WATER POLLUTION CONTROL RESEARCH SERIES • 13030 GJS \2I
National Irrigation Return Flow
esearch and Development Program
U.S ENVIRONMENTAL PROTECTION AGENCY
-------
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 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.
-------
NATIONAL IRRIGATION RETURN FLOW
RESEARCH AND DEVELOPMENT PROGRAM
by
Jame s P. Law, Jr., Ph.D.
Program Element Director
Agricultural Wastes Section
Treatment and Control Research
Robert S. Kerr Water Research Center
Ada, Oklahoma
for the
OFFICE OF RESEARCH AND MONITORING
ENVIRONMENTAL PROTECTION AGENCY
Program #13030 GJS
December 1971
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price 40 cents
-------
ABSTRACT
The status of the National Irrigation Return Flow Research and Develop-
ment Program is presented. Current research projects and future program
development are discussed. The report represents the position of the
Environmental Protection Agency (EPA) with regard to the development of
effective controls on the quality of irrigation return flows. Program
goals and milestones are outlined. A number of potential control measures
are discussed. Improvements in the water delivery system, on-the-farm
water management, and the water removal system are considered with respect
to improving the quality of irrigation return flows and decreasing the
degradation of receiving waters. Research and investigations are needed
to evaluate the effectiveness of potential control measures. Demonstra-
tions and educational activities will be required to overcome institution-
al, political, and legal constraints to water management reform.
Key Words: Irrigation return flow, water quality, pollution control,
pollution abatement, agricultural wastewater.
111
-------
CONTENTS
Section Page
I Summary and Conclusions 1
II Introduction 3
III Research and Development Program 9
IV Future Program Development 13
V Potential Control Measures 17
VI References 23
v
-------
FIGURES
Page
1. Model of the Irrigation Return Flow System 4
2. National Irrigation Return Flow Research, Development,
and Demonstration Program - Goals and Milestones 16
vi
-------
TABLES
No.
1 Research Need Statements PPBS 13030 Subprogram Element,
Irrigation Return Flows
vii
-------
SECTION I
SUMMARY AND CONCLUSIONS
The status of the National Irrigation Return Flow Research and Develop-
ment Program is presented. Early program development and current extra-
mural research projects supported by grant funds are discussed. Plans
for future program development represent the position of the Environment-
al Protection Agency (EPA) with regard to the development of effective
controls on the quality of irrigation return flows. Program goals and
milestones required for their accomplishments are outlined. Basically,
the practice of irrigation has detrimental effects on environmental
water quality. Practical means for alleviating and/or controlling water
quality degradation of surface and ground water resources from irrigated
agriculture are urgently needed. Where control measures are not already
apparent, research will be required to develop criteria for effective
solutions.
There are a number of control measures that can improve the quality of
irrigation return flows. The water delivery system can be improved by
lining canals and laterals, using closed conduits for water transporta-
tion, providing adequate control structures, and requiring flow measuring
devices. Improved management practices on the farm would include use of
new irrigation application methods, scientific irrigation scheduling to
insure proper timing and amount, more closely controlled leaching, judi-
cious use of slow-release or other controlled fertilizers, tailwater
recovery and reuse, and specialized cultural practices. In the water
removal system, both tile and open drains may be employed to collect
waste waters, which can then be diverted away from the river system or
subjected to treatment prior to discharge or reuse. Economic considera-
tions are important in selecting these methods.
Research and investigations will play leading roles in evaluating the
effectiveness of potential control measures. Demonstrations and educa-
tion will be required to disseminate the knowledge and experience needed
to overcome institutional, political, and legal constraints to water
management reform.
-------
SECTION II
INTRODUCTION
It has long been recognized that the quality of water draining from ir-
rigated areas was seriously degraded from that of the irrigation water
applied. Agriculturists have viewed this as a natural consequence of
the processes involved, and little attention has been given to the pos-
sibility that progress could be made toward controlling or alleviating
the contributions of mineral salts and nutrients to our nation's water
resources. Recent Federal legislation and a greatly increased national
concern have caused a reversal of this attitude, and EPA has been charged
"to establish a national policy for the prevention, control, and abate-
ment of water pollution" (1). The water quality problems associated with
irrigation return flows are of special concern because irrigated agricul-
ture is the largest consumer of public water resources. It also is of
major importance to the economy of a large segment of the nation and the
supplier of a significant part of the food and fiber produced annually.
Irrigation Return Flow System
The complexities of the irrigation return flow system are portrayed sche-
matically in Figure 1. The model shows the primary sources of return
flow to be canal seepage, bypass water, deep percolation, and tailwater
or surface return flow. Each of these can be subjected to some degree
of manipulation or control through improved management techniques. By-
pass water is chiefly a water resource or conservation problem, since
few pollutants 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 in-
creases saline subsurface drainage from irrigated areas. Canal seepage
can be a significant fraction of the total diversion in many project
areas (2). 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 nutrients and salts to the stream
drainage system.
The areas of research pertinent to the control of water quality degrada-
tion in irrigation return flows are concerned with prediction techniques,
treatment methods, and/or water management practices. Research needs
to date indicate a strong emphasis on the later as the most promising
approach to the control of nutrients and salinity at the source.
-------
PRECIPITATION
INFLOW TO
CANALS
EVAPOTRANSPIRATION
FROM CROPS
EV
EVAPORATION
FROMCANALS
SURFACE RUNOFF
FROM NON-IRRIGATED
LAND
IND. a MUN.
WASTES
OTHER
EVAPOTRANSPIRATION
FROM IRRIGATED LAND
UPSTREAM
APPLIED TO
IRRIGATED LAND
RIVER DIVERTED FOR
FLOW IRRIGATION
GROUND WATER
CONTRIBUTION
RIVER FLOW |
IRRIGATION
RETURN FLOW
DOWNSTREAM
FIGURE 1. MODEL OF THE IRRIGATION RETURN FLOW SYSTEM
NATURAL
INFLOW
-------
Statement of Problem
The major pollution factor associated with irrigation is the increased
concentration of mineral salts in the drainage water. Irrigation is by
far the major user of water in our western states and is responsible for
much of the salt load carried by many of our western river systems. The
control of pollutants contributed by irrigation is not an easy problem
to attack, nor is it likely that irrigation will be abandoned because it
degrades the quality of our water resources. Historically, irrigation
practices have developed more as an art than a science. The principal
scientific endeavors to date have been aimed at increasing crop yields
and improving the design of distribution systems with little or no regard
for the resulting water quality degradation. Salt balance studies have
been performed on district-wide or basin areas to determine the ratio of
total salt leaving to that entering the area, but these have not led to
recommendations for any measure of control over salt-loading to a river
system. Their value has been questioned on the basis that sources of
the salt leaving an area have not been positively identified. They
usually fail to show that all irrigated areas are under a favorable salt
balance or that some areas are not accumulating salt while others are
contributing salt from extraneous sources (2). Application practices
(and malpractices) have been based more on the convenience of the irri-
gator and protection of his water rights than on scientifically tested
management techniques. Research should now be aimed at reversing this
trend and demonstrating that proper water and fertilizer management
practices can indeed be an effective and feasible means of improving
the quality of irrigation return flows. Hopefully, the direct result of
such efforts will be a decrease in the pollutants contributed by irriga-
tion to our surface and groundwater resources.
Program Goals
The major goal of the National Irrigation Return Flow Research and Devel-
opment program is to find practical and economically acceptable means to
control the salinity and nutrient contributions of irrigated agriculture
to our surface and groundwater resources. This can be broken down and
stated in several more specific objectives as follows:
a. Gain knowledge relative to prediction techniques, management
practices, and treatment measures that may be applied to water quality
problems of irrigation return flow.
b. Evaluate the effect of present irrigation practices on salt loads
entering river systems, particularly through groundwater seepage.
c. Demonstrate that improved farm water management offers feasible
means of minimizing salt and nutrient degradation of return flow without
sacrificing crop yields.
-------
d. Develop recommendations and guidelines on irrigation practices,
methods, and systems which would have the greatest effect of reducing
nutrients and salts in return flow while maintaining an acceptable salt
balance in the root zone.
Development of the program goals has been through research need state-
ments submitted and coded into the Program Planning and Budgeting System
(PPBS). The originator of each need statement was asked to describe the
specific problem to be solved, why the solution is important, and how
the solution will be used. Some of the more significant need statements
that have been input to the program are listed by code and title in
Table 1. The major effort of the program is directed toward control at
the source rather than treatment and reclamation of degraded water. The
program leaders collaborate in assigning priorities to the research needs
in accordance with resources available to perform the required studies.
-------
TABLE 1
RESEARCH NEED STATEMENTS
PPBS 13030 SUBPROGRAM ELEMENT, IRRIGATION RETURN FLOWS
Need Title
Code
XAZ Agricultural Wastewater Characteristics
UCA Mineral Quality Relationships of Percolating Irrigation Waters
RBL Salinity Control Through Farm Irrigation Water Management
UBH Treatment of Waste Water from Irrigated Agricultural Areas
PCS Leaching, Reclamation, and Drainage Requirements in Irrigated Areas
RBM Prediction of Salinity in Irrigation Return Flows
PCR Alternate Procedures for Collection, Storage, and Reuse of Irrigation
Return Flows
RBK Economic Evaluation as a Function of Salinity in Irrigation Return
Flows
CBL Reduction of Salt Toxicity to Irrigation Crops by Chelation
CBK Genetic Development of Salt Tolerant Irrigated Crops
WOC Reclamation of Irrigation Return Flow for Reuse (Related to PCR)
WOD Evaluation of Subsurface Irrigation Method as Means of Salinity
Control in Irrigation Return Flow
WOE Boron Removal from Irrigation Supply and Waste Water
WOF Automated Irrigation Systems for Better Water Management and
Salinity Control in Return Flows
WOG Control of Nutrient Losses in Irrigation Return Flows
PAF Effects of Irrigation Management, Climate, Soil, Plants on
Irrigation Water Quality (Related to RBL)
UBI Source Control of Wastes from Irrigated Agricultural Areas
(Related to RBL)
PAG Salt Load in Solution Pick-up and Evapotranspiration Processes
(Related to UCA)
PAI Chemical Reactions and Equilibrium Relationships Between Quality
and Quantity of Irrigation Return Flow (Related to UCA)
7
-------
SECTION III
RESEARCH AND DEVELOPMENT PROGRAM
The first project was an in-house effort conducted in cooperation with
Agronomy Department personnel from Oklahoma State University at the Ir-
rigation Research Station, Altus, in southwestern Oklahoma. The study
spanned one growing season and was conducted on a 7-acre cotton field.
This pilot field study yielded data on the quantity and quality of irri-
gation water applied versus surface return flow and quality of soil
water percolating below the plant root zone. The results of that study
were published as Oklahoma Agricultural Experiment Station Bulletin B-
684 titled "Degradation of Water Quality in Irrigation Return Flows" (3).
One of the earliest and most urgent needs of the program was that of a
comprehensive literature review and preparation of a state-of-the-art
report. A contract was negotiated with Utah State University Foundation
to produce the report, which was completed in May 1969 and published
under the title "Characteristics and Pollution Problems of Irrigation
Return Flow" (2). It provided a broad review of irrigation practices,
mechanics of return flow, and the many complexities of water quality
problems associated with the soil-plant-water system. As one of the
major objectives of the report, research needs and recommendations were
stated. The report was significant in that it pointed out the lack of
information related directly to the control of water quality degradation
by irrigation return flows.
Current Research
The major emphasis toward the objectives of the program to date has been
through the administration of grant funds to support extramural research
projects. Limited manpower has served to curtail in-house research, but
it is expected that this effort will be expanded in the next few years.
One major in-house effort has been the cooperative interagency research
conducted at the Interagency Agricultural Waste Water Treatment Center
at Firebaugh, California. The cooperating agencies were the California
Department of Water Resources, U.S. Bureau of Reclamation, and the Robert
S. Kerr Water Research Center, EPA. The combined activities of the re-
search group represent the current activity under research need UBH,
"Treatment of Waste Water from Irrigated Agricultural Areas." The project
was initiated late in FY-1967. It was originally planned for a three-
year duration and subsequently extended through FY-1971 for completion
of economic and operational studies. St. Amant and Beck (4) have
described the organization and objectives of the interagency research
group. The main objective of the research was to develop economically
feasible methods of removing nitrogen, mainly in the nitrate form, from
the agricultural wastewaters of the San Joaquin Valley. Both assimilatory
-------
(algae stripping) and dissimilatory (bacterial denitrification) biolog-
ical methods have been developed and shown to be feasible. Final reports
of the studies are being completed and will be printed in the near future.
Another interagency research effort has been activated under research
need RBM, "Prediction of Salinity in Irrigation Return Flows," in co-
operation with the Bureau of Reclamation. The objective of this research
is to develop a basin model that will be able to predict the salinity
changes resulting from irrigation in a basin area. The computer model
is being developed and tested through a detailed evaluation of water and
salt movement in the Ashley Valley at Vernal, Utah. The model will be
evaluated further by later studies in other basin areas. The model will
be useful in predicting the effects of irrigation on water quality in
areas prior to irrigation development. The study does not include changes
in water management and fertilizer practices.
Whereas the two projects previously described deal with treatment and
prediction, respectively, other active and pending research is primarily
concerned with water management practices. Utah State University is
being supported with a grant titled "Quality of Irrigation Return Flow."
The project is investigating several related problems that affect the
quality of irrigation return flow. Four sub-project areas being studied
are:
a. Precipitation mechanisms in soils as they affect water quality;
b. Prediction techniques for simultaneous movement of salt and
water in soils and their response to changes in quality of irrigation
water and irrigation management;
c. Managing water in the soil-plant system to control the quality
and quantity of return flow; and
d. Contamination of surface and drainage water with soil and
foliar herbicides.
This project partially meets need statement UCA, "Mineral Quality Rela-
tionships of Percolating Irrigation Waters." Portions of sub-projects
(b) and (c) are being conducted by field studies in the Ashley Valley at
Vernal in order to cooperate with the USER prediction study. Information
interchange between the two projects has been helpful to both. That
portion of the project is also closely related to need statement RBL,
"Salinity Control Through Farm Irrigation Water Management." The final
report from this project will contain recommendations for solving spe-
cific water quality problems associated with irrigation return flow.
A three-year research project has been initiated with a grant *to Texas
A&M University Research and Extension Center at Lubbock dealing with
10
-------
the effects of subsurface irrigation and fertilizer application methods
on the nitrates and salts in percolating irrigation water. Groundwater
contamination already exists in the area of this study, and it is design-
ed to produce positive solutions for that problem. The results of this
study will contribute significant knowledge regarding irrigation methods
and fertilizer practices and their effects on the quality of return
flows. This project is designed to partially meet needs WOD, "Evaluation
of Subsurface Irrigation Method," and WOG, "Control of Nutrient Losses."
In addition, it is closely related to need RBL, "Farm Irrigation Water
Management."
Another three-year grant has recently been awarded to New Mexico State
University to study the quality and quantity of return flow as influ-
enced by trickle and surface irrigation methods. Automation of the
irrigation systems permits this research to contribute to needs RBL,
"Farm Irrigation Water Management," and WOF, "Automated Irrigation Sys-
tems for Better Water Management and Salinity Control." The study is
being conducted in the Rio Grande Valley near Las Cruces and should
contribute significantly toward the potential control of salinity con-
tributed to the Rio Grande in that area.
A demonstration project has been completed in the Grand Valley of western
Colorado which involved the installation of canal lining in portions of
the valley. Preconstruction data on the quality of water draining from
the area were gathered. Evans (4) has described the salinity problems
of Grand Valley and the approach to solutions through canal lining.
Post-construction evaluation of the effects of canal lining on the quality
of the drainage and the salt load contributed to the river from the area
is being made by Colorado State University personnel. Studies in the
Upper Colorado River Basin have shown that an estimated 18 percent of
the salt load at Hoover Dam originated from the Grand Valley area. The
findings of this study will partially meet need UBI, "Source Control of
Wastes from Irrigated Areas," and may be applicable to other areas which
produce high salt loading to the receiving stream.
Washington State University was recently awarded grant funds for the
"Evaluation and Demonstration of Irrigation Methods and Practices to
Reduce Contamination in Irrigation Waste Waters." The proposed research
is an extension of an ongoing project to include water quality measure-
ments. This project will make a significant contribution to research
need RBL, "Salinity Control Through Farm Irrigation Water Management."
Another program effort supported by grant funds to Colorado State Univer-
sity is titled "Irrigation Return Flow Quality Literature Abstracting."
Literature is being searched and abstracted, starting with the year 1968
and continuing through 1972. The abstracts will be accumulated and
published periodically in report form. Abstracts are also furnished to
the Water Resources Scientific Information Center (WRSIC) for inclusion
11
-------
in their publication, "Selected Water Resources Abstracts." An addition-
al task being completed under the terms of this active grant is the pre-
paration of a report covering "Research Needs in Irrigation Return Flow
Quality Control." The major topics covered include:
a. Define the major geographic areas where irrigation return flow
problems exist.
b. Specify the major water quality problems arising from irriga-
tion 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 the potential solution to solve the critical
problems.
This report will be useful in future program planning. It will provide
specific problem definitions that are needed to develop an integrated
program for achieving solutions needed to establish guidelines for the
control of pollutants arising from irrigated areas. It will be published
and made available to interested research groups in water quality control
investigations.
12
-------
SECTION IV
FUTURE PROGRAM DEVELOPMENT
Water quality degradation is a serious matter to agriculture, as well as
other water users. It has been pointed out (5) that we approach the
need for water quality management with little preparation in either
policy or technology for upgrading the quality of irrigation return flow.
The unfortunate prospect is that irrigation will continue to contribute
to the decline in water quality in many areas unless better systems for
managing the quality of return flows are found. Agricultural scientists
face a challenging future in achieving these objectives.
It is recommended that field research sites be used for specific studies
required to improve water quality in the major problem areas. A number
of considerations are of paramount importance for recommending and ini-
tiating studies at outlying field stations.
First of all, the new technology needed must be evaluated and demonstrated
in field plots. The wide variety of water quality problems can not be
investigated at one location under one set of conditions, including soil
profile characteristics, irrigation water quality, climate, cropping
system, etc. The significant water quality problems resulting from
irrigation differ in widely separated irrigated areas with differences
in soils, climate, crops, and management practices. Therefore, several
field site locations should be selected on the basis of suitability for
providing the technology needed to improve water quality in the major
problem areas.
A second major consideration concerns the capital investment that would
be required for the purchase, preparation, and equipping of field stations
to study irrigation return flow problems. As a beginning for this pro-
posed program, it is recommended that cooperative agreements with exist-
ing agricultural experiment stations be considered. These agreements
should vest control of the study sites and operations in the program
leaders. The use of existing irrigation facilities, buildings, labora-
tory space, etc., would be arranged by contract. The contractual arrange-
ments could also provide additional manpower for field work, sample
collection, etc., as required.
Thirdly, this approach would provide a means of cooperative in-house and
extramural effort that would be most effective in developing solutions
to protect the environment. It would require that program personnel be
stationed at each'field site to serve as project director. The director
would have responsibilities for assisting in planning and conducting the
specific studies. His duties would also include analysis of data and
reporting the findings. Depending on the scope of the research at the
field sites, it is conceivable that additional program personnel would
be required as support to the project director.
13
-------
Finally, the priority of research sites, their location, and the problems
to be studied would be based on the relative magnitude of the water
quality problems from irrigation return flows and the potential for
improving water quality.
Extramural research, development, and demonstration grants to answer
high priority needs will continue to be a major part of the future
program. Recommendations for research proposals are based upon
scientific merit and program interest. First of all, the proposed re-
search design must be based on scientific principles. It must be care-
fully conceived and planned to assure that the stated objectives will be
achieved. Uniqueness and originality are important points for consider-
ation. Use of accepted analytical methodology and technical procedure
is required. Assurance of adequate analytical quality control, data
evaluation, and interpretation procedures is necessary. The program
interest evaluation is concerned with fitting the research to the program
needs having high priority and which are not presently being funded
elsewhere. The research must be geared to solving a specific problem,
and a need for the study must be shown. When these criteria are met,
a research proposal is well on its way to favorable consideration.
Future program plans clearly indicate a coordinated effort involving
both in-house and extramural research activities. The extent to which
the program objectives can be met will depend in large measure upon the
resources, both professional manpower and funds, made available to the
program. In order to accomplish the program goals as set forth, an
increased level of resources will be required. Program goals and mile-
stones have been set forth in a report on "National Plan and Strategy
for Water Quality" (6) in the following sequence:
1. Develop an inventory of and evaluate water quality problems from
irrigation return flows (by 1972).
2. Conduct technical studies to characterize magnitude of salinity,
nutrient and sediment problems (1972-1974).
3. Demonstrate measures and practices to prevent or control salinity
pollution (1973-1975).
4. Demonstrate methods to treat, control, or prevent nutrient pollu-
tion (1973-1975).
5. Develop and demonstrate sediment prevention and control measures
(1973-1975).
6. Develop and demonstrate measures to prevent or control pesticides
pollution (1973-1975).
14
-------
7. Guidelines and/or manuals of recommended practices for control
of irrigation return flow problems (1976).
A more detailed analysis of future program plans is provided schematic-
ally in Figure 2. Program goals and milestones are indicated in logical
sequence. This sequence could be repeated in each major study area
involved. The suggested time-sequence of accomplishments are considered
to be realistic even though they do not coincide exactly with those
listed above. The overlapping of time periods'indicates latitude in
initiating the various activities and advancing more rapidly toward the
program goals.
15
-------
Figure 2
NATIONAL IRRIGATION RETURN FLOW RESEARCH, DEVELOPMENT AND DEMONSTRATION PROGRAM
Goals and Milestones
State-of-the-Art
Report
(Completed)
Define Areas
and Nature of
Major Problems
I
Organize and Fund
Study in Major
Problem Area(s)
Research Needs
for Technological
and Institutional
Requirements
FY 1972
FY 1973-74
Detailed Reconnaissance
of Water Quality Degradation
and Necessary Controls
Economic Evaluation
of Control Actions
Prediction of Effects
of Control Actions
Institutional Constraints
on Control Actions
Develop New Technology for
Control of Salinity,
Nutrients, Sediment, and
Pesticides
Develop Prediction Models
to Evaluate Effects of
New Technology
FY 1973-75 (3 years)
Recommend
Control Measures
for Water
Quality
Improvement
Water Delivery System
Soil-PIant-Water System
Water Removal System
Treatment Systems
Develop Institutional
•Models to Implement
Control Programs,
Develop Economic
Incentives to
Implement
Control Programs
FY 1975-77 (3 years)
Demonstration of
Control Systems
in Major Problem
Areas
Guidelines and/or Manuals
of Recommended Practices1
Implement Control
Programs
FY 1977-78 (2 years)
-------
SECTION V
POTENTIAL CONTROL MEASURES
It seems appropriate at this point to present a brief discussion of the
more apparent possibilities for achieving some measure of control over
the quality of irrigation return flows. Some control technology has
already been developed and the major missing link is the evaluation of
the effects on the quality of return flows and subsequent impacts on
the quality of receiving streams. In addition, the program must concern
itself with the institutional factors affecting the acceptance and im-
plementation of effective control measures. This aspect presents some
of the more difficult problems. It, therefore, seems assured that the
future program will be heavily involved in evaluation of effects of
control measures, technology transfer activities, and studies of insti-
tutional factors.
Potential control measures may involve physical changes in the system,
improvements in present management and cultural practices, or changes in
the institutional influences upon the system. Since irrigation return
flow is an integral part of the hydrologic system, control measures for
managing the return flow from an irrigated area must be compatible with
the objectives for total water resource management and development.
The irrigation return flow system (Figure 1) can be subdivided into
three major sub-systems: (a) water deliver; (b) the farm; and (c)
water removal. Water delivery includes the transport of water and
pollutants from the headwaters of the watershed to the point of diver-
sion, thence to the individual farm. The farm sub-system begins at the
point where water is delivered to the farm and continues to the point
where surface water is removed from the farm. Also, the farm sub-
system is defined vertically as beginning at the soil surface and
terminating at the bottom of the root zone. Water removal includes sur-
face runoff from the farm and water moving below the root zone. Quality
problems in the water removal sub-systems are minimized by having highly
efficient water delivery and farm sub-systems. Minimizing the quantity
of surface runoff will assist in alleviating water quality problems due
to sediments, phosphates, and pesticides; whereas minimizing deep per-
colation 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
17
-------
measures for improving the quality of water diverted from a river.
Consequently, they play a role in the management of the irrigation
return flow system. 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.
Canal and Lateral Lining - Many unlined irrigation canals traverse long
distances between the diversion point and the farm land. Seepage losses
may be considerable, resulting in low water-conveyance efficiencies.
Canal lining has traditionally been employed to prevent seepage and the
costs of lining have been justified primarily on the basis of the value
of 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. It has been
reported (2) 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 soils along the
canals are high in residual salts, the salt contribution from this source
could easily exceed that leached from the irrigated land to maintain a
salt balance. The salt from this source could be largely eliminated by
canal lining. Evaporation losses from canals commonly amount to a few
percent of the diverted water. A closed conduit conveyance system has
the advantage of minimizing both seepage and evaporation losses. Either
lined canals or closed conduits will reduce evapotranspiration losses due
to phreatophytes. The closed conduit system requires less land and pro-
vides better water control than a canal system. Water quality improve-
ment may very well prove to be the greatest economic justification for
canal lining and/or closed conduit systems.
Farm Water Management
Due to the nature of irrigated agriculture, whereby salts must be leached
from the root zone, optimum control will require improvements in on-the-
farm water management. In order to attain high irrigation application
efficiencies, the timing and amount of water being delivered to the farm
must be controlled. At the same time, the farmer must be capable of
controlling the water supply as it moves across the farm. Control of
the water requires regulating the water delivery rate, as well as
measuring the water applied.
Application Methods - The effect of methods of application on the quality
and quantity of return flow has not received detailed study. Convention-
al surface and sprinkler methods are most commonly used because of their
low initial cost and ease of adaptability to a wide range of*field and
surface conditions. New and unique approaches to application methods
18
-------
need to be found. Two that appear to offer great promise in the control
of both quantity and quality of return flows are subsurface application
(7) and drip or "trickle" methods (8).
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 concentration are reduced. The water content of the
soil is maintained below field capacity so that some precipitation can
be stored in the soil, introducing an additional dilution factor. Com-
parable crop yields have been produced with 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
water supply can be increased. Application rates can be closely con-
trolled and the method can be readily automated.
The drip irrigation technique has aroused enthusiastic interest in Israel
(8). The major advantages include increased crop yield, reduced salinity
damage, and shortened growing season with earlier harvest. The method
involves the slow release of water on the surface near the base of the
plants. Evaporation losses are greatly reduced and moisture release is
confined to the area of the plant root system.
Both of these methods need to be evaluated as to their potentials for
reducing salinity in return flows, increasing yields with limited water
supplies, and reducing fertilizer nutrient losses by leaching. Liquid
fertilizers can be applied by either of these methods in small controlled
doses throughout the growing season. The potential economic advantages
of saving both water and fertilizer nutrients and reducing labor costs of
operation make these methods attractive. Economic evaluation might show
that these benefits would largely offset the initial cost of installation.
Irrigation Scheduling - Historically, irrigation has been practiced more
as an art than a science. When left to his own discretion, a farmer may
delay irrigation until the crop is stressed and then apply more water
than actually needed, resulting in poor water management and reduced
yields. This two-fold problem is presently being overcome by irrigation
scheduling based on climatic, soil, and crop data (9, 10). Commercial
firms gather the data and notify the irrigator when to irrigate a certain
crop and the amount to be applied. The farmer pays a fee for the service
and is thus relieved of the responsibility of deciding when is the best
time to irrigate.
Experience in southern Idaho and the Salt River Project in Arizona during
the past few years clearly indicates increased yields due only to scien-
tific scheduling of irrigation. To date there has been little reduction
in water use, although it seems likely that this would occur with time
as the farmer gains more knowledge of actual crop requirements. This
19
-------
approach offers great promise as a water management control tool and may
provide the knowledge and experience needed to overcome present antiquat-
ed institutional, political, and legal influences that present the major
stumbling blocks to water management reform.
Control of Leaching - Another possible control measure is closely con-
trolled leaching to minimize salt pickup from underlying geologic for-
mations. The most drastic action would be to eliminate irrigation in
areas of high salinity such as those where the soils are formed from and
overlying salty shales. Preventing or reducing the amount of water
penetrating to deeper saline strata would also reduce the salt load in
return flows. The use of natural or artificial barriers below the root
zone, coupled with drainage systems to intercept drainage water before
it reaches the deeper strata, would be effective. Regulating the amount
of water applied to the land and thereby regulating the amount of drain-
age constitutes a combination of controlled leaching and dilution.
Further study is needed to evaluate this approach to the control of
salinity in return flows.
Fertilizer Nutrients - Nitrogen-use efficiency may be improved by the
use of slow-release fertilizers or by adding liquid fertilizers frequent-
ly through the irrigation water supply. The present higher cost of these
products is the chief deterrent to increased acceptance. If regulations
were imposed to require their use in areas where nitrogen problems occur,
increased sales volume would act to lower the cost of production and a
more favorable pricing schedule would result. An added advantage of slow-
release fertilizers is fewer applications per season. Further evaluation
of these products with regard to improved quality of irrigation return
flow is required.
Tailwater Recovery - In water-short areas, tailwater recovery is practiced.
In addition to increasing water-use efficiencies, the practice serves as
a control of sediment erosion with its adsorbed pesticides, phosphorus,
heavy metals, etc. The water recovered is returned to the irrigation
supply rather than released to surface drainage systems. The quality of
surface return flows is only slightly degraded and entirely satisfactory
for reuse after settling of suspended solids (3, 11). Improved irriga-
tion practices would likely result in order to minimize the quantity of
water and sediment from cropland. In extreme cases, enforceable regula-
tions may be required to effectively control tailwater losses and protect
downstream water users.
Cultural Practices - In areas of tight soils and saline water supply,
cultural practices become significant if crops are to be grown sucess-
20
-------
fully. Under these conditions, management alternatives are: (a) more
salt tolerant crops; (b) special deep tillage may be required; (c) leach
in the off-season or alternate years; (d) careful seed-bed preparation
and seed placement; and (e) close control of timing and amount of water
applied. Special practices such as mulching and reduced tillage may be
effective in reducing soil water evaporation. These special cultural
practices are more often aimed at crop production under less-than-ideal
conditions than toward improved quality of return flow, although the two
often go hand-in-hand.
Water Removal System
The water removal sub-system transports surface runoff and subsurface
drainage from irrigated lands. The tailwater may be returned to the
delivery system, become water supply for an adjacent farm, or be trans-
ported back to the river. Subsurface drainage may seep into open drains
or to lower lands along the river where salt damage often occurs. There
are essentially three management alternatives for preventing or minimizing
the quantity of pollutants discharged to the river: (a) divert the drain-
age to some discharge point or sink area away from the river; (b) treat-
ment for removal of pollutants prior to reuse or discharge; and (c)
provide dilution to minimize the detrimental effects. Economic consider-
ations are of prime importance in each of these alternatives.
Diversion - Subsurface return flows are often collected by tile drainage
systems underlying irrigated areas. Being thus collected into a common
sump or open drain, they may easily be diverted to some point away from
the river. The proposed drainage system for the San Joaquin Valley and
the present system for the Wellton-Mohawk district in southern Arizona
are examples of return flows being carried away without returning to the
river or supply canal system. Return flows diverted to suitable sink
areas may provide wildlife habitat. Either of these alternatives prevents
the addition of pollutant loads to the river system. Other considerations,
such as water rights of downstream users, may be important in selecting
suitable diversion schemes for irrigation return flows.
Treatment - The present high cost of desalination processes is the chief
deterrent to their use for reclaiming saline water. Only in extreme
cases would they prove economically feasible. Recent cooperative research
at Firebaugh, California, conducted by the Environmental Protection
Agency, Bureau of Reclamation, and California Department of Water Re-
sources has developed methods of removing nitrates from irrigation
return flows. In these studies, both algae stripping and bacterial
denitrification proved feasible to treat agricultural tile drainage prior
to its release into San Francisco Bay via the San Joaquin drainage canal
21
-------
system. Final plans for the treatment facility are being considered.
Dilution - Dilution of return flow occurs naturally in nearly all up-
stream irrigated areas, where drainage waters and other return flows are
diluted in the main stream so that the resultant quality is acceptable
downstream for irrigation and other beneficial uses. Multipurpose res-
ervoirs have provided storage capacity for low-flow augmentation as well
as other beneficial purposes. Stream-flow regulation can be beneficial
for quality control, although such benefits are usually incidental to
other primary requirements for regulated flow.
There are limitations to the effectiveness of dilution as a means of
managing return flows. The major physical limitation is the amount of
high quality water that can be stored and released at the desired times
to achieve maximum benefits from dilution. The legal implications of
obtaining water rights for the purpose of dilution could be exceedingly
complex. In general, such practices would result in diminished supplies
for other purposes and this in areas where water rights already exceed
the supply. Presently, it appears that stream-flow regulation for
quality control of irrigation return flows cannot be relied upon as a
useful management technique.
22
-------
SECTION VI
REFERENCES
1. Federal Water Pollution Control Act (PL 84-660) as amended by amend-
ments of 1961 (PL 87-88), the Water Quality Act of 1965 (PL (89-234)
and the Clean Water Restoration Act of 1966 (PL 89-735), Section 1
(a).
2. Utah State University Foundation, "Characteristics and Pollution
Problems of Irrigation Return Flow," Robert S. Kerr Water Research
Center, Ada, Oklahoma (May 1969).
3. Law, J. P., Jr.; Davidson, J. M., and Reed, L. W., "Degradation
of Water Quality in Irrigation Return Flows," Oklahoma Agricultural
Experiment Station Bulletin B-684 (October 1970).
4. Law, J. P., Jr.; and Witherow J. L., (eds.)> "Water Quality Manage-
ment Problems in Arid Regions, " EPA, Water Pollution Control
Research Series 13030 DYY06/69 (October 1970).
5. Law, J. P., Jr.; and Witherow, J. L., "Irrigation Residues,"
Journal Soil and Water Conservation, Vol 26, pp. 54-56 (March-
April 1971).
6. Federal Water Quality Administration, "National Plan and Strategy
for Water Quality," FWQA Report No. 14-12-910/10 (November 1970).
7. Busch, C. D., and Kneebone, W. R., "Subsurface Irrigation with
Perforated Plastic Pipe," Trans. ASAE 9. pp 100-101 (1966).
8. Goldberg, D., and Shmueli, M., "Drip Irrigation - A Method Used
Under Arid and Desert Conditions of High Water and Soil Salinity,"
Trans. ASAE 13. pp 38-41 (1970).
9. Franzoy, C. E., and Tankersley, E. L., "Predicting Irrigations
from Climatic Data and Soil Parameters," Trans. ASAE 13, pp 814-
816 (1970).
10. Jensen, M. E., Robb, D. C. N., and Franzoy, C. E., "Scheduling
Irrigations Using Climate-crop-soil Data," Jour. Irrig. and Drain.
Div. ASCE 96(IRl). pp 25-38 (1970).
11. Bondurant, J. A., "Quality of Surface Irrigation Runoff Water,"
Amer. Soc. of Agri. Engineers. Paper No. 71-247, 8 pp (1971).
ft U. S. GOVERNMNET PRINTING OFFICE : 1972—484-484/125
-------
1
Accession Number
w
5
f\ Subject Field &. Group
05G
SELECTED WATER RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
Robert S. Kerr Water Research Center, Environmental Protection Agency
Ada, Oklahoma
Treatment and Control Research, Agricultural Wastes
Title
National Irrigation Return Flow Research and Development Program
10
Authors)
James P. Law, Jr.
16
Project Designation
Program No. 13030 GJS
21 Note
22
Citation
Report 13030WRV12/71, Environmental Protection Agency, Washington, B.C.,
1971, 23 pages, 2 fig., 11 ref.
23
Descriptors (Starred First)
*Water quality control, *irrigation effects, pollution abatement,
waste water
25
Identifiers (Starred First)
*National research program, *irrigation return flow,
control measures, agricultural waste water
27
Abstract
The status of the National Irrigation Return Flow Research and Development
Program is presented. Current research projects and future program development
are discussed. The report represents the position of the Environmental
Protection Agency (EPA) with regard to the development of effective controls
on the quality of irrigation return flows. Program goals and milestones are
outlined. A number of potential control measures are discussed. Improvements
in the water delivery system, on-the-farm water management, and the water
removal system are considered with respect to improving the quality of irrigation
return flows and decreasing the degradation of receiving waters. Research and
investigations are needed to evaluate the effectiveness of potential control
measures. Demonstrations and educational activities will be required to overcome
institutional, political, and legal constraints to water management reform.
(Law-EPA)
Abstractor
James P. Law, Jr.
Institution
Robert S. Kerr Water Research Center, EPA, Ada, Oklahoma
WR:I02 (REV. JULY 1969)
WRSIC
SEND, WITH COPY OF DOCUMENT. TO: WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON. D. C. 20240
* SPO: 1970-389-930
------- |