins where
quality deterioration may be substantial in the projection years unless
total water supplies are augmented, four major results were identified:
1. Reductions in output and total gross income
in agricultural sectors.
2. Increased cost of more water.
3. Increased household purchases of soap.
4. Increased treatment costs in industrial
sectors.
By introducing costs and other direct effects into the input-output
models under no quality constrained conditions, the indirect effects of
lowered water quality were estimated for each of the above results in
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these two sub-basins. The study did not analyze specifically the im-
pact of alternative adjustments or control measures on areas or sub-
basins. Nor did it specifically analyze the return flow problem. How-
ever, in these sub-basins, irrigation is the major water use and re-use
of lower quality return flow -water is a major problem.
As a segment of the Colorado Economic Base Study described
above, the Economic Research Service made an analysis of agricultural
impacts with reference to the Wellton-Mohawk area in Arizona (220).
Basically, Pincock analyzed the production, .cost, and income effects
on farms in this area under three levels of water quality: 800 mg/1,
920 mg/1, and 1, 233 mg/1. He used a crop enterprise and farm budget
approach. The analysis was based largely on experimental data and
informed judgments with respect to production and damage functions.
Briefly his conclusions were:
1. No cropping pattern changes would occur within
the range of 800 to 1, 233 mg/1.
2. Additional leaching water would not be needed.
3. Major effects would be decreased crop yields.
4. Net damage effects would be small at 920 mg/1
but large at 1, 233 mg/1.
Pincock did not consider the return flow problem, although use
of return flow water is a primary element of deteriorated water quality.
His study does point up the adequacy and inadequacy of present data for
this kind of analysis with reference to the Lower Colorado River Basin.
This study was a basic input to the appraisal of damages to agriculture
described for the Colorado Economic Base Study.
Kneese has been a major proponent of the "basin firm" concept
for internalization of external economic effects (224). This approach
applies certain management principles of farm or business firms to a
total basin, to gain maximum benefit in dealing with water quality prob-
lems in the basin. Several possibilities exist for dealing with economic
externalities:
1. Internalize the externalities.
2. Adopt a system of charges or payments.
3. Enforce water quality standards.
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With reference to irrigation r.eturn flows, the "basin firm" con-
cept would likely require group action which action could accomplish
adjustments through a system of charges, incentive payments, and
enforcement. Others have recognized the potential. Castle (225)
emphasizes the need for institutional or administrative design to
accomplish what the market fails to do. Wantrup (226) has questioned
the usefulness of the "basin firm" concept. Rather, he suggests that
policy should emphasize economic functions employed by firms which
cause pollution. Among these policies and functions are:
1. Prohibit certain production functions.
2. Require certain production functions.
3. Impose quality standards on discharge.
4. Have unified collection and treatment of
waste by public, e. g. , irrigation drains.
5. Give economic incentive through tax
relief, loans, rebates, grants, etc.
Research in process
Some encouragement with respect to economic alleviation of
water quality problems is to be found in current research (227). Titles
of research projects sometimes include "irrigation return flows. " How-
ever, one concludes from the research currently under way that this
subject is not yet a major element of the total economic research pro-
gram.
In the past several years, the U. S. Department of Agriculture
in cooperation with land-grant colleges has devoted substantial atten-
tion to delineating significant research problem areas including:
1. Management of salinity and saline soils -- prob-
lems relating to salt accumulation, leaching, and
degrading water downstream.
2. Economic and legal problems in management of
water and watersheds. Among items of emphasis are
improved benefit-cost methods for identifying and
quantifying relative economic efficiency of development
and relation to national needs and objectives, and im-
proved legal and institutional arrangements, including
cost-sharing.
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3. Alleviate soil, water and air pollution. Character,
intensity and causes of pollution from agriculture
and forestry, alternative methods of reducing and
controlling, and use of low quality water for agri-
cultural purposes.
Secondly, a review sponsored by FWPCA of research needs is
noted (229). This report emphasizes the lack of adequate research
and data. Socio-economic problem areas include pollution abatement
costs, water treatment costs, and benefit-cost studies of economic
effects. The Western Agricultural Economics Research Council of the
Western Agricultural Experiment Stations, through its Committee on
Economics on Water Resources Development, has recommended and
obtained approval for a regional research project on the economics of
water quality.
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LEGAL ASPECTS
Legal Framework for Irrigation Water Use
Orderly water development and stable and efficient utilization
over long periods of time require the establishment of ground rules
setting equitable bounds on the way water can be used. Such rules or
laws must ideally encourage the full development and use of water re-
sources while prohibiting wasteful and harmful practices. They
should be non-discriminatory and durable in accommodating transitions
in use, to help avoid the danger of conflict developing.
Generally, water has been considered to be the property of the
public, yet made available for individual use while protecting both
public interest and individual rights. Certainty of the right is a basic
necessity in any water law. Water has been viewed from the beginning
of American water jurisprudence as a right of property, to which
protection is afforded by provisions of the federal and state constitu-
tions. For its stability, utility, and transferability each water user
deserves a clear statement of his rights through a system of title
recognized under law. To this end, individual states have evolved
statutory and administrative procedures for acquiring water rights,
considering protests, specifying conditions of forfeiture, adjudicating
water rights, and maintaining a central registry of water rights. These
state-developed codes have been and still are an indispensable basis for
decision and action to permit orderly and equitable expansion of uses
•while carefully safeguarding existing rights--whether these be individ-
ual, mutual, state, or federal. Quality always has been a considera-
tion in water rights, but its emphasis is of more recent date. Popula-
tion pressures naturally prompt water quality concern, including
regulations.
Legal and hydrologic compatibility
To be durable, a water law system must have a conceptual
structure harmonious with hydrologic laws and principles, including
considerations of quality as well as quantity. The legal character of
water rights must be developed from an understanding of the nature,
occurrence and movement of water. Water is characterized by
dynamism, complexity, and unity. All three characteristics have
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created trouble for water law-makers. Law can be more precise when
dealing with such fixed quantities as real estate. The transient, cyclic,
and renewable nature of water requires a different adaptation in law.
In an attempt to simplify the complex and poorly understood inter-
relation of water within a drainage basin, courts have classified water
in various ways. Unfortunately, such classifications often are com-
pletely unharmonious with the existing hydrologic relationships. Water
rights based on hydrologically unsound classifications and definitions
are insecure and lead to confusion and additional litigation.
All water in streams, lakes, swamps, and underground comes
from precipitation. Topography, soil porosity, geologic formations
and configurations, and other factors affect the path and rate of move-
ment of water over and through the soil mantle in response to gravity.
These factors also affect the mass inputs of dissolved and suspended
materials carried in a water supply. Flowing in natural patterns,
water is a transporting agent for these substances. This transport
aspect'of the hydrologic cycle becomes crucial in consideration of water
quality management. Water is subject to continuous evaporation and
transpiration •which decrease its volume as it moves. Hydrologically,
a river is in unity with the landscape it drains. The visible river is
only a part of the complete drainage system. Surface streams and
rivers are connected with "ghost rivers" that flow slower beneath
streambeds and through the porous media of the entire watershed.
It is in this connotation that we speak of the "hydrologic unity" existing
in a river basin. Many courts in their decisions obviously have failed
to grasp this notion.
A river system has a "dynamic equilibrium" in its pattern of
occurrence and movement of water. This pattern is specific to a
particular river system, giving rise to the hydrologic truism that
"every watershed is a law unto itself. " But legal adaptation to this
has been difficult.
Since natural flow patterns often do not conform to desired use
patterns, man modifies the natural system. Without such modification,
social and economic potentials could not be realized. Changes in flow
pattern, made by the construction of physical works to store, convey,
and treat water, are translated to downstream locations. There may
be increased loss of pure water to the atmosphere, and generally there
is an addition of suspended and dissolved substances. As water is
returned to the system after a particular use it becomes available for
re-use downstream, but the original flow pattern is modified, to vary-
ing degrees, in terms of quality, quantity, and regimen. Certain uses
have an imperceptible effect on downstream uses, but others have a
significant effect, on the amount, timing, and quality of water available
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to subsequent users. Therefore, water development and administra-
tion must consider the total system. Legal boundary conditions should
not restrict the utility of the resource, but rather maximize it, and
provide positive protection and certainty to each user in regard to
later uses.
Water rights doctrine
Water law in the West is mainly irrigation law, although mining
activities had an early influence on the laws (23). Irrigation generally
involves substantial diversions from streams or other sources and
conveyance to selected lands regardless of whether or not these lands
are contiguous to the source of water. It has been believed to be in
the public interest that every possible acre of land be irrigated. Thus,
there has been an intensive and extensive use and a multiplicity of uses,
so far as the water supply has permitted. "It is understandable, there-
fore, that the water law of the western states presents a complexity of
pattern and a fullness of development not to be found in the law relating
to water in the East" (10). On the other hand, those regions of plenti-
ful rainfall have had a natural distribution of water which precludes or
reduces the need for irrigation. In such regions the emphasis has been
on the right of the contiguous landowner to have the water flow past his
property in approximately its natural state, substantially undiminished
in quantity or quality. When one contemplates the variety and kinds of
economic enterprises requiring water at specific locations in any region
it is extremely difficult to see how any portion of the United States could
survive under a law that would forbid use of water on land or at locations
not contiguous to a stream. Actually, doctrines prescribing this gen-
erally have been modified or circumvented by legislative enactments in
most states as necessity for more reasonable interpretations have
developed.
Riparian and appropriative doctrines
There are two basic systems of water rights in the United States:
riparian and appropriative. They are extensively treated in many
scholarly writings (10, 230, 231). The doctrines fundamentally are
quite different. The essential differences have been outlined by Clark
and Martz (232):
In both riparian and appropriation doctrines, a
water right is regarded as "usufructuary, " a right of
use and not an interest in the corpus of the water supply.
But riparian rights'-originate from land ownership and
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are dependent on physical location, i. e. , contiguity
of land to a body of water. Appropriative rights do
not depend upon land ownership. They are acquired
by actual use of the supply and do not exist without
such utilization. Riparian rights, in contrast, remain
"vested" though unexercised. In general, riparian
owners may not exercise their water rights on
riparian lands. Appropriators may use the supply
without regard to location.
Appropriative rights are fixed and certain as to
the amounts of water allocated because of the principle
which entitles the senior water right holder to take his
allotted quantity before junior appropriators may take
theirs. In short "first in time, first in legal right"
governs. Riparian rights are not lost by non-use be-
cause they are an interest in particular land. Appro-
priative rights are terminated by non-use or abandon-
ment because their legal existence was created by
actual use only.
There are many extensions and refinements to the two doctrines.
The law of appropriation has the same basic ingredients in each state.
The riparian doctrine has undergone modification which permits more
comprehensive use of water. Such modification has brought the doc-
trine closer to the appropriation doctrine and in more realistic com-
patibility with the hydrologic facts of life. The degree of modification
in each state seems to be correlated •with the pressure for water devel-
opment and management in the economic and social growth of the state.
In arid areas where good land is much more abundant than water, the
appropriation philosophy of water rights generally has been adopted.
In locations where resources other than water were limiting factors to
economic development the riparian doctrine or common law has been
the basis for water rights. While the jurisdiction of either the appro-
priative or riparian doctrine has been paramount in most states, some
have recognized both systems. Inasmuch as these two systems of law
are quite different it was inevitable that in states recognizing both sys-
tems many conflicts and extensive litigation developed. The riparian
rule is a judicial rule. Legislation on riparian water rights has either
abrogated, limited, or modified the doctrine. The doctrine of appro-
priation, on the other hand, is based upon specific statutes which orig-
inally codified local customs. Court decisions have dealt principally
with interpretations of the customs and laws and with constitutional
questions (232). Many courts in upholding the riparian doctrine have
viewed the subject from the standpoint of private property rights.
Recognition of public interest has been a slow and difficult process.
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Though far from perfect, the doctrine of appropriation has proved
more workable than the riparian doctrine in development and use of
water resources. It is far less restrictive, affords greater protection
to investments in water enterprises, and includes the essential element
of "beneficial use. " The aim of the latter requirement is to safeguard
public interest in use.
State water right structure and administration
Originally, all means of appropriating water (in western streams
at least) were non-statutory; that is, there was no federal or state
statute outlining the steps in acquiring the right. Local customs
governed the appropriation of water. With further use of water and the
impetus of federal development through the Carey Act, the Desert Land
Act, and the Reclamation Act, formal appropriation procedures became
necessary. Thus, a complete administrative system pertaining to
water rights in the West originated in the need for legal procedures to
control the use of water resources. Elwood Mead (232) helped to
pioneer a complete state system of supervision over the appropriation,
adjudication, and distribution of water. The administrative system
Mead began in Wyoming spread rapidly to other states. While most
states have undergone occasional reorganization to discharge statutory
functions more effectively, the conventional functions have remained
about the same. Generally, these functions are vested in a state engi-
neer as the chief administrative officer. With statutory guidelines, he
makes decisions on applications to appropriate water, but his actions
are subject to judicial review. The state engineer also has power to
administer the water supply, both surface streams and groundwater,
at any given time and place, considering the hydrologic variability of
the system and the priority needs of the state. In some states these
functions are performed by a board. An aspect of increasing value in
a centralized administrative procedure has been the maintenance of up-
todate records in a single state office.
Interstate compacts
Compacts between states have been executed with respect to the
use of water of several interstate streams. Only congressional consent
validates such a compact. It is drawn up by representatives of the
states concerned, with the concurrence of a representative of the
federal government; ratified by the respective state legislatures, and
approved by an act of Congress.
The Supreme Court has recommended that the differences between
states concerning the use of their common rivers be settled by compact
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where possible. In various instances this has been done. In other
instances protracted negotiations failed to compose the differences
and court action was resorted to. Court action, or judicial apportion-
ment, is sometimes referred to as the "contentious approach.1'1 Inter-
state compacts are said to provide the "cooperative approach" to the
same problem. In the case of Colorado vs Kansas, 320 U.S. 383, 392
(1943) the Supreme Court said:
The reason for judicial caution in adjudicating
the relative rights of states in such cases is that, while
we have jurisdiction of such disputes, they involve the
interests of quasi-sovereigns, present complicated and
delicate questions, and, due to the possibility of future
change of conditions, necessitate expert administration
rather than judicial imposition of a hard and fast rule.
Such controversies may appropriately be composed by
negotiation and agreement, pursuant to the compact
clause of the Federal Constitution. We say of this case,
as the court has said of interstate difference of like
nature, that such mutual accommodation and agreement
should, if possible, be the medium of settlement, in-
stead of invocation of our adjudicatory power.
The Colorado River Compact of 1922 was probably the first major
interstate participation in regional water supply allocation. Significantly,
this compact superseded the "first in time first in right" principle by
preserving a defined amount of the river basin water supply for future
development and use in the so-called Upper Colorado Basin states.
This agreement made possible the immediate construction of Hoover
Dam and Lake Mead to start meeting immediate demands of the lower
basin area. The basic allocations of this compact have survived a
40-year lag in upper basin utilization of the compacted water supply.
It is important to note that storage and irrigation return flow are looked
to by the upper basin states to meet downstream compact commitments.
Most regional water development to this time has been accom-
plished after compacts and/or judicial decrees have been consummated.
There probably are more than 20 interstate water compacts dealing
with various aspects of water allocation and development. Two-thirds
of these are in the West. Two fundamental concepts seem to permeate
all compacts or decrees having to do with interstate water control and
allocation. The first is an unequivocal recognition of existing valid
water rights in force under the applicable laws of the specific states
involved. The second requires protection to a "basin of origin" in the
form of a fair water allocation and a protection of that allocation in the
operating arrangement dealing with unappropriated water, regardless
of time of future use (233).
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Federal Views on Water Rights
In recent decades much has been said concerning federal-state
relations in water rights. Actually, there is no federal law of water
rights in contradistinction to that of states. Only the states have
developed codes and institutional machinery to regulate the use of
water. The uneasiness or controversy that has been engendered is of
fairly recent origin and stems from Supreme Court decisions and
Justice Department assertions that unsettle traditional state under-
standings .
The federal view has its basic premise in the supremacy clause
of the Constitution which prevents states from limiting the authority of
the United States over its own property. The federal view is largely
one of sovereignty which questions whether a state should have the
right to regulate and control the actions of the federal government in
water matters and whether the application of federal laws of waters
within a state should be limited by the laws of a state. Both state and
federal governments have similar objectives in serving the public
interest. Water development programs are not for the aggrandize-
ment of any sovereign entity, either federal or state. Hence, there
is no necessity for any real clash between federal and state govern-
ments. The focus should be on providing legal and institutional
machinery to facilitate and promote orderly and equitable water devel-
opment in the public interest.
One of the issues of federal-state controversy is concerned with
compensibility of water rights taken by the United States relating to
any navigable streams. It seems obvious that government control
over "navigable waters" would be meaningless if the tributaries could
be dried up one by one so that eventually the navigability of the stream
could be destroyed. Hence, it is necessary for the federal government
to have control over non-navigable headwaters as well. The federal
position is that it should not have to pay for what has always been its
own property. Being the original proprietor of the public domain the
United States acquired all water rights on those lands. Justice Depart-
ment attorneys claim, therefore, that unless conveyed away, such land
and water rights are still U. S. property, and any such conveyance
must have been by an act of Congress under the property clause.
While certain federal statutes such as the Desert Land Act, provide
that water rights may be acquired by complying with state laws, this
does not invalidate the federal argument that ratification of state con-
stitutions did not transfer authority to convey title to water. One
still proves his title to water rights as he proves his title to land by
tracing his title through intervening owners to the United States of
America. In instances where just compensation has been an issue
the federal government has asserted that unless public rights have
been relinquished there is no obligation (234).
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Another major problem relates-to the federal claim of water
rights appurtenant to lands reserved from the public domain. Winters
vs. United States (207 U. S. 564, 52 L. Ed. 340, 28 Sup. Ct. 207) has
been described as the historical antecedent of present proprietary claims,
This case had the effect of establishing that a reservation of lands by the
United States also reserves such water as may be required to carry out
the purposes of the reservation. While the Winters case had to do with
an Indian reservation, Justice Department attorneys contend that the
power of the United States to reserve water for lands withdrawn extends
to all types of reservations. In the Santa Margarita Water Company vs.
United States, the government position was stated:
The United States of America claims that the title
to the rights to the use of water upon the reserved lands
of the U.S.A. resides in it and has never been conveyed
away. Those rights are part of the land and may be ad-
ministered by the U.S. A. independent of the laws of the
several states. They are in some regard similar to
state-re cognized riparian rights as use does not create
them and non-use does not cause their loss, yet to the
extent they are required to meet the beneficial uses for
which they were reserved they are not subject to diminu-
tion by appropriative or riparian rights which vested sub-
sequent to the reservation. They differ from appropriative
rights as they exist as parcel to the land and require no act
on the part of the U. S. A. to initiate or maintain them.
These rights have been reserved by executive orders and
statutes.
The states have pointed out that their constitutions provide either
for state ownership or state plenary power over all water within the
state; that such constitutions were ratified by Congress when the states
were admitted to the Union; and such action constitutes in substance, if
not actual conveyance by the Congress, at least a compact with the ad-
mitted state. States also refer to a long line of congressional acts
recognizing the state laws of water as further confirmation of the inten-
tion of Congress to treat the waters of non-navigable streams as being
under state jurisdiction. Viewed from the states' position, the federal
government is now asserting control over and ownership of all the water
in the western United States arising on federal reserved lands so as to
put in jeopardy water rights recognized under state water law.
It is rather significant that both the state and federal positions
seem to be conceived in terms of power and authority. For the past
several years legislation has been introduced in Congress to declare,
reform, clarify, amend, modify, confirm or restate the state and
federal relationship in water rights. The struggle is basically over
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who becomes top dog so far as water development is concerned. To
date none of this proposed legislation has become law. Based on con-
siderations of constitutional law, the federal position may be rather
formidable. In terms of logical validity in squaring with the hydrologic
facts of life and the purpose of law and policy in the orderly and efficient
development of water, the federal position leaves much to be desired.
It leads to the application of unsound principles in the development and
use of water resources. Claims based on appurtenance to federally
owned land are a throwback to the riparian doctrine of water rights
which has been found quite unsuitable in promoting efficient water
development. It is a selfish position in that reserved amounts in fed-
eral ownership are unspecified in quantity, in nature of use, and in time
when uses are to be initiated. In most western states the reserved
federal lands are generally upstream from locations where most water
uses occur under rights perfected under state law. Consequently, any
capricious use or development of waters appurtenant to federal lands
could alter the pattern of flow previously existing. A cloud of uncer-
tainty develops over the rights of any users downstream from a federal
reservation whose rights may be subsequent to the reservation. If the
federal government has reserved unspecified amounts of water, for
yet-to-be-determined purposes, which may be initiated at unspecified
times, how do state planners tell how much water remains for develop-
ment by non-federal interest? Must available supplies be wasted pend-
ing the time that reserved water may be ultimately utilized ? How can
individual states guarantee that interstate compact obligations can
continue to be honored ? Can recently constructed projects pay out
before the claimed reserved water is utilized? How can managers,
planners, and administrators integrate, coordinate, and optimize
water uses in a total system context if the unspecified reservation of
water leaves a "floating" boundary condition ? If state developed codes
for water allocation, protection, and definition of water rights are
abandoned, what new and better ones are advanced by the federal
government to replace them? It appears that the Justice Department
-- an agency somewhat remote from real problems of water resource
development, and having no administrative responsibility for a federal
rights law if such were forthcoming --is choosing to live by outmoded,
outdated, and unworkable principles -- unless, of course, all future
water development is to be 100 percent federally accomplished.
General Rules of Law Relating to Waste,
Seepage and Return Water
There are only a few court decisions relating to the acquisition of
rights in the re-use of water (235). A search of the literature bears out
the relative silence of the law as relating to the acquisition and disposi-
tion of return water. Legal periodicals from I960 to date indicate al-
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most no information on the subject. The following summary has been
based on exhaustive studies made on the subject by Wells A. Hutchins
in cooperation with various western states in producing a number of
volumes summarizing the law of water rights in the West (235-243).
Owners' rights on lands of origin
Continuance of supply. As a general rule, the owner of the land
on which waste and seepage waters originate and from which they flow
to other lands is not required to continue the conditions that lead to the
supply of waste and seepage water. Exceptions to this rule may result
when a permanent right to the use of waste water is obtained by purchase
or grant, or if discontinuance of the supply is done wantonly or to harm
another user. It may also be defeated by estoppel. Long continued use
of water leaking from defective diversion works may result in the down-
stream appropriator obtaining a right against the owner of the works.
Recapture. The original holder of a water right who has never
released title to the corpus of the water diverted in the exercise of his
right may refuse to allow such water to pass beyond his land.
Water from a different watershed may be recaptured within the
boundaries of the original project even after discharge in the natural
stream channel that is being used as a temporary conduit.
A party cannot reclaim water that is considered abandoned or is
discharged without intent to recapture.
Discharge of waste water. The right to discharge waste water
upon other lands has been acquired by prescription. The right to dis-
charge water into a water course is allowed provided it does not result
in injury to lower landowners. Anything in excess of reasonable and
non-injurious discharge is considered wrongful, but invasion of a
lower landowner's rights maybe prescriptive.
Users' rights to waste and seepage water. Generally, the same
principles apply to the appropriation of waste, seepage and foreign
water released into a stream with no intention to recapture as to natural
flow. Waste, seepage, and foreign water is generally not subject to
riparian claim in appropriation or dual system states. Since use of
waste water is generally made after it has left the land and control of
the original owner, in most cases it is impossible to obtain rights to
such water by prescription. In most cases the use is either permis-
sive or is not challenged by the original owner or user because he is
not concerned with the use of water after it leaves his premises.
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Return water
Approprlability. On many sources, including watersheds other
than those in which it is originally diverted, return flow is considered
an important factor in the supply for downstream users and it is sub-
ject to appropriation when no longer under the control of the upstream
user. Rights of a senior appropriator, whose water is supplied by
return flow from a junior user upstream, cannot change his right up-
stream above the junior so as to deprive the latter of the water.
Return water within the watershed
(a) Water returning to the stream from which diverted: Riparian
rights. Riparian lands benefit from the return to the stream of water
diverted upstream but unconsumed after use, and owners thereof are
entitled to such portions of the natural flow diverted upstream as are
allowed to flow back into the stream after use. The fact that such water
has been once used on upstream lands does not deprive it of the char-
acter of natural flow. The claim of the riparian owner upon the natural
flow of a stream is such that he may enjoin an upstream diversion out
of the watershed where the return flow cannot return to the stream
above his riparian lands. Appropriative rights. The original supply
cannot be diverted out of the watershed if it deprives a lower appropri-
ator of the use of return water upon which he has been depending in the
exercise of his appropriative right.
(b) Water returning to an upstream tributary: The right of a
riparian owner extends to the tributaries that enter the stream above
his land. Hence, the riparian owner has rights to the return flow of
water taken out of a watershed but which returns to the main stream
above his land.
Return flow from foreign water
(a) Abandoned without intent to recapture: The principle that
one cannot reclaim water that he has abandoned after rights of others
have lawfully attached is a generally applied rule of law. It is said
that the party who has released such water with no intent to recapture
it has lost all interest in the water abandoned. Some distinction has
been made, however, in the abandonment of released water as it
related to particles of water and not to the water right. Montana has
ruled that foreign water becomes a part of the stream.-
(b) Subject to appropriation: Where those who have imported
foreign water and released it into a watercourse make no claim to its
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further use, such water does not accrue to riparian owners and appro-
priators but generally becomes subject to appropriation in order of
priority by those who can gain access to it. These appropriative rights
attach only to such foreign water as has been abandoned and usually are
subject to the right of the importer to cease his abandonment thereof
in whole or in part. These rights also usually are subject to contingency
that the supply may be intermittent or may be terminated at the will of
the producer. Nevada statutes do not provide for the appropriation of
waste water unless it reaches a natural channel. The importer may sell
or otherwise dispose of his imported water at any time before abandon-
ing the same.
(c) Not subject to riparian rights: Riparian rights do not attach
to foreign water abandoned into the stream to which the riparian lands
are contiguous. Although riparian rights do not attach to the return
flow from foreign water, yet water from one tributary of a stream,
taken across a divide and discharged into another tributary of the same
stream, while foreign to the watershed into which it is introduced, is not
foreign with respect to riparian lands lying on the main stream below the
confluence or mouths of both upstream tributaries.
Rights of those who import foreign water
(a) Return flow not abandoned by producer: The fact that water
is brought into an area from a different watershed and is relinquished
or lost by discharge without intent to recapture does not constitute
abandonment of the water right. The fact that importers have abandoned
the flow from foreign water in the past is not usually taken to mean that
they must continue such abandonment in the future.
(b) May terminate abandonment after others have appropriated
abandoned water: It is a general rule that a producer of an artificial
flow is for the most part under no obligation to lower claimants to con-
tinue to maintain the flow.
(c) Right of disposal by contract: As a general rule the producer
of return flow from foreign water may dispose of the same by contract
prior to abandonment of the flow. Appropriative rights that have attached
to water abandoned in the past are not infringed upon by such acts.
(d) Exercise of right limited to reasonable beneficial use: Reason-
able use governs the flow from foreign water as well as other water.
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Discharge into natural channel. Those who bring foreign water
into a watershed have the right to discharge the same, in a reasonable
manner and without injury to others, into natural water courses.
Legal Recognition of Water Quality Criteria
In the evolvement of water law -- both case and statutory --
primary emphasis has been placed on considerations of quantity more
than quality. Nevertheless, the matter of diminution of water quality
has always been of concern, and in both the riparian and appropriation
systems of water rights there is recognition that the right to use water
pertains to its quality as well as to its quantity. Generally speaking,
however, concern has been with protection from quality loss causing
substantial harm and/or nuisance. Slight inconvenience, annoyance, or
harm not greatly impairing usefulness, has generally been considered
acceptable. The test of whether pollution complained of is wrongful
and actionable has pivoted on whether it was excessive so as to be un-
reasonable (235). Even today, most state pollution control laws try to
protect against the kinds of pollution that clearly and severely impair the
the usefulness of water courses.
The riparian doctrine of water rights has generally undergone
modifications to permit greater utilization of the flow. A strict inter-
pretation of the riparian doctrine (the natural flow theory as opposed
to the reasonable use theory) suggests the ultimate in pollution control.
"Water flows and ought to flow as it is wont to flow" is a phrase often
quoted from an early decision which sums up the basic tenets of the
riparian doctrine. Since the objective is to preserve the integrity of
the natural flow, any use that impairs the natural quantity or quality of
the water cannot be allowed. If utilization of water resources are to be
permitted or promoted then the doctrine must be relaxed such that the
right protects the holder from unreasonable interference with his use.
The "reasonable use" theory of the riparian doctrine suggests that so
long as the impairment does not interfere with beneficial use it cannot
be unreasonable. An important factor in determining the reasonableness
of pollution by a riparian use is the social value of the polluting use
compared to the social value of the injury.
Implicit in the appropriation doctrine, also, is a protection of
water quality. An appropriative right would lose its superiority if at
some point in time a junior appropriator were permitted to pollute the
water supply so as to cause substantial injury to senior appropriators.
Otherwise, the prior appropriator's right would no longer be superior.
While the protection against deterioration of water quality accorded the
prior appropriator is well established, the protection is circumscribed
by the purposes specified for the use of water under his appropriation.
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Every appropriation includes a definition of not only the quantity allowed
but also the particular nature or purpose of the use. For example, a
prior appropriation to use water for an irrigation purpose does not
afford protection of quality that may be needed for domestic purposes.
On the other hand, a permit which specifies the quantity and nature of
use implies that the prior appropriator may cause such impairment as
the use might normally be expected to cause. Thus, a prior appropri-
ator may deprive a subsequent (potential) appropriator not only by deplet-
ing the supply but also by destroying its usefulness, having impaired the
quality (244). Actually, this aspect of an appropriative right has been
negated in the case of industrial and municipal uses by separate sets of
rules promulgated to deal with water quality separately and specifically.
However, so far as irrigation uses are concerned, prior appropriators
have not been protected from deterioration in quality occurring in the
irrigation process itself. Subsequent appropriators maybe permitted
to use the water and thereby lower the quality but their use must be
beneficial and the injury resulting from the deterioration minor. As
with the riparian rule, the social interest or public interest becomes
a factor in the determination of an injury problem.
State water quality management
As water pollution problems have multiplied most states have
established control agencies separate and independent from the agency
traditionally charged with allocating rights to water use. The juris-
diction of such control agencies is generally broad, covering all water
in the state, as do the water rights agencies. Quality and quantity
problems are inseparable, and California wisely has recognized that
jurisdiction over water quality should be correlated with the function of
allocating water quantity.
Most states now include all or part of the provisions of the Sug-
gested State Water Pollution Control Act (U. S. Department of H. E. W. ,
revised 1965). Each state has developed rather strong statewide goals
in water quality management. State policies have been developed and
expressed in water codes and standards. These will not be detailed nor
reviewed here except as they enter into considerations of irrigation
return flow.
Much of the impetus for setting state standards and tighter state
regulations on water pollution has stemmed from the 1948 Federal
Water Pollution Control Law and subsequent amendments. The most
notable amendment was in 1965, known as the Water Quality Act. This
act contains provisions that illuminate some rather basic problems and
philosophical issues with water quality management, especially irriga-
tion.
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Legal Conflicts Between Irrigation Water Rights
and Water Quality Standards
The Water Quality Act of 1965 indicates that standards of water
quality must be such as to protect the public health and welfare and to
enhance the quality of water. In establishing such standards, the use
and value of public water supplies, propagation of fish and wildlife,
recreational purposes, and agricultural, industrial, and other legiti-
mate uses are to be considered. In setting guidelines for the formula-
tion of acceptable standards the Secretary of the Interior emphasized
the quality enhancement aspect by not allowing water quality to be
degraded below existing levels. While agreeing with the intent of this
so-called non-degradation policy, many states objected to the wording
of the policy since it seemed to exclude considerations of "use and value, lf
"practibility, " and "economic" and "physical feasibility." In other words,
enhancing the value of the water resources in the many uses specified in
the act may be quite inconsistent with enhancing the quality per se.
Water cannot be enhanced and degraded at the same time. A firm policy
of non-degradation ignores physical and economic feasibility of comply-
ing with such a standard. The establishment of water quality objectives
which purport to fully and adequately protect all existing and prospective
beneficial uses may result in extremely costly waste disposal. In other
words, the social costs may be increased by a strict interpretation of
the non-degradation principle. Water uses demand different levels of
quality and all water uses affect water quality to some degree. Full
utilization of a water resource requires some compromise in quality
enhancement. The non-degradation policy may be likened to the riparian
doctrine of water rights. Both emphasize "naturalness" in the extreme.
Both are unrealistic if utilization is an objective.
A strict policy of non-degradation presents a definite inconsistency
in federal programs, also. Agencies such as the Bureau of Reclamation,
U. S. Corps of Engineers, U. S. Department of Agriculture, and perhaps
several others all have mandates to promote and perfect water utilization
in ways which may cause water degradation. Both federal and state laws
recognize that the use of water for irrigation is a beneficial use. Yet,
the degradation of water quality through irrigation use is an inevitable
consequence of the physical nature of that practice.
Mulligan (245) has pointed out that:
There does not appear to be any economical and
yet fully successful method available for the treating of
irrigation waste waters in order to meet Control Board
requirements for the discharge of these wastes to sur-
face streams. In other words, it does not appear prac-
tical that irrigation return waters can be handled in the
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same manner as conventional, industrial or sewage
wastes.
In the case of sewage and industrial waste dis-
charges from a pipeline effecting a relatively limited
area, the control boards set requirements on either
the waste discharge itself or the receiving waters or
both. The discharger then constructs waste treatment
facilities to meet the requirements established. The
Control Boards check the discharge and/or the receiv-
ing waters for compliance.
Contrast this with establishing requirements for
agricultural drainage water for thousands of individual
agricultural operations covering millions of acres
presently irrigated and with potentials for irrigation
of many millions of acres more. Add to this the fact
that the effects of percolating agricultural -wastes on
groundwater quality are hard to evaluate which results
in difficulty in establishment of regulatory requirements
and you can readily see that the problem is one of great
magnitude.
Agricultural wastes traditionally are discharged with no treatment to
surface streams directly or indirectly following their cycle of use and
re-use downstream.
The expressions of policy and intent for water quality management
promulgated by Congress and implemented by the Department of Interior
are appropriate and well intended. However, policies and procedures
to implement water quality standards have shown a complete disregard
for practical considerations of existing water right structure. Setting
\vater quality standards can impair existing water rights and in effect
perform a re-allocation of water within a given stream system. The
setting of standards within a river basin may also cause imbalance in
the sharing of the burden of water quality maintenance. The Colorado
River serves as a good example, for the considerations are the same
in any river basin:
Many years ago, the Colorado River Basin states recognized that
because of the hydrologic unity existing in river basins all users should
have their interests weighed in common. They subsequently attempted
a compact dividing the water of the Colorado River among member states,
Thus, in the common knowledge that orderly economic growth of the
states served by the Colorado River System depended on having a known
water supply from which to plan its developments, the states proceeded
to divide the water. The 1922 Colorado River Compact failed to divide
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the flow of the river among individual states, but it did accomplish a
division between the upper and lower basin states, with the gaging
station at Lees Ferry as the dividing point. From the water allocated
in the 1922 compact, the upper basin states spelled out the limits of
utilization of each member state by the so-called Upper Colorado
River Compact, consummated in 1948. Since that time each state in
the upper basin has been free to re-allocate and administer the use of
its Colorado River system water to any legitimate need in attempting
to maximize the utility of available water within the limit of deple-
tion allotments.
Over the years new uses have been made of Colorado River sys-
tem water. Many more are contemplated. Each Colorado River Basin
state has made .tremendous investment in planning and development of
its water entitlement. Each has made projections and long range deci-
sions based on the certainty of their compact allocation and their water
right structure. The problems in this basin arising from setting quality
standards without reference to compact terms, hydrologic character-
istics, and water rights structure, would be tremendous. For example,
if dissolved solids concentration limits at particular points were set
close to existing levels in accordance with the non-degradation policy,
the TDS limit might well be exceeded before the depletion entitlement
of the region upstream is reached. Thus, the arbitrary establishment
of permissible salt concentrations could be in direct conflict with the
terms of the Colorado River compacts or could result in the complete
abrogation of them. Reasonable use and development by upstream
users might be restricted because of the quality standards adopted at
key points lower down the river system. To fix standards at present
levels (in terms of concentration) would place the entire burden of
quality control on those states which are still developing their water.
They could only develop at considerable expense of treating or re-
conditioning effluents.
The incompatibility problem that can arise between quality stand-
ards and water rights might be paralleled by considerations of low
flow augmentation as a remedy for deteriorating quality. As the process
of use and re-use continues, chemical, physical, bacteriological, or
thermal pollution may increase with each withdrawal. Concentrations
become highest when flows are lowest. Consequently, provision to
augment low flows, to reduce the concentration of undesirable constit-
uents, is a desirable practice. Better regulation of natural streamflow
so that dry season flows can be augmented would assure that critical
water quality concentrations are not approached so quickly. Thus, a
greater spectrum of users could be served and the utility of the supply
extended. The Senate Select Committee on National Water Resources
attempted to assess the amount of dilution water required (following
treatment) to maintain generally accepted water quality for each water
resource region. The volumes estimated were substantial.
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Despite the stress placed on low flow augmentation and its obvious
effectiveness for improving water quality, it generally has not been
recognized as a legitimate beneficial use of water under state water law.
The uses made possible by the augmentation practice would be recog-
nized, but there is no provision for appropriation of water for dilution
items. In a fully appropriated river basin where perhaps interstate
compacts apportion allowable state depletions and state laws specify
allocations to specific uses, augmentation may be possible only by re-
arrangement of existing water rights. As a result of the steady degrada-
tion in quality from upstream to downstream points, the need for flow
augmentation would appear first at lower regions. Without import,
augmentation may only be accomplished by restricting depletions at
upstream, locations so that greater flow volumes could proceed to down-
stream points. Conversely, if legitimate compacted or adjudicated
water rights for specific uses at downstream locations are subsequently
negated, not by lack of water availability but by quality deterioration,
then their rights are surely invalidated. It is quite obvious that exist-
ing water right patterns and a river basin perspective must accompany
any considerations of low flow augmentation.
The prevalent pattern of setting quality standards and implement-
ing pollution control measures without regard to vested water rights can
lead to serious conflict between and within states and regions.
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RESEARCH NEEDS AND RECOMMENDATIONS
The preceding survey of literature justifies two generalizations:
first, there is extensive literature indirectly bearing upon return flow;
second, almost no basic research has been devoted to return flow, and
only a little has been specifically concerned with return flow situations.
There is need, therefore, for research that will answer many specific
questions about quality and quantity of irrigation return flow.
New technology and continued introduction of new products such
as pesticides and detergents demand continuing research to determine,
in advance of their release for general use, any toxic effects of the
products and the quality changes that affect the environment. Consider-
able of the fundamental research, such as that conducted on pesticide
movement, degradation products, etc. , need not be directly related to
irrigation return flow in order to be applicable in an irrigation environ-
ment. But problems associated with salinity must be studied in the
irrigation system.
No attempt has been made to establish research priorities, for
gross difference exists in the magnitude of the problems. Availability
of funds, equipment, and research capability must also influence the
kind, amount, and rate of research.
Quantity of Return Flow
The quantity of irrigation return flow is dependent upon the fol-
lowing variables: quantity of irrigation water diverted; canal seepage
and bypass water; water applied; time and method of application; pre-
cipitation; soil characteristics; evapotranspiration; type of crop, and
farm practices. Each of these variables has been studied extensively,
and approximate quantitative values have been assigned to each in
relation to consumptive use of water and irrigation practices. Only a
few of the parameters, however, have been specifically related to
return flow problems. Nevertheless, with adequate data on the above
variables, the quantity of irrigation return flow can be predicted with
reasonable accuracy for most specified circumstances. Irrigation
and drainage projects are designed on the basis of such estimates.
But in any situation involving return flow, considerable effort may be
required to adequately characterize the relevant variables. Addition-
ally, while general estimates for a large river system may agree with
observed data, the total system inevitably will have localities of excess
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water and others of deficient water, as well as areas of salt accumula-
tion and leaching.
Recommendations
Past, present and planned research on the consumptive use of
water, and on irrigation efficiency and drainage, precludes the need
for general studies on consumptive use of water under the aegis of
water quality research. The quantity of return flow from irrigation
operations must routinely be included, however, as part of any investi-
gations concerned with the quality of return flow waters.
In contrast, concepts and studies related to the potential "net
depletion" of water supplies through irrigation usage have not been
adequate to its importance. Net depletion of groundwater is especially
difficult to quantitize. Diversion requirements and net depletion are
the two variables most relevant to questions of return flow quantities.
Social and economic costs associated with net depletion especially need
studying.
Quality of Return Flow
Characterization and prediction of irrigation return flow quality
are considerably more difficult than estimations of quantity, although
the two are related. Like quantity, quality is dependent upon a number
of variables. Most of these have been studied in other contexts. The
principles derived, however, permit some generalization about the dis-
solved materials likely to be encountered in return flow water under
specific conditions. Yet, there is no adequate conceptual model of how
the quality changes as irrigation water passes through the soil. Until
this has been developed, predictions of quality changes are largely
speculative. Existing data indicate such a complex relationship between
many of the variables that only further study of the specific variables
will allow the development of more precise predictive equations.
The composition and quantity of the irrigation water applied are
two determinants of the quality of return flow. Other major factors
include the degree of increased concentration of solutes in the water
and the reactions that occur between the point of irrigation application
and that of return flow. The concentration of solutes in the soil is
dependent on the timing and quantity of each irrigation application, the
salinity and type of soil matrix, and evapotranspiration. Possible re-
actions include additions of new solutes as well as" exchange and pre-
cipitation phenomena.
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Re commendation
Intensive investigations are needed to bridge the information gap
between the principles established in controlled research and theoreti-
cal calculations, and the actual changes in concentration and composi-
tion of salts in return flows as affected by the solutes in the irrigation
water, soil characteristics, and management practices.
High priority should be given to the identification of sources of
salinity entering the water of river systems. Analyses of such contam-
inant sources should provide bases for recommendations for reducing
activities which contribute disproportionate quantities of salt to each
system. Possibilities include the diversion of mineral spring waters
from entering river systems and elimination of water entering and leav-
ing highly saline, non-arable lands that provide high salt loads to stream
channels.
Leaching and Salt Balance
The movement of salt in soil water differs in water-saturated and
unsaturated conditions. Salts are leached more effectively from soil by
water applied slowly and moving through unsaturated soil. Differences
in salt movement associated with variations in rates of water applica-
tion may provide guidelines for irrigation practices that can better con-
trol salt concentration in soil. A resultant effect on the quality of irri-
gation return flow water would be inevitable.
The salt contribution fron non-irrigated areas resulting from
leaching residual salt by natural precipitation or canal seepage water
may be important in evaluating salt balance in relation to irrigation.
Decreasing diversions of water may reduce canal losses and excess
irrigation applications that may leach salt from saline deposits or sub-
strata.
Mineral springs often contribute significant proportions of salt
load carried in at least the smaller river systems. Special toxic ions
such as borates maybe traced particularly to such sources. Ways
should be sought to prevent such water from entering water of higher
quality.
No models are available on which to base any reliable prediction
of salt content of return flow water in a wide range of conditions.
Serious preliminary formulations, however, will help in identifying
systems that need more primary attention in more detailed studies.
Present models of salt movement in the soil, such as the leaching re-
quitement equation, are based on estimates of what the maximum salin-
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ity that can be tolerated by the crop or by the receiving water. Some
elements such as boron are not readily leached from the soil and are
being introduced into the water system as a result of detergent use by
home and industry.
Re commendations
A comprehensive, reliable model should be developed of salt
movement through soil profiles in relation to- changes in quantity and
composition of solutes, soil characteristics and irrigation, and other
management practices. Parameters must be identified that will permit
rapid evaluation of field situations and predictions of the quality and
quantity of return flow water under a variety of conditions.
Systems methodologies for data collection and analysis should be
developed for use in assessing the balance between water and salts
applied to an area and the quantities leaving as return flow. Amounts
entering the groundwater and/or leaving as surface flow should be care-
fully measured. The effects of climate, soils, crops and agricultural
practices should be evaluated and considered vital components of each
situation. The extent of salt removal from non-irrigated areas as a
result of canal seepage or rainfall should be evaluated in developing
salt balance concepts.
Intensive studies should be given to sources and effects of such
toxic agents as boron, in streams carrying harmful quantities and the
impact on agriculture when the water is used for irrigating crops.
The consequences of applying water at reduced rates that main-
tain soil in a less than water-saturated state need definition, particularly
as related to soil leaching and the quality of return flow.
Mineral springs and other highly saline waters justify studies as
to quantities and composition of salt contributed to stream channels.
Possibilities for plugging, disposal, or alternative uses for such saline
water merits further study.
Precipitation and Exchange Reactions
Precipitation and exchange reactions affect the quality of return
flow water and are functions of the composition and concentration of
salt in irrigation water, soil characteristics, plant influences, and
agricultural practices. It is in this area that the basic mechanisms for
understanding chemical quality must be sought. The precipitation re-
actions involve primarily calcium and magnesium carbonates, sulfates
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and possibly silicates. Carbonate precipitations are determined prima-
rily by soil pH, partial pressure of carbon dioxide, temperature, and
the concentrations of available calcium, magnesium, bicarbonate and
carbonate ions.
Precipitation and exchange reactions alter the relative concentra-
tions and thus the quality of irrigation return flows. Water carrying
heavy metals, such as acid mine wastes, may be effectively freed from
the metals on passage through soil, but the short and long-range effects
on the recipient soil have not been carefully evaluated. Lead, copper
and arsenic, for example, may have serious consequences when accumu-
lated in soil, while zinc may be retained in substantial quantity in some
soil before there is apparent crop damage.
The movement and retention patterns of such materials as fertili-
zers and pesticides are not adequately defined for irrigated soil nor are
the contributors of these pollutants to return flow from other users.
Water containing dissolved phosphates are effectively freed from
phosphate by passage through most soil. Nitrates, on the other hand,
are not adsorbed by soil and move with the water. The primary nitrate
sinks in a soil are usually considered to be plant absorption and micro -
bial action.
Re commendations
Conditions associated with the precipitation of calcium and mag-
nesium carbonates in soil should be evaluated in relation to theoretical
principles, with attention to concentrations of calcium, magnesium,
bicarbonate and carbonate in irrigation water, the carbon dioxide partial
pressure in the soil system, pH, temperature, and other associated ions
in solution. Special consideration should be given to defining the role of
magnesium and its effect on carbonate precipitation and the SAR equation
as it applies to the soil system.
Precipitation of alkaline earth silicates may sometimes be as
important as carbonate precipitation in altering the ionic composition
of irrigation return flow. The silicate composition of water and its
implications require attention.
Soil adsorption of phosphates, heavy metals, or agricultural
chemicals should be evaluated for resultant water improvement and the
effects on the adsorbing soil and on crops grown in the soil. Changes
in water temperature should be included as a variable.
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Applied studies must establish major variables and methods for
their measurement, such as will facilitate the quantitative evaluation
of changes in dissolved solutes in irrigation water during the process
of irrigation. Factors needing attention include evapotranspiration,
cation and anion exchange phenomena, water temperature implications,
plant interaction, precipitation and solution reactions, and related
changes. These studies will require the monitoring of such parameters
as the quantity and composition of pollutants in the irrigation water;
the quantity, time and method of water application; irrigation efficiency;
soil characteristics, including moisture and salt movement, its salinity
status, and the exchangeable ions and organic-biological component of
the soil; management practices, in eluding, fertilizer and pesticide treat-
ments; and environment-related factors such as temperature, humidity,
precipitation and evapotranspiration.
Translating to the Field
The vast accumulation of information on the chemistry and thermo-
dynamics of solutes furnishes an excellent theoretical background about
the complex relationships with solute changes that occur during the con-
centration and movement of salts in irrigation water through soil.
All pertinent variables must be carefully monitored, and to a major
extent, controlled in new studies. Lysimeter experiments designed to
evaluate all return flows on a year-around basis, would facilitate control
of several variables. Intensive studies under selected field conditions
with controlled soil conditions and agricultural practices should provide
results validly applicable to diverse field situations.
Recommendations
Lysimeter or controlled field plot studies should involve irrigation
of soils of identified characteristics with water of predetermined compo-
sition, under selected methods, rates and amounts of application at
specified frequencies. Selected crops should be grown under these con-
ditions and the significant factors controlled or measured, including the
quantity and composition of water percolating below the root zone.
Detailed studies should be initiated under selected field situations
in appropriate areas where groundwater originates, and where the most
significant factors controlling the quality of return flow can be measured.
The balance between water and salt applied to an area, the quantities
leaving as surface return flow, and those entering the groundwater
reservoir should receive attention. The effects of climate, soil, crops
and agricultural practices should be evaluated as vital components of the
systems involved.
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189
Modern computer techniques have permitted analyses of our
accumulated, extensive data on the composition of water of the United
States. To capitalize upon the already substantial investment in such
analyses, the data should now be further studied in relation to climate,
geology, soil, and vegetation of selected areas.
Organic Wastes
Few organic wastes have received detailed attention in relation to
quality of irrigation return flow. The effects on soil of large amounts
of farm manure, and of organic wastes on drainage water composition
needs study. Recent studies have shown feed lots to be a major source
of nitrates in groundwater. Water containing sewage or other wastes
may carry pathegenic organisms as well as decomposable organic
materials. Organic materials may improve soil structural stability
and permeability, and thus facilitate the movement of mineral elements,
viruses, and possibly micro-organisms through soil.
Re commendations
The effects of decomposable organic materials on the quality of
irrigation return flow and on the movement of such substances as phos-
phates, nitrogenous compounds and pesticides, and on the survival and
movement of such organisms as viruses, pathogenic bacteria and nema-
todes should receive detailed attention. Studies should be made on all
new pesticides to determine, in advance of their use, their persistence
in soil, decomposition products, and the general reactions in soil,
water and crops, and the resulting pollution hazards of the water com-
ing from the land.
Thermal Pollution
Thermal pollution is a problem of growing importance. The role
of irrigation in relation to thermal change is unknown. Under condi-
tions of hot surface soil tail water may be warmed appreciably. Drain-
age water percolating through soil will usually attain the temperature of
the soil substrata. The use of river systems for cooling in connection
with both fossil fuel and atomic fuel power plants is increasing. Chem-
ical reaction and solubility of salt in water are both directly and in-
directly affected by the temperature. Carbon dioxide solubility is in-
versely related to water temperature and consequently thermal pollu-
tion may initiate precipitation reaction in either stream bed or soil.
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Thermal pollution has direct effects on aquatic life. A few degrees
change in temperature may drastically alter the proportions of biological
systems. Return flows will most likely have an ameliorating effect on
temperature extremes.
Re commendations
Thermal pollution or major temperature changes should be studied
in terms of their effects on chemical changes in solutes. The role of
irrigation in thermal pollution should be determined, as a moderator of
major temperature changes as well as a positive or negative contributor
of heat.
Matching Use to Quality
Disposal of low quality return flow water often is a major prob-
lem. , Some of it may best be used for wildlife marshes and for recrea-
tion. Evidence indicates that the economic return from such use may
be high, but specifics are lacking. Information is needed on possible
locations and productive management techniques for saline lakes or
marshes, the uses to which they are best adapted, and monitoring
methods and standards to protect public health.
The combination of well drained, permeable, sandy soil, liberal
applications of water, and salt tolerant crops can permit crop produc-
tion with water commonly considered unsatisfactory for agricultural
purposes. Many possible combinations of these factors have not been
adequately evaluated.
The technology of reclaiming low quality water is currently receiv-
ing considerable, well deserved attention. The imminent water short-
ages in large areas of the western United States and in other countries
make efficient reclamation by distillation or one of the membrane
processes a highly important goal. Reclaimed water both increases
the quantity and improves the quality without increasing withdrawals
from natural supplies.
Aquatic life water quality criteria have been established primarily
for fish. Since fish are just one inhabitant of any body of water, there
is information needed to provide more comprehensive criteria for
water in relation to other aquatic life.
The large mass of analytical data on water quality of streams and
well water provides an opportunity for detailed analyses using computer
techniques. Data for various water basins can now be analyzed for trends
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191
and changes related to irrigation and agricultural practices. In some
cases there is a large time lag in the effect of return flow on the quality
of water being pumped from a groundwater basin.
Recommendations
The long-range result of mixing low quality return flow water
with high quality water needs studying relative to the complete chain of
water users. The quality cut-off point, at which the mixing of water
provides no net advantage, needs to be established for different condi-
tions. The advantages of recirculating reclaimed water in contrast to
increasing withdrawals should be studied, using some specific cases.
A systems approach to available water basin data could help
develop productive management techniques and philosophy.
Saline water has a significant but inadequately defined potential
as a source of recreation. Investigations are needed to identify the
range of uses and related considerations.
Use of different qualities of irrigation water should be studied
under farm situations in relation to various soil and cropping conditions,
and with special attention to new crops and varieties.
Effects of variations in water quality on plant nutrition have not
been defined. Such studies can be expected to permit economic retu.rns
from water of quality now considered unacceptable.
Investigations of the technology of water reclamation should be
continued, particularly using membrane processes.
The potential market for low quality water should be studied, with
costs and other limitations carefully evaluated to determine combinations
that can maximize economic returns.
Effects of salt and other chemicals on aquatic forms and biological
systems should be defined and incorporated into relevant standards.
Organisms and species may provide practical indication to suit-
able use of water of reduced quality. For instance, the presence of
certain fish indicates acceptability for livestock. Additional possible
indicator organisms should be identified for other purposes, such as
for the detection of shock loads of many pollutants.
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Treatment and Management of Return Flow Waters
The pollutants in irrigation return flows that currently appear
most objectionable, in terms of adversely affecting subsequent use,
are nutrients, salinity and possibly pesticides. When established irri-
gation practices cannot be significantly modified to preclude eventual
buildup of these constituents, treatment of irrigation return flows may
be necessary to produce an acceptable quality level. If treatment is
impracticable, the return flow may have to be physically excluded from
sectors of the water resources when they would be objectionable. The
hypothesis that users of irrigation water cannot afford to treat return
flows needs re-examination in relation to total social and economic
costs. If agriculture is to assume a posture comparable to that of
municipalities and industry, technical and financial assistance undoubtedly
will be required, to find practical and equitable solutions to the many prob-
lems and costs involved.
Re commendations^
Studies should be initiated on the treatment requirements of irri-
gation return flow in terms of total quantity-quality systems management.
Examples of the options that should be investigated include:
1. Collection and treatment to a specified level of
nitrates, phosphates, and/or total dissolved solids,
with eventual return to general water resources.
2. Dilution by streamflow regulation.
3. Management by diversion of return flows to selective
uses where reduced quality is acceptable (e.g., indus-
trial cooling •water) or to disposal sinks (e.g. , oceans,
estuary, etc. )
4. Permutations of such possibilities.
Quality control decision-making must be examined in terms of a
modern economic and legal framework.
Since formal identification of water pollution from irrigation return
flows is a relatively recent phenomenon, substantial inputs must be made
soon in the areas of manpower training, applied research of treatment
technology, systems management planning, and federal and state legis-
lation .
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Groundwater
Our understanding of our groundwater resources is minimal.
Most of what we do know simply emphasizes the need for research. As
groundwater is pumped for irrigation, a deep percolating return flow
changes the chemical composition of the groundwater. Deeply percolat-
ing water mixes with the groundwater resources and may be stored for
long periods and eventually transported appreciable distances in ground-
water aquifers.
Recommendations
Groundwater quality should be studied to help clarify changes in
the composition of return flow. Procedure and equipment should be
developed to permit the reliable sampling of groundwater and the sys-
tematic groundwater monitoring that should precede evaluation of ground-
water quality in relation to possible use. Detailed study at selected
locations should facilitate a comprehensive groundwater monitoring
system to assess the long-term effects of irrigation on the quality of
groundwater in the major storage basins.
Methodologies must be developed that will make possible adequate
study of the composition of groundwater, its movement, patterns, rates
and processes of mixing, and the gradual changes attributable to deeply
percolating irrigation water.
The use of groundwater storage basins in managing irrigation
return flows needs further study. In some instances unlined irrigation
canals add appreciable quantities of relatively high quality water to the
groundwater supply. The effects of conservation programs involving
lining of canals that may cause changes in groundwater quality and
quantity should be studied before canal lining and related programs are
initiated.
The commonly observed quality-oriented stratification of ground-
water within basins should be evaluated and mapped where practicable.
Also, the rate of mixing of groundwater needs to be evaluated in rela-
tion to such factors as permeability of the soil substrata, rates and
points of water additions and withdrawals, and other related factors.
The varied effects from moderate amounts of salt in irrigation
water, including increased infiltration into slowly permeable soil, needs
additional attention, particularly as related to irrigation practices and
groundwater recharge.
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Engineering techniques need to be developed to encourage more
effective utilization of ground-water of varying qualities, for example,
tapping better quality strata, while bypassing the less desirable.
Public Health
The public health aspects of return flow water will probably require
continuous updating as new analytical techniques are developed for viral
and other organisms, and as new chemicals are used in agricultural pro-
duction. Some data indicate that nematodes and other plant pathogens
may be carried by some return flows. A highly probable source of such
contamination is runoff water from the soil surface, but confirmation is
lacking. Salt and organics in irrigation water may influence the move-
ment and survival of micro-organisms and the movement and decompo-
sition of pesticides.
Radioactive pollution of water is a persistent and burgeoning prob-
lem. f There is increasing danger of contaminated water being used for
domestic and livestock consumption and for irrigation. Radio-nucleotides
are generally strongly adsorbed by soil, and the water is thereby improved,
but the effects on the soil and on the plants it supports have not been deter-
mined.
Recommendations
Factors affecting the rate of movement of viruses, bacteria,
other micro-organisms and pesticides through soil, and their appear-
ance and persistence in surface runoff water and groundwater should be
determined. Conditions under which return flow water is likely to
create health hazards should be defined more fully. The possibility of
using selected organisms as indicators of water quality merits attention
relative to public health problems.
Ways in which chemicals such as insecticides, herbicides and
soil fumigants may become ingredients of return flow water and create
potential health hazards should be determined and publicized.
Effects of radioactive pollutants on soil and the possibility of their
uptake by plants and resultant consequences deserve attention relative to
public health as well as to the agricultural productivity of the land.
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Legal and Economic'Considerations
Legal problems associated with deteriorating water quality have
not been adequately investigated. Growing public concern over deteri-
oration in the quality of many nationally important waters is leading to
expanded legal consideration and action. The lack of appropriate legal
structures relative to water quality may unnecessarily interfer with
future water development projects and in some instances may hamper
water quality control. To some extent the lack of legal frameworks for
water quality control may be accentuated by the dearth of economic re-
search to establish the cost of water quality deterioration. There is
need for broad economic research related to water quality, to assess
costs and benefits. Questions of equitable distribution of benefits to
geographical and social sectors are likely to provide difficult moments
unless legal guidelines are established.
Unique and extremely difficult economic problems related to irri-
gation return flows involve external economies and diseconomies. These
problems frequently are referenced in terms of incidence of costs and
benefits. Areas or firms or groups of firms that are interdependent
in the physical use of resources, nevertheless, make their decisions in-
dependently. Thus, the cost and return functions of the water resources
are distorted. In water quality, for example, the cost of deterioration
in use instigated by one user may be borne by another user. Since the
market system does not resolve these problems, institutional arrange-
ments must be devised. Appraisal of economic impacts of various alter-
natives is basic to formulation of these programs.
There is need for more information concerning cost distribution
and methods of financing systems required to serve users with the qual-
ity of water needed. In some instances it may be possible to exchange
water between users and thereby achieve gains through matching water
quality to users' quality requirements. New water agencies and laws
may be needed to effect such changes.
Re commendations
Studies should be made to provide reference data that will enable
greater precision in anticipating the physical, biological, social and
economic consequences of alternative laws, public policies, and other
institutional arrangements related to the use of water of different qual-
ity and the imposition of water quality standards, especially as related
to irrigation return flow.
More intensive study should be made on the inseparable nature of
quality-quantity management in relation to institutional, economic and
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legal restrictions, to assure that pollution laws do not abrogate exist-
ing water rights and compacts.
Inconsistencies in state and federal water laws and agency policies
(as related to water depletion and pollution by irrigation and return flow)
should be catalogued and plans developed for bringing them into general
agreement. Agreement should be sought also between laws and policies
and hydrologic principles.
The effects of changes in water quality on agricultural income, on
land values and on costs of alternative ways of disposing of low quality
waters should be investigated. Intensive research is needed on the
economic, social and legal aspects of the effects ,of pollution, in regard
to those who hold water rights.
A thorough economic model that relates water quality to uses and
values would be a major step in assessing the economic costs or benefits
of irrigation insofar as changes in water quality are concerned. Empiri-
cal testing of economic models, methodologies and criteria from the
standpoint of farm, area, regional, and national impacts of water quality
deterioration is essential. Studies of institutions and legal requirements
for effecting such shifts in water to match users requirements also should
receive attention.
Research should be done on assessments, financial arrangements,
and sources for alleviating external diseconomies arising from the
deterioration of water quality because of irrigation return flows and other
uses of water. The costs of alternative procedures for disposing of
and/or reclaiming saline return flows should be investigated. The eco-
nomic and legal implications of biological contamination of waters by
disease organisms, plant pathogens or other noxious pollutants also need
attention.
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GLOSSARY OF TERMS
Agricultural Consumptive Use: Use of water which is changed
from the liquid to the gaseous state by evaporation or transpiration
and is thereby lost from the soil-plant ecosystem. See also Evapo-
trans pi ration.
Applied Water Requirement: The quantity of water required to be
delivered at a farmer's headgate in a given period of time to meet con-
sumptive use and irrigation application loss requirements. It does not
include direct precipitation.
Benefit-Cost Ratio: The arithmetic proportion of estimated aver-
age annual economic benefits to average annual cost, insofar as the
factors can be expressed in monetary terms. It is a measure of the
degree of tangible economic justification of a project.
Benefits: Increase or gains, net of associated or induced costs,
in the value of goods and services which result from conditions with the
project, as compared with conditions without the project. Benefits in-
clude tangibles and intangibles and may be classed as primary or
secondary.
Bypass Water: Water diverted for irrigation, but returned to the
river or source of supply without being applied to the agricultural land.
Bypassing: Quality control of public water supplies by conveying
irrigation return flows in a separate channel thus bypassing the natural
channel.
Concentration: The quantity of dissolved material in a unit vol-
ume or weight of water. In this report concentration is expressed in
milligrams per liter, parts per million, equivalents per million,
specific electrical conductance in micromhos per cm, and tons per
acre foot.
Deep Percolation Losses: That portion of irrigation water applied
to the land that percolates below the crop root zone and is not subject
to consumptive use by the agricultural crops.
Degradable: Capable of being decomposed, deteriorated, or
decayed into simpler forms with characteristics different from the
original. Also referred to as biodegradable.
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Degradation of Water Quality: Decrease in water quality due to
increased concentration of any substance classified as a pollutant.
Dilution: The reduction of pollutant concentration of a given
water by the addition of water having a lesser concentration of pollu-
tant.
Drainage Water: Surface and subsurface water coming from irri-
gated areas which may be commingled with precipitation, surface run-
off, and groundwater flow from non-irrigated lands.
Economic Demand Schedule: The price schedule of quantities of
goods, services, or resources to be purchased.
Economic Efficiency: The situation in which productive resources
are so allocated among users that any reshuffling from the pattern does
not improve any individual's position but leaves all individuals as well
served as before.
Evaporation Disposal: A method of treating undesirable return
flows by capture and storage and allowing the stored water to naturally
evaporate.
Evapotranspiration: The consumptive use of water from the soil.
Water lost as vapor from a given area of soil through the combined
processes of evaporation from the soil surface and transpiration from
plants.
Financial Feasibility: A demonstration that beneficiaries are
ready, willing, and able to pay reimbursable costs for products and
services within the prescribed repayment period; that sufficient capital
is authorized and available to finance construction to completion, and
that estimated revenue to be derived during the prescribed repayment
period is sufficient to cover reimbursable project costs.
Intangible Benefits: Those benefits which, although recognized as
having real value in satisfying human needs or desires, are not fully
measurable in monetary terms, or are incapable of such expression in
formal analysis.
Intangible Damages: Those damages that cannot be evaulated in
monetary terms, such as loss of life, suffering, etc.
Irrigation: As used in this report, the application of water to
land to supply moisture required for the growing of crops. The appli-
cation of water to land by man-made devices, structures or controls.
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Irrigation Return Flow: Any water diverted for irrigation pur-
poses that finds its way back into a source of supply (stream or ground-
water basin). This includes bypass water, deep percolation losses,
tail water runoff and seepage.
Irrigation Water: Water diverted from a surface or groundwater
source to irrigate land.
Leaching Requirement: The fraction of water entering the soil
that must pass through the root zone to prevent salt accumulation from
exceeding a prescribed level, expressed as a percentage.
Maximization of Net Benefits: Extending the scope of development
to the point where the benefits added by the last increment of scale (i. e. ,
an increment of size of a unit, an individual purpose in a multiple pur-
pose plan, or a unit in a comprehensive plan) are equal to the cost of
adding that increment of scale.
Net Water Requirements: Applied water requirement less the
amount of the applied water that can be salvaged and re-used within
the area.
Nutrients: Compounds of nitrogen, phosphorus, and other elements
essential for plant growth. (These may have an adverse effect on water
quality. )
Pesticides: Chemical compounds used for the control of undesir-
able plants, animals, or insects. The term includes insecticides, -weed
killers, rodent poisons, nematode poisons, fungicides, and growth reg-
ulators.
Pollutants: Substances that may become dissolved, suspended,
absorbed, or otherwise contained in water, that impair its usefulness.
Pollution: The presence of any substance (organic, inorganic,
biological, thermal, or radiological) in water at intensity levels which
tend to impair, degrade, or adversely affect its quality or usefulness
for a specific purpose.
Primary Benefits: The value of goods and services directly result-
ing from the project, less associated costs incurred in realization of the
benefits and any induced costs not included in project costs. Types of
primary benefits may include domestic, municipal, and industrial water
supply, irrigation, flood prevention, land stabilization, drainage,
recreation, and fish and wildlife.
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200
Project Economic Costs: The value of all goods and services
(land, labor, and materials) used in constructing, operating, and main-
taining a project or program; interest during construction, and all other
identifiable expenses, losses, liabilities, and induced adverse effects
connected therewith, whether in goods or services, whether tangible or
intangible, and whether or not compensation is involved. Project
economic costs are the sum of installation costs; operation, maintenance,
and replacement costs, and induced costs. See also Installation Costs;
Operation, Maintenance, and Replacement Costs; and Induced Costs.
Quality: The degree of excellence or conformance to standards
for specific use.
Salinity: Salt content concentration of dissolved mineral salts in
water or soil.
Salinization: The process of accumulation of soluble salts in soil.
Salt Balance: The quantity of salt entering an area by way of the
irrigation •water as compared with the quantity of salts removed from
the area by return water.
Salts: Dissolved mineral matter and/or soluble inorganic salts.
Secondary Benefits: The increase in the value of goods and
services which indirectly result under conditions expected with the
project as compared to those without the project.
Seepage: That water which is lost from the conveyance channels
of rivers or other water supply systems.
Sewage: The water-carried wastes originating from households
(domestic sewage) and manufacturing establishments (industrial wastes)
that are collected and transported in sewerage systems to treatment
facilities. It contains organic materials that have high oxygen demands
for degradation and decomposition.
Sprinkler Irrigation: A method simulating rainfall by using various
spray nozzles to discharge water into the air allowing it to fall to the
earth and infiltrate into the soil. Several designs are employed: solid
set systems; portable systems; and hand held or positioned nozzles.
Sub-surf ace Irrigation: A method using the soil profile to trans-
mit the water from the source of supply to its point of storage in the
plant root zone. Particular soil profile conditions are required.
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Surface Irrigation: A method by which the soil surface is used to
convey the water to the point of infiltration into the soil. The following
surface application methods are used: flooding from field ditches;
border irrigation; checks; basins; furrows; and corrugations.
Tail Water Runoff: Irrigation water that runs off the surface of
irrigated fields. Sometimes referred to as waste water or surface
return flow.
Tangible Benefits: Those benefits, either primary or secondary,
that can be expressed in monetary terms.
Tangible Damages: Those damages that can be evaluated in
monetary terms.
Total Return Flow: All water that returns to a source of supply
after having been diverted for any purpose.
Used Water: Any water that has been used by man for any purpose,
including irrigation, municipal, industrial, power, recreation, fish,
and wildlife.
Water Quality: The sum total of all those properties, character-
istics, and attributes which determine the suitability of water for any
desired beneficial use.
Water Renovation: Restoration or improvement of quality by
reducing the amount of pollutants present. To restore to some former
state of purity.
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REFERENCES
1. Houk, Ivan E. , "Irrigation Engineering, '' Agr. and Hydrological
Phases, Vol. I, John Wiley & Sons, Inc., N. Y. 1951.
2. United States Water Resources Council, "The Nation's Water
Resources, " Wash. D. C. 1968.
3. Economic Research Service, "Major Uses of Land and Water in
the United States," Agr. Economic Report No. 13, Economic
Research Service, USDA. July 1962.
4. National Technical Advisory Committee, FWPCA, "Water Quality
Criteria, " US Gov. Printing Office, Wash. B.C. 1968.
5. Newell, Frederick Haynes, "Irrigation in the United States, " (3rd
Ed. Rev.), Thomas Y. Crowell & Co., N. Y. 1902 and 1906.
6. Mead, Elwood, "Irrigation in Utah, " US Gov. Printing Office, USDA,
Bull. 124. 1901 and 1904.
7. Wilson, Herbert M. , "Irrigation Engineering, " John Wiley & Sons,
N. Y. 1910.
8. American Association for the Advancement of Science, "Agriculture
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1967.
9. Pillsbury, Arthur F. , and Harry F. Blaney, "Salinity Problems
and Management in River Systems, " ASCE Jour, of the Irrigation
and Drainage Division, 92(IR1 ):77-90. 1966.
10. Hutchins, Wells A., "Selected Problems in the Law of Water Rights
in the West," USDA Misc. Publ. No. 418, US Gov. Printing Office,
Wash. D. C. 1942.
11. Scofield, Carl S. , "Salt Balance in Irrigated Areas, " Agricultural
Research, Vol. 61:17-39. 1940.
12. Wilcox, L. V., and W. F. Resch, "Salt Balance and Leaching
Requirement in Irrigated Lands, " USDA Tech. Bull. No. 1290.
July 1963.
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13. Richards, L. A., ed. , "Diagnosis and Improvement of Saline and
Alkali Soils, " USDA Agr. Handbook No. 60. February 1954.
14. Reeve, Ronald C. , and Milton Fireman, "Salt Problems in Rela-
tion to Irrigation, " Irrigation of Agricultural Lands, Ch. 51,
Agronomy Series, No. 11, ASA, Madison, Wis. 1967.
15. Bouwer, Herman, "Salt Balance, Irrigation Efficiency, and Drain-
age Design, " J. Irrig. Drain. Div. ASCE, accepted for publication.
1969.
16. Magistad, O. D. , "Plant Growth Relations on Saline and Alkali Soils, "
The Botanical Review, 11:181-230. 1945.
17. Hayward, H. E. , and L. Bernstein, "Plant-Growth Relationships
on Salt-Affected Soils, " The Botanical Review, 24:584-635. 1958.
18. Christiansen, Jerald E. , Jerome J. Jurinak, Carlos J. Grassi,
"Observations and Recommendations with Regard to Drainage and
Salinity Problems in the Choele Choel Irrigation Project, Republic
of Argentina, " mimeo report by Project 213, Inter-American Center
for the Integral Development of Land and Water Resources, Utah
State University, Logan. 1968.
19. Christiansen, J. E. , and J. P. Thorne, "Salinity Problems and
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