&EPA
United States
Environmental Protection
Agency
Robert S Kerr Environmental Research EPA-GOO/2-78-162
Laboratory July 1978
Ada OK 74820
Research and Development
Best Management
Practices"
for Salinity Control
in Grand Valley
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S, Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2 Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-78-162
July 1978
"BEST MANAGEMENT PRACTICES" FOR SALINITY CONTROL
IN GRAND VALLEY
by
Wynn R. Walker
Gaylord V. Skogerboe
Robert G. Evans
Agricultural and Chemical Engineering Department
Colorado State University
Fort Collins, Colorado 80523
Grant No. S-802985
Project Officer
James P. Law/ Jr.
Source Management Branch
Robert S. Kerr Environmental Research Laboratory
Ada, Oklahoma 74820
ROBERT S. KERR ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
ADA, OKLAHOMA 74820
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DISCLAIMER
This report has been reviewed by the Robert S. Kerr
Environmental Research Laboratory, U.S. Environmental Protection
Agency, and approved for publication. Approval does not signify
that the contents necessarily reflect the views and policies
of the U.S. Environmental Protection Agency, nor does mention
of trade names or commercial products constitute endorsement or
recommendation for use.
11
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FOREWORD
The Environmental Protection Agency was established to
coordinate administration of the major Federal programs designed
to protect the quality of our environment.
An important part of the Agency's effort involves the
search for information about environmental problems, management
techniques and new technologies through which optimum use of the
Nation's land and water resources can be assured and the threat
pollution poses to the welfare of the American people can be
minimized.
EPA's office of Research and Development conducts this
search through a nationwide network of research facilities.
As one of these facilities, the Robert S. Kerr Environmental
Research Laboratory is responsible for the management of programs
to: (a) investigate the nature, transport, fate and management
of pollutants in groundwater; (b) develop and demonstrate methods
for treating wastewaters with soil and other natural systems;
(c) develop and demonstrate pollution control technologies for
irrigation return flows; (d) develop and demonstrate pollution
control technologies for animal production wastes; (e) develop
and demonstrate technologies to prevent, control or abate pollu-
tion from the petroleum refining and petrochemical industries;
and (f) develop and demonstrate technologies to manage pollution
resulting from combinations of industrial wastewaters or indus-
trial/municipal wastewaters.
This report contributes to the knowledge essential if the
EPA is to meet the requirements of environmental laws that it
establish and enforce pollution control standards which are
reasonable, cost effective and provide adequate protection for
the American public.
icJx-^u)
William C. Galegar
Director
Robert S. Kerr Environmental
Research Laboratory
iii
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PREFACE
The Department of Agricultural and Chemical Engineering
at Colorado State University has conducted several research
programs which deal directly or indirectly with the Grand Valley
Salinity Control problem. This report is the last in a series
of three describing the results obtained in one of these pro-
grams, Grant No. S-802985, "Implementation of Salinity Control
Strategy in Grand Valley." However, it is intended to be a
somewhat nontechnical summary relating to the Grand Valley, and
includes results of supportive studies reported by the writers.
The major technical series of reports from which this
report is generated is listed below, a full description is
cited in the references:
Grant No.
14-01-201
S-800278
S-800278
S-802985
S-802985
S-800687
S-800687
Report Title
Evaluation of Canal Lining for
Salinity Control in Grand Valley
Evaluation of Irrigation Sched-
uling for Salinity Control in
Grand Valley
June 1974
Evaluation of Drainage for Salin- Aug. 1974
ity Control in Grand Valley
Implementation of Salinity Con-
trol Technology in Grand Valley
In Press
Evaluation of Irrigation Methods In Press
for Salinity Control in Grand
Valley
Irrigation Practices and Return
Flow Salinity in Grand Valley
Potential Effects of Irrigation
Practices on Crop Yields in
Grand Valley
In Review
In Review
In addition to these major technical reports, there are
several supportive studies which apply to the Grand Valley in
at least some aspect. These are:
IV
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Grant No.
Report Title
Date
R804303
R803572
R803869
R804828
Achieving Irrigation Return Flow In Press
Quality Control through Improved
Legal Systems
Socio-Economic and Institutional In Review
Factors in Irrigation Return
Flows Quality Control
Integrating Desalination and Agri- In Press
cultural Salinity Control Alter-
natives
Assessing the Spatial Variability
of Irrigation Water Applications
In Press
Many of the above reports have been utilized in the
writing of these reports in order to present a broad considera-
tion of "Best Management Practices" in the Grand Valley.
Nearly all of the analytical procedures are left to the reader
to evaluate in the technical reports.
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ABSTRACT
A nontechnical summary of several research activities in
the Grand Valley is given. Analyses.- of alternative measures
of reducing the salt load originating from the Valley as a
result of irrigation return flows are presented. These alter-
natives include conveyance channel linings, field relief
drainage, on-farm improvements (such as irrigation scheduling,
head ditch linings, sprinkler and trickle irrigation), economic
control measures such as taxation and land retirement, modified
legal constraints, and collection and treatment of return flows
with desalting systems.
The best management practices for salinity control in the
Grand Valley should be primarily the structural rehabilitation
and operational modification of the local irrigation system
lying below the turnouts from the major canal systems. Canal
linings appear in the optimal strategies at higher levels of
valley-wide salinity control emphasis but only so far as lining
the Government Highline Canal is concerned. Desalting would
become a cost-effective alternative after major irrigation
system improvements are implemented.
Field drainage, taxation, and land retirement are not
considered reliable control alternatives because of cost and
marginal effectiveness. The legal measures are unlikely candi-
dates in a salinity control program directly, but will play an
important role in implementing the practices which reduce salt
loading directly.
This report was submitted in fulfillment of Grant No.
S-802985 to Colorado State University, under sponsorship of the
Environmental Protection Agency. This report covers the period
February 18, 1974 to June 17, 1977, and was completed as of
January 31, 1978.
VI
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CONTENTS
Foreword iii
Preface iv
Abstract vi
Figures viii
Tables x
Acknowledgments xi
1. Introduction 1
2. Conclusions 29
3. Recommendations 35
4. The Grand Valley Hydro-Salinity System 39
5. Technological Alternatives for Salinity Control 50
6. Best Management Practices 64
7. Economic and Legal Options 86
8. Implementation 98
References 108
vn
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LIST OF FIGURES
Number Page
1 The Colorado River Basin 2
2 Relative magnitude and sources of salt in the
Colorado River Basin 3
3 The Grand Valley, Colorado 6
4 Grand Valley canal distribution system and approxi-
mate areal extent of cobble aquifer 10
5 Geologic cross-section of the Grand Valley 12
6 A typical geologic cross-section in the Grand
Valley, indicating the approximate areal
extent of the cobble aquifer 15
7 Intensive study area for the Grand Valley Salinity
Control Demonstration Project and location of
irrigation scheduling and drainage study farms . . 17
8 Location map of the soil chemistry and crop yields
study area 21
9 Irrigation treatments for corn 24
10 Location of the nine selected lateral subsystems
incorporated in the project 26
11 Mean annual flow diagram of the Grand Valley
hydrology 45
12 Schematic diagram of a typical desalination system . 60
13 Relationship of plant capacity and desalting costs
for various desalting systems that could be
employed in Grand Valley 63
14 Conceptual decomposition model of a regional or
basin salinity control strategy 68
viii
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15 Cost-effectiveness function for the first level,
on-farm improvement alternatives in the Grand
Valley 73
16 Optimal Grand Valley canal lining cost-effectiveness
function 75
17 Grand Valley desalination cost-effectiveness function 76
18 Grand Valley second level salinity control cost-
effectiveness function 78
19 Marginal cost function of optimal salinity control
strategy in the Grand Valley 81
20 Grand Valley best management practices based on the
hydro-salinity system proposed by Kruse (1977) . . 82
21 Best management practices for the Grand Valley
assuming the hydro-salinity budget of Kruse (1977)
and a threefold increase in lateral lining costs . 83
IX
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LIST OF TABLES
Number Page
1 Description of Farms in the Demonstration Area
Included in the 1973 Irrigation Scheduling
and Drainage Studies 19
2 Final Selection of Laterals Included in Project . . 28
3 Canals Served by the Major Canals in Grand Valley . 41
4 Hydraulic Characteristics of the Grand Valley
Canal and Ditch System 42
5 Consumptive Use Estimated For the Grand Valley ... 42
6 Seepage Data for the Fourteen Major Canals in
Grand Valley 44
7 Mean Annual Grand Valley Water Budget 47
8 Mean Annual Grand Valley Salinity Budget 48
9 Summary of Mean Annual Salt Pickup in Metric Tons
for Agricultural Sources in the Grand Valley ... 49
10 Cost-Effectiveness of Selected Land Retirement
Options 89
11 Cropland Business Multipliers Per Dollar of
Production in the Grand Valley 90
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ACKNOWLEDGMENTS
Four people have been instrumental in the pursuit of this
research program almost from its inception. The Project Officer,
Dr. James P. Law, Jr., has been an active participant in the
planning and development of the research approach, and his long-
term efforts and cooperative attitude that have allowed this
research program to be brought to a logical conclusion are
greatly appreciated. My colleague for many years, Dr. Wynn R.
Walker, has contributed most significantly to this research
effort in taking responsibility for much of the analysis. Mr.
George Bargsten, who began this research program with me in
September 1968 and continued throughout to be largely responsi-
ble for the field data collection, has my respect and gratitude
for his many years of hard, diligent work. Much of the experi-
mental design each year was dictated by the capability of our
water quality laboratory in Grand Junction, and this responsi-
bility fell upon Ms. Barbara F. Mancuso, who was meticulous in
the laboratory procedures, diligent in getting the samples
analyzed, and remained cheerful under pressure.
There are many people and organizations in the Grand Valley
who should be thanked for their contributions to this research
effort. Mr. Bob Henderson and Mr. Bill Klapwyck, who are
Managers of the Grand Valley Irrigation Company and Grand Valley
Water Users Association, respectively, have been deeply involved
in this research since its inception and have always been very
helpful in providing ideas and getting the work done. Mr. Chuck
Tilton, Superintendent of the Grand Junction Drainage District,
has also been heavily involved in the construction activities
and very helpful to the farmers participating in this research
program. The soil chemistry and crop yield studies were done
on land leased from Mr. Kenneth Matchett, an outstanding citi-
zen and farmer who was cooperative and more than helpful.
During the course of this project, three engineers served
in Grand Valley and were responsible for field operations;
namely, Mr. Orlando W. Howe, Mr. Ray S. Bennett, and Mr.
Robert G. Evans. I would particularly like to acknowledge the
efforts of Mr. Evans, who took responsibility for all of the
construction activities involved with the"lateral improvements
during the final demonstration phase.
The project benefited considerably from the many students
who participated in the research activities, particularly those
xi
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who spent 4-5 years with the project; namely, Mr. James H.
Taylor, Mr. Ted L. Hall, Dr. James E. Ayars, Mr. Berry J. Treat
and Mr. Charles W. Binder. Although he spent a shorter time
period on the project, Dr. J.W. Hugh Barrett contributed signi-
ficantly in his research on crop yield functions.
Finally, the individuals who should be acknowledged the
most are the farmers who participated in this research program.
We learned much from them. From irrigating some fields for a
few seasons ourselves, to studying irrigation problems and
farmer constraints, to modifying irrigation practices, to con-
structing physical improvements and the enormous task of opera-
ting these new systems as effectively as possible, it was all a
tremendous learning and sensitizing experience.
My sincerest thanks to all of you.
Gaylord V. Skogerboe
Principal Investigator
XI1
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SECTION 1
INTRODUCTION
COLORADO RIVER SALINITY PROBLEM
Mineral pollution is the most serious water quality problem
in the Colorado River Basin (Figure 1). The problem is serious
because the Basin is approaching conditions of full development
and utilization of the available water resources. Thus, while
the salinity problem may seem unique to basins of the arid V7est,
it will ultimately be faced by nonarid areas as the water use
approaches the available supply. Thus, the salinity control
program developed for the Colorado River Basin may be expected to
serve as a model for future programs in other basins.
The most serious problems resulting from the saline flows
are experienced in the Lower Colorado River Basin. Increasing
salinity concentrations are threatening the utility of water
resources in the downstream areas of Arizona, California, and the
Republic of Mexico. Detriments to agricultural water users are
primarily being encountered in Imperial and Mexicali Valleys,
while the primary urban detriments are occurring in Los Angeles
and San Diego. The U.S. Environmental Protection Agency (1971)
reported that existing damages to Lower Basin users would in-
crease from $16 million annually in 1970 to $51 million annually
by the turn of the century if planned developments do not include
appropriate salinity control measures, while more recent estimates
by the U.S. Bureau of Reclamation (USER) (Bessler and Maletic,
1975) show present damages at $53 million annually, which is
projected to be $124 million annually by the year 2000.
Approximately 10 million metric tons (11 million tons) of
salts are delivered each year in the water supply serving the
Lower Colorado River Basin. These salts reach Hoover Dam in
about 1.36 million hectare-meters (11 million acre-feet) of
water. Studies have indicated that roughly 37 percent of this
salt load is contributed by irrigated agriculture in the Upper
Colorado River Basin (Figure 2). Present salinity concentrations
necessitate treatment of water for both municipal and industrial
uses throughout the Lower Basin. In fact, concentrations at
times approach the tolerance of many high value crops such as
citrus, thus requiring the use of excessive quantities of water
for leaching and expensive water management programs.
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/Wyoming.
Utah ^vCoorado,
L—
Figure 1. The Colorado River Basin.
2
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Irrigottd Agriculture
37%
(8750T/d)
Net Runoff
52%
(72454 T/d)
Upper Colorado River
Basin
Average Salt Load,Metric tons/day
June 1965—May 1966
Natural Point Source*
and Well*
Municipal
(324 T/d) ond
Induttriol
Upper Main Stem
. Subba»in
Relative Magnitude of Salinity
Sources by River Basins of the
Colorado River
Grand Volley Area
ie% /or
Green River
Subbatin
Lowtr Main Stei
Subba»in
San Juan River
Subbo»in
Lower Colorado River
Basin
Average Salt Load,Metric tons/day
November 1963-October 1964
Net Runoff
Municipal
and
Induttrial
1% (58T/d)
Irrigated Agriculture
Upper Colorado
River Botin
Inflow
72%
(8920 T/d)
Figure 2. Relative magnitude and sources of salt in the
Colorado River Basin (U.S. Environmental Protection
Agency, 1971).
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The water quality problem in the Colorado River Basin has
obviously become chronic before full utilization of the water
resources has been realized. The philosophy surrounding future
developments will probably be one of accompanying each develop-
ment with a corresponding decrease in the salt load somewhere
else in the Basin in order to maintain present water quality
levels.
The Upper Basin water users are particularly affected by
these conditions because most of the future developments involve
interbasin transfers, in-basin oil shale developments, and
possible hydroelectric and thermalelectric production. None
of these water uses add significantly to the salt loading aspect,
but each diminish the quantity of water available for diluting
the salt loads already being carried. Consequently, future develop-
ment of water resources in the Upper Colorado River Basin must be
associated with more rigid salinity controls on the existing salt
sources, many of which are agriculture related.
In irrigated areas, it is necessary to maintain an acceptable
salt balance in the crop root zone, which requires some water for
leaching. However, when irrigation efficiency is low and convey-
ance seepage losses are high, the additional deep percolation
losses are subject to the highly saline aquifers and soils common
in the basin and result in large quantities of salt being picked
up and carried back to the river system. Therefore, a need
exists to delineate the high input areas and examine the manage-
ment alternatives available to establish the most effective
salinity control program.
That portion of the water supply which has been diverted for
irrigation but lost by evapotranspiration (consumed) is essentially
salt-free. Thus, the water percolating through the soil profile
contains the majority of salts originally in the water supply and
left behind by the water lost to evaporation and transpiration.
The net result is that the percolating soil water contains a
higher concentration of salts. This is referred to as the "con-
centrating" effect.
As the water moves through the soil profile, it may pick up
additional salts by dissolution. In addition, some salts may be
precipitated in the soil and there may be an exchange between
some salt ions in the water and in the soil. The salts picked up
by the water applied to the land are termed salt "pickup." The
total salt load from an irrigated area is the net increase of
salt in the irrigation return flows as a result of the concentrat-
ing effect plus the salt pickup (minus any precipitation of salts).
The most significant salt source in the Upper Basin is the
Grand Valley area (Figure 2) in west central Colorado. The
contribution to the total salt flows in the basin from this area
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is highly significant. The primary source of salinity is from
the extremely saline aquifers overlying the marine deposited
Mancos shale formation. The shale is characterized by lenses of
salt in the formation which are dissolved by water from excessive
irrigation and conveyance seepage losses when it comes in contact
with the Mancos Shale formation. The introduction of water
through these surface sources percolates into the shallow ground-
water reservoir where the hydraulic gradients displace some
water into the river. This displaced water has usually had
sufficient time to reach chemical equilibrium with the salt con-
centrations of the soils and shale. These factors also make the
Grand Valley an important study area, since the conditions en-
countered in the Valley are common to many locations in the
Upper Basin.
THE GRAND VALLEY
General Description
The Grand Valley is located in west central Colorado near
the western edge of Mesa County. Grand Junction, the largest
city in Colorado west of the Continental Divide, is the population
center of the Valley (Figure 3). The Grand Valley is a crescent
shaped area which encompasses about 49,800 hectares (123,000
acres) of which 57.7 percent or about 28,650 hectares (70,800
acres) are irrigated. Urban and industrial expansion, service
roads and farmsteads, idle and abandoned lands account for most
of the land not farmed. The Valley was carved in the Mancos
Shale formation (a high salt bearing marine shale) by the Colorado
River and its tributaries. The Colorado River enters the Grand
Valley from the east, is joined by the Gunnison River at Grand
Junction and then exits to the west.
Spectacular and colorful canyons flank the southwestern edge
of the Valley (Colorado National Monument). A steep escarpment
known as the Book Cliffs (which are the southern edge of the Roan
Plateau) rises from the Valley floor on the north; the 3,050
meter (10,000 feet above mean sea level) high Grand level lies
to the northeast; and distantly to the southeast the San Juan
Mountains can be seen; to the south and west lie the rough,
steep, deeply eroded hilly lands of the high terraces or mesas of
the canyon lands of the Colorado Plateau. Within the Grand Valley,
the irrigated lands have been developed on geologically recent
alluvial plains consisting of broad coalescing alluvial fans and
on older alluvial fans, terraces and mesas. Included in the
Valley lands are stream flood plains and various rough lands
occurring as terraces, escarpments, high knobs, and remnants of
former mesas.
The majority of the population of Mesa County resides in the
Grand Valley near and within the city limits of Grand Junction.
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x'Grand Valley
*
COLORADO
Grand Valley Salinity
Control Project
Boundary of Irrigated
Area
Figure 3. The Grand Valley, Colorado.
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In 1970 the population of the city of Grand Junction was 20,170,
which was 37 percent of the total Mesa County population. The
population has been growing steadily during the past decades, and
the 1974 estimated population of Grand Junction was 27,000 while
that of Mesa County was nearly 62,000. The projected 1990 popu-
lation of Mesa County is 90,000.
Grand Junction is a regional trade and service center for
the considerable agricultural and mining interests in western
Colorado, northwestern New Mexico, northeast Arizona, and eastern
Utah because of its access to major highways, rail and airline
systems. During the 1950's the area became and has remained
the center of the uranium exploration boom and several uranium
development projects sponsored by the government. Recent program
expansions related to energy have caused an economic upswing for
the area. At the present time, the Grand Valley is a focal supply
point for the budding oil shale and sodium bicarbonate (Nahcolite)
industries which lie to the north and west. The area is also a
supply and service center for a considerable oil and natural gas
drilling and exploration industry.
The diversified agricultural industry in the Valley is
comprised of both livestock and crop production activities.
Slightly less than 10 percent of the irrigated acreage is planted
to pome and deciduous orchards, the produce of which is processed
locally and may be shipped as far as the Atlantic seaboard. The
Grand Valley has long been a favored wintering area for cattle and
sheep which were grazed on high mountain summer ranges to the east
and north (Young et al., 1975).
An economic survey by Leathers (1975), along with the land
use inventory by Walker and Skogerboe (1971), indicates that
local farming is primarily a small unit operation. The population
engaged in agricultural activities is widely dispersed throughout
the Valley with most living on their property. Leathers (1975)
determined from sampling about 100 random selections that most
farm units were less than 40 hectares (100 acres) in size. Of
the total of 7,870 fields in the Valley, 50 percent are less
than 2 hectares (5 acres) in size (United States Department of
Agriculture-Soil Conservation Service (USDA-SCS), 1976).
The Grand Valley receives an average annual precipitation
of only 211 mm (8.29 inches) and practically all irrigation and
potable water supplies come from the nearby high mountain
snowpacks. The climate is marked by a wide seasonal range, but
sudden or severe weather changes are infrequent due primarily to
the high mountains surrounding the Valley. The usual occurrence
of precipitation in the winter is snow and during the growing
season is in the form of light showers from thunderstorms.
Severe cloudbursts occur infrequently during the late summer
months and hail storms are rare. Although temperatures have
ranged to as high as 40.6 degrees C (105 degrees F), the usual
-------
summer temperatures range to the middle and low 30's degrees C
(90's degrees F) in the daytime and around 15 degrees C (low
60's degrees F) at night. Relative humidity is usually low
during the growing season, which is common in all of the semi-
arid Colorado River Basin. The average annual relative humidity
is 58.8 percent. The prevailing wind direction is east-southeast
with an average velocity of about 13.4 kilometers per hour (8.3
mph) .
Enough variation in climate exists in the Valley to
separate the agricultural land use into three primary regions.
In the eastern end of the Valley, the protective proximity to
the abrupt Grand Mesa results in extended periods of frost-free
days which allows apple, peach, and pear orchards to abound. In
the western half of the Valley, the primary emphasis is on pro-
ducing corn, alfalfa, sugar beets, and small grains. (Sugar
beets are presently not grown in the Valley due to the closure of
the Holly Sugar factory in the fall of 1976.) Between these two
regions is a transition zone of small farms and the urban setting
of Grand Junction, the population center of the area.
Historical irrigation development in the Grand Valley was
reported in detail in an earlier EPA report, "Evaluation of Canal
Lining for Salinity Control in Grand Valley," (Skogerboe and
Walker, 1972) and only a very brief summary will be presented
here.
Although the early explorers concluded that the Grand Valley
was a poor risk for agriculturally related activities, the first
pioneering farmers rapidly disproved this notion with the aid of
irrigation water diverted from the Grand and Blue Rivers (now
the Colorado and Gunnison Rivers, respectively) entering the
Valley. Through a long struggle, an irrigation system evolved to
supplement the otherwise meager supply of precipitation during
the hot summer months. The first large-scale irrigation in the
Valley began in 1882 with the construction of the Grand Valley
Canal (now the Grand Valley Irrigation Company), which was pri-
vately financed. Other private systems were built during the
period between 1882 and 1908 when construction started on the
last major system, which was the Grand Valley Project by the
USER. The last major construction was completed in 1926: The
Grand Valley Project consists of two divisions: The Garfield
Gravity Division and the Orchard Mesa Division on the north and
south sides of the river, respectively.
The futility of irrigation without adequate drainage was
quickly demonstrated to early settlers in the Valley as some low
lying acreages became waterlogged with highly saline groundwater.
Today, the failure to completely overcome these conditions is
still evident. For example, of the more than 28,600 hectares
(70,800 acres) of irrigable cropland, almost one-third is either
in pasture or idle. An examination of land use in Grand Valley
-------
by Walker and Skogerboe (1971) indicated a large fraction of the
12,000 to 16,000 hectares (30,000 to 40,000 acres) of phreato-
phytes and barren soil were once also part of the irrigated
acreage. Evidence exists that these same lands were once highly
productive and subsequently ruined by overirrigation and
inadequate drainage.
Two main irrigation entities divert water from the Colorado
River. These are the Grand Valley Water Users Association (USER
Project) and the Grand Valley Irrigation Company. A third irri-
gation company, the Redlands Power and Water Company, diverts
water from the Gunnison River. A number of smaller companies
have carriage agreements with the two major canals for delivery
of Colorado River water. These include the Palisade Irrigation
District (Price Ditch) and the Mesa County Irrigation District
(Stub Ditch), who have such an agreement with the Grand Valley
Water Users Association (Government Highline Canal). The Grand
Valley Irrigation Company is composed of several smaller canals,
including the Mesa County Ditch, Kiefer Extension, the Inde-
pendent Ranchman's, and others. The irrigation system of the
Valley, consisting of about 287 kilometers of canals, is shown in
Figure 4.
- Discharge capacities at the head of the canals range from 20
m /sec (700 cfs) in the Government Highline Canal to 0.8 m /sec
(30 cfs) in the Stub Ditch and diminish along the length of each
canal or ditch. The lengths of the respective canal systems are
approximately 74 kilometers (46 miles) for the Government High-
line Canal, 35 kilometers (22 miles) for the Price, Stub, and
Redlands Ditches, 125 kilometers (78 miles) for the Grand Valley
system, and 53 kilometers (33 miles) for the Orchard Mesa Canals.
The capacities, dimensions, and seepage losses of the canals in
the Valley are summarized in Tables 4 and 6 in Section 4.
The term lateral is used in this text to refer to those
small conveyance channels which deliver water from the company
canals to the farmer's fields. These small channels usually
carry flows less than 0.14 m /sec (5 cfs) and range in size up to
1.2 or 1.5 meters (4 or 5 feet) of wetted perimeter. There are
about 600 kilometers (373 miles) of laterals in the Grand Valley
as determined by the USER (1976). Not counting the Redlands area
of the Valley, there are 1,553 laterals in the Valley (USER,
1976).
When water is turned into the lateral system, it becomes the
responsibility of the users entitled to the diversion and not the
ditch company. The only exception is the Government Highline
Canal which sometimes treats their larger laterals as small
canals and turnout water at headgates on these laterals.
However, no effort is made beyond the headgate.
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Legend
Boundary of Irrigated Area
Grand Valley Salinity Control
Demonstration Project
Ufp Approximate Extent of Cobble
£££££££} Aquifer
Seal* HI Kilom«t«rs
Figure 4. Grand Valley canal distribution system and approximate areal extent of
cobble aquifer.
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Single users served by an individual turnout are not
uncommon, but most laterals serve several irrigators who decide
among themselves how the lateral will be operated. Most of the
multiple-user laterals/ which may serve as many as 100 users, run
continuously throughout the irrigation season with the unused
water being diverted into the drainage channels. USER (1976)
figures show that the average irrigated acreage served by a
lateral is between 10 and 15 hectares (25 to 37 acres).
The prevalent method of applying water to croplands in the
Valley is furrow irrigation. Small laterals carrying 0.03 to
0.14 cubic meters per second (1 to 5 cubic feet per second)
divert water from the company or district operated canal systems
to one or more irrigators. Water then flows into field head
ditches where it is applied to the lands to supply moisture to
the growing crops and maintain a low salinity root zone environ-
ment in order to sustain plant growth.
The predominantly alfalfa, corn, sugar beet, orchard, and
small grain economy is served by a more than adequate water
supply. The 28,665 hectares (70,830 acres) of irrigable crop-
land encompassed within the irrigation system enjoys a total
diversion of more than 2.4 hectare-meters per hectare (8 acre-
feet per acre) during normal years. Considering that the poten-
tial evapotranspiration of these croplands is usually less than
0.9 hectare-meters per hectare (3 acre-feet per acre), it is
obvious that existing water use efficiencies are low. There is
no groundwater used for irrigation purposes. The abandonment
and withdrawal of farmlands for other uses has also contributed
to the surplus of water since there has been no reduction in
diversions. Most of this "excess" water is wasted into the
drains.
Geology
The geologic formations throughout the Colorado River Basin
were laid by an inland sea which covered the area. After the
retreat of the sea, the land masses were uplifted and subsequent
erosion has created the mountains and plateaus as they are
today. As shown in Figure 5, the upper formations are sandstones
and marine shales which are underlaid by the marine Mancos Shale
and the Mesa Verde formations. Mancos Shale is a very thick
formation that lies between the underlying Dakota sandstones and
the overlying Mesa Verde formation. The thickness of the Mancos
Shale usually varies from between 900 to 1,500 meters (3,000 and
5,000 feet). Due to its great thickness and its ability to be
easily eroded, this shale forms most of the large valleys of
western Colorado and eastern Utah. These formations occur in
about 23 percent of the Basin in such locations as the Book
Cliffs, Wasatch, Aquarius and Kaiparowits Plateaus, the cliffs
around Black Mesa and areas in the San Juan and Rocky Mountains.
The Grand Valley was created by erosion, which cut through the
11
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GRAND
UNCOMPAHGRE UPLIFT
CENOZOIC
TERTIARY
(EOCENE)
C (PALEOCENE)
MESOZOIC
ARCHEZOlC
Figure 5. Geologic cross-section of the Grand Valley.
-------
upper formations creating the Valley in the Mancos Shale. This
formation is the main source of the salt contribution to the
Colorado River. Due to its marine origin, the shale contains
lenses of salt which are easily dissolved as water moves over
the shale beds. Water moving over and through the shale origi-
nates from overirrigation and leakage from the canals and
laterals. Since the overlying soil is derived from the shale,
it is also high in salts and contributes significantly to the
salinity of return flows.
Because of the marine origin of the shale, it contains a
very high percentage of water soluble salts which can be readily
seen in the many patches of alkali (white and black) in both
irrigated and nonirrigated areas. The types of salts which are
present in the shale are mostly calcium sulfate with smaller
amounts of sodium chloride, sodium sulfate, magnesium sulfate,
and calcium and magnesium carbonates. In fact, the minerals
gypsum and calcite (calcium sulfates) are commonly found in
crystaline form in open joints and fractures of the Mancos
Shale, as well as in the soil profile.
The Mancos Shale is a "dark-gray (black when wet) clayey
and silty or sandy, calcareous gypsiferous" deposit of marine
origin and Upper Cretaceous in age (Schneider, 1975). In the
portion of the Valley lying north of the Government Highline
Canal (Figure 4), Mancos Shale is an exposed erosional surface.
Essentially no irrigation is practiced in this portion of the
Valley. Intermittent ridges of Mancos Shale are exposed in the
area bounded, approximately, by the Government Highline Canal on
the north and the Grand Valley Canal on the south. These shale
ridges have a general north-south trend and represent remnants
of a shale terrace which has been dissected by southward flowing
streams that began in the Book Cliffs. The southern extremities
of these ridges (approximately the Grand Valley Canal) are the
remnants of the shale cliffs that once formed the northern bank
of the Colorado River (Schneider, 1975).
With time, the Colorado River migrated southward in an
approximately horizontal plane until it reached its present
position. During this period, the river deposited what is now a
cobble aquifer that extends from the present river location
northward to, approximately, the Grand Valley Canal (Figure 4).
Migration of the Colorado River to the south decreased the
gradient of southward flowing tributaries, and the Valley was
gradually filled with alluvial deposits transported by the
tributaries. These tributary deposits buried the Colorado River
bedload and flood plain deposits (Schneider, 1975). It is the
tributary alluvium, deposited during the Quaternary, that forms
the source of most of the irrigated soils in the Valley. In
recent time, local washes have again cut down into the alluvial
deposits and into the Mancos Shale at many locations.
13
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Recent downcutting into the Mancos Shale bedrock is most prevalent
near the north edge of the irrigated region where the tributary
deposits are relatively thin.
The alluvial deposits overlying the cobble aquifer and/or
the Mancos Shale are saline clays and silts derived mainly from
Mancos Shale in the Book Cliffs area and from shaly members of
the Mesa Verde Group. Where the cobble aquifer is absent, the
clay soils are in contact with a weathered shale zone, below
which is the unweathered Mancos Shale. Due to the compactness
of the clay and silt particles making up the shale, the forma-
tion is not considered water-bearing at depth. However, the
weathered zone near the surface does transmit small quantities
of water along joints, fractures, and open bedding planes. In
this zone, the percolating water, which primarily originates
from the overirrigation of cropland and seepage losses from
canals and laterals, dissolves the salts directly out of the
shale. The weathered shale can be recognized by its brownish-
gray to brown color as compared to the darker gray of the
unweathered shale. The weathered shale also exhibits joints,
and disintegration and separation along the bedding planes.
These features account for the permeability of the weathered
shale.
The cobble aquifer that underlies the tributary alluvium in
much of the irrigated region of the Valley is locally under
artesian pressure, and the water table aquifer in the overlying
alluvium is a perched aquifer. The two aquifers are not hydrauli..
cally independent; however, there is sufficient permeability in
the confining layer to permit interchange of waters. At some
locations, the confining layer is apparently absent and there is
direct hydraulic connection between the tributary alluvium and
the cobble layer. A typical geologic cross-section of the area
can be seen in Figure 6 which indicates the approximate lateral
extent of the aquifer.
RESEARCH APPROACH
The inflow-outflow analysis reported by the U.S.
Environmental Protection Agency (1971) showed that the Grand
Valley was the largest agricultural source of salt loading per
hectare of irrigated land in the Colorado River Basin.
Consequently, the Grand Valley became the initial focus of
research studies to evaluate the effectiveness of various agri-
cultural salinity control measures for reducing the salt loading
reaching the Colorado River.
Water entering the near-surface aquifers in the Valley
become heavily laden with salts dissolved from the soils and
aquifers of marine origin which occur extensively in the area.
The primary source of these soils and aquifers is the Mancos
14
-------
o
o
Legend
| Fine Gravel
] Silty Clay Loam Soils
1 Cobble Aquifer
N
3
•O
3-
CO
J Tight Cloy ( Discontinuous)
h_-_-^.- Moncos Shale Bedrock
L71
Orchard
Mesa
-o
Scalt I Mile
Horizontal Scolt
Figure 6. A typical geologic cross-section in the Grand Valley, indicating the
approximate areal extent of the cobble aquifer.
-------
Shale formation which was formed as a result of the alternate
advance and recession of the great inland seas once dominating
the western United States. Since the water entering local
aquifers comes mainly from irrigation channel seepage and deep
percolation from excessive and inefficient irrigations, the
emphasis of a salinity control program is to maximize the effi-
ciencies of both the conveyance and farm water-use subsystems.
Canal and Lateral Lining
Aside from the numerous studies in the Grand Valley to
evaluate local conditions, this effort, the Grand Valley Salinity
Control Demonstration Project, was the first study conducted in
the area to determine the effect of salinity management practices
on conditions in the Basin. The project was funded on a matching
basis by the Environmental Protection Agency in conjunction with
the Grand Valley Water Users Association, Palisade Irrigation
District, Mesa County Irrigation Company, Grand Valley Irrigation
Company, Redlands Power and Water Company, and the Grand Junction
Drainage District to further the development of pollution con-
trol technology in the Basin. Each of these entities had repre-
sentatives on the Board of the Grand Valley Water Purification
Project, Inc. (later renamed Grand Valley Canal Systems, Inc.),
which was formed to contract with the Federal government to con-
duct this demonstration project. The primary objective of the
initial project was to demonstrate the feasibility of reducing
salt loading in the Colorado River system by lining conveyance
channels to reduce unnecessary groundwater additions.
The project was composed of three study areas selected for
their different characteristics commonly found in the Valley.
Area I, shown in Figure 7, was chosen as an intensive study area
in which the bulk of the investigation was to be conducted and
also included most of the construction effort. This area was
designated for detailed investigations regarding effects of
conveyance linings on the water and salt flow systems in an
irrigated area. The intensive study area was selected for its
accessibility in isolating most of the important hydrologic
parameters, but had the important advantage that it allowed five
irrigation companies to participate in one unit. Area II was
selected because it represented a different landform several
miles west of Area I along a short section of the Grand Valley
Canal where high seepage losses had resulted in a severe drainage
problem. Area III was located along a section of the Redlands
First Lift Canal, which is supplied from the Gunnison River and
was selected to evaluate the effect of a different soil type and
drainage condition.
The preconstruction and postconstruction evaluation of
canal and lateral lining was based upon a hydro-salinity model
having two basic subsystems, surface water and groundwater.
16
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Stub Ditch
Government
Highline —
Canal
Figure 7. Intensive study area for the Grand Valley Salinity
Control Demonstration Project and location of irri-
gation scheduling and drainage study farms.
17
-------
The study was conducted to collect and analyze sufficient data
to define in detail both the water and salt flow systems
(Skogerboe and Walker, 1972). This report also provides a
summary of previous investigations concerned with irrigation and
drainage in Grand Valley, as well as a history of irrigation
development in the Valley. A complete land use inventory of the
entire Grand Valley (Walker and Skogerboe, 1971) was undertaken
(along with some sampling programs throughout the irrigated area
to define lateral lengths, field,head ditches, etc.) in order to
allow the results from the intensive study area to be projected
valley-wide.
Irrigation Scheduling and Drainage
The activities begun in 1968 to evaluate canal and lateral
linings' as- salinity control measures demonstrated the need for
further investigations concerning on-farm management practices.
As a result, a second-and-third-phase program was undertaken to
determine the feasibility of two farm management improvements—
irrigation scheduling and field relief drainage—in controlling
salinity.
Five fields in the demonstration area were incorporated
into the second and third phases of the studies to represent
a cross-section of agricultural practices in the Grand Valley.
These farms, located in Figure 7 and described in Table 1, were
included in an irrigation scheduling service implemented in the
Valley by the local USER office, thereby allowing the efforts of
this investigation to be coordinated with the USER.
Since the intensive study area is characteristically
operated by small unit farmers and the soils are severely
affected by the high-water table conditions, agricultural pro-
ductivity is not presently sufficient to support most of the
occupants, and many have outside jobs in local businesses or
industry. One of the concerns of the investigators was in
demonstrating the value of the irrigation scheduling service to
these individual landowners. In addition, these lands were once
among the Valley's most productive (at the turn of the last
century) and a significant impetus could be generated locally in
support of salinity control programs if such measures were
effective in returning these lands to a high level of agricultural
productivity.
During the second phase study, an effort was made to
evaluate irrigation scheduling under various management condi-
tions ranging from little or no improvements in on-farm irri-
gation practices to maximum use of the scheduling recommendations.
Three of' the farms, namely the Kelleher, Canaday, and Wareham
farms, were included primarily as part of the third phase of
this project involving field drainage, but were included in the
scheduling program to yield a linkage between the two studies.
18
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TABLE 1. DESCRIPTION OF FARMS IN THE DEMONSTRATION AREA
INCLUDED IN THE 1973 IRRIGATION SCHEDULING AND
DRAINAGE STUDIES.
Farm
Martin
Bulla
Canaday
Kelleher
Wareham
Crop
Corn
Barley
Corn
Barley
Oats
Pasture
Alfalfa
Crested
Wheatgrass
Crop
Acreage
9.2
10.7
15.0
17.1
9.8
1.0
17.4
13.6
Field
Capacity
22.3
24.2
23.9
26.5
25.0
25.8
30.5
29.3
Wilting
Point,
%
10.7
13.4
12.1
12.8
12.2
14.1
16.7
16.7
19
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The two fields referred to as the Martin and Bulla farms were
intensively studied to evaluate the potential for salinity
control resulting from irrigation scheduling, along with the
requirements for maximizing this potential in the Grand Valley
with structural and nonstructural improvements in the irrigation
system.
For the third phase study, irrigation practices and drainage
problems were monitored on the Kelleher, Canaday, and Wareham
farms during the 1972 irrigation season. Then, during the
spring of 1973, a perforated plastic pipe drainage system was
constructed on the Wareham farm. All three farms were then
incorporated into the irrigation scheduling program during the
1973 irrigation season.
Soil Chemistry and Crop Yield Studies
Predicting Chemical Quality—
The hydro-salinity model developed under the first phase of
this research program describes the present situation in the
study area regarding water and salt flows. However, the only
method for predicting the reduction in salts returning to the
river through implementation of any salinity control measure(s)
is by assuming a one-to-one relationship between water and salt.
That is, if the subsurface return flow is reduced by 50 percent,
the salt pickup is also reduced by 50 percent. In order to
overcome this limitation, a project "Irrigation Practices,
Return Flow Salinity, and Crop Yields" was initiated.
Three adjacent fields containing 9.3 hectares were leased
for this study (Figure 8). The area was divided into 54 plots
which were 30.5 meters by 30.5 meters in size, two plots which
were 12.2 meters by 61 meters, two plots which were 12.2 meters
by 91.4 meters, and five plots which were 12,2 meters by 152
meters. Each plot was used for a different replication of the
crop, fertilizer and irrigation treatments. They were con-
structed so that each plot performed as a large lysimeter. A
trench was excavated slightly into the shale along the lines
dividing the plots, with the depth to shale varying from 1 to 6
meters, and the average being 3 meters. A plastic curtain was
then placed vertically in the center of the trench to divide the
individual plots. The lower edge of the curtain was "sealed" to
the shale by backfilling to the original elevation of the shale
with compacted clay. Consequently, the shale floor and plastic
membrane walls act to create a box around each plot, with each
plot serving as a large lysimeter.
The drainline encased in a gravel filter material was then
placed at about the same elevation of the shale, inside the
curtain, and continued around the periphery of the plot. Upon
leaving the plot area, the water was transported via solid
pipeline to a measuring station where water quality and quantity
were monitored.
20
-------
City of
Grand Junction
Scale
Figure 8. Location map of the soil chemistry and crop yields
study area.
21
-------
The irrigation system was designed to deliver water through
a closed conduit to each plot and allow measurement of the flows
onto each plot. Since furrow irrigation is used almost exclu-
sively throughout the Valley, this method was employed in the
experiments.
The crops that were grown consisted of corn, grass, alfalfa
and winter wheat, since these are the main crops grown commer-
cially in the Valley (except the Jose Tall Wheatgrass, which was
grown as a highly salt tolerant crop that could be used in
reclaiming highly saline lands). By varying irrigation timing
and amounts and nitrogen fertilizer levels on the different
plots, and by monitoring quality and quantity of both inflow and
outflow waters, the effects of these parameters on return flow
salinity and crop yields were evaluated for corn and wheat.
A salt and water budget could be developed for each plot
and compared to those developed for the other plots. From these
data, equations could be developed to predict the variation in
chemical quality (including ionic constituents) of the moisture
movement through the soil profile, as well as the salt pickup
resulting from movement of subsurface irrigation return flows.
These results could then be combined with the hydro-salinity
model to evaluate the effectiveness of various salinity control
measures in reducing the salt load reaching the Colorado River
(Skogerboe et al., 1978a).
Crop Yield Functions—
To determine the economically optimal allocation of
irrigation water to a given crop, the relationship between the
yield of the crop and its use of the supplied water must be
known. Studies of this relationship, particularly those con-
sidering the grain yield (the reproductive organ) of the crop,
have generally resulted in a curvilinear line of best fit being
drawn through a scatter of data. More recent studies (including
this research program) indicate that this scatter of data largely
results from the time of occurrence of water deficits in relation
to the stage of growth. Crops are far more sensitive to moisture
stress during some stages (i.e., pollination in corn) than
others. If a crop is supplied a seasonal quantity of water less
than its potential requirements, exaggerated yield reduction
could occur if the deficit occurs during periods of such sensi-
tivity. The scatter in data can be considerably reduced,
therefore, if deficits are so timed that they cause the least
yield reduction for the given quantity of water supplied
(Skogerboe et al., 1978b).
The research plots used in the soil chemistry studies were
used to investigate the effects upon yield of stressing corn
and wheat during the different stages of growth. The corn was
differentiated in three subsequent growth stages. Stage I was
from the emergence and establishment stage through the main
22
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period of vegetative growth preceding tasseling. Stage II was
the pollination period from tasseling to the blister kernel
stage, and Stage III was the grain filling period from blister
kernel to physiological maturity. These growth stages coincide
with those of Stewart et al. (1975), although some subjectivity
is involved in the differentiation between growth stages.
Water was applied to the corn weekly during one, two or
three of the growth stages, giving eight different treatments
(Figure 9). Each treatment was replicated four times. The
eight plots within a replication were grouped contiguously to
provide approximately equal depth to shale within the replication.
These plots being watered within a growth stage were
watered once a week with a net amount calculated to be slightly
in excess of the crop requirements. Thus, in the early stages
it was planned that the watered plots would receive approxi-
mately 40 mm per week, rising to 65 mm per week during the
period of peak demand. Stressing during a particular growth
stage was achieved by eliminating all irrigation from the
stressed plots during that growth stage. Rainfall which fell
during the growing season was light and infrequent, allowing a
high degree of stress to be applied.
The winter wheat plots were similarly differentiated
according to growth stage, although to a somewhat limited scale
due to experimental work with the wheat not beginning until the
spring following its winter dormancy. All plots were watered
during the week beginning the 17th of May, when in the late boot
stage; after which two growth stages were considered, the
anthesis period and the grain filling period. Three plots
received water only during the first stage (1-0), two plots
received water only during the second stage (0-1), three plots
received water during both stages, (I-I), and two plots received
no water at all during both of these stages (O-O). Approximately
50 mm (net) of water was applied per week to those plots being
irrigated.
Development of Technological Package
Economically feasible means of controlling salinity
associated with irrigation return flows had been evaluated
individually and independently in previous investigations. In
order to extend these results to the formulation of comprehensive
plans for controlling salinity on a large scale, it was necessary
to describe the interrelationships which exist among the
alternatives. Prior to this project, some limited evidence had
indicated that the functions describing costs and effectiveness
of specific salinity control measures were nonlinear. Therefore,
if salinity control measures are not mutually exclusive, then an
"optimal" salinity control strategy would consist of a combination
23
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Growth Stage:
I Pre-emergence plus
I Post-emergence
Irrigation
5 Irrigations
Legend:
I = Irrigation
0- Non-irrigation
Plant
m
4 Irrigations Designation
0-0-0
0-0-1
0-1-0
O-I-I
I-0-0
I-O-I
I-I-O
Secondary Rooting
Tassel
Emerge a Estobish | Vegetative Period
Blister Kernel
I-I-I
JGrc
Mature
Pollination Period [Groin Filling Period
6 Weeks I 5 Weeks 4 Weeks I 5 Weeks
29th April 13th June 13th July 15th August 17th September
Figure 9. Irrigation treatments for corn.
-------
of several alternatives. The respective composition of such a
strategy would depend on the relative magnitude of each hydro-
logic segment of an irrigated area. Thus, an important step in
solving salinity problems was to investigate the nature of
improvements incorporating several alternatives, or in simpler
terms, assessing the impact of a "package" of salinity control
measures.
The primary objective of this final demonstration phase was
to show the advantages of implementing a "package" of technologi-
cal improvements within the lateral subsystem. Although major
emphasis was upon on-farm improvements, considerable improvements
in the water delivery conveyances and some improvements in
lowering high-water tables (drainage) were also required.
This demonstration phase utilized each of the salinity
control measures previously evaluated in Grand Valley, with the
additional use of various irrigation methods to demonstrate the
complete package of salinity control measures. No single
measure will adequately alleviate the salt load from an irri-
gated area, while a complete package of salinity control measures
can be expected to reduce the salt load beyond the sum of each
individual measure because of improvements in the operation and
management of each lateral.
The intensive study area in the Grand Valley, which had
been used for evaluating the effectiveness of canal and lateral
lining, irrigation scheduling, and tile drainage in reducing the
salt load entering the Colorado River, was also used for this
demonstration project. In order to facilitate the continued
participation by the irrigation interests in the Grand Valley,
the laterals were selected to cover as many canals as possible.
The final selection, as shown in Figure 10, had two laterals
under the Government Highline Canal, one under the Price Ditch,
three under the Grand Valley Canal, and three under the Mesa
County Ditch. It should be pointed out that the lands served by
the Government Highline Canal in the demonstration area are
served under carriage contract with Mesa County Irrigation
District (Stub Ditch) and the Palisade Irrigation District
(Price Ditch). Therefore, all the irrigation entities in the
demonstration area were involved directly in the project.
The laterals were selected to capitalize on previous work
regarding canal and lateral lining, irrigation scheduling, and
drainage studies. The selection of a lateral as a subsystem
rather than an individual farm, had a tremendous advantage in
allowing control of water deliveries at the lateral turnout. In
this way, both the quantity of flow and the time of water
delivery could be controlled, facilitating improved water
management throughout the subsystem.
25
-------
Seal* I Milt
Scale I Kilomtttr
I 1
Water Supply
Land Under Study Lateral
Hydrologlc Boundary
Canal or Ditch
. Drain or Wash
Grand Valley Canal
Stub Ditch
*
m
lovernment
j Highline
/ Canal
,*V.
•' Price Ditch
I
X
Figure 10. Location of the nine selected lateral subsystems incorporated in the
project.
-------
The experimental design for the preevaluation was primarily
aimed at providing specific information for the 330.7 hectares
(817 acres) undergoing treatment listed in Table 2. The field
data collection program allowed the design of irrigation and
drainage facilities and provided sufficient data to allow pre-
dictions of salinity benefits which resulted from each specific
salinity control measure.
A variety of irrigation methods were demonstrated,
including adjusting or "tuning-up" present irrigation methods
being used in the study area. Considerable experience had been
gained in improving the existing irrigation methods while
evaluating irrigation scheduling as a salinity control measure.
in the Grand Valley. In addition, more advanced irrigation
methods had been evaluated as to salinity benefits in the Grand
Valley. The irrigation systems constructed under this project
included automated farm head ditches, sprinkler irrigation, and
trickle irrigation (Evans et al., 1978a, and Evans et al., 1978b).
Although the postevaluation included the monitoring of
water and salts entering and leaving the demonstration area, the
primary emphasis was the on-site evaluation of each specific
salinity control measure. The on-site evaluation was then
compared with the results of the total demonstration area hydro-
salinity monitoring program. The concurrent EPA research
project, "Irrigation Practices, Return Flow Salinity, and Crop
Yields," which was also conducted in the Grand Valley, was
utilized in developing the cost-effectiveness of each salinity
control measure. The combined results of these two projects
were extremely important in establishing the benefits to be
derived from implementing a salinity control technology package.
A two-day "Field Days" was conducted during the third year
of this project in the month of August, 1976, which was attended
by approximately 800 people. This event was primarily directed
toward the growers in the Grand Valley and secondly to irri-
gation leaders (mostly growers) throughout the Upper Colorado
Basin. State and Federal agency personnel also attended. This
was coupled with an irrigation equipment show and was cosponsored
by the Colorado State University Cooperative Extension Service.
27
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TABLE 2. FINAL SELECTION OF LATERALS INCLUDED IN
PROJECT
Lateral
Identification
HL C
PD 177i/ I/
GV 92
GV951/1/
GV 160
MC 3
MC l()i/
MC 30^/
Canal
Highline Canal
Highline Canal
Price Ditch
Grand Valley Canal
Grand Valley Canal
Grand Valley Canal
Mesa County Ditch
Mesa County Ditch
Mesa County Ditch
TOTAL
Area
Hectares
13.1
35.9
27.8
24.3
79.1
78.7
3.7
54.0
14.1
330.7
Acres
32.4
88.6
68.8
59.9
195.7
194.3
9.0
133.4
34.7
816.8
Irrigators^
1
2
6
6
13
8
1
9
_1
47
I/ These laterals were part of the earlier EPA funded canal and lateral
lining study.
2/ This lateral was part of the earlier EPA funded field drainage study.
3/ This lateral consolidated an additional 70 acres from two other
laterals.
4_/ A portion of this lateral was included in the previous EPA funded
irrigation scheduling program.
5_/ An irrigator is defined as a person who farms more than one acre.
In actuality, 89 persons are involved in the operation of this
project.
28
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SECTION 2
CONCLUSIONS
1) Of the 10 million metric tons of salt annually reaching
the Lower Colorado River Basin, 600,000 to 700,000 metric tons
are annually contributed by the Grand Valley. The salt load
contribution from Grand Valley is the result of saline subsur-
face irrigation return flows reaching the Colorado River. The
alluvial soils of Grand Valley are high in natural salts; how-
ever, the most significant salt source is the Mancos Shale
formation underlying these alluvial soils which contain crystal-
line lenses of salt which are readily dissolved by the subsurface
return flows.
2) The irrigation water supply is at least three times
greater than the crop water requirements. Although much of this
excess water returns to open drains as surface runoff, which has
negligible impact upon the salinity in the Colorado River, there
are still significant quantities of water that reach the under-
lying Mancos Shale formation, then pass into a near-surface
cobble aquifer, where the water is displaced into the Colorado
River. These subsurface return flows are the result of seepage
losses from canals and laterals, and excessive deep percolation
losses from overirrigation of the croplands.
3) The excessive irrigation water supplies are the result
of early development of irrigation systems in Grand Valley.
The Grand Valley Irrigation Company has the first right (earliest
priority) to water on the Colorado River in the state of
Colorado. During extreme drought years, only the Government
Highline Canal has to reduce its diversions. However, the
irrigable acreage under each system has been substantially
reduced by the addition of roads, homes, stockyards, etc., and
the water supply is applied to less acreage.
4) The irrigation companies usually terminate their
responsibility to the irrigators at the turnout gates along the
canals which discharge water into the laterals. Generally, the
water users under each lateral are only informally organized,
and the lack of flow measuring devices greatly hinders their
ability to equitably distribute the waters.
29
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5) The combination of geologic setting, early water rights
that yield abundant irrigation water supplies, reduction in
irrigated acreage, lack of responsibility of irrigation companies
to individual water users, the almost complete absence of flow
measuring devices along the laterals, and the low annual charges
(costs) for irrigation water all contribute to the salinity
problem.
6) The abundant water supply has also created waterlogging
and salinity problems for farmers in Grand Valley. Abandoned
irrigated lands and reduced agricultural productivity of the
lower lands are visual evidence of these problems. Salt accumu-
lations on the ground surface are visible at numerous places
throughout the Valley.
7) Soil chemistry studies showed that the salinity
concentration of the deep percolation losses were independent
of the volume of deep percolation, because the concentration of
salt below the root zone produces a saturated gypsum and lime
condition which is relatively constant. Groundwater chemistry
data also show that the concentration of salt in the cobble
aquifer, although double the concentration of deep percolation
immediately below the crop root zone, is still relatively con-
stant owing to the solubility limits of the major salts. Thus,
the salt loading due to irrigation return flow can be calculated
from a knowledge of the water balance for the Grand Valley. The
reductions in salt loading reaching the Colorado River will be
directly proportional to reductions in subsurface irrigation
return flows (seepage and deep percolation losses).
8) Based upon the field data collection program which was
incorporated into a water balance analysis, the sources of sub-
surface return flow (and consequently salt loading) are: (a)
canal seepage 23 percent; (b) lateral seepage 32 percent; and
(c) deep percolation losses 45 percent.
9) The salinity control cost-effectiveness associated with
each alternative improvement is the basis for determining the
formulation of an implementation policy. Studies reported in
the technical literature indicate that the salinity damages in
the Lower Colorado River Basin range from $150 to $350 per
metric ton per year when extended to the Grand Valley. Local
benefits to the project such as increased crop yields, reduced
irrigation system maintenance costs, increased land values and
other factors were not evaluated as part of this report and
are not included in the cost-effectiveness of the various
alternatives.
10) Concrete slip form lining or low-head PVC plastic
lining of laterals are almost equal in cost-effectiveness and
can reduce salinity at substantially less cost than the $150/
metric ton value. Concrete slip form linings offer the
30
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advantages of easier and less frequent maintenance than pipelines,
and they are more acceptable to local irrigators. Pipelines,
on the other hand, are easier and more rapidly installed and
can be installed by the farmer as part of his matching cost
requirements.
11) Use of high-head PVC pipe (SDR 81 or greater) or
concrete pipe is not a cost-effective alternative to concrete
linings or low-head PVC and should be discouraged. Attendant
problems with the use of low-head pipe can be overcome by
giving particular attention to design and rigorous installation
specifications.
12) Field head ditch lining by concrete slip form or gated
pipe have comparable cost-effectiveness values, and while cost-
ing more than twice as much as lateral linings to remove a unit
of salinity, they still cost considerably less than the $150/
metric ton value.
13) Evaluation of alternative methods of irrigation implies
that cropland evapotranspiration can be well estimated. Three
empirical approaches were used in this study: (a) the Blaney-
Criddle method; (b) the Jensen-Haise method; and (c) the Penman
method. The Blaney-Criddle approach underestimated lysimeter
data by about 40 percent on a seasonal basis; corrections in
the temperature coefficient reduced this seasonal error to zero,
but estimates were still substantially in error for monthly
time periods. The Jensen-Haise approach overestimated seasonal
evapotranspiration by approximately 5 percent with a 10-15
percent error during the early spring windy periods. The
Penman approach was better than the Jensen-Haise method in esti-
mating seasonal values, but was not better at approximating
the seasonal distribution of evapotranspiration.
14) Irrigation scheduling by itself is not a significant
salinity control alternative, but is a necessary part of any
strategy for improved water management in order to maximize the
effectiveness of physical improvements. Scheduling should be
referenced to the areas of a field receiving the least amounts
of water, and then related to the operation of the irrigation
system so that the duration of a water application is equal to
the time required to refill the "least watered" root zone areas.
In sprinkler irrigation, the least watered or "critical" areas
would be along the shortest diagonal distance between two
sprinklers on adjacent laterals; whereas for surface irrigated
systems, it is at the lower end of the field.
15) Improved agronomic practices can be effectively
utilized in the irrigation scheduling program. Field experi-
ments with corn and wheat in Grand Valley showed that irrigation
could be halted before the crop reached physiological maturity,
allowing the stored soil moisture to carry the crop through
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to harvest. At least one irrigation can be eliminated, which
would result in decreased deep percolation losses. This practice
not only improves yields, but also allows the soil to be drier
for harvest, allows better utilization of winter precipitation
and retains more nutrients in the root zone, particularly nitro-
gen, for use by subsequent crops.
16) A common practice in the Grand Valley is to plant crops
half way between two furrows and then irrigate to provide suffi-
cient moisture for germination. This practice contributes
significantly to deep percolation losses and can be inexpensively
reduced by changes in cultural practices such as planting in or
on the edge of a furrow. New furrows can be made at a later
time when the crop has partially developed a root zone.
17) Furrow irrigation is the predominant method of water
application in the Grand Valley. Existing application effi-
ciencies [(available root zone storage/applied water) x 100] are
about 64 percent. Strict adherence to the scheduling philosophy
outlined in (14) above would result in application efficiencies
of 85 to 90 percent, but this appears to be unrealistic without
substantial investments in automation. The cut-back method of
furrow irrigation was demonstrated in the Valley at about the
same cost-effectiveness for controlling salinity as head ditch
linings.
18) Border irrigation is applicable in the Grand Valley,
but not presently accepted. Graded borders have approximately
the same potential application efficiency as furrow irrigation,
while the costs would be higher due to higher land leveling
requirements. In addition, border irrigation requires more
skilled labor and a higher degree of management than is presently
available in the area.
19) Level borders offer potential for reducing salt loading
if problems with soil crusting can be controlled. The level
borders also require a high level of management capability and
would be quite adaptable to automation.
20) Properly managed sprinkler systems offer a large
potential for reducing salt loading from irrigation return flows.
Solid-set systems are not presently cost-effective in the Grand
Valley, whereas the less expensive moveable systems (side-roll,
etc.) are very competitive in an on-farm salinity reduction
program. Achievable application efficiencies for sprinkler
irrigation are 85 to 95 percent depending on the level of
management of the system.
21) Trickle irrigation is cost-effective for orchard
crops and has the greatest potential for reducing return flow
salinity from these areas. However, it can be applied to less
than 10 percent of the Valley. Due to the large cost of these
32
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systems, trickle irrigation has a much poorer cost-effectiveness
than properly managed surface irrigation systems.
22) Since sprinkler and trickle irrigation methods are not
controlled by soil properties, changing to these systems poten-
tially would have a very large impact on reducing the salt load-
ing from the early season irrigations. These early irrigations
are responsible for more than 50 percent of the total annual salt
load resulting from irrigation return flows in the Grand Valley.
23) A comparison of the cost-effectiveness relationships
of the various irrigation system improvements indicates that
head ditch linings, gated pipe, and/or automated cut-back furrow
irrigation will reduce salinity for approximately $100-$110 per
metric ton per year (i.e., one ton of salt will be eliminated
from the Colorado River each year over the life of the improve-
ments at an initial investment of $100-$110 for the first year's
ton). A limit of 146,500 metric tons per year is amenable to
this alternative. Sprinkler irrigation could be utilized to
extend local salinity control to 171,000 metric tons per year,
at a cost of more than $130 per ton. The maximum control would
be achieved through massive conversion to trickle irrigation
(227,000 metric tons per year) at a cost of about $200 per ton.
24) Comparison of on-farm salinity control methods on a
cost-effectiveness basis in the Grand Valley indicates that
these measures are second only to lateral linings in feasibility.
25) Canal linings reduce salt loading at unit costs ranging
from $190 to $700 per metric ton of salt removed.
26) Desalting in conjunction with pump drainage can be
expected to become feasible to reduce salt loading at approxi-
mately $320 per metric ton.
27) Field relief drainage is infeasible for agricultural
salinity control at any cited figures for downstream detriments.
28) Cost-sharing programs are highly effective in attracting
irrigators to participate in programs for improving the lateral
and on-farm components of the irrigation system, provided ade-
quate technical assistance is available. Allowing individual
irrigators to use their labor to meet all or part of their
matching cost requirements certainly contributed to the ease of
accomplishing the goals of the demonstration project.
29) In Grand Valley, the jurisdiction of the irrigation
companies does not include the laterals in most cases, so there
are no formal arrangements for managing the irrigation water
supply and settling disputes among water users. The informal
organizational arrangements used for the lateral improvement
program, although satisfactory on most of the laterals, resulted
33
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in numerous problems on a few laterals as far as collecting
required matching funds for the project, as well as some diffi-
culties in implementing improved irrigation practices.
30) Water delivery and irrigation application systems can
be designed so that the irrigation has to be efficient for conti-
nued operation. Also, strict influent controls of the quantity
of water diverted to a field should result in efficient irri-
gation. Both of these alternatives require substantial technical
assistance to the growers to be effective.
31) Individual on-farm improvements should be the result
of individual negotiations between the irrigator and technical
assistance personnel. However, there is a clear need to involve
irrigators in all phases of salinity related improvements.
Where irrigators participated in design decisions, the systems
were not always the most efficient, but were certainly the most
workable and flexible from the standpoint of the water users.
Participation in the actual construction provided operational
insight, understanding of neighbor needs, a pride in workmanship,
and in some cases, a more rapid completion of the work than by
contractual methods.
32) Proper water management requires a strong emphasis
toward on-farm water control structures, especially flow measure-
ment devices. This project utilized standardized means for
determining water flow rates. All flow measurement devices were
designed or selected to be read directly by the farmers without
the use of printed tables.
33) A large amount of technical assistance is required
in working with farmers in designing on-farm improvements that
suit their individual needs, to negotiate the financial terms,
construction of the improvements, and assisting the irrigator in
the proper management of his new system.
34) The implementation of a lateral and on-farm improvements
program will result in excess water being available for renting
or leasing to water users upstream from the Grand Valley.
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SECTION 3
RECOMMENDATIONS
As a result of this rather extensive research project,
there are several recommendations which can be made concerning
the implementation of a "total" salinity control program.
1) Implementation of an action salinity control program
in the Grand Valley should consist primarily of lateral improve-
ments (i.e., concrete slip form lining or low-head PVC plastic
pipe) and on-farm improvements. The lateral improvement pro-
gram, the on-farm program, and the irrigation scheduling pro-
gram should be integrated into a single program which plans,
constructs, and operates a combination of improvements moving
from one lateral to the next. The design of the on-farm
improvements should not be separate from the lateral improve-
ments. The programs, therefore, should be handled by one
federal agency, most likely the Soil Conservation Service (SCS)
since they have had considerable experience in this subject
area in the Grand Valley. In addition, due to the small sizes
of the laterals, the design criteria of the SCS are adequate.
2) Concrete lining of the Government Highline Canal
should be postponed until completion of basinwide studies on
cost-effectiveness of salinity control alternatives in other
irrigated areas. Also, a canal lining program should wait
until sufficient feedback is obtained from the lateral and on-
farm improvements program, so that an accurate assessment of
reductions in lateral diversions can be made, in order to
properly size the canal, rather than constructing a canal which
would have a larger capacity than necessary.
3) The use of metering headgates is recommended for closed
conduit flows. Propeller meters should not be used due to
excessive problems with sediment and maintenance. Other methods
such as a constant head orifice are not justified economically
for the small increase in discharge measurement accuracy. Open
channel flow should be measured with Cutthroat flumes rather
than Parshall flumes because of cost and ease of installation.
4) The plan of improvement must include sufficient flow
measurement structures throughout the lateral subsystem to
facilitate equitable distribution of the water supplies and
improved irrigation practices.
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5) The use of high-head plastic PVC pipe, transits
(asbestos-cement) or concrete pipe is not recommended for lateral
lining, because they are not cost-effective when compared to
low-head (50-foot) plastic pipe or trapezoidal slip form
concrete lining.
6) For lateral improvement programs which require the
collective action of the irrigators served by a lateral, there
is a need to encourage the users to formally organize under the
corporate laws of the State of Colorado that apply to irrigation,
which will: (a) substantially facilitate contractual arrange-
ments for lateral improvements; (b) provide a much simpler
means of handling matching cost requirements; and (c) provide a
better means of implementing a comprehensive water management
program for each lateral.
7) The prevalent method of water application should remain
furrow irrigation. Fields larger than 10 hectares (which are
very few) should be encouraged to convert to mobile (side-roll,
etc.) sprinkler systems, whereas the limited orchard area should
utilize trickle irrigation.
8) Furrow irrigation system improvements should involve
lining head ditches with slip form concrete or gated pipe.
Automation of the head ditch system with cut-back, pump-back,
or a combination of these two should be implemented.
9) Land leveling should not be implemented on a large
scale since infiltration rates are generally low and slopes are
comparatively high. Uniformity of water applications is not a
serious problem under Grand Valley conditions when cut-back or
pump-back systems are used.
10) Training materials should be developed to instruct
farmers in the use of proper irrigation practices, motivate
them to be efficient by illustrating the potential for yield
increases and salt loading reductions, and demonstrate the
feasibility of the salinity control program.
11) The success of any salinity control program rests
finally with the degree of participation of the farmers them-
selves. Farmers who have made exceptional progress in improving
their on-farm water management practices should be given special
recognition. Adequate numbers of technical assistance personnel
should be available to help the irrigators develop such pro-
ficiencies with their system and develop a higher level of water
management. However, the existing levels of technical assistance
personnel needed to work with farmers are insufficient, parti-
cularly trained manpower with on-farm water management experience.
Thus, special training courses should also be prepared and given
to these individuals.
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12) Once the physical facilities are completed on a lateral,
a program of "scientific" irrigation scheduling should be used
to maximize the effectiveness of the physical improvements. The
agency in charge of the on-farm and lateral lining program should
be given responsibility for the irrigation scheduling program.
The service should also include pesticides and fertilization
scheduling assistance to the local growers. After a number of
years, the irrigation scheduling program should be turned over
to the Grand Valley Canal Systems, Inc. Revenues from water
transfers can be used to pay for this service, or farmers can
be charged for this service through their annual water cost
assessment fees.
13) Efficient irrigation methods and practices should be
designed and can be mandated or constructed by: (a) having
the irrigation delivery and application systems designed so as
to require highly efficient methods for their viable operation;
and (b) using strict influent control standards for the quantity
of water diverted for each acre. Both of these alternatives
will require a large amount of technical assistance to effect
the desired changes.
14) The implementation program should be monitored,
evaluated, and continuously refined. This process will not only
maximize the effectiveness of the Grand Valley Salinity Control
Program, but will provide valuable information and experience
for implementing irrigation return flow quality control programs
in other areas of the West. An annual review of the program
should be conducted with participation by all involved parties.
15) The State Engineer's Office should develop standards
and criteria for beneficial use of irrigation water in Grand
Valley, which will limit the farm water deliveries. In con-
junction, influent standards should be used, with an initial
standard being the present water duty. The success of an
influent control approach is dependent upon: (a) use of numerous
flow measuring devices; (b) adequate technical assistance for
working with and advising farmers on improved irrigation
practices and methods; and (c) availability of funds for making
the necessary structural improvements.
16) State legislation should be enacted that would
authorize the irrigation companies in Grand Valley to sell, rent
or lease the excess water resulting from this salinity control
program to water users upstream from Grand Valley. The revenues
from such water transfers should be used to line the canals or
make other structural improvements to the delivery system.
17) New industries which require further water development,
such as energy complexes, and interbasin water transfers should
be allowed to offset their salinity detriments (which are
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primarily salt concentrating effects) by lining a sufficient
length of the Grand Valley Canal or make other structural
improvements in the irrigated areas.
18) Preliminary evidence suggests that irrigation of urban
lawns, landscapes and parks may contribute approximately the
same salt loading per hectare as agricultural water uses.
Therefore, a salinity control program should be developed and
tested for urban lawns, parks, golf courses, etc. in the Grand
Valley.
19) The relative impact of on-farm improvements in reducing
the salinity of the Colorado River ought to be considered
throughout the Basin before plans are finalized for the Grand
Valley. In other words, on-farm and lateral lining improvements
in the Grand Valley, coupled with similar programs in other
areas, may be more cost-effective than complete off-farm full-
scale improvement programs (canal lining, desalting, drainage,
etc.) in the Grand Valley. However, the lateral lining and on-
farm improvement programs for the Grand Valley should be
initiated immediately.
20) The ultimate level of salinity control decided upon for
the Grand Valley should be evaluated in a basinwide context.
The marginal costs of salinity control are linearly distributed
and, therefore, other areas will be better sites for salinity
control efforts than plans approaching full-scale control in
the Grand Valley. Consequently, the Grand Valley studies of on-
farm improvements should be extended to other irrigated areas in
the Upper Colorado River Basin.
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SECTION 4
GRAND VALLEY HYDRO-SALINITY SYSTEMS
In the 1960's, a concerted effort was undertaken to
identify the sources of salinity in the Colorado River Basin.
The Federal Water Pollution Control Administration, then within
the Interior Department, utilized United States Geological
Survey (USGS) stream gaging data as well as an extensive water
quality sampling program to identify the major salt contributors
in the Basin (United States Environmental Protection Agency,
1971). The Grand Valley in western Colorado was described as
one of the largest agricultural sources of salinity (about 18
percent of the total Upper Basins' agriculturally related contri-
bution) , and it subsequently became the site for the first studies
to evaluate field-scale salinity control measures.
The early studies identified the Grand Valley as a major
problem area by mass balancing water and salt flows into and
out of the Valley region. Similar investigations by lorns et
al. (1965) and Hyatt et al. (1970) produced supportive results,
although a substantial variability in the specific nature of
the Grand Valley salinity problem emerged. Since that time, a
great many individual calculations describing the Valley salt
loading and the respective components have been made, but very
little agreement existed until early 1977 when most studies were
completed. Although some variability still exists among the
various investigative groups, the differences are sufficiently
close that they become relatively unimportant in evaluating
optimal salinity control policies for the Valley.
Problem Identification
The procedures for delineating the water-salt flow system
in an irrigated area are collectively termed hydro-salinity
budgeting, or hydro-salinity modeling, since computers are
generally needed to handle the large number of necessary
calculations. In the Grand Valley, the composition of this
system has been extensively investigated at various levels of
sophistication. As the salinity investigations were continued,
refinements in the Valley's basinwide impact have been made and
verified. Interestingly, the research evolution in the Grand
Valley case study suggests a fairly sound approach for other
areas as well.
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Remedying irrigation return flow quality problems can be
divided into four logical steps. First, the magnitude of the
problem and the downstream consequences must be identified in
relation to the irrigated area's individual contribution to the
problem. In this way, the most important areas can be delineated
for further consideration, thereby making the most cost-effective
use of available personnel and funding sources. As noted pre-
viously, the inflow-outflow analysis by EPA (1971) led to the
conclusion that initial research efforts should concentrate in
the Grand Valley. Next, the components of the problem must be
segregated. In most large areas, the costs of studying the
entire system are prohibitive, so smaller "sampling" studies are
conducted (the demonstration area) from which projections are
made to predict the behavior of the entire area. The third step
is to evaluate management alternatives on a prototype scale in
order to assess their cost-effectiveness and develop a sensiti-
vity concerning the capability for implementing such technologies.
And finally, if the measures which can be applied are effective
in reducing salinity, are economically feasible, and are accept-
able to the farmers, the final step is the actual application,
or implementation, of the technologies in order to alleviate the
water quality problem.
The Grand Valley was identified as an important agricultural
source of salinity in the Colorado River Basin through a series
of analyses involving mass balance of the Valley inflows and
outflows. lorns et al. f!965) evaluated stream gaging records
for the 1914 to 1957 period, concluding that the net salt loading
(salt pickup) from irrigation in the Valley ranged from about
450,000 to 800,000 metric tons annually. This range of numbers
has been generated independently by Hyatt et al. (1970), Walker
(1970), Skogerboe and Walker (1972) , Westesen (1975), and the
USGS (1976). More recent consideration of data by the writers
and others indicates a long-term salt pickup rate between
600,000 to 700,000 metric tons/year. This figure is now
generally accepted by the various research groups and action
agencies involved with the Grand Valley salinity investigations.
The fact that the Valley's salinity contribution has been
such a disputed figure over the last few years exemplifies the
importance of establishing the total Valley contribution. In
areas like the Grand Valley, where the total impact is only 5
to 8 percent of the river inflows or outflows, the impact of
irrigation must be established using statistical analyses of the
available data. However, the natural variability can cause
serious errors in conclusions regarding salt pickup if not
tempered by other data and analyses. For example, a major
problem in early investigations was deciding how much of the
inflow-outflow differences was due to natural runoff from the
surrounding watershed. Because of the meager precipitation
locally, the writers assumed the natural salt contribution
would be negligible. This conclusion was later substantiated
40
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partially by Elkin (1976) who estimated an upward limit for the
natural contribution of about 10 percent of agricultural sources.
Segregating the Irrigation Return Flow System
In the Grand Valley, as in numerous other irrigated areas,
water is supplied to the cropland in a canal and lateral con-
veyance system. Water is diverted from the Colorado and Gunnison
Rivers into three major canals: (a) the Government Highline
Canal; (b) the Grand Valley Canal; and (c) the Redlands Power
Canal. These large canals in turn supply the smaller canals and
ditches as listed in Table 3.
TABLE 3. CANALS SERVED BY THE MAJOR CANALS IN GRAND VALLEY
Government Redlands
Highline Grand Valley Power
Canal Canal Canal
Stub G.V. Mainline Redlands #1
Price G.V. Highline Redlands #2
Orchard Mesa Power Mesa County
Orchard Mesa #1 Kiefer Extension
Orchard Mesa #2 Independent Ranchmen's
A description of the hydraulic characteristics of these
canals and ditches is given in Table 4, based on information
provided by the USER. From the canals and ditches, water is
diverted into the small, largely earthen laterals leading to the
individual fields. This lateral system of approximately 600
kilometers of ditch carrying from 0.06 - 1.0 m3/sec. A frequency
distribution of the lateral lengths based on data provided by the
USER (1976b) indicated that the average length is about 400
meters, with an average capacity of about 0.10 mvsec.
Nearly all farmers in the Valley apply water using the
furrow irrigation method. The Soil Conservation Service (SCS)
inventory (1976) of the irrigation system indicates over 9,000
individual fields in the Valley having a wide range of widths,
slopes and lengths. The typical field is 140 meters wide, 160
meters long, with a slope (toward the south generally) of 1.125
percent. A frequency distribution of field acreages showed the
typical field encompassing a little more than 2 hectares.
Calculating the length of unlined field head ditches based on
the SCS data indicates a total unlined length of 1300 kilometers
(1640 km total).
Irrigation water is applied to approximately 25,000 hectares
during the course of a normal irrigation season (Walker and
Skogerboe, 1971). This acreage has been substantiated by the
recent SCS inventory and generally accepted by the other
agencies.
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TABLE 4. HYDRAULIC CHARACTERISTICS OF THE GRAND VALLEY CANAL
AND DITCH SYSTEM
Initial Terminal Initial
Length Capacity Capacity Perimeter
Name (km) (mYsec) (nr/sec) (m)
Government Highline Canal
Grand Valley Canal
Grand Valley Mainline
Grand Valley Highline
Kiefer Extension of
Grand Valley
Mesa County Ditch
Independent Ranchmen's
Ditch
Price Ditch
Stub Ditch
Orchard Mesa Power Canal
Orchard Mesa #1 Canal
Orchard Mesa #2 Canal
Redlands Power Canal
Redlands #1 & #2 Canals
73.70
19.80
21.70
37.00
24.50
4.00
17.40
9.50
11.30
3.90
24.10
26.10
2.90
10.80
16.99
18.41
7.08
8.50
3.96
1.13
1.98
2.83
0.85
24.07
3.12
1.98
24.07
1.70
0.71
14.16
0.71
3.96
0.71
0.06
0.85
0.28
0.11
24.07
0.17
0.17
24.07
0.06
19.19
16.67
13.86
12.62
7.25
6.67
3.17
7.27
2.94
18.20
6.46
3.58
16.88
3.95
Based upon lysimeter data reported by Evans et al. (1978a),
the weighted average consumptive use demand by the irrigated
portion of the area equals about 0.745 meters per season. A
breakdown of the individual consumptive uses in the Valley is
given in Table 5.
TABLE 5. CONSUMPTIVE USE ESTIMATED FOR THE
GRAND VALLEY
Consumptive Use
Volume Depth
in ha-m in Meters
Open water surface evapora-
tion and phreatophyte use1 3,450
Open water surface evapora-
tion and phreatophyte use2 8,400
Cropland3
TOTAL
18,600
30,450
0.138
0.336
0.745
1.219
1adjacent to river
2along canals and drains
3approximate area of 25,000 ha
The irrigation return flow system in the Valley may be
divided according to whether or not the return flows are surface
42
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or subsurface flows. Surface flows occur as either field
tailwater or canal, ditch, and lateral spillage. Subsurface
flows include canal and ditch seepage, lateral seepage, and
deep percolation from on-farm applications (deep percolation in
this sense to include head ditch and tailwater ditch seepage).
Canal and Ditch Seepage—
Since the early 1950"s, five major seepage investigations
of the major canals and ditches have been conducted (Skogerboe
and Walker, 1972 and Duke et al., 1976). Although seepage rates
have been noted over a wide range, some representative rates are
presented for the 14 canals listed in Table 6, which in turn,
have been used to compute the seepage volume for each canal and
ditch. In the Grand Valley, the total canal seepage is estimated
to be approximately 3,700 ha-m per year.
The seepage rates vary for each canal. The writers, using
published data, applied the trends to the Grand Valley Canal,
the Orchard Mesa System, and the Redlands System where data are
few. The seepage rate from the Grand Valley Canal is assumed to
be substantially lower than the value listed for the Government
Highline Canal, even though both have similar capacities,
because of the high-water table conditions surrounding the Grand
Valley Canal along much of its length. The overall differences
in the Valley budgets as summarized by Walker et al. (1977) and
Kruse (1977) can be largely attributed to the differences in
assigning seepage rates. The latter data reflect an approxi-
mately uniform application of the Government Highline Canal
seepage rates.
Lateral Seepage—
Tests reported by Skogerboe and Walker (1972) and Duke et
al. (1976) indicate seepage losses from the small ditches com-
prising the lateral system probably average about 8 to 9 ha-m/
km/year in the Grand Valley. Thus, for the 600 km of small
laterals, the total seepage losses are approximately 5,300 ha-m
annually. Combined lateral and canal seepage is, therefore,
approximately 9,000 ha-m annually.
On-Farm Deep Percolation—
Numerous studies in recent years have attempted to quantify
deep percolation from on-farm water use. Skogerboe et al.
(1974a, 1974b) estimated these losses (including head ditch and
tailwater ditch seepage) to be about 0.30 ha-m/ha. Duke et al.
(1976) estimated these losses, independent of on-farm ditch
seepage, to be 0.15 ha-m/ha. Minutes of the Grand Valley
Salinity Coordinating Committee show on-farm ditch seepage to
be 0.12 ha-m/ha (Kruse, 1977). Combining the figures given by
Duke et al., (1976) with Kruse (1977) gives a total on-farm
subsurface loss of 0.27 ha-m/ha. Given the large number of
fields tested by various investigators, total on-farm seepage
and deep percolation losses are probably about 7,500 ha-m per year,
43
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TABLE 6. SEEPAGE DATA FOR THE FOURTEEN MAJOR CANALS IN
GRAND VALLEY
Name of Canal or Ditch
Government Highline
Grand Valley
Grand Valley Mainline
Grand Valley Highline
Kiefer Extension
Mesa County
Independent Ranchmen's
Price
Stub
Orchard Mesa Power
Orchard Mesa #1
Orchard Mesa #2
Redlands Power
Redlands 1 & 2
Days in
Operation
214
214
214
214
214
214
214
214
214
365
214
214
365
214
Seepage Rate
m3/nr/day
0.091
0.045
0.061
0.061
0.061
0.061
0.061
0.061
0.061
0.076
0.076
0.076
0.065
0.137
Seepage
Volume
ha-m
1,653
291
251
516
160
24
60
60
30
195
160
104
116
80
3,700
Canal Spillage and Field Tailwater—
The operational wastes and field tailwater are difficult
to define because, first, they do not generally create problems
associated with salinity degradation, and second, data regarding
these flows are sparse. Skogerboe et al. (1974a) listed field
tailwater as 43 percent of field applications, whereas Duke et
al. (1976) reported estimates of field tailwater and canal
spillage or administrative wastes which were 18 percent and 35
percent, respectively. Estimates of spillage and tailwater by
the USER were slightly smaller than the authors' estimate.
Using the 43 percent figure for field tailwater and the 18 per-
cent figure for canal spillage yields about 37,000 ha-m per year
for field tailwater and spillage.
Aggregating the data presented previously with inflow-
outflow records in the vicinity of Grand Valley gives a clear
picture of how the irrigation system relates to the overall
hydrology (Figure 11). The flow diagram is particularly helpful
in visualizing the relative magnitude of the irrigation return
flows from the agricultural area in comparison with the flow in
the Colorado River.
Identifying the Salinity Contribution
The salinity contribution of the Grand Valley hydro-
salinity system can be developed in a number of ways.
44
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Plateau Creek Inflow/^
(I3,800ha-m)
Colorado River Inflow
( 297,650 ha -m)
Cropland
Precipitation
. ( 3,IOOha-m)
Gunnison River Inflow
( 178,000 ha-m)
Evaporation 8 Phreatbphyte Use
Canal Diversions Adjacent to River ( 3,450 ha-m)
( 69,000 ha-n\) / ^^ |rrigation from Return Flow ( 45,100 ha-m)
Canal a Lateral
Seepage
(9,CX)Oha-m
Tailwater ft
SpjJ Is (37,000 ho
Net Evaporation ft
Phreatophyte
Evapotranspiration
{ 8,40Oha-m)
ep Percolation
(7,500 ha-m)
Cropland Evapotranspiration
( 18,600 ha-m)
Colorado River
Outflow
(462,IOOha-m)
Figure 11. Mean annual flow diagram of the Grand Valley hydrology.
-------
For example, if the annual salt pickup is divided by the volume
of groundwater return flow (630,000 tons/8,100 ha-m), the average
concentration of the return flow due to salt pickup can be
determined (7,800 m/Jl) . Data reported by Skogerboe and Walker
(1972) indicated an average groundwater salinity of 8,000 to
10,000 mg/i (average of 8,700 mg/£), and, if the irrigation
water salinity is 500-1,000 mg/£, these figures agree quite
closely.
The USGS and others have recently measured surface drainage
return flows at selected areas in the Valley. These data indi-
cate an average salinity of about 4,000 mg/£. Thus, as Duke
et al. (1976) pointed out, if all return flows were through the
drainage channels and phreatophyte consumptive use was not con-
sidered, the calculation of salt pickup would result in an
estimated valley-wide contribution of approximately 660,000 tons.
Consequently, the two salt loading figures, as predicted by
inflow-outflow mass balancing and calculations using local data,
are sufficiently close to be confident in the values. Based on
the figures pointed out in these preceding paragraphs, the salt
loading due to irrigation in the Grand Valley can be segregated
as follows:
1) Canal and Ditch Seepage 23 percent
2) Lateral Seepage 32 percent
3) On-farm Losses 45 percent.
Summary
At the time of this writing, there are two principal
hydro-salinity budget estimates for the Grand Valley as mentioned
previously. In various meetings and conferences, the differences
have been noted and the essential areas of disagreement
identified. The writers believe an examination of the budgets
prove useful. Tabular budgets of the Grand Valley water and
salt volumes are presented in Tables 7 and 8. It should be
noted that the basis of the Kruse (1977) estimate has been
expanded to be congruent with the analyses of Walker et al.
(1977).
Probably no other issue has been considered more among the
several research and planning groups associated with the Grand
Valley than the net salt loading from the Valley. This figure
is central to any salinity study because it defines the
boundaries within which each segment of the agricultural hydro-
logy must fit. By subtracting the salt carried in the irri-
gation water supplies from the volume of subsurface and drainage
return flow, the net agricultural contribution can be delineated
in metric tons annually as listed in Table 9.
The reader will note that the essential differences lie in
two areas: (a) canal seepage; and (b) deep percolation.
46
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TABLE 7. MEAN ANNUAL GRAND VALLEY WATER BUDGET (ALL UNITS
IN HECTARE-METERS)
!/ I/
River Inflows
Plateau Creek 13,800 13,800
Colorado River nr. Cameo 297,650 297,650
Gunnison River nr. Grand Junction 178,000 178,000
489,450 489,450
Evaporation and Phreatophyte Use (net) 3,450 2,950
Canal Diversions
Lateral Diversions 52,900 54,100
Seepage 3,700 7,620
Operational Wastes 12,400 22,100
69,000 83,820
Lateral Diversions
Seepage 5,300 6,100
Field Tailwater 24,600 25,140
Cropland Consumptive Use 18,600 19,100
Cropland Precipitation -3,100 -3,100
Deep Percolation 7,500 6,860
52,900 54,100
Irrigation Return Flows (Subsurface
Canal Seepage 3,700 7,620
Lateral Seepage 5,300 6,100
Deep Percolation 7,500 6,860
Phreatophyte Withdrawals (net) -8,400 -8,400
8,100 12,180
Irrigation Return Flows (Surface)
Operational Wastes 12,400 22,100
Field Tailwater 24,600 25,140
37,000 47,240
River Outflows
Colorado River at Colorado-Utah
State Line 462,100 462,100
I/ Walker et al. (1977)
2/ Kruse (1977)
47
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TABLE 8. MEAN ANNUAL GRAND VALLEY SALINITY BUDGET (ALL UNITS
IN METRIC TONS) __
River Inflows
Plateau Creek 62,600 62,600
Colorado River nr. Cameo 1,352,600 1,352,600
Gunnison River nr. Grand Junction 1,371,700 1,371,700
2,786,900 2,786,900
Canal Diversions
Lateral Diversions
Seepage
Operational Wastes
301,100
21,100
70,600
392,800
307,900
43,400
125,800
477,100
Lateral Diversions
Seepage
Field Tailwater
Deep Percolation
Irrigation Return Flows (Subsurface)
Canal Seepage
Lateral Seepage (adjusted for
Deep Percolation salt pickup)
30,200
140,000
130,900
301,100
163,200
232,200
416,800
812,200
34,700
143,100
130,100
307,900
268,500
231,700
368,000
868,200
Irrigation Return Flows (Surface)
Operational Wastes (0 pickup)
Field Tailwater (0 pickup)
Natural Diffuse Sources
River Outflows
Colorado River at Colorado-Utah
State Line
70,600
140,000
210,600
30,000
125,800
143,100
268,900
72,600
3,445,900 3,518,500
I/ Walker et al. (1977)
2/ Kruse (1977)
48
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TABLE 9. SUMMARY OF MEAN ANNUAL SALT PICKUP IN METRIC TONS FOR
AGRICULTURAL SOURCES IN THE GRAND VALLEY
Walker et Kruse Ratio
al. (1977) (1977) (2)/(l)
(1) (2) (3)
Canal Seepage
Lateral Seepage
On-Farm Ditch Seepage
Deep Percolation
142,100
202,000
95,000
190,900
630,000
225,100
197,000
103,500
129,800
655,400
1.58
0.98
1.09
0.68
1.04
The difference in canal seepage can be attributed solely to the
assignment of seepage losses to respective conveyances whereas
the deep percolation differences reflect the fact that both
budgets were developed from extending data collected at different
sites. The relative confidence in each study is about equal and
the interested reader may review the technical reports if he
chooses to examine this issue further. In a realistic sense,
however, these differences are relatively unimportant, as will
be demonstrated in later sections.
49
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SECTION 5
TECHNOLOGICAL ALTERNATIVES FOR SALINITY CONTROL
IDENTIFICATION OF POTENTIAL SOLUTIONS
Prevention or control of water quality degradation due
to irrigation return flow is both difficult and expensive to
achieve. Potential solutions and control measures involve
physical changes in the system, which can be brought about by
constructing improvements to existing systems or by placing new
institutional influences upon the system, or a combination of
both. Since irrigation return flow is an integral part of the
hydrologic system, control measures for managing the return flow
from an irrigated area must be compatible with the objectives
for water resource management and development in the total
system (Skogerboe and Law, 1971).
This section is presented to outline the potential
technological solutions to the irrigation return flow problem in
the Grand Valley. These solutions have been classified into
three groups: (a) improving water conveyance, including canals
and laterals; (b) on-farm water management; and (c) water re-
moval, including drainage and desalting. These groups conform to
the three subsystems in an irrigation system; namely, water
delivery, on-farm water use, and water removal (Skogerboe and
Law, 1971).
Water entering the near-surface aquifers in Grand Valley
displaces highly mineralized waters from these aquifers into the
Colorado River. In any area where the water is in prolonged
contact with soil, the concentration of mineral salts tends
toward a chemical equilibrium with the soil. In Grand Valley,
as in many other areas, high equilibrium salinity concentrations
are known to exist in the near-surface aquifer. The key to
achieving a reduction in salt loading is to lower the ground-
water levels, which will result in less displacement of water
from the aquifer into the Colorado River. The most effective
means for lowering groundwater levels is to reduce the source of
groundwater flows, which can be accomplished by reducing seepage
through canal and lateral lining or by reducing deep percolation
loss'es resulting from excessive irrigation by improved on-farm
water management practices. Since a leaching requirement is a
necessary part of local irrigation, some deep percolation
50
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losses can be expected under the most efficient irrigation
practices. Therefore, relief tile drainage systems are also
realistic salinity control alternatives when deep percolation
and seepage losses, which have lower salinity concentrations
than flows in the lower reaches of the groundwater system, can
be intercepted and removed before equilibrium concentrations are
reached. Also, drainage systems, either tile or pumping, must
be considered in combination with desalting, along with the
other adaptable salinity control measures.
IMPROVING WATER DELIVERY
Water is a surplus commodity in the Grand Valley because of
its excellent water right priorities and the construction of
homesteads, roads, and urban complexes have reduced the original
irrigated acreage about 30 to 40 percent. Thus, instead of the
originally developed 1.76 ha-m/ha water duty, there is now a
diverted supply of about 2.74 ha-m/ha. The results are three-
fold. First, the history of development in the western United
States has always shown water to be a valuable commodity to an
area since the rights not historically diverted are subject to
abandonment. The Grand Valley irrigation authorities have felt
they must divert their rights for fear of losing them. In
short, it is not the practice of agriculture to be wasteful, but
the laws regulating the use of water dictate that a user either
be wasteful or give up a valuable right. The second result is
that there is no incentive to manage water efficiently because
it is cheap and plentiful. And finally, most irrigation system
improvement programs are initiated to reduce losses because
supplies are short or to reduce maintenance. In the Grand
Valley, the abundance of low cost water has economically dis-
couraged efforts to reduce losses, so the existing system
remains largely earthen channels.
The salinity associated with the conveyance system is
attributable directly to seepage losses. Indirectly,
rehabilitation and improved operation, management, and mainte-
nance of the network of canals and laterals affect the use of
water on the farm itself. This section will be divided into a
discussion of canal and lateral systems.
Canal Lining and Management
The basic element in improving canal and ditch systems is
the lining or piping of the channels so that seepage is
alleviated. In the construction of these improvements, new
turnout structures and water measurement devices are incor-
porated which improve the control and distribution of water,
thereby providing a stimulus to irrigators for more efficient
water utilization. The Bureau of Reclamation's 1975-1976 esti-
mates of the costs to line the major canals in the Valley with
51
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concrete was slightly more than $40 million (USER, 1976a).
Referring to Tables 4 and 6 in the previous section, and assum-
ing the linings would reduce seepage by approximately 80 percent,
indicates that the average cost per ton of salt reduced is $200
to $360/metric ton.
When water is turned into the lateral system, it becomes
the responsibility of the users entitled to the diversion.
Single users served by an individual turnout are not uncommon,
but most laterals serve several irrigators who decide among
themselves how the lateral will be operated. Most of the
multiple-use laterals, which may serve as many as 100 users, are
allowed to run continuously with the unused water being diverted
into the drainage channels. This practice would be almost
completely eliminated if the only water diverted was that quan-
tity appropriated to each acre in the company water rights. In
addition, the employment of a demand system, based upon irri-
gation scheduling and limited by the water duty for the crop-
land, would be highly beneficial in improving crop yields while
reducing subsurface irrigation return flows. The costs that
would be passed on to the irrigator for a more regulated canal
system would also provide added incentive for more efficient
water management practices below the canal turnout. Thus, there
would be an indirect economic incentive for better management.
Lateral Lining and Management
The benefits which would accrue from lining the lateral
system in an area like the Grand Valley are essentially the same
as described earlier concerning the canal linings. However,
because of the vast extent and generally poor conditions of the
lateral system, the effect of the laterals is much greater than
the canals. As with the canal system, the appurtenances, such
as the control and measurement structures, are an integral part
of any lateral system improvements. Therefore, the additional
benefits derived from more efficient water management cannot be
ignored.
The extent of the lateral system is approximately 600
kilometers in length and, as shown previously, contributes more
than 200,000 tons of salt to the Colorado River each year as
a result of seepage. The costs of lining these channels with
slip form concrete or buried plastic pipeline range from $10
million (Walker et al., 1977) to $30 million (USER, 1976a). The
unit salinity control costs, therefore, range from $50/ton to
$150/ton.
There exists an obvious need for rehabilitation of the
laterals, consisting of linings and regulating structures,
before an effective salinity control program can be undertaken
on the croplands. The reason is simply that there exists little
52
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means of water distribution on an equitable basis below the
canal turnout. Aside from the canal turnout themselves, which
could be rated individually, no observable or accurate means of
measurement exists internally in most laterals. Without ade-
quate control and measurement structures, it would be impossible
to either regulate lateral diversions or equitably distribute
the water among users.
ON-FARM WATER USE AND MANAGEMENT
The salinity entering receiving waters as a result of the
inefficiency in the on-farm component of an irrigation system
can be reduced but not completely eliminated. There must be at
least some flow through the crop root zone in order to remove
salts which tend to accumulate due to the concentrating effects
of evapotranspiration. Unfortunately, few if any irrigation
systems are operated in such a manner that the excess water
application just equals the required leaching fraction. The
excess leaching water generally dissolves additional salts from
the soil and aquifer materials so that the total mass emission
of salt from an irrigated area is greater than the total volume
being diverted in the irrigation water. Consequently, the more
inefficient an irrigation is, the greater the net salt pickup.
The problem is compounded by the fact that irrigation systems do
not apply water to the soil uniform by, which when combined with
the nonhomogeneity of soil characteristics, results in an
uneven distribution of the soil water in an irrigated field.
Crop yield is directly related to supplying the plant with
adequate moisture, and since the farmer wishes to maximize
yield, the least watered areas are generally given sufficient
water to meet the needs of the plant. The remainder of the
field is overirrigated, but this does not cause substantial
yield decreases even though nutrients are leached from the root
zone. Experience has demonstrated that the irrigator knows when
to irrigate, but not how much water to apply. As a result, most
irrigators apply more water even to the least watered areas than
required. And finally, water is frequently conveyed to various
field locations via a lengthy system of earthen ditches that
contribute substantial seepage losses to the underlying
groundwater basin.
If the problems of on-farm water management are properly
conceptualized, the remedies to a salinity problem evolve into
one or various combinations of three alternatives:
1) On-farm conveyance networks can be lined or
replaced to prevent seepage;
2) The uniformity of water application can be
increased by altering irrigation practices
or converting to more effective systems; and
53
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3) The irrigator can be trained or advised
regarding the amount of water required to
refill the crop root zone and meet the mini-
mal leaching requirement.
On-Farm Seepage Control
Many farmers have lined the perimeter of their farm
conveyance networks to reduce seepage, maintenance, and labor.
The most common lining methods include a concrete slip form
lining, a buried plastic membrane, compacted earth, or converting
the ditches to plastic or aluminum pipelines. Each of these
alternatives are relatively inexpensive and have become accepted
methods for improving on-farm water management. In the Grand
Valley, the on-farm conveyance system can be lined for about
$7.50 per meter, which translates into a cost of about $100 per
metric ton of salt load reduction in the Colorado River. In
order for the irrigator to operate his system effectively, flow
measurement devices should be located so that the inflow to each
field is known.
Improving Water Application Uniformity
In order to irrigate the least watered areas in a field
without overirrigating other parts of the field, the uniformity
of the application should be maximized. Since different irri-
gation systems have different uniformity problems, it is useful
to segregate this discussion into: (a) surface irrigated systems;
(b) sprinkler irrigated systems; and (c) trickle irrigation
systems.
Surface Irrigation Systems—
The predominant form of surface irrigation in Grand Valley
is furrow irrigation. The soils are relatively "tight" and
combined with the 1 to 1.5 percent field slopes results in large
volumes of field tailwater. The infiltration in these soils
generally follows a decaying exponential function. Uniformity
under furrow irrigation is maximized when the "intake opportu-
nity time" at both ends of the field are equal. Since water is
conveyed from the head end to the tail end of the field, equal
intake opportunity times along the furrow are not possible. The
least watered area of the field is at the bottom end, so under
existing management practices, the highest attainable irrigation
efficiency is achieved when the root zone in this area is just
refilled.
There are two "operational" wastes which occur under furrow
irrigation. The first, is the water percolating below the root
zone described previously. The second, only alluded to, is the
runoff from the lower end of the field. Efforts to reduce each
one is competitive; i.e., measures to minimize runoff will
54
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increase deep percolation and vice versa. Since salinity is
directly associated with deep percolation, local improvement
programs will cause high runoff if not coupled with some system
modification that will be described shortly. (In some irrigated
areas, sediment erosion is a major problem and tailwater would
be the highest priority for control.)
In the Grand Valley, furrow irrigation uniformity and
consequently efficiency can be substantially improved by three
alternatives. First, irrigation scheduling should always be
based on sampling at the lower end of the field so that the
minimal intake opportunity (or irrigation set) can be determined.
Irrigation scheduling will be discussed later in this section.
The flow in the furrow should be adjusted so that the time
required for the flow to advance to the end of the field is
about 25 percent of the minimal intake opportunity time. If
these practices were implemented and strictly adhered to, local
deep percolation volumes would be cut by more than 50 percent.
The individual furrow length and discharge can be adjusted to
satisfy these criteria. Unfortunately, such a program does not
appear realistic in the Grand Valley.
The second method for improving furrow irrigation
uniformities and efficiencies is called cut-back furrow irrigation,
Under this method, the head ditch is sufficiently automated so
that a large "wetting" furrow stream is introduced to quickly
advance the flow down the furrow and then the flow is "cut-back"
to a "soaking" flow rate to finish the irrigation. This tech-
nology has been well demonstrated in the Grand Valley with about
the same unit salinity control costs as lining the on-farm
conveyance channels. Cut-back irrigation has one notable
advantage over simply controlling the existing system—the field
tailwater is greatly reduced.
The final alternative for improving furrow irrigation
uniformities in the Valley is to utilize large furrow streams
(without causing erosion), collecting the excessive tailwater in
a small reservoir, and then pumping this water back to the head
of the field. This technology has been demonstrated on one
field in the Grand Valley by the Colorado Water Conservation
Board. Because of the low value of water in Grand Valley, there
are some difficulties in gaining farmer acceptance for this
tailwater reuse system. However, this technology represents the
most efficient furrow irrigation system when operated in terms
of a known soil moisture deficit and completely eliminates on-
farm surface wastes. The unit costs of salinity control for
reuse systems are higher than the cut-back option.
These three alternatives obviously imply that the slope of
the field is fairly uniform. If not, land grading may be
required. In the Grand Valley, with careful surface irrigation
management, the salt loading can be substantially reduced by
55
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cultural practices such as planting row crops near the edge of
a furrow (instead of midway between two furrows), so less time
is required to "soak" the seed bed by lateral wetting (especially
in the early irrigations).
Sprinkler Irrigation Systems—
A conversion from surface methods of irrigation to sprinkler
irrigation systems by farmers in the Grand Valley would be
highly beneficial in terms of efficient water use. Sprinkler
irrigation systems, properly designed, installed and operated,
have advantages both in terms of water quantity and quality.
More uniform water application is generally possible on local
types of soils, thereby minimizing deep percolation losses, and,
of course, such a system should result in no tailwater runoff.
The division of lands in the Valley are such that the most
effective sprinkler system would be the familiar mobile "side-
roll" or other portable systems. In the orchards, tow-line or
solid-set sprinklers could be used. The unit salinity control
costs should be approximately $200 per metric ton of salt load
reduction for mobile systems and $300/ton for the solid-set
systems.
Apart from the water quality benefits, there are many other
advantages to farmers in converting to sprinklers. The labor
savings are particularly noticeable in comparison with surface
irrigation methods. With portable solid-set or permanent set
systems, labor is negligible and the systems lend themselves to
automation to other water application purposes (i.e., frost
control, cooling, etc.).
Besides reducing nutrient losses as a result of reducing
deep percolation, further fertilizer loss reduction can be
achieved by the ability to use sprinkler systems to apply
fertilizers at the time required by the plant. Water soluble
fertilizers can be applied through the sprinklers with the
timing and amount controlled to meet the needs of the plant.
The ability to schedule fertilizer applications to plant needs
(rather than to cultural operations as with surface irrigation
methods) reduces the opportunity for leaching nutrients below
the root zone. The amount of water applied can also be con-
trolled to meet the needs of the crop, and thereby avoiding the
excessively large deep percolation losses that commonly occur in
the Grand Valley during the early season irrigations. Water
soluble herbicides and insecticides can also be applied through
the sprinklers.
Trickle -Irrigation Systems—
Trickle or drip irrigation is a recently developed
irrigation method and would appear to have potential for orchard
crops in the Grand Valley area. This method of irrigation has
gained attention during recent years because of the potential
for increasing yields, while decreasing water requirements and
56
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labor input. The concept behind trickle irrigation is to
provide the plant with the optimal soil moisture environment
continuously. This is accomplished by conducting water directly
to individual plants, through laterals running along each row,
instead of providing water to the entire field as with flood or
sprinkler irrigation. Another advantage is that trickle irri-
gation systems are easily automated. The multitude of lateral
lines are supplied by manifold lines connected to the main line,
which in turn, connects to the water source. A control head is
provided, generally at the water source, to regulate pressure
and flow and to filter suspended solids from the water. A
fertilizer injection system is often incorporated into the
control head.
A wetted profile, the shape of which is largely dependent
on soil characteristics, develops in the plant's root zone
beneath the" "trickle" or "emitter." Ideally, the area between
trees and between tree rows is dry and receives moisture only
from incidental rainfall. Trickle irrigation saves water
because only the plant's root zone is supplied with water and
little water should be lost to deep percolation or soil evapo-
ration under proper management. The only irrigation return flow
is due to the leaching fraction that is necessary to prevent
excessive salt buildup in the root zone. There is no surface
runoff and very little nonbeneficial consumptive use of water by
weeds. Water savings are effected through the ease with which
the correct amount of water is accurately applied. Also,
trickle requires very skilled technical assistance for nutrient
balance and fertilizer applications (the grower needs outside
technical assistance).
For irrigating widely spaced crops (i.e., trees), the cost
of a correctly designed trickle irrigation system is relatively
low in comparison to that for other solid-set or permanent
irrigation systems. In orchards, the unit salinity control cost
of a trickle irrigation system is comparable to that for a
solid-set or permanent sprinkler system having the same level of
automation. In addition, where clogging is not a problem and
emitter line maintenance is minimal, operation and maintenance
costs of the trickle irrigation system are usually quite low.
However, in plantings of row crops or vines, where the
average distance between emitter lines must be less than 3
meters (10 feet), the cost of trickle irrigation is relatively
high. When a trickle irrigation is installed, there is usually
a substantial need for technical assistance to insure that the
plants are not being stressed and that a nutrient balance is
being maintained.
Irrigation Scheduling
The results of the Grand Valley Salinity Control
Demonstration Project indicate that irrigation scheduling
57
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programs have a limited effectiveness for controlling salinity
in the Grand Valley under existing conditions. Excessive water
supplies, the necessity for rehabilitating the irrigation system
(particularly the laterals), and local resistance to change
preclude managing the amounts of water applied during successive
irrigations. To overcome these limitations, irrigation scheduling
must be accompanied by flow measurement devices at all the major
division points, farm inlets, and field tailwater exits. In
addition, it is necessary for canal companies and irrigation
districts to assume an expanded role in delivery of the water.
Also, some problems have been encountered involving poor com-
munication between the farmer and scheduler, as well as certain
deficiencies in the scheduling program dealing with evapotrans-
piration and soil moisture predictions. These latter problems
can be easily rectified, and correcting these conditions will
make irrigation scheduling much more effective and acceptable
locally.
The results of this demonstration project show that
irrigation scheduling is a necessary, but not sufficient, tool
for achieving improved irrigation efficiencies. The real
strides in reducing the salt pickup resulting from overirrigation
will come from the employment of scientific irrigation scheduling
in conjunction with improved on-farm irrigation practices. In
addition, improved agronomic practices should also be incor-
porated into an irrigation scheduling service (Jensen, 1975).
WATER REMOVAL
Drainage
Drainage investigations in the Grand Valley began shortly
after the turn of this century when local orchards began failing
due to saline high-water tables. Studies showed the soils to be
not only saline but also having low permeabilities. At the
time, the future development of the USBR's "Grand Valley Project"
loomed as a severe threat to the low lying lands between it and
the Colorado River. In answer to these drainage needs, the
solutions were clearly set forth, but never fully implemented
because of the large capital investment required. However, the
citizens of Grand Valley did elect to form a drainage district
supported by a mill tax levy in order to construct open ditch
drains and some buried tile drains to correct trouble spots.
The construction of open drains has played an important
role in Grand Valley. These drains serve as outlets for tile
drainage systems, as well as intercepting and conveying tail-
water runoff which would otherwise flow over surface lands,
infiltrate, and contribute to additional subsurface groundwater
flows, subsequently reaching the Colorado River with increased
salt pickup.
58
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Recent studies have shown that water intercepted by field
relief drainage systems has salinity concentrations about 3000
mg/1 less than if the subsurface flow continued to the river
through the groundwater system (Skogerboe et al., 1974). A
principal advantage of field drainage is that the effluent is a
point source which can be disposed of or treated. Unfortunately,
field relief drainage has unit salinity control costs more than
an order of magnitude greater than any other alternative, and
would, therefore, not be employed in any presently conceived
salinity control program. An alternative and effective form of
drainage—pump drainage—can be utilized in conjunction with
desalination to reduce salinity at about the same cost as canal
lining. This alternative is considered in more detail in the
following discussion on desalting.
DESALTING
The development of desalination technology in the United
States has been guided by the following basic objective as
stated in the Saline Water Act of 1952 (PL 448):
"to provide for the development of practicable
low-cost means for producing from sea water
or from other saline waters (brackish) and other
mineralized or chemically charged waters, water
of a quality suitable for agriculture, industrial,
municipal, and other beneficial consumptive uses."
The objective of desalination as listed above has been
given a massive research and development effort, although the
application to large-scale systems is only now beginning to
occur (USDI, USER, 1973). The traditional scope of saline
water conversion programs has been to reclaim otherwise unsuit-
able waters for specific needs. However, these programs have
dealt almost exclusively with direct utilization of product
water, rather than returning the project water to receiving
waters in order to improve the overall resource quality. Thus,
with mounting concerns for managing salinity on a regional or
basinwide scale, the potential for applying desalination within
the framework of an overall salinity control strategy is an
interesting one. A desalting system as used herein consists of
facilities for supplying raw water (water to be desalted) to the
plant, the desalting plant itself, and facilities to convey and
dispose of the brine (Figure 12). Transportation of product
water beyond the confines of this system is not considered.
Desalting Costs
In general, the costs associated with desalting systems may
be classified as either those expended during construction, or
59
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r
filtrate
and
gas
Feedwater
P retreat ment
Desalination
Subsystem
feed
Feedwater Collection
and
Conveyance
Feedwater
Subsystem
Desalting
Processes
brine
product
Product Post-
Treatment
Brine Conveyance
and
Disposal
Brine
Subsystem
•*• product water
Figure 12. Schematic diagram of a typical desalination system.
-------
those required annually to operate and maintain the facilities.
These costs are subject to inflationary pressures and must,
therefore, be periodically updated. Once costs are current,
various relationships between the costs and system performance
can be formulated. A detailed costing model is presented by
Walker (1978).
Construction costs, capital costs, or investment costs
include all expenses associated with building the appropriate
facilities and can be subdivided into the following eight
categories:
1) Construction costs, including designs and
specifications, labor, and materials;
2) Steam generation equipment if utilized in
the desalting process;
3) Site development expenses for offices, shops,
laboratories, storage rooms, etc., and for the
improvement of the surrounding landscape such
as parking, grading, and fencing;
4) Interest during construction on funds borrowed
to finance construction;
5) Start-up costs necessary to test the plant
operation, train operating personnel, and
establish operating criteria;
6) Owner's general expenses for indirect costs
like project investigation, land acquisition,
contract negotiation and administration, and
other miscellaneous overhead costs;
7) Land costs for the site and conveyance
facilities; and
8) Working capital to cover daily expenses
involved in plant operation.
Annual operation and maintenance costs can be divided
into six categories described as:
1) Labor and materials for plant or support
facility operation;
2) Chemicals for pretreatment and process
additions;
3) Fuel to power stream generation equipment;
61
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4) Electricity for pumps, filters, etc.;
5) Steam generator operation and maintenance; and
6) Replacement of process elements.
After describing the individual costs associated with
desalting systems, it is generally necessary to express such
costs in either dollars per unit volume of product water (for
water supply feasibility) or dollars per unit of salt extracted
(for salinity control studies). These cost bases are determined
by dividing the total annual costs by the annual volume of
product water or brine salts.
Applications in the Grand Valley
The desalting processes that might be applied to the Grand
Valley are as follows:
1) Multi-stage flash distillation (MSF);
2) vertical tube evaporation - mutli-stage flash
distillation (VTE-MSF);
3) Vapor compression - vertical tube evaporation
-multi-stage flash distillation (VC-VTE-MSF);
4) Electrodialysis (ED);
5) Reverse osmosis (RO); and
6) Vacuum freezing - vapor compression (VF-VC).
Associated with each of these processes must be facilities to
collect and convey feedwater and to convey and dispose of the
brines. An evaluation by Walker (1978) for the Grand Valley
indicated that local applications would most likely pump water
from the cobble aquifer underlying the irrigated area, or divert
the saline drainage and natural surface flows for the feedwater
supply. Brines would be best injected into deep strata. Based
on these criteria, Walker (1978) computed the scale distributed
desalination costs for the Grand Valley conditions. These
results are shown in Figure 13.
62
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200 r
o
••-
E
>»
•»
(A
100
i
<
"o
Figure 13.
20 40 60 80 100
Product Water Capacity, mVday x 10"*
Relationship of plant capacity and desalting costs
for various desalting systems that could be employed
in Grand Valley.
63
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SECTION 6
BEST MANAGEMENT PRACTICES
INTRODUCTION
Controlling salinity in a major river basin is a difficult
task because of the mixture of diffuse and point sources of
salinity. Generally, the best practicable solution lies in
combining the strong features of several control measures and
applying each to the conditions for which it is best suited.
Salinity control technology in this regard remains to be developed
since few investigations have managed to integrate the alter-
natives. If the control program is to be based on "best manage-
ment practices," then this integration of alternatives should be
"optimized" in accordance with a specific criteria for selecting
one measure over another.
In an irrigated area, like the Grand Valley, traditional
salinity control measures include canal and lateral linings
along with improved irrigation practices including irrigation
scheduling. Nevertheless, treatment of the agricultural system
does not completely alleviate local salinity problems because
only the salt pickup component of salinity can be reduced. By
considering other measures such as land retirement, taxation,
desalination, etc., a total salinity control program is possible
by removing salts being transported through the irrigated system,
thereby creating a "zero discharge" capability.
In the previous section, the array of alternatives for
controlling salinity were outlined and evaluated. Some were
obviously more applicable than others. Consequently, it is
necessary to delineate those which can be utilized in the Grand
Valley.
Taxation is strictly a linear application of estimated
downstream damages and, therefore, does not adequately incor-
porate the costs of treating the problem by amending local
irrigation practices. If the objective of the Grand Valley
salinity control program is to reduce salt loading by less than
300,000 metric tons per year, the taxes would be higher than the
costs to achieve the control. Plans calling for more than this
level of control would find that the taxes undercharge the costs.
In other words, there is a point where the costs of alleviating
64
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salinity are greater than the downstream damages. Taxation
would, therefore, have to be based on a sliding scale repre-
senting the minimum cost strategy for reducing salinity. These
kind of taxes, however, are simply repayment fees and are not
generated from consideration of the entire economy. Consequently,
taxation as developed earlier will not be included among the
"best management practices."
Land retirement is a viable and competitive salinity control
measure in some areas such as the extensive citrus groves near
Yuma, Arizona (where land retirement is being implemented).
These levels do not have as yet an alternative use which requires
water. In the Grand Valley, there is substantial urbanization
occurring and lands retired would sell for high prices to be
developed as housing sites. Many areas in the Valley already
converted to subdivisions utilize the water previously diverted
for agriculture. Every local indication implies these water
supplies are generally inadequate (i.e., the urban irrigator on
less vegatative area requires more water to irrigate a smaller
vegetative area because of lower water use efficiency). It
does not appear that land retirement would be a long-term
solution to the salinity problem.
All of the legal solutions and remaining economic solutions
will be omitted from this section and considered independently
in the following section when implementation is discussed.
These solutions are difficult to employ alone because they
directly or indirectly affect the kinds of physical improvements
that will be evaluated here. Since field relief drainage is so
costly, it will also be deleted from the array of alternatives.
Thus, the alternative measures for controlling local salt load-
ing can be reduced to lining or piping the canal and lateral
conveyance system, modifying existing on-farm irrigation methods
and practices, and pumping the saline groundwater or diverting
surface drain flow into desalination treatment plants.
The best management practices for salinity control in the
Grand Valley are delineated by integrating each of the alter-
natives in an optimizational context. The basis for this
analysis is the "cost-effectiveness" relationship.
COST-EFFECTIVENESS ANALYSIS
Optimization Criterion
Optimization is generally a maximization or a minimization
of concise numerical quantities reflecting the relative impor-
tance of the goals and purposes associated with alternative
decisions. Of themselves, neither the goals nor purposes
directly yield the precise quantitative statements required by
systems analysis procedures. Therefore, the objectives require
65
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a mathematical description before alternative strategies can be
evaluated (Hall and Dracup, 1970). The specific measure to faci-
litate this examination can be defined as the optimizing crite-
rion. Probably the most commonly used and widely accepted "indi-
cators" are found among the many economic objective functions.
However, considerable controversy exists as to the most realistic
of these tools. If, for example, aspects of a water quality
problem could be priced in an idealized free market monetary ex-
change, the forces that operated would insure that every indivi-
dual's marginal costs equalled his marginal gains, thereby
insuring maximum economic efficiency. In the absence of this
ideal situation, the optimizing criterion, in any case, is at
best an indicator of the particular alternative.
Among the more adaptable economic indicators are
maximization of net benefits, minimum costs, maintaining the
economy, and economic development. The use of each depends on
the ability to adequately define tangible and intangible direct
or indirect costs and benefits. In water resource development,
and water quality management specifically, the economic incentives
for more effective resource utilization are negative in nature
(Kneese, 1964). A large part of this problem steins from the
fact that water pollution is a cost passed on by the polluter to
the downstream user. Consequently, the inability of the existing
economic systems to adequately value costs and benefits has
resulted in the establishment of water quality standards, however
inefficient these may be economically (Hall and Dracup, 1970).
The immediate objective of water resource planners is thus to
devise and analyze the alternatives for achieving these quality
restrictions at minimum cost, the criteria chosen for this study.
The reader interested in the nature of the optimization
technique utilized in the analysis of minimum cost is referred
to Walker (1978).
Conceptual Minimum Cost Salinity Control Model
On a basinwide scale, a salinity problem is the combined
effect of many irrigated areas, saline springs, diffuse natural
inflows, and other miscellaneous sources. These salinity sources
not only occur sequentially due to the geographic structure of
hydrologic area, but are also often governed by differing
administrative formulas. Consequently, the problem of deter-
mining an "optimal" strategy for a major river basin area
rapidly becomes too large and too complex for direct analysis.
One of the various mathematical techniques for optimizing com-
plicated systems is to decompose the problem into a series of
aubproblems whose solutions are coordinated in a manner that
produces the solution to the larger problem. One method applied
to analysis of water quality improvements in the Utah Lake
Drainage basin of central Utah provides both a simple and
effective decomposition (Walker et al., 1973). The structure of
the decomposition methodology referred to above is shown
66
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schematically in Figure 14. Individual levels of modeling are
delineated to define water quality cost-effectiveness analyses
at different stages of development enroute to a single repre-
sentation at the ultimate basinwide scale.
The conceptual model illustrated in Figure 14 represents an
additive approach for determining the minimal cost salinity con-
trol strategy in a river basin. A number of levels or subdivi-
sions having similar characteristics can be defined to correspond
to various levels of hydrologic or administrative boundaries in
a region. Within each level, the alternative measures for
salinity management are characterized by cost-effectiveness
relationships. A more detailed review of the structure of cost-
effectiveness functions and their interdependence will assist
the reader in understanding the application of the conceptual
model in later sections.
Description of Cost-Effectiveness Functions—
The alternatives for managing salinity on a basinwide scale
fall into two categories: (a) those that reduce salinity con-
centrations by dilution or minimizing the loss of pure water
from the system by evaporation; and (b) those that improve water
quality by reducing the mass emission of salt.
Examples of the first category include weather modification
to enhance stream flow, evaporation suppression, and phreato-
phyte control. Many of these approaches are more costly and
difficult to apply than is justified by the salinity control
achieved and are, therefore, not considered in this work. In
the second category, such measures as saline flow collection and
treatment, reduction in agricultural return flows, and land use
regulation can be used to reduce the volume of salinity entering
receiving waters. In this report, only saline flow collection
and treatment and irrigation return flow management are
evaluated. Under these assumptions, salinity control becomes
a mutually exclusive problem that allows addition of individual
solutions to derive larger solutions. By letting the spatial
scale of the problem correspond to successive layering or addi-
tions, the multilevel approach is congruent to the subbasin
breakdown of major hydrologic areas.
The smallest spatial scale considered in this analysis is
that of a subbasin containing an irrigated valley or stream seg-
ment delineated by inflow-outflow data. In a major river basin,
a number of river systems may combine to form the basin itself
so there are actually a number of subdivisions in a river basin.
Thus, vertical integration of subbasins yields the aggregate
river basin. In this analysis the river basin, river subsystem,
and subbasin divisions have been designated as levels 4, 3, and
2, respectively. Level 1 will also encompass the subbasin scale
as will be described shortly.
67
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Cost
Cost of achieving desired
salinity control at
level 4
LEVEL 4 SALINITY CONTROL
COST-EFFECTIVENESS FUNCTION
: Optimal investment in
ternative 2 at level 3
—4-
; Optimal investment in
alternative I at level 3
Effectiveness
cn
oo
Cost
Optimal level 3
Costs from level 4
ALTERNATIVE I, LEVEL 3
COST-EFFCTIVENESS
FUNCTION
L I, level 2 investments
alt. 2, level 2 investments
Effectiveness
Cost
ALTERNATIVE 1. LEVEL 2
COST-EFFECTIVENESS
FUNCTION
Cost
/Jevel I
' Cl
costs
ALTERNATIVE 2 LEVEL2
COST-EFFECTIVENESS
FUNCTION
Desired salinity control
at level 4
level I
/ costs
J-"
Optimal level 2
Cost from level 3
Effectiveness
Optimal level 2
Cost from level 3
Effectiveness
Cost
/ALTERNATIVE 2.
/ LEVEL 3 COST-
' EFFECTIVENESS
FUNCTION
Effectiveness
Cost
ALTERNATIVE 3 LEVEL 2
COST-EFFECTIVENESS^.
FUNCTION
Cost
level I
costs
ALTERNATIVE 4 LEVEL}
COST-EFFECTIVENESS
FUNCTION
level I costs
Effectiveness
Effectiveness
Figure 14. Conceptual decomposition model of a regional or basin salinity control
strategy (Walker et al., 1977).
-------
Associated with each level of the model are cost-
effectiveness functions describing each alternative for con-
trolling salinity. The structure of the cost-effectiveness
functions includes two parts. The first is the function itself.
In order to compare the respective feasibility among various
salinity control measures at each level, the mathematical de-
scription of each alternative must be in the same format. Since
this study involves evaluating the minimal cost strategy for
reducing salt loading, each salinity control measure's feasibi-
lity for being included in the eventual strategy is based on the
relationship between the costs of improvement and the resulting
reduction in salt loading. The second part of the cost-
effectiveness functions is what might be called a "policy space."
To appreciate this aspect of the model, it is probably necessary
to first discuss the determination of the optimal basinwide
strategy.
Evaluating the Optimal Strategy—
Suppose the optimal policy for controlling salinity in a
river basin had been determined with a minimum cost decision
criterion. Such an analysis would provide two pieces of infor-
mation. First, it would detail the cost associated with a range
of reductions in salinity, and second it would delineate how
much of these costs are to be expended in each river subsystem.
In other words, the evaluation of the optimal strategy at level
4 involves systematic comparisons of level 3 cost-effectiveness
functions and once the strategy had been determined, it also
yields the optimal costs or expenditures in each level 3 alter-
native (river subsystem). In a similar vein, the level 2 costs
and policies are determined from a knowledge of the level 3
optimal as determined during the level 4 analysis and so on.
Thus, the cost-effectiveness function for any alternative within
a level is:
1) The result of optimization of respective cost-
effectiveness functions at a lower level and
therefore a minimum cost relationship at every
point; and
2) The sum of costs from optimal investments into
each alternative at a lower level. The "policy
space" is therefore a delineation of lower level
cost-effectiveness functions.
The preceding paragraphs noted the detailing of a salinity
control strategy once the optimal is known. Determining the
basin optimal, on the other hand, begins at a level 1. A com-
parison of level 1 cost-effectiveness functions describing each
alternative at that level produces the array of level 2 func-
tions. Similar steps yield each succeeding level's optimal
program. Thus, the multilevel approach described herein involves
69
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a vertical integration up through the levels to determine the
optimal policy and a backwards trace to delineate its components.
MODEL APPLICATION IN THE GRAND VALLEY
The array of salinity control alternatives applicable as
first level measures in the Grand Valley were described earlier
in four primary classes: (a) on-farm structural and operational
improvements; (b) lateral lining by slip form concrete or plastic
pipeline; (c) concrete canal linings; and (d) collection and
desalination of subsurface and surface drainage return flows.
On-Farm Improvements
On-farm water management improvements which improve
irrigation efficiency and thereby reduce return flows include:
(a) improved irrigation practices implemented through irrigation
scheduling; (b) structural rehabilitation; and (c) conversion
to more efficient methods of irrigation.
Irrigation Scheduling—
Recent studies in Grand Valley have indicated that
irrigation scheduling services, even when accompanied by flow
measurement structures, generally do not significantly improve
farm and application efficiencies (Skogerboe et al., 1974a).
The overall impact of irrigation scheduling is estimated at
only 10 percent of the total estimated on-farm potential improve-
ment, which is insignificant by itself when considering the
sensitivity of these types of costina estimates. Consequently,
irrigation scheduling should be considered part of other irri-
gation improvement measures rather than considered a separate
alternative salinity control measure.
Structural Rehabilitation—
Structural improvements in the system may include concrete
lined head ditches or gated pipe to reduce on-farm seepage
losses, land leveling for better water application uniformity,
adjusting field lengths and water application rates to be more
congruent with soil and cropping conditions, and automation to
provide better control. Flow measurement and scheduling ser-
vices should accompany these types of improvements in order to
maximize their effectiveness.
In the Grand Valley, head ditch requirements are generally
less than the capacity of the smallest standard ditch available
through local contractors (12 inch bottom width, 1:1 side slope,
slip form concrete). Assuming an average head ditch capacity
of 0.05 mvsec, the estimated unit cost of head ditch linings
is $7.50/m (Walker, 1978). This figure is well within the range
encountered in the last two seasons in the Valley. There are
70
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approximately 1.3 million meters of head ditches in the Grand
Valley contributing an estimated 95,000 metric tons of salt to
the river annually. If linings were assumed to be 90 percent
effective, the cost-effectiveness of head ditch improvements
would be $113.40/ton (1.3 million meters x $7.50/m 7 86,000
tons).
Automatic cut-back furrow irrigation systems have
demonstrated which, when combined with irrigation scheduling,
may improve application efficiencies to 75 or 80 percent,
thereby effecting an additional 60,000 ton decreases beyond the
effects of the linings (Evans, 1977). In 1975, the installed
cost of the cut-back systems was $11.50/m. Thus, the salt load
reductions by lining head ditches (86,000 tons) and the addi-
tional 60,000 m ton reduction resulting from increased appli-
cation efficiency results in a cost-effectiveness of $102.407
ton. Because of the small size of these ditches, linear distri-
bution can be assumed without introducing significant error. In
the case of the Grand Valley, it appears automation may be added
to surface irrigation systems for the additional water use effi-
ciency and consequent salt load reduction at about the same
cost-effectiveness as the simple head ditch or gated-pipe
improvements. Where head ditch capacities are large, concrete
lining would generally be more cost-effective than piped systems.
Automated cut-back furrow irrigation would further reduce salt
loading due to improved irrigation efficiencies.
Field lengths may be modified along with land shaping to
improve the uniformity of water applications. This would be
particularly true in soils having a relatively high infiltration
capacity, but not as effective in tight soils such as those
encountered in the Grand Valley.
In order to completely control irrigation return flows, the
method of applying irrigation water needs to be independent of
soil properties. The application of sprinkler irrigation
systems was shown by Walker (1978) to be approximately 80 per-
cent efficient (application efficiency), whereas trickle irriga-
tion systems could be expected to operate at the 90 percent
level. Applying either system to the average field size in the
Grand Valley (2-3 hectares) would be very expensive, so most
systems would irrigate multiple fields. Mobile sprinkler
systems would cost about $900 per hectare for coverages larger
than 10 hectares. Trickle irrigation systems would cost
approximately $1,800 per hectare for sizes greater than 2
hectares. Assuming irrigators would consolidate fields suffi-
ciently to avoid the high unit costs encountered with small
fields, the salt loading reduction for each system can be cal-
culated as about 7 tons/hectare for sprinklers and about 9 tons/
hectare for sprinklers and about 9 tons/hectare for trickle
systems. These figures also take into account elimination of
field head ditches and tailwater ditches. Mobile or portable
71
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sprinkler systems would have average salinity cost-effectiveness
ratios of approximately $132/ton, while the respective range for
trickle systems would be about $200/ton. Solid-set sprinklers
would be at least double these figures and are therefore not
evaluated. Center-pivot systems would be difficult to apply in
the Grand Valley because of the small average size of land
holdings.
Optimal On-Farm Improvement Strategies—
The first level cost-effectiveness function for on-farm
salinity control is developed by computing the minimum cost
strategy at various levels of on-farm control. These results
for the Grand Valley case are shown in Figure 15.
The actual computed cost-effectiveness relationship for
on-farm improvements is the step function shown as the solid
lines. This characteristic occurs because of the linear
assumption regarding the distribution of costs and salinity
impacts. The smooth curved line represents a best fit through
the cost-effectiveness distributions.
Two major strategies evolved in the analysis of on-farm
improvements: (a) improvements to the existing system creating
salinity reductions up to about 150,000 tons annually; and (2)
system conversions to provide controls up to approximately
220,000 tons annually. Irrigation scheduling should be incor-
porated with all alternatives. Of particular interest here is
the fact that the alternatives are mutually exclusive. In
other words, in implementing an on-farm salinity management
plan, either one or another is optimally chosen. For instance,
if planners selected on-farm improvements to reduce salinity by
more than 150,000 tons, the alternatives would be limited to
changing to sprinkler or drip irrigation methods. Below the
150,000 ton figure, head ditch lining and/or automation would be
optimal. This structure of the cost-effectiveness is unique
among the alternatives as the reader will note in succeeding
sections. This uniqueness is based on the fact that on-farm
improvements themselves are mutually exclusive and limited in
their expected effectiveness.
Lateral Lining and Piping
Laterals have been defined as the small capacity conveyance
channels transmitting irrigation water from the supply canals
and ditches to the individual fields. Most of these laterals
operate in a north-south direction and can carry the flows in
relatively small cross-sections. Although the capacities of the
laterals may vary between 0.06 and 1.4 mVsec, most capacities
would be within the range of 0.06 to 0.20 mVsec. Utilizing a
median value of 0.20 m^/aec yields a concrete lining cost of
approximately $16/m. Alternative use of PVC pipe approximates
72
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so r
o
O
O.
O
O
o
S
Figure 15
40
30
20
10
Sprinkler
Irrigation
a
Irrigation
Scheduling
Trickle
;/ Irrigation
a
.- Irrigation
'-Scheduling
Head
^ Ditch Linings
a
Irrigation Scheduling
KX>
20O
Salinity Reduction, thousands of metric tons
Cost-effectiveness function for the first level,
on-farm improvement alternatives in the Grand
Valley.
73
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concrete lining costs for this capacity and a further distinction
will not be made.
As noted earlier, Grand Valley laterals extend approximately
600,000 meters, less than one-half the length of field head
ditches. Seepage under existing conditions contributes about
202,000 metric tons, or slightly less than the on-farm contri-
bution. Although no attempt is made to distribute the lateral
lining costs to account for variable capacity, the cost-
effectiveness function for Grand Valley lateral lining is about
$50 per metric ton. Thus, the estimated costs of lining the
total lateral system in the Valley is about $10 million. It
should be noted that in personal contact with the USBR, (1976a),
costs for the lateral linings were estimated to be more than $30
million in 1976.
Canal and Ditch Lining
There are 14 major canal and ditch systems in the Grand
Valley ranging in length from 74 kilometers for the Government
Highline Canal (17 mVsec capacity) to 4 kilometers for the Mesa
County Ditch (1 mVsec capacity). The pertinent parameters for
each canal, along with the seepage contribution to salt loading,
were given earlier. The results of an optimal canal lining pro-
gram are given in Figure 16, which shows the total capital con-
struction costs as a function of the annual salt load reduction
to be realized (Walker, 1978).
The results obtained in optimizing canal lining policies
are interesting in the sense that they demonstrate the need to
initiate linings on more than one segment of the conveyance
system when full-scale implementation begins. This may not be
practical from a planning or scheduling standpoint.
Desalination
Desalting evaluations involved first determining the most
cost-effective process and, second, the most cost-effective
feedwater and brine disposal facilities. The optimal desalting
policy in the Valley utilizes a reverse osmosis system with
feedwater wells and brine injection wells (Walker, 1978) . To
express desalting cost-effectiveness in the same format as the
agricultural alternatives, the costs are plotted against the
mass of salts removed from the system. For the purposes of this
report, an interest rate of 7 percent and a usable life of 30
years will be assumed. For the reverse osmosis system, Figure
17 shows the resulting cost-effectiveness function.
Whereas agricultural salinity control costs exhibit
increasing marginal costs with scale, the opposite is true for
desalting systems. In an optimizational analysis, therefore,
the respective feasibility of desalting technology is maximized
for large-scale applications. For small systems, desalting is
74
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9 ~ Redlonds System
Redlands System
rrrv**ffj
Government /.
Grand Valley
Grand Volley Mainline
Grand Valley Highline
'// overnment ighlne anal
Y////////X//////////,
40 50 60 70 80 9O 100 110
Annual Salt Load Reduction, thousands of metric tons
Figure 16.
Optimal Grand Valley canal lining cost-effectiveness
function (Walker et al., 1977).
75
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100 200 300
Annuol Salt Removal, thousands of metric tons
Figure 17. Grand Valley desalination cost-effectiveness
function (Walker et al., 1978).
76
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much less cost-effective than treatment of the agricultural
system. As these factors are considered, a linear approximation
representing the average marginal cost would serve at least as
well as the nonlinear function. Consequently, desalting cost-
effectiveness in the Grand Valley can be represented by using a
present value cost of $320 per metric ton of salt reduction
(Walker, 1978).
BEST MANAGEMENT PRACTICES
The individual cost-effectiveness functions at the first
level (desalting, canal lining, lateral lining, and on-farm
improvements) are optimally integrated to determine the minimum
cost salinity control strategy for the Grand Valley. These
results are shown in Figure 18.
Consider three points on the Grand Valley cost-effectiveness
curve (Figure 18): (a) total costs = $15 million, salt loading
reduction = 266,000 tons; (b) total costs = $40 million, salt
loading reduction = 403,000 tons; and (c) total costs = $80
million, salt loading reduction = 530,000 tons. For convenience,
these three points have been designated as Cases 1, 2, and 3,
respectively.
If the expenditure in the Grand Valley is to be $15 million
in 1976 value dollars (Case 1), the optimal strategy in so doing
is found from a vertical trace at this point on the curve repre-
senting the Valley (Figure 18). Specifically, $10 million should
be invested in lateral linings and $5 million in on-farm
improvements. Referring back to the paragraphs on lateral
lining, it is noted that a $10 million investment covers the
cost of lining the entire system. Thus, for Case 1, the first
part of the strategy is to line the lateral system entirely. In
a similar backward look to Figure 15 representing the level 1
relationship for on-farm improvements, it is seen that a $5
million cost corresponds to about 64,000 ton reduction in the
on-farm salinity contribution, and is so accomplished by head
ditch linings, or cut-back irrigation, and irrigation scheduling.
A $40 million salinity control investment (Case 2) in the
Grand Valley is seen from Figure 18 to reduce salinity by
403,000 metric tons by spending $10 million lining the lateral
system, $20 million making on-farm improvements and $10 million
for lining some of the major canals. Referring again to Figure
15, a $20 million investment in on-farm improvements implies
reducing the on-farm salt contribution by 156,000 tons by
irrigating nearly all of the irrigated land with portable or
mobile sprinkler systems. Figure 16 showed that $10 million
in canal lining would accomplish a 45,000 ton reduction in salt
loading. To do this, a small (essentially insignificant) amount
77
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On-Farm Improvements
IOO 200 3OO 4OO 500 600
Annual Salt Loading Reduction, thousands of metric tons
700
Figure 18. Grand Valley second level salinity control cost-
effectiveness function.
78
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of lining should occur in the Redlands system with the remainder
being applied to the Government Highline Canal.
Case 3 shows that agricultural improvements should stop at
$42.6 million, with any remaining salt volumes to be removed
from the system through desalination of the subsurface irrigation
return flows. The $42.6 million figure for local agriculture
includes $10 for lateral lining, $21 million for on-farm improve-
ments, and $11.6 million in canal lining. On-farm improvements
would still involve conversion to sprinkler irrigation in
conjunction with irrigation scheduling.
The mathematics of this analysis indicates the minimum cost
salinity control strategy for the Grand Valley, but a planner or
administrator must also consider the practicality of the solu-
tions. For example, in the third case, it would probably be
unrealistic to line a very small portion of the Redlands Canal
system; consequently, a decision would likely be made to invest
all of the funds into lining the required length of the
Government Highline Canal. Likewise, on-farm improvements may
be limited to converting the existing system to a sprinkler
irrigated system with some measure of control to increase appli-
cation efficiencies beyond those assumed for this analysis. The
point to be made is that at this level of investigation, the
inherent assumptions allow a certain amount of flexibility to
account for some of the intangible social-institutional factors
involved in an implementation effort.
In representing what might be called the best management
practices for the Grand Valley, it must be realized that the
four major implementation alternatives (lateral lining, on-farm
improvements, canal linings, and desalting) only represent
"structural measures." Consequently, nonstructural alternatives
such as land retirement, influent and effluent standards, taxa-
tion, and miscellaneous enforcement options are not included.
Nevertheless, the value of this sort of analysis can be clearly
demonstrated. In the Grand Valley, a plan might be proposed in
which all of the canals would be lined, all of the laterals
lined, and some on-farm improvements to reduce salt loading by
450,000 metric tons annually. Looking at Figure 15 and 16, and
the comments describing lateral linings, shows a total cost of
such a program of $65.5 million. Figure 18 indicates the same
reduction could be accomplished with a $54 million investment
if the on-farm role were expanded, the canal lining program
diminished and a limited desalting capacity were included. Thus,
this optimization analysis illustrates how a $11.5 million
savings (21 percent) can be achieved.
The eventual program in the Grand Valley is dictated by its
respective feasibility in comparison to similar cost-effectiveness
studies on the other subbasins in the Upper Colorado River Basin.
In fact, the level of investment in the entire river system for
79
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salinity control depends on the level of damages created by the
salinity. Since the completed four level analysis is not avail-
able, it is interesting to compare downstream damage with costs
in the Grand Valley. Note that the estimates of marginal cost
and downstream detriments must be the same. Walker (1975)
reviewed much of the literature descriptive of the California,
Arizona, and Republic of Mexico damages. At the time, Valentine
(1974) had proposed damages of $175,000 per mg/fc of increase at
Imperial Dam ($146 per ton in Grand Valley assuming 8 percent
interest). Other estimates in terms of equivalent damages
attributable to Grand Valley range upward. A representative
figure is $190/ton as proposed by the USER (Leathers and Young,
1976). Some as yet unpublished figures now place these damage
figures as high as $375/ton. If the minimum cost curve in Figure
18 is differentiated to approximate marginal costs and be con-
gruent with these damage figures, the $146 per ton damage esti-
mate of Valentine (1974) falls at a 300,000 ton reduction, while
the $190 per ton and $375/ ton figures occur at 355,000 tons and
538,000 tons, respectively. Figure 19 is a plot of the marginal
Grand Valley salinity costs as a function of salt loading
reduction. Thus, not considering secondary benefits in the
Valley, or obviously all the consequences in the lower basin,
the level of investment in the Grand Valley could range between
$19 million for $83 million. In any event, it can be seen that
the actual policy for salinity control in a subbasin depends on
decisions made at higher levels. Similarly, within a subbasin
the measures implemented to control salinity change as the
emphasis on the subbasin itself changes.
Sensitivity of Results
In earlier sections of this report, two major discrepancies
with other investigative or planning groups were noted. The
first was the difference between the salt contributed by canal
seepaoe and that contributed by on-farm sources. The second
difference was that the authors' lateral lining cost estimate
was about one-third of the estimate made by the USER (Walker
et al., 1977). In order to evaluate these differences on the
Valley's best management practices, the optimizational analysis
was adjusted to account for the first differences and then the
combined effect of both differences. The results are shown in
Figures 20 and 21.
In the first case, optimal on-farm investments have been
reduced by more than 13 percent while the expenditures in canal
lining have more than doubled. The second case indicates that
the higher priced lateral lining emerges in about the center of
the on-farm and canal lining policies. In addition, the costs
of the program are substantially increased for all levels of
possible salt loading reductions. The best management practices
for salinity control in the Grand Valley follow about the
80
-------
300
o
o
200
o
o
(O
100
100 200 300 400 500 600
Annual Salt Loading Reduction, thousands of tons
700
Figure 19.
Marginal cost function of optimal salinity control
strategy in the Grand Valley.
81
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140
120
IOO
o
T»
C
O
80
o
u
40
o
o
20
Ofl-form Improvements
0 IOO 200 300 40O 50O 600
Annuol Solt Lcoding Reduction, thousonds of tons
Figure 20. Grand Valley best manaqement practices based on the
hydro-salinity system proposed by Kruse (1977).
82
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I40r
Conol Lining
On-form Improyamant*
Lotarol Lining
Canal Lining
\\x\\\\\\
ssss/SSS/SS // S / s . / ,• / / / ,' / /
On-farm Improv*mant• ////
100 200 3OO 400 500 600
Annual Salt Loading Reduction, thousands of tons
Figure 21. Best Management practices for the Grand Valley
assuming the hydro-salinity budget for Kruse (1977)
and a threefold increase in lateral lining costs.
83
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same course of events irrespective of the hydro-salinity numbers
utilized. If the lateral lining costs, however, are increased
by utilizing more expensive pipe, the overall effect will be
significant.
It should be noted in closing this part of Section 6, that
the USBR has updated the estimated canal lining and lateral
lining costs (USBR, 1977). Figures presented in this report are
based on early 1976 estimates and can be updated if desired.
However, even correcting for the effects of inflation does not
reconcile the difference, because the writers have used different
construction materials to control salinity than has the USBR in
their estimates. For example, there is no reason to utilize
concrete or high-head PVC pipelines in the Grand Valley lateral
lining programs (as now planned) when properly installed low-
head PVC or slip form concrete will perform as well. The properly
installed low-head PVC or slip form best management practices
are, of course, affected by decisions to use more expensive
lining materials where unnecessary. In fact, use of concrete
pipe for laterals causes this salinity control alternative to be
substantially less cost-effective than most potential on-farm
improvements.
IMPACT IN THE COLORADO RIVER BASIN
In Section 4, the hydro-salinity system of the Grand Valley
was described in terms of the 1968 water year which is thought
to be representative of the average condition. More exhaustive
review of the USGS water sampling data shows some disparity with
the figures utilized herein, but the differences are unimportant
for the points to be discussed in the following paragraphs. The
writers estimate that the prevention or removal of one metric
ton of salt from the Colorado River will improve the water
quality leaving the State by 2.17 x I0~k mg/l. Thus, a 400,000
metric ton salinity program in the Grand Valley could be expected
to improve the quality of flows leaving the State in the Colorado
River by approximately 87 mg/l. The Bureau of Reclamation com-
putes a 1976 modified condition at Imperial Dam in which a one
metric ton reduction in salt loading will reduce salinity con-
centrations by 1.16 x 10~" mg/l (USBR, 1977). Again, a 400,000
ton reduction in the Grand Valley would improve water quality
at Imperial Dam by more than 46 mg/4.
At the time of this writing, existing plans call for a
salinity control program of about 400,000 metric tons annually
in the Grand Valley. Long-term monitoring of the river outflows
will establish the exact magnitude of the salinity reduction.
However, the vital issue is the maintenance of the 1972 salinity
levels at Imperial Dam (800 mg/fc)/ a policy which has been
generally accepted as the long-range goal. The USBR estimates
that development of the remaining Colorado River entitlements
84
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would increase salinity concentrations at Imperial Dam by 300 to
400 mg/A. Consequently, the Grand Valley salinity control pro-
gram can be expected to eliminate about 10 percent of the problem
which will require attention by the year 2000. In fact, if all
of the problem is to be amended such that the 1972 water quality
goal is protected, combined reduction in salt loading and evap-
orative concentration must equal an equivalent 3 million ton
salinity control effort. Thus, many irrigated areas must be
included in the eventual program as well as the improvement of
other factors contributing to salinity in the Basin.
85
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SECTION 7
ECONOMIC AND LEGAL OPTIONS
The development of best management practices in the previous
section provides for the most cost-effective salinity control
program in Grand Valley utilizing technologies that are not only
appropriate, but they have also been demonstrated on farmers'
fields to evaluate their acceptability to fanners. The imple-
mentation of these cost-effective and acceptable technologies
requires some consideration of the economic and legal options.
A combination of physical improvements and institutional
rearrangements are most likely to provide the most implementable
salinity control program. The three options to be discussed
below are land retirement, taxation, and development of a water
market. Other considerations involved in implementation will be
discussed in Section 8.
LAND RETIREMENT
Much of the research effort by physical scientists concerned
with controlling rising levels of salinity in the Colorado River
Basin has focused on structural technologies. These means
typically require extensive technical and material input often
leading to substantial public and orivate investments. Land
retirement is one nonstructural control option that deserved
careful study since acreage reduction or desalination are the
only technically feasible methods which can be employed to
achieve the zero discharge objective proposed in the 1972 federal
water quality legislation (Public Law 92-500).
To determine whether land retirement can be feasible on
economic efficiency grounds, two sources of information are
required: (a) the direct and indirect costs of removing land
from irrigation; and (b) the benefits or incremental reduction
in damages that would occur as a consequence. Direct costs
should accurately reflect the incomes foregone from farming of
the retired irrigated lands. Included in the indirect costs
should be the net effects of costs and benefits issuing from
resource reallocation, social transition, impacts on environ-
mental amenities, and other consequences in the affected region.
An interindustry (inout-output) model serves as the
underlying structure for the analysis reported by Leathers and
86
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Young (1976). The input-output model is an analytical accounting
technique commonly used in the evaluation of "total" economic
impacts of exogenous (or outside-induced) changes in an economy.
Because of the interdependence among industries in a well
developed economy (which may include small or large regions),
secondary (or indirect) impacts are often thought to be just as
important as the primary (or direct) impacts of an induced
change. For this reason, the basic approach adopted in the
study by Leathers and Young (1976) is an indirect impact
analysis.
Land retirement mechanisms might include one or more of a
number of options and can be either voluntary or involuntary
depending on the level of public acceptance and participation in
the program. The objective is to discontinue irrigation of
selected acreages, thus eliminating all future salt loading from
these sources. Specific program options evaluated by Leathers
and Young (1976) involve a permanent withdrawal of water
supplies.
Withholding irrigation water from previously cultivated
acreage in the Grand Valley might be accomplished on a voluntary
basis by State purchase of existing water rights from willing
sellers. Because of the Grand Valley's arid climate, this would
mean that farmland is taken out of production altogether,
eventually returning to desert. State purchase of privately-
held water rights through legal condemnation proceedings would
constitute a compulsory mechanism. Both would, in effect,
amount to land purchase since desert grazing land is of nominal
value by comparison.
If a voluntary land retirement program is to be viable,
this implies that some farmers in the Valley would be willing,
to sell their farms (or a portion of their acreage) at a price
that exceeds the present value of their long-run, capitalized
earnings. In the case of "marginal" farms, this would mean that
some individuals would be willing to trade the present value of
farming (in the long run) as a "consumption activity" for an
alternative activity made available by the purchase offer. (If
the land were subdivided into suburban homes, then there would
be a high likelihood that lawn irrigation would contribute sub-
stantially to the salt load reaching the Colorado River). Under
an involuntary program, it would probably be necessary that the
offer price exceed the present market value of representative
irrigated acreages. The program would have an added flexibility
if willing sellers under a voluntary retirement scheme could
select the marginal acreages on their farms (perhaps difficult
areas to irrigate where water losses are high and productivity
low) for purchase by the State—analogous to the soil bank
program (Public Law 89-321). Under such an option, the costs of
the program might be reduced appreciably.
87
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Two different options were examined by Leathers and Young
(1976). Option I represents a partial retirement scheme.
Specific areas of irrigated land which are markedly less pro-
ductive (since they tend to have high salt content and/or serious
natural drainage problems that hinder plant growth) are selected
for retirement. Leathers and Young (1976) have stated that
approximately 3,500 hectares in the Grand Valley fall into this
category. Together they represent 14 percent of the area's
irrigated l?nds and 8 percent of the areas' crop output. Since
these areas of relatively unproductive soils are not contiguous
in large blocks, retirement of such lands would control deep
percolation from fields and seepage from farm head ditches, but
would not reduce seepage losses in the main conveyance system.
A different strategy (Option II) considers the effect of
retiring an entire irrigation district. All canals and laterals
controlled as an integrated unit and the acreage (both poor and
productive) they service would be withdrawn from production.
With this option, land retirement implies the inclusion of canal
and lateral seepage losses, which would not be the case under
the first option. Accordingly, the costs of retirement are
compiled by Leathers and Young (1976) on the basis of two
assumed rates of annual salt reduction per acre: 4.9 metric tons
under Option I, and 7.4 tons under Option II. The Government
Highline Canal was chosen to illustrate the impacts of Option II,
which is assumed representative of the Valley as a whole in
terms of both productivity and salt pickup, so that results could
be generalized to a full land retirement program (Leathers and
Young, 1976).
A summary of results presented by Leathers and Young (1976)
for the two options is shown in Table 10. In order to present
these data in the same units as used throughout this report, the
figures are expressed as the dollars per metric ton reduction
recovered to the present time of early 1976. The interest rate
is assumed to be 8 percent and the period 30 years.
In general, the incremental costs of salt removal (in $ per
metric ton), using the provisional estimates of salt pickup,
appear to be competitive with other more expensive controls such
as canal lining, drainage, and desalting. However, the cost-
effectiveness of the program is quite sensitive to assumptions
regarding estimates of the quantity salts removed and the value
of the salts removed. Accordingly, it is important that these
assumptions be considered very carefully in comparing alternative
salinity control programs. For example, the cost of partial
retirement (Option I lands) varies from $76.50 per ton to
$177.80 per ton depending on the assumed rate of salt pickup per
acre, and more than double if the regional economic impact is
viewed. Leathers and Young (1976) believe that the regional
accountina stance provides a fairly generous upper bound on
total program costs.
88
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TABLE 10. COST-EFFECTIVENESS OF SELECTED LAND RETIREMENT
OPTIONS (LEATHERS AND YOUNG, 1976)
Salts Removed
(m ton/ha) Dollars per m ton
Lower Bound Upper Bound
Partial Land Retirement
(Option I)
2.7 177.80 500.70
4.9 99.00 277.90
6.4 76.50 214.90
Complete Land Retirement
(Option II)
4.5
7.4
10.0
245.30
149.60
111.39
586.20
356.70
266.70
TAXATION
Experience has proven that uncontrolled use of many natural
resources cannot be maintained, particularly the assimilative
capacity of air and water. These resources have often been
overloaded with a vast array of pollutants threatening the health
of both human and biotic environments.
Much of today's problem can be understood by examining the
historical perspective with which natural resources were
developed and utilized. Initially, the supply exceeds the
demands, and it is economically "free," but, with development,
such resources became "scarce" in the sense that competitive
pressure is put on the limited supply provided by nature. At
the point where the scarcity develops, neither the private
market nor the public structures for regulation are capable of
equitable allocation. Negative externalities begin to mount, and
the various environmental systems may be severely damaged. As a
result, this country has incorporated public regulation in the
form of quality standards to manage pollution. The remaining
alternatives for controlling pollution; namely, subsidy, moral
suasion, and taxation, have been overlooked because of the
necessity for immediate action.
Economists such as Solow (1971) and Baumol (1972) have
argued that standards are emergency measures and neglect the
questions of benefits and costs on a regional scope. A much
better solution is suggested in which effluent taxation would be
imposed on polluters, who would then determine whether to clean
their wastes or pay the taxes so such treatment could be provided.
89
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The lower the marginal cost of pollution control from a source,
the larger the reductions which can be achieved to avoid the
corresponding tax payment.
Walker (1978) evaluated the taxation alternative for the
Grand Valley. An updated summary of this work is included in
the following discussion.
Grand Valley Economy
Sectors within the general economy are not isolated from
each other, even though a considerable degree of specialization
may be present. Thus, an analysis which focuses entirely upon a
single sector, or even a limited number within the economy, can
only effectively examine the behavior and problems internal to
that specific sector. In the study by Walker (1975), the inter-
nal workings of the Grand Valley economy were not of primary
concern, but rather, the linkage between the agricultural
sectors and the rest of the local economy. This linkage describes
the local impact either directly or indirectly that would result
from taxing individual cropped acreages to effect a specified
measure of salinity control. The basic analytical system used
herein to achieve a description of the linkages is the "input-
output" model described by Miernyk (1965).
The economic input-output model results in a business
multiplier for each industry in the processing sector (which in
this case is irrigated agriculture). The value represented by
the business multiplier indicates the total economic production
in the economy of the Grand Valley resulting from one dollar
worth of output from an industry in the irrigated system (i.e.,
a crop). Thus, if the business multiplier for the alfalfa
industry is 1.23, then the direct and indirect effects resulting
from one dollar of production is an additional 23 cents. A
summary of the crop industry business multipliers, along with
those for the state as presented by Walters and Ramey (1973),
is shown in Table 11.
TABLE 11. CROPLAND BUSINESS MULTIPLIERS PER DOLLAR OF PRODUC-
TION IN THE GRAND VALLEY (WALTERS AND RAMEY, 1973)
Alfalfa
Corn Orchards
Pastures Grains Sugar
beets
Walker
Walters
Ramey (
(1975)
&
1973)
1.
2.
23
10
2.
2.
20 2.24
10
1.31 1.51 2
1
.53
.80
The use of the input-output model by economists is generally
common practice because of its quantitative description of the
economy of an area or a region. Data for these models usually
90
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are collected by field surveys and then reconciled with the
secondary sources such as county agricultural statistics prepared
by the Colorado Department of Agriculture. Thus, input data to
the model are best developed by field experience and sampling
data.
Alternative Taxing Schemes
The basis for deciding upon the structure of a taxing
system may be selected from a number of alternatives which can
be grouped into two classifications. The first is a taxing
alternative in which assessments are made against selected
salinity producing processes according to an objective of least-
cost criteria. The second group of taxing alternatives are
those restrained to applying some tax is to stimulate the
structural and management improvements which would reduce salin-
ity effects, all agricultural processes should be encouraged to
alter existing practices. Three models must be developed before
results can be generated relating to salinity control through
taxation. The hydro-salinity model delineated the agriculture
activities causing salinity and quantified their effects. An
analysis of damages created through the use of saline water
supplies in the Lower Basin identifies the damages originating
in the Grand Valley by tracing the salinity concentrations back
upstream. The linkage between these two models is the annual
cost per metric ton of salt attributable to the Grand Valley.
The interaction of the models and the input-output economy model
for the Grand Valley establish a "pollution or salinity
coefficient." The salinity coefficient is the linkage among
the three models and is defined as the dollar cost of salinity
related detriments per dollar of output from each economic
sector in the local economy.
The salinity coefficients integrating the three modeling
systems present some interesting alternatives for assessing
taxes against the croplands in Grand Valley to affect salinity
control. The formats of these alternatives are as follows:
(a) directly related salinity damages; and (b) per acre equiva-
lent salt loading; and (c) salinity coefficients; and (d) gross
revenue.
The four taxing alternatives discussed above are by no
means an exhaustive list of the possibilities, although they
were selected to represent the set of taxing policies aimed at
stimulating improvements in local irrigation systems. The pur-
pose here is to illustrate how the linkage of economic and
hydrologic models can be made to assess the concept of pollution
taxation as a measure to effect solutions to water pollution
problems.
A comparison of the taxing plans presented should center on
two major questions: (a) how well will the measure induce local
91
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salinity control improvements; and (b) what would be the local
economic impact of a taxing program.
More than one-half of the salt pickup in the Grand Valley
comes from seepage losses in the water conveyance system.
Existing plans indicate that the initial salinity control efforts
will involve rehabilitation of canals, ditches, laterals, and
their appurtenances. Such a program must be undertaken with
the cooperation of local landowners because the system is pri-
vately owned and operated. However, the application of water on
the croplands themselves also requires substantial improvement.
Consequently, an important comparison of the taxation procedures
would be how well they would encourage either self-improvement
or offset the costs of having certain improvements made by
others. Walker (1975) concluded that a system of taxation based
on equivalent salt loading would be best suited for the local
system because it exhibited the best balance between conveyance
and on-farm improvements.
The equivalent salt loading concept is predicated on the
basis that the primary unit in the salinity problems in the
Colorado River Basin, at least so far as control is concerned,
is mass or tonnage of salts being carried by the water flows.
Under the equivalent salt loading approach, the respective
allocation of taxes for any given level of desired salt loading
reduction would be as follows:
Alfalfa 14.3%
Corn 17.8%
Orchards 12.1%
Pasture 15.2%
Grains 21.2%
Sugar Beets 19.4%
Application of Taxation
Taxation will not likely be employed to remedy the salinity
problems in the Colorado River Basin. In the reports prepared
during this study, the results of which are summarized herein,
the costs of improving local agricultural practices to reduce
salt loading are less than the currently reported damage figures
until a program requiring a reduction of more than about two-
thirds of the salt loading is reached. In other words, if the
volume of salts to be eliminated from the Grand Valley return
flows is less than about 350,000 to 400,000 metric tons, the
taxes would always be higher than the actual costs. Consider
the following example. Suppose the Grand Valley salt contri-
bution was to be reduced by 200,000 metric tons annually.
Further, assume that a metric ton per year contribution resulted
in downstream damages of $150 (Valentine, 1974). The taxation
approach would levy the following charges to the Grand Valley:
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Alfalfa $ 726/hectare
Corn $ 922/hectare
Orchards $l,293/hectare
Pasture $l,092/hectare
Grains $2,023/hectare
Sugar Beets $2,734/hectare
As shown in the previous section, this amount of salinity can
be reduced by an average expenditure of approximately $720 per
hectare. Note that these are present value figures. If the
desired salinity contribution was raised to 400,000 metric tons
annually, the taxes would be less than the costs.
It is evident that taxation is a linear policy inasmuch
as the tax is not related to the level of control. Consequently,
taxation does not segregate the alternative measures for salinity
control based on individual cost-effectiveness relations. On
the other hand, the evaluation of salinity control alternatives
using their associated cost-effectiveness functions automatically
indicates the most cost-effective improvements as the salinity
control programs are initiated. The taxation alternative has
not been further considered.
Even though significant strides have been made towards
pollution control, a critical problem remains for which neither
the quality standard nor effluent tax can be properly applied.
The problem is that a quantitative contribution to the diffuse
pollution created by irrigation return flows is very difficult
to ascribe to an individual water user.
LEGAL CONSIDERATIONS
Beneficial Use
A major legal problem that is universal throughout the 17
western states is the failure to enforce the concept of benefi-
cial use provisions of the law. The reason is twofold. One has
to do with the fact that the definition of beneficial use is
nebulous and, thus, lacks appropriate direction for administra-
tors to follow or courts to interpret. The second derives from
a lacK of social consciousness on the part of water users so
that the burden of proving nonbeneficial use is upon the state,
which is really an administrative impossibility. Generally, our
system of water law places emphasis upon the right to use water,
not the duty to use it appropriately.
Cases in Colorado and other western states reflect the
difficulty of enforcing the general concept of beneficial use
under which water is allocated and the exercise of the right to
use follows. It is suggested, therefore, that the State
Engineer's Office develop and adopt criteria for beneficial use
93
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as an agency rule or regulation. These criteria for use will in
effect define the standards of water use efficiency in the con-
veyance and application of water under the exercise of a water
right relative to quantity diversions, water use, and quality
discharge. They will also provide the basis for shifting the
burden of proper use of the public resource upon the benefactor
(both purveyor and user) and in essence identify the duty for
delivery, use and removal of water.
Influent Standards
As stated earlier in this report, the demonstration project
used each lateral as a subsystem because this provided control
at the lateral turnout gate. This turnout gate is a critical
control point in the irrigation system because it represents the
terminal point of responsibility for most of the irrigation
companies in Grand Valley (in some cases, under the Grand Valley
Water Users Association, there is responsibility along the upper
portions of the lateral). In turn, the control point for each
irrigation company is the point of diversion from either the
Colorado River or Gunnison River. The responsibility for these
river diversions belongs to a water commissioner who is a state
employee, while the amount of water discharged at each turnout
gate alone a canal is the responsibility of water masters or
ditch riders, who are employees of the particular irrigation
company.
Proper operation of an improved lateral subsystem will
result in a significant reduction in the discharge requirement
at the turnout gate, as compared with lateral diversions prior
to an improvement program. Since the lateral turnout gate is
an important control point, standards for water use could be
applied at each turnout gate, which could be classified as an
influent pollution control standard. An initial influent
standard goal should be the intended water duty for the irriga-
tion lands. This should be measured at each farm inlet, which
can then be translated back to the lateral turnout gate taking
into consideration lateral seepage losses (which could be
essentially ignored if the laterals were lined or converted to
pipelines). An important consideration should be to use either
a volumetric water duty as a standard, or a variable flow rate
which is dependent upon the changing water requirements of the
crops during an irrigation season.
The approach of using influent standards has the advantage
of alleviating the salinity problem by improved water management
practices, rather than end-of-pipe treatment, or partially re-
ducing the salt load by using effluent standards under a permit
program. The success of an influent approach is dependent upon:
(a) use of numerous flow measuring devices; (b) adequate techni-
cal assistance for working with and advising farmers on improved
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irrigation practices and methods; and (c) availability of funds
for making the necessary structural improvements.
Development of a Water Market
The establishment of a water market would alter the present
institutional arrangement, so it would seem desirable from a
practical standpoint to alter that arrangement as little as
possible in order to assure its acceptance. In order to minimize
the disruption to the present institutional arrangements for
allocating irrigation water, a water rental market could be
established. Under such an arrangement, a water rental market
would utilize the present structure of water rights and allot-
ments and would permit the rental of surplus water to upstream
water users (with the "rental" waters retaining their original
appropriation dates) without jeopardizing these rights and
allotments.
There is a legal requirement that water transfers not injure
other water rights. In most cases, transfers must be restricted
to the amount previously used consumptively; however, since the
return flows from the Grand Valley are not reused in the State
of Colorado, there would be no downstream damages to water rights
holders by transferring water upstream of Grand Valley. Such
transfers will not be detrimental to downstream users so long
as the State of Colorado does not exceed its entitlement to the
Colorado River, which presently is not the case. In addition,
the Grand Valley Irrigation Company holds the first priority
water right on the Colorado River within the boundaries of the
State of Colorado. There are many other early priority rights
held by the various irrigation companies in Grand Valley. The
"Cameo Demand," which is the reguired water deliveries as
measured at a USGS stream gaging station located on the Colorado
River upstream from Grand Valley, is for 1,850 cfs during the
irrigation season. These rights are for irrigation and hydro-
power. This "Cameo Demand" has a definite impact upon the value
of upstream junior water rights, as well as future upstream
water resources development.
The Upper Colorado River Basin, because of its vast reserves
of oil shale and near-surface coal, is becoming one of the most
important areas in the Nation for energy development. However,
energy development will also result in increased salinity levels
in the Colorado River unless mitigating alternatives are
employed. There may be some advantages in allowing the water
quality degradation resulting from an energy complex to be offset
by improvements at another location in the river system, usually
within the same state boundaries. One of the most viable off-
site alternatives is irrigation improvements in agricultural
areas. In particular, the Grand Valley offers a unique opportu-
nity for coordinating energy development with improved irriga-
tion water management. An energy complex could make sufficient
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investments in irrigation improvements to almost exactly offset
the salinity detriments resulting from the energy complex opera-
tion, thereby satisfying the nondegradation policy for the basin.
Such investments have the added advantage of increasing agri-
cultural productivity. Also, irrigation improvements in such
areas would decrease the diversion requirements, which could in
turn be transferred upstream. This decreased diversion require-
ment provides additional opportunities for improved basinwide
water management provided changes in Colorado water laws can be
achieved (Skogerboe et al., 1975).
An impediment in the exercise of water rights is the
transfer restriction of rights within an irrigation system to
other uses, or outside of the basin. This constraint may exist
in the substantive water law or as a result of the organizational
and administrative system of the state. There are few states
that prevent the sale and transfer of water rights to other
present uses. States restricting transfers rely upon the
appurtenancy concept to prevent such shifts. However, the law
should be modified or changed to reflect state encouragement in
the renting, leasing, transferring or selling of water rights to
other uses and places so long as the vested rights of others are
protected. Although there are no restrictions on the transfer
of water rights in Colorado, the organizational red tape—delay
and expense—acts as an impediment. Changes in the administra-
tive and judicial system should be made to facilitate exchanges
of water rights. Recognition of such a right and a change in
the concept of beneficial use to include recreation, aesthetics,
fish and wildlife and other beneficial uses would serve to
nullify the fear of losing that portion of the water right not
exercised by permitting the transfer of the unneeded portions
to other uses within the system.
Removing these rigidities in the law to give the water right
holder greater freedom and flexibility will eliminate many of
the irrigation problems perpetuated by the appropriation doctrine.
A legal solution would be to merge the economic benefits from a
more liberal transfer policy into legal guidelines that still
provide protection to existing water right holders. This would
require the adoption of an incentive mechanism to encourage
water users to "market transfer" some of their water through
the irrigation companies (i.e., Grand Valley Irrigation Company
or Grand Valley Water Users Association), or possibly through
the Grand Valley Canal Systems, Inc. Water could be rented or
leased to upstream water users (i.e., other irrigators or new
energy complexes) with the revenues being used to further im-
prove the irrigation system in Grand Valley.
A substantive change in the water laws affecting the
administrative organization of the state which should be enacted
to enable a greater degree of cooperation between the state
agency and water users, and at the same time permit the state
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to concentrate on the development of a desirable state water
plan, is to enact legislation permitting the state water re-
sources agency or other public organizations the right to
acquire water through appropriation, purchase, abandonment or
condemnation. The significance can be seen at the state and
interstate level by granting the state greater freedom in
carrying out its responsibilities and negotiating agreements with
its water users and other states.
What is needed is a means of allocating and reallocating
water within the irrigation system by an organization cognizant
of the needs of water users within the system, the state water
development plan, and the basin and international impacts. The
development of a centralized state brokerage system is suggested
which would be operated as a market center for the exchange and
sale of water rights, or renting of water available under the
rights held (Radosevich, 1972).
This brokerage system could be organized as a public or
private institution. Water users would be permitted to divert
only that amount of water necessary for their operation, without
fear of losing the unused decreed quantity, and lease or rent
the difference to other users. Hence, there would be an econo-
mic incentive to implement more efficient irrigation water
management in an attempt to reduce the quantity of water applied.
A brokerage system created as a public entity could be
established in the Office of the State Engineer or water plan-
ning and resource department (i.e., Colorado Water Conservation
Board). These offices or their respective divisional offices
in the various basins within the state would list all available
water for rent, lease, exchange or sale. The location of avail-
able waters will determine the impact upon other vested rights,
but the responsibility for delivery and protection of such other
rights would rest upon either the water right holder or water
acquirer. Uniform prices for units of water could be established,
or the available water could be transacted to the highest bidder.
The adoption of such a system in state organization would require
changes in agency laws to permit this type of activity. Like-
wise, it would be imperative that the state should have the
power to purchase, condemn or receive water rights in the name
of the state. This would allow the state to take action against
appropriators who refuse to implement efficient practices,
acquire their unused rights, and retain them for future use
while renting or leasing the water during the interim. A percent
of the transacted price would be retained for the operation and
maintenance expense of the brokerage system (Radosevich, 1972) .
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SECTION 8
IMPLEMENTATION
BASIC PROGRAM
The optimizational analysis of the cost-effectiveness
functions for the various salinity control alternatives clearly
shows that the basic program which should be implemented con-
sists of lateral lining and on-farm improvements. Depending
upon the level of salt load reduction being sought, after imple-
menting lateral lining and on-farm improvements, the next
priority would be concrete lining of the Government Highline
Canal. At this point, the implementation of these technologies
at the investment levels indicated in Figure 18 would be econo-
mically feasible based on downstream damages alone, without
taking into consideration the local benefits to the farmers and
people living in the Grand Valley. However, it may be possible,
if similar analyses were done for each of the irrigated areas
in the Upper Colorado River Basin, that concrete lining of the
Government Highline Canal would not be as cost-effective as
lateral lining and on-farm improvements in other areas (i.e.,
lateral lining and on-farm improvements in the Gunnison Valley
may be more cost-effective than concrete lining the Government
Hiqhline Canal).
Lining the Government Highline Canal is the easiest
technology to implement because this canal was originally con-
structed as part of the USBR Grand Valley Project, and the USBR
would be technically responsible for the construction of the
concrete lining. The implementation of lateral lining and on-
farm improvements is not so easy. First of all, lateral lining
should not be implemented by itself, followed by on-farm improve-
ments, instead, lateral lining and on-farm improvements must be
planned simultaneously with the participation of the water users
under each lateral. Otherwise, the full potential benefits of
the lateral lining will not be realized. A significant point to
bear in mind is that the construction of physical improvements
only increases the potential for improved water management (and
consequent salt load reduction), while the operation and manage-
ment of these new physical facilities dictates the degree to
which this potential is realized. As stated earlier in this
report, irrigation scheduling would be a necessary requirement
in achieving the potential of the on-farm improvements.
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hater
tne
mprovhater
improve tne tinent to the implementation of a
of lateral lining and on-farm improvements on a
lateral-by-lateral basis.
IMPLEMENTATION ACTIVITIES
Considerable experience has been gainec 1 in
with farmers Curing the ^^ ^.^ *nd fa™er feedback in
Demonstration Project. ^ese experie research
recent yea" ^/f J^is for tne development of some broad
fi^SinesPror a program to implement a combination of lateral
?^n« and on- farm improvements . The specific objectives of
^n-In^pl mentation Pro-am are as follovs: «., ^ncour^
farmer Pa^icipation;^b} train Praining materials; (e)
^cognfze !ne 'efforts ol farmers; and (f) evaluate implementation
activities .
This section of the report provides a brief discussion of
- -'
active farmer participation
Participation
One of the unique characteristics of improving on-farm
™n<- i«; that the degree of success is highly depend-
' onhTdegree ^participation of each individual farmer,
«*n as their ability to cooperate collectively for the
as well*s their aci y * The construction of on-farm
common ?°?^°^ve_ents only provides an increased potential for
Refuse e^clency! wnereL the degree of potential which will
^achieved is dependent upon the operation, management, and
b • ^ance of the physical improvements. This, in turn, is
maintenance of tne p y a£ility of technical assistance
delV?deS farmer attitudes, and the degree of credibility between
?nose?ndiv?^als providing the technical assistance and the
farmers involved.
rr-^dibilitv and acceptance by the farmers begins when the
v,a«ir training and motivational materials are initially used to
describe the problem. Efforts to organize the water users under
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each lateral provide an opportune time to develop early rapport
with the farmers. Credibility and acceptance of the technical
personnel by farmers during the planning and implementation of
individual farm plans for improved water management is essential
to the long-range goals of a control program. Credibility and
good communication must exist during the collective negotiations
in determining the physical improvements to be made on a lateral.
Farmer participation is crucial during these stages in order to
evolve a plan of development which is acceptable to the water
users and also satisfies the goals of the salinity control
program.
The final step in this process dictates the real success of
the entire program. After spending vast sums of money to con-
struct physical improvements/ the test of effectiveness centers
largely around the operation/ management, and maintenance of
these improvements. This is the phase of the work where the rapport
developed with the farmers pays huge dividends. Unfortunately,
this step is very time-consuming and most frequently neglected.
Considerable evaluation is required to "tune-up" these new
improvements so that they are operating at their potential, and
the key variable in this operation is the farmer decision maker.
Training Field Personnel
The primary agency providing technical assistance to farmers
for a salinity control program will likely be the SCS, The SCS
will likely cooperate with the USER in the provision of required
technical assistance. Given the levels of manpower needed to
work with farmers, and the current shortage of trained manpower
with on-farm water management experience, special short courses
for training personnel will likely be required. As a complement
to technical competence, personnel working directly with farmers
should know how to develop good working relationships with
farmer clients and have definite skills and knowledge related to
organizing farmers into water user associations for action pro-
grams. Personnel also must have the capabilities required for
assisting farmers in "tuning-up" furrow irrigation practices and
the maintenance of improved conveyance systems.
Technical assistance to farmers will include convincing them
to use "scientific" irrigation scheduling procedures and other
improved irrigation practices. The focus on improved irrigation
scheduling is essential because the existing piecemeal methods
of scheduling in Grand Valley have been found to be inadequate
as an individual salinity control measure.
Water User Organizations
A crucial element in implementation of an effective salinity
control program is gaining the participation of the users. The
unit of organization should be the lateral subsystem because it
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is a natural hydrologic unit where farmers know each other and
interact on a day-to-day basis. In Grand Valley, the jurisdic-
tion of the irrigation companies does not include the laterals
in most cases; so, there is an organizational vacuum for most
laterals. The goal should be to gain participation by all water
users on each lateral. This may not always be possible due to
human problems. While the organization could be on an ad hoc or
informal basis, experience indicates that it is probably best to
aim for a formal organization with rules developed by the members
themselves. A formal organization with its own rules and regu-
lations also makes it easier for the implementing agency because
all parties have a knowledge of the structure and mechanisms
involved. When the leadership is defined, this facilitates the
work of the implementing agencies.
For example, the water users on several laterals in the
Grand Valley have organized formally as nonprofit mutual irri-
gation companies under the state laws of Colorado. One problem
the members of these associations have encountered has been
lawyer fees for incorporation. This can be partially overcome
by providing model sets of bylaws and other provisions to farmers
considering such organization. In fact, alternative models can
be provided farmers, and they should decide the set of rules and
regulations which meet their special needs for the most effective
means of operation and maintenance of the lateral subsystem.
These models could be provided in a well-prepared manual or
booklet and made available to interested farmers. The booklet
should explain the benefits of formal organization, how to
organize legally, and the types of bylaws and provisions
required. It is important that such a booklet be well illus-
trated and in easily understood language. Often such booklets
are not well prepared and contain too much legal jargon which
farmers cannot fully understand. The goal is to design usable
materials on how-to-do-it for the farmer audience.
Basic Farmer Training Materials
Materials are needed to motivate farmers and help them
understand the importance to themselves and their communities of
improving present water management practices for increased crop
production and the control of salinity. Data obtained in prob-
lem identification and alternative solutions to the problem
should be utilized in preparing well-illustrated materials for
farmers. These materials should graphically and clearly define
the problem, explain its consequences, document the contributing
factors, and explain the costs and benefits. Alternative solu-
tions should be carefully delineated and estimated costs
presented.
Techniques for such communications could include slide
shows, an easy-to-read booklet, and selective use of local mass
media channels. The slide show developed for the Grand Valley
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Salinity Control Demonstration Project has been well received
and has been presented many times in the community at special
public meetings and for civic groups (Bargsten et al., 1974).
Since a comprehensive salinity control program requires changes
in attitudes and behavior wherever such programs are proposed,
the first major consideration should be the design of definite
communication strategies. To make the program successful in
reaching all water users and the community, several complementary
communication methods should be used over time to reinforce the
central messages. Local conditions and communication sources
and channels need to be identified and used with imagination.
Essentially, salinity control is a problem of water conservation
which requires much education on the part of farmers and
communities.
Farmer Client Recognition
The Irrigation Field Days held at Grand Valley, and other
experiences, have demonstrated the importance of farmer recogni-
tion. Farmers usually can sell a program to other farmers more
successfully than public officials. Where possible, farmers
should be given special recognition, because the success of any
salinity control program rests finally with the degree of
participation by the farmers themselves. There are a number of
methods which can be effectively utilized for using farmer
recognition to motivate other farmers.
The proper use of radio and television announcements and
newspaper articles can be of considerable help in fostering
enthusiasm for the program. The local newspaper provides excel-
lent coverage on news related to natural resouces and agricul-
ture. The local newspaper in Grand Junction has been very
helpful and always willing to include news articles pertaining
to the Grand Valley Salinity Control Demonstration Project. The
television station and some radio stations in Grand Junction
have cooperated with the project in disseminating news related
to the salinity control research activities.
The news media, in addition to news reports about current
activities of the salinity program, are also very interested in
covering human interest stories. If these human interest reports
and farmers' testimonials are well prepared, they can create
much interest in other farmers for the programs. Such publi-
city is free and probably can generate better image-building
for the state and federal agencies than they can do for
themselves.
Awards should be given to those farmers who have made
exceptional progress in improving their on-farm water manage-
ment practices. Awards for providing leadership in the water
user association under each lateral should be considered. Awards
presented to each water user served by the lateral demonstrating
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the most efficient use of water would be highly effective in
promoting the goals of an improvement program. News media
coverage of such awards also provides additional incentives for
improved water management on the part of other farmers. Framed
photographs of farmers engaged in improvement activities with an
inscription could be considered for presentation. Plaques could
be presented to cooperators to show appreciation for their
contributions.
An excellent method of employing farmers for promoting wide
interest in a project once substantial progress has been made in
an improvement program is the use of field days. In the Grand
Valley, a Field Day could be held annually which would involve
strong participation by local farmers. Water users and irri-
gation company leadership from other valleys in the Upper Basin
could be given special invitations to attend the Field Day in
order to observe firsthand the implementation of a salinity con-
trol program. In addition, special tours could be arranged
during other times of the year for a group of irrigators from
any particular area to visit the Grand Valley and meet with
farmers who have participated in the program. The emphasis
should be farmer-to-farmer interaction, with the Grand Valley
farmers being highlighted, rather than technical assistance
personnel. These personnel, however, should play a strong back-
stage role in facilitating this interaction.
Evaluation and Refinement of Implementation Activities
Evaluation research techniques are available which, if
properly utilized, can be used to determine the strengths and
weaknesses of project implementation. Information from such
evaluative studies is needed by sponsoring agencies and by proj-
ect implementors to discover the most effective and efficient
methods of working cooperatively with farmers. Continual and
periodic evaluation mechanisms are needed in order to continually
refine the implementation program. Feedback is needed both
from farmers and technical assistance personnel for improving:
(a) the delivery of the salinity control technological package;
(b) the operation and management of the physical improvements;
and (c) the cost-effectiveness of the entire program. Credibi-
lity with the farmers will be strengthened by continually re-
fining and improving the implementation program.
Extension communication strategies should be designed into
the project work plans in order that various techniques can .be
effectively evaluated. While technical expertise for such pro-
grams is usually adequate, there is a general weakness in de-
signing and evaluating extension communication strategies.
Technical assistants should be given short courses in skills
needed for working effectively with farmers. As stated often
in this report, the key variable in achieving successful program
implementation and long-term effective management of improved
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systems is the farmer client himself. Consequently, communication
techniques used for working with farmers as individuals and
groups should be designed into the implementation program and
evaluated to the same degree as the technical components and
activities.
INSTITUTIONAL ARRANGEMENTS
Lateral and On-Farm Improvements
As stated earlier, lateral lining and on-farm improvements
should not be separate programs, but rather a single program
which is planned and developed with participation by the
affected water users on a lateral-by-lateral basis. Presently,
the responsibilities are being divided between the USBR for
lateral lining and the SCS for on-farm improvements. There is
a serious question as to whether or not these components, which
are the "heart" of an action salinity control program for Grand
Valley, should be divided between two federal agencies. Besides
the problems of coordination between federal agencies and having
two separate agencies interacting with the farmers, this report
has shown that the difference in costs for lateral lining will
vary significantly depending on which agency is responsible.
Using 1976 costs, the writers have estimated that the SCS can
accomplish the lateral lining program at a cost of $10 million,
while the USBR estimates the cost of $30 million. In addition,
the SCS program would have the advantage of allowing participa-
tion by farmers when pipelines are installed, which is of con-
siderable help to farmers in: (a) meeting their cost sharing
requirements; (b) developing a better understanding of how the
newly improved lateral subsystem will operate; (c) developing a
pride in the improvements; and (d) having a commitment to
effectively manage and maintain the new improvements.
This particular program of lateral lining (or pipelines) and
on-farm improvements could be initiated immediately. In imple-
menting such a program, there is a question as to whether or not
the construction activities should be scattered throughout the
Grand Valley to serve as demonstrations to nearby farmers, or
whether these improvements should be concentrated at the lower
end of the Valley and then moved upstream with time. The
advantage in beginning at the lower end of the Valley is that
after completion of construction, and then operation for a few
years, the required diversion at each lateral turnout gate would
be more accurately known, which would allow a more proper sizing
of the canal section for purposes of concrete lining. The canal
lining program should begin at the lower end of Grand Valley,
with the lining program moving up the Valley with time.
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Lining Government Highline Canal
The decision of whether or not to concrete line the
Government Highline Canal is dependent upon the desired level of
salt load reduction from Grand Valley, which in turn is dependent
upon the cost-effectiveness of alternatives in other irrigated
areas of the Upper Colorado River Basin. At this time, studies
have not been completed which would allow a comparison of lining
the Government Highline Canal with salinity control alternatives
in the Gunnison Valley, Uinta Basin, etc. Besides waiting on
the completion of basinwide studies before making a decision
whether or not to proceed with a lining program, there are some
other advantages in postponing a decision:
1) The program of lateral lining and on-farm improve-
ments needs to be underway, and a number of
improved lateral subsystems operated for a few
years, in order to accurately determine how much
present lateral diversions can be reduced, so that
the canal will be properly sized, rather than
constructing a canal which would have a larger
capacity than necessary.
2) The opportunities for lining the Grand Valley
Canal, discussed below, which involves the
institutionalization of a water market, would
also prove advantageous in facilitating the
lining of the Government Highline Canal.
The primary disadvantages in postponing a decision to line the
Government Highline Canal are: (a) rising construction costs;
and (b) allowing higher salt loads to continue entering the
Colorado River during the interim.
Lining Grand Valley Canal
In Section 7, the development of a water market for Grand
Valley was discussed. The lateral lining and on-farm improve-
ment program will result in a decreased discharge requirement
at the lateral turnout gate. State legislation would be
required to allow this water savings (only a part of this sav-
ings is a reduction in consumptive use by phreatophytes) to be
transferred for use upstream through a rental or lease agree-
ment. The revenues from these transfers can be used for irri-
gation scheduling (as discussed below) and canal lining.
Since the Grand Valley Irrigation Company (Grand Valley
Canal) has the first priority water right on the Colorado River
(in the State of Colorado), any water savings under this system
would be extremely valuable to upstream water users. The
results of the cost-effectiveness and optimization analysis
described in Section 6 shows that lining the Grand Valley Canal
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has an average cost of about $500 per metric ton of salt
reduction. In comparison, the average reduction cost per metric
ton of salt load reaching the Colorado River is $300 for lining
the Government Highline Canal and $50 to $100 for lateral lining
and on-farm improvements. Consequently, for every $0.60 of
water rental revenue applied to lining the Grand Valley Canal,
the Federal Government could consider a cost sharing of $0.40 in
order to make the salinity control cost-effectiveness of the
Grand Valley Canal System in line with that of the Government
Highline Canal.
Allowing new industries, such as energy complexes, and new
interbasin water transfers to offset their salinity detriments
(which are primarily salt concentrating effects) by lining a
sufficient length of canal in Grand Valley would be highly
advantageous because of the additional benefits resulting from
increased agricultural productivity, as well as water savings
from reduced seepage losses. Rather than allowing these new
water users to offset their salinity detriments by lining the
Government Highline Canal, which would cost less, there are a
number of advantages in requiring that the Grand Valley Canal be
lined: (a) there is a lack of options for lining the Grand
Valley Canal; (b) having the first priority water right on the
river means that any water savings (i.e., reduced seepage losses
resulting from canal lining) has a higher revenue value than any
other water right, which will provide funds for additional canal
lining; and (c) the cost to new water users (energy complexes,
other industries and cities) is still relatively insignificant.
Irrigation Scheduling
In implementing the program for lateral and on-farm improvements,
irrigation scheduling will have to be a strong component. For a
number of years, the technical assistance personnel will have
to take responsibility. The USSR presently has an irrigation
scheduling program in the Valley and would appear to be the
logical agency to continue this activity. However, if the SCS
is going to have the responsibility for the lateral and on-farm
improvements, then there is some advantage, because of their
continual interaction with farmers, for the SCS in collaboration
with the Agricultural Research Service (ARS) to handle the
responsibility for implementing irrigation scheduling on improved
lateral subsystems.
After a number of years, the irrigation scheduling program
should be turned over to private commercial organizations, the
irrigation companies, or the Grand Valley Canal Systems, Inc.
There are two options in obtaining revenues to provide this ser-
vice, either charge the farmer through his annual water assess-
ment fees or utilize water rental revenues. The advantages in
having the Grand Valley Canal Systems, Inc. take responsibility
in later years for an irrigation scheduling program are: (a)
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all of the canals in the Valley could be operated as a system;
(b) the management capability of the local irrigation interests
would be strengthened; and (c) there would be more involvement
by irrigation company leadership in the equitable distribution
of water to irrigators.
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REFERENCES
Bargsten, G. , G.V. Sfcogerboe, W.R. Walker, and J.P. Law, 1974
The Grand Valley, An Environmental Challenge, u.s. Environ-
mental Protection Agency, Robert S. Kerr Environmental
Research Laboratory. Ada, Oklahoma. February.
Baumol, W.J., 1972. On Taxation and the Control of Externalities,
American Economic Review. Vol. 62, No. 3. June. p. 319.
Bessler, M.B. and J.T. Maletic, 1975. Salinity Control and the
Federal Water Quality Act. Journal of the Hydraulics
Division, ASAE. Vol. 101, No. HY5. May. pp. 581-594.
Duke, H.R., E.G. Kruse, S.R. Olsen, D.F. Champion, and D.C.
Kincaid, 1976. Irrigation Return Flow Quality as Affected
by Irrigation Water Management in the Grand Valley of
Colorado. Agricultural Research Service, U.S. Department
of Agriculture, Fort Collins, Colorado. October.
Elkin, A.D., 1976. Grand Valley Salinity Study: Investigations
of Sediment and Salt Yields in Diffuse Areas, Mesa County
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neer, Soil Conservation Service, Denver, Colorado.
Evans, R.G., 1977. Improved Semi-Automatic Gates for Cut-Back
Surface Irrigation Systems. Transactions of the ASAE.
Vol. 20, No. 1. pp. 105-108, 112.
Evans, R.G., W.R. Walker, G.V. Skogerboe, and C.W. Binder, 1978a
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108
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109
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Skogerboe, G.V. and W.R. Walker, 1972. Evaluation of Canal
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110
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Ill
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112
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO.
EPA-600/2-78-162
3. RECIPIENT'S ACCESSIOI^NO.
4. TITLE AND SUBTITLE
"BEST MANAGEMENT PRACTICES" FOR SALINITY CONTROL IN
GRAND VALLEY
5. REPORT DATE
July 1978 issuing date
6. PERFORMING ORGANIZATION CODE
7Wynn R. Walker, Gaylord V. Skogerboe, and Robert G,
Evans
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Agricultural and Chemical Engineering Department
Colorado State University
Fort Collins, Colorado 80523
10. PROGRAM ELEMENT NO.
1BB770
11. CONTRACT/GRANT NO.
S-802985
12. SPONSORING AGENCY NAME AND ADDRESS
Robert S. Kerr Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Ada, Oklahoma 74820
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA/600/15
15. SUPPLEMENTARY NOTES
124 pages, 21 fig., 11 tab., 46 ref.
16 ABSTRACT
A nontechnical summary of several research activities in the Grand Valley is given.
Analyses of alternative measures of reducina the salt load originating from the
Valley as a result of irrigation return flows are presented. These alternatives
include conveyance channel linings, field relief drainage, on-farm improvements (such
as irrigation scheduling, head ditch linings, sprinkler and trickle irriqation),
economic control measures such as taxation and land retirement, modified legal con-
straints, and collection and treatment of return flows with desalting systems. The
best management practices for salinity control in the Grand Valley should be orimarilj
the structural rehabilitation and operational modification of the local irrigation
system lying below the turnouts from the major canal systems. Canal linings appear
in the optimal strategies at higher levels of valley-wide salinity control emphasis
but only so far as lining the Government Highline Canal is concerned. Desalting
would become a cost-effective alternative after major irrigation system improvements
are implemented.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
COS AT I Hield, Group
Irrigation, Fluid infiltration, Salinity,
Seepage, Water distribution, Water loss,
Water pollution, Water quality, Sprinkler
irrigation
irrigation (practices,
systems, efficiency, meth-
ods, management), Furrow
irrigation, Border irri-
gation, Colorado River,
Salinity control, Grand
Valley, Return flow
98C
13. DISTRIBUTION STATEMENT
TO RELEASE TO THE PUBLIC
19. SECURITY CLASS (This Reporti
UNCLASSIFIED
21. NO. OF PAGES
125
20. SECURITY CLASS tThispage)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
13
u. s. wmnuian PMTING
!978-757-uo/i4i2
NO. SHI
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