EPA 430/9-74-006
EVALUATION OF SALINITY
CREATED BY IRRIGATION
RETURN FLOWS
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Water Program Operations
Washington, D.C. 20460
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EVALUATION OF SALINITY
CREATED BY IRRIGATION RETURN FLOWS
Arthur L. Jenke, Hydrologist
Non-Point Source Control Branch
Office of Water Program Operations
Environmental Protection Agency
January, 1974
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price Jl.M
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TABLE OF CONTENTS
Page
ILLUSTRATIONS V
ACKNOWLEDGEMENTS ^...^ viii
INTRODUCTION 1
The Problem 2
SUMMARY AND CONCLUSIONS H
GENERAL 7
Irrigation Return Flow 9
Origin of Return Flow 12
Salt Accumulation in the Soil 21
PROBLEMS ASSOCIATED WITH EXCESSIVE SALINITY 23
Effect on Domestic Use , 24
Effect on Agriculture 26
LOCATION OF MAJOR PROBLEM AREAS 36
Colorado River Basin 33
Upper Colorado River Basin Region 40
Lower Colorado River Basin Region 45
The Imperial Va,lley 49
The Coachella Valley 55
The Rio Grande Basin 59
Upper Rio Grande Basin 59
Middle Rio Grande Basin 62
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Lower Rio Grande Basin 64
Pecos River Basin 67
Central Valley Basin, California 68
Sacramento Valley 69
Sacramento-San Joaquin Delta 69
San Joaquin Valley 72
Yakima River Basin 75
Snake River Basin 77
Other Major Problem Areas 78
REMEDIAL AND CONTROL MEASURES 81
* Farm Water Delivery System 81
Farm Water Management System 93
Water Application Methods , 96
Surface Methods 96
Trickle and Drip Methods 98
Sprinkler Methods 99
Subsurface Methods 100
Minimum, Tillage 102
Farm Water Removal System 103
Future Methods of Return Flow Control 107
NEEDED DEMONSTRATIONS AND RESEARCH 110
Technical 110
Institutional-Legal 113
GLOS SARY OF TERMS 118
REFERENCES CITED 120
111
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Cover Photograph: Irrigated lettuce
in the Palo Verde Valley, California.
Water for the Palo Verde Project is
diverted from the Colorado River.
Photo courtesy Bureau of Reclamation,
U.S. Dept. of the Interior.
iv
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ILLUSTRATIONS
Figure
1. Freeze protection afforded citrus nursery as a result
of overnight irrigation in Florida. Temperature was
approximately 21 degrees fahrenheit for 8 hours. 10
2. Destructive effect created by excessive amounts of
tailwater being lost from irrigated field having too
steep a grade for efficient irrigation. Hudspeth 14
County, Te xa s.
3. Excessive amount of tailwater being lost from irrigated
field. Note water flowing across highway. Hudspeth
County, Texas. 15
4. Considerable erosion caused by excessive irrigation on
light sandy soil. Gully depths are greater than two
feet. Near Caldwell, Idahq. 16
5. Erosion caused by excessive irrigation. San Diego
County, California. 17
6. Serious water erosion caused by excessive use of
irrigation water on too steep slopes. Approximately 75
percent of the topsoil was lost in one irrigation,
Fremont County, Wyoming. 18
7. Irrigation waste water erosion on a cultivated field.
Morrill County, Nebraska. 19
8. Citrus grove abandoned as result of build up of salt in
the soil. Coachella Valley, California. 21
9. Salt damage to carrot crop, Coachella Valley,
California. 29
10. Sugar beets growing sparsely along salt-encrusted
ridges between irrigation furrows. Irrigation water
containing salts rose to the ridge surface through
capillary action and evaporated, leaving the solids
behind. California. 30
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11. Salt buildup in soil results in extensive damage in
this flax field as shown by the bare areas. Imperial
County, California. 31
12. Aerial view of irrigated farmland southwest of Roll,
Arizona. Standing salty water and saline soils
resulted in a less of approximately 1000 acres of
crops. 32
13. Here high water table prevents removal of surface water
after irrigation, resulting in ponding of water and
drowning of crop. Imperial Valley, California. 51
1U. Tile, gravel and sights placed ahead of construction on
an irrigated farm in the Imperial Valley, California.
The tiling operation is engineered and constructed by
the Imperial Irrigation District Engineering
Department. 53
15. Typical discharge of tile drain designed to lower the
water table beneath irrigated land. Tile drainage
commonly discharges into open collection ditches for
ultimate disposal in this instance into the Salton
Sea. Imperial Valley, California. 54
16. Grove of heavy-laden date palms near Indio, California
in the Coachella Valley. The Valley is one of a few
areas in the United States where the date palm thrives. 57
17. Seeding of presprouted rice using aircraft. 70
18. Application of pesticide by aerial crop spraying. 71
19. Earthen water conveyance ditch being lined by spraying
or "shooting" with concrete. No reinforcement is used
in this method. Final County, Arizona. 84
20. Pouring concrete ditch with size 12 wire mesh being
placed in the concrete. This ditch is 34 inches deep
with 1 to 1 side slopes. Pueblo County, Colorado. 35
21. The Delta B Canal, a large conveyance channel near
Delta, Utah being lined with plastic. Two 32 foot
plastic strips are being used to line the canal. 86
VI
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22. A modern concrete-lined irrigation canal. Note control
gates which can be closed in order to regulate the flow
of water into the desired channel. The crop is
alfalfa. Installation is near Red Bluff, California. 87
23. Steel mainline (42 inch penstock) capable of delivering
50 cubic feet per second of irrigation water to 3000
acres of cropland. Near Payette, Idaho. 88
24. Irrigation pipe being delivered by helicopter to site
in mountainous terrain. This 30 inch flume will
deliver snow-melt runoff water directly to an open
diversion ditch. Near Gypsum, Colorado. 89
25. Earthen irrigation storage reservoir being lined with
grout or "gunnite" reinforced with wire mesh. Sealing
the walls and floor of the structure virtually
eliminates seepage. San Diego County, California. 91
26. Polyethylene lining being placed in large irrigation
reservoir to render the water-holding facility
impervious to leakage. Riverside County, California. -92
27. On-farm irrigation tailwater return pit. Intercepted
water is recycled by pumping through a plastic pipeline
to a concrete-lined ditch for reuse. Near Pecos,
Texas. 106
Significant Irrigation Areas in the Seventeen Western
Conterminous States. 37
VII
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ACKNOWLEDGEMENTS
The information presented in this report has been drawn
from various sources. The references cited represent a
worthwhile and useful assemblage of publications on the
subject of irrigation return flow but is not intended to be
all-inclusive. The Soil Conservation Service, USDA, and the
Bureau of Reclamation, USDI, have made a valuable
contribution in the form of both technical advice and
photographs of various aspects of problems associated with
irrigated agriculture and methods related to their solution.
Technical advice, comment, review and editing were
provided by personnel of the Non-Point Source Control
Branch, Office of Water Program Operations, and by personnel
of other elements of the Environmental Protection Agency.
vin
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INTRODUCTION
Irrigated agriculture has been practiced in arid and
semi-arid regions of the world since the beginning of man's
civilized history. Supplementary irrigation during the
growing season is becoming increasingly commonplace in humid
regions.
The earliest known records of man's attempt to raise
crops using artificial application of water are found in the
Middle East and North Africa. The remains of wells,
underground collection systems, dams, reservoirs, terraced
irrigation works, catchment basins, aqueducts and conveyance
channels in the Middle East all indicate that the land once
supported a large population with an advanced knowledge of
irrigated agriculture. Today, this once verdant land is
largely barren and non-productive as a result of salinity
buildup in once-fertile valleys, salt marsh development,
denudation of topsoil by aeolian and fluvial erosion, sand
dune encroachment, and general deterioration.
Of the world's nations, China irrigates an estimated
182,855,000 acres (74,001,100 hectares), India 93,000,000
acres(37,637,100 hectares) and the United States
approximately 44,000,000 acres (17,807,000 hectares).
Irrigated agriculture is practiced on about 10 percent of
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the cropped land of the United States and yields about 25
percent of the total national crop value.
The_Problem
Irrigation is not without dilemmas. Serious problems
of salinization and water-logging of land commonly result
from inferior or inefficient irrigation practices. The
problem of excessive salinization is not necessarily
confined to soil. Increases in salinity of waters receiving
irrigation return flows have been occurring at an alarming
rate in the United States during the past two decades.
Water pollution resulting from irrigated agriculture
originates from both non-point, or diffuse, and point
sources. The impact of agricultural irrigation wastes,
including salinity, sedimentation, pesticides and nutrient
runoff and organic debris, on water quality degradation has
only been recognized fully in recent years. This was due to
the gradual development of the problem. Significant
increases in irrigated acreage since the termination of
World War II, along with increases in the use of pesticides
and fertilizers have focused attention on water quality
deterioration associated with irrigation practices.
This report is devoted primarily to an objective
presentation of the nature and extent of water quality
deterioration created by the introduction of salinity into
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the aquatic environment by irrigation return flows. While
it deals primarily with salinity, or total solids, it
recognizes that sedimentation, nutrients, pesticides,
organic debris, and heavy metals, among others, contribute
significantly to the problem of water quality degradation
throughout the nation. Water uses affected are municipal,
industrial, commercial, downstream agricultural and
recreational, all of whom receive water of ever-diminishing
quality. Deep percolation of irrigation returns is causing
increasingly significant pollution of the ground water en-
vironment in many parts of the nation.
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SUMMARY,AND_CONCLUSIONS
1. Irrigation, the artificial application of water to the
land, can result in serious water pollution problems in the
aquatic environment wherever it is practiced.
2. Numerous water quality changes may take place during
irrigation. The magnitude and nature of these changes are
functions of mineralization, evaporation, transpiration, ion
exchange, solution, leaching and biochemical action.
3. Surface runoff water from irrigated lands may be
expected to contain a mineral composition similar to that of
the applied water, with a significant increase in
pesticides, fertilizers, organic debris, soil particles,
colloids, heavy metals and other pollutants derived from
accidental or purposeful placement onto the land.
U. Irrigation water which has moved through the soil (deep
percolation) may become burdened with excessive dissolved
solids, and possibly a change in ionic composition. The
water may also acquire soluble fractions of fertilizers such
as nitrates. A reduction in insoluble nutrients, degradable
pesticides, oxidizable organics, pathogenic organisms and
bacteria can be expected.
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5. Degradation of water quality can be costly to the
consumer. Adverse economic effects on municipal/ industrial
and commerical users often necessitates increased and
expensive treatment. Agriculture frequently experiences
impaired crop yields and greater water use requirements.
Deep percolation, often required to leach salts below the
plant root zone, may introduce toxic levels of nitrates into
the aquifer.
6. Improved and modernized on-the-farm water management
practices represent the most feasible approach to the
abatement or elimination of water quality degradation caused
by irrigation return flows. An acceptable control program
includes the application of recognized technology at the
pollution source. This is in harmony with the time-honored
concept that pollution be abated at the source rather than
by applying treatment to the contaminated waters.
7. Demonstration and pilot control projects designed to improve
on-farm irrigation efficiency should be afforded high prioritv
in the overall effort to abate pollution created by irrigation
returns.
8. Legal and institutional factors combine to constrain more
efficient water practices, particularly in the Western
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United States. The concepts and rules of the prior
appropriation doctrine, in which water quality is not
considered, are major deterrents to the implementation of a
sound water management technology. A possible solution may
lie in the reinterpretation of the doctrine.
9. A piecemeal approach to the water quality degradation
problem caused by irrigation return flows will be
ineffective. (Only a basin-wide total control program will
prpduce acceptable and lasting results.
10. There is a need for additional documentation of
pollution caused by irrigated agriculture throughout the
nation. Records currently available too often involve only
those areas where salinity is already acute. Frequently,
the modifying or diluting effects of ample water supplies
mask continuing increases in salinity. Well-planned
monitoring and surveillance programs will direct immediate
attention to seemingly inconspicuous problem areas and allow
corrective measures to be applied.
11. The best available irrigation and drainage management
methods, aimed at assuring a minimum generation of wastes,
should be incorporated into the initial planning and
development of all future irrigation projects.
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GENERAL
Irrigation is the artificial application of water to
land to supply and maintain optimum soil moisture necessary
for plant growth. In arid and semi-arid regions of the
world, irrigation accounts for almost all of the life -
supporting water for agriculture whereas in sub-humid and
some humid areas irrigation is supplementary and principally
used to maintain soil moisture during periods of drouth.
The practice of irrigation was known to the peoples of
ancient Egypt and Asia Minor. Irrigation systems in that
part of the world are evident today. This beginning was in
arid and semi-arid lands similar to those in many parts of
the Western United States. Increases in population created
concentrations in cities and villages and a reduction in the
nomadic way of life. This created increased crop demands
and irrigated agriculture was the method that could assure a
continuous food supply on a reasonably reliable basis.
Irrigation was, and is, a science of survival. Successfully
practiced, it enabled man to survive drouths, support larger
populations, and expand territorially and culturally.
There are approximately 44,000,000 acres (17,807,000
hectares) of irrigated land in the United States. About 90
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percent is in the seventeen western conterminous states*-
The balance lies in humid and semi-humid states where there
is a need for supplemental irrigation during periods of
drouth. Florida, for example, ranks tenth in the national
inventory with 1,490,000 irrigated acres (603,000 hectares).
The importance of irrigated agriculture to the national
economy is apparent when it is realized that irrigation is
practiced on about 10 percent of the nations cropland and
generates approximately 25 percent of the total crop value.
Irrigated agriculture accounts for about 35 percent of
the total water withdrawn in the nation for off-channel uses
and approximately 85 percent of the total national water
consumption. The national annual irrigation water
requirement, projected to 1980, is placed at 140,000,000
acre-feet (172,688, 600, 000 cubic meters) (1). This water
will be supplied from both surface and ground water sources.
The application of water to cropland under controlled
conditions has many advantages. It enables the equitable
distribution of water-soluble fertilizers, liquefied animal
*Those conterminous states located west of the eastern
boundaries of North Dakota, South Dakota, Nebraska, Kansas,
Oklahoma and Texas
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wastes, and pesticides. Crop cooling to ensure continued
growth, and frost protection are additional benefits (Figure
1) . Partial control of date of maturity and subsequent
early harvest of crops such as fruits, vegetables and
flowers may also be achieved through irrigation (2).
l£Ei2§tion Return Flow
Of the total water applied during irrigation, as much
as 65 percent may be used consumptively. This use includes
loss by direct evaporation from the soil plus transpiration
from plants. Consumptively-used water is that discharged
into the atmosphere as vapor and is no longer available for
reuse within or by the existing system. The balance of the
applied water, or about 35 percent, is termed irrigation
return flow and finds its way back into the surface or
subsurface hydrosystem. Irrigation return flow then, is the
water diverted for irrigation which returns to the surface
stream or to the subsurface ground water environment (3).
The practice of irrigation necessarily degrades the
quality of applied water to some degree inasmuch as the
water is used consumptively. Evaporation and transpiration
alone may concentrate dissolved minerals in the applied
water as much as 300 percent. In addition to an increase in
salinity, the applied water may acquire sediments,
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FIGURE 1. Freeze protection afforded citrus nursery
as a result of overnight irrigation in Florida.
Temperature was approximately 27 degrees farenheit
for 8 hours. Photo Courtesy Soil Conservation Service,
U.S. Dept. of Agriculture.
10
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pesticides, fertilizers, organic debris, heavy metals, trace
minerals, farm oils and greases, bacteria (including
pathogenic organisms), nematodes and other forms of
pollution. Salinity, a major water pollutant, and its
effect on the aquatic environment, is addressed in this
report.
Salinity increases associated with return flows may be
brought about by both consumptive and non-consumptive uses
of applied water. The principal constituents comprising
return flow salinity are the water-soluble compounds of
calcium, magnesium, sodium and potassium. Minor amounts of
iron, aluminum, manganese and other cations may also be
involved. The dominant anions in the compounds are
carbonates, bicarbonates, sulfates, and chlorides. Any
combination of these cations, and anions form the salts or
"salinity" of irrigation return flows.
A basic process by which irrigation return flow
elevates the salinity of a hydrologic system with which it
is in contact is termed salt loading. This process
increases the total salt burden of the receiving waters by
adding salts. A second process is concentration, in which
the salinity of a water body or hydrologic system is
increased by evaporation. Evaporation merely reduces the
amount of water but does not reduce the total quantity of
11
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dissolved salt. Return flows may be aggravated by non-
associated sources of pollution as natural salt flows,
mining, and oil field operations. Additional sources
including municipal, commercial and industrial waste
discharges, together with runoff from urban, construction,
highway and agricultural sources may augment return flow
salinity.
low
Return flows originate from both surface and subsurface
sources. Surface sources include bypass water, tailwater
(wastewater) , and the incidental source, precipitation.
Bypass water is that diverted for irrigation but returned to
the source without having been applied to the land.
Tailwater is the excess remaining after an irrigation and is
hopefully retained in ditches or in ponds. The subsurface
source is water which has percolated through the soil
profile. This water finds its way either to the zone of
ground water saturation or to the stream through artificial
drains or by shallow diffuse seepage (non-point sources)
along the stream bank.
Excessive application of irrigation water often results
in tailwater losses as shown in Figures 2 and 3. If
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movement of the runoff is excessive, serious erosion may
occur and valuable topsoil lost (Figures 4-7)
Runoff may have high turbidity imparted by sediment.
Eroded soil particles may transport adsorbed contaminants
such as pesticides, fertilizers, and organic material.
Tailwater is exposed to other pollutants and may contain
non-adsorbed pesticides that were applied directly to the
soil or washed from the plant by rainfall or sprinkler
irrigation. Soluble fertilizers, soil amendments, animal
wastes and organic constituents may also be found among
tailwater pollutants. Evaporation accounts for further
concentration of dissolved contituents. Finally, excessive
application may cause a significant rise in temperature
resulting from storage in pools, canals, laterals and
ditches (4) .
Bypass water ordinarily acquires relatively little
additional contaminant inasmuch as it represents water
routed through conveyance canals and ditches and which is
returned directly to the stream without having been applied
to the land. It too, is subject to concentration through
evaporation and may be consumptively used.
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*&»*'
\
FIGURE 2. Destructive effect created by excessive
amount of tailwater being lost from field
having too steep a grade for efficient irrigation.
Hudspeth County, Texas. Photo courtesy Soil
Conservation Service, U.S. Dept. of Agriculture.
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- x.4.
. ,_ . -. r .
FIGURE 3. Execessive amount of tailwater being lost
from irrigated field. Note water flowing
across highway. Hudspeth County, Texas. Photo cour-
tesy Soil Conservation Service, U.S. Dept. of Agricul-
ture.
15
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*_ . «?«- -
, v;, -
(!«
" ' I '1.1
.'.'v
FIGURE U. Considerable erosion caused by excessive
irrigation on light sandy soil. Gully depths
are greater than two feet. Near Caldwell, Idaho. Photo
courtesy Soil Conservation Service, U.S. Dept. of
Agriculture.
16
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FIGURE 5. Erosion caused by excessive irrigation.
San Diego County, California. Photo cour-
tesy soil Conservation Service, U.S. Dept. of Agriculture.
17
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'
*-
*
^
' ~
y
c;_ -
%^1
:.:,/^X -"*4A''
' "-»"*V%»f "^S-'
- .'"^**x"'- _",
' - - *v *f^..
FIGURE 6. Serious water erosion caused by excessive use
of irrigation water on too steep slopes.
Approximately 75 percent of the topsoil was lost in one
irrigation. Fremont County, Wyoming. Photo courtesy
Soil Conservation Service, U.S. Dept. of Agriculture.
18
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FIGURE 7. Irrigation waste water erosion on a culti-
vated field. Morrill County, Nebraska.
Photo courtesy Soil Conservation Service, U.S. Dept. of
Agriculture.
19
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The applied water which percolates into the subsurface
plays the major role in the life-sustaining drama of the
irrigation event. Normally, it is also the greatest
contributor to pollution in return flows. A part of the
water is stored in the root zone where it is used
consumptively by crops. The plant uses the pure-water
fraction of root-zone moisture and the remainder is left
with an elevated mineral (salt) and soluble nutrient
concentration. That water not retained in the root zone may
continue to percolate downward, continuously acting as a
mineral solvent or leaching agent. It may then move
laterally to seepage areas, be collected by artificial
drains, or ultimately find its way into the ground water
system. The percolating fraction of applied water increases
the concentration of salinity in the return flow. This
increase is inevitable and is an inherent part of the
irrigation scheme that must be recognized by agriculturist,
hydrologist, engineer and environmentalist alike. The
concentration of mineral salts in irrigation return flow
from both leaching and evapotranspiration may range from
three to ten times that of the applied water.
20
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§§i£ Accumulation in the Soil
The introduction of irrigation into the field of
agriculture on a large scale has had the effect of diverting
salt to the soil. This is salt that, in previous years, had
been dedicated by nature to the oceans. Through irrigation,
salt is being intercepted enroute to its time-honored
destination, placed upon and through the soil mantle,
concentrated by evapotranspiration and leaching, and
returned to the stream. This series of events may take
place many times in a single river basin or stream prior to
discharge. Each use results in increased concentration and
the cumulative effect is the magnification of a normal salt
content several times that expected under non-irrigating
waterway conditions (5).
Accumulations of salt in irrigated soil must be avoided
inasmuch as the land would soon become too saline to support
plant life. If normal rainfall cannot flush the salt from
the root zone, excess water must be applied during regular
seasonal irrigations to prevent buildup. The excess
represents the "leaching requirement" necessary to prevent
salt accumulation above a prescribed level. Failure to
maintain the level can become a limiting factor to further
agricultural development in a given area. The increased
application of water to achieve a proper leaching
21
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requirement could result in waterlogging the land. The
imbalance, if it occurs can be corrected by providing
adequate drainage. Returns collected in drainage systems
may be highly saline.
22
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PROBLEMS ASSOCIATED WITH EXCESSIVE SALINITY
The degradation of water quality caused by increased
salinity may have far-reaching, accumulative effects on
subsequent beneficial use. The use to which water is put
determines the level of quality required. A particular
quality may have a detrimental effect on a specific use.
High quality water is required for municipal use and for
many industrial purposes. The effects of moderate increases
in salinity on the well-being of adult aquatic animals may
be minimal. However, spawning of certain fish species may
be impaired by salinities in the range of 500 milligrams per
liter, or even less. Ascertaining water quality
requirements for aquatic life may be difficult inasmuch as
different species vary widely in their tolerence to salinity
and other dissolved substances during various life stages.
For other uses salinity levels can be moderately high and
not be particularly detrimental. Among these are water
skiing, swimming, boating and hydroelectric power generation
and some commerical applications.
Water is ordinarily categorized in terms of its
suitability for municipal, industrial, agricultural, and
recreational uses. Some specialized industrial uses such as
pharmaceutical, food processing, textile manufacturing, and
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laundering are often particularly sensitive to specific
dissolved elements in very low concentrations. The
projected industrial growth and expansion of any area or
municipality may be limited by the quality qf the available
water supply. Industries critically examine additional
costs involved in treatment necessary to upgrade water
quality at prospective plantsites. These secondary costs
may be an important factor in determining the establishment
of highly desirable industries in areas that are otherwise
ideally situated with repsect to terrain, fuel, labor,
climate and accessibility.
Domestic Use
The use of water that is of direct personal concern to
the domestic consumer includes drinking, food preparation,
laundering and personal hygiene among the most important.
Water high in dissolved solids may damage ornamental shrubs,
trees and lawns. It can also be detrimental to water- us ing
home appliances. Water high in calcium and magnesium salts,
termed "hard", can cause scaling in hot-water heaters,
pipes, boilers, air-conditioning equipment and significantly
shorten their life. The salts of calcium and magnesium,
unless eliminated by softening, leaves scums, crusts, curds
and rings on household utensils and fixtures They also
cause yellowing of fabrics and toughen vegetables during
24
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cooking. Hard water requires excessive amounts of soap and
detergent, adding appreciably to household expense. If the
water contains excessive chlorides and sulfates, corrosion
may replace scaling as the undersirable mechanism. Salts of
these ions are more difficult and more expensive to control.
The U.S. Department of Health, Education and Welfare,
Public Health Service, has published standards applicable to
drinking water and water supply systems used by public carriers
and other subject to Federal quarantine regulations. The recom-
mended upper limit of total dissolved solids is placed at 500
parts per million (6). The National Technical Advisory Sub-
committee on Public Water Supplies in its report to the Secretary
of the Interior, has expanded upon the Public Health Service's
Regulations with respect to drinking water standards. The
Subcommittee prepared an in-depth review and reported its findings
and recommendations regarding water quality for Recreation and
Aesthetics; Public Water Supplies; Fish, Other Aquatic Life and
Wildlife; Agricultural uses including Farmstead Water Supplies,
Livestock and Irrigation; and Industry (7).
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A severe municipal water salinity problem caused by
irrigation return flows recently occurred in the Lower
Colorado River. Saline water in an aquifer underlying the
We11ton-Mohawk Irrigation District near Yuma, Arizona is
drained by a series of large-capacity wells drilled to
control the water table (8). The discharged effluent
greatly increased the salinity of the Colorado River at
Yuma. The company that supplied domestic water to the city
had to abandon its intake structures in the river and obtain
potable water by diversion at Imperial Dam, approximately 15
miles upstream. Downstream users in Mexico, however, had no
alternative source of supply and the salinity of the
Colorado River flowing into Mexico is the subject of
international negotiations (9).
Effect on Agriculture
Salinity created by irrigation generates additional
problems for the downstream user. Saline water may increase
the salinity of the root zone environment of the soil.
Elevation of soil salinity may inhibit seed germination,
reduce crop yields and prevent the growing of crops having
low salt tolerances. In extreme instances, salt buildup may
even cause the removal of land from agricultural production
(Figure 8). Production of vegetable crops having low salt
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vx,
. ;
'
-. -.-.'.
FIGURE 8. Citrus grove abandoned as a result of
build up of salt in the soil.
Coachella Valley, California. Photo courtesy
Bureau of Reclamation, U.S. Department of the
Interior.
27
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tolerances such as celery, beans, lettuce, carrots and
cabbage, together with melons and practically all citrus
fruits could be greatly reduced by soil salinity buildup
(Figure 9) . These are high-value crops which contribute
substantially to the economic well-being of the grower.
Other money crops such as sugar beets and flax have suffered
damage from excessive soil-salinity (Figures 10 and 11).
Water quality criteria for irrigation and general
agricultural purposes have been developed by the Federal
Salinity Laboratory Staff (10). These cover a wide range
and are closely interrelated with soil texture, infiltration
rate, drainage, climate and crop salt tolerance.
As the salinity of applied water increases, a larger
quantity is ordinarily needed to prevent salt buildup in the
root zone. In some soils continued irrigations using
limited amounts of water only that necessary to maintain
field capacity -- will invarably induce salt concentration.
The buildup can progress to the stage where it adversely
affects the surface and greatly inhibits plant growth,
creates large "kill" areas and may ultimately result in the
abandonment of much land (Figure 12).
Many soils in their natural (virgin) environment are
highly mineralized and may be either sodic or saline. Sodic
28
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FIGURE 9. Salt damage to carrot crop, Coachella
Valley California. Photo courtesy
Bureau of Reclamation, U.S. Dept. of the Interior.
29
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FIGURE 10. Sugar beets growing sparsely along
salt-encrusted ridges between ir-
rigation furrows. Irrigation water containing salts
rose to the ridge surface through capillary action
and evaporated, leaving the solids behind.
Photo courtesy Dept. of Water Resources, State of
California.
30
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FIGURE 11. Salt buildup in soil results in exten-
sive damage in this flax field as shown
by the bare areas. Imperial County, California.
Photo courtesy Soil Conservation Service, U.S. Dept.
of Agriculture.
-------
FIGURE 12. Aerial view of irrigated farmland south-
west of Roll, Arizona. Standing salty
water and saline soils resulted in a loss of approx-
imately 1000 acres of crops. Photo courtesy Bureau
of Reclamation, U.S. Dept. of the Interior.
32
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soils have a high exchangeable sodium ion content whereas
saline soils may contain excessive concentrations of soluble
salts other than, or in addition to, exchangeable sodium.
Both soil types require special management practices,
particularly when irrigated and subject to leaching,
inasmuch as the high concentrations of mineral constituents
impair their productivity (10). Leachates from these soils
may contribute significantly to return flow salinity. It is
estimated that salt-affected soils comprise about 28 percent
of all irrigated acreage in the Western states.
Excess water applied to the land to control root zone
salt must be removed or the land may become waterlogged as
the water table rises. Measures to control the elevation of
the ground water table require drainage systems which in
turn requires high capital investments on the part of the
irrigator. An example is the region in southern California
served by the Imperial Irrigation District and covering
553,000 acres (223,800 hectares). Facilities to drain
saline irrigation return flows in the Imperial Valley have
required the construction of approximately 1375 miles (2210
kilometers) of open drainage ditches and nearly 18,000 miles
(28,960 kilometers) of subsurface drainage tile in an effort
to maintain a favorable salinity balance in the soil (11).
Current capital costs to install subsurface tile average
$2450 per mile. The elaborate drainage system, designed to
33
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maintain a favorable salt balance in the root zone, is
needed because of a predominance of clay and heavy loam
soils which impede downward percolation of water and
encourage salt buildup in the shallow zone. Estimated
capital costs of pipe or tile drainage systems ranges from
$150 to more than $100 per acre, depending on the depth and
spacing of the pipe (12). Avoidance of soil salinity
buildup and potential reduction of crop yields obviously
requires large capital outlays by the irrigator.
Philosophically, detriments associated with water
degradation are fundamentally economic. Any increase in
salinity results in an economic penalty inasmuch as
additional water is required for equivalent benefit (13).
If water is degraded, the user must either apply more
water to the field to maintain crop yield or use the same
amount of water and risk a decrease in yield. If more water
is required for leaching or to maintain salt balance, the
cost of water rises, installation of artificial drains may
be necessary, soluble fertilizer requirements may be
increased, labor costs may rise, and the danger of soil
damage resulting from sodium hazard may increase, if
additional water is not available, the irrigator may have to
34
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turn to more salt-tolerant crops. In any event, the loss is
an economic one.
Direct adverse effects to the plant from increased
salinity are; reduction in osmotic action, decreasing water
uptake capability, and possible adverse metabolic reaction
with resultant toxicity. Indirect adverse effects may
include impairment of surrounding soil structure. This in
turn may reduce permeability, porosity, and water
infiltration capability.
35
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LOCATION OF MAJOR PBQBLEM AREAS
Water quality problems of some type and magnitude exist
in every irrigated area of the nation. These vary both in
intensity and kind of pollutant involved. The most severe
return flow problems are found in the conterminous Western
States (See Plate I). Soils in these arid and semi-arid
regions are ordinarily high in residual mineral salts
inasmuch as they have not been subjected to extensive
leaching by rainfall or snowmelt as have those in the more
humid parts of the nation. The soil profile developed in
sub-humid and humid regions is thick and relatively free of
readily-soluble minerals.
There are several areas in the United States
categorized by agricultural, soil, irrigation and ecological
authorities as those in which water quality problems
associated with irrigation return flows are serious.
The Colorado River Basin probably contains more major
salinity problem areas than any other in the nation. It is
closely followed by the Imperial and Coachella Valley of
Southern California, the Rio Grande Basin of New Mexico,
Texas and Mexico, and the great Central Valley of California
#
which contains the agriculturally important San Joaquin and
36
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SIGNIFICANT IRRIGATION AREAS
IN THE
SEVENTEEN WESTERN CONTERMINOUS STATES
'"Vc
Yaklma River Valley^
fc°o,
NORTH DAKOTA
Cx,C
If,
'0*/V
'/-q
-sa,
San Joaquln Valley
Coachella Valley
Salton Sea
Imperial Valle
Lower Colorado River Basin Rlncon-Mesllla Valley
IRRIGATED AREAS
Lower Rio Grande Valley
400
PLATE I
330
KILOMETERS
37
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Sacramento Valleys. These , together with several
additional, but less serious, areas are reviewed.
Colorado
The Colorado River heads on the east slope of Mt.
Richthofen in the northwest part of the Rocky Mountain
National Park, about 70 miles (113 kilometers) northwest of
Denver. The river then flows west by south into the Gulf of
California 1450 miles (2330 kilometers) distant. The
Colorado and its tributaries drain an area of approximately
255,000 square miles (582,750 square kilometers) or about
one-twelfth of the area of the conterminous United States.
It is unique among the great waterways of the world in that
its flow is completely "captured" by a series of large
reservoirs. Among these are Lake Havasu, Mohave, Mead,
Powell, Flaming Gorge, Fontenelle, Navajo, Morrow Point and
Blue Mesa (14). The most acute problem facing future
development of water resources in the Colorado River Basin
is salinity.
The basin is divided into an Upper and Lower Region by
the Colorado River Compact of 1922. The Upper Region
contains 113,496 square miles (293,955 square kilometers)
located upstream from Lee Ferry, Arizona. Irrigated
agriculture, a major industry, utilized 1,621,500 acres
38
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(656,220 hectares) of farmland in 1965 of which 99 oercent
were irrigated entirely from surface sources - the balance
being supplied by ground water (15).
The total annual dissolved solids load (salinity)
reaching Lee Ferry, Arizona, during the period 1941-1966 is
placed at 8,155,000 tons (7,398,000 metric tons). Of this
amount, the estimated loads contributed by irrigated
agriculture ranged from 1,995,000 to 3,320,000 tons
(1,809,800 to 3,011,800 metric tons). This range,
representing a variance of 24 to 41 percent of the total
salt load points out a need to develop more accurate
prediction of salinity caused by irrigation return flows
(16) . It is further estimated that nearly 90 percent of the
total relative salt load from irrigated agriculture in the
entire Basin originates in the Upper Region.
The balance of the salinity in the River at Lee Ferry
is attributed to natural sources. These are both non-point
or diffuse, and point. The diffuse sources in both the
Upper and Lower Basin are the most significant.
The Lower Colorado River Basin Region lies downstream
from the Lee Ferry division point and contains 141,137
square miles (365,545 square kilometers). Approximately
1,200,000 acres (485,640 hectares) of Lower Basin farmland
39
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were irrigated in 1965 under both organized irrigation
systems and privately- owned wells pumping from river
aquifers. Of the total, approximately 895,000 acres
(362,210 hectares) were located in the important Gila River
Subregion (17) .
It is estimated that only 12 percent Of the total
relative salt load from irrigated agriculture in the entire
Colorado River Basin originates in the lower portion.
Colorado River Basin Region
The Grand Valley irrigated agriculture area located in
the valley of the Colorado River both upstream and
downstream from its confluence with the Gunnison River in
western Colorado is the most serious salinity problem area
in the Upper Basin. Deep percolation from excessive amounts
of applied water, plus leakage from old canal and ditch
distribution systems in the Valley reaches the underlying
saline aquifer developed over the highly mineralized Mancos
Shale of Cretaceous Age. The excess water has elevated the
ground water table to the point where a substantial amount
of base flow is introduced into the Colorado River Channel.
This has added significantly to the salt load of the river.
The excessive amount of salt represents that dissolved from
the highly saline shale beds. It is estimated that 88,000
40
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irrigated acres (35,315 hectares) in the Grand Valley
contribute about 8 tons of salt per acre per year or a total
of 704,000 tons (638,655 metric tons) annually to the Upper
Basin. This is an estimated 18 percent of the total
irrigated agriculture salt load of the entire Colorado River
Basin! (13).
Deterioration of water quality in the Grand Valley
increased to the point where it became the target of several
special investigations funded, in part, by the Environmental
Protection Agency. Recent valley-wide land-use studies
indicated that almost 30 percent of the available
agricultural acreage in the valley has become unproductive
due to high water table and attendant salinity problems (18,
19, 20,21) .
Another major area of salinity created by irrigation
return flows is the Gunnison River - Uncompahgre River
Valley System in western Colorado south of Grand Valley.
The Uncompahgre Valley contains 6,000 acres (2430 hectares)
of irrigable land from which the salt yield is placed at an
estimated 4.5 tons per acre per year or a total contribution
of 27,000 tons (24,495 metric tons) annually. The valley of
the Gunnison River and its tributaries contain 167.000 acres
(67,585 hectares) of irrigated land, most of which is
underlain by the highly mineralized (gypsiferous) Mancos
shale and yields and average of 6.7 tons of salt per acre
41
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per year, or an annual total of 1,118,900 tons (1,015,045
metric tons) . The significance of applying irrigation water
to soils derived from highly mineralized bedrock becomes
readily apparent. The Gunnison-Uncompahgre complex accounts
for an estimated 29 percent of the total irrigation-
associated salt load of the entire Colorado River Basin.
The salt load of the combined irrigated area of the Grand
Valley and Gunnison-Uncompahgre Basins totals 47 percent or
almost one-half of the salt load from irrigated areas in the
entire Colorado River Basin. Their combined yearly salt
contribution to the Colorado River is about 1,850,000 tons
(1,678,000 metric tons).
Additional return flow problem areas in the Upper Basin
are located in the Green River Subbasin. Relative salt
loads from irrigated agriculture in the Subbasin contribute
an estimated 32 percent of the total salt load of the entire
Colorado River Basin. The Green River is the largest
tributary of the Colorado and drains parts of Wyoming,
Colorado and Utah. The river and its tributaries contain
numerous irrigated valleys, several of which have
significant salinity problems associated with irrigated
agriculture. Among the more important areas having return
flow problems are the Big Sandy Creek Basin in southwestern
Wyoming together with Ashley Valley and Duchesne Valley,both
in eastern Utah.
42
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The Big Sandy Creek Basin contains an irrigated area of
approximately 13,000 acres (5260 hectares) underlain by
highly gypsiferous, relatively soluble, sedimentary rocks
which, upon weathering, form the soils that support
agriculture in the basin. Irrigation return flows
contribute an estimated 5.6 tons (5.08 metric tons) of salt
per acre per year or a total of 73,000 tons (66,225 metric
tons) per year to the Green River System.
Ashley Valley, located in northeastern Utah, also
referred to as the Vernal Unit Area, has long been
identified with water quality deterioration imparted by
irrigation return flow salinity. The approximate 20,000
acres (8,094 hectares) of irrigated land in the Valley
contributed an annual salt load of 4.2 tons (3.8 metric
tons) per acre during the period of June 1965 to May 1966 or
a total of 84,000 tons (76,205 metric tons) to the Green
River. The predominant ion is sulfate leached from
gypsiferous soils. The Ashley Valley-Vernal locale, while
relatively small in areal extent, is intensely saline and
has been the subject of recent studies funded by the
Environmental Protection Agency and the Bureau of
Reclamation (22,23).
The Duchesne area of northeastern Utah contains 166,000
acres (67,180 hectares) of irrigated land, mostly
43
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concentrated in the valleys of the Uinta and Duchesne River
and their tributaries. Return flows contribute an estimated
three tons of salt per acre per year or about 498,000 tons
(451,775 metric tons) annually to the Green River System.
Irrigation in the Price River Valley cf northeastern
Utah, located about 60 miles (97 kilometers) southeast of
Provo^ is developed in soils derived from the Mancos shale.
Approximately 20,000 acres (8100 hectares) are under
irrigation and the total salt load attributed to return flow
could be as great as 8.5 tons (7.7 metric tons) per acre per
year or 170,000 tons (154,220 metric tons) annually.
Difficulty has been experienced in attempting to establish
the total quantity of salt assignable to return flows in the
Valley. The contribution of naturally-occurring salinity in
the area of ground water is known to be sizeable. Both
irrigation returns and ground water in the Valley owe their
excessive salt pickup to leaching of soils developed upon
the Mancos shale. The Mancos is an excellent example of an
off-repeated condition in arid lands in which a rock
formation, usually shale, is a valley-builder capable of
yielding gentle topgraphy well-suited to irrigated
agriculture but is at the same time capable of severely
degrading the quality of water applied to its weathered *
mantle (soil).
44
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Lower Colorado River Basin Region
Significant increases in salinity in the Lower Colorado
River mainstem occur in its reaches upstream from Imperial
Dam. This dam represents the southernmost point of
diversion of Colorado River water for irrigation in the
United States. Principal increases in salinity involving
return flows originate in the Parker Valley, nearly all of
which lies within the Colorado River Indian Reservation.
The valley contains about 110,000 acres (44,517 hectares) of
river flood plain of which 31,700 acres (12,830 hectares)
were irrigated in 1962. The Reservation has unused water
rights sufficient to irrigate an additional 67,500 acres
(27,320 hectares) which, if developed, will create a further
increase in the total amount of dissolved solids in the
downstream reaches of the river. The projected increase
will be the result of salt concentration by stream depletion
(17).
The Palo Verde Irrigation District located in the Palo
Verde Valley immediately downstream from the Colorado River
Indian Reservation contains approximately 85,000 acres
(34,400 hectares) under irrigation. The district
contributes a salt load of about two tons per acre per year
to the mainstem. Much of this is groundwater salinity
currently being withdrawn through deepened existing drains.
45
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The Colorado River emerges from mountainous terrain
fourteen miles upstream from Yuma, Arizona and is joined by
the Gila River. The floodplain immediately below the
junction is an important irrigated area. It widens
downstream from Yuma and merges with the Colorado River
delta system, a vast arable plain, which extends westward to
the Salton Sea Basin and south to the Gulf of California
(8). Agriculture, the mainstay of the area's economy is
made possible by irrigation with Colorado River water
diverted at the Imperial Dam located 26 miles (42
kilometers) upstream from the Northern International
Boundary with Mexico. This great diversion point supplies
the Yuma, Gila and Wellton-Mohawk irrigated areas in Arizona
and the Imperial and Coachella Valleys in California through
two major conveyances the Gila Gravity Main Canal into
Arizona and the All-American Canal into California. The
total annual diversion of water from the Imperial Dam into
the canals is approximately 6,000,000 acre-feet
(7,400,940,000 cubic meters). Water is also released at
Imperial Dam for delivery to Mexico under provisions of the
1944 Treaty with that country. Summarizing, most of the
Colorado River water used in the United States is diverted
at the Imperial Dam.
The major irrigation return flow salinity problem in
the Lower Colorado region is that created by ground water
46
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pumped to control water levels beneath the Wellton-Mohawk
Irrigation District in the Gila River Valley. The pumped
water was originally discharged into the Colorado River
downstream from Imperial Dam. Past irrigation during the
early part of the century used ground water pumped from an
aquifer underlying Wellton-Mohawk and eventually increased
the salinity of the water to the point where it was no
longer usable. The increase in salinity is a classic
example of the combined effect of continued evapotran-
spiration of the applied water plus deep percolation of the
remainder (irrigation returns) to the aquifer from which it
was withdrawn. The irrigation water was, in essence,
continuously recycled. Inauguration of the Gila Project
revived irrigation in the Gila Valley. Subsequent
application of Colorado River water diverted at Imperial Dam
elevated the water table and the Wellton-Mohawk area became
waterlogged. Land reclamation required much larger
quantities of water than were originally anticipated. High
capacity withdrawal wells were drilled, beginning in 1955,
to control ground water levels. The quality of the effluent
discharged into the Gila River underwent severe
deterioration during the summer of 1961. During that year
returns from more than 60 wells in the Wellton-Mohawk Valley
were discharged into a wastewater conveyance channel (the
Wellton-Mohawk Main Outlet Drain) which emptied into the
Gila River. The problem was aggravated by greatly increased
47
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pumping rates and the development of additional wells. The
result was an alarming elevation of salinity in the Colorado
River immediately north of the international boundary. The
salinity trend has since reversed and the quality of
We11ton-Mohawk drainage has shown steady improvement. It
reached a maximum of 6,000 parts per million total dissolved
solids in 1961, then decreased to an average of 4,620 ppm
during the water year 1966 and to 4,100 ppm in 1969 (9,12).
The control of salinity of Colorado River water
reaching Mexico has been the subject of international
discussion and negotiation. Initial control measures
designed to reduce the salinity included the release of
additional water at Imperial Dam to provide dilution; the
elimination of several highly saline drainage wells in the
Wellton-Mohawk Project; and the construction of a concrete-
lined conveyance channel to divert undesirable saline
drainage to the Colorado River immediately downstream from
Mexico's Morelos Dam. Morelos dam is the point of diversion
of water for irrigation in Mexico's Mexicali Valley, a
southward extension of the Imperial Valley. The concrete-
lined conveyance channel was constructed in fulfillment of a
formal international agreement with Mexico and was placed in
service on November 16,1965. While the primary function of
the channel is to divert saline returns downstream of the
Morelos Dam, provision is made for directing the flow into
48
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the Colorado River either upstream from or downstream from
the dam if requested by Mexico.
The Imperial Valley
The Imperial Valley of California, located south of the
Salton Sea is a broad, flat plain flanked by low, barren
mountain ranges and is a part of an elongated desert valley
extending northward from the Gulf of California.
Physiographically, it is a segment of the Colorado River
delta fan tributary to the Salton Sea Basin (24). The
valley is a closed depression and represents the southern
part of the bed of ancient Lake Cahuilla. Most of its area
is below sea level.
The Imperial Valley is one of the most intensively
irrigated areas in the world. Agricultural production
depends entirely on water supplied from the Colorado River
through the Ail-American Canal. The average annual rainfall
in the region is about 3 inches (7.6 centimeters).
Approximately 475,000 acres (192,250 hectares) were
irrigated in 1971, yielding a gross value of agricultural
products in excess of $300,000,000.
-------
The control of salt buildup in Imperial Valley soils
caused by consumptive use of irrigation water requires
continual leaching and carefully controlled irrigation
management practices, particularly with respect to amount,
frequency and methods of water application. The physical
and chemical properties of the soils require additonal
management practices to prevent salt accumulation in the
plant root zone. The salts in the soil lend themselves
readily to leaching, and are composed principally of the
chlorides and sulfates of sodium, calcium and magnesium.
About 50 years ago it became apparent that drainage of
the valley soils was grossly inadequate. A rapidly rising
water table along with an alarming increase in ground water
salinity combined to seriously affect crop productivity.
Figure 13 illustrates land and crop damage associated with
high water tables in the Valley. The Imperial Irrigation
District initiated the installation of a series of open
drainage ditches to depress the water table and conduct
returns to the Salton Sea. Construction of a tile drainage
system to augment the surface drainage network and further
remove accumulated saline ground waters that threatened to
waterlog the valley began as early as 1929. Today there are
17,834 miles (28,695 kilometers) of tile drains serving more
than 377,000 irrigated acres (152,570 hectares) in the
valley. The type of tile drain used in the valley and the
50
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.
f
FIGURE 13. Here high water table prevents removal of
surface water after irrigation, resulting
in ponding of water and drowning of crop. Imperial
Valley, California. Photo courtesy Soil Conservation
Service, U.S. Dept. of Agriculture.
51
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method of discharge of collected irrigation return flows
into conveyance ditches are shown in Figures 14 and 15.
It is necessary to earmark about 20 percent of the
total irrigation water diverted to the Imperial Valley for
root zone leaching in order to achieve a condition wherein
the total annual quantity of salts removed is somewhat
greater than the total annual quantity introduced. Also, as
the salinty of the source water, diverted from the Colorado
River increases, the leaching requirement Will have to be
increased (27). Salt balance in Valley soils was initially
achieved in 1946 and has been maintained continuously.
Furrow irrigation is the water-application technique
used almost entirely in the Imperial Valley because of the
low infiltration rates and elevated soil salinities* The
more versatile and efficient sprinkler methods are seldom
used due to the relatively high concentration of salt in the
applied water coupled with the very high summer
temperatures. Rapid drying of saline water on the leaf
surface leaves a toxic concentration of salt and often
results in the death of the foliage (27).
Irrigation return flows from the Imperial Valley amount
to approximately 900,000 acre-feet (1,110,140,000 cubic
meters)per year, all of which is discharged into the Salton
52
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FIGURE 11. Tile, gravel and sights placed ahead of
construction on an irrigated farm in the
Imperial Valley, California. The tiling operation is
engineered and constructed by the Imperial Irrigation
District Engineering Department. Photo courtesy Soil
Conservation Service, U.S. Dept. of Agriculture.
53
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/
FIGURE 15. Typical discharge of tile drain designed to
lower the water table beneath irrigated land.
Tile drainage commonly discharges into open collection
ditches for ultimate disposal in this instance into
the Salton Sea. Imperial Valley, California. Photo
courtesy Soil Conservation Service U.S. Dept. of Agriculture.
-------
Sea and represents 90 percent of the total annual inflow
into that body.
The^Coachella Valley
Irrigation return flow problems in the Coachella Valley
are similar to those in the Imperial Valley. The Coachella
Valley is an intermontane, linear depression located
immediately north of the Salton Sea and represents the
northern part of the elongate alluvial limb of the Colorado
Desert which extends northwestward from the Gulf of
California. A portion of the Valley is located within the
downstream segment of the Whitewater River Basin and is
flanked by the Little San Bernardino Mountains on the
northeast and the Santa Rosa Mountains on the southwest.
The southern part of the Valley is the bed of ancient Lake
Cahuilla which now contains the recently-formed Salton Sea*.
*The present Salton Sea was formed during 1905-1907 when more
than 16,000,000 acre-feet (19,735,840,000 cubic meters) of
Colorado River water poured through several breaches in the
river levee system and flowed westward into the Salton
Trough.
55
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Coachella Valley is one of the few areas in the United
States where select date palms can be successfully grown.
An experimental station was established by the government in
1904 to study and develop date palm culture in this country.
Choice date palm varieties were imported from Egypt and
Algeria and irrigated groves established (24). The
production of dates now represents an important aspect of
the economy of the Valley. (Figure 16).
Ground water resources were developed early in the
agricultural history of the Coachella Valley. As water
levels declined, Colorado River water was imported into the
area, beginning in 1948, through the Coachella Branch of the
All-Americah Canal. The availability of ample water,
accompanied by expanded irrigation activity, resulted in the
development of a shallow, perched ground water body. The
installation of tile drainage designed to combat the high
water table began in 1950 and continues. More than half of
the 60,000 irrigated acres (24,280 hectares) in the valley
which overlie areas of restricted ground water movement have
been tiled. Salt balance studies indicate that the annual
tonnage of salt in the return flows exceeds that applied
during irrigation (28) . The leaching fraction of the
Coachella Valley is approximately 30 percent. Continued .
high water requirements for leaching will have to be
56
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FIGURE 16. Grove of heavy-laden date palms near
Indio, California in the Coachella Valley.
The Valley is one of the few areas in the United States
where the date palm thrives. Photo courtesy Bureau
of Reclamation, U.S. Dept. of the Interior.
57
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maintained. Return flows from the Valley amount to about
100,000 acre-feet (123,349,000 cubic meters) annually and
are discharged into the Salton Sea.
Irrigation return flows from the combined Coachella and
Imperial Valleys literally control the quantity, quality,
and related problems of the Salton Sea inasmuch as the total
annual inflow into this body of water is composed almost
entirely of irrigation returns. Saltwater sport fish were
introduced into the Salton Sea when its salinity reached
approximately 35,000 ppm or that of the oceans. Its
salinity is currently about 37,000 ppm and rising, which
means that sport fishing and associated recreation may soon
terminate if the salinity increase is not arrested.
Reduction of salinity can be accomplished by augmentation
with fresh or low-salinity water. This, in turn would
involve either importation from out-of-basin sources,
desalination of all or part of the return flows or other
costly approaches (29). Costs involved in desalting a
portion of the Coachella drainage waters were studied
recently by the Office of Saline Water and the Bureau of
Reclamation (30). Cost estimates, based upon 2870 ppm
feedwater and 400 ppm product water, ranged from $220 to
$297 per acre foot, using electrodialysis and multistage ,
flash distillation respectively.
58
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The Rio Grande Basin
The Rio Grande Basin is divided into four geographical
segments for purposes of water-use discussions. These are
the Upper Basin, Middle Basin, Lower Basin and the Pecos
River Subbasin. The Rio Grande River begins in southwestern
Colorado on the east flank of the San Juan Mountain range
and flows approximately 1,900 miles (3,057 kilometers) south
and east into the Gulf of Mexico at Brownsville, Texas.
Upper Rig Grande Basin
The Upper Basin, located between the headwaters of the
river and Ft. Quitman, Texas, drains an area of about
32,000 square miles (82,880 square kilometers). Important
irrigated segments begin with San Luis Valley, located
adjacent to the headwaters of the river in south-central
Colorado. The valley is a down-faulted, relatively flat,
high-altitude depression bounded by the Sangre de Cristo
Mountains on the east and by the San Juan Mountains on the
west. Its northern part is a closed depression into which
surface drainage converges. The valley contains very large
amounts of surface and subsurface water. Estimated ground
water storage in the aquifer system underlying the valley is
placed at more than two billion acre-feet (2,466,980,000,000
cubic meters). This water is contained in several porous
59
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formations comprised primarily of extrusive rocks
represented by volcanic flows, tuffs, breccias and debris.
The thickness of this multiple aquifer may be as great as
30,000 feet (9,145 meters). The uppermost aquifer is
unconfined, extensive and contains water at depths normally
less than twelve feet. Recharge is chiefly from percolation
of applied irrigation water, leakage from canals and
ditches, and precipitation. Principal recharge to the deep
aquifer system is through infiltration from mountain streams
flowing across alluvial fans edging the valley.
Irrigation, dating to 1880, is vital to agriculture in
the San Luis Valley inasmuch as the average annual rainfall
is only eight inches. During the period 1880 to 1950 the
principal source of irrigation water was surface supplies
(31). Excessive irrigation returns waterlogged a part of
the valley in the early part of this century and a drainage
network was constructed between 1911 and 1921 in an attempt
to dewater the land but the problem created by the
excessively high water table remains, at least in part, to
this day-
Subirrigation is practiced in the San Luis Valley and
tends to aggravate the waterlogged condition. This method
4
of applying water is common is some areas of the United
States and can be highly efficient if water levels are
60
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carefully regulated. Subirrigation requires a high water
table, water in continuous supply, and controlled drainage.
The quality of the shallow ground water has
deteriorated as a result of mineral concentration caused by
comsumptive use and valley soils have been adversely
affected by significant alkali buildup.
Irrigation is also practiced downstream from San Luis
Valley in the middle section of the Upper Rio Grande Basin
between the Colorado state line and San Marcial at the head
of Elephant Butte Reservoir. Historically, irrigation was
practiced in this reach of the river during the Pueblo I and
Pueblo II eras, (700 to 1050 A. D.) and it is estimated that
at the time of the arrival of the Spanish in the 16th
Century, 25,000 acres (10,120 hectares) were being
irrigated. The first Spanish irrigation ditch was built in
1598 about 30 miles north of Santa Fe, New Mexico (32) . A
recent study of water usage on the Upper Rio Grande (33)
placed the total irrigated land in the middle section at
approximately 150,000 acres (60,705 hectares). Consumptive
ground water losses in the section are particularly high as
a result of phreatophyte usage.
This reach of the river is served by several
conservancy and irrigation districts, some organized as
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early as 1915, and numerous community ditch systems.
Agricultural production is confined chiefly to small
subsistence-type farms. The main products are fruits,
garden vegetables, hay, forage crops and cotton. Irrigation
return flow problems are beginning to receive attention in
this area and several significant investigations are in the
planning stage.
Middle Rio Grande Basin
The Rincon and Mesilla Valleys lie along a 108 mile
reach of the Rio Grande River in the Middle Basin between
the Caballo Dam in New Mexico, and El Paso, Texas. The
Rincon Valley contains about 15,000 irrigated acres (6070
hectares) and the Mesilla Valley about 70,000 irrigated
acres (28,330 hectares). Salinity studies conducted over a
period of 20 years by Wilcox (34), indicated an increase of
272 ppm, due almost entirely to the effect of salt loading
resulting from irrigation return flows in the Rio Grande
River between the Caballo Dam and El Paso. Water quality
deterioration in the Rincon and Mesilla Valleys has been
accelerated by the increased consumptive use of ground water
for irrigation brought about by the drought of 1951 to 1957
when a critical surface water shortage existed. More than
#
1700 water-supply wells were completed in the alluvial
aquifer during this period. Today approximately 42 percent
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of the water used in the Rincon and Mesilla valleys is
supplied by wells. The average salinity of water taken from
a representative group of these wells indicates that the
ground water is considerably more saline than that in the
river (35). There is little doubt that the salinity of both
ground water and the river will continue to increase as a
result of use and reuse together with attendant
concentration through evapotranspiration. The effects of
the deterioration of water quality will be increasingly
reflected in damage to valley soils.
The overall efficiency of irrigation in the Rincon-
Mesilla Valley ranges between 40 and 50 percent. Re-stated,
this means that as much as one-half the applied water is
lost by deep percolation. The quality of the percolating
water is seriously degraded as it passes downward to the
water table. Experimental research is currently underway to
reduce the amount of return flows through more efficient
application of water to the land. The effects of trickle or
drip irrigation on water use efficiency in the area are also
under investigation (35).
The quality of water in the Rio Grande River,
aggravated by irrigation returns, is of particular
importance to the cities of El Paso and Juarez. Both are
growing rapidly and long-term projections indicate that
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their municipal and industrial water needs may eventually
require the entire river flow. Pumpage for municipal
purposes accounted for about 56 percent of the water used in
1960 and the ground water source which receives its recharge
from the river will continue to be relied upon to produce
the major part of future requirements.
The Lower Rio Grande Basin includes the downstream
drainage area between Ft. Quitman, Texas and the Gulf of
Mexico. The river marks the International Boundary between
the United States and Mexico throughout this reach and is
joined by several important tributaries originating in both
countries. Among these are the Pecos and Devils Rivers in
the United States and the Rio Conchas, Rio Salado and the
Rio San Juan in Mexico.
The principal irrigated area in the United States lies
in Hidalgo, Willacy, and Cameron counties in the Lower Rio
Grande Valley. The gross value of Valley agricultural
products is about $100,000,000 per year.
The fertile lands of the Lower Rio Grande Valley are
*
dependent upon water from the river for irrigation.
However, this source is supplemented during drought periods
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from about 1500 irrigation wells capable of providing an
additional 2,200 acre-feet (2,713,680 cubic meters) daily.
Poor quality of the return flow limits the use of drainage-
canal water but this source is also used as a supplemental
supply during periods of serious drought. Drainage water
from the Texas side of the Rio Grande is not returned to the
river but is diverted to the Gulf of Mexico through the
Laguna Madre.
The irrigated area is essentially deltaic, relatively
flat, low-lying, and slopes gently to the northeast from the
Rio Grande River toward the Gulf of Mexico. There are few
natural channels for the removal of surface waters. The
surface drainage problem is so severe that much of the
surface runoff from Hidalgo County must flow overland
through Willacy County to reach the Laguna Madre.
Numerous underground drains have been installed but are
inadequate and have failed to keep pace with drainage needs.
The subsurface drainage problem is aggravated by over-
irrigation, excessive seepage from unlined irrigation
canals, undersized outlets, or even complete lack of
outlets, plus excessive water contributed by high intensity
storms and hurricanes (36). Periodic hurricane-associated
floods may inundate the land for days or even weeks.
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This impairment of subsurface drainage is reflected in
surface drainage deficiencies. Surface drainage ditches
lack depths sufficient to adequately lower the ground water
table. Additionally, they are overloaded, suffer from
improper maintenance, structural deterioration, and lack
adequate outlets. Numerous surface obstructions such as
roads, railroads, highways, canals, and drainways restrict
runoff and further aggravate the problem. Frequent
waterlogging of a significant portion of the valley creates
serious problems involving ground water salinity and salt-
laden soils.
The Comprehensive Study and Plan of Development, Lower
Rio Grande Basin, Texas (36) states that the valley contains
690,000 acres (279,245 hectares) of irrigable land having a
high water-table problem and, of this amount, 655,000 acres
(265,080 hectares) have attendant salinity problems. It is
estimated that crop yields are currently being reduced at
the rate of 10 to 15 percent by excessive salinity and in
some areas croplands may have to be removed from production
- a condition that will progressively worsen with time if
remedial steps are not taken. The drain waters frequently
contain domestic sewage, untreated cannery and other food
processing wastes, phosphates, pesticides, organic residues,
bacteria and silt. At periods of low flow the chemical and
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bacteriological quality of the irrigation returns is very
poor
The Pec os River is the principal tributary of the Rio
Grande River in the United States. Approximately 200,000
acres (80,940 hectares) of agricultural lands are being
irrigated in the Pecos River Basin in New Mexico. Of this
amount, about 40,000 acres (16,190 hectares) are being
irrigated using surface water; 125,000 acres (50,590
hectares) using ground water and 35,000 acres (14,165
hectares) using combined sources. Principal crops in the
Basin are cotton and alfalfa. Secondary crops are grain
sorghum, barley and wheat. The average yearly consumptive
irrigation usage ranges from 0.85 to 1.8 acre- feet per acre
(2625 to 5550 cubic meters per hectare).
It has been stated that "For its size, the Basin of the
Pecos River probably presents a greater aggregation of
problems associated with land and water use than any other
irrigated basin in the United States. ..." (37) . Salinity
problems are particularly acute and irrigation return flows
add significantly to the dissolved solids content of the
river, principally in the Middle and Lower sub-basins in New
Mexico and Texas. Very heavy growths of phreatophytes and
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other vegetation plus saline loads from salt springs and oil
field brines combine tc further deteriorate water quality.
Studies to date regarding Pecos Valley return flow problems
are rather generalized and sparsely documented. However,
programs looking toward solutions to the problem of water
quality deterioration in the Pecos Valley are in the
planning stage.
Central^ Vail ey_Basj.nt_Calif2£nia
The Central Valley Basin of California constitutes the
largest irrigated area in the United States and is not
without its share of water quality problems resulting from
irrigation return flows. The valley is in the form of a
northwest trending, elongate bowl, bordered by mountains.
The lone outlet is a gap on the west in the San Francisco
Bay area through which the Sacramento and San Joaquin Rivers
discharge to the Pacific Ocean. The Basin is roughly 500
miles (805 kilometers) long and 120 miles (195 kilometers)
wide and constitutes more than one-third of the entire area
of the state. It contains about 10,000,000 acres (4,047,000
hectares) of cropland of which approximately 6,000,000 acres
(2,428,200 hectares) are presently under irrigation. The
Central Valley is roughly divided into three segments termed
the North or Sacramento Valley, the Middle or Delta area,
and the South or San Joaquin Valley.
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Sacramento Galley
The Sacramento Valley contains approximately 1,000,000
irrigated acres (404,700 hectares). Among important crops
produced is rice. This cereal grain represents a major
commodity and its cultivation is carried out using modern
methods. Aerial techniques are used to seed presprouted
rice and to apply pesticides and fertilizers. (Figures 17
and 18JL The quality of the applied water is very good.
Deterioration is largely caused by excessive nutrients
(nitrates and phosphates) and pesticides, with only nominal
problems associated with salinity. During the early period
of development of irrigated agriculture in the Valley, water
was obtained from wells but in recent years surface supplies
have been rapidly replacing subsurface sources. Development
of additional water resources has brought about increased
irrigation and attendant drainage problems associated with
high water tables created principally by excessive water
application. It is estimated that approximately 50,000
acres (20,235 hectares) are affected in this manner in the
Sacramento Valley (27).
Sacramento-San Joaquin Delta
The Delta area, also known as the Delta Lowlands,
contains 738,000 acres, (298,670 hectares) of which more
69
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'>' aSH*
FIGURE 17. seeding of presprouted rice using air-
craft. Photo courtesy Soil Conservation
Service, U.S. Dept. of Agriculture.
70
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FIGURE 18. Application of pesticide by aerial
crop spraying. Photo courtesy Bureau
of Reclamation, U.S. Department of the Interior.
AWBERC LIBRARY U.S. EPA
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than 500,000 acres (202,350 hectares) are in irrigated
agriculture. The Delta is located at the confluence of the
Sacramento and San Joaquin Rivers and is one of the most
productive in California.
The Delta is unique inasmuch as a significant amount of
its cultivated acreage lies below the level of the Delta
channels and the water must be siphoned over the channel
levees into deep drainage ditches where irrigation is
accomplished by capillary movement upward from the water
table into the plant root zone. Salts accumulate in the
root zone and must either be removed or reduced to non-toxic
levels. This is accomplished by periodic leaching, usually
during the winter months, and the saline return flows
discharged to the channel system.
San^Jgaguin Valley
The San Joaquin Valley contains over 7,000,000 acres
(2,832,900 hectares) of irrigable land of which slightly
less than 4,000,000 (1,618,800 hectares) are currently
developed. Of this amount, 2,700,000 acres (1,092,690
hectares) are located in the Tulare Lake Basin at the
southern end of the valley. The importance of the San
Joaquin Valley as an agricultural province is readily
apparent when it is realized that the valley contains about
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40 percent of the irrigable land of California. Rapid
expansion of irrigation in the San Joaquin segment of the
Central Valley was stimulated by construction of the
California State Water Project, the Federal Delta - Mendota
Canal, and the San Luis Project,
Salinity of irrigation returns is significant in the
valley. Additionally, and of great importance, is the high
nitrate content, the source of which is inherent in the
soil. The total solids content of irrigation water supplied
from the Sacramento River system ranges from 500 to 700
parts per million. Severe degradation of quality resulting
from concentration through consumptive use and leaching of
natural salts, including nitrates and boron compounds from
the soils by deep percolation, has occurred and is
progressively worsening. The salinity of some returns has
reached 20,000 ppm (27). Deterioration of water quality is
often accompanied by high water tables in areas where
subsoil permeability is restricted and irrigation is
intensive. Extensive damage to crops and soil has occurred
as a result of these factors. Tile drains have been
emplaced beneath 34,000 acres (13,760 hectares) in an
attempt to alleviate the problem. It is estimated that the
amount of acreage actually benefited is much greater
inasmuch as the drainage network intercepts subsurface water
from adjacent and upslope areas (38). Plans call for
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construction of a massive complex of tile drains beneath an
additional 300,000 acres (121,410 hectares) of valley land. ,
The effluent from the drainage system is either
returned to the San Joaquin River or recycled into the canal
delivery system. The discharge of the returns into the
river poses a serious threat to the ecology of the San
Francisco Bay system. The most troublesome pollutant is
nitrate. Construction of the San Joaquin Master Drain, a
joint U.S. Bureau of Reclamation and California Department
of Water Resources project designed to collect, transport
and discharge the highly saline and nitrate-charged
agricultural waters from the valley to the Sacramento-San
Joaquin Delta will aggravate the ecological problem.
Evaluation of the effect of the discharge on the quality of
Delta and Bay waters has been undertaken by the Central
Pacific Basins Comprehensive Water Pollution Control Project
of the Federal Water Pollution Control Administration,
predecessor of the Environmental Protection Agency (39). An
additional study has been made by the California Regional
Water Quality Control Board (40) .. Proposed methods of
denitrification of Master Drain waters include both
bacterial, and algal productioniand harvesting (algae
stripping) . The study also considered desalination of the
*
wastewater to remove salts, including boron compounds.
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Summarizing, the vast San Joaquin Valley agricultural
province is beset by a complex set of return flow problems
including high concentrations of natural salts, toxic boron
compounds, excessive native (plus applied) nitrates, high
water tables and poor drainage conditions.
Yakima River_Basin^Washington
The Yakima River Basin, located in south-central
Washington, contains about one-half million irrigated acres
and is one of the most intensively farmed in the United
States. Five government-owned irrigation facilities plus
several privately-owned systems and districts serve the
Basin's water needs.
Ample supplies of water in the Yakima Valley during the
early days of irrigation resulted in the application of
large quantities to the land. Following a long history of
excessive irrigation, waterlogging of the soils occurred as
the ground water table rose and finally reached a point
where surface water accumulated in areas of inadequate
drainage. Evaporation of the ponded water left a toxic
concentration of salts both on the surface and in the
shallow root zone and large amounts of land were severely
damaged.
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Concentration of mineral salts^ in irrigation water
returning to the Yakima River system, particularly after
multiple diversions is caused principally by consumptive
use, leaching, and ion exchange. Return flow quality is
also affected to a significant degree in the basin by
nutrient application, erosion, and crop removal. A detailed
study of the return flow problem by the University of
Washington pointed to the excessive application of water as
the major source of deterioration of irrigation returns in
the Basin (4l). It is estimated that 6*6 acre-feet per acre
(20,350 cubic meters per hectare) are diverted to the
surface and, of this amount, about 4.25 acre-feet per acre
(13,100 cubic meters per hectare) are actually applied to
the land. The balance is lost in conveyance channels by
seepage, wastage of various forms, and evapotranspiration.
The study concluded, in part, that irrigation return flows,
both surface and subsurface, were the responsible factor in
influencing the overall water quality of the Yakima River.
It further concluded that excessive application of water was
instrumental in elevating the ground water table and
degrading ground water quality; that quality was lessened by
the addition of minerals and soluble nutrients to a degree
where the dissolved solids content increased approximately
five times that of the adjacent surface water; and, that
*
leaching and ion exchange were the mechanisms largely
responsible for the change in water composition.
76
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Crops irrigated with water affected by irrigation
returns in the valley were also heavily infested with
parasitic nematodes. Unusally high sediment loads, together
with attendant adsorbed fertilizers and pesticides are
common in Basin return flows and are often of greater
importance than the effects of salinity on water quality
deterioration. Excessive water application is responsible
for the high sediment loads. A. study of the effects of
sedimentation in the Basin's Roza Irrigation District has
recently been undertaken (42). Investigators found that
sediment concentrations in return flows, even under the best
current irrigation system management, failed to meet the
water quality standards established by the Washington State
Department of Ecology, the standards-setting agency.
Returns often contained turbidity values in excess of 400
JTU (Jackson Turbidity Units). State standards require that
turbidity, even in Class "C" waters not exceed 10 JTU over
natural conditions.
Snak e_Ri yer_ Basin^Idahg
Approximately 4,225,000 acres (1,722,000 hectares) are
being irrigated in the Snake River Basin of southern Idaho.
The Bureau of Reclamation estimates that an additional
6,000,000 acres (2,428,200 hectares) are potentially
irrigable. Both surface and ground water in Idaho are of
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high quality and suitable for irrigation purposes. Ample
supplies are available and water allotments in the Snake
River Valley are particularly high. They range from about
6.5 acre-feet per acre (20,500 cubic meters per hectare )to
nearly 13 acre-feet per acre (40,100 cubic meters per
hectare) in areas where a range of between 2 and 3.5 acre
feet per acre (6,175 and 10,800 cubic meters per hectare)
would probably satisfy most requirements. Surface erosion
and deep percolation are problems created by these excessive
applications and, while not serious at this time, will no
doubt become so when the Basin's irrigable lands are fully
developed (27) .
An evaluation of the effects of irrigation on water
quality in the Pacific Northwest has recently been completed
and provides a valuable insight into the problems of the
Snake and Yakima River basins (43).
Qther Ma1or Problem^Areas
The Missouri River Basin and the Arkansas-White-Red
River Basin are in need of detailed study. The upper
segment of the Missouri River Basin has several areas where
irrigation return flow problems exist but where significant
*
salinity increases in the stream system are not obvious
because of the diluting effect of ample water supplies.
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A study of diffuse or non-point irrigation returns
discharging into the North Platte River in Nebraska
immediately downstream from the Nebraska-Wyoming state line
indicated a 27 percent increase in the salinity of the river
during a period of low flow in 1964 (44). The actual range
in total solids varied from 509 ppm at the state line to 647
ppm at Bridgeport, Nebraska, a distance of 60 river miles
(97 kilometers). Even though the increase was nominal,
responsible authorities are concerned. Water taken from the
North Platte River is used for irrigating many thousands of
acres in Nebraska and its deterioration could impose serious
detrimental effects on the economy of the state.
Skogerboe and Law (27) recount examples of serious
irrigation return flow quality problems existing in several
states. Among these are high sodium concentrations in soils
near Riverton, Wyoming where the problem is so severe that
reclamation of once-irrigated lands is currently uneconomic
in many areas. Problems are also beginning to develop in
both North and South Dakota in lands underlain by highly
saline formations of very low permeability.
The areas cited are those for which there is documented
evidence regarding salinity imparted to water by irrigation
return flows. There are additional areas where water
quality deterioration caused by irrigation practices are
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important. The problems involved are similar to those cited
and include increases in salinity of the receiving water;
elevation of the ground water table to critical levels;
damage to the soil, surface and root zone; excessive erosion
and sedimentation; transfer of fertilizers and pesticides,
plus other water-degrading factors associated with irrigated
agriculture.
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REMEDIAL_AND_CONTROL_MEASURES
The control of salinity and other pollution caused by
irrigation return flow cannot be easily achieved. Control
methods include the application of current technology and
the development of new technology. Current technology
includes known methods of increasing the efficiency of the
water development system, on-the-farm water management, and
elimination of surface discharges of irrigation waters.
These, combined with the application of irrigation
scheduling and increased water-use efficiency will minimize
pollution caused by irrigation returns. These methods and
procedures must be coordinated with a careful reevaluation
of the institutional measures affecting irrigation.
Ea£S_Water Delivery System
The water delivery system consists of conveyance
channels, beginning with major irrigation canals conveying
water from diversion points to the irrigation district or
farm system and terminating in the lateral distribution
network. Estimates of seepage losses from canal systems
vary from 13 percent in the Uncompahgre, Colorado area, to
48 percent in the Carlsbad, New Mexico Project. If 20
percent of all water diverted for irrigation in the United
States were lost by seepage (a conservative estimate), the
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total would amount to 24,000,000 acre-feet (29,603,760,000
cubic meters) per year based on current usage (27) . This
amount of water could irrigate an additional 8,000,000 acres
(3,237,600 hectares)or could be available as a diluent to
improve the quality of existing water supplies. Not only do
channel losses by seepage represent a potential waste of a
valuable resource but percolating waters may leach
additional minerals from the soil and further deteriorate
the quality of the return flows. The problem can be
alleviated or even eliminated by lining the canals and
ditches. A. study of the effect of lining irrigation
conveyance channels on the reduction of ground water and
stream salinity was undertaken as part of the Grand Valley
Salinity Control Demonstration Project(45). conclusions
drawn as a result of the study clearly indicated that
conveyance lining is a feasible Salinity control measure*
Conveyance channel lining is incorporated into all new
projects initiated by governmental agencies and is a proven,
effective deterrent to return flow water quality
deterioration. Lining materials may be compacted earth,
hard-surface, or membrane. The hard-surface linings include
Portland cement, concrete, mortar, asphalt cement, and soil-
cement. Such lining materials are used where structural
*
stability such as the prevention of canal bank failure or
velocity erosion in high-capacity delivery systems is
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necessary. The use of concrete head ditches results in
considerable saving of water, eliminates annual cleaning or
remaking earthen ditches and enables more efficient control
of water flow and distribution. Figures 19 and 20
illustrate the use of concrete in two methods of ditch
lining whereas the use of plastic lining in conveyance
channel construction is shown in Figure 21. An operational
concrete-lined ditch is shown in Figure 22.
A problem inherent to the open ditch is one of
evaporation losses from -the free water surface.
Substitution of closed conveyances such as steel, concrete
or plastic mainline or conduit is the logical alternative.
Pipelines, in addition to eliminating seepage and
evaporation losses ordinarily occupy less space and usually
provide better control over flow regulation. Steel
irrigation pipe mainline is shown in Figure 23. The early
stage of construction of a 30-inch steel pipe flume designed
to convey snow-melt runoff directly to a major irrigation
diversion is shown in Figure 24.
Large earthen irrigation storage reservoirs are often
constructed to provide water for multiple users such as
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FIGURE 19. Earthen water conveyance ditch being
lined by spraying or "shooting" with
concrete. No reinforcement is used in this method.
Final County, Arizona. Photo courtesy Soil
Conservation Service, U.S. Dept. of Agriculture
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FIGURE 20. Pouring concrete ditch with size 12 wire
mesh being placed in the concrete.
This ditch is 34 inches deep with 1 to 1 side slopes.
Pueblo county, Colorado. Photo courtesy Soil Conser-
vation Service, U.S. Dept. of Agriculture.
85
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^-^*
" ^y^:::v-V
*.
V
':t
FIGURE 2], The Delta B Canal, a large conveyance
channel near Delta, Utah being lined
with plastic. Two 32 foot plastic strips are being
used to line the canal. Photo courtesy Soil Conser-
vation Service, U.S. Dept. of Agriculture.
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FIGURE 22. A modern concrete-lined irrigation
canal. Note control gates which can
be closed in order to regulate the flow of water
into the desired channel. The crop is alfalfa.
Installation near Red Bluff, California. Photo
Courtesy Soil Conservation Service, U.S. Dept. of
Agriculture.
87
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*3?
,;**
FIGURE 23. Steel mainline (42 inch penstock)
capable of delivering 50 cubic feet
per second of irrigation water to 3000 acres of
cropland. Near Payette, Idaho. Photo courtesy Soil
Conservation Service, U.S* Dept. of Agriculture.
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FIGURE 24. Irrigation pipe being delivered by
helicopter to site in mountainous
terrain. This 30 inch flume will deliver snow-
melt runoff water directly to an open diversion
ditch. Near Gypsum, Colorado. Photo courtesy
Soil Conservation Service, U.S. Dept. of Agriculture.
89
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irrigation or conservation districts. Storage reservoirs
are also useful in areas where the sources of water are
limited. For example, a low-productivity well or wells can
supply water continuously to the reservoir while the latter
is used intermittently to irrigate. These structures may be
a source of seepage and subsequent impairment of ground
water quality if improperly constructed. Leakage can be
eliminated by sealing the reservoir walls and floor with
impervious materials. Figure 25 illustrates the
application of "gunnite" (grout) to excavation walls.
Figure 26 illustrates the placement of polyethylene lining
in an irrigation reservoir. Excellent treatments of the
subject of ditch lining and reservoir sealing have been
issued by the U.S. Department of Agriculture and the U.S.
Bureau of Reclamation (46, 47, 48) .
Many delivery systems in use today contain no provision
to meter or otherwise regulate the amount of water provided
to the irrigator. Correct measurement not only increases
water application efficiency, but is a sound water manage-
ment practice. A higher degree of water-use efficiency can
be attained when the amount of water passing principal
points in a delivery system is known.
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FIGURE 25. Earthen irrigation storage reservoir
being lined with grout or "gunflite
reinforced with wire mesh. Sealing the walls and floor
of the structure virtually eliminates seepage.
San Diego County, California. Photo courtesy Soil
Conservation Service, U.S. Dept. of Agriculture.
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FIGURE 26. Polyethylene lining being placed in large
irrigation reservoir to render the
water-holding facility impervious to leakage.
Riverside County , California. Photo courtesy Soil
Conservation Service, U.S. Dept. of Agriculture.
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Farm Water Management System
The judicious management of water applied to irrigated
crops on the farm represents the most practicable method of
controlling water pollution imparted by irrigation return
flows.
Controlled application such as irrigation scheduling
will reduce excessive seepage losses and eliminate surface
runoff while maintaining correct available moisture capacity
in the plant root zone.
Irrigation scheduling is defined as the process of
applying an optimum amount of water to any particular crop
when it is needed. In many irrigated areas the farm
operator is inclined to irrigate when his field is dry
rather than attempt to maintain an optimum moisture level in
the soil. Over-application of water on a discontinuous
basis frequently occurs and may result in possible damage to
the crop, unnecessary runoff, and excessive deep
percolation. Optimum irrigation scheduling is currently
being practiced in a number of areas in the western states
and may ultimately be adopted as the accepted method of
irrigation on a nation-wide scale. Demonstration projects
using scheduling techniques are becoming more numerous and
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computerized programs involving water application to
irrigated farms are being developed.
The Bureau of Reclamation is conducting a pilot
irrigation-management study in southern Idaho to develop a
useful computerized-management program that can be employed
by both irrigation districts and individual irrigators (49,
50). The program1s goal is the development of a system
which will schedule both the application of irrigation water
to the farm and delivery of water through the system. The
program was the outgrowth of a study which indicated that
regional farmers were obtaining less than 45 percent
effective use of applied water. The low efficiency resulted
from excessive application and inexact timing. The soil
moisture reservoir was not being fully utilized. Experts
estimated that proper scheduling of irrigation, plus
improved on-the-farm water management, could increase
efficiency to 55 or 60 percent. The program was implemented
in 1969 with eight farmers initially participating on a non-
assessment basis and has since expanded to 76 users,
irrigating approximately 14,000 acres (5,665 hectares) of
the 76,000 irrigable acres (30,755 hectares) in the project
area. Scheduling techniques involving the field-computer
approach have also been developed by the Salt River
Project's Agriculture section, Arizona (51, 52). Project
personnel work closely with the individual irrigator in an
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effort to achieve optimum use of water for a particular crop
growing in a typed soil. Field services rendered include
fertilizer application recommendations along with the
evaluation of current in-use irrigation system efficiencies.
The concept of scientifically-determined irrigation
scheduling is rapidily expanding and several commercial
irrigation management services capable of providing the
irrigator with computerized analyses and trained
agriculturists are available to the prospective client.
On-the-farm water management practices, less
sophisticated than computerized scheduling, can be applied
by the irrigator to effect substantial decreases in return
flow volumes. These include the prevention of overflow in
head ditches and laterals; improved distribution of water
over the field, elimination of "lows" or depressions in the
graded field to prevent ponding of water; contoured terraces
constructed to prevent runoff; and prudent choice of
irrigation method. These factors, along with others
somewhat less important, constitute good conservation-
irrigation practices.
Modern equipment and methods to accurately control
distribution of water applied to the land are available to
the present-day irrigator. Substantial reductions in the
amount of applied water can be achieved after leveling or
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releveling the land and maintaining the improved
configuration. Reductions as great as 40 to 50 percent in
water use may occur following leveling and the installation
of simple (Parshall flume) water measuring devices. Over-
irrigation results in excessive water losses due to
abnormally high seepage and evaporation, causes soil
waterlogging in low spots, and creates potential drainage
problems. Planned water use reduces labor costs. The well-
managed system also requires less attention. Farm ditches
kept clean and free of weeds, grasses and debris will
prevent clogging, overflowing, and attendant water wastage
and erosion.
Water Application Methods
There are three basic methods of applying water to an
irrigated tract. These are surface, sprinkler, and
subsurface. Choice of method is principally a function of
land slope, soil type, water quality, plant acceptance and
soil erodability.
Surface Methods
*
In the surface method, water is applied directly to the
ground at ground level and flows by gravity over the
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surface of the field. The amount of land slope is important
in the surface irrigation system inasmuch as the
distribution of water over the field is totally dependent
upon natural flow. The surface must be relatively flat and
any slope present must be very gentle. Irrigation of close-
growing crops is accomplished by flooding the entire field,
which is surrounded by a dike, levee, or border to confine
the water. in the irrigation of row crops, the water is
directed down the furrows between the rows through siphon
tubes from an adjacent water supply ditch. Surface
application by the level border or furrow method is adapted
to soils that have relatively low infiltration rates. Care
must be taken to avoid too rapid application which could
result in abnormal waste, excessive leaching, waterlogging,
erosion,and accumulation of tailwater. Absolute control
over these factors probably cannot be achieved. Control of
tailwater, however, can be accomplished by recirculating or
reusing the excess water applied on the farm. The reuse
system also allows the irrigator a reasonable degree of
application latitude and enables the use of minimulm |
allowable stream flows in each furrow. Minimal furrow
stream flow in turn, normally results in decreased furrow
erosion, higher irrigation efficiencies and larger crop
yields.
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Trickle and Drip Methods
A variation of the surface method is the relatively new
trickle or drip irrigation system. In the trickle method,
water is applied very slowly to the soil surface adjacent
to the base of the plant through a series of tiny holes or
valves in irrigation pipe laterals. Water from these point
sources moves through the soil by the action of gravity and
capillarity. Evaporation losses are greatly reduced and
water released is confined to a relatively small segment of
soil adjacent to the plant root zone. This method offers
considerable promise in future control of return flows and
is capable of achieving very high irrigation efficiencies
under many conditions (53, 54).
Drip irrigation is versatile and can be applied to
field crops, orchards, vineyards, or pasture. A problem
inherent to the method is the accumulation of salts at the
periphery of the wetted portion of the moisture profile,
where evaporation leaves a deposit of solids. Periodic
leaching may be required to carry these salts below the root
zone. Other problems are mechanical and involve a lack of
uniform water application caused by manufacturing
imperfections in water emitters, emitter clogging, and
emission rate fluctuations resulting from friction-induced
pressure drops in the conveyance lines. These have been the
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object of recent investigations (55). Problems and
potentials of both trickle and drip systems have recently
been summarized (56) .
Sprinkler Methods
Sprinkler irrigation imitates rainfall nature's
ordinary method of applying moisture to the land.
Sprinkler methods can be applied to soils having high intake
rates, on steep and irregular slopes, and on soils that are
rough or too thin to level because of danger of exposure of
subsoil. Irrigation of sloping, irregular land must be
almost entirely limited to sprinkler methods inasmuch as
homogeneous distribution of water can only be accomplished
by sprinkling provided water is applied slowly enough to
prevent erosion. Automatic controls are adaptable to
sprinkler methods so that systems can be designed with a
high degree of operational flexibility. Fertilizers,
including liquid animal wastes, cannery waste lagoon
effluents, and pesticides can be readily applied through
sprinkler systems. Drawbacks to the use of sprinkler
methods exist. If the crop grown is subject to fungi
development or other diseases aggravated by high-moisture
conditions, the method may have severe limitations. Also,
highly saline water may leave toxic, and often lethal,
deposits on the foliage if applied during periods of high
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ambient temperatures. High winds may distort spray patterns
and reduce the efficiency of sprinkler application.
Excessive amounts of silt, along with sand and trash in the
water supply may cause nozzle plugging and excessive erosion
of moving parts. This foreign material must be removed from
the water prior to its introduction into the system.
Methods
Subsurface irrigation or subirrigation, as originally
defined, reguired that the ground water table be close to
the plant root zone or that an impervious layer of rock or
soil be present to confine the applied water to a position
immediately below the root zone. In the subsurface method,
water is supplied to the ground water mass through canals
and laterals or by a system of subsurface pipelines in
quantities which carefully regulate the height of the water
table below the root zone. Capillarity th|ein conveys the
water to the roots of the plant. The system possesses a
dual capability and is, in reality, a combination irrigation
and drainage network capable of both supplying water and
disposing of excess water if well-managed and properly
monitored.
*
An interesting adaptation of water table management in
subirrigation is cited in recent investigations of the use
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of subsurface drains to maintain the water table at proper
depth to supply the needs of growing crops (57).
A new concept in subsurface irrigation, and one that
shows exceptional promise in the field of return flow
quality control, does not require the presence of a shallow
ground water table. Water is applied underground to the
root zone through tiny holes or valves in small diameter
pipes buried in the row at the level of the root zone.
Application rates can be carefully regulated to irrigate at
frequent intervals with small amounts of water. Evaporation
is reduced and salinity concentrations minimized. The
application of water directly to the root of the plant has
reportedly resulted.in comparable crop yields using one
half, or less, of that needed in "conventional" irrigation
methods. This method then, may literally double the
potential acreage that can be irrigated by a given quantity
of water in those areas where its use is feasible. The
method needs further testing over several agricultural
cycles before its range of application can be established.
A significant drawback is the system's capital cost which
ranges from $345 to $850 per acre ($850 to $2100 per
hectare), depending on pipe spacing. The principal
application of subsurface irrigation techniques of this type
will be in the cultivation of high-value crops in areas
where water is expensive (56).
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Minimum Tillage
Suppression of evaporation and transpiration of
moisture from the soil reduces irrigation water demand and
subsequently lessens the likelihood of excessive return
flows. A cultural practice, known to agronomists for many
years but not widely applied in irrigated agriculture is the
no-tillage or minimum-tillage technique. The system
requires that mulch left by a prior planting be retained on
the soil surface. Significant reductions in runoff, soil
erosion and nutrient loss, caused by destructive action of
rainfall, can be achieved by preserving this protective
ground cover. Rises in crop yields are the result of
increased water infiltration and decreased evaporation.
Minimum tillage techniques do have disadvantages. Weeds
must be controlled by application of herbicides prior to
planting. Plantings in areas infested by bermudagrass or
johnsongrass are ineffective inasmuch as herbicides fail to
control these grasses. Pests such as cutworms, armyworms,
wireworms and slugs tend to be protected by the mulch. It
may be difficult to control volunteer crop plants and,
unless reasonable use of herbicides can effect control,
reversion to tillage or cultivation will be necessary. The
possible application of the technique to irrigated farming
was discussed during a recent no-tillage symposium (58).
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£g£gWater^Removal System
The removal of applied water is an important aspect of
the irrigation water management system. Both surface and
subsurface returns must be considered.
Cultural practices designed to conserve water applied
to the field and thereby reduce surface returns are well
known and basically simple. Surface runoff is likely to
occur if application of water to the land is unavoidably
excessive as it might be in areas having very tight soils.
Such soils have very low intake rates and require large
amount of water for leaching.
Runoff can be minimized by deep-plowing. This creates
a rough surface and facilitates soil moisture uptake and
retention. Infiltration into deep-plowed soils may be
increased by a factor of eight-to-fifteen times that of
lightly-plowed soils. Contour planting and contour tilling
can reduce soil loss caused by runoff, particularly on
slopes of low-to-moderate grade, by as much as 50 percent.
Contour strip cropping, a method of alternating strips of
grass, which is close-growing, with strips of grain or
other row crops can likewise be very effective in
suppressing field erosion in addition to reducing runoff.
The grass strip acts as a partial barrier to runoff,
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decreases its velocity, and acts as a filter, trapping a
significant quantity of sediment while allowing the water to
pass. Formed structures such as terraces and berms are
commonly used to reduce concentrated runoff or intercept
moderate-to-high velocity flows.
*j
Surface runoff control lessens the degree of sediment
transport and decreases the likelihood of important losses
of nutrients and pesticides adsorbed on sediment particles.
Filtration of water through a few feet of soil ordinarily
eliminates nearly all adsorbable pesticides and nutrients
but may have little effect on soluble minerals or highly
soluble nutrients. The irrigator should remain continuously
aware of the fact that a significant increase in water
retention will tend to increase the subsurface component of
irrigation return flow and increase the risk of stream and
ground water pollution.
Excess water applied to the field can be collected in a
reuse reservoir or tail ditch and recycled through the
irrigation distribution system. In this manner, nutrients,
pesticides, organic debris, dissolved solids, bacteria and
plant parasites can be confined to the field. If not
reused, tailwater may enter the surface or subsurface drains
and provide contaminant loads similar to that of surface
runoff, its non-consumptive counterpart. The difference in
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composition between anplied water and irrigation runoff
water in small watersheds has been the subject of recent
studies by the U.S. Department of Agriculture (59).
Reuse of runoff water is a desirable conservation
practice and can significantly reduce the ultimate cost of
water, particularly to the irrigator who has found it
necessary to develon a water well system at considerable
capital expenditure. Reuse systems are not uncommon and
need not be complex. The components usally consist of a
collection pit, screen, pump, and automated controls (Figure
27). The system, including the possibility for use as an
animal waste disposal facility in conjunction with farm
livestock programs, has been described by the Nebraska
Agricultural Experiment Station in cooperation with the
Agricultural Research Service (60) . Recycling excess
irrigation water offers an excellent method of return flow
control.
Subsurface drainage systems are often necessary to
prevent waterlogging of the soil and are used to control
buildup of salinity at or near the ground surface. Shallow
water tables impede achievement of salt balance by
increasing leaching requirements. Tile drainage networks
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- i ,-
FIGURE 27. On-farm irrigation tailwater return
pit. Intercepted water is recycled by
pumping through a plastic pipeline to a con-
crete-lined ditch for reuse. Near Pecos, Texas.
Photo courtesy Soil Conservation Service, U.S.
Dept. of Agriculture.
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are extensively used to convey water from the soil and to
depress the ground water table to a point where it will not
endanger crops. The tile drain and collection system offers
a point source for treatment and control of pollutants. The
problem of pollution by water emanating from tile drains has
been addressed by the Federal Water Pollution Control
Administration and others (39, 61) .
Methods of Return Flow Control
The methods and procedures cited as pollution controls
are those currently available to the irrigator and can be
catergorized as state-of-the-art measures. They are
technically feasible, practicable, economically viable,
socially acceptable, and without adverse legal constraint.
Their implementation would require few additional structural
facilities or institutional changes on the part of the
irrigator.
Feasiblity investigations that may provide additional
measures of control of pollution created by irrigation
return flow include several important studies now underway.
Among these are measures designed to conserve water by
minimizing evapotranspiration. The rate and amount of this
loss is a function of numerous factors including solar
radiation, temperature, relative humidity, wind velocity -
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available soil moisture, type of crop, stage of crop
growth, length of growing season, degree of tillage, and
surface mulch conditions. Any practicable method to reduce
evapotranspiration is desirable and will increase irrigation
efficiency. Reduction of evapotranspiration losses can be
accomplished through judicious project planning (62). It
has been shown that evapotranspiration can be diminished by
using artificial barriers. These inhibit the downward
movement of water and thereby curtail losses by deep
percolation. Soil water evaporation losses to the
atmosphere may also be reduced by these barriers (63, 6H,
65). The most successful of these methods employ asphalt
emplaced by tractor at depths of approximately two feet.
The work is in the experimental and demonstration stage.
Implementation costs range from $200 to $250 per acre.
Consumption of water by phreatophytes (those plants
that habitually obtain their water supply from the zone of
saturation either directly from or through the capillary
fringe) is quite large in arid and semiarid regions. The
control and partial elimination of these water users would
release appreciable volumes of water for beneficial uses.
However, the destruction of phreatophytes such as saltcedar,
willow, cottonwood and mesquite would have to be undertaken
on a limited orderly and carefully planned basis inasmuch as
many forms of animal life such as birds, fowl, game animals
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and useful predators depend on the sanctuary of dense
phreatophytic environments for survival.
Of all water uses (and losses) involved in the field of
agriculture, the use of water by a growing plant is the most
wasteful and involves efficiencies of only one to two
percent. It is apparent that if plant efficiency could be
increased by only a few percent, millions of acre-feet of
water could be conserved. An interesting technology in
evapotranspiration control is aimed at reducing the fluid
loss from the growing plant per se. The concept is not new
and has been used by nurserymen to combat desiccation of
damaged trees and shrubs whose preservation was considered
essential. A family of non-toxic chemicals designed to
accomplish transpiration control more efficiently than at
present is currently being developed. These compounds,
called antitranspirants, fall into three catergories and
include chemical leaf sealants, materials that increase leaf
reflectivity and thus reduce plant heat load and, finally,
chemicals which tend to reduce the size of the stomata or
plant pore.
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NEEDED_DEMONSTRATIONS_AND_RESEARCH
Research and demonstration projects needed in the fielc
of irrigated agriculture should emphasize those aspects
with the greatest near-term impact upon water quality
control. These fall into two major catergories and are, 1)
technical, including management of the soil-plant-water
system and, 2) institutional-legal, involving possible
innovation, revision and reformation of irrigation district
structure, reevaluation of Western water law and its
conflict with water quality standards, and other institu-
tional constraints. Both recognize that excessive water use
is the greatest cause of water quality degradation
associated with irrigation.
Technical
A blend of research and demonstration is neeeded to- develop
methods of increasing efficiency in irrigation practices.
This concept involves sound design and subsequent operation
of an irrigation project which will maintain crop yields and
at the same time reduce water requirements, volume of
irrigation returns, and amount of salt transported to
surface or subsurface waters. Elements of the project must
*
also be economically feasible.
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Increased efficiency can be accomplished in several
ways. Included is judicious management of the water-soil-
plant system conducted, under conditions where climate, water
salinity and soil type are the major variables. Such
methods use proven irrigation techniques to increase the
efficiency of the water delivery system, the on-farm
application system and the water removal system.
Methods of water application can greatly influence
irrigation efficiency. Significant increases using
subirrigation, drip-trickle and bubbler methods can be
attained but will create a need for additional research
inasmuch as the environment to which the irrigated crop will
be exposed is radically changed. Soil-water in drip-trickle
methods remains uniformly and continuously high. Organism
populations in the surface soil may change and give rise to
new and differing plant diseases. The possibility of
adverse pathogenic effects also exist. Poor management of
the drip-trickle system could be damaging and create
hitherto unknown problems. Nutrient utilization will also
be affected by a continuously moist environment. Salinity-
nutrient interactions under these conditions are known to
occur but little is known of the mechanism or its effects on
plant response. Plant stress interactions between relative
humidity and salinity, and between ozone (polluted air) and
salinity are recognized. Adverse effects of air pollution
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can occasionally be overcome by salt stress and may be
useful in maintaining ornamentals in a healthy state by
artificial salination of the soil where air pollution is a
problem.
Control of water application to establish a uniformly
moist environment might be achieved through the use of
sensors to monitor soil salinity at given depths. Soil
salinity is a function of the amount of transitory drainage
water. A salinity sensor grid might represent a major
component of future irrigation systems. The foregoing con-
cepts represent only a few of many possibilities designed to
increase irrigation efficiency through advanced technology
(66) . The concept of irrigation return flow water quality
improvement through application of more efficient methods is
in harmony with the Environmental Protection Agency's
position that remedial measures should be applied at the
pollution source rather than by treatment of the effluent.
Research within the framework of the National
Irrigation Return Flow Research and Development Program
prepared for the Office of Research and Monitoring,
Environmental Protection Agency contains a summary of
worthwhile needs (16). A major thrust of the program is
directed toward the development and demonstration of
improved crop, plant, nutrient and pesticide management
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methods, all based upon interaction between soil,
hydrology, salt and nutrient movement, fate of pesticides,
and other factors. The development and demonstration of
new and improved water delivery systems, application
methods, drainage systems and tailwater reuse systems must
necessarily be an integral part of the same program.
Additional research needs and potential solutions for con-
trolling quantity and quality of irrigation return flow are
summarized in a prior Environmental Protection Agency
publication (27) .
Institutional-Legal
A demonstration or research program need not
necessarily be limited to technologically-oriented projects
but can include institutional approaches. These, like the
technological approach, employ the concept of improved water
management practices. Projects could include the
restriction of irrigation development in areas of
potentially high salinity; consolidation of irrigation
companies and water supply districts into single management
units; and encouragement of local acceptance of control
measures through educational programs on the local,
regional and State levels.
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Other projects might include evaluations of the
operational and proposed programs of Federal, State and
local agencies to determine what future courses of action
will be required to achieve reduction in pollution created
by irrigation return flows. An important facet of such
evaluation would include regulatory powers and authorities
needed regarding land and water management and the
possibility of integrating these into a return flow control
program.
The control of diffuse returns is complicated by the
difficulty of quantification, including determination of
their measurement of pollutional effects. Additional com-
plications are the basic conflicts between Western water law
and water quality standards. The legal rule that water must
be used to maintain the continued right to its use
aggravates the problem.
Institutional constraints have been responsible for1
numerous salinity problems in many irrigated areas in the
United States. Among these constraints are legal,
political, cultural and economic. The legal constraint
involves water rights. A water right is the legal right to
the use of water and grants the right to divert and excerise
A
physical control over the water. The right determines who
can take the water, the amount to be taken, and the time of
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taking. The right is established as to priority of use and
affords legal protection to the user. An irrigator having
an adequate water right has little economic incentive to
institute efficient water management practices. As a
result, excessive irrigation often occurs. Rights cannot be
bartered, bought, sold or leased, but must revert to the
original grantor if not used. The "property right in water"
concept created through the prior appropriation doctrine
thus is a major deterrent to the implementation of water
management technology. The element of water quality is not
considered. The path to the resolution of the water
management problem in the West could be cleared to a large
degree by changes, or reinterpretation, of the doctrine.
Perhaps strict enforcement of the law may, in many
instances, be all that is required to implement control.
For example, there are direct statutory restrictions to the
excerise of a water right as in Colorado Revised Statute
Section 148-7-8 providing "during the season it shall not be
lawful for any person to run through his irrigation ditch a
greater quantity of water than is absolutely necessary for
irrigating his land and for domestic and stock purposes; it
being the intent and meaning of this section to prevent the
wasting and useless discharge and running away of water"-
Further limiting this water right, the Colorado court held
in 1893 that no one is entitled to a priority of more water
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than he has actually appropriated nor for more than he
actually needs (67) .
A particularly troublesome institutional deterrent to
control of return flow salinity exists in the Lower Rio
Grande Valley. Irrigation is controlled and administered by
34 separate irrigation districts and four drainage districts
plus water and other metropolitan districts. Each district
has its own power and authority over the use, development,
protection and administration of water within its
jurisdiction. Each district designed and built its
distribution and drainage facilities to serve only the area
within its boundaries. Little attention was paid to the
overall effect on Valley irrigation. These and other
factors pertinent to the institutional problem of the Valley
are presented in several important studies prepared by Texas
ASM University (68, 69, 70). Conflicts created by these
numerous and overlapping authorities account for a
significant part of the Valley salinity and drainage
dilemma. Cultural institutions in the Valley involve the
continued use of time-honored concepts, customs and
traditions that are no longer applicable in many instances
and should be discontinued. These involve water application
and use practices, labor use and crop preference.
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A recent Environmental Protection Agency in-house study
of salinity created by irrigation return flows concluded, in
part, that the solution of the problem can only be
accomplished through a basin-wide control program. The
study also concluded that, "Improved water management
practices, particularly the use of water at optimum
efficiencies on the farm, is the most feasible approach to
controlling excessive salt loads from irrigation return
flows to many of our western river systems. Present
technology would permit the implementation of several
salinity control measures that are not now widely employed
...."r and "Legal and institutional means must be found to
control water salvaged through improved water management in
order to finally achieve a solution to basin-wide salinity
problems".
Present levels of government concern and effort can be
expected to produce major achievements relating to
permanent and definitive solutions to the problem of control
of salinity and other pollutants.
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GLOSSARY OF TERMS
-^sS-Wat6.?. ~ water diverted for irrigation but returned to
the source without having been applied to the land.
- water discharged into the atmosphere as
vapor and no longer available for use by the discharging system.
Evapotranspiration - water lost as vapor from the combined
process of evaporation from the soil and transpiration from
vegetation. Evapotranspiration represents an important
consumptive use of water.
ion - the application of water to furrows
(narrow trenches dug by farm equipment) to irrigate crops
planted in, or between, the furrows.
Leaching^reguirement - the amount of water that must pass
through the root zone to maintain a prescribed salt level.
Expressed as a percentage of the total water applied to the
land.
Qsmgtic_ action - the diffusion of water through a
semipermeable membrane (example - soil moisture extracted by
plant root hairs).
Perched_ground_water_body - a ground water mass located within
the zone of aeration, and seprated from the main underlying
ground water body by a zone of unsaturated rock.
Permeability - the capacity of a material (soil) to transmit
fluid (air and water) .
£°.£2.§i±Y. ~ tne ratio of the aggregate volume of interstices,
voids, pores or other openings of a soil sample to the total
(bulk) volume. Usually expressed as a percentage.
Prior appropriation^doctrine a basic doctrine that all
waters in a State, whether above or below the ground, are the
property of the people. A vested right to the use of the
water is acquired by appropriation and the application of the
water to beneficial use. The individual first in time is
first in right and beneficial use is the basis, the measure,
and the limit of the right.
Salt_loadin2 - the addition of dissolved solids to water
from both natural and man-made sources. Not to be confused
with salt concentrating which increases salinity by stream
flow depletion and concentration of the salt burden in a lesser
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volume of water. Salt loads may originate in surface runoff,
diffuse ground water discharges, mineral springs, municipal
and industrial waste, and irrigation.
!!ts - a group of low-nutrient organic materials
such as compost, peat, and sewage sludge that may be
incorporated into the soil or used as mulches. Amendments
have a dual effect of improving the condition of the soil
while providing some plant nutrient.
Tajlwater - water which is the excess remaining after
an irrigation.
Trickle_ irrigation - water applied very slowly to the
surface of the soil through tiny holes or valves in plastic
pipe.
Wat er^ infiltration - the downward flow of water from the
soil surface into the soil. Infiltration implies flow into
the soil as contrasted to percolation which denotes flow
through the soil.
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REFERENCES CITED
1. Committee on Pollution, National Academy of Sciences
- National Research Council, "Waste Management and
Control"., Publication 1400. A Report to the
Federal Council for Science and Technology, p.
141. Washington, D. C., 1966.
2. "Planning for an Irrigation System". American
Association for Vocational Instructional Materials
in Cooperation with the Soil Conservation Service,
United States Department of Agriculture, pp. 17-
21, Engineering Center, Athens, Georgia, June,
1971.
3. Law, James P. and Witherow, Jack L., "Irrigation
Residues", Journal of Soil and Water Conservation,
Vol. 26, No. 2, pp. 54-56. March-April, 1971.
4. Characteristics and Pollution Problems of Irrigation
Return Flow. Utah State University Foundation.
Robert S. Kerr Research Center, Federal Water
Pollution Control Administration, United States
Department of the Interior, Ada, Oklahoma, May
1969.
5. Bishop, A. Alvin, "Conflicts in Water Management",
Forty-second Honor Lecture, Winter 1971. The
Faculty Association, Utah State University, Logan
Utah.
6. Public Health Service Drinking Water Standards,
1962. Public Health Service Publication No. 956,
U.S. Department of Health, Education, and Welfare,
Washington, D. C.
7. Water Quality Criteria. Report of the National
Technical Advisory Committee to the Secretary of
the Interior. Federal Water Pollution Control
Administration. Washington, D. C., April 1968.
8. Hely, Allen G., Lower Colorado River Water Supply -
its Magnitude and Distribution. United States
Geological Survey Professional Paper. 486-D,
1969.
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9- Irelan, Burdge, Salinity of Surface Water in the
Lower Colorado River-Salton Sea Area. United
States Geological Survey Professional Paper.
486-E, pp. E-31 and E-32, 1971.
10. Diagnosis and Improvement of Saline and Alkali
Soils, United States Salinity Laboratory Staff,
Agriculture Handbook No. 60. United States
Department of Agriculture, Washington, D. C.
August, 1969.
11. Carter, R.F., Presentation of Imperial Irrigation
District, Environmental Protection Agency
Conference. Las Vegas, Nevada, Feburuary 15, 1972.
12. Need for Controlling Salinity of the Colorado
River. Colorado River Board of California. The
Resources Agency. State of California, August,
1970.
13. The Mineral Quality Problem in the Colorado River
Basin, Appendix A., "Physical and Economic
Impacts", U.S. Environmental Protection Agency
Regions VIII and IX, 1971.
14. Quality of Water, Colorado River Basin, Progress
Report No 5. United States Department of the
Interior, Washington, D. C., January 1971.
15. Upper Colorado Region. Comprehensive Framework
Study. Appendix XV. Water Quality Pollution
Control and Health Factors. Workgroup of the
Upper Colorado Region State-Federal Interagency
Group for the Pacific Southwest Interagency
Committee, Water Resources Council, Washington,
D. C., June, 1971.
16. Law, James P., Jr., National Irrigation Return Flow
Research and Development Program. Water Pollution
Control Research Series. U.S. Environmental
Protection Agency. Washington, D. C., December
1971.
17. Lower Colorado Region. Comprehensive Framework
Study, Appendix XV. Water Quality Pollution
Control and Health Factors, prepared by Lower
Colorado Region State-Federal Interagency Group
for the Pacific Southwest Interagency Committee,
Water Resources Council, Washington, D. C., June
1971.
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18. Skogerboe, Gaylord V., and Walker, Wynn R.,
11Preconstruct!on Evaluation of the Grand Valley
Salinity Control Demonstration Project."
Agricultural Engineering Dept., College of
Engineering, Colorado State University, Ft.
Collins, Colorado, June 1971.
19. Walker, Wynn R., and Skogerboe, Gaylord V.,
"Agricultural Land Use in the Grand Valley",
Agricultural Engineering Dept., College of
Engineering, Colorado State University, Ft.
Collins, Colorado, July , 1971.
20. Walker, Wynn R., and Skogerboe, Gaylord V.,
"Hydrologic Modeling for Salinity Control
Evaluation in the Grand Valley" in Proceedings on
National Conference on Managing Irrigated
Agriculture to Improve Water Quality, Sponsored by
the U.S. Environmental Protection Agency and
Colorado State University, Grand Junction,
Colorado, pp. 67-75, May 16-18, 1972.
21. Skogerboe, Gaylord V. and Walker, Wynn R.,
"Evaluation of Canal Lining for Salinity Control
in Grand Valley", Environmental Protection
Technology Series. Office of Research and
Monitoring, U.S. Environmental Protection Agency,
Washington, D. C., October, 1972.
22. King, Larry G., Hanks, R. John, Nimah, Musa N.,
Gupta, Satish C. and Backus, Russel B., "Modeling
Subsurface Return Flows in Ashley Valley." In
Proceedings of National Conference on Managing
Irrigated Agriculture to Improve Water Quality,
Sponsored by the U.S. Environmental Protection
Agency and Colorado State University, Grand
Junction, Colorado. pp. 241-256, May 16-18, 1972.
23. Wilson, Robert F-, "Hydrologic Modeling of Ashley
Valley, Utah". In Proceedings of National
Conference on Managing Irrigated Agriculture to
Improve Water Quality, Sponsored by the U.S.
Environmental Protection Agency and Colorado State
University. Grand Junction, Colorado, pp. 229-
239, May 16-18, 1972.
24. Troxell, Harold C., "Water Resources of Southern
California With Special Reference to the Drought
of 1944-51". Geological Survey Water Supply Paper
1366, Washington, D. C. 1957.
122
-------
25. Mackenzie, Arnold J., "Soil Water and Cropping
Management for Successful Agriculture in Imperial
Valley". In Proceedings of National Conference on
Managing Irrigated Agriculture to Improve Water
Quality. Sponsored by the U.S. Environmental
Protection Agency and Colorado State University,
Grand Junction, Colorado, pp. 41-45, May 16-18,
1972.
26. Colorado River Association, Newsletter, Los
Angeles, California. January/February, 1973.
27. Skogerboe, Gaylord V. and Law, James P., Jr.,
"Research Needs for Irrigation Return Flow Quality
Control", Water Pollution Control Research Series,
U.S. Environmental Protection Agency, November,
1971.
28. Bower, Charles A., Spencer, J.R. and Weeks, Lowell
O. "Salt and Water Balance, Coachella Valley,
California." Journal of the Irrigation and
Drainage Division, Proceedings of the American
Society of Civil Engineers, Vol. 95, No. IRl,
March, 1969.
29. Koenig, James B., "Salton Sea: A New Approach to
Environmental Problems in a Major Recreation
Area". Environmental Planning and Geology. U.S.
Department of Housing and Urban Development and
U. S. Department of the Interior, Washington, D. C.
December, 1971.
30. "The Value of Desalted Water for Irrigation" A
Joint Research Study Prepared for the Office of
Saline Water, United States Department of the
Interior; Bureau of Reclamation, Office of the
Chief Engineer, Denver, Colorado, June, 1969.
31. Emery, P. A., Boettcher, A.J., Snipes, R.J. and
Mclntyre, H.J.,Jr., "Hydrology of the San Luis
Valley, South-Central Colorado". Hydrologic
Investigations Atlas HA-381, U.S. Geological
Survey, Washington, D. C., 1971.
123
-------
32. Clark, John W., "Salinity Problems in the Rio
Grande Basin" in Proceedings on National
Conference on Managing Irrigated Agriculture to
Improve Water Quality Sponsored by the U.S.
Environmental Protection Agency and Colorado State
University, Grand Junction, Colorado., pp. 55-66,
May 16-18, 1972.
33. Jetton, Eldon P. and Kirby, James W., "A study of
Precipitation, Streamflow and Water Usage on the
Upper Rio Grande", Atmospheric Science Group,
College of Engineering, The University of Texas,
Austin, Texas, Report No. 25. June 1970.
34. Wilcox, Lloyd V. "Salinity Caused by Irrigation",
Journal of the American Water Works Association,
Vol. 54, No. 2, pp 217-222, February, 1962.
35. Wierenga, P.J. and Patterson, T.C., "Irrigation
Return Flow Studies in the Mesilla Valley" in
Proceedings of National Conference on Managing
Irrigated Agriculture to Improve Water Quality,
Sponsored by the U.S. Environmental Protection
Agency and Colorado State University. Grane
Junction, Colorado. pp. 173-179, May 16-18, 1972.
36. "Comprehensive Study and Plan of Development, Lower
Rio Grande, Basin, Texas." U.S. Department of
Agriculture in cooperation with the Texas Water
Development Board, the Texas State Soil and Water
Conservation Board and the Texas Water Rights
Commission, Temple, Texas. July, 1969.
37- "Water Resources of New Mexico, Occurrence,
Development and Use". Compiled by the New Mexico
State Engineer Office in cooperation with the New
Mexico Interstate Stream Commission and the U.S.
Geological Survey State Planning Office, Santa Fe,
New Mexico, 1967.
38. "Nutrient from Tile Drainage Systems". Bio-engineering
Aspects of Agricultural Drainage, San Joaquin
Valley, California prepared by the California Department
of Water Resources, Water Pollution Control Series.
Environmental Protection Agency, May 1971.
39. "Effects of the San Joaquin Master Drain on Water
Quality of the San Francisco Bay and Delta" by the
Central Pacific Basins Comprehensive Water
Pollution Control project. Federal Water Pollution
Control Administration, U.S. Department of the
124
-------
Interior, Southwest Region, San Francisco,
California. January, 1967.
40. Beck, Louis A., "Treatment of Irrigation Return
Flows in the San Joaquin Valley", in Proceedings
of National Conference on Managing Irrigated
Agriculture to Improve Water Quality, Sponsored by the
U.S. Environmental Protection Agency and Colorado
State University, Grand Junction, Colorado, pp.
83-97, May 16-18, 1972.
41. Sylvester, Robert O. and Seabloom, Robert W., "A
Study of the Character and Significance of
Irrigation Return Flows in the Yakima
Basin", The University of Washington, Department
of Civil Engineering. February, 1962.
42. Carlile, B.L., "Sediment Control in the Yakima
Valley" in Proceedings of National Conference on
Managing Irrigated Agriculture to Improve Water
Quality, Sponsored by the U.S. Environmental
Protection Agency and Colorado State University,
Grand Junction, Colorado, pp. 77-82, May 16-18,
1972.
43, Viers, C.E., "An Assessment of the Effects of
Irrigation on Water Quality in the Pacific
Northwest", The Environmental Protection Agency,
Region X, Seattle, Washington, 1972. Draft report.
44. Gordon, G. V., "Chemical Effects of Irrigation-
Return Water, North Platte River, Western
Nebraska" U.S. Geological Survey Professional
Paper 550-C, pp C244-C250, 1966.
45. Skogerboe, Gaylord V. and Walker, Wynn R.,
Evaluation of Canal Lining for Salinity Control,
Environmental Protection Technology Series, Office
of Research and Monitoring, U.S. Environmental
Protection Agency, Washington, D. C., October,
1972.
46. Lauritzen, C.W., "Lining Irrigation Laterals and
Farm Ditches" Agriculture Information Bullentin No.
242, Agriculture Research Service, U.S., Department
of Agriculture, Washington, D. C., November, 1961.
47. Renfro, George, Jr., "Sealing Leaking Ponds and
Reservoirs", Soil Conservation Service, U.S.
Department of Agriculture, SCS-TP-150, Washington,
D. C., February, 1968.
125
-------
48, Ferrese, R. , "Design Considerations for Open
Channels", Jones, B.V. and Morrison, W.R., "Canal
Linings and Soil Sealants"; and Ruffatti, M.J.,
"Design of Pipe Systems". Part I, II, and III of
"System Moderation and Rehabilitation", Water
Systems Management Workshop, 1971, Lecture Notes,
Bureau of Reclamation, U.S. Department of the
Interior, Denver, Colorado. November, 1971.
49. "Irrigation Management services Program", Annual
Report, 1971, Minidoka Project - Burley, Idaho,
Bureau of Reclamation, U.S. Department of
Agriculture, Boise, Idaho.
50. Brown, R.J. and Buchheim, J.Fr "Water Scheduling
in Southern Idaho, A Progress Report," Bureau of
Reclamation, U.S. Department of the Interior in a
paper presented at the National Conference on
Water Resources Engineering of the American
Society of Civil Engineers, Phoenix, Arizona,
January 11-15, 1971.
51. Jensen, Marvin E. , Robb, David C.N. and Franzoy, C.
Eugene, "Scheduling Irrigations Using Climate-
Soil-Crop Data", Journal of the Irrigation and
Drainage Division, Proceedings of the American
Society of Civil Engineers, pp. 25-38. IRl, March
1970.
52. Kyaw, E. Win and Wilson, David S., Jr., "Irrigation
Scheduling in the Salt River Project", in
Proceedings of the National Conference on Managing
Irrigated Agriculture to Improve Water Quality,
Sponsored by the U.S. Environmental Protection
Agency and Colorado State University, Grand
Junction, Colorado, pp. 187-194, May 16-18, 1972.
53. Goldberg, D. and Shmueli, M., "Trickle Irrigation
A Method for Increased Agricultural Production
Under Conditions of Saline Water and Adverse
Soils", 1969 International Arid Lands Conference,
Tuscon, Ariz.
54. "Proceedings of the Drip-Irrigation Seminar",
Presented at Escondido High School, Escondido,
California, July 16, 1970. Agricultural Extension
Service, University of California. San Diego,
California, Water Irrigation Methods, CP219-500-*
9/70.
55. Myers, Lloyd E. and Bucks, Dale A., "Uniform
126
-------
Irrigation with Low-Pressure Trickle Systems"
Journal of the Irrigation and Drainage Division,
ASCE, Vol. 98, No. IR3, Proceedings Paper No.
9175, pp. 341-346, September, 1972.
56. Cole, Thomas E., "Subsurface and Trickle
Irrigation. A Survey of Potentials and Problems",
Nuclear Desalination Information Center, Oak Ridge
National Laboratory, Oak Ridge, Tennessee,
November, 1971.
57. Skaggs, R. Wayne; Kriz, George J., and Bernal,
Reynaldo, "Irrigation Through Subsurface Drains",
Journal of the Irrigation and Drainage Division,
ASCE, Vol. 98. No. IRS, Proceedings Paper No.
9183, pp. 363-373, September, 1972.
58. Unger, Paul W. and Wiese, Allen F., "No-tillage
Research in the Panhandle of Texas" in
Proceedings, No-tillage Systems Symposium
sponsored by the Ohio State University and Ohio
Agricultural Research Center in Cooperation with
Chevron Chemical Company, pp. 103-107, Center for
Tomorrow, Columbus, Ohio. February 21-22, 1972.
59. Bondurant, James A., "Quality of Surface Irrigation
Runoff Water", Paper No. 71-247, Annual Meeting,
American Society of Agricultural Engineers,
Washington State University, Pullman, Washington,
June, 1971.
60. Fischbach, P.E. and Bondurant, J.A., "Recirculating
Irrigation Water", Paper No. N. National
Irrigation Symposium, Nebraska Center for
Continuing Education, Lincoln, Nebraska, November
10-13, 1970.
61. Willrich, T.D., "Properties of Tile Drainage
Water", American Society of Agricultural
Engineers, 1970 Winter Meeting, Paper No. 70-752,
Chicago, Illinois, December 8-11, 1970.
62. Langley, Maurice N., "Evapotranspiration and Irrigation
Project Planning and Mangement", Conference
Proceedings: Evaporation and its Role in Water
Resources Management American Society of Agri-
cultural Engineers, Chicago, Illinois, December
5-6, 1966.
63. Meyer, Raymond E. "Subsurface Asphalt Barriers as a
Water Conservation Measure" Proc., North West
127
-------
Texas Water Conference, West Texas Water
Institute, Texas Tech University, Lubbock, Texas,
February 5, 1971.
64. Erickson, A.E., Hansen, C.M. and Smucker, A.J.M.,
"The Influence of Subsurface Asphalt Barriers on
the Water Properties arid the Productivity of Sand
Soils" 9th International Congress of Soil Science
Transactions, Volume 1, Paper 35.
65.Fisher, R..C., "Development of Asphalt Moisture
Barrier Equipment", American Society of
Agricultural Engineers, 1971 Winter Meeting, Paper
No. 71A-607 Chicago, Illinois. December 7-10
1971.
66. Van Schilfgaarde, Jan, Personal Communication.
U.S. Salinity Laboratory, Agricultural Research
Service, U.S. Departtment of Agriculture,
Riverside, California. February, 1973.
67- Radosevich, G.E., "Water Right Changes to Implement
Water Management Technology" in Proceedings of
National Conference on Managing Irrigated
Agriculture to Improve Water Quality, Sponsored by
the U.S. Environmental Protection Agency and
Colorado State University, Grand Junction,
Colorado, pp. 265-279, May 16-18, 1972.
68. Trock, Warren L., "Institutional Influences in
Irrigation Water Management" in Proceedings of
National Conference on Managing Irrigated
Agriculture to Improve Water Quality, Sponsored by
the U.S. Environmental Protection Agency and
Colorado State University, Grand Junction,
Colorado, pp. 281-284, May 16-18, 1972.
69. Trock, Warren L., "Institutional Factors
Influencing Water Development in Texas".
Technical Report No. 35, Water Resources
Institute, Texas A&M University, March, 1971.
70. Casbeer, Thomas J. and Trock, Warren L., "A Study
of Institutional Factors Affecting Water Resource
Development in the Lower Rio Grande Valley,
Texas," Technical Report No. 21, Water Resources
Institute, Texas A&M University, September, 1969.
*-
71. "Report of Steering Committee on Salinity control
of Irrigation Return Flows", U.S. Environmental
Protection Agency, Region VIII - Denver, Colorado,
December, 1972. Unpublished.
128 *U.S. GOVERNMENT PRINTING OFFICE: 1974 546-317/Z8Z 1-3
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