WATER POLLUTION CONTROL RESEARCH SERIES • 13030—11/71
RESEARCH NEEDS FOR IRRIGATION
RETURN FLOW QUALITY CONTROL
>. ENVIRONMENTAL PROTECTION AGENCY
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WATER POLLUTION CONTROL RESEARCH SERIES
The Water Pollution Control Research Series describes the
results and progress in the control and abatement of pollution
in our Nation's waters. They provide a central source of
information on the research, development, and demonstration
activities in the water research program of the Environmental
Protection Agency, through inhouse research and grants and
contracts with Federal, State, and local agencies, research
institutions, and industrial organizations.
Inquiries pertaining to Water Pollution Control Research
Reports should be directed to the Chief, Publications Branch
(Water), Research Information Division, R&M, Environmental
Protection Agency, Washington, B.C. 20460.
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RESEARCH NEEDS FOR
IRRIGATION RETURN FLOW
QUALITY CONTROL
by
Gaylord V. Skogerboe
Associate Professor
Agricultural Engineering Department
Colorado State University
Fort Collins, Colorado 80521
and
James P. Law, Jr.
Project Officer
Treatment and Control Research Program
Environmental Protection Agency
Robert S. Kerr Water Research Center
Ada, Oklahoma 74820
for the
OFFICE OF RESEARCH AND MONITORING
ENVIRONMENTAL PROTECTION AGENCY
Project #13030
November 1971
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $1.00
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EPA-Reviev Notice
This report has been revieved by the Environmental Protection
Agency and approved for publication. Approval does not
signify that the contents necessarily reflect the views and
policies of the Environmental Protection Agency nor -does
mention of trade names or commercial products pnnst.-it.iite
endorsement or recommendation for use.
ii
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ABSTRACT
There are a number of potential solutions for controlling
the quantity and quality of irrigation return flow. Using
efficient practices in the delivery canals and pipelines/
as well as improving on-the-farm water management/ will
minimize the problems in the water removal system. In
most cases, the key to minimizing irrigation return flow
quality problems is to improve water management practices
on the croplands.
There are various institutional methods which can be used
to control irrigation return flow quality. These methods
include restricting irrigation development in areas of
potentially high salt pickup, regulations on the use of
fertilizers, or agricultural chemicals, tailwater controls
which would not allow surface runoff from a farm, increas-
ing water rate charges, changing the interpretation of
western water laws, use of irrigation scheduling to over-
come institutional constraints, consolidation of irrigation
companies in an irrigated valley into a single management
unit, and/or requiring that anyone degrading the quality of
water pay the cost of treating this water.
There are a multitude of research needs regarding irrigation
return flow quality, but only the specific research needs
required to undertake an effective control program' are des-
cribed. These research needs include irrigation practices,
soil-plant-salinity relationships, leaching requirements,
prediction of subsurface return flow, cultural practices,
irrigation scheduling, treatment of return flows, economic
evaluations, and institutional control methods.
111
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CONTENTS
Section Page
I Conclusions 1
II Recommendations 5
III Introduction 7
IV Major Areas for Irrigation Return Flow 13
Problems
V Major Water Quality Problems 29
VI Potential Solutions and Control Measures 53
VII Research Needs 77
VIII Implementing Control Programs 85
IX Acknowledgments 91
X References 95
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FIGURES
No. Page
1 Model of the irrigation return flow system. 9
2 Major hydrologic regions in the United States. 17
3 Navajo Indian Irrigation Project. 26
4 Coachella Valley, Salton Sea, Imperial Valley, 32
and Mexicali Valley.
5 San Joaguin Valley. 40
6 Irrigation development in Yakima Valley. 43
7 Presently irrigated and potentially irrigable 45
areas in the Upper Snake River Basin.
8 Lower Truckee and Carson Rivers. 49
9 Proposed salinity control projects in the 69
Colorado River Basin.
VI
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TABLES
No.
Page
1 U.S. Irrigated acreage by states for 1968 14
and 1969.
2 Irrigated acreage by major hydrologic regions 16
in the United States for 1959 and 1969.
3 Long-term projective estimates of agricultural 18
irrigation in the United States, from
1980 to 2020.
4 Status and extent of saline and sodic areas 19
in the seventeen western states and
Hawaii, 1960.
5 Estimated diversions, depletions, and return 21
flows by major water uses in the United
States for the years 1954 and 2000.
6 Estimated annual irrigation^ water requirements 22
for years 1957, 1980, and 2000.
7 Mean annual discharge and dissolved solids, 36
Rio Grande.
8 Estimated costs of salinity control projects. 70
9 Projected salinity in the Lower Colorado River 73
with and without proposed salinity control
projects.
VI1
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SECTION I
CONCLUSIONS
The practice of irrigation has detrimental effects on
environmental water quality, just as do many other of man's
activities. Usually, the quality of water draining from
irrigated areas is materially degraded in several ways as
compared with the water applied. However, irrigation can
also produce beneficial water quality effects through denit-
rification, phosphate reduction in subsurface return flows,
and biological improvements. Irrigation return flows are
of special concern because irrigated agriculture is the
largest consumer of our water resources.
At the present time, about 48 million acres of land are
irrigated in the United States, with all but 5 million acres
being located in the 17 western states. Crop production is
reduced on one-quarter of the irrigated lands due to saline
soils, while salinity is an immediate hazard to half of these
irrigated lands. Throughout the world, a third of the irri-
gated land is plagued by salt problems.
•The major water quality problem resulting from irrigated
agriculture is the salt transported to groundwater reservoirs
and rivers by irrigation return flow. Other problems include
the movement of sediments, variable amounts of fertilizers
and pesticides, phosphates (which may come from fertilizers),
and increased bacterial content in surface return flows.
Subsurface return flows frequently show considerable increase
in salts, including nitrates, but show a reduction in bac-
teria.
Presently, the major irrigation return flow quality problem
areas are the San Joaquin Valley, Colorado River Basin, and
Rio Grande Basin. Of these three areas, only the Colorado
River Basin has had a reconnaissance study undertaken to
determine the salinity sources and to define, in a general
manner, potential control measures. Studies on irrigation
return flow have been conducted in the San Joaquin Valley,
while very little attention has been given to irrigation
return flow in the Rio Grande Basin. In addition to these
major problem areas, there are numerous other locations
throughout the West with recognized irrigation return flow
problems, including the Yakima Valley in Washington; the
Carson and Humboldt rivers in Nevada; the Santa Ana River
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Basin in California; the Sevier River in Utah; the South
Platte River in Colorado; the Bear River in Utah and Idaho;
the Platte River in Nebraska; the Pecos River in New Mexico
and Texas; the Columbia River Basin in Idaho, Oregon, and
Washington; and the Arkansas River Basin in Colorado, Kansas,
Oklahoma, and Arkansas. Actually, potential water quality
problems exist wherever irrigation is practiced.
Practical means for alleviating and/or controlling water
quality degradation of surface and groundwater resources
resulting from irrigated agriculture must be developed.
Where control measures are not readily apparent, research is
needed to develop criteria for effective solutions. A
unified research and development program requires careful
planning, which includes defining specific research activi-
ties necessary for the successful implementation of control
programs.
There are a number of potential solutions for controlling the
quantity and quality of irrigation return flow. The irri-
gation system can be subdivided into the water delivery sub-
system, the farm, and the water removal sub-system. Using
efficient practices in the delivery canals and pipelines, as
well as improving on-the-farm water management, will mini-
mize the problems in the water removal system. In most
cases, the key to minimizing irrigation return flow quality
problems is to improve water management practices on the
croplands.
The water delivery system can be improved by lining canals
and laterals, using closed conduits for water transportation/
providing adequate control structures, and installing flow
measuring devices.
Improved practices that can be used on the farm include judi-
cious use and application, or placement, of fertilizers, use
of slow-release fertilizers, controlling water deliveries
across the farm, use of improved irrigation application
methods (e.g. subsurface application of trickle irrigation),
control of soil evaporation, use of a pumpback system to
allow recycling of surface return flows, erosion control
practices (e.g. contour farming), and irrigation scheduling
to insure that the proper amounts of water are applied at
the times required by the plants.
In the water removal sub-system, open drains and tile drain-
age can be used to collect return flows, which can then be
subjected to treatment on a large area or basin-wide basis,
if necessary.
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There are various institutional methods which can be used
to control irrigation return flow quality. These methods
include restricting irrigation development in areas of
potentially high salt pickup, regulations on the use of
fertilizers, or agricultural chemicals, tailwater controls
which would not allow surface runoff from a farm, increas-
ing water rate charges, changing the interpretation of
western water laws, use of irrigation scheduling to over-
come institutional constraints, consolidation of irrigation
companies in an irrigated valley into a single management
unit, and/or requiring that anyone degrading the quality of
water pay the cost of treating this water.
There are a multitude of research needs regarding irrigation
return flow quality, but only the specific research needs
required to undertake an effective control program are des-
cribed. These research needs include irrigation practices,
soil-plant-salinity relationships, leaching requirements,
prediction of subsurface return flow, cultural practices,
irrigation scheduling, treatment of return flows, economic
evaluations, and institutional control methods.
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SECTION II
RECOMMENDATIONS
A study of the Rio Grande Basin should be undertaken to
define the magnitude of the water quality problems within
the basin. Potential solutions, and their associated
costs, for controlling quality degradation should be eval-
uated.
The two major areas of research which would facilitate the
development of control programs for an area are: (a) sub-
surface return flow quality prediction techniques; and (b)
economic evaluation. Without this research, a control pro-
gram is severely hampered because the effects of imposing
changes upon the system, such as control measures, cannot
be adequately evaluated.
Research projects should be initiated to develop and
recommend quality control-measures for subsurface return
flow in the Colorado River Basin and Rio Grande Basin, while
additional studies are needed in the San Joaquin Valley.
These same three study areas used to develop prediction
techniques for subsurface return flows should be used for
research and demonstration projects regarding irrigation
practices, soil-plant-salinity relationships, cultural
practices, leaching requirements, irrigation scheduling, and
drainage water treatment.
An economic evaluation of costs and benefits from return
flow control programs should be undertaken for each of these
three major problem areas. The research and demonstration
activities should be coordinated into the control program
for each region. A strong interaction must exist between
the research teams and local and action agency personnel.
Research teams should consist of regional, state, and federal
personnel most capable of developing control programs.
A study should be undertaken to evaluate the feasibility of
changing the interpretation of western water laws to provide
incentives for efficient water management on irrigated
lands.
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The soil and water conservation measures proven over the
past few decades to have water quality benefits, e.g., soil
erosion control, canal and farm ditch lining, and improved
irrigation practices, should continue through educational
and action programs.
The institutional constraints to water management reform
in irrigated areas should be critically evaluated. Major
among these are water rights doctrine and management prac-
tices of mutual water districts, canal companies, etc.
The effects of negotiable rather than fixed water rights
should be investigated, in addition to the effect of includ-
ing quality as well as quantity to water rights.
Federal legislation should be enacted to provide economic
incentives to undertake irrigation return flow quality
control projects.
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SECTION III
INTRODUCTION
Irrigation is one of the most important agricultural prac-
tices developed by man, with irrigation being practiced in
some form since the earliest recorded history of agriculture.
The economic base for many ancient civilizations was pro-
vided by irrigation. Indians of the western hemisphere were
irrigating crops long before the discovery of the New World
(25). Much of the economy of the western United States
depends on irrigation, which has been the dominant factor
in the development of land and water resources in the arid
and semi-arid regions of the western states. Irrigation is
practiced on about 10 percent of the total cropped land in
the United States, but this land produces approximately
25 percent of the Nation's total crop value (20). Irrigation
farming not only increases productivity, but it also provides
flexibility which allows shifting from the relatively few
dryland crops to many other crops which may be in greater
demand. Irrigation contributes to strengthening other facets
of a region's economy in that it creates employment oppor-
tunities in the processing and marketing of agricultural
products.
The practice of irrigation has detrimental effects on
environmental water quality, just as do many other of man's
activities. It has long been recognized that the quality of
water draining from irrigated areas was materially degraded
from that of the irrigation water applied. Agriculturists
have viewed this -as a natural consequence of the many pro-
cesses involved, and little attention has been given to the
possibility that progress could be made toward controlling
or alleviating the quality degradation caused to our water
resources. Recent Federal Legislation and a greatly increased
national concern have reversed this attitude, and we have
been charged "to establish a national policy for the preven-
tion, control, and abatement of water pollution" (14). The
Water Quality Act of 1965 further provided for all states to
establish water quality standards for their interstate and
coastal waters. Crucial decisions were required regarding
the uses of water resources, quality criteria to support
these uses, and specific plans for achieving such levels of
quality. The purpose of this program is to enhance the
quality and value of polluted water and to protect the quality
of clean water. The water quality standards are, in effect,
the guides to an effective clean water program. Although the
major efforts to date appear to be in the treatment and control
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of municipal and industrial wastes, agriculture is by no
means exempted from the fight against water quality degrada-
tion. The water quality problems associated with irrigation
return flows are of special concern because irrigation agri-
culture is the largest consumer of our Nation's water resources.
It is also of major importance to the economy of a large
segment of the nation and is the supplier of a significant
part of the food and fiber produced annually.
Irrigation return flow constitutes a large portion of the
flow in many streams of the western United States.
Some degree of salt concentration due to irrigation has been
accepted as the price for irrigation development. However/
there are areas where quality degradation has been a serious
matter for some time. As pressures on water resources increase,
there is a mounting concern for proper control of such serious
water quality deterioration. The need for more precise infor-
mation as a basis for wise action has been brought sharply
into focus. There is a great dearth of information concerning
the exact role of irrigation return flows in surface and ground-
water quality problems.
Irrigation Return Flow System
The complexities of the irrigation return flow system and its
relationship to a river basin are portrayed schematically in
Figure 1. The model shows the primary sources of return flow
to be canal seepage, bypass water, deep percolation, ground-
water flow, and tailwater or surface return flow. Each of
these can be subjected to some degree of manipulation and/or
control through water management techniques. Bypass water is
chiefly a water resource or conservation problem, since few
impurities are added by simply flowing through the canal
system. It is required for the purpose of maintaining head
and adequate flow through the canal system and is usually
returned directly to the river. Canal seepage, on the other
hand, contributes to high water tables, aggravates subsurface
salinity, encourages phreatophyte growth, and generally
increases saline subsurface drainage from irrigated areas.
Canal seepage can be a significant fraction of the total
diversion in many project areas (30). Once water is applied
to irrigated cropland, tailwater and deep percolation are
the major contributors to irrigation return flow. These
sources are the conveyors of dissolved salts, plant nutrients,
sediments, pesticides, and other pollutants to the stream
drainage system.
The diversion-return flow cycle shown in Figure 1 is typical
of many western rivers. The flow at any point in the river
may be composed of natural inflow, irrigation return flow,
municipal and industrial effluents, and return flow of other
used water. The proportion of each depends on such factors
8
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Evaporation
from Canals
Precipitation
I I
Inflow to
Canals
Upstream
Surface Runoff From
Non-Irrigated Land
Ind. 8 Mun
Wastes
Natural
Inflow
Evapo transpiration
from Crops
Other
Evapotranspiration
from Irrigated Land
Applied to
Irrigated Land
Diverted
for
Irrigation
Groundwater
Contribution
River Flow
Irrigation
Return Flow
I
Downstream
Figure I. Model of the irrigation return flow system.
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as the number of diversions, the extent and diversity of
uses, the position on the stream, and the amount of natural
inflow to the stream. The model represents but one diver-
sion cycle which may be repeated many times over in a river
basin.
The major water quality problems resulting from irrigation
are due to the basic fact that plants are large consumers of
water resources. Growing plants extract water from the supply
and leave salts behind, resulting in a concentration of the
dissolved mineral salts which are present in all natural water
resources. In addition to having greater concentrations of
salts in the return flow resulting from evapotranspiration,
irrigation also adds to the salt load by leaching natural
salts arising from weathered minerals occurring in the soil
profile, or deposited below. Irrigation return flows pro-
vide the vehicle for conveying the concentrated salts and
other pollutants to a receiving stream or groundwater reser-
voir. It is necessary to examine the water quality problems
resulting from this process and to develop and implement
measures to control or alleviate the detrimental effects.
Purpose of Report
The responsibility for developing and coordinating the national
Irrigation Return Flow Research and Development program within
the Environmental Protection Agency is vested in the Robert
S. Kerr Water Research Center at Ada, Oklahoma. Briefly, the
major goal of the program is to find practical and economic-
ally feasible means to alleviate and/or control the water
quality degradation of surface and groundwater resources
resulting from irrigated agriculture. In establishing and
implementing such a broad control program, a number of decision-
making steps-are required. First of all, decisions are required
on effective control measures required by the program. Where
control measures are not readily apparent, the second step
requires specifying the research that is needed to identify,
verify, and/or justify certain control measures that would be
effective in accomplishing the program goals. Finally, inves-
tigations, demonstrations, and applied research will be
required to solve the social, legal, and institutional problems
inherent in effecting the necessary changes to bring about
quality control of irrigation return flows.
A unified research and development program requires careful
planning. There is a need to define in some detail the
research activities required by the program. This report is
an effort to meet this immediate need. Under the terms of
an existing grant agreement with the Department of Agricul-
tural Engineering at Colorado State University, basic
10
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background information for the report was gathered. Recog-
nized authorities in several of the western states were
visited and interviewed (See Section IX Acknowledgments).
The results of those interviews constitute the basis for the
majority of the material presented herein.
The objectives of the report are specified by the major
topics covered as follows:
a. Define the major geographic areas where irrigation
return flow problems exist.
b. Specify the major water quality problems arising from
irrigation return flows and how these differ by regions.
c. Propose potential solutions required to alleviate and/or
control water quality degradation by irrigation.
d. Define specific research activities most urgently
required to design and implement control measures or poten-
tial solutions to critical problems.
This report will form the basis for future program planning.
It will provide specific problem definitions needed to develop
an integrated program for achieving solutions needed to
establish guidelines for the control of water quality of irri-
gation return flows. In addition to the program planning
function, it will serve as a guide to interested research
groups.
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SECTION IV
MAJOR AREAS FOR IRRIGATION RETURN FLOW PROBLEMS
In the past 80 years, the total irrigated land in the
United States has increased from under four million acres
to over 48 million acres, or an increase of 1,200 percent.
During the last two decades, the value of supplemental
irrigation has been recognized in the humid eastern United
States, with the total irrigated acreage being five million
acres. There is reason to believe that the acreage
of irrigated lands will continue to increase. At the same
time, farming is becoming more and more intensive, thereby
resulting in greater food production on each acre of irri-
gated cropland, with increasing use of fertilizers.
Every state has some croplands which are irrigated. A tab-
ulation of irrigated acreages during 1968 and 1969 for each
state (29) is listed in Table 1, while the amount of irri-
gated land for 1959 and 1969 (22,28) is given in Table 2 by
river basins. There is a discrepancy between Tables 1 and
2 regarding the 1969 irrigated acreage, which amounts to
roughly 5 million acres, or 10 percent. The major irriga-
ted areas in the United States are located in the seventeen
western states. Both California and Texas contain more
than eight million acres of irrigated land, with Nebraska
having more than four million irrigated acres, and Colorado,
Idaho, and Montana each containing better than three million
irrigated acres. The major river basins are shown in Figure 2.
The Economic Research Service (22) has made projections of
irrigated acreage in the United States to the year 2020.
A breakdown of these projections by major river basins is
shown in Table 3. The increase in irrigated acreage in
the United States (mainland 48 states) from 1969 to 2000
is roughly 30 percent, with the projected increase for the
same time period in the western states being 25 percent.
Many of the irrigated lands, particularly in western arid
areas, contain large quantities of salt and are therefore
classed as saline soils. Some lands are high in exchange-
able sodium and,are referred to as being sodic. The
estimated acreage of salt-affected soils is listed in
Table 4 (30). Crop production is reduced on one-quarter of
the irrigated lands in the western United States due to
saline soils. Salinity is a hazard to half of the
13
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Table 1. U.S. irrigated acreage by states for 1968 and 1969
(29).
State
Alabama
Alaska
Arizona
Arkansas
California
Colorado
Connecticut
Delaware
Florida
Georgia
Hawaii
Idaho
Illinois
Indiana
Iowa
Kansas
Kentucky
Louisiana
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mississippi
Missouri
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New Mexico
New York
North Carolina
North Dakota
Ohio
Irrigated
Acreage
1968
32,000
464
1,131,000
1,350,000
8,600,000
3,280,000
13,000
14,700
1*440,876
182,000
126,000
3,660,000
32,000
34,400
93,000
1,416,814
.21,000
580,687
6,574
23,000
29,470
138,000
25,000
115,000
145,305
3,200,000
4,103,300
1,300,000
3,100
96,439
875,000
87,500
104,029
89,100
36,000
Irrigated
Acreage
1969
32,000
1,155
1,145,000
1,435,000
8,500,000
3,310,000
12,000
14,700
1,490,876
144,629
126,000
3,660,000
34,000
35,100
95,000
1,588,377
21,000
580,687
14,772
23,000
30,470
139,000
25,000
209,057
145,305
3,200,000
4,236,000
1,300,000
3,100
106,300
1,000,000
89,250
104,639
89,100
37,000
Percent
Increase or
Decrease
0
+149
+ 1'
-1- 6
- 1
+ 1
- 8
0
+ 3
- 26
0
0
+ 6
+ 2
+ 2
+ 5
0
0
+125
0
+ 3
+ 1
0
+ 82
0
0
+ 3
0
0
+ 10
+ 4
+ 2
0
0
+ 3
14
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Table 1. (Continued)
State
Oklahoma
Oregon
Pennsylvania
Rhode Island
South Carolina
South Dakota
Tennessee
Texas
Utah
Vermont
Virginia
Washington
West Virginia
Wisconsin
Wyoming
U.S. To'tal
17 Western States
Other States
Irrigated
Acreage
1968
610,000
1,760,000
37,000
3,325
35,618
414,000
17,500
8,300,000
1,348,624
2,200
65,000
1,440,000
3,060
110,000
1,608,500
48,311,148
43,307,901
5,003,247
Irrigated
Acreage
1969
619,278
1,800,000
37,000
3,325
37,772
414,000
17,250
8,200,000
1,3.48,624
2,200
50,000
1,460,000
3,313
110,000
1,642,500
48,551,216
43,341,316
5,209,900
Percent
Increase or
Decrease
+ 3
+ 2
0
0
+ 5h
0
- 1
- 1
0
0
- 30
+ 1
+ 8
0
+ 2
+ h
0
+ 4
15
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Table 2. Irrigated acreage by major hydrologic regions
in the United States for 1959 and 1969.
I959i/ 1969^
Acres Acres
1,000 1,000
North Atlantic 208 519
South Atlantic - Gulf 560 1,747
Great Lakes 82 143
Ohio Basin 30 99
Tennessee Basin 13 18
Upper Mississippi 55 121
Lower Mississippi 625 972
TOTAL-EASTERN REGIONS 1,573 3,619
Souris - Red - Rainy 9 20
Missouri Basin . 5,802 6,985
Arkansas - White - Red 2,806 5,357
Texas - Gulf 4,168 5,890
Rio Grande 1,638 2,020
Upper Colorado 1,361 1,700
Lower Colorado 1,219 1,430
Great Basin 1,426 2,240
Columbia - North Pacific 5,014 5,815
California 7,627 8,050
TOTAL-WESTERN REGIONS 31,070 39,507
MAINLAND UNITED STATES 32,643 43,126
Tabulated by river basins from the 1959 USDA Census
of Agriculture (28).
Taken from projections by George A.. Pavelis, Economic
Research Service, USDA (22).
16
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'"COLUMBJA
NORTH PACIFIC
GREA
LAKES
UPPER
MISSISSIPPI
MISSOURI
GREAT BASIN
ARKANSAS-WHITE-RED
LOWER ,;
COLORADO;'
RIO
GRANDE
TEXAS-GULF
Figure 2. Major hydrologic regions in the United States
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Table 3. Long-term projective estimates of agricultural
irrigation in the United States, from 1980 to
2020 (22). (All acreage data are in thousands
of acres.)
1980 2000 2020
North Atlantic 730 990 1,120
South Atlantic - Gulf 2,480 3,520 4,150
Great Lakes 230 350 470
Ohio Basin 150 250 340
Tennessee Basin 30 50 70
Upper Mississippi 210 310 410
Lower Mississippi . 1,400 2,070 2,570
TOTAL-EASTERN REGIONS 5,230 7,540 9,130
Souris - Red - Rainy 90 230 250
Missouri Basin 8,050 8,950 9,600
Arkansas - White - Red 5,600 6,400 6,690
Texas' Gulf 6,510 7,350 7,770
Rio Grande 2,050 2,180 2,200
Upper Colorado 1,900 2,150 2,250
Lower Colorado 1,820 2,190 2,400
Great Basin 2,340 2,510 2,570
Columbia - North Pacific 7,350 7,810 8,490
California 9,050 9,600 11,540
TOTAL-WESTERN REGIONS 44,760 49,370 53,760
MAINLAND UNITED STATES 49,990 56,910 62,890
18
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Table 4. Status and extent of saline and sodic areas in the seventeen western states
and Hawaii, I960.1
State
Arizona
California
Colorado
Hawaii
Idaho
Kansas
Montana
Nebraska
Nevada
New Mexico
North Dakota
Oklahoma
Oregon
South Dakota
Texas
Utah
Washington
Wyoming
TOTAL
1 Unpublished
Area reported
Statewide
Statewide
Statewide
7 areas
All but 3 counties
Statewide
4 areas
Statewide
Statewide
Statewide
6 areas
Statewide
Statewide
Statewide
4 areas
7 areas
23 counties and the
Columbia Basin
Statewide
data from the U.S. Sa
Total
acreage2
1,565,000
11,500,000
2,811,532
117,418
1,880,063
421,545
1,242,728s
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
2,221,484
1,261,132
36,451,893
linity Labora
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
tory cited in
%
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
103,361
1,196,266
275,854
512,782
266,254
279,703
10,325,305
"Characteristics and
%
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
Pollution
Problems of
2 Irrigable
3 Arable
Irrigation Return Flow," Utah State University Foundation (1969).
-------
irrigated acreage in the West. California, which has a
greater acreage of irrigated land than any other state/
also contains the largest acreage of salt-affected soils.
The states of South Dakota, Nevada, Hawaii, Utah, and
Colorado have more than one-third of the irrigated lands
being affected by highly saline soils.
The impaired crop production previously mentioned is not lim-
ited to the western United States, but is a major problem in
many areas of the world. The portions of the world facing
the greatest population pressures are the same areas which
have the least amount of additional land available for
agriculture. In such areas, increased food production
must come from more intensive farming with consequent
increased yields. Although there is a great need to
increase the productivity of such lands, agricultural pro-
duction is being damaged due to rising groundwater tables
and increased salinity in the soils and groundwater supp-
lies. Bower (4) has estimated that more than a third of
the world's irrigated land is plagued by salt problems.
Projected water demands in the United States for the year
2000 are shown in Table 5 for major types of water uses
(9). The total diversion, depletion, and return flows
for irrigation, municipal, manufacturing, mining, and
power plant cooling are shown for the years
1954 and 2000. The projected increase in irrigation
diversions is very small, with such diversions increasing
5 percent, while the increase in irrigated acreage from
1954 to 2000 is projected to be doubled. Thus, the pro-
jections for water withdrawals reflect an expected major
increase in irrigation efficiency.
The National Academy of Sciences (9) has made projec-
tions for irrigation water requirements based on current
water use efficiencies and estimated future efficiencies
as shown in Table 6. For the western region, improved
water use efficiency would result in a net decrease of
surface water withdrawals.
20
-------
Table 5. Estimated diversions, depletions, and return flows by major water
uses in the United States for the years 1954 and 2000 (9).
(All units in billions of gallons daily.)
Year 1954
Use
Irrigation
Municipal
Manufacturing
Mining
Steam-Electric
Power Cooling
Totals
Notes :
Gross
Withdrawal
176.1
16.7
31.9
1.5
74.1
300.3
Withdrawals and consumptive
Water Resources, 86th Congr<
Consumptive
Use
103.9
2.1
2.8
0.3
0.4
109.5
Return
72.2
14.6
29.1
1.2
73.7
190.8
uses from Report of
2SS, January
30, 1961
Year 2000
Gross Consumptive
Withdrawal Use
184.5
42.2
229.2
3.4
429.4
888.7
the Select
•
126.3
5.5
20.8
0.7
2.9
156.2
Return
58.2
36.7
208.4
2.7
426.5
732.5
Committee on National
Total estimated streamflow = 1,100 billion gallons daily.
-------
to
Table 6. Estimated annual irrigation water requirements for years 1957, 1980, and 2000 (9).
(All units in thousands of acre-feet.)
Water Resource Region
Total groundwater and surface-water
requirements
At estimated
future efficiency
1957b 1980 2000 1980 2000
At current efficiency3
Surface-water re-
quirement at estimated
future efficiency
1957
1980
2000
Additional surface-
water requirement
at estimated future
efficiency
1980 2000
Eastern:
New England
Delaware-Hudson
Chesapeake Bay
Southeast
Eastern Great Lakes
Western Great Lakes
Ohio
Cumberland
Tennessee
Upper Mississippi
Lower Mississippi
Lower Missouri
Lower Arkansas, White, Red
Subtotal
Western:
Upper Missouri
Upper Arkansas, White, Red
Western Gulf
Upper .Rio Grande-Pecos
Colorado
Great Basin
Pacific Northwest
Central Pacific
South Pacific
Subtotal
United States Totals
1
1
1
b
17
4
11
6
20
9
16
35
5
127
133
54
220
84
,743
44
67
84
8
44
100
,592
21
,560
,621
,717
,748
,840
,576
,262
,444
,182
,924
,044
,737
,358
96
312
156
3,022
66
142
186
11
60
243
2,295
45
2,177
8,811
20,747
4,876
11,789
7,079
20,335
9,481
16,837
35,031
4,486
130,661
139,472
297
583
1,675
12,196
713
1,330
2,178
113
354'
6,081
4,409
1,650
3,847
35,426
32,040
6,488
15,689
8,053
20,708,
9,742
21,053
35,623
4,635
154,031
189,457
80
292
132
2,374
54
120
158
9.
57
212
2,020
39
1,880
7,427
16,346
4,035
9,226
5,522
16,071
7,449
13,680
30,223
3,671
106,223
113,650
247
437
1,256
8,711
546
997
1,633
85
275
4,561
3,351
1,350
3,148
26,597
22,331
4,922
10,914
5,315
14,696
6,727
15,132
27,241
3,371
110,649
137,246
49
110
77
906
32
58
59
7
40
56
605
18
437
2,454
15,237
1,329
5,328
2,959
14,386
8,216
14,887
17,962
2,522
82,826
85,280
73
146
121
1,234
39
103
111
8
52
119
768
34
526
3,334
14,058
1,130
4,613
2,761
12,214
6,481
12,586
16,623
2,019
72,485
75,819
225
219
1,156
4,530
399
857
1,143
78
253
2,554
1,273
1,161
881
14 ,729
19,205
1,378
6,003
2,923
11,904
5,852
13,921
16,345
2,023
79 ,554
94,283
24
36
44
328
7
45
52
1
12
63
163
16
89
880
- 1,179°
199
715
198
- 2,172
- 1,735
- 2,301
- 1,339
503
-10 ,341C
- 9,461C
176
109
1,079
3,624
367
799
1,084
71
213
2,488
668
1,143
444
12, 275
3,968
49
675
36°
-2,482
-2,364
- 966
-1,617
- 499
-3,272°
. 9,003
Assuming no increase in efficiency of application and' transmission of irrigation water.
Based on adequate irrigation of all land under irrigation.
CNegative values indicate a net decrease in water requirements resulting from estimated increased
efficiency in use and transmission of irrigation water.
-------
Whenever water is diverted from a river for irrigation use,
the quality of the return flow is degraded. The return
flow mixes with the natural flows in the river. This
mixture is then available to downstream users to be diverted
to satisfy their water demands. This process of diversion
and return flow may be repeated many times along the course
of a river. In the case of the original diversion, if the
increase in pollutants contained in the return flow is
small in comparison to the total flow in the river, the
water quality would probably not be degraded-to such an
extent that it would be unfit for use by the next downstream
user.
If the quantity of pollutants in the return flow is large
in relation to the river flow, then it is very likely that
the water is not suitable for the next user unless the water
is treated to remove objectionable constituents. Since
water is diverted many times from the major rivers, the
river flows show a continual degradation of quality in the
downstream direction. As the water resources become more
fully developed and utilized, without controls, the quality
in the lower reaches of the river will likely be degraded
to such a point that the remaining flows will be unsuitable
for many uses, or previous uses of the waters arriving at
the lower river basin no longer will be possible.
Two examples of major river basins having high utilization
of the water resources and experiencing deleterious water
quality effects are the Colorado River Basin and the Rio
Grande Basin. The water users in the Lower Colorado River
Basin, especially Mexico, the Imperial, and Coachella
valleys, experience difficulties at the present time due
to high salt concentrations in the river. Salt concentra-
tions in the Lower Colorado River at the turn of the century
(year 2000) due to anticipated water resource development
projects are projected to increase. Projects are presently
nearing completion for exporting additional quantities of
high quality water from Colorado River watersheds to satisfy
water demands in the more populous regions of Utah, Colo-
rado, and New Mexico. The authorized Central Arizona
Project will divert large quantities of flow from the Colo-
rado River to Salt River Valley, which is within the basin,
but the return flows to the Colorado River will be almost
nil. However, the irrigation return flows will have long-
term effects on the salt balance in the Salt River Valley.
In addition, large quantities of water will be diverted,
with no return flows, for use by present and future power
plants in the four corners region (Utah, Colorado, New
Mexico, and Arizona). A salinity control program, which
would be a combination of controlling mineralized springs
and irrigation return flows, would negate a large portion
23
-------
of the damage which will result from recently constructed
and anticipated water resource development projects, which
will export good quality water to adjacent river basins,
thereby leaving less water within the Colorado River Basin
for diluting irrigation return flows.
The Rio Grande Basin is another example of an area already
experiencing serious water quality problems, with the out-
look for even more serious problems. Rapid population
growths in Albuquerque, El Paso, and Juarez, alone, foretell
of immediate difficulties. Whereas studies have been made
in the Colorado River Basin which predict future water
quality problems due to basin development, such comprehensive
studies have not been undertaken in the Rio Grande River
Basin. Future water quality problems in this basin could
easily result in international problems somewhat similar to
those recently experienced in the Lower Colorado River. By
necessity, a control program for irrigation return flow
would be a significant part of any comprehensive water
development plan.
Another major irrigated agricultural area which is pres-
ently experiencing water quality problems due to irrigation
return flow is the.San Joaquin Valley. Water deliveries
from portions of the recently constructed California State
Water Project have begun. New lands are being placed under
irrigation and natural salts (including nitrates and boron)
in the soil root zone must be leached, with subsequent
higher water tables in the presently irrigated lower lands.
A drain is being constructed in order to carry the return
flows to the ocean by way of San Francisco Bay. Because
of already serious quality problems in the bay, this
drainage water must be treated for nitrate removal before
being released into the bay. One of the major difficulties
is predicting the quantity of drainage water, as well as
its quality. Thus, the magnitude of the potential problems
can only be estimated at the present time.
The Yakima Valley in central Washington is an area which
experiences considerable local difficulty due to irrigation
return flow, but once the return flows reach the Columbia
River, the quality degradation is minor because the Columbia
River flow is many times larger than the Yakima River.
Even so, there is a real need for an irrigation return flow
control program because of competition from other uses
(fishing, recreation, municipal, and industrial) within the
Yakima River Basin, as well as to provide economic equity
among the agricultural water users.
24
-------
In addition to the problem areas cited above, there are
numerous examples of irrigated areas in the West which
experience water quality problems, many of them serious,
due to irrigation return flow. Some examples are: the
Pecos River in New Mexico and Texas; the Arkansas River
Basin in Colorado, Kansas, Oklahoma, and Arkansas; the
South Platte River in Colorado; the Platte River in
Nebraska; the Sevier River in Utah; the Bear River in Utah
and Idaho; the Humboldt River in Nevada; and the Santa
Ana Basin in California. With the passing of time, the
water quality problems in these areas will become more
serious because of increasing water demands.
Although salinity problems due to irrigation return flow
are not significant in much of the Pacific Northwest, water
quality problems resulting from pesticides, nitrogen, phos-
phorus, nematodes, and sediments are very important. Also,
there is considerable potential for increasing the irrigated
acreage in the Columbia River Basin because of abundant
water supplies. For example, Idaho could increase its
irrigated cropland from 3.66 million acres (1969) to 8
million acres. Such an increase in irrigated acreage could
be expected to have a dramatic effect upon the water quan-
tity and quality of the Snake River.
Present-day technology is not sufficient for predicting the
quality of irrigation return flow. Thus, there is a real
problem in making long-range projections on water quality
in a receiving stream due to irrigation projects. Conse-
quently, the problems resulting from the development of
new irrigation projects, particularly those involving
lands not previously irrigated, are usually confronted
after-the-fact.
The Navajo Indian Irrigation Project in northwestern New
Mexico (Figure 3), which is presently under construction,
will eventually irrigate 110,000 acres of land not prev-
iously irrigated. An initial block of 10,000 acres is
scheduled for irrigation in the spring of 1975. Of the
approximately 500,000 acre-feet of water to be diverted
annually, half (250,000 acre-feet per year) of the water
is expected to be return flow. There are estimates that
the quality of these return flows will double in salt con-
centration due to evapotranspiration, but there are no
estimates of salt pickup. Presently, the irrigation system
for the initial block is being re-designed to provide more
efficient water utilization. If this results in less water
being diverted for the 110,000 acres, then the total salt
load returning to the San Juan River will not be as great
as would have occurred under the original plan of develop-
ment due to reduced salt pickup. In any event, predicitons
25
-------
I
go 2 4 6 i
SCALE IN MILES
LOCATION MAP
Figure 3. Navajo Indian Irrigation Project.
-------
of salt load returning to the San Juan River are not
available. As a consequence, expected downstream damages
in the Lower Colorado River to Arizona (particularly when
the Central Arizona Project is constructed), California and
Mexico are unknown with only very crude estimates being
possible.
The Navajo Indian Irrigation Project is but one example
of our present-day problems in predicting the effect of
irrigation development upon the quality of downstream
receiving waters. As our water resources become more fully
utilized, the importance of irrigation return flow quality
will be of even greater significance in the overall water
management and development in a basin. If large-scale schemes
for transporting water to the Intermountain West from the
Columbia River Basin or Canada were to become a reality, what
would be the effect of irrigating new desert lands in Utah
and Nevada, or other adjacent areas? Questions similar to
this can be raised regarding the effect of any projected
changes to present water resource schemes. Intelligent
answers are needed if we are to recommend and initiate
control programs based on wise use of available technology.
It is the intent and purpose of this report to point out
those areas where present technology is lacking and indi-
cate future courses toward technological development.
27
-------
SECTION V
MAJOR WATER QUALITY PROBLEMS
Usually, the quality of water coming from the mountainous
watersheds in the West is excellent. At the base of the
mountain ranges, large quantities of water are diverted to
valley croplands. Much of the diverted water is lost to
the atmosphere by evapotranspiration (perhaps one-half to
two-thirds of the diverted water), with the remaining
water supply being irrigation return flow. This return
flow will either be surface runoff, shallow horizontal
subsurface flow, or will move vertically through the soil
profile until it reaches a perched water table or the
groundwater reservoir, where it will remain to be pumped
or be transported through the groundwater reservoir until
it reaches a river channel.
That portion of the water supply which has been diverted
for irrigation but lost by evapotranspiration (consumed)
is essentially salt-free. Therefore, the irrigation return
flow will contain most of the salts originally in the water
supply. The surface irrigation return flow will usually
contain only slightly higher salt concentrations than the
original water supply, but in some cases, the salinity may
be increased significantly. Thus, the water percolating
through the soil profile contains the majority of salt
left behind by the water returned to the atmosphere as
vapor through the phenomena of evaporation and trans-
piration. Consequently, the percolating soil water con-
tains a higher concentration of salts. This is referred
to as the "concentrating" effect.
As the water moves through the soil profile, it may pick
up additional salts by dissolution. In addition, some
salts may be precipitated in the soil, while there will
be an exchange between some salt ions in the water and
in the soil. The salts picked up by the water in addi-
tion to the salts which were in the water applied to the
land are termed salt "pickup." The total salt load is
the sum of the original mass of salt in the applied water
as the result of the concentrating effect plus the salt
pickup1.
Whether irrigation return flows come from surface runoff
or have returned to the system via the soil profile, the
29
-------
water can be expected to undergo a variety of quality
changes due to varying exposure conditions. Drainage from
surface sources consists mainly (there will be some precip-
itation runoff) of surface runoff from irrigated land.
Because of its limited contact and exposure to the soil
surface, the following changes in quality might be expected
between application and runoff: (a) dissolved solids con-
centration only slightly increased; (b) addition of variable
and fluctuating amounts of pesticides; (c) addition of,
variable amounts of fertilizer elements; (d) an increase in
pediments and other colloidal material; (e) crop residues
and other debris floated from the soil surface; and (f)
increased bacterial content.
Drainage water that has moved through the soil profile will
experience different changes in quality from surface runoff.
Because of its more intimate contact with the soil and the
dynamic soil-plant-water regime, the following changes in
quality are predictable: (a) considerable increase in
dissolved solids concentration; (b) the distribution of
various cations and anions may be quite different; (c)
variation in the total salt load depending on whether there
has been deposition or leaching; (d) little or no sediment
or colloidal material; (e) generally, increased nitrate
ccrtent unless the applied water is unusually high in nit-
rates; (f) little or no phosphorus content; (g) general
reduction of oxidizable organic substances; and (h) reduc-
tion of pathogenic organisms and coliform bacteria. Thus,
either type of return flow will affect the receiving water
in proportion to respective discharges and the relative
quality of the receiving water.
The quality of irrigation water and return flow is deter-
mined largely 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 contacted by the water.
Irrigation, municipal and industrial use and reuse of water
concentrates these salts and adds additional, kinds and
amounts of pollutants. Many insecticides, fungicides, bac-
tericides, herbicides, nematocides, as well as plant hormones,
detergents, salts of heavy metals, and many organic compounds,
render water less fit for irrigation and other beneficial
uses.
Colorado River Basin
The variety of water quality problems resulting from irriga-
tion return flow can be illustrated with a few examples. The
major water quality problem in the western United States is
30
-------
salinity, with the Colorado River Basin being one of the
more serious problem areas. In addition to the problems
caused by large quantities of good quality water being
transported outside of the Basin, there is a tremendous
problem due to salt pickup by the irrigation return flows
passing through the soil profile and over saline shale beds
before returning to the river. Also, there are a number of
mineralized springs which further aggravate the salinity
problem. The highest rates of salt pickup among the irri-
gated valleys within the basin occur in Grand Valley, Colo-
rado and Castle Valley, Utah where the rate is about 8 tons
of salt a year for each irrigated acre. Salt pickup rates
of roughly 6 tons per acre per year result from irrigation
in the Uncompahgre River Valley and Lower Gunnison River
Valley, with both valleys being located in Colorado. High
rates of salt pickup also occur at Big Sandy Creek Basin in
Wyoming, Ashley Valley in Utah, and the Duchesne River Basin
in Utah. Of the total salt load reaching Hoover Dam, the
Environmental Protection Agency (12) estimates that 37 per-
cent is the result of salt pickup from deep percolating
irrigation return flows.
The Colorado River Board of California (8) has made predic-
tions of future salinity at Parker Dam (diversion point for
the Metropolitan Water District of Southern California) and
Imperial Dam (diversion point for All-American Canal which
serves Imperial and Coachella Valleys) based upon antici-
pated upstream water development (Figure 4). By the year
2000, the projected salinity levels at Parker Dam and
Imperial Dam will be 1110 ppm and 1340 ppm, respectively,
whereas the present levels are 740 ppm and 850 ppm. The
estimated damages to California by the turn of the century
could amount to $40 million per year (8). In addition,
Arizona and the Republic of Mexico would also suffer severe
damages.
Imperial and Coachella Valleys, Southern California. The
high concentrations of salt in the water supply to Imperial
Valley, combined with problems of tight soils and high summer
temperatures, result in many difficulties for the farmer in
growing a crop. The biggest problem is maintaining a salt
balance in the root zone. A salt balance for the valley as
a whole was first achieved in 1949. The option of using
sprinkler irrigation is unavailable to the Imperial Valley
farmer in many instances because the combination of salt anc.
water deposited on a leaf in one rotation of the sprinkler
has dried and left only the salt, with consequent toxic
effects due to salt concentration and absorption, before the
sprinkler can complete another rotation. Salt toxicity
31
-------
g 5 io_ is
Scale of Miles
Figure 4 Coachella Valley, Salton Sea, Imperial Valley, and
Mexicali Valley.
-------
results in the demise of plant foliage. Because of the
tight soils, with consequent low infiltration rates, there
is a real difficulty in getting enough water to pass through
the root zone to assure that there is no salt accumulation
in the root zone, which would result in lower crop yields.
Cultural practices play a critical role in the infiltration
of the irrigation water into the soil profile. Also, seed
bed preparation is very critical. Changing the depth of
seed placement one-half inch may result in the seed not
germinating due to rapidly changing salinities in the soil
solution with depth as a result of furrow irrigation.
An interesting cultural practice in the Imperial Valley is
the use of sprinklers to germinate lettuce seeds. Oftimes
salinity is high enough in the seed bed to inhibit germina-
tion. Portable sprinkler lines are set in place and adequate
moisture added to leach salts and bring about uniform germin-
ation of the planted seed. Soon after seedlings emerge,
sprinkling is discontinued, sprinkler lines are removed, and
furrow irrigation resumed. This is a cultural practice
that has been learned from experiments and is used to assure
a uniform stand of lettuce, as an aid to harvesting.
The annual quantity of irrigation return flow from Imperial
Valley is 900,000 acre-feet, while Coachella Valley returns
100,000 acre-feet. The return flows from these two areas
are essentially the total inflow to the Salton Sea, which is
approximately one million acre-feet per year. Of the total
diverted to the valley, a minimum of 10-15 percent is
required for leaching in order to maintain a favorable salt
balance in the root ?pne. The leaching requirement of 10-
15 percent would be satisfactory if equilibrium conditions
existed. In practice, in order to gain on salt removal, a
greater amount of leaching is required. The Imperial Irri-
gation District estimates the leaching requirement to be
20 percent to accomplish present levels of salt removal
wherein the total annual quantity of salts removed is
greater than the annual quantity of salts brought into the
valley. Increasing salinity levels in the Colorado River
will also increase the required leaching fraction. Based
upon salt measurements of the inflow and outflow waters,
calcium and magnesium carbonates and gypsum are being pre-
cipitated in the soil/ while sodium and potassium chlorides
are being removed from the soil. The precipitation and
exchange of salt ions occur because the Colorado River water
is high in calcium, bicarbonate, and sulfate. The necessity
for maintaining a salt balance is somewhat alleviated by the
high proportion of dissolved salt that is gypsum, which pre-
cipitates as an innocuous salt in the soil profile.
33
-------
Salt balance studies have been reported for Coachella
Valley, which is located on the north and west side of the
Salton Sea, by Bower, Spencer, and Weeks (10). The 60,000
acres of irrigated land is served by the Coachella Branch
of the All-r American Canal, which diverts water from the
Colorado River at Imperial Dam. Part of the Coachella
Canal is concrete-lined and water diverted from the canal
is transported in concrete pipelines to the individual
farms, with the water being measured throughout the system.
The delivery and use of large amounts of water from the
Colorado River beginning in 1948 resulted in high ground-
water levels developing in the valley. To alleviate this
situation, tile drainage was installed. Presently, more
than half of the lands have tile drainage. The studies
showed that a salt balance (the annual tonnage of salts
leaving the irrigated area, which enters the Salton Sea, is
equal to or exceeds the annual tonnage of salts entering
the valley from the Coachella Canal) was achieved when half
of the irrigated land had tile drainage and the leaching
fraction was 30 percent.
The irrigation return flow from Imperial Valley and Coa-
chella Valley has a unique role related to water quality
problems in the Salton Sea. At the time the Salton Sea was
formed, in the period 1905 to 1907, it had essentially the
same salinity as the Colorado River. Prior to this time,
free salt was being mined in the area inundated by the
Salton Sea. The present salinity of Salton Sea is approx-
imately 40,000 ppm. At the time the salinity approached
that of the ocean, the California Department of Fish and
Game transplanted salt-water sport fish into the Salton Sea.
For some time, these sport fish had difficulty surviving due
to a lack of forage fish. Finally, a forage fish, the
Corvino from Mexico, was found which would survive in the
Salton Sea. Now, with salinities reaching higher levels than
the ocean, it looks like much of this salt-water sport
fishing will be lost. There is some talk of desalination.
Eventually, the Salton Sea will assume many of the charac-
teristics of Great Salt Lake. Reducing the quantity of
irrigation return flow reaching the Salton Sea would only
aggravate the present problems.
We11ton-Mohawk District, Arizona. Attempts to develop irri-
gation in the We11ton-Mohawk District of the Gila River
Valley were unsuccessful until Colorado River water diversion
was authorized by the Gila Project in 1947. The Gila River
proved an undependable supply as upstream development pro-
gressed, and irrigation from wells failed as water levels
declined and the groundwater quality deteriorated from
34
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continual evapotranspiration and recirculatxon (19). Soon
after the introduction of Colorado River water, the drain-
age problem became serious and was solved by the selective
placement of wells to remove the poor quality groundwater.
A concrete-lined channel was constructed to convey the
poor quality drainage from the valley without creating
further drainage and salinity problems in the lower lande,
Although this was a more expensive scheme, it was justi-
fied on the basis of benefits derived from preventing
further salt damages to productive lands. Further bene-
fits were derived by conveying the saline drainage waters
to the Colorado River downstream from Morelos Dam, the
diversion point for irrigation water going into Mexico.
If at some future time the quality of the We11ton-Mohawk
drainage water improves sufficiently, it may again be
used as a portion of Mexico's supply. Until that time,
the Mexican water quality is being protected by having
the saline drainage water bypass Morelos Dam. This is
cited as an example of diversion away from a portion of a
river system for the purpose of controlling the quality
of the water resources in the basin. Another example of
conveying drainage waters to a discharge point other than
the river system is in the San Joaquin Valley of
central California.
Rio Grande Basin
Salt balance studies have been conducted in the Rio Grande
Basin for a number of years. The results of a 20-year
study were reported by Wilcox (31) and are summarized in
Table 7. Several diversions for irrigation occur along
the Rio Grande between Otowi Bridge near Santa Fe, New
Mexico and Fort Quitman, Texas below El Paso. The four
main irrigated areas at the time of the study were as
follows: (a) 80,000 acres between Otowi Bridge and San
Marcial; (b) 15,000 acres between Caballo Dam and Leas-
burg Dam; (c) 70,000 acres between Leasburg Dam and El
Paso; and (d) 85,000 acres between El Paso and Fort Quit-
man. A close correlation exists between the irrigated
areas, decreased discharge, and increased salt load of
the river. While the discharge is decreased to one-fifth
its original value, the dissolved solids concentration
is increased almost 10-fold and the total salt load is
almost doubled.' Although the salt balance appears favor-
able between all stations except El Paso and Fort Quitman,
much more detailed information is required before positive
statements regarding the salt status of the irrigated
soils could be made. The overall effects have been almost
totally attributed to the use of water for irrigation.
The sources of salts returned to the river have not
35
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Table 7. Mean annual discharge and dissolved solids, Rio Grande.
I/
u>
Station
Otowi Bridge, N.M.
San Marcial, N.M.
Elephant Butte Outlet, N.M.
Gaballo Dam, N.M.
Leasburg Dam, N.M.
El Paso, Texas
Fort Quitman, Texas
Discharge
1,000 acre- ft
1,079
853
790
781
743
525
203
Dissolved
ppm 1,
221
449
478
515
551
787
1,691
Solids
000 tons
324
520
514
547
557
562
467
I/ Adapted from Wilcox (31)
-------
been identified. The dangers of such generalized conclu-
sions can readily be seen. More detailed investigations
will be required in order to suggest suitable and adequate
control measures.
The high salinities encountered in the Rio Grande have
resulted in agricultural damages to El Paso Valley because
the more salt-sensitive crops cannot be grown in this area.
The Mesilla Valley, which is roughly 40 miles upstream,
has a wider range of crops that can be grown because of
better quality water. The Hudspeth Irrigation District,
which is located below El Paso, has encountered serious
problems due to high concentrations of sodium salts, which
drastically affect crop production.
Long-term projections for El Paso show that municipal and
industrial water needs will require all of the flows in
the Rio Grande, but it is presently anticipated that a
large amount of this future water demand will have to
come from groundwater supplies. The problem is compounded
by the rapid growth rate of Juarez, which is located
across the river from El Paso in the Republic of Mexico.
Degradation of groundwater quality due to irrigation
return flows moving through the soil profile could result
in additional treatment costs when such water supplies
are used to satisfy municipal and industrial water require-
ments. At the same time, studies are needed to evaluate
the role of irrigation return flows in recharging the
groundwater basin.
Agricultural lands in the lower Rio Grande Basin exper-
ience some of the same cultural problems encountered in
Imperial Valley, namely tight soils and poor quality water.
Irrigation return flows are not subject to reuse except in
drought years when farmers pump from the drainage canals
to supplement their supply. Consequently, there has been
no real concern for the quality of drainage waters. A large
part of the irrigated area is tile-drained to control
groundwater levels and about 80 percent of the drainage
water from the Texas side does not return to the river,
but drains directly eastward to the Gulf Coast. No
information is available regarding the quantity of nit-
rates, phosphates, or pesticides being carried to the
Gulf by this route. Drains from the Mexican side do
return to the Rib Grande and are of very poor quality.
This occurs below Falcon Reservoir which supplies irri-
gation water to both Texas and Mexico. Careful farm
water management and special cultural practices are
required in order to move salts below the root zone and
insure a productive agriculture. The quality problems
37
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requiring further study for possible control are those
resulting from nutrient and pesticide transport to the
drainageways and eventually into the Gulf of Mexico.
A recent study in the lower Rio Grande Valley of south
Texas (7) has shown the need for institutional reform to
promote efficient water resource utilization. The insti-
tutional influences that were shown to hinder improved
water management practices were antiquated water rights
doctrine and an unuaually large number (34) of water con-
trol and irrigation districts in a three-county area. The
major recommendations for reform included: (1) negotiable
water rights; (2) consolidation of water districts into
one master district; and (3) rehabilitation of outdated
delivery and drainage facilities. Similar reforms could
well be recommended for many of the irrigated valleys of
the western states.
Central Valley of California
Sacramento Valley. The Sacramento Valley represents quite
a different problem with respect to irrigation return flows,
as opposed to the San Joaquin Valley. The annual flow of
the Sacramento River is somewhere between 14 and 18 million
acre-feet per year. There are one million acres of irri-
gated land in the valley. The quality of the water supply
is very good. The Sacramento River outflow provides dilu-
tion and flushing for the Delta area of the San Francisco
Bay system. In order to maintain the quality of water
within the Delta, the State does not want to allow further
degradation of the Sacramento River, along with controlling
waste discharges into the Delta. The California State
Water Resources Control Board intends to maintain the
quality of the Sacramento River.
The Sacramento Valley is a major rice producing area. Rice
is planted by airplane, fertilized by airplane (phosphates
are applied prior to planting on dry ground), and insecti-
cides are applied by airplane. The major pollutants result-
ing from these practices are nitrates, phosphates, and
pesticides.
One of the present problems concerning the Delta area of the
Central Valley is that a portion of the water supply is
being diverted by the State Water Project from the Sacramento
River Basin to southern California. Limited drainage prob-
lems in Sacramento Valley are occurring because of increased
irrigation provided by additional surface water supplies
being used on the west side of the Valley. These surface
water supplies are replacing the former pumped water
38
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supplies in some areas. At the present time, there are
approximately 50/000 acres which have high water tables
resulting from excessive water application.
San Joaquin Valley. In contrast to the Sacramento Valley
to the north, the San Joaquin Valley experiences consider-
ably greater water quality degradation in its irrigation
return flows. The valley contains about 8 million acres
of irrigable land of which about half is presently irri-
gated and approximately half of that acreage has a poten-
tial drainage problem. This comprises about 40 percent of
the irrigable land of the State, but, without water imports,
has available only one-sixth of the State's water resources
(Figure 5). Importation of water from the north resulting
from the California State Water Project, the Federal Delta-
Mendota Canal, and the San Luis Project has allowed vast
new acreage to be placed under irrigation (23), particularly
on the arid western side of the valley. The irrigation
water applied is of good quality with a total salinity of
less than 500-700 ppm. Due to the high concentration of
natural salts and native nitrates in the soils, drainage
from the area will have salinities as high as 20,000 ppm,
which may be reduced to the 3,000 ppm range after 50 years
of irrigation and its concomitant leaching of the soil pro-
files. This severe water quality degradation precludes the
reuse of the drainage water and has forced the considera-
tion of drainage canals to convey the irrigation return
flows to the ocean via San Francisco Bay. Portions of a
federally constructed San Luis Drain have already been com-
pleted but are not yet conveying drainage waters. Farm
tile drainage systems, which are not extensively used at
the present time, return either to the San Joaquin River or
are pumped back into the canal delivery system.
A unique problem exists in the San Joaquin drainage waters
due to the relatively high nitrate content. A few studies
to date have indicated the major source in this area to be
natural nitrates in the soils and to a lesser extent,
applied fertilizers. The possibility of damage to San
Francisco Bay by release of these nitrates prompted exten-
sive studies into potential treatment measures that might
be used for their removal. Algae stripping and biological
denitrification methods have been shown to be feasible
solutions. Other researchers, working with submerged tile
drains, have'achieved a smaller degree of success. The
cost of treatment is still high and further studies will no
doubt be conducted before a final decision on the treatment
scheme to be used will be made. The economic and legal
problems involved may very well turn out to be the major
blocks to solving the problem. Economists have investi-
gated the abilities of the irrigators to bear the costs of
39
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0 16 32
—--—Si^^iB
SCALE IN MILES
LEGEND
——— SAN JOAOUlN MASTER DRAIN
___ TOPOGRAPHIC DIVIDE
""iiiiuiiiiii EDGE OF VALLEY FLOOR
1 j POTENTIAL DRAINAGE PROBLEM AREAS
Figure 5. San Joaquin Valley
40
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state-federal drains to convey irrigation return flows
out of the valley. It is doubted that farmer acceptance
of these added costs will be achieved until they are forced
to do so. This still leaves the added cost of treatment
to be considered and a further decision regarding proper
and just allocation of those costs.
Under our present system, controlling practices on-the-
farm is virtually impossible unless some means can be
developed whereby there will be economic incentives for
reducing water pollution. Extensive demonstration and
education programs will be required to promote acceptance
of improved farm management practices. This is true not
only in the San Joaquin Valley, but in other critical prob-
lem areas as well. Control of leaching practices through
improved water management in the newly irrigated fringes
of the valley may be necessary to protect the lower lying
lands from excessively saline groundwater seepage.
Detailed salt mass balance studies will be required to
evaluate the greatest long-term benefits and to protect
those lands placed in jeopardy by the problem of increased
salinity in drainage waters. These also are required to
develop and recommend potential salinity control measures
that could be most effective in protecting the quality of
surface and groundwater resources. Some trade-off between
the need for crop production and the need for reduced
pollution may be necessary.
Columbia River Basin
The water quality problems resulting from irrigation return
flow are extremely varied in the Columbia River Basin.
Problems involving nitrates, phosphates, nematodes, sedi-
ments, and pesticides are prevalent in this region.
Attempts to undertake solutions to these problems are
important particularly since the problems will increase
in complexity as the water supplies become more fully util-
ized.
Yakima Valley, Washington. One of the major areas of irri-
gation return flow quality problems is the Yakima Valley.
There are presently approximately 400,000 acres of land
under irrigation in the valley, with the potential for
another 300,000 acres to be irrigated if the water supply
were made available to some of the higher lands. An exten-
sive irrigation return flow study in the Yakima River Basin
(27) has shown the major water quality problems resulting
from irrigation. The following discussion summarizes the
findings of that study.
41
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The Yakima River drains an area of 6,120 sq. mi., including
over 400,000 acres of land irrigated for the production of
a variety of crops (Figure 6). It has a mean annual flow
of 3,900 cfs which is partially regulated by six reservoirs
in the headwaters. Natural water quality variations occur
with changes in the rate of runoff and reservoir releases.
In the lower 80 miles of the valley, the summer flow of
1200 to 2000 cfs consists almost entirely of irrigation
return flow, and during the irrigation season, the entire
flow of the river is diverted several times for irrigation
use. The study revealed that irrigation return flow was
the major factor influencing the overall quality of the
Yakima River and that leaching and subsurface drainage
were responsible for the increased salinity and change in
ionic composition of salts in the river. Thus, irrigation
return flows were the major contributors to the 10-fold
increase in dissolved solids, from 40-50 ppm in the head-
waters to 400-500 ppm below the irrigated areas. Much worse
water quality degradation results from sediment transport
and nutrient releases to the river. Over-irrigation and
fertilizer applications in excess of crop requirements
were found to be the major causes of water quality degrada-
tion downstream. Increased turbidity (suspended solids)
was particularly bothersome to downstream irrigators and one
of the main reasons why sprinkler methods are not used more
extensively. Improved water and fertilizer management
practices were suggested as major factors in improving the
quality of irrigation return flows in the entire valley
area. The lack of adequate control over water delivery and
water use results in over-irrigation. Although the water
allotment is from three to three and one-half acre-feet per
acre, the actual use was found to be as much as four to
six acre-feet per acre per season.
Faulkner and Bolander (13) have investigated the transpor-
tation of nematodes in surface irrigation return flow, as
well as the establishment of plant parasitic nematodes upon
host plants. Their findings in Yakima Valley showed that
plants irrigated with surface irrigation return flow became
heavily infested with prarsitic nematodes. At the same
time, plants irrigated with groundwater supplies did not
become infested.
In summary, the major water quality problems occurring in
the Yakima River Basin and other irrigated areas in the
State of Washington are: sediment transport, nitrates,
salinity (only in localized areas), nematodes, phosphorus
on sediments, high bacterial (coliform) content in surface
return flows, and increased temperature of surface return
flows.
42
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CANADA
WYO.
CALIFORNIA j NEVADA ; UTAH
LOCATION MAP
Kittitas
Irrigation
Project
©
SCALi: IN MIL
Roza Irrigation
Project
Tieton
Irrigation
Project
Wapato
Irrigation
Project
Sunnyside
Irrigation
Project
Figure 6 Irrigation development in the Yakima valley.
43
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Snake River Valley. Irrigation return flows from the three
million acres of irrigated land in the Snake River Basin
present no really serious salinity problems. If the total
potential of eight million irrigable acres were developed
(Figure 7), water quality problems could develop. The chief
reason for the quality of flow in the Snake River being main-
tained satisfactorily is that several large natural springs
flow into the river downstream from the major irrigated
areas. The Thousand Springs area below Twin Falls, Idaho
contributes an average inflow of 4.3 million acre-feet per
year. The quality of this inflow is very good (even better
than Snake River water diverted above Twin Falls at Milner
Dam) and results in a large dilution effect.
A recent sutdy (6) of the water-soluble nitrate, phosphate,
and total salt balance on a large irrigation tract in the
Twin Falls area is an excellent example of the type of
investigations needed in many irrigation return flow problem
areas. Typical information from such studies includes:
quality and quantity of applied water, surface runoff, and
subsurface drainage; fate of applied water; and the source
of water quality problems from irrigation return flows. The
major problems arising from this large tract were the
.nitrate-nitrogen contributed by subsurface drainage and
sediment transport in surface return flows. The subsurface
drainage water from the area contained lower total salt
concentrations than irrigation water diverted at many loca-
tions in the Colorado and Rio Grande River basins. In areas
not served by a canal system, some salt problems have devel-
oped from pumping groundwater with salt concentrations as
high as 3,000 micro-mhos (electrical conductivity).
Examples of excessive water useage in areas of ample supply
are the unusually high water duties allotted. In the Burley,
Idaho area, the water duty (acre-feet of water diverted
during the irrigation season for each acre of land) is
approximately 6.5 acre-feet per acre per irrigation season;
in the Rupert area, it is roughly 9 acre-feet per acre; and
in the Rigby area of the upper Snake, the water duty goes
as high as almost 13 acre-feet per acre. These are totally
unrealistic when it is realized that crops (in Twin Falls
tract, for example) require from 23 inches (spring grain)
to 42 inches (irrigated pasture) estimated evapotranspira-
tion for the entire year (6). In some rivers, the large
quantities of seepage and deep percolation losses may bene-
fit downstream water users because the return flows may
coincide with periods of low streamflow and high water
demands by crops. These problems fall within the realm of
water management and serve to illustrate some of the anti-
quated institutional constraints in approaching optimum
development of water resources. Although a number of
44
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•l
I \NONTWA
(IDAHO
*ASH,NGTON
CALIF. 'NEVADA WH UTAH
LOCATION MA"
& .
•&V.V'. c
Potentially Irrigable Area
Presently Irrigated
10 0 10 20
J I.
SCALE
Figure 7
Presently Irrigated and Potentially Irrigable Areas in the Upper Snake
River Basin.
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irrigated valleys having high water diversion rates do not
presently create serious water quality problems, such prac-
tices become more critical as the water resources of the
river basin become more fully utilized.
Some degree of management control is being achieved in
southern Idaho through commercial concerns who sell a
scientific irrigation scheduling service to the farmer.
The potential for using this approach as a tool to limit
quantity as well as time of application will be discussed
more fully in the following section of this report (Section
VI. Potential Solutions and Control Measures).
Odessa, Washington area. The Odessa area in the State of
Washington has pumped domestic water from a shallow aquifer
which occurs at depths of about 200 feet. Later, wells
were drilled for purposes of supplying water to irrigated
lands. These irrigation wells were drilled into deeper
aquifers at depths of 400 to 700 feet below the ground sur-
face. The return flows from the irrigated lands have now
contaminated the shallow domestic wells. The drilling of
irrigation wells began as a means of supplemental water
supply for irrigation, but the area is now being more
intensively irrigated and higher cash value crops are being
grown. Also, the small lakes in the area are used for
irrigation, but recreational potentials may be lost because
of deteriorating water quality due -to irrigation return
flows.
The East High Project of the Columbia Basin, which would
consist of approximately 500,000 acres of irrigated land,
would also add to the problem in the Odessa area. The
present problems in this area due to the development of
groundwater supplies, and the consequent problem of irri-
gation return flows, would be considerably aggravated by
the additional irrigation of 500,000 acres of new land.
Horse Heaven Hills, Washington. The Horse Heaven Hills
area, which is located south of the Yakima River, has
approximately 200,000 acres that could be easily placed
under irrigation. Another 300,000 acres could be potentially
placed under irrigation. The last 300,000 acres would create
more of an irrigation return flow problem because this area
consists of rolling hills and consequently would be faced
with sediment erosion. These lands also contain over 6
million tons of leachable soil salts, which would be
removed in drainage waters upon irrigation development. This
is a typical problem for many of the agricultural lands in
Washington which might be placed under irrigation in the
future.
46
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Lower Columbia Basin. A significant problem in the sandy
soil areas of the lower Columbia River Basin is the early
season irrigation for wind erosion control. This sandy area
encompasses roughly 100,000 to 200,000 acres. Sprinkler
irrigation is used to apply 3-5 inches of water from the
time of pre-plant until early leaf stage for potatoes and
beets. Much of the fertilizer applied prior to planting is
leached from the root zone before any significant plant
growth occurs.
The problem of high nitrates in groundwater came into focus
in the lower Columbia River Basin during 1962, when two
cases of nitrate poisoning were reported. Subsequent
analysis of well-water in this area by the U.S. Bureau of
Reclamation disclosed that the water supplies from many
wells contained nitrate concentrations ranging from 50 to
500 ppm. The source of this nitrate, whether it be from
fertilizers or natural soil deposits, must be investigated
before any recommendations on water or fertilizer practices
can reasonably be initiated.
Santa Ana Basin, Southern California
The University of California, both at Riverside and Davis,
has been deeply involved in studies in the Santa Ana River
Basin. There are roughly 300,000 acres of irrigated land
in the basin. The Santa Ana Water Planning Agency requested
that a survey be made of nitrogen inputs in the valley/
where the nitrogen is going, what nitrate problems exist,
and recommend management practices to improve these problems,
The problems consist of water and fertilizer management on
these irrigated lands, municipal-industrial wastewaters, as
well as the disposal of animal wastes on the land.
With respect to fertilizer efficiency, there are some
examples of vegetable crops in Santa Ana Basin where 300 to
400 pounds of nitrogen per crop per acre are needed but the
application irate is more nearly 1,000 pounds of nitrogen
per acre, with some cases as high as 1,700 pounds of nitro-
gen per acre. The higher usages of nitrogen are usually
related to higher water usage as well. Thus, nitrogen
efficiency can be related to water use efficiency, as well
as management efficiency, with excessive water application
leading to excessive leaching of plant nutrients before
they can be utilized by the crop.
The basin is divided into two portions, an upper basin and
a lower basin. This basin is divided by a natural dike
almost at the county line (Orange County). Also, there is
47
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a reservoir located near this dike. The groundwater table
is fairly deep, but the salinity of this groundwater is
increasing with time. The planning agency is very concerned
about this increased salinity. It would be desirable to
control the amount of salts and nitrates reaching the ground-
water and, consequently, the amount of salts and nitrates
reaching the reservoir at the county line. This reservoir
has been the water supply for appreciable groundwater
recharge in Orange County.
An informative area of different estimates by the planning
agency and the university was the travel time of water mov-
ing from the ground surface down to the groundwater table.
The planning agency developed map contours of travel time.
These travel times were usually on the order of two or
three years. In contrast, the university arrived at travel
times in excess of ten years. This points out the diffi-
culty in using existing data and rough estimates for arriv-
ing at travel time as opposed to making physical measure-
ments in the soil in order to make an estimate.
Bear River, Utah
The headwaters of the Bear River are located in Utah. The
river travels into the southwest portion of Wyoming, thence
flows across southeastern Idaho and returns to northern
Utah, where it terminates in the Great Salt Lake and is
lost by evaporation. In the meantime, the flows have been
diverted a number of times for irrigation. Flood irrigation
is practiced on much of the upstream lands, with downstream
users being dependent upon the return flow. Before reach-
ing the Great Salt Lake, the flows of the Bear River pass
through the Bear River Migratory Bird Refuge near Brigham
City, Utah. The quality of the flows traveling through the
refuge has been deteriorated due to irrigation return flow,
surface water evaporation, and evapotranspiration by phrea-
tophytes. The quality problem becomes serious during
periods of low flow when most of the water is irrigation
return flow. Although the irrigation return flow is essen-
tial, from a quantity standpoint, during periods of low flow,
the poor quality of this water limits its usefulness.
Carson River, Nevada
The Carson River (Figure 8) has some similarities to the
Bear River. The headwaters of the Carson River are in the
Sierra Nevada Mountains. The flow is generally in an
easterly direction. Large quantities of water are diverted
at the base of the mountains to irrigate forage crops in
48
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•
WINNEMUCCA
,'LAKE /
Pyramid Lakeu Indian Reservation
Stillwater Wild Life
Mgt. Area
0 5 10 15
•
SCALE IN MILES
PAIUTE DAM
a RES.
DERBY
DIVERSION DAM
Truckee'cVrsdn
Irrigation Area
CARSON
LAKE
IRRIGATION AREA
Figure 8. Lower Truckee and Carson Rivers.
-------
Carson Valley. Eventually, the flows returning to the river
are stored in Lahontan Reservoir, which is one of the earlier
U.S. Bureau of Reclamation projects, just upstream from
Fallon, Nevada. The stored waters are used to irrigate lands
in the Fallon area, with the water duty (acre-feet of water
diverted during the irrigation season for each acre of land)
being very high. Consequently, the water table in the area
is very near the surface and large populations of phreato-
phytes are supported (2).
The irrigation return flows are conveyed to the Carson Sinks,
where the water is lost by evaporation. This sink area is
managed as a waterfowl refuge. At the present time, quality
problems in the refuge resulting from irrigation return flow
are not as severe as encountered in the lower Bear River, but
future water demands, as well as Indian water rights, can be
expected to change this situation considerably. A balance
will have to be reached between requirements for improved
irrigation water management to release water supplies to sat-
isfy Indian water rights, along with allowing a sufficient
quantity of irrigation return flow having a satisfactory
water quality to meet waterfowl needs in the refuge.
Upper Missouri River Basin
There are numerous examples of irrigation return flow quality
problems throughout the Upper Missouri River Basin. Most of
the quality problems that can be cited are the result of
increased salinity, but this is largely due to a combination
of two factors. First of all, the water supplies are fairly
plentiful, which tends to mask quality degradation. Secondly,
there is a real lack of documented studies regarding irriga-
tion return flow quality in this region of the United States.
The present knowledge on quality problems is the result of
irrigation system failures or recent investigations undertaken
for the purpose of expanding irrigated agriculture.
The State of Nebraska has plentiful water supplies and consid-
erable potential for increasing its irrigated acreage. At
the present time, more than 4 million acres of land are being
irrigated in Nebraska. The present growth rate is approxi-
mately 250,000 acres of new irrigated land per year. Nebras-
ka has 16 million acres of heavy soils amenable to surface
irrigation and another 18 million acres of sand hills. At
the ,same time, 8 million acre-feet of water per year is leav-
ing the state. Thus, this water could be made available to
new irrigated lands.
The water supply for much of the irrigated acreage in Nebraska
is pumped from groundwater basins. Water reuse systems are
50
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rapidly coming into existence in lower Nebraska (Lincoln to
Hastings) because of groundwater pumping costs. The cost of
a water reuse system has been estimated to be comparable to
a pumping lift of 50 or 60 feet. Many farmers in this area
are now pumping groundwater 100 feet.
Presently, the major irrigation return flow quality problem
in Nebraska is the result of inefficient water use on a USER
project in the Tri-County area. The groundwater table has
risen 100 feet in the last 20 years, until it is now near the
ground surface, with resultant losses in agricultural produc-
tivity. The cost of surface water in this area is much lower
than for pumping groundwater, which is at least part of the
reason for the inefficient water use.
There are a number of examples of irrigation project failures,
or near failures, in Wyoming. The Riverton Project has
suffered from sodic conditions, which now make land reclama-
tion economically unfeasible for many farms. Much of this
problem could have been alleviated if canals had been lined,
on-the-farm water management practices instituted, and
drains constructed at the initiation of the project.
Areas in North Dakota and South Dakota, which are experienc-
ing irrigation development, will face many salinity problems.
Many of these lands are underlain by soils high in natural
salts. Because of soils having low permeability, drainage
will be required for many of these irrigation projects to
insure their success. At the same time, irrigation return
flow quality problems will increase substantially.
The Garrison Diversion Unit in North Dakota may be cited as
an example. The plan for development involves the diversion
of Missouri River water from Garrison Reservoir into the Red
River of the North Basin to irrigate ultimately a total of
one million acres. The lack of adequate prediction tech-
niques precludes valid estimates of the impact of the irriga-
tion return flows on the quality of Red River water. At the
insistence of irrigators and water district personnel, the
original plans were revised to include lined canals and pipe-
line distribution systems. Advantages of the revised plan
include: adaptability to sprinkler methods and reduced land
preparation costs; increased water control and water-use
efficiencies; reduced weed control requirements; limited sub-
surface drainage needs; and lower operation and maintenance
costs. No estimates of improved quality of return flows due
to these revised plans (vs. original plan) were suggested,
although some improvement would no doubt result. The need
for prediction capabilities in newly irrigated areas is
again emphasized.
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Western Salinity Control Costs
Some informative estimates can be made based upon present-day
knowledge and the projections for future land use (Table 3)
and water use (Tables 5 and 6). Studies in the Twin Falls
area (6) and the Colorado River Basin (8) indicate that the
range of values for salt pickup from irrigated lands is
roughly 1/2-8 tons per acre per year. An average salt pickup
rate might be 2 tons per acre per year. Future water-use
projections indicate a two-fold increase in irrigation effi-
ciency by the year 2000. Consequently, a reasonable estimate
for salt pickup reduction would be one-half, or 1 ton per
acre per year. Using an estimated irrigated acreage at the
turn of the century (year 2000) of 50 million acres for the
western states, the annual reduction in salt load reaching
our groundwater and surface water supplies would be 50 million
tons per year.
Using the Colorado River Basin reconnaissance investigations
as a guide, the total annual unit costs for achieving an
annual salt load reduction of 50 million tons might be $20
per ton per year. Thus, the total annual costs would be
1 billion dollars, of which half, or more, could be attributed
to salinity control, with the remaining costs being attributed
to direct benefits for the irrigated croplands.
The benefits resulting from salinity control will increase
dramatically with time. Projections for future water demands
indicate many of.the western river basins will be approaching
full utilization of existing water supplies within the next
50 years. As these water supplies become more fully utilized,
the necessity for salinity control, and consequently the
benefits from salinity control measures, will increase expon-
entially. As a conservative estimate, the benefits should
exqeed the total costs by 50 percent. Also, the total costs
for salinity control on an acre-foot basis are very minimal,
being roughly $3-$10 per acre-foot per year for diverted
water.
The above estimates are very crude due to a lack of better
data. However, these estimates do provide "ballpark" values,
which are advantageous in gaining an insight into the costs
and benefits of salinity control. Other benefits such as
reductions in sediments, phosphates, nitrates, and pesti-
cides have not been taken into account, but would increase
the benefits accruing from improved water management.
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SECTION VI
POTENTIAL SOLUTIONS AND CONTROL MEASURES
Prevention or control of quality degradation to water
resources due to irrigation return flow is both difficult
and expensive to achieve. Potential solutions and control
measures involve physical changes in the system, which
can be brought about by constructing improvements to
existing systems or by placing new institutional influences
upon the system, or a combination of both. Since irrigation
return flow is an integral part of the hydrologic system,
control measures for managing the return flow from an irri-
gated area must be compatible with the objectives for
water resource management and development in the total
system. Irrigation return flow quality control is one
component in the management of the water resources in a
river basin, which has been long neglected. In many cases,
environmental quality has been subjugated by economic
pursuits.
The irrigation return flow system can be subdivided into
three major sub-systems: (a) the water delivery system;
(b) the farm; and (c) the water removal system. The water
delivery system can be further subdivided into two com-
ponents; namely, (a) the transport of water and pollutants
from the headwaters of the watershed to the cross-section
along the river where water is diverted to irrigate crop-
lands, and (b) the transport of water and pollutants from
the river diversion works to the individual farm. The
farm sub-system begins at the point where water is deliv-
ered to the farm, which is usually the point of highest
elevation on the farm, and continues to the point where
surface water is removed from the farm, which is usually
the lowest elevation ground surface on the farm. Also,
the farm sub-system is defined vertically as beginning
at the ground surface and terminating at the bottom of
the root zone. The water removal sub-system consists of
(a) the surface runoff from the tail end of the farm, and
(b) water moving below the root zone.
In most instances, the quality problems in the water
removal sub-system are minimized by having highly effic-
ient water delivery and farm sub-systems. Minimizing the
quantity of surface runoff will assist in alleviating
quality problems due to sediments, phosphates, and
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pesticides; whereas minimizing deep percolation losses from
irrigated lands will reduce quality problems due to salts,
including nitrates, in areas where salt pickup occurs.
Water Delivery System
The importation of high quality water from adjacent river
basins, weather modification to increase precipitation and
runoff from the watersheds, bypassing mineralized springs,
evaporation reduction from water surfaces, and phreatophyte
eradication are some of the available measures for improv-
ing the quality of water diverted from a river. Con-
sequently, they play a role in the management of the irri-
gation return flow system. More feasible approaches may
be found in the control of losses from storage and convey-
ance systems.
Canal and lateral lining. Many unlined irrigation canals
traverse long distances between the diversion point and
the farm land. Seepage losses may be considerable, result-
ing in low water conveyance efficiencies. Canal lining
has traditionally been employed to prevent seepage 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 to receiving waters
has only recently been given serious attention. A recent
report (4) showed that average seasonal canal losses
varied from 13 percent of the diversion on the Uncompahgre
Project, Colorado, to 48 percent of the diversions on the
Carlsbad Project, New Mexico. If we assume a very conser-
vative estimate that 20% of the total water diverted for
irrigation in the United States is lost by canal seepage,
the loss to the intended users would be 24 million acre-
feet per year. This quantity of water would irrigate
eight million additional acres, using three acre-feet per
acre, or it would contribute an additional dilution effect
to the benefit of downstream users.
If soils along the canals are high in residual salts, the
salt pickup contribution from this source could easily
exceed that leached from the irrigated land to maintain a
salt balance. The time required to leach these residual
salts would depend upon the quantity of seepage and the
quantity of salts. In addition to the quantity of water
saved, 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. Research is currently
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underway to evaluate the effect of canal lining on the
quality of drainage water returning to the river near
Grand Junction, Colorado.
Evaporation losses from canals commonly amount to a few
percent of the diverted water. The installation of a
closed conduit (pipeline) conveyance system has the advan-
tage of minimizing both seepage and evaporation losses.
Either lined open channels or closed conduits will reduce
evapotranspiration losses due to phreatophytes and other
non-economic vegetation along canals. The closed conduit
system uses less land and provides for better water con-
trol than a canal system. Water quality improvement may
very well prove to be the greatest economic justification
for closed conduit systems because of minimal seepage
losses and considerable flexibility in water control.
Project efficiency. A key element that must be provided
in the water delivery system is flow measurement.
The amount of water passing key points in the irrigation
delivery system must be known in order to provide water
control and attain a high degree of water use efficiency.
Many present day systems employ no flow measuring devices,
and, in some cases, the individual farmer operates his
own turnout facility with no close control of the amount
diverted to the farm.
Economics play a major role in existing project irrigation
efficiencies, and a close correlation exists between water
abundance and/or cost of water and project efficiency.
For example, where water is scarce or high in cost, the
efficiencies are found to be higher. Project management,
as well as farm management, involves balancing the immed-
iate cost of water against the higher labor and investment
costs required to use it more efficiently (17). The costs
of inefficient water use oftimes are not recognized immed-
iately but may be reflected in reduced yields due to nut-
rient losses or increased salinity, or in extra drainage
facilities required later to control rising water tables.
On-the-Farm WaterManagement
The most significant improvements in controlling irriga-
tion return flow quality will potentially come from
improved on-the-farm water management. This will be par-
ticularly true for areas containing large quantities of
natural pollutants, such as salts, in the soil profile.
In such situations, the key is to minimize the subsurface
return flows, thereby minimizing the quantity of pickup.
Irrigation practices on the farm are the primary source of
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present return flow quality problems. Besides improve-
ments at the source/ other improvements can be accomplished
in the water removal system. Due to the nature of irri-
gated agriculture, whereby salts must be leached from the
root zone, an optimum solution will, in most cases, require
improvements in on-the-farm water management. Numerous
technological and institutional concepts could be utilized
to accomplish improved water quantity and quality manage-
ment. Some of the technological possibilities are cited
immediately below, whereas the institutional possibilities
are discussed later in this section (Section VI).
Cultural practices. When the soils to be irrigated are
tight (low infiltration rate and low permeability), and the
water supply delivered to the farm is highly saline, cul-
tural practices become extremely significant if crops are
to be grown successfully. Under these conditions, the
management alternatives become: (a) use more salt tolerant
plants (which are usually lower in cash value); (b) use
special soil tillage practices (which cost more); (c) leach
in the off-season; (d) leach the field one year and plant
a crop the next year; (e) prepare the seed-bed more care-
fully; or (f) control the timing and amount of water being
applied. Usually, these problems must be faced in the
lower regions of- a river basin, where the accumulative
effects of upstream water quality degradation, along with
having finer soils resulting from river deposition, create
difficult management conditions.
In general, the deeper water is stored in the soil, the
more slowly it will be removed by evapotranspiration. Soil
structure, texture and stratification are the principal
properties that control distribution of water storage in
the soil. In extreme cases, deep tillage may be required
to disrupt slowly permeable layers and permit greater
water storage capacity, as well as deeper root penetration.
At the same time, excessive or unnecessary tillage can be
detrimental to stored soil water, increasing evaporative
losses when the crop needs it most. Therefore, cultural
practices can play a significant role in overall farm water
management.
Fertilizers. There is a strong relationship between water
use efficiency and fertilizer use efficiency. Applying
excessive quantities of water to the croplands results in
leaching of fertilizer materials below the root zone, where
they are unavailable for plant growth. One real potential
for improving nitrogen use efficiency over some present
management practices would be the use of slow-release fer-
tilizers. There is still a need for improved technology
for slow-release fertilizers to match nitrogen release with
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nitrogen needs by various plants. At the present time,
urea-based slow-release fertilizers cost about 40* per
pound of nitrogen, whereas urea nitrogen costs approxi-
mately 10* a pound of nitrogen. Taking into account the
efficiency of nitrogen use, the difference is only a
factor of 2. Urea originally cost 30$ to 40* per pound
of nitrogen, but this cost dropped to 10* per pound of
nitrogen as the volume used increased. If penalties for
nitrogen discharge were imposed, slow-release fertilizers
would be predominant in areas where nitrogen problems
occurred. The use of slow-release fertilizers also has
the advantage that by a proper match between nitrogen
release and nitrogen needs by plants, only one fertilizer
application would be required per season, rather than two,
on vegetable crops. When applying fertilizer to crops
which are not very salt tolerant, it then becomes necessary
to limit the amount of fertilizer being applied. Another
solution to this problem would be the application of fer-
tilizer in small amounts with the irrigation water through-
out the growing season, essentially spoon-feeding to meet
crop requirements. Continual application of nitrogen fer-
tilizer may impair ripening of certain crops.
Water control. In order to attain high irrigation appli-
cation efficiencies, positive control of the timing and
amount of water being delivered to the farm is required.
The irrigator must also be able to control the water
supply as it moves across the farm. The water delivery
rate must be subject to regulation as well as the quan-
tity applied at any given irrigation. Reducing seepage
losses from farm ditches, preventing tailwater losses,
improving water distribution over the field, and reduc-
ing unnecessary deep percolation losses are probably the
most significant areas for improvement (24). Related to
distribution system losses is water use by non-economic
vegetation in or adjacent to farm ditches. Such plants
not only extract water directly from the supply, but
also from the soil under and adjacent to the ditch.
This extraneous vegetation retards flow in the ditch and
increases seepage and evaporative losses, and in extreme
cases, may cause water waste by overflowing or breaking
the ditchbank. Reduction of these losses is essential
to water control on the farm.
Application methods. The effect of methods of applica-
tion on the quality and quantity of return flow has not
received detailed study. Conventional surface methods
are most commonly used because of their low initial cost,
while sprinkler methods are used because of their adapt-
ability to a wide range of field and surface conditions
and possibilities for reduced labor costs. In most areas,
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there is a real need to "tune-up" the existing irrigation
systems, thereby attaining the highest practicable irri-
gation application efficiency that can be achieved with
these systems. New and unique approaches to application
methods need to be found. Two that appear to offer promise
in the control of both quantity and quality of return
flows are subsurface application and drip or "trickle"
methods.
With subsurface irrigation, water can be applied to the
crop in small amounts and at frequent intervals so that
evaporation and the resultant increase in salt concentra-
tion are reduced. The average water content of the soil
can be maintained below field capacity (at points of mois-
ture application, the water content is above field capa-
city) , so that some precipitation can be stored in the
soil. Comparable crop yields have been produced with as
much as 40 to 50 percent less water than is required with
furrow irrigation. Thus, limited water supplies can be
extended or the acreage which can be irrigated with a
given constant water supply can be nearly doubled. Appli-
cation rates can be closely controlled and the method can
be readily automated.
The drip irrigation technique has been developed in Israel
and received enthusiastic interest among many researchers
throughout the arid regions of the world. The major advan-
tages include increased crop yield, reduced salinity
damage, and shortened growing season with earlier harvest.
The method involves the slow release of water on the sur-
face near the base of the plants. Evaporation losses are
greatly reduced and moisture release is confined to the
area of the plant root system. Salts will accumulate in
certain portions of the root zone during the growing
season, which must eventually be leached. Some very
different, but little understood, salt problems may result
from this system.
Evapotranspiration control. Control of evaporation and/or
transpiration offers another means of increasing irriga-
tion efficiency and improving the quality of irrigation
return flows. Such practices as mulching and reduced
tillage can be highly advantageous in reducing soil water
evaporation. Blevins, e_t a!L (3) demonstrated, with no-
tillage studies on corn, a significant decrease in soil
water evaporation and greater ability of the soil to store
water for use by the crop. By conserving soil moisture,
higher corn yields were produced. Surface mulching
either with crop residues or artificial barriers has
proven effective in reducing water vapor transfer to the
atmosphere. Certain surface active agents also have been
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shown beneficial in more rapidly establishing a dry barrier
at the soil surface and thus reducing evaporative water
loss (18). The irrigation methods described above (sub-
surface application and trickle irrigation) offer a great
potential for reducing the nonbeneficial evaporative losses
of irrigation water applied, thus increasing irrigation
efficiencies.
Robins (24) provided an excellent review of the subject
of evapotranspiration control as related to irrigation
requirement. Attainment of any reduction of evapotrans-
piration, either beneficial or nonbeneficial, would reduce
the quantity of irrigation water required for successful
crop production. It has been estimated (1) that nonbene-
ficial use of water by phreatophytes and other water-loving
plants amounts to 25 million acre-feet of water annually
in the 17 western states. This amount obviously is lost
from the potential for growing economic crops and represents
a sizeable fraction of the total water resource. Reduction
of this water use by any means possible represents a prac-
tical way to increase river flows and thereby reduce salt
concentration.
Possibilities exist for reducing evapotranspiration of
economic crops by altering climatic, soil, plant, and water
management practices (24). Basically, evapotranspiration
is an evaporative process controlled largely by the clima-
tic factors, solar radiation, temperature, relative humid-
ity, and wind velocity. Obviously, most of these would be
difficult to control in large field areas. Three, broad
groups of antitranspirants that have been investigated are:
(a) reflective materials that decrease the heat load on the
leaf; (b) film-forming materials that hinder the escape of
water vapor from the leaf; and (c) stomata-closing mater-
ials that increase stomatal resistance to water vapor trans-
fer (10). Each of these types has been proven effective
in reducing evapotranspiration, but as yet their use on a
large scale has not been practiced. In addition to anti-
transpirants, substitution of cool season for warm season
crops, and plant breeding and selection to achieve greater
water use efficiency, have been suggested as potential
control measures.
Optimum irrigation scheduling to extend the irrigation
interval and apply water when needed and in the correct
amount can exercise beneficial control over evapotranspir-
ation, particularly during periods when crop cover is
incomplete.
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Pumpback system. One excellent technique for managing
irrigation return flows would be the use of a pumpback
system for tailwater control. Such a system would increase
irrigation efficiency and minimize pesticides, phosphorus,
and heavy metals returning to the return flow system. This
would also serve as a self-policing system since the farmer
would be more prone to be careful about harmful pollutants
being placed on the land or in the water.
The pumpback system can be highly advantageous for controll-
ing sediment. Rather than allowing the water and sediment
from surface irrigation return flow to be transported to
the next farm, or back to the river, the surface return flow
may be collected and recirculated. A tailwater pit for
collection and storage will also serve as a sediment trap,
where much of the suspended material will be deposited.
Thus, improved irrigation practices would likely result in
order to minimize the quantity of water and sediment leav-
ing the cropland. Enforceable regulations may be required
to effectively control tailwater losses.
Irrigation scheduling. Early studies by Israelson in about
1930 and later studies during the 1950's and 1960's have
shown that in most irrigated areas the amount of water
applied and the timing of this water application are quite
random. For example, oftimes when the farmer finds that his
field is dry, he will irrigate, but. the irrigation application
may be more than is really needed by the crop. Thus a
two-fold problem occurs where the plant has already been
stressed because of the field being too dry, which means
that the yield has already been reduced. The second prob-
lem is due to more water being applied than was really
necessary. In extreme cases, this might even lead to a
problem of reduced aeration of the soil.
One of the more interesting areas of water management con-
trol presently being explored is that of optimum irrigation
scheduling. The purpose of irrigation scheduling is to
advise a farmer when to irrigate and how much water should
be used (15,16) . Primarily, a farmer relies on visual
indications of crop response to decide when to irrigate,
or he may have to irrigate on a fixed water rotation system.
Irrigation scheduling is geared towards taking soil mois-
ture measurements, along with computing potential consump-
tive use for the crops being grown, to determine when to
irrigate and the quantity of water to be applied. As an
example, in the Twin Falls-Burley area of Idaho, there
were no acres of land being studied for irrigation sched-
uling in 1969, whereas 10,000 acres were under irrigation
scheduling in 1970, and 40,000 acres are under the irri-
gation scheduling program during 1971. It is anticipated
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that this acreage will increase to at least 100,000 acres
during 1972, and hopefully the acreage will include all of
the area in a few years' time.
The reason this program has been successful is because the
measurements are being made by irrigation district personnel
or commercial firms, which are then supplying the needed
information to the farmers. This has saved the farmer the
effort of going out and making these same measurements
himself and then having to make decisions regarding the
timing and quantity of irrigation water to be applied.
Because of the busy schedule of the farmer, and'the diffi-
culty he might have in the initial interpretation of the
data, the problem of irrigation scheduling has met with
little success in the past. The efforts xn louho look
extremely promising and the farmers are claiming a signi-
ficant benefit from irrigation scheduling. Yields have
been increased due to the fact that water was applied
when needed rather than after the crops were stressed.
In most cases to date, there has been very little reduction
in water use, although it vrould seem likely that a decrease
in water use would occur with time as the farmer gains
more knowledge of what is actually occurring in the soil
profile. Another benefit to the farmer from this program
is that he can anticipate the dates when irrigation is to
be accomplished. This allows him to schedule irrigation
along with the other duties that must be performed on the
farm and relieves him of the responsibility of deciding
exactly when is the best time to irrigate.
Water Removal System
The water removal sub-system consists of removing surface
runoff from agricultural lands (if not captured and pumped
back on the farm) and receiving deep percolation losses
from irrigation. The surface runoff, or tailwater, from
one farm may become all or part of the water supply for
an adjacent farm, may flow back into the water delivery
system at some downstream location, or may be transported
back to the river via an open drain, either natural or
man-made. Before surface return flows reach the receiving
stream, there are essentially three alternatives for pre-
venting or minimizing the quantity of pollutants dis-
charged into the river. A bypass channel could be con-
structed to some location where the flows could be dis-
charged without returning to the river. A second alter-
native would be to store the return flows in shallow
storage reservoirs and allow the water to evaporate,
leaving behind the pollutants. Seepage must be controlled
in bypass channels or storage reservoirs; otherwise the
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groundwater may become contaminated. This second alternative
has the disadvantage that pollutants are being collected,
rather than discharged to the ocean, which may eventually
create a real disposal problem.
The third alternative for minimizing the quality degrada-
tion in the receiving stream due to surface irrigation
return flow would be to treat the return flow. Desalina-
tion processes could be used to restore the water supply
to a desired quality level, but methods for disposing of
brine wastes must be considered. If the problem is to
remove nitrates, then the results of the research program
at Firebaugh, California conducted by the Environmental
Protection Agency, U.S. Bureau of Reclamation, and Califor-
nia Dept. of Water Resources could be used. In these
studies, both algae stripping and bacterial denitrification
proved to be the least costly nitrate removal methods.
Drainage and salinity control. Waterlogging and salinity
pose a serious threat to many irrigated areas. Any
expansion upslope from existing irrigated lands becomes
a direct threat to the waterlogging of downslope areas
(11). For example, many of the fertile lands in the San
Joaquin Valley of California are now threatened by upslope
irrigation development, and some areas in the Yuma Valley
of Arizona have been rendered unproductive by irrigation
development on the Yuma Mesa. Equally dangerous threats
exist from the salt balance problem of these areas. Recir-
cuiation of water by pumping or reuse of return flows
results in a buildup of salinity. Concomitant with
increased salinity are corresponding increases in the
leaching requirement and drainage needs. Irrigation devel-
opment, including impoundment, conveyance, and application,
upsets the natural hydrologic cycle of an area. Recogni-
tion and solution of drainage and salinity problems in
such areas requires an intensive application of control
measures based on sound scientific knowledge.
For deep percolation losses, there are a few possibilities
for managing the effect of water quality degradation upon
receiving streams. In certain special situations, an
impermeable barrier placed a short distance below the root
zone would be effective in preventing moisture movement
deeper into the soil profile or subsurface strata which
might contain large amounts of natural salts. Thus, the
deep percolation losses could be collected and diverted to
the surface water removal system without being unnecessar-
ily degraded by subsurface salinity.
Tile drainage is a very effective means for removing the
less saline waters in the upper portions of the groundwater
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reservoir, thereby reducing the mass of salts returning
to the river., By using tile drainage, salts are allowed
to accumulate below the drains. This is particularly true
for soils high in natural salts. Tile drainage will not
completely remove all of the water moving below the root
zone unless the water table is lowered below the natural
groundwater outlet. Usually, some water will still move
through the groundwater reservoir and return to the surface
river, .but the quantity of such groundwater return flows
can be'reduced considerably by tile drainage. The quality
degradation to receiving streams from tile drainage out-
flow can be minimized by treating the outflow. This points
out another advantage of tile drainage. Tile drains allow
the collection of subsurface return flows into a master
drainage system for ease of control and treatment.
Institutional Influences
Irrigation return flow quality is largely a problem of
economic "externalities." The harmful deeds of one
farmer generally occur as a cost to someone else who may
be located a considerable distance from the source of the
problem. Conversely, the costs to one farmer for "cleaning
up" his return flow will accrue as benefits to downstream
water users. Thus, until the costs arid benefits for an
entire system are internalized, there is no real incentive
for the upstream polluter to make investments for enhanc-
ing water quality. Economics are important in this
problem area, but new legal and institutional frameworks
must be created to effectively deal with the problem.
One of the most dramatic courses of action that could be
taken to prevent quality degradation from irrigation
return flow would be to eliminate irrigation from areas
where high salt pickup rates occur, such as soils that are
formed from shales, or are themselves high in natural
salts. This concept may be more useful in preventing the
development of new irrigated areas, rather than eliminating
existing irrigated areas. Regulations may be required
regarding the management of phosphate fertilizers (for
areas having large quantities of surface runoff) or nitro-
gen fertilizers, or both. In some areas a regulation
requiring the .use of slow-release fertilizers may be
necessary.
Tailwater control would be advantageous for controlling
sediment. Sediment is also a problem because of plugging
of sprinkler nozzles in sprinkler irrigation systems.
Besides controlling the transport of pollutants, there
are other environmental considerations, such as mosquito
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abatement. Each farmer would be required to control tail-
water, or surface runoff, by means of lagoons or some
pumping system. A regulation could be put into effect
that would not allow surface runoff to leave the farm. A
permit system might be used to enforce this regulation.
A farmer might be able to have surface runoff, provided
the next farmer below him would be willing to accept such
surface runoff. This would overcome the problem where
some farmer's water supply is dependent upon return flows
from the farmer above. This would also relieve the prob-
lem in areas where large amounts of water are flooded
over the land and the next lower farmer receives the
surface runoff from this flooding. To change such a
system would require extensive physical changes in the
delivery and farm irrigation systems, but such costs would
frequently be comparable to costs of other control
measures.
There is a possibility that a schedule of money charges
could be applied for excessive water use. For example,
if the determination had been made as to the amount of
water really required for a crop, then this amount of
water could be delivered to the farmer for the reasonable
charge of operation-maintenance costs. If any additional
water were to be used by the farmer, which would only be
possible if he had previously developed a water right for
such water, then there would be a higher charge for the
additional amount of water beyond that required by the
crop. This might work in such a way that for the first
15% of water beyond the crop need would be charged at
perhaps double the rate of water for that needed by the
crops, whereas the next 15% might be quadruple the cost
of water needed for the crop, etc.
There must be some economic incentive for an irrigator
to control irrigation return flow. Such incentives can
be negative or positive. For example, a regulation
disallowing tailwater runoff costs the farmer additional
money without any apparent economic return, thereby
becoming a negative economic incentive. Now if this same
farmer could be shown that preventing tailwater runoff
would reduce the amount of water needed, reduce erosion,
increase crop yields, and increase the efficiency of
fertilizer use, and such benefits were greater than his
additional operating costs in preventing tailwater runoff,
then he has a positive economic incentive. Educational
programs could be highly beneficial in promoting irri-
gation return flow quality control, especially if a posi-
tive economic incentive can be shown. Showing economic
gain to the water user often requires field demonstration
projects that can be seen, rather than facts and figures
developed from a paper (desk) study.
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Our western water laws contribute substantially to the
irrigation return flow quality problems. There is no
incentive to conserve water in most of the irrigated
valleys in the West. Everyone feels that they must use
their full water right for fear of losing any portion of
the unused right. Although such attitudes frequently con-
tribute to local drainage problems, the practice persists.
Usually, the damages from this practice are passed on to
downstream water users. In Colorado, for example, a
farmer having an adequate water right, who lines his farm
ditches or otherwise conserves water, cannot use the
saved water to irrigate additional land or as a supplemental
water supply for lands having an inadequate water right.
If the same farmer had an inadequate water right for his
land and used various conservation measures to allow more
water to become available in the root zone, he benefits
from the improvements and has not jeopardized his water
right. Thus, a farmer having an adequate water right has
no, or very little, economic incentive for improving his
water management. This example points out the necessity
for changing our present incentive system.
Our basic water laws are probably satisfactory, but the
interpretation of these laws could be modified to encour-
age more efficient water use. A market place is needed
where water could be bought or sold. For example, if
each farmer could accrue some monetary benefit by conserv-
ing water, then a positive economic incentive would exist.
The water saved by one farmer could be sold or rented to
a farmer having an inadequate water supply. This way, the
water supply could be redistributed within the irrigated
valley to meet the agricultural water demands more effi-
ciently. In most irrigated valleys, there are problems of
maldistribution of the water supply, but at the same time,
there could be a net water savings. This net water savings
could be sold or rented to satisfy other water demands.
To accomplish such water transfers would require some safe-
guards that the transfer was desirable from the standpoint
of fitting into a comprehensive water resources development
plan for the basin. Also, there would need to be some
legal safeguards to prevent "black market" prices. This
could be accomplished by allowing the state the right of
condemnation in such affairs, which would also provide
economic reimbursement to the area which conserved the
water.
Irrigation scheduling is a positive economic incentive
for improving water management because of increased crop
production. This technique for improving irrigation prac-
tices has the advantage of partially overcoming the negative
aspects of western water laws. Although the irrigation
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scheduling reported to date does not cite any reduction
in total water use, this reduction will take place as
more experience is gained by the farmer regarding soil
moisture management in the root zone of his croplands.
Even so, the farmer may still wish to divert his full
water right. Again, if the farmer could receive an
economic return by being allowed to transfer the saved
water, then the improvements in irrigation water use
efficiency could be brought about at a much faster
pace.
Only a few of the irrigated valleys are operated as a
single management unit. In many valleys, several irri-
gation companies exist, with each company responsible
for water delivery to a portion of the valley. In many
cases, separate institutions exist to handle the water
removal (drainage system). Numerous examples could be
cited where 20-30 irrigation companies operate in a
single valley. In order to develop effective irrigation
return flow quality control programs, the quality degra-
dation resulting from the entire irrigated valley must
be ascertained. Then alternatives for controlling irri-
gation return flow must be developed, which will be
primarily valley-wide alternatives. Thus, there is a
real need to work with a group representing the agri-
cultural interests of the entire valley. The consolida-
tion of the separate irrigation companies into a single
entity would have many advantages to local interests in
improving agricultural development in the area, as well
as providing a single entity for more effectively bring-
ing about improved water management programs to reduce
quality degradation in receiving streams due to irri-
gation return flow.
One concept that could be used in order to manage the
irrigation return flow problem would be to require the
one degrading the quality of water to pay the cost of
treating this water. This concept might be applied on an
individual farm basis. Having the individual farmer take
care of his own problems might become extremely difficult
(if not impossible, or nearly so) for deep percolation
losses. Thus, there would be a need for a large district
to handle the costs of treating the return flows. This
would require that all return flows be collected at some
downstream point where they would then be amenable to
treatment. The degree of required treatment should diff-
erentiate between the pollutants already present in the
applied water as compared with the pollutants added due
to irrigated agriculture. The costs would then be dis-
tributed back to the individual farmers. Such a measure
would have the advantage of placing greater stress on
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water management in order to minimize deep percolation
losses and the associated costs of collection and treat-
ment.
An example of having irrigation return flows treated
would be the San Joaquin Master Drain. The costs
for this treatment could be distributed back to the far-
mers, but economically, it could be shown that everyone
in the basin gathers some benefits due to this drain.
Thus, there should possibly be a payment by everyone within
the basin for the drain. This is a real question of
economic benefits. The problem becomes one of defining
these benefits and distributing the costs.
There are a number of economic questions that could be
asked regarding the distribution of costs and benefits
resulting from irrigation return flow. For example, in the
Santa Ana Basin, who should pay the costs of treating the
contaminated groundwater supplies? If a canal is lined to
reduce seepage losses and consequent salt pickup, how
should the costs be distributed among local water users,
downstream water users, and the public, either locally,
regionally, or nationally?
One real means for improving irrigation return flow
quality, which has been pointed out a number of times, is
to improve the efficiency of water use on the farm, but
taking into account the leaching requirement for maintain-
ing a salt balance in the root zone. One of the problems
that makes this difficult is that certain farmers are more
able to return capital investment to the farm for such
operations as land leveling, ditch lining, or improved
irrigation methods, whereas the marginal farmer is not
able to return capital for farm improvements and thus
usually has poorer efficiency. In looking at any incentive
programs for improving irrigation return flow quality, it
should be taken into account that some means must be pro-
vided whereby the marginal farmer could benefit by improved
water management practices and consequent alleviation of
water quality problems. When such investments are made,
the marginal farmer probably benefits more than other
farmers. For farmers with capital, there is still a problem
if the return for such capital investments is lower than
for alternative uses of capital.
In looking at the many alternatives for controlling irri-
gation return flow quality, it becomes evident that some of
the conservation measures advocated over the past few decades
have resulted in water quality improvements. For example, such
practices as soil erosion control, canal and farm ditch
lining, improved irrigation practices, and tile drainage
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have water quality benefits. Therefore, many of these
practices should continue to be emphasized through educa-
cional and action programs.
Quality Control Programs
As alluded to previously, an irrigation return flow
quality control program is only one component in the
overall water resource planning and development of a river
basin. Thus, any control program must fit into the long-
range objectives for the basin. This also points out that
the planning for a control program should be accomplished
on a river basin basis. To date, the only control program
which has been planned on a basin-wide scale is the pro-
posed salinity control program for the Colorado River Basin.
To illustrate a control program, the following material has
been taken from the report, "Need for Controlling Salinity
of the Colorado River," which was published by the Colorado
River Board of California in August, 1970 (8).
Colorado River Basin. There are a number of sources of
salinity throughout the Colorado River Basin that could be
controlled by individual projects. The Environmental Pro-
tection Agency has identified a number of specific projects
and has conducted limited reconnaissance level investiga-
tions. The Bureau of Reclamation has completed reconaiss-
ance level studies for one project. The Type I, Comprehen-
sive Framework Studies for the Upper Colorado Region have
also identified these projects in its reports (as yet un-
published) . Salinity sources include twelve irrigated
areas and five natural sources. Five flowing wells that
together contributed 100,000 tons of salt annually to the
river have already been plugged. The mean annual tonnage
of salts reaching Hoover Dam is roughly 8 million. The
cumulative effect of these projects would accomplish a
substantial reduction in the river's salt load. It should
be emphasized that these identified projects are not con-
sidered to be the only feasible projects, and that other,
now unidentified, projects may also prove to be feasible
(8).
Salt sources subject to control are located on Figure 9,
"Proposed Salinity Control Projects." Average annual
costs, including capital, operation and maintenance costs,
are summarized in Table 8.
The twelve irrigated areas vary in size from 100,000 acres
in Uncompahgre Valley, Colorado to several small irrigated
68
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OWIN
Big Sandy Creek
Henrys Fork
River N
FLAMING GORGE DAM_
Glenwood Springs
Roaring Fork River
R A D 0
Grand Valley
Lower Gunnison
'CURECANTI DAMS
Uncompahgre River
C A F 0 R N A
ICO
O SALT LOAD REDUCTION PROJECT
C2* IRRIGATION IMPROVEMENTS
Figure 9. Proposed salinity control projects in the Colorado
River Basin
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Table 8. Estimated costs of salinity control projects (8).
Project
Salt
Removed
(Thousands
Tons/Yr)
Annual
Project
Costs a
(Thousands
Dollars)
Unit
Cost b
(Dollars/
Ton/Yr)
Irrigation Improvements c
Grand Valley 310
Lower Gunnison River 330
Price River 90
Uncompahgre River 320
Big Sandy Creek 40
Roaring Fork River 50
Upper Colorado River 80
Henrys Fork River . 40
Dirty Devil River 40
Duchesne River 270
San Rafael River 70
Ashley Creek 40
Subtotal 1,680
Stream Diversion
Paradox Valley . 180
Impoundment and Evaporation
La Verkin Springs 80
Desalination
Glenwood and Dotsero Springs 370
Blue Springs 500
Totals 2,810
Weighted Average Unit Cost
3,100
3,600
1,000
4,000
490
880
1,400
710
710
5,700
1,400
800
23,790
700
600
5,000
16,000
46,100
5,
5,
5,
00
,40
,70
6.30
6.30
8.50
8.90
8.90
8.90
10.40
10.50
11.60
3.90
7.50
13.50
32.00
12.30
Annual project costs include amortized construction, operation
and maintenance costs.
The unit costs only include costs allocated to salinity control.
Annual project costs for irrigation improvements incorporate all
costs, including those allocated to the irrigation function.
Costs allocated to salinity control projects were estimated
to be one-half of total annual project costs.
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areas in Utah and Wyoming. Measures to be used for salinity
control would include lining canals, constructing drains,
and improving irrigation efficiencies through modification
of irrigation practices. These measures would reduce return
flows and thereby decrease the quantity of water coming into
contact with highly saline groundwater and underlying mat-
erial. The degree of salt load reduction will vary from
one area to another. Therefore, a detailed investigation
is required for each irrigated valley in order to establish
the amount of salt reduction which will result from each
water management alternative. Also, the costs and benefits
must be established for each alternative. Based on studies
conducted by the Environmental Protection Agency (12), it
was estimated that the combination of these control measures
would reduce the salt contributed from approximately
600,000 irrigated acres by 1,680,000 tons annually. Average
annual costs have been estimated to be $23,800,000. The
unit cost for individual areas varies from a low of $5/ton/
year in Grand Valley, Colorado, to a high of $12/ton/year
in one small area.
In all irrigated areas salinity control works would benefit
local irrigators as well as reduce the overall dissolved
solids load. These benefits would be in yield increases
resulting from lowering of the water table (where high
water tables affect crop production), lower canal operation
and maintenance costs, and reduced fertilizer costs.
Completion of all enumerated projects would result in rem-
oval of 2.8 million tons of salt annually from the Colo-
rado River and its tributaries upstream from Hoover Dam.
Approximately 22,000 acre-feet per year would be removed
as brine and evaporated or injected into deep geological
formations. The salts removed would amount to 25 percent
of the total annual projected salt load of 11.4 million
tons at Hoover Dam in the year 2000.
Cost data on these projects from open file records of the
Environmental Protection Agency were available on an annual
cost basis; however, data from Type I, Comprehensive Frame-
work Studies and other sources enable close estimates to
be made of the capital costs of the salinity control pro-
jects. Projects located in the Upper Colorado River Basin
would have a capital cost of approximately $230 million,
and those located in the Lower Colorado River Basin would
have a capital cost of about $150 million.
About 79 percent of the salt reduction would be achieved
from sources in the Upper Basin, while the balance would
be from sources in the Lower Basin between Lee Ferry and
Imperial Dam. With all projects completed, the full
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reduction would amount to an average of 360 ppm under flow
conditions prescribed by the Colorado River Basin Compact.
Annual costs of salinity control projects divided by the
estimated maximum dependable annual virgin water supply of
the river, 14 million acre-feet/ gives a unit cost of
$3.30 per acre-foot.
Projected salinity at Hoover Dam and other major diversion
points is shown in Table 9 for the years 1980, 2000, and
2030 for conditions with and without salinity control pro-
jects. The projections shown with the projects are based
on the assumption that about half of the projects would be
completed by 1980 and the balance by 2000.
Grand Valley, Colorado. Of the total salt load reaching
Hoover Dam, 18 percent is salt pickup from Grand Valley.
In 1968, the Federal Water Pollution Control Administra-
tion (now the Environmental Protection Agency) awarded a
grant to the Grand Valley Water Purification Project, Inc.
for the "Grand Valley Salinity Control Demonstration Pro-
ject." The organization receiving the grant was a newly
organized institution with board members representing the
various irrigation companies in the valley. The purpose
of the grant was to line canals and laterals in a demon-
stration area immediately east of the city of Grand Junction
to determine the effectiveness of such lining in lowering
the water table and decreasing the salt pickup reaching the
Colorado River, which flows through the valley. The tech-
nical evaluation of the effectiveness of the lining in
accomplishing the objectives of the project was subcontracted
by the local organization to Colorado State University.
In evaluating the lining program, it was deemed necessary
to prepare water and salt budgets for the demonstration
area, as well as the entire Grand Valley. As a result,
more knowledge was gained regarding on-the-farm water
management and the subsurface flow system, as well as the
open drain system. From this knowledge, better estimates
can be prepared regarding the magnitude of the quality
problem resulting from each component of the return flow
system.
At the present time, plans are being developed on two
fronts. First of all, when the lining program evaluation
is completed in January, 1972 the demonstration area will
hopefully be used to demonstrate: (a) the benefits of irri-
gation scheduling in improving crop yields, lowering local
groundwater levels and decreasing deep percolation losses
and salt pickup on a long-term basis; and (b) the advantages
of tile drainage combined with careful on-the-farm water
management in reclaiming poor agricultural lands, increasing
crop yields and decreasing salt pickup reaching the Colorado
River.
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Table 9. Projected salinity in the Lower Colorado River with and without proposed
salinity control projects.3 (In Parts per Million) (8)
Station
(Along Colorado River)
Below Hoover Dam
At Parker Dam
At Palo Verde Dam
At Imperial Dam
At Northerly Interna-
tional Boundary
Average
1963-67
730
740
b
850
1,300°
1980
Without
Projects
830
860
910
1,070
1,350
With
Projects
790
820
860
990
1,290
2000
Without
Projects
1,050
1,110
1,190
1,340
d
With
Projects
790
830
890
1,010
d
2030
Without
Projects
1,090
1,150
1,230
1,390
d
With
Projects
810
840
910
1,030
d
Based on Upper Basin depletions as projected by the Colorado River Board for 1980 and
the U.S.B.R. for subsequent years.
5Record not available.
**
'Source: International Boundary and Water Commission.
Not estimated.
-------
The second program being planned for Grand Valley
involves a three-phase project which would evaluate and
demonstrate the effects of irrigation practices on crop
yield and salinity of irrigation return flows.
The first phase would entail studies on a small field of
30-40 acres. This intensive study area would be broken
into approximately 100 plots, each having an individual
drainage system. .A solid-set sprinkler system will be
used as the method of irrigation. Four crops - alfalfa,
barley, corn, and pasture - will be studied, with the
amount and timing of water application being varied for
the plots, as well as nitrogen fertility levels. Bare
plots will be used wherein moisture treatments are
varied. In addition, special plots will be constructed
which will allow a separation between salt pickup due to
vertical percolation through the soil as compared with
horizontal water movement along the underlying shale
beds. The quantity and chemical quality of the drainage
effluent from each plot will be monitored. Moisture
changes and chemical quality changes will be measured
in the soil profile. From these measurements, a model
can be developed which describes water and salt movement
through the soil. Since the drainage effluent from each
plot is monitored, the model can be verified. Finally,
crop yields will be measured. This phase of the program
will provide relationships between moisture -treatments
and chemical quality of drainage effluents, thereby
providing information which can be projected into a
systems analysis of an area. In turn, crop production
functions based on salinity levels will be developed.
The second phase of the program would utilize approxi-
mately 100 acres for a more extensive field demonstration
of the effects of various irrigation methods, in combin-
ation with moisture and fertilizer treatments, on crop
yield and chemical quality of irrigation return flows.
This phase would make it possible to demonstrate under
controlled conditions, solutions to farm problems in
irrigation water management. Projections of the quantity
and chemical quality of water percolating to the ground-
water table will be obtained from the model developed
under Phase I. This will necessitate the measurement of
soil moisture and chemical quality movement through the
soil profile.
The third phase of the proposed program would be the
extension of recommended practices on four to six coop-
erative demonstration farms scattered throughout Grand
Valley. These farms would be operated by their owners,
but with technical assistance provided by the project.
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The objective of this phase would be to demonstrate that
improved farm water management can produce the desired
results under farmer management, that it is practical,
and that it can be profitable for the individual as well
as for society generally. This phase is extremely impor-
tant in obtaining farmer acceptance. Also, the feedback
from the farmers is necessary so that adjustments may be
made in design, operating procedures, and educational
methods.
In each of the three phases, tours, seminars, publications
and the news media (Grand Junction has both a local news-
paper and a television station) would be used extensively
to accomplish the demonstration objectives. The success
of the demonstration program depends on the effectiveness
with which the results are disseminated and the degree to
which they are accepted and transposed into action.
The foregoing serves to illustrate one example of an
approach to salinity control by improving farm water
management and cultural practices in a valley area. Similar
extensive investigations in other problem areas should be
the basis for developing and initiating action programs
designed to alleviate water quality problems arising from
irrigated areas. The example also illustrates the broad
spectrum approach required to formulate solutions to our
present problems and also provide the necessary incentives
for farmer acceptance of proven control measures. Since
most of the water quality problems are area-wide in scope,
the solutions to those problems must be conceived and
executed on an area-wide basis.
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SECTION VII
RESEARCH NEEDS
There are a multitude of research needs regarding irri-
gation return flow quality. The wide variety of research
needs have been described in the Utah State University
Foundation report, "Characteristics and Pollution Prob-
lems of Irrigation Return Flow" (30). The research needs
described below are an attempt to list the specific res-
earch needs required to carry out an effective irrigation
return flow quality control program. The fact that a
number of important research needs are not described
below only means that the priority of such needs is con-
sidered less important from the standpoint of immediate
needs for getting control programs underway. The order
in which research needs are discussed does not imply
priority, since this may vary with regions and the diff-
erence of major problems in different irrigated areas.
Irrigation Practices
There are a number of irrigation methods now available
but only surface irrigation and sprinkler irrigation are
commonly used. Consequently, much of our present-day
knowledge of irrigation has been derived from these
methods. For surface irrigation, there is not a great
need for additional research, but there is a real need
to put into practice the technology now available. One
of the criteria in designing a surface irrigation system
is to minimize tailwater runoff, which is compatible with
quality control of surface return flow. In much of the
recommended research cited below, surface irrigation will
frequently be used as the method of water application.
In such cases, the experimental design should include
studies of tailwater runoff and consequent quality deg-
radation by sediments, phosphates, salts, fertilizers,
and pesticides. In addition, experimental designs should
incorporate irrigation waters of varying salinity. Efforts
to automate surface irrigation systems should be encouraged.
The primary research need regarding sprinkler irrigation con-
cerns quality degradation by sediments and the pollutants
adsorbed on soil particles. Sediment erosion is partic-
ularly prevalent with high application rate sprinkler
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systems such as the center-pivot sprinkler. Design cri-
teria which incorporate sediment erosion control are needed
for sprinkler systems.
Subsurface application and drip irrigation are two methods
which provide considerable control of water application
timing, rates, and amount. Because of their potential for
achieving high irrigation efficiencies, and increased
nutrient efficiencies, these irrigation methods should be
incorporated in many of the experimental designs. For
example, the research needs cited below under "Soil-Plant-
Salinity Relationships" could be included in some of the
evaluations regarding the effectiveness of these two
irrigation methods in an irrigation return flow quality
control program. Also, evaluations of these irrigation
methods should include water supplies covering a wide
range of salinity concentrations as well as a range of
soil types. In addition, the efficiency of fertilizer use
should be included in the studies. Another important
aspect of the experimental design would be the inclusion
of information on the quantity and quality of flow which
moves below the root zone. From this research, design
criteria should be developed for each irrigation method
which are oriented towards both the quantity and quality
aspects of irrigation return flow in addition to their
effects on crop yields.
Soil-Plant-Salinity Relationships
In assessing the effects of increasing the salinity of
water supplies, it becomes essential that crop damage
functions be determined. At the present time, we have
only a fair knowledge of the salinity effects upon crop
growth. We are also weak in our knowledge of crop yield
functions due to water quantity, alone. Thus, experi-
mental designs should incorporate both water quantity and
quality as variables in crop production and crop damage
functions. Such experiments could be incorporated in
studies regarding the prediction of subsurface return
flow, which are discussed later in this section.
The salt tolerance of various crops under a variety of
on-the-farm water management practices should be inves-
tigated. The studies should include short-term effects
due to salinity, such as the ability of a plant to with-
stand high salinity concentrations for short durations.
Again, the salinity of the irrigation water supply should
be varied. A portion of these studies could be included
in the evaluation of subsurface application and drip
irrigation, which are described above.
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There is a tremendous potential for using slow-release
fertilizers in order to maximize plant-use efficiency and
minimize the quantity of fertilizer constitutents appear-
ing in irrigation return flow. There is still a need to
develop satisfactory slow-release fertilizers which will
release nutrients at a rate to match plant needs. The use
of slow-release fertilizers should be incorporated in many
of the experimental designs on irrigation practices. In
addition, demonstration projects using such fertilizers
could be easily accomplished in most areas where nutrients
in irrigation return flow are a problem.
The advantages of subsurface application and drip irriga-
tion in reducing soil water evaporation should be delineated,
Surface mulches and/or reduced tillage to reduce soil water
evaporation could also be incorporated in demonstration pro-
jects.
After accomplishing much of the research described above,
there should be a program to monitor the long-term effects
of recommended irrigation and agronomic practices. Rather
than just using crop yields as a measure of success, the
monitoring must include water quantity and quality changes
taking place in the root zone, as well as the quantity and
quality changes in moisture movement below the root zone.
Leaching
Better techniques for determining optimum leaching require-
ments are needed. The basic problem is developing a know-
ledge of transport phenomena on a field basis, which can
then be incorporated into the development of criteria for
determining leaching requirements. The transport phenomena
will involve a more detailed analysis of leaching based
upon an ionic evaluation of salt movement through the soil.
For example, certain salts, such as gypsum, are not really
deleterious to plant growth. Consequently, if these salts
are precipitated within the soil, they present no real prob-
lem. A more difficult problem results when salts such as
sodium are not being leached from the root zone. Therefore,
criteria for leaching should take into account the type of
salts being leached, as well as total dissolved solids, as
a means of evaluating leaching requirements and leaching
efficiencies.
Much of our present knowledge regarding leaching require-
ments and the movement of water and salts in the soil has
been developed in laboratory-packed columns. The results
obtained under these artificial conditions can be unrealistic
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when compared with undistrubed soil profiles in actual
field conditions. There is a need to translate this type
of information to actual field conditions, and additional
studies in this area are required. The relationships
between soil physical characteristics and quality of the
water applied must be evaluated to determine actual leach-
ing requirements in the real world.
Prediction of Subsurface Return Flow
The greatest single technological need at the present time
for the subject area of irrigation return flow quality is
the development of prediction techniques which will des-
cribe the quantity and quality of subsurface return flow.
The real critical problem is defining the variability in
subsurface return flows for large areas, such as an irri-
gated valley or a large portion of the valley.
In order to produce applicable research results, general
models should be developed to describe subsurface return
flow which can be adapted to numerous areas. Conceptual
models must be developed and the sensitivity of various
parameters which will be used in the models must be deter-
mined. In studying large areas, a balance must be reached
between the sophistication of the model and the cost of
collecting field data. There are still a number of limi-
tations in our ability to make accurate field measurements.
These models must be capable of predicting changes in the
quantity and quality of subsurface return flows under a
variety of water management alternatives. To fully eval-
uate chemical quality changes, the models should be capable
of handling precipitation and exchange reactions which take
place as the moisture moves through the soil profile. These
transformations alter the ionic balance of the chemical
constituents in solution and are very important in describ-
ing the quality of irrigation return flow.
Lysimeter or controlled field plot studies will be required
to develop the necessary models for describing subsurface
return flow. After such models have been developed, they
should be verified on large areas such as an entire irri-
gated valley, or a major portion of an irrigated valley.
Cultural Practices
Irrigated areas containing tight soils having low permea-
bility and receiving highly saline water supplies, which
are characteristics of many irrigated valleys located
at the lower end of a river system, would benefit
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considerably from additional research efforts regarding
soil management practices such as deep tillage or other
mechanical techniques. Also, demonstration of mulching and
reduced tillage to control soil water evaporation would be
beneficial. Again, experimental designs for studying
cultural practices could be combined with some of the res-
earch needs described below.
Irrigation Scheduling
The practice of optimum irrigation scheduling has only come
about in the last few years and is presently practiced in
only a few limited areas of the West. Irrigation scheduling
has a tremendous potential for improving water use effic-
iency, with consequent improvements in irrigation return
flow quality due to decreased tailwater runoff and decreased
salt pickup in subsurface return flows. Because of inherent
advantages to the farmer in increased crop production, this
practice could overcome some of the institutional constraints
in bringing about improved water management. Consequently,
irrigation scheduling demonstrations could prove to be one
of the best tools at our disposal for controlling irrigation
return flow quality. Therefore, such demonstrations should
be undertaken in the irrigated valleys of the West having
major water quality problems due to irrigation return flow.
Such studies must be more comprehensive than irrigation
scheduling investigations to date, since the effect on the
quantity and quality of subsurface return flows must be
evaluated.
Pump-Back Systems
Pump-back systems for tailwater control are presently
being used in certain water-short locations. Generalized
design criteria should be developed for these systems which
take into account sediment removal, farm salt balance,
necessity for pond lining, treatment possibilities, and
other environmental problems such as odors, insects, mos-
quitoes, etc. The effects of the recirculation of tail-
water on the quality of the applied irrigation water need
to be evaluated so that recommendations can be formulated
for optimum design and operation criteria.
Treatment
Studies are needed to evaluate the rates of denitrification
with various environments under field conditions. The
studies should include management practices to control
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nitrogen in the root zone. The judicious selection of soil
types (i.e., those which have high denitrification poten-
tials in the soil profile below the root zone), shallow
water tables, hard pans, shallow tile drains, etc., are items
which should be investigated as to conditions which might
produce favorable conditions for bacterial denitrification.
Alternatives for accomplishing denitrification in tile drains,
or possibly open drains, should be investigated. At least
partial denitrification may be accomplished in the drainage
system.
The research program at Firebaugh, California provided
information on nitrate reduction by algae stripping and
bacterial denitrification. The results of these studies
should be utilized in demonstration projects. This will also
allow the costs and benefits of treatment to be compared
with other alternatives for controlling water quality deg-
radation from irrigation return flow.
Economic Evaluation
There is an ever-increasing need to delineate the wide
variety of benefits and damages that occur as a result of
water quality changes. In assessing costs and benefits
associated with irrigation return flow, the research cited
above regarding the development of crop production and
crop damage functions due to water quality would provide
necessary information for making more accurate economic
evaluations, and consequently would also benefit the
decision-making process. Along this same line, cost studies
are needed for various treatment processes which may be
employed to remove nutrients, sediments, and/or salts.
Rather than just thinking in terms of crop production, or
crop damage, resulting from water quality degradation,
another important concept in economic studies should be the
decreased utility of return flows to downstream water users
due to deteriorating water quality.
Economic studies are needed which point out the local, state,
regional, and national benefits which would accrue from the
implementation, either in an irrigated valley or an entire
river basin, of an irrigation return flow control program.
For example, a control measure implemented in a particular
valley has certain benefits to the local area, including
non-agricultural sectors. The degree of quality improvement
achieved by this control measure will have a number of bene-
fits to downstream water users. Also, benefits may accrue
to upstream users resulting from water exchanges or because
of institutional arrangements (e.g., if standards fix the
allowable water quality leaving a region, then the
82
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improvement of irrigation return flow quality in an exist-
ing area may be required before new agricultural lands can
be placed under irrigation within the region).
Institutional Changes Needed
The greatest institutional need for improving irrigation
return flow quality is a change in the interpretation of
western water laws to provide incentives for efficient
water use. First of all, a study should be undertaken to
delineate the changes in water law interpretation required
to provide efficient water use incentives. Next, the
procedures required to have such interpretations included
in the water law structure of each state should be deter-
mined. Then, as a minimum, such changes in interpretation
should be attempted in the states having major quality
problems resulting from irrigation return flow. This would
be particularly beneficial in a state where a control pro-
gram would soon be getting underway.
Studies should be undertaken which would evaluate the possi-
bilities of incorporating water quality into a water right
(e.g., California Porter-Cologne Act). For the most part,
our water rights pertain only to the quantity of water.
Since the quality of water can be a limitation upon its
use, both quantity and quality should be specified in a
water right. A variable water right based on quality may
be feasible. For example, a greater quantity of low quality
water will be required to produce the same results that can
be obtained with a lesser amount of high quality water.
The effects of placing certain regulations upon an area in
order to control irrigation return flow quality should be
evaluated. For example, regulations regarding the use of
fertilizers should be studied. Such studies must consider
requirements for administering fertilizer regulations, as
well as gaining knowledge on local and downstream benefits,
along with local damages. Other regulations that need
evaluation are limiting water use (e.g., use of economic
charges to control water use), tailwater controls, and
effluent standards for drainage systems which incorporate
both quantity and quality.
Potential Control Measures
Area-wide investigations will be required in some areas to
define the control measures that are needed and feasible to
improve downstream water quality. The studies in the
Colorado River Basin described in the previous section
83
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(Section VI) are examples of the types required. These
studies pinpoint the sources of salinity, nutrients, and
other pollutants, and provide background information to
support the most feasible approaches to control measures.
Once the sources of pollutants are defined, more detailed
studies will be required to specify how those sources may
best be controlled. Such broad investigations will require
the cooperative efforts of several research groups under
the guidance of a central advisory committee representing
local, state, and federal interests.
Local acceptance of proposed control measures will require
demonstration projects and an extensive educational pro-
gram to demonstrate local, regional, and interstate bene-
fits to be gained. Considerations in implementing control
programs are discussed more fully in the following section.
84
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SECTION VIII
IMPLEMENTING CONTROL PROGRAMS
The attempt herein has been to delineate research efforts
required to support an irrigation return flow quality
control program. In order to spell out needed research,
the possibilities for control, and consequently a control
program(s), must be defined. In order to show the role
of research in supporting a control program, the follow-
ing discussion on implementing control programs is pres-
ented .
The initial step required in establishing any type of
control program is to delineate the major types of irri-
gation return flow quality problems and where they occur.
At the present time, the major problem areas are the
Colorado River Basin, Rio Grande Basin, and San Joaquin
Valley, with smaller areas like Yakima Valley and Santa
Ana Basin also having critical problems.
After defining the major problem areas, the magnitude of
the problem and potential solutions must be defined. Of
the three major problem areas cited above, only the Colo-
rado River Baisn has been studied on a basin-wide scale
in order to develop potential solutions and costs for con-
trolling salinity within the basin. The San Joaquin
Valley has been extensively studied for purposes of agri-
cultural development, but additional efforts on evaluat-
ing return flows are required because of the magnitude of
the potential problems. There is a very strong need to
undertake a study of the Rio Grande Basin to define the
magnitude of the potential problems within the basin, as
well as potential solutions, including costs, of control-
ling quality degradation. This reconnaissance study
would be very similar to the type of study recently
reported for the Colorado River Basin. (8,12)
Once the major problem areas within a river basin have been
delineated, it then becomes necessary to conduct more
detailed investigations, particularly for the areas creat-
ing the greatest quality degradation. A major problem
area will likely be an irrigated valley such as Grand Valley
in the Upper Colorado River Basin. At this point, it
becomes necessary to investigate the water delivery system,
on-the-farm water management, and the water removal system
85
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in order to define accurately the magnitude of control
possible for a number of water management alternatives.
At this point, many of the research needs cited in the
previous section play an important role.
The two major areas of research which would facilitate
the development of control programs for an area are: (a)
prediction of subsurface return flow; and (b) economic
evaluation of the effects of alternative control measures.
The inability at the present time to predict the quantity
and quality of subsurface return flow is a real hindrance
to accurately defining return flow quality changes which
will result from imposing changes upon the water delivery
system or improving on-the-farm water management. To
overcome this lack of technology, it would appear advan-
tageous to have a coordinated research effort utilizing
recognized researchers in this area of endeavor. For
instance, research projects could be initiated to study
subsurface return flow in the Colorado River Basin and
Rio Grande River Basin, while expanded studies are needed
in the San Joaquin Valley. The projects could be coor-
dinated by a committee consisting of recognized research
leaders and state and federal personnel.
The major reason for conducting studies on subsurface
return flow in each of the three major problem areas is so
that the study area can be incorporated into the control
program for the region. The same study area can be used
for research and demonstration projects regarding irri-
gation practices, cultural practices, soil-plant-salinity
relationships, leaching, irrigation scheduling, and treat-
ment. Thus, there is considerable versatility in accom-
plishing many of the research needs. These study areas
would supply the specific information needed for irrigation
return flow quality control programs in that region, as
well as satisfy certain general research needs applicable
to other regions.
The second major area of needed activity, economic evalu-
ation, could be accomplished in much the same manner as
described above in developing prediction techniques for
subsurface return flow. An economic evaluation could be
undertaken for each of the three major problem areas.
Again, an advisory committee could be used to conceptual-
ize the economic models and formulate the investigations.
An economic study of the benefits and damages that will
result from various control measures is necessary to the
control program for each major problem area. Each study
can contribute to the development of general economic
criteria, which can then be used in evaluating control
86
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programs in new areas, thereby reducing the time and
effort required for an economic evaluation of a new pro-
gram area.
The institutional research needs could be undertaken
initially without being associated with any particular
study areas. The problem of instituting changes in the
interpretation of western water laws primarily requires
interaction with the agency in each state which adminis-
ters water rights. Later, it would be desirable to
define the benefits and costs in particular study areas
which would result from these new interpretations.
One benefit arising from research programs conducted in
the major problem areas will be the focus and attention
which will be given to the problem(s). Research and
associated personnel become heavily involved in the over-
all problems, which are then communicated to local, state,
regional, and federal personnel responsible for correcting
the problems. For this phase of the program to be success-
ful, it becomes essential that a strong interaction exist
between the research personnel and local and action agency
personnel. First of all, there must be a strong inter-
action among local, state, and federal personnel in the
investigations which lead to the delineation of a control
program. The role of research is to supply some of the
information necessary for developing the control program.
Another benefit that might result from the research program
will be the possibility of training researchers and investi-
gators in the general field of irrigated agriculture.
Although there are a large number of professional people
working in the field of agriculture, the number of such
personnel oriented towards solving agricultural pollution
problems is small. Consequently, training programs aimed
at orienting a wide spectrum of professional personnel
which might be associated with implementing control pro-
grams would be highly beneficial. Also, since the problems
of irrigation return flow quality are world-wide, many
countries would benefit by having personnel from their
country receive training at the major study areas. The
general technological concepts of control would essen-
tially be the same anywhere in the world, but the insti-
tutional influences will vary considerably from one portion
of the world'to another.
Finally, once a specific control program has been developed
for a particular area, the question arises as to the funding
of the control measures. Can existing institutions be
utilized, or should new institutions be developed? Since
87
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benefits derived from control programs are not restricted
locally, public support may be required to implement speci-
fic control measures.
The concept of effluent standards is presently being
explored with regard to certain industrial waste effluents.
It is not beyond the realm of possibility that similar
approaches may be considered for agricultural wastes.
Such standards would have to be concerned with pollutant
loading, not just the concentrating effects. Voluntary
action programs, while there is still time, would be much
better for all concerned. Agricultural scientists should
be aware of this and start considering the consequences of
such action. Studies designed to solve a problem before
enforcement action becomes necessary would be most desir-
able. It has already been suggested that a date for defin-
ite improvement in the quality of irrigation return flows
be set. The urgency for immediate action is apparent.
Resource Requirements
Some rough estimates can be made for implementing the above
mentioned studies. For example, a study involving changes
in water rights interpretations for the 17 western states
is estimated to have a. total cost of $100,000, which could
be distributed evenly between fiscal years 1973 and 1974.
A reconnaissance investigation of the Rio Grande Basin is
needed to define a salinity control program. The cost of
such an investigation is estimated at $250,000 per year
for three years, say fiscal years 1973, 1974, and 1975.
In addition, a research and demonstration site for studying
irrigation methods, leaching, and subsurface return flows
should be established, either in Mesilla Valley, El Paso
Valley, or the Lower Rio Grande Basin. The costs for
establishing such a site would be $400,000 the first year
due to needed facilities, and $250,000 each succeeding
year. Studies of soil-plant-salinity relationships and
cultural practices should be undertaken in the Lower Rio
Grande Basin at an annual estimated cost of $100,000. The
economic evaluation studies should get underway the second
year at an annual cost of $75,000. Also, a demonstration
project involving irrigation scheduling, with roughly an
annual cost of $100,000, should be underway the second
year (fiscal year 1974).
In both the Colorado River Basin and San Joaquin Valley,
the cost of establishing a research and demonstration site
for investigating irrigation methods, leaching, and sub-
88
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subsurface return flows would be roughly $400,000 the first
year and $250,000 each subsequent year. Economic studies
costing $75/000 annually, and irrigation scheduling demon-
strations costing $100,000 annually, should be initiated the
second year. Additional studies on soil-plant-salinity
relationships and cultural practices should be encouraged
in the Lower Colorado River Basin, with an estimated
annual cost of $50,000.
The uniqueness of Yakima Valley, with water quality problems
resulting from sediment erosion, should be utilized to
develop guidelines for irrigation return flow quality con-
trol in areas subject to sediment erosion. Approximately
$150,000 per year could be required to develop these guide-
lines.
If the above cost estimates are summarized, the total
research and demonstration expenditures would amount to the
totals tabulated on the following page.
89
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Legal Investigations
Rio Grande Basin
Reconnaissance Investi-
gation
Research & Dem Site
Irrigation Scheduling
Economic Evaluation
Soil-Plant-Salinity &
Cultural Practices
Colorado River Basin
Research & Dem Site
Irrigation Scheduling
Economic Evaluation
Soil-Plant-Salinity &
Cultural Practices
San Joaquin Valley
Research & Dem Site
Irrigation Scheduling
Economic Evaluation
Yakima Valley
TOTALS (in $1,000)
FY 73
($1,000)
50
250
400
100
FY 74
($1,000)
50
250
250
100
75
100
FY 75
($1,000)
FY 76
($1,000)
250
250
100
75
100
250
100
75
100
400
50
250
100
75
50
250
100
75
50
250
100
75
50
400
150
1,800
250
100
75
150
1,875
250
100
75
150
250
100
75
150
1,825
1,575
The rate at which resources, both professional manpower and
funds, are made available to the program will determine the
extent to which program objectives can be accomplished. In
order to make significant inroads toward control programs,
an increased level of resources will be required.
90
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SECTION IX
ACKNOWLEDGMENTS
Much of the material reported herein was gathered by the
authors, Dr. James P. Law, Jr., Environmental Protection
Agency and Gaylord V. Skogerboe, Colorado State University,
while visiting a number of western institutions during
May of 1971. These visitations proved to be extremely
fruitful in defining the major problem areas in irrigation
return flow quality, formulating potential solutions to
the problems, and listing research needs.
The authors are indeed appreciative of the time given by
the personnel listed below, both in meeting with the
authors and also in reviewing the manuscript.
UTAH STATE UNIVERSITY
Name Title Department
A.A. Bishop Prof & Head Agr & Irr Engrg
R.J. Hanks Prof Soils & Meteorology
Larry King Assoc Prof Agr & Irr Engrg
Howard B. Peterson Prof Agr & Irr Engrg
SNAKE RIVER CONSERVATION RESEARCH CENTER
AGRICULTURAL RESEARCH SERVICE
Name Title
James A. Bondurant Agr Engr
Melvin Brown Soil Scientist
David L. Carter Research Soil Sci
Marvin E. Jensen Director
Jay Smith Soil Scientist
WASHINGTON STATE UNIVERSITY
Name Title Department
Bobby Carlile Soil Scientist Agronomy & Soils
Keith 0. Eggleston Asst Agr Engr Agr Engrg
91
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Name
Brian McNeal
Charles Mueller
David Schuy
Norman K. Whittlesey
Title
Assoc Prof
Asst Prof
Asst to the Dir,
Assoc Prof
Department
Agronomy & Soils
Agr Engrg
Water Res Center
Agr Econ
ENVIRONMENTAL PROTECTION AGENCY
PACIFIC NORTHWEST REGIONAL OFFICE
Name
William D. Clothier
C. E. Veirs
Title
Research & Monitoring
Program Representative
Regional Specialist for
Irr & Land Management
Name
Louis A. Beck
CALIFORNIA DEPT. OF WATER RESOURCES
Title
Senior Sanitary Engr
UNIVERSITY OF CALIFORNIA, DAVIS
Name
R. S. Ayers
J. W. Biggar
L. J. Booher
Raymond Fleck
J. N. Luthin
R. J. Miller
D. R. Nielsen
Akin Orhun
Verne Scott
Kenneth K. Tanji
Title
Ext Soil & Water
Prof
Ext Irrigationist
Assoc Res Chemist
Chairman
Assoc Water Sci
Prof
Grad Student
Prof .
Lecturer
Department
Spec
Water Sci & Engrg
Environmental Tox
Water Sci & Engrg
Water Sci & Engrg
Water Sci & Engrg
Civil Engrg
Water Sci & Engrg
Water Sci & Engrg
Name
R. L. Branson
Andrew Chang
Thorn Checker
UNIVERSITY OF CALIFORNIA, RIVERSIDE
Title Department
Ext Soil Spec
Assist Ag Engr
Assoc Prof
Soil Sci & Ag Engrg
Soil Sci & Ag Engrg
Econ
92
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Name
N. T. Coleman
S. Davis
W. J. Farmer
Dennis D. Focht
John Letey
R. Luebs
A. W. Marsh
Russell L. Perry
Parker F. Pratt
W. F. Spencer
Lewis H. Stolzy
Title
Prof
Ag Engr
Asst Prof
Asst Prof
Prof
Soil Scientist
Ext Irrig Spec
Prof
Chairman
Soil Scientist
Prof
Department
Soil
Soil
Soil
Soil
Soil
Soil
Soil
Soil
Soil
Soil
Soil
Sci a
Sci &
Sci &
Sci &
Sci &
Sci &
Sci &
Sci &
Sci &
Sci
Sci
Ag Engrg
Ag Engrg,USDA
Ag Engrg
Ag Engrg
Ag Engrg
Ag Engrg,USDA
Ag Engrg
Ag Engrg
Ag Engrg
Ag Engrg,USDA
Name
J. D. Rhoades
U.S. SALINITY LABORATORY, SWCRD
AGRICULTURAL RESEARCH SERVICE, USDA
Riverside, California
Title
Research Soil Scientist
SOUTHWESTERN IRRIGATION FIELD STATION
AGRICULTURAL RESEARCH SERVICE
Name
A. J. MacKenzie
Lyman S. Willardson
Title
Director
Agr Engr
IMPERIAL IRRIGATION DISTRICT
Name
J. Melvin Sheldon
Title
Manager
Department
Water
Name
G. R. Dutt
Wallace H. Fuller
A. W. Warrick
UNIVERSITY OF ARIZONA
Title Department
Prof
Head
Assoc Prof
Ag Chem & Soils
Soil Physics
-------
NEW MEXICO STATE UNIVERSITY
Name Title Department
J. W. Clark Director Water Resources
Research Institute
Eldon G. Hanson Head Ag Engrg
John W. Hernandez Prof Civil Engrg
G. A. O'Connor Asst Prof Agronomy
P. G. Wierenga Asst Prof Agronomy
UNIVERSITY OF NEBRASKA
Name Title Department
W. E. Splinter Prof & Head Agr Engrg
Paul Fischbach Prof Agr Engrg
Deon Axthelm Prof Agr Engrg
94
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SECTION X
REFERENCES
1. Agricultural Research Service, Soil and Water Conserva-
tion Division, "Impact of Irrigation on Salinity of
Surface Waters," Report submitted to the Federal Water
Pollution Control Administration, USDI, Washington,
D.C. (September, 1967).
2. Bain, R. C., Jr., and Marlar, J. T., "Water Quality
Control Problems in Inland Sinks," Water Quality Manage-
ment Problems in Arid Regions, Report 13030 DYY 6/69,
Edited by James P. Law, Jr. and Jack L. Witherow,
Robert S. Kerr Water Research Center, Federal Water Qual-
ity Administration, U.S. Dept. of the Interior, Ada,
Oklahoma (October, 1970).
3. Blevins, R. L., Cook, D., Phillips, S. H., and Phillips,
R. E., "Influence of No-tillage on Soil Moisture,"
Agronomy Journal, Vol. 93, No. 4, pp 593-596 (1971).
4. Bower, C. A., "Irrigation Salinity and the World Food
Problem," Presented before a joint meeting of the Crop
Science Society of America and Soil Science Society of
America, August 22 at Stillwater, Oklahoma (1966).
5. Bower, C. A., Spencer, J. R., and Weeks, L. 0., "Salt
and Water Balance, Coachella Valley, California,"
Journal of the Irrigation and Drainage Division, ASCE,
Vol. 95, No. IR1, pp 55-63 (March, 1969).
6. Carter, D. L., Bondurant, J. A., and Robbins, C. W.,
"Water-Soluble N03_ Nitrogen, P04_ Phosphorus, and
Total Salt Balances on a Large Irrigation Tract,"
Soil Science Society of America Proceedings, Vol. 35,
No. 2, pp 331-335 (March-April, 1971).
7. Casbeer, Thomas J., and Trock, Warren L., "A study of
Institutional Factors Affecting Water Resource Develop-
ment in the Lower Rio Grande Valley, Texas," Texas A&M
University, Water Resources Center, Tech. Report No. 21.,
College Station, Texas (September, 1969).
95
-------
8. Colorado River Board of California, "Need for Controlling
Salinity of the Colorado River/" Report submitted by the
staff of the Colorado River Board of California to the
members of the Board, Sacramento, California (August, 1970).
9. Committee on Pollution, National Academy of Sciences-
National Research Council, "Waste Management and Control,"
Publication 1400, Report submitted to the Federal Council
for Science and Technology, Washington, D.C. (1966).
10. Davenport, D. C., Hagan, R. M., and Martin, P. E.,
"Antitranspirants Research and Its Possible Application
in Hydrology," Water Resources Research, Vol. 5, No. 3,
pp 735-743 (1969).
11. Donnan, W. W., and Houston, C. E., "Drainage Related to
Irrigation Management," In Irrigation of Agricultural
Lands, ASA Monograph No. 11, Madison, Wisconsin. Chapt. 50,
pp 974-987 (1967).
12. Environmental Protection Agency, "Summary Report," The
Mineral Quality Problem in the Colorado River Basin,
Regions VIII and IX (1971).
13. Faulkner, L. R.,. and Bolander, W. J., "Agriculturally-
Polluted Irrigation Water as a Source of Plant-Parasitic
Nematode Infestation," Journal of Nematology, Vol. 2,
No. 4, pp 368-374 (October, 1970).
14. Federal Water Pollution Control Act (PL 84-660) as
amended by Amendments of 1961 (PL 87-88), the Water
Quality Act of 1965 (89-234) , and the Clean Water Restor-
ation Act of 1966 (PL 89-753), Section 1 (a).
15. Jensen, Marvin E., "Scheduling Irrigations with Compu-
ters ," Journal of Soil and Water Conservation, Vol. 24,
No. 5, pp 193-195 (Sept.-Oct., 1969).
16. Jensen, M. E., Robb, C. H., and Franzoy, E. C., "Sched-
uling Irrigations Using Climate-Crop-Soil Data,"
Journal of the Irrigation and -Drainage Division, ASCE,
Vol. 96, No. IR1, pp 25-38 (March, 1970).
17. Jensen, M. E., Swarner, L. R., and Phelan, J. T.,
"Improving Irrigation Efficiencies," In Irrigation of
Agricultural Lands, ASA Monograph No. 11, Madison,
Wisconsin. Chapt. 61, pp 1120-1142 (1967).
96
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18. Law, J. P., Jr., "The Effect of Fatty Alcohol and a
Nonionic Surfactant on Soil Moisture Evaporation in a
Controlled Environment," Soil Science Society of
America Proceedings, Vol. 28, No. 5, pp 695-699 (1964).
19. Moser, Theodore H., "Drainage by Pumped Wells in
Wellton-Mohawk District," Journal of the Irrigation and
Drainage Division, ASCE, Vol. 93, No. IRS, pp 199-208
(Sept., 1967) .
20. National Technical Advisory Committee, FWPCA, "Agricul-
tural Uses," Water Quality Criteria, U.S. Govt. Printing
Office, Washington, D.C. (1968).
21. Pacific Northwest River Basins Commission, "Irrigation,"
Columbia-North Pacific Region Comprehensive Framework
Study, Appendix IX, Vancouver, Washington (February, 1971)
22. Pavelis, George A., "Regional Irrigation Trends and
Projective Growth Functions," Draft Report by Water
Resources Branch, Natural Resource Economics Division,
Economic Research Service, USDA, Washington, D.C.
(December, 1967).
23. Pillsbury, Arthur P., and Johnston, William F., "Tile
Drainage in the San Joaquin Valley of California,"
University of California Water Resources Center, Pub.
No. 97, Los Angeles (1965).
24. Robins, J. S., "Reducing Irrigation Requirements," In
Irrigation of Agricultural Lands, ASA Monograph No. 11,
Madison, Wisconsin. Chapt. 62, pp 1143-1158 (1967).
25. Rohn, Arthur H., "Prehistoric Soil and Water Conserva-
tion on Capin Mesa, Southwestern Colorado," American
Antiquity, 28, No. 4, pp 441-455 (1963).
26. State of California, The Resources Agency, Department
of Water Resources, "Waste Water Quality, Treatment, and
Disposal," San Joaquin Valley Drainage Inyesjbigajbioji,
Bull. No. 127, Appendix D, Sacramento, California (April,
1969) .
27. Sylvester, Robert O., and Seabloom, Robert W., "Quality
and Significance of Irrigation Return Flow," Journal
of the Irrigation and Drainage Division, ASCE, Vol. 89,
No. IRS, pp 1-27 (Sept., 1963).
97
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28. U.S. Bureau of Census. 1961. U.S. Census of Agricul-
ture: 1959.
29. U.S. Irrigated Acreage, World Irrigation/ (Aug.-Sept.,
1970).
30. Utah State University Foundation, Characteristics and
Pollution Problems of Irrigation Return Flow, EPA
(FWQA), Robert S. Kerr Water Research Center, Ada,
Oklahoma (1969).
31. Wilcox, Lloyd V., "Salinity Caused by Irrigation,"
Journal of the American Water Works Association, Vol.
54, No. 2, pp 217-222 (February, 1962).
98
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SELECTED WATER i. Report NO.
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
2. 3. Accession No.
w
RESEARCH NEEDS FOR IRRIGATION RETURN 5" ReponDate
FLOW QUALITY CONTROL *•
8. Performing Organization
, . . - . Report No.
7. Author(s) *
Skogerboe, G.V., and Law, J.P., Jr. w ProJ€ctNo_
9. Organization
Colorado State University
/. Contract/Grant No.
- - -*
Fort Collins, Colorado
Agricultural Engineering Dept. ' 13. Type ofReport and
Period Covered
12. Sponsoring Organization
15. Supplementary Notes,
Report 13030 11/71, Environmental Protection Agency, Wash., B.C.
1971 98p, 9 fig, 9 tab, 31 ref
16. Abstract
There are a multitude of research needs regarding irrigation
return flow quality, but only the specific research need's
required to undertake an effective control program are des-
cribed. These research needs include irrigation practices,
soil-plant-salinity relationships, leaching requirements,
prediction of subsurface return flow, cultural practices,
irrigation scheduling, treatment of return flows, economic
evaluations, and institutional control methods.(Skogerboe-CSU)
17a. Descriptors
*Water pollution effects, *Water pollution sources, *Water
quality control, fertilizers, irrigation water, nematodes,
nitrates, phosphates, salinity
17b. Identifiers
*Return Flow, Irrigated Land, Irrigated Systems
lie. COWRR Field & Group
05G
18. Availability 19. Security Class.
(Report)
20. Security Class.
(Page)
21. No. of Send To:
Pages
Priff WATER RESOURCES SCIENTIFIC INFORMATION CENTER
* fftCC i i e- 1-lC-DADTIlJCrWT i~»C" T LJ CT IMTtrDir^ia
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON. D. C. 20240
Abstractor Qaylord V. Skogerboe \institution Colorado State University
WRSIC 102 (REV JUNE 1971) ftU.S. GOVERNMENT PRINTING OFFICE: 1972 484-484/156 1-3
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