United States
Environmental Protection
Agency
Robert S Kerr Environmental Research EPA-GOO/2-78-16 1
Laboratory y 1978
Evaluation
of Irrigation Methods
for Salinity Control
in Grand Valley
-------
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.
-------
EPA-600/2-78-161
July 1978
EVALUATION OF IRRIGATION METHODS FOR
SALINITY CONTROL IN GRAND VALLEY
by
Robert G. Evans
Wynn R. Walker
Gaylord V. Skogerboe
Stephen W. Smith
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
-------
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
-------
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
industrial/municipal wastewaters.
This report contributes to the knowledge essential if the
EPA is to meet the requirements of environmental laws that it
establishes and enforce pollution control standards which are
reasonable, cost effective and provide adequate protection for
the American public.
William C. Galegar
Director
Robert S. Kerr Environmental
Research Laboratory
111
-------
PREFACE
This report is the second in a series of three reports
resulting from U.S. Environmental Protection Agency Grant No.
S-802985 entitled, "Implementation of Agricultural Salinity
Control Technology in Grand Valley." This report is concerned
with the evaluation of furrow, border, sprinkler and trickle
irrigation as individual salinity control measures. The first
report in this series has the same title as the grant and
details the experimental design and the procedures used to
collect data on several types of on-farm improvements, field
drainage, canal and lateral linings and irrigation management
practices (such as irrigation scheduling) as salinity control
measures. The third report of this series "Best Management
Practices for Salinity Control in Grand Valley" develops the
methodology for determining the cost-effectiveness of individual
salinity control measures, as well as a complete package of
salinity control measures that should be implemented in the
Grand Valley.;
Another research project conducted in Grand Valley and
largely funded by the U.S. Environmental Protection Agency has
provided the necessary background in soil chemistry to support
the cost-effectiveness analysis in the above three reports.
This second project, "Irrigation Practices, Return Flow Salinity
and Crop Yields," was supported by EPA Grant No. S-800687. Two
reports resulted from this effort. The first report, "Irrigation
Practices and Return Flow Salinity," focuses upon the prediction
of subsurface irrigation return flow salinity. The second
report, "Potential Effects of Irrigation Practices on Crop
Yields in Grand Valley" focuses upon the impact of various
irrigation practices in determining crop yields, with particular
emphasis on maize (Zea Mays L.) and wheat.
iv
-------
ABSTRACT
Irrigation return flows in the Upper Colorado River Basin
carry large salt loads as a result of contact with the saline
soils and the marine derived geologic substratum. The Grand
Valley of western Colorado is a major contributor to the salinity
problems of the basin and is, therefore, a logical region to
test the effectiveness of agricultural salinity control alterna-
tives. This study emphasized the implementation of on-farm
salinity control alternatives; primarily evaluating irrigation
scheduling, furrow irrigation, sprinkler irrigation, and trickle
irrigation. Border irrigation was also evaluated, but was not
implemented as part of this study. The cost-effectiveness of
the various on-farm alternatives in the Grand Valley is
summarized and presented in this report.
This report is the second in a series of reports submitted
in fulfillment of Grant No. S-802985 by Colorado State University
under the sponsorship of the U.S. Environmental Protection
Agency. This report covers the period February 18, 1974 to
February 17, 1977 and work was completed as of June 17, 1977.
v
-------
CONTENTS
Foreword iii
Preface iv
Abstract v
Figures vii
Tables xi
Abbreviations and Symbols xii
Acknowledgments xiv
1. Introduction 1
2. Conclusions 17
3. Recommendations 20
4. The Grand Valley 23
5. Present Irrigation Practices 39
6. Irrigation Water Requirements 58
7. General Considerations in Irrigation ... 72
8. Furrow Irrigation 81
9. Border Irrigation. . 98
10. Evaluation of Sprinkler Irrigation .... 110
11. Trickle Irrigation 134
12. Comparison of Irrigation Methods for
Salinity Control 147
References 157
Bibliography 166
vii
-------
LIST OF FIGURES
Number Page
1 The Colorado River Basin 2
2 Relative magnitude and sources of salt in the
Colorado River Basin (USDI, FWPCA, 1970,
Appendix A) 3
3 Location of Grand Valley Salinity Control
Demonstration Project 6
4 Grand Valley Salinity Control Demonstration
Project 7
5 Map showing the location of the nine selected
lateral subsystems incorporated in the project,
and the locations of the previous canal linings,
irrigation .scheduling and drainage
investigations 14
6 Normal precipitation and temperature at Grand
Junction, Colorado (U.S. Department of
Commerce, 1968) 25
7 General geologic cross section of the Grand
Valley (USDA, 1955) 27
8 Soils map of irrigated lands in Grand Valley
(from USDA, 1955) 29
9 Approximate areal extent of cobble aquifer in the
Grand Valley 32
10 Frequency distribution of farms in the Grand
Valley (Leathers, 1975) 34
11 Frequency distribution of field sizes in the Grand
Valley (USDA Soil Conservation Service, 1976) . 35
12 Agricultural land use in the Grand Valley (Walker
and Skogerboe, 1971) 37
VI11
-------
Number Page
13 Graphic representation of the magnitude and
distribution of water flows in the Grand Valley
for 1968 (Walker, 1970) 40
14 Grand Valley canal distribution system 42
15 Frequency distribution of lateral lengths in the
Grand Valley (USDI, USER, 1975) 49
16 Frequency distribution of the area contained under ,
laterals in the Grand Valley (USDI, USER, 1975) . 50
17 Frequency distribution of field widths in the
Grand Valley (USDA-SCS, 1976). 52
18 Frequency distribution of field lengths in the
Grand Valley (USDA-SCS, 1976) 53
19 Frequency distribution of field slopes (in
percent) in the Grand Valley (USDA-SCS, 1976). . 54
20 Relative infiltration rate function for perennial
and annual crops in the Grand Valley 55
21 Seasonal distribution of salt pickup from the farms
in the test area (Skogerboe et al., 1974b) ... 57
22 Schematic view of the constant water level tank
grass lysimeter used in the Grand Valley .... 63
23 Comparison of lysimeter data with the Blaney-
Criddle estimates for well-watered grass in
1975 65
24 Comparison of lysimeter data with the Jensen-
Haise estimate for alfalfa in 1975 67
25 Comparison of lysimeter data and the Penman
equation estimate for alfalfa in 1975 68
26 Definition sketch of surface irrigation application
uniformity for a) the case where part of the
field is underirrigated, b) the case of zero
underirrigated, and c) conditions of
significant overirrigation 89
27 Application efficiency relationship for furrow
irrigation for the case of zero underirrigation
(after Gerards, 1978) 92
IX
-------
Number
28 Field efficiency relationships for furrow
irrigation for the case of zero under-
irrigation (after Gerards, 1978) 93
29 Seasonal distribution of computed application
efficiencies for common crops grown in Grand
Valley 95
30 Characteristic intake curves for graded border
irrigation in the Grand Valley (Howe and
Heerman, 1970} 105
31 Application efficiency as a function of the
calculatedcut-off time (tco) for the "average"
field of 1.25 percent slope, 150 meter lengths
(50 percent soil moisture depletion, discharge
per unit width) 106
32 Application efficiency as a function of length
for level borders (USDA-SCS, Border
Irrigation, 1974) 109
33 a) Graphical representation of the linear
uniformity coefficient; b) the uniformity
coefficient as related to system performance . . 114
34 Deficiently watered area in percent 117
35 Hypothetical graph of the depth of required water
for constant application efficiencies as a
function of time for a given distribution
coefficient 118
36 Application efficiency as a function of the UCL,
and the increases in application efficiency
as a result of 5 and 10 percent increases in
the UCL as related to the deficiently watered
area 120
37 Relationship between salt pick-up and application
efficiency as a function of the quality of
applied water for the Grand Valley 122
38 Distribution characteristics of the 5.2 hectare
overhead sprinkler system 125
39 Expected application efficiencies for operation of
the overhead sprinkler system at various areal
deficit levels 126
-------
Number Page
40 Irrigation scheduling curve, at the different
application rates, for the overhead sprinkler
system 127
41 Distribution characteristics for the 4.05 hectare
side-roll wheel-move sprinkler system 129
42 Expected application efficiency for operation of
the side-roll wheel-move sprinkler system at
various areal deficit levels 130
43 Irrigation scheduling curves for the side-roll
wheel-move sprinkler system 131
44 A wetted profile develops in the root zone below
each "emitter" or "trickier". This cross-
section illustrates an idealized profile below
emitters placed on either side of a tree crop. . 136
45 Diagram of a typical automated, trickle system
"head" 137
46 A typical 6.1-hectare (15-acre) orchard layout
showing the various system components 139
47 Pressure rating curves for selected emitters and
emitter-hose products (Smith and Walker), 1976). 140
48 Idealized soil moisture cross sections under a
standard emitter and an operating aerosol
emitter. Equal flow rates from each are
assumed (Karmeli and Smith, 1977) 142
49 Cost relationships for pressurized irrigation
systems (Walker, 1978) 153
50 Cost-effectiveness function for the first level,
on-farm improvement alternatives, in the Grand
Valley (Walker, 1978) 155
XI
-------
LIST OF TABLES
Number Page
1 Final Selection of Laterals Included in Project . . 15
2 Soil Mapping Classification Index and Approximate
Percentage of Areal Extent in Grand Valley,
Colorado 30
3 Land Use Summary by Canal in the Grand Valley,
Colorado, 1969 (in hectares) 38
4 Water Right Decrees for the Grand Valley
Irrigated Area 45
5 Dimensions, Capacities and Seepage Rates of
Canals in the Grand Valley, Colorado 46
6 Field Efficiency Calculations for a Typical
Grand Valley Field 96
7 Magnitude of the On-Farm Salinity Contribution
in the Grand Valley 149
8 Cost-Effectiveness Functions for On-Farm
Improvements in the Grand Valley 154
XII
-------
LIST OF ABBREVIATIONS AND SYMBOLS
ac
AF
BTU
cal/gm
cfd
cfs
cmd
CMI
cms
degrees C or °C
degrees F or °F
ft
gra
gpm
ha
ha-m
hr
hp
in
km
kPa
Ib
Iph
1/min
acre, (43,560 ft } one acre equals 0.405
hectare
acre-foot, volume of water to cover one
acre a depth of one foot, one acre-foot
equals 0.1233 hectare-meters
British Thermal Unit
calories per gram
cubic feet per day
cubic feet per second, volume flow rate of
water, one cfs equals 0.0283 cubic meter per
second
cubic meter per day
Colorado Miner's Inch, one Colorado Miner's
Inch equals 0.74 liters per second
cubic meters per second, one cubic meter per
second equals 35.31 cfs
centigrade temperature (also called Celsius)
scale
Fahrenheit temperature scale
feet, unit of length, one foot equals 0.3048
meters
gram, 454 grams equal one pound
gallons per minute, volume flow rate of
water, one gallon per minute equals 0.631
liters per second
hectare, metric unit of area, one hectare
equals 2.471 acres
hectare-meter, volume of water to cover one
hectare to a depth of one meter, one ha-m
equals 8.108 AF
hour, 60 minutes
horsepower, one horsepower equals 7.460 x
10~^ erg/sec
inch, one inch equals 2.54 centimeters
kilometer, metric unit of length, one
kilometer equals 0.621 miles
kilopascal, metric unit of pressure, 6.9
kilopascal equals one psi
pound (mass)
liters per hour, volume flow rate of water
liters per minute, volume flow rate of
water
Xlll
-------
1/s — liters per second, volume flow rate of water
m — meter
m3/s — cubic meters per second, volume flow rate of
water
me/1 — milliequivalents per liter
mg/1 — milligrams per liter, equal to one ppm
mi — mile, one mile equals 1.609 kilometers
mm — millimeter
mph — miles per hour, velocity
N/m — Newton per square meter, unit of pressure,
one N/m^ equals one Pascal (6.9 kPa equals
one k)
ppm — parts per million
psi — pounds force per square inch, unit of
pressure
sec — seconds, time
UCC — Christiansen's Uniformity Coefficient
(Christiansen, 1942)
UCH — Hawaiian Sugar Planters Association
Uniformity Coefficient (Hart, 1961)
UCL — Linear Uniformity Coefficient (Karmeli, 1977)
yd — yard, unit of length, one yard equals 0.9144
meters
yd3 — cubic yard, unit of volume, one cubic yard
equals 0.7646 cubic meters
xiv
-------
ACKNOWLEDGMENTS
The authors are deeply indebted to the many individuals who
carefully attended to the daily details of the field data
collection and the laboratory analyses. These people include
Ms. Barbara Mancuso, Mr. John Bargsten, Mr. Forrest Binder,
Mr. Gregory Sharpe, Mr. David Flower, Mr. Douglas Ely,
Mr. Patrick O'Connor, Mr. Larry Rumburg, Mr. Richard L. Aust and
Mr. Charles W. Binder.
The cooperation of all the landowners and irrigators on the
project who contributed labor, shared costs and expended much
effort for the construction and operation of the lateral and on-
farm improvements is greatly appreciated. Their willingness to
participate in this investigation is undoubtedly one of the
major factors for the degree of improvement which was achieved.
The cooperation and assistance of the Grand Junction
Drainage District was greatly appreciated and special thanks are
due to Mr. Howard K. Hiest, Mr. Capper Alexander, Mr. Wesley
Land, Mr. Bill Huber of the Board of Directors, Mr. Charles
Tilton, Superintendent and their staff. Thanks also go to
Mr. Charles Bowman, Superintendent of the Mesa County Road
Department and his staff for their assistance in the project.
The efforts and assistance of Mr. Robert Henderson and the
Directors of the Grand Valley Irrigation Company, Mr. William
Klapwyk and the Directors of the Grand Valley Water Users
Association and the other irrigation companies in the area were
extremely helpful. A complete list of all other agencies and
Grand Valley businesses who contributed to this project would
take several pages and, therefore, a collective and heartfelt
thanks goes to each of them.
The irrigation scheduling computer service was provided by
the Bureau of Reclamation, USDI, Grand Junction Office. We
gratefully recognize Mr. Bill McCleneghan, Mr. Elaine Richards,
Mr. Ray White and Mr. Jack Ticen for their assistance.
Special acknowledgment goes to Mrs. Susan Kuehl and
Ms. Sue Eastman for typing the many drafts of this report.
Finally, the efforts and advice given by the EPA Project
Officer, Dr. James P. Law, Jr., have been extremely helpful in
the successful pursuit of this project. He has generously given
of his time to cooperatively achieve the goals of the project.
xv
-------
SECTION 1
INTRODUCTION
PROBLEM STATEMENT
Approximately 10 million metric tons (11 million tons) of
salts are delivered each year in the water supply serving the
Lower Colorado River Basin (Figure 1). 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 concen-
trations necessitate treatment of water for both municipal and
industrial uses throughout the Lower Basin. In fact, at times,
concentrations approach the tolerance of many high-value crops
such as citrus, requiring the use of excessive quantities of
water for leaching and expensive water management programs.
This situation is expected to become even more serious,
especially when the many planned upstream water development
projects are constructed. Thus, a program for reduction of
mineral pollution is urgently needed in order to protect
existing water users from quality degradation during low flow
periods and to prevent the serious restriction of future basin-
wide economic development. Due to the relatively large salinity
contribution from agriculture, it is obviously one sector in
which to begin implementation of technologies that will reduce
the salt loading from these areas.
Since the Grand Valley of Colorado is the largest
contributor of salts per hectare of irrigated land in the Upper
Colorado River Basin, it was a logical place to begin investi-
gating salinity control alternatives. The irrigated portions of
the Grand Valley have an estimated salinity contribution
averaging from 450,000 to 800,000 metric tons of salt annually
to the Colorado River. These salts are a direct result of the
deep percolation from irrigated farm lands and seepage from
unlined canal and lateral water delivery systems. Examination
of district and canal records show that this contribution has
been fairly constant over the past sixty years. Elkin (1976)
has estimated that the additional natural salinity contributions
from the area has an upward limit of about 10 percent of the
-------
I
I
f\)
/Lake
(Mead
$&
Lees /
Ferry \
'.Ariz, ^
%
Figure 1. The Colorado River Basin.
-------
Upper Colorado River
Basin
Average Salt Load,Metric tons/day
June 1965—May 1966
Natural Point Sourcti
and W«ll»
Irrigated Agriculture
37%
(8750 T/d)
Net Runoff
52 %
(72454 T/d)
Municipal
(324 T/d) and
Upper Main Stem
Subbatin
Relative Magnitude of Salinity
Sources by River Basins of the
Colorado River
Grand Valley Area „
„ _. /Other
18 % Area*
Green River
Subbatin
Lower Main Stem
Subbaiin
San Juan River
Subbatin
Lower Colorado River
Basin
Average Salt Load,Metric tons /day
November 1963-October 1964
Net
Upper Colorado
River Basin
Inflow
72%
(6920 T/d)
Municipal
and
Induttrial
Irrigated Agriculture
Figure 2. Relative magnitude and sources of salt in the
Colorado River Basin (USDI, FWPCA, 1970, Appendix A)
-------
salt loading from Grand Valley/ or a maximum of about 80,000
metric tons annually.
The introduction of water from these surface sources
dissolves the salt contained in the saline soils and marine
shales of the area. When the water reaches the shallow ground-
water reservoir, the slight hydraulic gradient causes some
groundwater to be displaced into the river. This displaced
water has usually had sufficient time to reach chemical equi-
librium with the salt concentration in the shale and/or cobble
aquifer, which is approximately 8,700 mg/1 total dissolved
solids (TDS).
The water from seepage and deep percolation tends to reach
chemical saturation with the very abundant natural sources of
soluble gypsum and calcite that are present in the soils and
geologic substrata. The concentration of salts appears to be
controlled by geologic conditions and is independent of seepage
rates (Duke et al., 1976). if the amount of groundwater is
reduced through improved on-farm water management practices, as
well as canal and lateral lining, the concentrations of other
salts such as sodium chloride will rise slightly, but not enough
to compensate for the reduction in flows. Therefore, the net
contribution to salt loading is essentially directly proportional
to the reduction in groundwater flows (Skogerboe, McWhorter, and
Ayars, 1978b).
PREVIOUS INVESTIGATIONS
Canal and lateral seepage can be greatly reduced by lining
the delivery system. The Grand Valley Salinity Control Demon-
stration Project was initiated in 1968 to study the effectiveness
of linings as a salinity control measure. Since then, additional
studies have been conducted on field drainage and scientific
irrigation scheduling as viable salinity reduction technologies.
In 1967, the irrigation companies of the Grand Valley
became aware of the potential financial burden which could be
placed upon the Valley's water users by salinity damages down-
stream, especially if they were forced to comply with salinity
control measures at their own expense. Consequently, they began
efforts to initiate action based on the concept that abatement
of the salinity problem would have state, regional, national,
and international benefits. Furthermore, it was claimed "that
development of irrigation within the Grand Valley was done
without intent of damage to others, and was done within existing
laws and regulations and, therefore, the Valley's water users
should not be penalized for their actions by laws and regulations
enacted after the fact." With this in mind, the irrigation
companies formed a cooperative organization called the Grand
Valley Water Purification Project, Inc. and petitioned the
-------
Federal Water Quality Administration for 70 percent matching
funds to demonstrate canal lining as a salinity control measure.
This money was forthcoming, and in 1968 the Agricultural Engi-
neering Department of Colorado State University was contracted to
perform the technical evaluation regarding the effectiveness of
canal lining in reducing the Grand Valley's salt load to the
Colorado River.
The particular demonstration area was selected because it
contained lands served by the majority of irrigation companies in
the Valley, and their cooperation after the project would be
needed to implement the proposed changes on a valley-wide scale.
The location of the demonstration area is shown in Figure 3, and
a close up of the area is shown in Figure 4. After completion of
this initial project, the canal companies reorganized into the
Grand Valley Canal Systems, Inc. and remained active. Presently,
their main purpose is to collectively represent the irrigation
interests of the Valley.
Canal and Lateral Lining
The present demonstration area is one of three areas of
study included in the initial investigation. The initial phase
of the project involved the determination of the seepage rates
from the canals and laterals in the three test areas. The
ponding technique was employed to assure reliability of the
results.
The results of this study indicated that canal and lateral
lining in the tes-t area reduced salt inflows to the Colorado
River by about 4,260 metric tons (4,700 tons) annually. The bulk
of this reduction is attributable to the canal linings, but the
greater importance of lateral linings is clearly indicated. The
length of laterals (600 kilometers), plus the total head ditches
(1,640 kilometers), is about eight times greater than the length
of canals (286 kilometers) in the Valley. The economic benefits
to the Lower Basin water users alone exceeded the costs ($350,000
construction plus $70,000 administration) of this project.
Consequently, it was concluded that conveyance lining in areas
such as the Grand Valley, where salt loadings reach 18 metric
tons or more per irrigated hectare, are a feasible salinity
control measure. The local benefits accrued from reduced main-
tenance, .improved land value, and other factors add to the
feasibility of conveyance linings as a salinity management
alternative. The results of this project are reported in detail
in "Evaluation of Canal Lining for Salinity Control in Grand
Valley," Report EPA-R2-72-047 (Skogerboe and Walker, 1972).
Irrigation Scheduling
An irrigation scheduling project was initiated in 1972 in
the demonstration area as a salinity control measure. Since a
-------
• -'..
Grand Valley Salinity
Control Project
Boundary of Irrigated
Area
Figure 3. Location of Grand Valley Salinity Control Demonstration Project.
-------
Stub Ditch
20
Canals
Drains
Boundary
Section Number
Government
Highline
Canal
Price Ditch
Scale I Kilometer
Grand Valley Canal
Seal* I Mile
Mesa County
Ditch
Colorado River
Figure 4. Grand Valley Salinity Control Demonstration Project.
-------
large fraction of the water passing through the local soils
returns to the river as deep percolation resulting from over-
irrigation, measures aimed at improving irrigation efficiencies
promise a high potential for controlling salinity. Among all the
methods for achieving higher water use efficiencies on the farm,
irrigation scheduling is one of the most promising and least
expensive.
The results of this demonstration project showed that
irrigation scheduling is a necessary tool, but not in itself
sufficient for achieving improved irrigation efficiencies. The
real strides in reducing the salt pickup caused by overirrigation
will come from the employment of irrigation scheduling in con-
junction with other improved on-farm irrigation practices.
Excessive water supplies, the necessity for rehabilitating the
irrigation system (particularly the laterals), and local resist-
ance to change, preclude higher levels of water management during
successive irrigations. To overcome these limitations, irriga-
tion scheduling must be accompanied by flow measurement at all
the major lateral division points and farm inlets. In addition,
it is necessary for the canal companies and irrigation districts
to assume an expanded role in delivery of the water, in accepting
more responsibility for lateral deliveries, and in changing to a
demand type system. More details on this project can be obtained
in the EPA Report entitled "Evaluation of Irrigation Scheduling
for Salinity Control in the Grand Valley" (Skogerboe, Walker,
Taylor and Bennett, 1974b).
Drainage
Part of the initial demonstration project on canal linings
included a portion on drainage. A total of $20,000 was spent in
this initial project to tile some open drains and concrete slip-
form some other open drains. This was done to correct two small
surface problems in the area. The field data indicated that most
of the open drains in the area were performing as intended and
were not seeping water back into the groundwater. However, there
still existed a need to evaluate the effectiveness of field drain-
age as a salinity control measure. This was undertaken in 1972.
Drainage studies were not new in the Grand Valley. In-fact,
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 to have low permeabilities.
At that time, the future development of the Bureau of
Reclamation's "Grand Valley Project" loomed as a severe threat to
the low lying lands between it and the Colorado River. In answer
to the apparent drainage needs, the necessary solutions were
clearly set forth but never fully implemented because of the
large capital investment required. However, the citizens of
8
-------
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 local trouble spots. All of these
efforts barely contained the rise in water tables, and today,
more than fifty years later, the local conditions remain
essentially unchanged.
The construction of open drains has played an important role
in the Grand Valley. These drains serve as outlets for the tile
interceptor drainage systems. They also intercept and convey
tailwater 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.
This study was undertaken with the history of local drainage
well in mind, but for different purposes, to skim water from the
top of the water table before it reaches chemical equilibrium
with the highly saline soils and groundwater in the cobble
aquifer, and to demonstrate to local farmers the benefits in
increased crop production by improved field drainage resulting in
lower soil salinity levels by permitting more effective leaching.
Three farms were selected for field drainage investigations
during the 1972 irrigation season. The studies showed that the
drainage problems on two of the farms could be alleviated by
improved on-farm water management practices, particularly by
increasing irrigation efficiency during the early part of the
season which would sufficiently reduce deep percolation losses
and would keep the groundwater level at a satisfactory depth
below the ground surface to allow good crop production.
The field drainage effluent was approximately 3000 mg/1 less
saline than the concentration of the waters in the cobble aquifer,
This significantly demonstrated that the field drainage will
"skim" the water before it can reach the higher concentrations.
Although it is very expensive ($4225/hectare or $1960/acre),
field drainage can be an effective salinity control measure.
In viewing the results of this study, it is obvious that
field drainage is a curative rather than preventative measure.
High costs of such programs illustrate the need of first
minimizing the flows passing through the root zone or seeping
from canals and laterals. The smaller amount of water then
entering the groundwater could be effectively removed by drainage
systems and/or wells located at selected locations. Field
drainage as it pertains to objectives of salinity control is a
remedy which must be considered but will probably not be imple-
mented as a salinity control measure in the Valley. This project
was discussed in much more detail in the EPA Report "Evaluation
of Drainage for Salinity Control in Grand Valley" (Skogerboe
et al.f 1974a).
9
-------
PURPOSE
The costs of salinity control to sufficiently compensate for
future water resource developments in a region like the Colorado
River Basin will be high. Savings achieved through the implemen-
tation of the most cost-effective alternatives can be substantial,
This project was designed to develop and demonstrate cost-
effectiveness relationships for salinity control in the Grand
Valley of western Colorado.
Economically feasible means of controlling the 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 is necessary
to describe the interrelationships which exist among the alterna-
tives. 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 were not mutually exclusive, then an "optimal"
salinity control strategy would consist of a combination of
several alternatives. The respective composition of such a
strategy would depend on the relative magnitude of each hydro-
logic segment in an irrigated area. Thus, an important step in
solving salinity problems was to investigate the nature of
improvements incorporating several alternatives, and assessing
the impact of a "package" of salinity control measures.
The most significant aspect of this particular demonstration
project is the employment of a salinity control technology
"package", rather than a single control measure. Experience in
the Grand Valley has shown that the most significant progress is
made when the gamut of questions can be answered regarding the
interrelationships between water management and agricultural
production. Thus, the concept of a technology package, along
with an understanding of the "system" including other agricul-
tural inputs, provides the necessary base for providing sound
advice to the farmer. This in turn facilitates the development
of credibility and consequently farmer acceptance.
OBJECTIVES
The primary objective of this demonstration project was to
show the advantages of implementing technological improvements
within the lateral subsystems, in reducing the salt load entering
the Colorado River. As defined in this project, the lateral
subsystem begins at the canal turnout and includes all of the
water conveyance channels below the turnout and the farm lands
served by the lateral water supply. Although major emphasis was
upon on-farm improvements, considerable improvements in the water
delivery conveyances, improvements in lowering high-water tables
10
-------
(drainage), and tailwater removal improvements were also
required.
This project utilized each of the salinity control measures
previously evaluated in Grand Valley with the additional use of
various irrigation methods to demonstrate on-farm salinity
control measures. No single measure (except a desalination
plant) will adequately alleviate the salt load from an irrigated
area. Demonstrating the complete package of salinity control
measures is a "first", which can also 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 objectives of this demonstration project are summarized
below:
A. Utilize salinity control technology to demonstrate the
complete package of salinity control measures for nine
laterals, including a preevaluation and postevaluation
of the following control measures:
1. Utilization of existing canal lining technology
developed in the Grand Valley;
2. Utilization of irrigation scheduling technology
presently in use in the Grand Valley;
3. Evaluation of salinity control benefits resulting
from various on-farm irrigation methods as a part
of this demonstration project;
4. Utilization of drainage technology previously
evaluated in the Grand Valley; and
5. Utilization of the concurrent research project,
"Irrigation Practices, Return Flow Salinity, and
Crop Yields," to predict the chemical quality
changes in the Colorado River resulting from this
demonstration project.
B. Determine the cost-effectiveness of each salinity
control measure, various combinations of salinity
control measures, and the complete package of salinity
control technology for this demonstration project.
C. Conduct a two-day highly publicized field days.
D. Determine the best practicable salinity control
technology for the Grand Valley, including valley-wide
cost-effectiveness.
11
-------
E. Analyze effectiveness of local administrative controls
in implementing salinity control technology.
1. Tailwater runoff control
2. Permit system
a. Individual farm
b. Lateral
c. Canal (Irrigation Co.)
d. Entire Valley
3. Influent standards
a. Farm inlet
b. Lateral turnout
c. Canal diversion
F. Delineate the essential elements of an educational
program to transfer this information to other farmers
in the Grand Valley, along with farmers in other
irrigated areas of the Colorado River Basin.
This report covers only Objective A3. The preceding
report, "Implementation of Agricultural Salinity Control Tech-
nology in Grand Valley" (Evans et al., 1978) covers all the other
objectives except D. The final report of this research program,
"Best Management Practices for Salinity Control in Grand Valley"
(Walker et al., 1978), is devoted to satisfying Objective D.
RESEARCH APPROACH
The principal study area in the Grand Valley, which has 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 in this
demonstration project. The advantage in continuing to utilize
this study area is that the hydrology is already known. In
addition, there has been considerable expenditure of funds in
both equipment and personnel for instrumenting this particular
demonstration area. The wealth of available information provides
a strong basis for evaluating the effectiveness of salinity
control measures.
With all the available knowledge regarding the study area, a
lateral including the associated lands served by the lateral
water supply can be used as a subsystem for evaluating the
salinity reduction in the Colorado River resulting from the
implementation of a salinity control technology package.
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
12
-------
selection, as shown in Figure 5, had two laterals under the
Highline Canal, one under the Price Ditch, three under the Grand
Valley Canal, and three under the Mesa County Ditch. Figure 5
also shows the locations of the previous canal lining, irrigation
scheduling and drainage investigations. It should be pointed out
that the lands served by the Highline Canal in the demonstration
area are served under carriage contract with the Mesa County
Irrigation District (Stub Ditch) and the Palisade Irrigation
District (Price Ditch). Therefore, all the irrigation entities
in the demonstration area are 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 hydrologic knowledge already gained in
this demonstration area allows routine surface water and ground-
water monitoring to evaluate the overall effectiveness of the
salinity control technology package.
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 1. The field
data collection program provided a basis for the design of
irrigation and drainage facilities and sufficient data to allow
predictions of salinity benefits resulting from each specific
salinity control measure. Although the postevaluation included
the monitoring of water and salts entering and leaving the
demonstration area, the primary emphasis was the on-site evalua-
tion of each specific salinity control measure. The on-site
evaluation was then compared with the results of the total
demonstration area hydrosalinity monitoring program.
The selection of a lateral as a subsystem, rather than an
individual farm, had a tremendous advantage of control 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.
Considerable experience has been gained in improving and
"tuning up" the existing irrigation methods while evaluating
irrigation scheduling as a salinity control measure in the Grand
Valley. In addition, more advanced irrigation methods have 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.
A two-day "Field Days" was conducted during the third year
of this project in the month of August. This event was primarily
directed towards the growers in the Grand Valley and secondly to
irrigation leaders (mostly growers) throughout the Upper Colorado
River Basin. Some State and Federal agency personnel also
attended. This was coupled with an irrigation equipment show
13
-------
Legend
Water Supply
Grand Valley Canal
t •
,i.
V///////////A Land Under Study Lateral
t:::-:^-:-'-:>:':•:::•:] Previous Drainage Study
Irrigation Scheduling Project
Hydrologic Boundary
Canal or Ditch (No Improvements)
Drain or Wash
Trapezoidal Concrete
Slip-form Lining
Gunite Lining
E Rd
Gunite,Downhill
Bank Only GV 160
Stub Ditch
•
overnment
Highline
Canal
/ Price Ditch
i
Scale I Kilometer
Figure 5.
Map showing the location of the nine selected lateral subsystems
incorporated in the project, and the locations of the previous
canal linings, irrigation scheduling and drainage investigations.
-------
TABLE 1. FINAL SELECTION OF LATERALS INCLUDED IN PROJECT
Lateral
Identification
HL C
HLE^
PD 177-' -/
GV 92
W95l'l'
GV 160
MC 3
MC 10^/
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
No.of
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.
15
-------
and was cosponsored by the Colorado State University Cooperative
Extension Service.
The concurrent EPA research project, "Irrigation Practices,
Return Flow Salinity, and Crop Yields," which was also conducted
in the Grand Valley, provided necessary input for developing the
cost-effectiveness of each salinity control measure. In addition,
the results from this same project provided valuable information
regarding increased crop yields that can be expected from
improved water management practices. The combined results of
this research project and the demonstration project are extremely
important in establishing the benefits to be derived from
implementing a salinity control technology package. The detailed
results of this project can be found in the EPA reports entitled,
"Irrigation Practices and Return Flow Salinity in Grand Valley"
(Skogerboe et al.r 1978b) and "Potential Effects of Irrigation
Practices on Crop Yields in Grand Valley" (Skogerboe et al.,
1978a). The combined results of the two projects are incorpo-
rated in the EPA report "Best Management Practices for Salinity
Control in Grand Valley."
Although each irrigated area is somewhat different, the
knowledge already gained in the Grand Valley can be utilized in
conjunction with existing and secondary sources of data for other
areas, particularly irrigated areas in the Upper Colorado River
Basin, to formulate plans and priorities for implementing
salinity control technology in such areas.
16
-------
SECTION 2
CONCLUSIONS
The cost-effectiveness associated with each salinity control
alternative is the basis for determining the formulation of an
implementation policy. Studies reported in the technical litera-
ture indicate that the salinity damages in the Lower Colorado
River Basin range from $150 to $350 (Section 12) 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. The evalua-
tion of the salinity control benefits resulting from various on-
farm irrigation methods yielded the following conclusions:
1) 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 Modified 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 weekly 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
estimating seasonal values, but was not better at
approximating the seasonal distribution of
evapotranspiration.
2} Irrigation scheduling by itself is not a significant
salinity control alternative, but should be part of any
strategy for improved water management in order to
maximize the effectiveness of physical improvements.
3) Irrigation 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
17
-------
the time required to refill the "least watered" root
zone areas. In sprinkler irrigation, the least watered
or "critical" areas would be the diagonal distance
between two sprinklers on adjacent laterals; whereas
for surface irrigated systems, it is at the lower end
of the field.
4) Furrow irrigation is the predominant method of water
application in the Grand Valley. Existing application
efficiencies [(available root zone storage/applied
water) x 100] is about 64 percent. Strict adherence to
the scheduling philosophy outlined in (3) 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.
5) 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.
6) Level borders offer a large potential for reducing salt
loading if problems with soil crusting can be controlled.
Also, the level borders require a very high level of
management capability, and would be quite adaptable to
automation.
7) 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
management of the system.
8) 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 systems, trickier irrigation has a
much poorer cost-effectiveness than properly managed
surface irrigation systems.
18
-------
9) Since sprinkler and trickier irrigation methods are not
controlled by soil properties, changing to these
systems potentially would have a very large impact on
reducing the salt loading from the early season irriga-
tions. These early irrigations are responsible for
more than 50 percent of the total annual salt load for
irrigation return flows in the Grand Valley.
10} A comparison of the cost-effectiveness relationships of
the various irrigation system improvements indicates
that head ditch linings, gated pipe, and/or automated
cutback 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 improvement 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.
11) 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.
12) Installation of potentially efficient irrigation
systems will not by itself reduce salt loading from
irrigation return flows. These systems must be
properly managed to realize any improvement over
existing conditions in the Grand Valley. Likewise,
much more efficient management and control of existing
irrigation systems in the Grand Valley would result in
significant salt load reductions. For this reason,
successful implementation requires large-scale exten-
sion type programs to provide necessary technical
assistance and a strong interaction with farmers.
19
-------
SECTION 3
RECOMMENDATIONS
As a result of this research project, there are several
recommendations which can be made concerning the implementation
of a "total" salinity control program and the evaluation of
salinity control benefits resulting from various on-farm irriga-
tion methods.
1) The lateral improvement program and the on-farm program
should not be two separate programs/ but a single
program which plans, constructs, and operates a combi-
nation of improvements moving from one lateral to the
next.
2) An effective plan of physical improvements must be
developed which will result in improved water manage-
ment for increasing agricultural productivity in the
Grand Valley, while reducing the salt load in the
Colorado River.
3) Irrigation scheduling in the Grand Valley should be
included in any plan to implement on-farm irrigation
system improvements for salinity control. The primary
objective should be to develop operational criteria for
determining the length of each irrigation set and flow
rates which just meets the root zone storage require-
ments in the least watered areas of a field. Irriga-
tors should be advised of the time water should be
applied to their fields for a range of days over which
the fields might be irrigated. Predicting the exact
dates of subsequent irrigations should be of secondary
importance.
4) Existing salinity control plans should be reevaluated
in terms of the on-farm potential. Reducing field head
ditch seepage with slip form concrete lining or gated
pipe should be considered a salinity control alterna-
tive second only to lateral linings in importance.
Automated cut-back furrow irrigation should be con-
sidered as equal in cost-effectiveness with simple head
ditch linings, but it has a higher potential for total
salt load reduction.
20
-------
5) Sprinkler and trickle irrigation should be considered
when the control of on-farm salinity is to be reduced
as much as possible. However, the marginal costs of
these possible improvements exceed the costs of lining
the Government Highline Canal. Therefore, the level of
on-farm improvements needs to be evaluated in terms of
other alternatives.
6) The relative impact of on-farm improvement in reducing
the salinity of the Colorado River ought to be con-
sidered throughout the Basin before plans are finalized
for the Grand Valley. In other words, on-farm improve-
ments 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.
7) The ultimate level of salinity control decided upon for
the Grand Valley should be evaluated on 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 at least in a general
sense to other irrigated areas in the Upper Colorado
River Basin.
8) 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.
9) Adequate numbers of technical assistance personnel
should be available to help the irrigators develop
proficiency with their system and develop a higher
level of water management.
10) Given the levels of technical assistance personnel
needed to work with farmers, and the current shortage
of trained manpower with on-farm water management
experience, special training courses should be
developed.
11) Once the physical facilities are complete, a program of
"scientific" irrigation scheduling should be used to
maximize the effectiveness of the physical improvements.
12) The success of any salinity control program rests
finally with the degree of participation by the farmers
themselves. Farmers who have made exceptional progress
21
-------
in improving their on-farm water management practices
should be given special recognition.
13) 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.
22
-------
SECTION 4
THE GRAND VALLEY
LOCATION
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 popula-
tion center of the Valley. The area was illustrated in 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 foot) high Grand Mesa lies to the north and east,
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 canyonlands of
the Colorado Plateau.
Within the Grand Valley, the irrigated lands have 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.
POPULATION
The majority of the population of Mesa County reside in the
Grand Valley near and within the city limits of Grand Junction.
23
-------
In 1970 the population of the city of Grand Junction was 20,170,
which is 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
population 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 still is 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.
CLIMATE
The Grand Valley area enjoys a moderate year-around climate
which is influenced more by the mountain ranges in the Upper
Colorado River Basin than by the latitude. The movement of air
masses is affected by the mountain ranges so that the high
elevations are relatively wet and cool, whereas the low plateaus
and valleys are much drier and subject to wide temperature
ranges. The characteristic climate in the lower altitudes is hot
and dry summers and cool winters.
The Grand Valley has a climate common to all of the
semi-arid Colorado River Basin. Most of the precipitation to the
Valley is provided from the Pacific Ocean and the Gulf of Mexico,
whose respective shores are 1,200 and 1,800 kilometers (750 and
1,100 miles) away. During the period from October to April,
Pacific moisture is predominant, but the late spring and summer
months receive moisture from the Gulf of Mexico. The advancing
air masses are forced to high altitudes and lose much of their
moisture either before entering the area (Gulf of Mexico fronts)
or after leaving the area (Pacific fronts).
The Grand Valley receives an average annual precipitation of
only 211 mm (8.29 inches) and practically all the irrigation and
potable water supplies come from the nearby high mountain snow-
packs. The monthly distribution of precipitation and temperature
for Grand Junction is shown in Figure 6. The climate is marked
by a wide seasonal range, but sudden or severe weather changes
are infrequent due primarily to the high ring of mountains around
the Valley.
24
-------
Grand Junction Colo.
Alt. 4843 ft. - 1476 meters
c
recipitation
a.
—
0 '•'••:•;.
O
0
a>
(O
c
8.29" Annual 210.57mm Annual -30
,,,, m ,,.-:-. II Hj .,,,, - 20
11 11 II II iSS III 11 |l || 1| 18 ~ I0
i 190 Frost Free Days ,
Apr. 16 Oct. 23
E
E
recipitation
a.
u.
o
80-
60-
52.5 °F Annual
a>
3
O
| 40-
a>
II.4°C Annual
- 30
- 20
o
e
10 =
o
a.
£
0)
- 0
c
o
a>
20-
a
-10 §
JFMAMJJASOND
Month
20
Figure 6. Normal precipitation and temperature
at Grand Junction, Colorado (U.S.
Department of Commerce, 1968).
25
-------
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).
GEOLOGY
The plateaus and mountains in the Colorado River Basin are
the products of a series of land masses deeply eroded by wind and
water. However, long before the earth movements which created
the uplifted land masses, the region was the scene of alternate
encroachment and retreat of great inland seas. The sediment rock
formations underlying large portions of the basin are the result
of material accumulated at the bottom of these seas. In the
Grand Valley, the primary geologic formation resulting from this
action is the Mancos Shale.
Mancos Shale is a very thick sequence of drab, gray, fissle,
late Cretaceous marine shale 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. A general
geologic cross-section of the Valley can be seen in Figure 7.
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 small
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.
Due to the compactness of the clay and silt particles making
up the shale, the formation is not considered water-bearing at
depth. However, the weathered zone near the surface does
transmit small quantities of water along joints, fractures, and
26
-------
GRAND MESA
UNCOMPAHGRE UPLIFT
AVA «xgi CENOZOIC
:yy- TERTIARY
(EOCENE)
Y_ (PALEOCENE)
MESOZOIC
(CRETACEOUS)
ARCHEZOIC
Figure 7. General geologic cross section of the Grand Valley (USDA, 1955)
-------
open bedding planes. In this zone, the percolating water, which
primarily originates from the overirrigation of cropland,
dissolves the salts directly out of the shale. The soils of the
Valley are also quite saline because they have been derived from
the Mancos Shale.
A gravel and cobble layer has been found under some parts of
the irrigated areas in the Grand Valley. It is believed to be
ancient stream deposits of the Colorado River, laid down in
recent geologic time, and serves as an aquifer for transmitting
highly saline groundwater to the river.
SOILS
The physical features describing the project area are
similar to the entire Grand Valley. The soils in the Valley were
classified by the Soil Conservation Service (SCS) in cooperation
with the Colorado Agricultural Experiment Station in 1955.
Using these data, a soil classification map of the Grand Valley's
irrigated area is shown in Figure 8. The soil classification
symbols, along with a general description of each symbol and the
relative percent of areal extent, are tabulated in Table 2.
The dry desert climate of the area has restricted the growth
of natural vegetation, and because of the lack of organic matter,
the soils are very low in nitrogen content. The natural inorganic
content is high in lime carbonate, gypsum, sodium, potassium,
magnesium and other calcium salts. With the addition of irriga-
tion, some locations have experienced high salt concentrations
with a resulting decrease in crop productivity.
Although natural phosphate exists in the soils, it becomes
available too slowly for use by cultivated crops, and fertilizer
applications greatly aid yields. Other minor elements such as
iron are generally available for most crops except in those areas
where drainage is inadequate. The soils in the area are of
relatively recent origin, and consequently, they contain no
definite concentration of lime or clay in the subsoil horizons as
would be expected in weathered soils. Some areas in the Valley
have limited farming use because of poor internal drainage, which
results in waterlogging and salt accumulations.
Lying on top of the Mancos Shale and below the alluvial
soils is a large cobble aquifer extending north from the river to
about midway up the irrigated area for most of the length of the
Valley. The approximate areal extent of this aquifer can be seen
in Figure 9. The importance of this aquifer with respect to the
drainage problems of the area has been demonstrated by a coopera-
tive study in 1951 between the Colorado Experiment Station in
conjunction with the United States Department of Agriculture,
Agricultural Research Service (USDA-ARS) which evaluated the
28
-------
I '
\a
LEGEND
I' | Billings Silty Clays
Chipeta - Persayo Loams
I I Chipeta Silly Cloy Loam
Fruita and Ravola Loams
Fruita Loams
Genola Loams
Green River Loams
Hinman Cloy
Mack Clay Loams
Mayfield Shaly Clay Loam
Mesa Clay Loams
Naples Loams
I'.'.V.v'J Persayo-Chipeta Silty Clay Loam
Ravola Loams
Redlunds Loams
Redlands and Thoroughfare Soils
I Riverwosh
t-iiKS Rough Broken Land:Mesa, Chipeta,8 Persayo Soils
~] Rough Gullied Land
V/ifilpA Thoroughfare Fine Sandy Loam
Figure 8. Soils map of irrigated lands in Grand Valley (from USDA, 1955)
-------
TABLE 2. SOIL MAPPING CLASSIFICATION INDEX AND APPROXIMATE
PERCENTAGE OF AREAL EXTENT IN GRAND VALLEY, COLORADO
Map Approximate
Symbol Soil Type Percent
Be Billings silty clay loam, 0 to 2 percent slopes 25.4
Bd Billings silty clay loam, 2 to 5 percent slopes .6
Ba Billings silty clay, 0 to 2 percent slopes 2.7
Bb Billings silty clay, 2 to 5 percent slopes .1
Be Billings silty clay, moderately deep over Green River .7
soil material, 0 to 2 percent slopes
Cd Chipeta silty clay loam, 0 to 2 percent slopes 2.4
Ce Chipeta silty clay loam, 2 to 5 percent slopes 2.8
Ca Chipeta-Persayo shaly loams, 2 to 5 percent slopes .8
Cb Chipeta-Persayo shaly loams, 5 to 10 percent slopes 1.9
Cc Chipeta-Persayo silty clay loams, 5 to 10 percent slopes 1.5
Fe Fruita clay loam, 0 to 2 percent slopes 2.2
Ff Fruita clay loam, 2 to 5 percent slopes .4
Fg Fruita clay loam, moderately deep, 0 to 2 percent slopes .6
Fl Fruita clay loam, moderately deep, 2 to 5 percent slopes 1.1
Fi Fruita gravelly clay loam, 2 to 5 percent slopes .6
Fk Fruita gravelly clay loam, 0 to 2 percent slopes .1
Fro Fruita gravelly clay loam, 5 to 10 percent slopes .1
Fn Fruita gravelly clay Loam, moderately deep, 2 to 5 .5
percent slopes
Fo Fruita gravelly clay loam, moderately deep, 5 to 10 .1
percent slopes
Fp Fruita very fine sandy loam, 0 to 2 percent slopes 1.1
Fr Fruita very fine sandv loam, 2 to 5 percent slopes .5
Fs Fruita very fine sandy loam, moderately deep, 0 to 2 .5
percent slopes
Ft Fruita very fine sandy loam, moderately deep, 2 to 5 1.0
percent slopes
Fu Fruita very fine sandy loam, moderately deep, 5 to 10 .1
percent slopes
Fc Fruita and Ravola loams, 2 to 5 percent slopes 1.2
Fd Fruita and Ravola loams, moderately deep, 2 to 5 .3
percent slopes
Fa Fruita and Ravola gravelly loams, 5 to 10 percent .7
slopes
Fb Fruita and Ravola gravelly loams, 20 to 40 percent .1
slopes
Ga Genola clay loam, 0 to 2 percent slopes .2
Gb Genola clay loam, 2 to 5 percent slopes 1
Gc Genola clay loam, deep over Hinman clay, 0 to 2 .5
percent slopes
Gd Genola fine sandy loam, deep over gravel, 0 to 2 *
percent slopes
Gf Genola loam, 2 to 5 percent slopes .2
Gg Genola very fine sandy loam, deep over gravel, 0 to .1
2 percent slopes
Gh Green River clay loam, deep over gravel, 0 to 2 ;1
percent slopes
Gk Green River fine sandy loam, deep over gravel, 0 to 2 .4
percent slopes
(Table 2 continued on following page)
30
-------
TABLE 2 (Continued)
Map
Symbol
Soil Type
Approximate
Percent
Gl
Gm
Ha
Hb
He
Ma
Mb
Me
Md
Me
Mf
Mg
Mh
Na
Nb
Nc
Pa
Pb
Ra
Rb
Rf
Rg
Re
Rd
Re
Rk
Rh
Rl
Rn
Rm
Ro
Rr
Rp
Rs
Tb
Ta
Tc
Green River silty clay loam, deep over gravel, 0 to
2 percent slopes
Green River very fine sandy loam, deep over gravel,
0 to 2 percent slopes
Hinman clay, 0 to 1 percent slopes
Hinman clay loam, 0 to 2 percent slopes
Hinman clay loam, 2 to 5 percent slopes
Mack clay loam, 0 to 2 percent slopes
Mayfield shaly clay loam, 2 to 5 percent slopes
Mesa clay loam, 0 to 2 percent slopes
Mesa clay loam, 2 to 5 percent slopes
Mesa gravelly clay loam, 2 to 5 percent slopes
Mesa gravelly clay loam, 5 to 10 percent slopes
Mesa gravelly clay loam, moderately deep, 2 to 5 percent
slopes
Mesa gravelly clay loam, moderately deep, 5 to 10
percent slopes
Naples clay loam, 0 to 2 percent slopes
Naples fine sandy Joam, 0 to 2 percent slopes
Navajo silty clay, 0 to 2 percent slopes
Persayo-Chipeta silty clay loams, 0 to 2 percent slopes
Persayo-Chipeta silty clay loams, 2 to 5 percent slopes
Ravola clay loam, 0 to 2 percent .slopes
Ravola clay loam, 2 to 5 percent slopes
Ravola very fine sandy loam, 0 to 2 percent slopes
Ravola very fine sandy loam, 2' to 5 percent slopes
Ravola fine sandy loam, 0 to 2 percent slopes
Ravola fine sandy loam, 2 to 5 percent slopes
Ravola loam, 0 to 2 percent slopes
Redlands loam, 2 to 5 percent slopes
Red lands loam, 0 to 2 percent slopes
Redlands loam, 5 to 10 percent slopes
Redlands and Thoroughfare soils, shallow over bedrock,
5 to 10 percent slopes
Redlands and Thoroughfare soils, shallow over bedrock,
2 to 5 percent slopes
Riverwash, 0 to 2 percent slopes
Rough broken land. Mesa, Chipeta, and Persayo soil
materials
Rough broken land, Chipeta and Persayo soil materials
Rough gullied land
Thoroughfare fine sandy loam, 2 to 5 percent slopes
Thoroughfare fine sandy loam, 0 to 2 percent slopes
Thoroughfare fine sandy loam, 5 to 10 percent slopes
.2
1.7
.5
1.7
.3
.5
.5
1.7
1
1.3
.7
.1
8
.4
.1
.1
.1
3.4
2.5
6.1
.4
4.7
.1
2.1
.1
2.1
I "8
.1
.4
2.9
3.6
2.9
2.9
1.4
.1
.1
than 0.1 percent.
31
-------
Ul
to
Legend
Boundary of Irrigated Area
Grand Valley Salinity Control
Demonstration Project
*< Approximate Extent of Cobble
J Aquifer
Scale in Kilometers
Figure 9. Approximate areal extent of cobble aquifer in the Grand Valley.
-------
feasiblity of pump drainage from the aquifer. Much of this
cobble aquifer is covered with a thin, tight and often discon-
tinuous clay layer and/or a shale gravel washed from the nearby
Book Cliffs.
AGRICULTURAL ECONOMIC CONDITIONS
The modification of the Colorado River's flows have yielded
benefits in the form of irrigation, power generation, recreation,
industrial and domestic water supply, transportation and waste
disposal. In recent years, manufacturing and service industries
have experienced rapid growth, surpassing mining and agriculture
in economic importance in all seven basin states.
Agriculture is an important source of employment and income
to the local population in the Grand Valley area. In 1972, the
annual per capita income for Mesa County was $3,409 compared to
the Colorado per capita income of $4,006. The unemployment is
generally less than the state-wide level (in October 1976 it was
4.3 percent compared to 5.3 percent for the state). In 1970, the
median income for families was $8,065 for Mesa County. Farm
population in Mesa County for 1970 was 3,898 which was a 42.7
percent decline from 1960.
The Grand Valley contains approximately 65 percent of the
total irrigated croplands in Mesa County and accounts for about
75 percent of total value of farm products for the county. The
1969 census counted a total of 1,320 farms (by U.S. Department of
Commerce definition) for Mesa County which was a 21 percent
decrease since 1964.
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 are 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 popula-
tion engaged in agricultural activities is widely dispersed
throughout the Valley with most living on their property.
Leathers (1975) determined from 100 random selections that most
farm units were less than 40 hectares (100 acres) in size (Figure
10). Using data supplied by the USDA Soil Conservation Service,
frequency distribution of field sizes is shown in Figure 11. Of
the total of 7870 fields in the Valley, 50 percent are less than
2 hectares in size.
33
-------
U)
100 r
80
c
o
o 60
E
i_
^ 40
20
0
100 200 300
Net Cropped Acreage per Farm
400
500
Figure 10. Frequency distribution of farms in the Grand Valley (Leathers, 1975)
-------
100
80
o
o 60
U1
S 40
u.
fl>
a.
20
Field Size in hectares
2 . 4
T I I I
8
10
10
15 20 25
Field Size in acres
14
16
18
Figure 11. Frequency distribution of field sizes in the Grand Valley (USDA-SCS, 1976)
-------
AGRICULTURAL LAND USE
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) entering the Valley. Through a
long struggle, an irrigation system evolved to supplement the
otherwise meager supply of precipitation during the hot summer
months. However, the futility of irrigation without adequate
drainage was quickly demonstrated 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 as illustrated by a summary of land use in the
Valley presented in Figure 12. For example, of the more than
28,600 hectares (70,000 acres) or 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 phreatophytes and barren soil were also once part of an
irrigated acreage. Evidence exists that these same lands were
once highly productive and subsequently ruined by overirrigation
and inadequate drainage.
The various land use acreages in the Valley are shown in
Table 3. One of the most quoted statements in the literature
concerning the Grand Valley is that approximately 30 percent of
the farmable area is unproductive because of the ineffectiveness
of drainage in these areas. Examination of the results presented
in Table 3 indicates that 58 percent of the valley can be
classified as usable land. However, only 43 percent can actually
be considered productive. In the demonstration area, the
percentages are 70 and 52, respectively. The use of the term
productive relates to the areas producing cash crops such as
corn, sugar beets, small grains, orchards, and alfalfa.
36
-------
I20r
100
u>
O)
o
o
80
8
W
q
c
i eo
o
o>
0
*3
CD
(A
^* A /"\
4O
^^
U
c
o
_J
20
-
-
f— \
-
-
Sugar Beets
Orchards
Grain
Idle
Posture
Corn
Alfalfa
Irrigable
iviistBiiQnvuus
Industrial
Municipal
Municipal-
Croplands Industrial
Open Water
Phreatophytes
Barren
Soil
Phreatophytes
Open Water
Municipal -
Industrial
Phreatophytes
and
Barren Soil
Irrigable
/"* ^ Afhl f*f\f4f
or opionos
—
™
-
*J\S
40
C/J
£
30 P
o
£
O
O
0
c
O /N
20 j
in
^
C
o
_l
10
r»
Total
Surfaces and
Barren Soil
Figure 12.
Agricultural land use in the Grand Valley
(Walker and Skogerboe, 1971).
37
-------
TABLE 3. LAND USE SUMMARY BY CANAL IN THE GRAND VALLEY, COLORADO, 1969 (IN HECTARES)
Land Use Classification
Torn
Sugar beets
Potatoes
Tomatoes
Truck Crop
Barley
Oats
Wheat
Alfalfa
Native Grass Hay
Cultivated Grass Hay
Pasture
Wetland Pasture
Native Pasture
Orchard
Idle
Other
Farmsteads
Residential yards
Urban
U» Stock yards
00 Refineries
Miscellaneous Industrial
Natural Ponds .
Cottonwoods (H) J
Cottrmwoods (M) }
Cottonwoods (L)
Salt Cedar (H)
Salt Cedar (M)
Salt Cedar (L)
Willows (H)
Willows (M)
'•'illows (L)
Cattails (H)
Car rails (Ml
Greanewood (H)
Gr»asewood (M)
Gr«-»*ewood (L)
Shrubs: Wild Kose, etc. (Hi
Shrubs (M)
Shrubs (L)
Grasses and/or s^ces;;!!
Grasses and/or sedqes
Precipitation only
TOTAL
Stub
Ditch
23.
13.
39.
2.
17.
99.
44.
10.
2.
0.
12.
1.
0.
2.
6.
a.
0.
20.
312.
•J
6
2
4
4
9
9
1
0
8
5
6
8
a
5
1
8
6
7
Gov1 1
Hiqhlir.e
Canal
2419.1
1396.7
38.4
12.5
65.1
665.2
389.6
6.1
2839.9
182.1
620.3
4.5
19.0
281.2
1192.8
51.0
277.2
11.3
307.1
63.5
256.9
247.6
915.2
43.7
1.6
•* . 0
1J9.2
1184.7
82.9
31. 6
1.2
4219.6
17970. S
Price
Ditch
216.5
0.8
106.4
28.3
B.9
222.9
14.2
44.1
149.3
80.1
637.2
231.0
2.4
43.7
65.9
106.8
4.9
15.0
4.0
9.7
5.3
6.5
4.5
2.R
3.6
5.3
25.1
4.9
136.4
2180.5
Grand
Valley
Canal
2699.1
698.3
38.8
53.8
59.5
935.0
613.0
25.5
2106.3
34.0
619.4
1473.6
217.7
208.0
1707.0
4.5
494.0
13.8
1588.1
97.5
16.2
251.3
303.5
131.5
6.1
525.6
6.1
23.9
54.2
1.6
170.7
1408.4
21.4
73.7
0.4
1432.3
13115.8
Mesa
County
Ditch
63.5
25.1
6.1
100.3
36.4
129.5
19.8
16.6
136.8
32.0
7.7
3.5
8.5
19.4
1.2
5.7
6.1
4.5
68.4
40.1
13.fi
20.6
770.6
Adjacent
to
River
31.2
64.7
2.4
10.5
3.6
2.0
17.8
33.6
852.5
481.5
53.4
68.8
1073.8
43.7
35.6
1.2
307.5
27.1
3.6
292.1
3406.6
Orchard
Mesa #1
Canal
284.0
20.6
31.6
2f>.7
21.4
82.5
31.2
10.5
227.6
4.5
64.3
132.7
57.0
668.4
224.1
58.3
87.4
264.6
66.4
Jb.J-
15. -i
l.fi
2.n
12.3
1.6
20.6
4.0
17.4
8.1
41.7
1.6
53.4
2.0
i.f>
6.9
186.9
2/81. 7
Orchard
Mesa #2
Canal
26.3
17.4
2.0
155.6
3.6
21.8
108.8
1.2
744.0
143.6
36.4
11.3
19.8
7.3
19. C
3.9
8.5
6.9
5.3
S.9
87.6
15.0
3.G
3.*
203.1
1670.8
Redlands
Canal
50.2
13.0
1.2
6.9
7.3
22.3
164. 7
8.5
458.8
23.4
15(1. 1
245.6
27.9
15.4
273.9
13.0
17.8
29. 1
1.6
0.8
338.2
24.3
3.6
77.7
6.5
497.7
2479.5
Redlands
Power
Canal Total
5818.6
2123.6
110.0
100.7
146.0
1852.5
1092.5
51.0
50.2 5971. S
56.3
4.0 983. C
2.0 3094.8
4.5
23.1 441.3
2816.8
1.2 3930.6
57.9
10.1 991.7
214.8
14.6 2593.5
3.2 264.3
16.2
293.4
7.7 1539.9
919.6
65.1
79.7
2.0 2890.4
19.1
88.2
169.9
9.7
8.5
339.4
20.6
2.0 3190.0
19R.2
210.5
4.*
5.6
3.6
0.4 7.3
5.3
2.0 7011.3
122.5 49817.5
1 Note: H - Heavy cover, M - Medium cover, L * Light cover
-------
SECTION 5
PRESENT IRRIGATION PRACTICES
WATER SUPPLY
The primary source of water for irrigation in the Grand
Valley is the Colorado River, with the exception of about 1200
hectares (3000 acres) which are irrigated from the Gunnison
River. There is no groundwater used for irrigation due to the
high salinity (8700 mg/1) of the waters in any of the potentially
productive aquifers. A schematic representation of the
hydrologic budget for the area is presented in Figure 13.
Irrigation water entering into the Grand Valley is of
relatively high quality. The electroconductivity ranges from
around 350 ymhos/cm to a maximum of 4000 ymhos/cm with the
average value being 480 ymhos/cm. Suspended solids concentra-
tions in the incoming irrigation water range from a low of 5 ppm
to over 4000 ppm with an average mean of 200 ppm. However, the
drains which carry field tailwater often obtain suspended solids
concentrations in excess of 30,000 ppm. The USDA Soil Conserva-
tion Service estimates that 2.6 million metric tons (2.9 million
tons) of sediment are added annually to the Colorado River from
the irrigation of lands in the Grand Valley. Municipal water
(potable) supplies in the Valley are obtained from a well-
developed system of reservoirs on the Grand Mesa and are of a
very high quality. This water, however, is much more expensive
than irrigation water and, consequently, many homeowners use
irrigation water for the irrigation of landscapes and gardens.
Irrigation water costs in the Grand Valley range from
$9.90/ha-m ($1.22/AF) to $43.80/ha-m ($5.40/AF) depending on the
canal and number of shares. The average cost tends toward the
lower value.
WATER RIGHTS
Early exploration concluded that the Grand Valley had
limited potential for agriculture since the terrain appeared very
desolate. A great deal of appreciation for this judgment can be
acquired just passing through the area and noting the landscape
outside the irrigated agricultural boundaries. In 1853, Beckwith
(the expedition recorder for the Captain John W. Gunnison
39
-------
Plateau Creek Inflow
(13,800 ha-m)
Colorado River Inflow
( 297,650 ha -m)
Cropland
Precipitation
, ( 3,100 ha-m)
Gunnison River Inflow
( 178,000 ha-m)
Evaporation a Phreatophyte Use
Canal Diversions Adjacent to River ( 3,450 ha-m)
(69,000 ha-m)/ ^/7 lrriaation from Return Flow (45,100 ha-m)
Net Evaporation a
Phreatophyte
Evapotranspiration
(8,400 ha-m)
Canal ft Lateral
Seepage
(9,000 ha-m
Toilwater a
SpjJ Is (37,000 ho-m
eep Percolation
(7,500 ha-m)
Cropland Evapotranspiration
{ 18,600 ha-m)
Colorado River
Outflow
(462,100 ha-m)
Figure 13. Graphic representation of the magnitude and distribution of
water flows in the Grand Valley for 1968 (Walker, 1970).
-------
exploration, 1853) described the Valley as, "The Valley, twenty
miles in diameter, enclosed by these mountains, is quite level
and very barren except scattered fields of greasewood and sage
varieties of artemisia—the margins of the Grand (Gunnison) and
Blue (Colorado) River affording but a meager supply of grass,
cottonwood, and willow." Soon after the settlement began
(September, 1881), it was realized that the climate could not
support a nonirrigated agriculture. As a result, irrigation
companies were organized to divert water from the river for
irrigation. A map of the irrigation canal system in the Grand
Valley is presented in Figure 14.
The first such company was the Grand Valley Irrigation
Company who owns and operates the Grand Valley Canal, and, at the
present time, serves 18,890 hectares (46,678 acres) of land,
although in the 1969 land use survey, only 12,030 hectares
(29,727 acres) were irrigated.
The present Grand Valley Canal system comprising
approximately 124.4 kilometers (77.25 miles) of canals and
subcanals is the result of a consolidation of the Grand River
Ditch Company, Grand Valley Canal Company, Mesa County Ditch
Company, Pioneer Extension Ditch Company, and the Independent
Ranchmen's Ditch Association. The construction of what is now
the main line Grand Valley Canal probably began in 1882 since the
original priority is dated August 22, ,1882, although A. J. McCune
who was the engineer for the Grand River Ditch Company filed a
statement with the clerk and recorder of Mesa County, Colorado on
April 5, 1883, that construction commenced January 10, 1883. At
this time, the ditch was owned by Matt Arch, E. S. Oldham,
William Oldham, John Biggies, and William Cline who planned for a
capacity of about 786 cfs (22.26 cms). The times of the early
development were uncertain and the company, like so many others,
was facing financial trouble. It was then sold to the Traveler's
Insurance Company which also acquired title to the other four
companies now making up the system. On January 29, 1894, the
Grand Valley Irrigation Company was incorporated when the
Certificate of Incorporation was filed with the Secretary of
State's office and the title was acquired from the insurance
company.
Although the original decree was based on an estimated
acreage of 30-35,000 acres (12,500-14,600 hectares), later
investigations revealed the acreage was slightly less than 40,000
acres (16,700 hectares), plus an additional 4,661.25 acres
(1,942.19 hectares) not yet developed, for a total of about
44,000 acres (18,300 hectares). If the usual 200-day irrigation
season is experienced, this water right amounts to approximately
1.76 hectare-meters/hectare (5.76 acre-feet per acre) on a total
irrigated area basis, from which an estimated 20 percent seepage
loss rate of 0.32 hectare-meters per hectare (1.05 acre-feet per
acre) leaves about 1.44 hectare-meters per hectare (4.71
41
-------
to
\
Scale in Miles
1012345
Scale in Kilometers
Figure 14. Grand Valley canal distribution system.
-------
acre-feet per acre) for irrigation. The water right based on the
net irrigated area is much higher, approaching 2.60 hectare-
meters per hectare (8.53 acre-feet per acre) and 2.08 hectare-
meters per hectare (6.82 acre-feet per acre), respectively.
The Grand Valley Project (built by the USDI, Bureau of
Reclamation) serves water to four irrigation companies, the Grand
Valley Water Users Association, the Orchard Mesa Irrigation
District, Palisade Irrigation District (Price Ditch), and the
Mesa County Irrigation District (Stub Ditch).
The Grand Valley Water Users Association was incorporated
February 7, 1905, and later renewed the incorporation
September 11, 1945. It operates the Government Highline Canal
which serves about 18,507 hectares (44,416 acres) of irrigable
land. In 1969, 10,186 hectares (25,169 acres) were irrigated
under this canal. In addition, the Association diverts 22.60 cms
(800 cfs) during the nonirrigation season for power development
through a siphon across the Colorado River shortly below the main
diversion. During the irrigation season, 11.30 cms (400 cfs) is
used for power development, with the remaining 11.30 cms (400
cfs) passing through the irrigation pumps to raise the irrigation
water to the Orchard Mesa Canals. The power generated with this
water is sold to the Public Service Company of Colorado to help
pay the debt on the original project. The length of the
Government Highline Canal is 73.7 km (45.8 miles).
The Orchard Mesa Division of the Grand Valley Project was
formed by request of the people of the Orchard Mesa Irrigation
District when the prior operation was facing bankruptcy. The
District was organized under the 1905 Colorado Statute covering
irrigation districts, which was later revised to comply with the
1921 Colorado law.
The operation of the Orchard Mesa Irrigation District in
many ways is similar to the Association in that the water duty
and land classification are the same. The District is now
provided water through the siphon diversion under the Colorado
River from the Government Highline Canal into the Orchard Mesa
Power Canal (3.9 km in length). During the irrigation season,
1/2 of the 22.60 cms (800 cfs) in the canal is diverted through ,
the Orchard Mesa Irrigation District pumps which lift 2.27 cms
(80 cfs) 12.2 meters (40 feet) into the Orchard Mesa #2 Canal
(26.1 km in length) and 1.70 cms (60 cfs) 39.3 meters (130 feet)
into the Orchard Mesa #1 Canal (24.1 km in length). The Orchard
Mesa system serves 3114 irrigated hectares (7694 acres) according
to the 1969 land use survey.
The Palisade Irrigation District, with essentially the same
organizational format as the Orchard Mesa Irrigation District,
operates the Price Ditch (9.5 km). This ditch is supplied 1.87-
1.93 cms (66-68 cfs} through a turbine pump just off the
43
-------
Government Highline Canal as it exits through Tunnel No. 3. An
additional 0.68 cms (24 cfs) is delivered under a carriage con-
tract through turnouts in the Highline Canal. There were 1743
hectares (4306 acres) irrigated directly under this canal in 1969,
The Mesa County Irrigation District, which operates the Stub
Ditch (11.3 km) has an irrigation water right of 1.13 cms (40
cfs). The operation and organization of this district are
similar to the previous five districts mentioned. At the turbine
pump serving the Price Ditch, 0.42 cms (15 cfs) are pumped into
the Stub Ditch. The remaining 0.71 cms (25 cfs) is diverted
under a carriage contract directly from the Highline Canal to
agricultural lands within the boundaries of the Mesa County
Irrigation District. A total of 246 hectares (608 acres) was
irrigated directly from this canal in 1969.
Both the Palisade Irrigation District and the Mesa County
Irrigation District were organized independently of the govern-
ment projects. Their history is somewhat unknown to the writers,
but they consolidated their systems with the Highline Canal when
it was built, presumably to streamline their operation and to
eliminate operation and maintenance costs of the individual
diversion works which can be substantial. The old river diver-
sion works (now abandoned) can still be seen just above the town
of Palisade.
The Redlands Water and Power Company, a mutual ditch
company, irrigates about 1200 hectares (3000 acres) southwest
of Grand Junction and south of the Colorado River in a canal
carrying 8.97 cms (670 cfs). Under this diversion 0.17 cms (6
cfs) is used for irrigation of lands below the power canal, 17.24
cms (610 cfs) for power generation, and 1.53 cms (54 cfs) is
pumped to an initial height of 38.7 meters (127 feet) for irri-
gation. Small areas in the project are served by higher lifts.
The highest is about 91.4 meters (300 feet). Electricity in
excess of pumping needs is sold to project settlers and to the
Public Service Company. Much of the lands served by these canals
is residential.
The water rights of the individual canals and the priorities
are listed in Table 4. The dimensions, capabilities, and seepage
rates of the canals in the Grand Valley are tabulated in Table 5.
CANAL OPERATIONS
The canals are operated by the previously mentioned canal
companies. These companies are relatively small with small
staffs compared to similar organizations in other irrigated areas
in the western United States. Generally speaking, maintenance of
canals and headgate regulation are kept to a minimum. The
Government Highline, however, does have a limited demand type
44
-------
TABLE 4. WATER RIGHT DECREES FOR THE GRAND VALLEY IRRIGATED AREA
Original
Name of Ditch Appropriation
Date
(1) Orchard Mesa Power
Canal
(2) Palisade Irr. Diet.
(3) Pallaado Irr. Diat.
(4) Orchard Mesa Power Canal
(5) E. Palisade Irr. Dist.
(6) Mesa County Irr. Dist.
(7) Mesa County Irr. Dist.
(8) Mann Pumping System
(9) Orchard Mesa Irr.
Dist.
(10) Orchard Mesa Irr. Oist.
(11) orchard Mesa Irr.
Dist.
(12) Grand Valley Project
(13) Grand Valley Project
(14) Rose Point Power Canal
(15) Orchard Mesa Irr. Dist.
(16) Palisade Irr. Dist.
(17) Grand Valley Irrigation
Company
(18) Grand Valley Irrigation
Company
(19) Redlands Water & Power
Company
3-6-89
10-1-89
10-1-89
8-2-98
10-1-00
7-6-03
7-6-03
9-10-03
10-25-07
10-25-07
10-25-07
2-27-08
2-27-08
7-2-1O
4-26-14
6-1-18
7-27-12
7-25-14
Decree
Allowed.
(cfs) if
110.70
573.00
80.00
139.30
10.20
627.00
40.00
1.00
195.00
75.00
180.00
730.00
400/800
113.25
100.00
23.50
520.81
195.33
670.00
Use
of
Right
Irrigation
Pumping
Irrigation
Irrigation
Irrigation
Pumping
Irrigation
Irrigation
Irr. Pump
Irrigation
Conditional
Irrigation
Power
Irrigation
Conditional
Irrigation
Irrigation
Irrigation
Irrigation
& Power
Comments^
Abandon, land now in Orchard Mesa Irr. Dist., 1O cfs irr.,
rest pumping, rights not transferred to District
Power plant abandon, decree usable only with approval of
Bureau of Reclamation.
Decree delivered by Gov't Highline Canal, point of diversion
changed by decree of 7-25-41 (Price Ditch) .
Same as (1).
Former steam ptvping plant, now gravity from Orchard Mesa
Power Canal (Orchard Mesa Irr. Dist. owns decree.
Same as (2) , (Stub Ditch) .
Decree now delivered by Gov't Highline Canal by gravity and
pumping, point of diversion not formally changed.
Former steam pump from river, now pumped from Orchard Mesa
Power Canal, electric motor.
Now diverted through Gov't Highline Canal, but through same
pumping plant, point of diversion changed.
Same as (9).
Same as (9), made absolute in decree of 7-25-41, 130.0 cfs
power, 50 cfs ixrig.
Quantity fixes in decre-J of 7-25-41 as above, same applies
for power and domestic.
Quantity fixed in decree of 7-25-41 with priority date as above,
400 cfs irrigation season, 800 cfs non-irrigating season.
Abandon, decree property of Orchard Mesa Irr. Dist., no change
in point of diversion.
Conditional water claimed for irrigation, none claimed for
pumping water.
Date of this decree is date of change of point of diversion to
Gov't Highline Canal (3). This decree provides for laterals
fed directly from project canal to Palisade lands.
Priority Date of 8-22-82, No. 1 priority on the Colorado
River. Based on 30-35 thousand acres w/20 percent loss rate.
First enlargement. Priority 358 of which 75.86 cfs is conditional
upon the addition of 4661.25 acres to the system.
60 cfs used for irrigation. Hater is diverted from the
Gunnison River.
1 cfs - 0.0283 m /sec
Decrees (1) through (16) are water right decrees incorporated in the Grand Valley Project.
-------
TABLE 5. DIMENSIONS, CAPACITIES AND SEEPAGE RATES
OF CANALS IN THE GRAND VALLEY, COLORADO
Canal
Government Highline
Grand Valley
Grand Valley Mainline
Grand Valley Highline
Kiefer Extension
Mesa County
Independent Ranchman's
Price
Stub
Orchard Mesa Power
Orchard Mesa No. 1
Orchard Mesa No. 2
Red lands Power
Redlands No. 1 and No. 2
TOTAL CANALS
Length
Km
73.7
19.8
21.7
37.0
24.5
4.0
17.4
9.5
11.3
3.9
24.1
26.1
2.9
10.8
286.7
Inlet Q
m^/sec
16.99
18.41
7.08
8.50
3.96
1.13
1.98
2.83
0.85
24 . 07
3.02
1.98
24.07
1.70
Wetted
Perimeter
m
19.19
16.67
13.86
12.62
7.25
6.67
3.17
7.27
2.94
8.20
6.46
3.58
16.88
3.95
Days of
Operation
per Year
214
214
214
214
214
214
214
214
214
365
214
214
365
214
Effective
Seepage Rate
m2/mVday
0.076
0.030
0.046
0.04G
0.046
0.046
0.046
0.046
0.046
0.061
0.061
0.061
0.050
0.122
Seepage
m3/day
77,300
10,900
10,800
22,100
6,800
600
2,600
2,200
1,400
3,300
7,400
4,800
1,900
4,200
156,300
Salt
Contribution
m. tons/yr
54,100
7,600
7,600
15,400
4,800
700
1,800
1,600
1,000
2,300
5,100
3,300
1,300
2,900
109,500
-------
lateral diversion system, but the water deliveries are measured
only infrequently.
Adjusting the amount of the canal diversions at the river is
also kept to a minimum. Regulation of water within the canal
system is controlled by spillage into drains and natural washes.
This water contributes very little to the salt loading from the
Valley, but is often 20 percent to 25 percent of the total
diversion. This is obviously a luxury which can be taken only
in an area with abundant water and very senior water right
appropriations.
If the canals would go to a strict demand type delivery
system, the spillage would be negligible but would entail the
general acceptance of more efficient irrigation methods such as
trickle, sprinklers, borders, dead-level irrigation, cut-back
irrigation, tailwater recovery systems, automation and changes
in present tillage practices. It would require that the canal
companies hire additional staff and purchase more equipment. The
present very low cost of water would have to increase
substantially to pay for these services.
LATERAL OPERATION
There are several hundred laterals (1553 not including the
Redlands) in the Grand Valley covering a distance of more than
600 kilometers. The term lateral is read in this text to refer
to those small conveyance channels that deliver waters from the
company canals to the farmer's fields, and are defined as the
distance from the headgate to the point of delivery to the last
farm. These small channels usually carry flows less than 0.14
cms C5 cfs) and range in size up to 1.2 or 1.5 meters (4 or 5
feet) of wetted perimeter.
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 that the Grand Valley Water
Users Association (Government Highline Canal) which will treat
some of their larger laterals as small canals and loosely manage
the water within the lateral by regulation of the "sublaterals."
However, no effort is made to control the water use in the
sublaterals or on the farm.
Single users served by an individual canal 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 growers,
run continuously throughout the irrigation season with unused
water being diverted into a convenient drainage channel.
47
-------
Data collected during the course of the investigations
indicate that as the size of the laterals approaches 48-50
hectares (120-125 acres) and/or have more than 2-4 users, they
will run continuously throughout the season. A frequency distri-
bution of the laterals in the Valley is presented in Figure 15.
The longest lateral in the Valley is 8990 meters (29,500 feet) as
defined by the USDI, Bureau of Reclamation, 1975 (the length of a
lateral is from the headgate to the last farm delivery). The
largest lateral in the Valley is under the Government Highline
Canal and contains 707.81 hectares (1749 acres). The areal
distribution of laterals for the Valley is graphically presented
in Figure 16.
Under the Stub Ditch, Price Ditch, and Government Highline
Canal (east of Indian Wash), the water is allocated on a per acre
basis and can never be transferred from the land. The allocation
is 0.5 Colorado Miners Inches (CMI) per acre (0.91 1/s/ha) and
must run continuously under the by-laws of the Palisade Irriga-
tion District (Price Ditch) and the Mesa County Irrigation
District CStub Ditch). It should be noted that west of Indian
Wash, where the Government Highline Canal is not serving lands
under carriage contracts, the water is provided on a modified
demand basis varying from 0.75 to 1.0 cfs per 40 acres (0.021
to 0.028 m3/s per 16.2 hectares).
The Grand Valley Canal which diverts water from the Colorado
River releases water to the Mesa County Canal and several others
are entirely privately owned and have an arrangement by which the
water shares are bought, sold, rented, or transferred anywhere in
the entire system. One share of water is 0.4 Colorado Miners
Inches (0.30 1/s).
ON-FARM WATER USE
The common irrigation philosophy concerning water duty is
one share (4.7 to 5.8 gpm or 0.30 to 0.37 1/s) for one acre,
continuous flow, which was a reasonable criterion when the canal
systems were first established. For example, if a farmer had 80
(32.4 hectares) acres, had 80 shares of water, and, if the total
allotment of water was rotated around the farm, the irrigations
were fairly efficient. However, since that time, average farm
units have become much smaller, and using the same criterion of
1 share per acre, the irrigations obviously had to become less
efficient because corresponding smaller streams of water have
slower advance times and, therefore, a greater opportunity time
for larger amounts of deep percolation.
Practically all irrigations in the Valley utilize open
ditches with siphon tubes on row crops with 30-inch row spacings
On crops such as alfalfa and small grains, the irrigations are
usually a variation of flood irrigation using "corrugations" or
48
-------
100
Lateral Length , meters x 100
8 10 12 14 16
18
20
800
1600
2400
3200 4000
Lateral Length, feet
4800
5600
6400
Figure 15. Frequency distribution of lateral lengths
in the Grand Valley (USDI, USER, 1975).
22
7200
-------
Ul
o
100
90
80
70
60
«*•
o
£ 50
o>
o
v 40
30
20
10
0
Figure 16,
Lateral Size in hectares
7 8 9 10 II 12
T
T
T
T
T
T
13
T~
14
T~
15
T"
16
"T"
17
—r~
18
10
15 20 25
Lateral Size in acres
30
35
40
45
Frequency distribution of the area contained under
laterals in the Grand Valley (USDI, dSBR, 1975) .
-------
shallow furrows, and siphon tubes or a "cut-and-dam" system with
some unlined ditches. According to the USDA-SCS (1976), there
are more than 1640 km of head ditches in the Valley of which
about 1300 km are unlined.
There is very little automation of irrigation systems in the
Valley. The only automated systems, other than on turf applica-
tions, were installed for demonstration or research purposes by
governmental agencies.
The USDA Soil Conservation Service inventory of irrigation
practices in the Grand Valley indicates that there are 7870
fields with the average size about 2.2 hectares (5.5 acres)
(see Figure 11). The average field width (Figure 17) is about
140 meters (450 feet); the average field length (Figure 18) is
approximately 159 meters (520 feet); and the average field slope
(Figure 19) is close to 1.25 percent.
The majority of irrigated soils in the Grand Valley are clay
loams, with 29.5 percent of the total irrigated acreage being
classified as Billings silty clay loam. The soils are generally
tight with intake characteristics decreasing with time through
the irrigation season (Figure 20).
Because of the low cost of water, the common philosophy of
the Grand Valley agricultural community regarding irrigation
improvement is limited to concrete linings and land shaping
rather than installation of more efficient and sophisticated
irrigation methods, which are generally not economically war-
ranted. This attitude is partly the result of national USDA
Agricultural Stabilization and Conservation Service (ASCS) regu-
lations on cost sharing which do not allow matching funds for
moveable sprinklers and gated pipe (or other types of "portable"
systems).
The USDA Soil Conservation Service estimates that
approximately one-fifth of the head ditches and laterals in the
Grand Valley have been lined, although some are undoubtedly in
need of repair. Many of the irrigation leaders in the area
proudly point to this fact as a sign of local progressive
irrigation practices.
A very common and generally necessary irrigation practice is
to plant the crops and irrigate them "up." Furrows are usually
on a 30-inch (76 cm) spacing, and the seeds are planted halfway
between two furrows. Under this practice, individual irrigation
sets often run 36 to 48 hours until the field has become
"blacked" out (the water has completely soaked across all the
area between furrows). This first irrigation is unquestionably
the water application which has the largest contribution to deep
percolation and could probably be reduced by changing tillage
practices, i.e., planting on the edge of a furrow rather than in
51
-------
Ul
N)
100
100
Field Width, meters
200 300
200
400
600 800 1000
Field Width, feet
1200
1400
1600
Figure 17.
Frequency distribution of field widths
in the Grand Valley (USDA-SCS, 1976).
-------
Ul
U)
100
Field Length in meters
200 300
400
500
200
400
600 800 1000
Field Length in feet
1200
1400
1600
Figure 18.
Frequency distribution of field lengths
in the Grand Valley (USDA-SCS, 1976).
-------
Ul
O
*-
O
d>
0)
0.
0.5
1.0
1.5 2.0 2.0 30
Field Slope in percent
3.5
4.0
4.5
Figure 19
Frequency distribution of field slopes (in
percent) in the Grand Valley (USDA-SCS, 1976).
-------
Ul
en
Perennial Crops
I 2 3
Number of Previous Irrigations
Figure 20. Relative infiltration rate function for perennial
and annual crops in the Grand Valley.
-------
the center. However, attempts to introduce new tillage practices
into the area have met with limited success. The percent of
annual salt pickup during the irrigation season is graphically
indicated in Figure 21.
TAILWATER REMOVAL
Field tailwater is the responsibility of each individual
irrigator. Most of the tailwater is dumped directly into drains
or into other laterals or canals where it is reused. Very few
tailwater ditches run much farther than the width of the field
before they are put into a drain or other conveyance system.
There is only one tailwater recovery (pump-back) system in the
Valley which was put in by the Colorado Water Conservation Board
as a demonstration project.
The many open drains in the Grand Valley play an important
role in tailwater removal. In the demonstration area, these
drains carry only about 27 percent of the total groundwater
flows, and their major benefit has been to intercept and convey
tailwater runoff which would otherwise flow over surface lands,
infiltrate, and contribute to additional subsurface groundwater
flows, which would subsequently reach the Colorado River with
increased salt pickup.
56
-------
100
CL
3
-SC
u
a
a
CO
"o
3
C
0)
o
w
-------
SECTION 6
IRRIGATION WATER REQUIREMENTS
COMPUTING EVAPOTRANSPIRATION
A review of the alternative approaches to estimating the
volume and rates of water evaporated from wet crop and soil
surfaces or transpired by the plants can be found in several
literature sources (Jensen, 1973; Doorenbos and Pruitt, 1977) .
So far as this technology is applicable to the management of
irrigation return flow quality (through irrigation scheduling) ,
Skogerboe et al. (1974b) and Jensen (1975) are good summaries.
In this section, some of this previously reported work will be
repeated in order that in later paragraphs our efforts at
calibrating and verifying estimating procedures will be more
understandable .
Methods of Estimating Evapotranspiration
The analysis of irrigation return flows in the Grand Valley
has included three principal approaches to estimating evapotran-
spiration: (a) the Blaney-Criddle method; (b) the Modified
Jensen-Haise method; and (c) the Penman Combination method.
These methods represent much of the range in sophistication
available today, varying in detail from a temperature dependent
analysis (Blaney-Criddle) to an analysis of energy balance and
convective transport (Penman) .
The Blaney-Criddle Method —
The Blaney-Criddle procedure for estimating
evapotranspiration has the form (Blaney and Griddle, 1950):
k k t p
Et - —TOO — - • •- .............
where,
Et = monthly evapotranspiration in inches;
kfc = 0.0.173t - 0.314; ............. (2)
kc = time distributed crop growth stage coefficient;
t = mean monthly temperature in °F; and
58
-------
p = mean monthly percentage of annual daytime hours.
Crop curves and values for p can be found in Blaney and Criddle
(1950) . Estimates of Et were originally intended on a seasonal
basis, but work by numerous individuals have shortened this
interval by interpolating values for p and k .
c
The Modified Jensen-Haise Method —
The Jensen-Haise procedure is a temperature and solar
reduction equation adjusted for location and elevation by vapor
pressure functions (Jensen and Raise, 1963) :
Etp = Ct(T - V Rs
in which,
E. = average daily potential evapotranspiration of a well-
" watered alfalfa crop having 30-50 cm of top growth,
mm/day ;
T = mean daily temperature, °C;
R = total daily solar radiation in langleys multiplied by
0.0171 to get mm/day;
T = intercept of the temperature axis
2C
= -2.5 - 0.14(e2 - e-j^) °C/mb - elev(m)/550. ... (4)
e2,e, = saturation vapor pressures at the mean maximum
and mean minimum temperature, respectively, for
the warmest month of the year, in mb;
CT = temperature coefficient
Cl + C2 CH
(5)
C-L = 38 - (2°C x elev(m)/305) .......... (6)
C2 = 7.6°C ................... (7)
C = 50 "^ .
CH (e2 - 6l) .................
In order to relate Etp to evapotranspiration values for
other crops, a crop growth stage coefficient was defined,
kco = VEtp
k = crop growth stage coefficient; and
where
. = potential evaporation for the specified crop
59
-------
Kincaid and Heerman (1974) present polynomial regression
equations for kco based on the table of coefficients presented by
Jensen (1973).
The Penman Combination Method —
Penman (1948) first derived an equation for the
evapotranspiration of a short, well-watered crop (generally
assumed to be grass) based on a combination of energy balance at
the crop surface and the heat-mass transfer processes due to air
movements. The equation which resulted and is used today is
written for alfalfa:
Etp= [A*7 (*n+G)+15-36 7^(a+bU2)(ez'-ez) 1-0. 0171 . . (10)
in which,
A = slope of the saturation vapor pressure curve at a
specified temperature, d(mb)/d(°C);
Y = psychrometic constant, mb/°C;
R = net radiant energy, langleys/day (ly/day) ;
G = soil heat flux, ly/day;
U2 = wind run at a height of 2 meters, km/day;
a,b= empirical regression coefficients requiring local
calibration;
e °= saturation vapor pressure at the surface of the
crop, mb; and
e = vapor pressure at the crop surface, mb.
z
The data available at most irrigated sites employing the
Penman approach include solar radiation (Rs) , temperature, wind,
and relative humidity or dew point temperature. In order to
develop the parameters for Eq. (10), a number of empirical
functions can be used. In the Grand Valley, the approach that
was used is described below.
Net radiation, Rn, was determined from relationships
presented by both Jensen (1973) and Kincaid and Heerman (1974) .
This procedure begins by defining solar radiation on a clear,
cloudless day by plotting a curve through the long-term maximal
values:
Rso - 760 exp-t-! ........... (11,
where
R = clear day solar radiation, ly/day; and
SO
Day 1 = March 1.
A more recent review by the writers of Eq. (11) indicates the
coefficient 760 should be increased about 10 percent, but the
60
-------
overall effect is negligible. In a similar view, it is necessary
to define the clear day net outgoing longwave radiation:
Rbo " e'
where
R, = net clear day outgoing longwave radiation, ly/day;
e1 = -0.2 + 0.261 exp[-7.77 x 10~4 (273-Tk> 2] . . (13)
T, = temperature in degrees Kelvin (°C + 273)
— 8
a = Stefan-Boltzmann constant = 11.21 x 10 ly/°K
Based on Eqs. (11) and (12), the longwave radiation (R.) occurring
on a particular day equals (Jensen, 1973) :
Rb = [1-2 IT-' °'21 Rb
so
and
Rn -
in which a = crop albedo (generally taken to be 0.23).
The exchange in heat from the soil is based on two
assumptions: (1) the soil temperature to a depth of 2 meters
varies approximately with average air temperature; and (2) the
volumetric heat capacity of the soil is 0.5 cal cm"3 "C"1. The
soil heat flux, G, is then written as (Jensen, 1973):
T . — T .
G = " x 100 .............. (16)
At
where,
G = soil heat flux, ly/day;
T._, = mean temperature for the previous period, °C;
T. , = mean temperature for the following period, °C; and
At = days between the preceding and following periods
(period interval) .
Kincaid and Heermann (1974) use a comparison of current
temperature with the average of the previous 3 days to calculate
G for irrigation scheduling. They also presented convenient
expressions for A/A+Y/ y/A+Y, and e° as follows:
Y/A+Y = 0.959 - 0.0125T + 0.00004534T2 ..... (17)
61
-------
= 1 - (Y/A+Y) ............... (18)
e° = -0.6959 + 0.2946T - 0.005195T2 + 89xlO~6T3 . (19)
z
in which T represents the mean daily temperature in °F.
The evaluation of the term (e£ - ez) in the Penman equation
can be made in several ways. For the Grand Valley studies, the
following expression was used:
e° + e°
(ez ~ ez) = 2 2 1 ~ el x rh ' • ........ (20)
in which
e°, e9 = saturation vapor pressure at maximum and minimum
daily temperatures/ mb; and
rh = maximum daily relative humidity (usually taken as
the 6-8 AM values) expressed as a fraction.
Calibrating Estimating Formulas
In 1974 two constant-water-table grass lysimeters one meter
square in surface area were set up in the Grand Valley along with
a climatic station recording precipitation, temperature, solar
radiation, and relative humidity. A diagram of the lysimeters is
given in Figure 22. Evans et al. (1978) presented the data
collected from the lysimeters and their extension to other
locally grown crops.
Blaney-Criddle Calibration —
The Blaney-Criddle equation, as described earlier,
underestimates Etp in the Grand Valley by approximately 40
percent. Generally, in the windy months of spring the procedure
underestimates Etp by as much as 50 percent, whereas later
results show substantial overestimation. The calibration of Eq.
(1) involved solving for the k. term:
E. • 100
at - b =
p.fkc ................
In this case, k. was found to be:
kt = -0.002686t + 1.49 ............. (22)
Even so, the month-to-month variations were large (i.e.,
equations 1 and 22 overestimate Etp in May, July and September,
while it underestimates the values in June and August) . It
should be noted that calibration of the kt parameter over so
62
-------
Soil
ttv#
• • *.* *• .*
i«*»«4*«f,
'; Gravel
Float Valve
Welded Aluminum Lysimeter
Tank Im x Im x 0.46 m
p
o
I "
4 Tubing
Water Stage
Recorder
-—Reservoir
^i*r.,*r.tti.i*i •.«..*.!..
Figure 22. Schematic view of the constant water level
tank grass lysimeter used in the Grand Valley.
-------
short a time period does not give complete confidence in the
resulting equations because temperature is only one of many
climatic factors affecting evapotranspiration. A longer term
analysis is needed before proposing a usable function for k^
beyond that expressed in Equation 2.
Jensen-Haise Calibration—
In the Grand Valley, the mean minimum and mean maximum
temperatures at the 1480 meter elevation are 34.6°C and 18.1°C,
respectively. At these temperatures, 62 = 55.29 mb and e^ =
20.58 mb so that CH = 1.44. The data similarly result in dp
being equal to 0.0255 and Tx = -10.05. The Jensen-Haise equation
for the Grand Valley is, therefore (multiplied by 0.0171 to yield
mm/day):
E = 4.36 x 10~4(T + 10.05)Rg (23)
Equation 23 overestimates evapotranspiration as determined
from the grass lysimeters (and divided by 0.87) by 4 percent to 5
percent over the accumulated irrigation season. However, during
the windy periods of May and June, Equation 23 can underestimate
Ej-p by about 10-15 percent. By solving for CT and Tx and
correlating with the lysimeter data, Equation 23 was slightly
modified as indicated below:
E. = 4.75 x 10~4(T + 9.646)R (24)
»ip s
Penman Calculation—
The Penman equation has several regression formulas implied
in its form as listed in Equation 10. An evaluation of each of
these was made, but the only effective correlation was between
the wind term coefficients, a and b. Interestingly enough, the
values determined for alfalfa (a = 0.90 and b = 0.0062) are not
significantly different from the values Penman originally
suggested for grass (Jensen, 1973). The resulting Penman formula
for alfalfa (E. ) is:
tp
E. = 0.0171[C, (R+G)+C~(0.9+0.0062 U0) (e°-e )] . (25)
T»jp JL n £, £ Z Z
Comparison of Methods
The mean monthly measured values of the grass lysimeter
evapotranspiration are plotted against both the calibrated and
original Blaney-Criddle relationships in Figure 23. These data
were collected in 1975. The other years do not differ markedly,
however. The revised function for kt allows a substantially
better monthly estimate of consumptive use than the version
suggested by Blaney and Griddle (1950). In fact, over the season
64
-------
I "
e 10
^
uT 9
o>
o 8
6
o.
en
2 5
I 4
o
o
i 2
0)
o ,
0. I
tf) n
o 0
CD
TIITIITIITTl T III I I I T I I I I I III llJITTIIIll
1 I
I 1
li
I
- Measured, 1075mm Total
---- Calibrated Equ, l075mmTotal
--- Original Equ, 654mm Total
iii i iliiiii liiitfliiiif It ji ii I iiiiiiiiiii
S 15 29 5 IS 25 S 15 25 5 15 25 5 15 25 5 IS 25 S 15 25 5 IS 25 S IS 25
Apr May Jun Jul Aug Sept Oct Nov Dec
Figure 23. Comparison of lysimeter data with the Blaney-Criddle
estimates for well-watered grass in 1975.
65
-------
the measured and predicted (by the adjusted equation) are
identical. The Blaney-Criddle approach is satisfactory for time
periods greater than or equal to one month, but not the daily or
weekly periods needed for irrigation scheduling. It is also
obvious that application of the original Blaney-Criddle approach
can lead to significant errors if the method is not locally
calibrated.
Figure 24 shows the comparison of measured and calculated
Etp values during the 1975 irrigation season in Grand Valley when
the Jensen-Haise method is applied. The error introduced by
simply using the reported function with the altitude correction
is too small to be significant/ although about a 4-5 percent
improvement was achieved with local calibration. The Jensen-
Haise method is often used in conjunction with the Penman equa-
tion in many irrigation scheduling services, primarily from July
on when wind is less significant. The largest error in the time
distributed estimates (5-6 day intervals) was less than 2 mm per
day in the latter part of the Grand Valley's 1975 irrigation
season. In June, a 5 mm error is noticeable.
Although the Penman equation shows more seasonal error than
the Jensen-Haise approach (Figure 25), it follows the lysimeter
data better over the season. In evaluating these results, it
appears that time intervals less than 3-5 days are not justified
by the sensitivity of the approaches. In fact, the correlation
between measured and predicted values on a daily basis was less
than 70 percent, whereas it was approximately 90 percent for 5-6
day periods.
IRRIGATION SCHEDULING
Irrigation scheduling in its simplest form of predicting
when to irrigate is practiced continually by all irrigators. The
scheduling criteria are often "judgment" oriented but are gener-
ally adequate. Modern scientific irrigation scheduling services
utilize soil moisture budgeting procedures to not only predict
the timing of the next irrigation, but also the necessary
quantities of irrigation water to be applied.
With various alternatives at each step, the irrigation
scheduling operation is basically a two step process. First, the
soil moisture status at the present must be updated from the last
date when it was known. This procedure involves adjusting the
potential evapotranspiration calculated from the Penman or
Jensen-Haise equations for crop, growth stage, and soil moisture
stress and including irrigation and precipitation in the update
interval. Because the soil moisture is being updated rather than
predicted, actual field and climatic data are used. The second
step is to determine the date of the next required irrigation and
66
-------
o
TJ
E
E
LJ
o
cr,
c
o
C
O
CL
O
LJ
^O
"c
a>
"o
a.
12 -
II -
10
9
8
7
6
5
4
3
2
I
Measured, 1040 mm
Total
^ 0
A Calculated, 1037 mm
Total
15 25 5 15 25
I 1,1 l
1525
Apr May Jun Jul Aug Sept Oct Nov Dec
Figure 24. Comparison of lysimeter data with the Jensen-Haise
estimate for alfalfa in 1975.
67
-------
>v
o
•o
£
6
UJ
o>
c
o
Q.
to
C
o
Q.
O
UJ
"g
"c
0>
o
Q.
O
•4—
12
II
10
q
*J
8
7
6
5
4
3
2
£ I
0
| ' 'M I | I I I I I | I I I I I | I I I I I | I I I M | I I I I I | I I I I I
Measured, 1040 mm
Total
^Calculated, 1024 mm
Total
!.'.'J ' i ill J M .1i i I Hi i ill M I ill
« IX J« " '_' • —^- • • • • L 1 1 I 1 1 I I II I I I I I
5 IS 25 S 15 25 9 15 25 5 IS 29 5 IS 25 5 15 25 9 IS M 5 15 25 5 15 25
Apr May Jun Jul Aug Sept Oct Nov Dec
Figure 25. Comparison of lysimeter data and the Penman
equation estimate for alfalfa in 1975.
68
-------
the amount it should involve. This analysis is based on
anticipated climatic and crop water use data.
Updating the Soil Moisture Status
In general, the availability of moisture in a crop root zone
must be periodically calculated rather than measured to insure a
reliable estimate of the depth and timing of future irrigations.
Measurements, of course, are preferable but cannot be made with
sufficient frequency. Consequently, the soil moisture storage at
the present is determined by starting at the beginning of the
update period and sequentially deducting the evapotranspiration
from soil moisture. This procedure assumes the conditions at the
beginning of the period are known.
The first step in updating the existing soil moisture
storage is the calculation of actual evapotranspiration. Begin-
ning with the potential evapotranspiration of alfalfa, Etp (from
Equations 23 and 24) , a crop coefficient kco is defined such that:
Et - kcoEtp
where E.J. is the potential evapotranspiration of the particular
crop at the point in time encompassed by the update period. The
value of Et depends also on the availability of soil moisture and
decreases as the depletion increases. Jensen (1973) and Kincaid
and Heerman (1974) define a stress coefficient:
log[l + 100(1 - D /DT)]
ks - - log 101 P .......... <27>
in which,
k = stress coefficient;
S
D = actual soil moisture depletion, in mm; and
D_ = field capacity, in mm.
Whenever a rain or an irrigation occurs, the actual evapotran-
spiration is actually increased somewhat due to free water at the
crop and soil surface. To account for this, an additional
quantity of evapotranspiration is added to E as follows:
Etr = kr(0.9 - kCQks) Etp ............ (28)
where
E. = added evapotranspiration due to rain or irrigation,
mm/day;
k =0.8 for first day following rain or irrigation;
=0.5 for second day;
=0.3 for third day; and
= 0.0 for other days.
69
-------
If the value of kcoks is greater than 0.9, Etr is set equal to
zero. Thus/ the actual evapotranspiration of a given day is:
Et - 'kcoks + kr<°-9 - kcoks)]Etp ........ <29>
In order to compute the value of the stress coefficient, ks,
the values of soil moisture depletion must also be known. This
involves two factors. First/ as the roots grow in the early
season, more and more available soil moisture is added to the
system:
DT(t) = (MC) [RDi + (RDm - RD^-r] ........ (30)
in which,
DT(t) = field capacity of the root zone with time, mm;
MC = moisture content at field capacity, mm/m;
RD. = initial rooting depth, m;
RD = maximum rooting depth, m; and
r = interval of the planting date to present divided
by the time between planting date and full crop
cover .
Then, the soil moisture depletion on a day i is written,
Dp(t) = D (t-1) + Et - R± (31)
where,
D (t) = soil moisture depletion, mm; and
R^ = rainfall or irrigation on the day.
The value of Dp substituted into Equation 27 for a day i is
usually the value D (i-1).
Predicting the Next Irrigation
Once the soil moisture system has been updated to the
present, and assuming the soil moisture has not already reached
the level when an irrigation should be initiated, the next step
is to determine when and how much to irrigate. Because real time
climatic data or soil measurement are not yet available, the root
zone budgets must be projected into the future until the soil
moisture level at which an irrigation should occur is determined.
These calculations occur in the same order as the updating
analyses except the daily evapotranspiration potential (Etp) is
replaced by the long term average E^-a. In the Grand Valley, for
example, the calibrated Penman and Jensen-Haise equations were
applied using mean climatological data resulting in the
relationship:
70
-------
Eta = 8'51 exp-[(Day-137)/ADay]2 (32)
in which,
E. = mean potential values for E. , mm/day;
Day = present modified Julian date (Mar. 1=1); and
ADay = 90 if Day >_ 137 and 120 if Day < 137.
When the date of the next irrigation is determined, the
amount to apply at that point will equal the allowable depletion
(depletion when irrigation is to be initiated) divided by the
irrigation application efficiency. The application efficiency
depends on the irrigation method and the practices followed by
the irrigator. This latter aspect will be covered in the
following sections.
Implementing Irrigation Scheduling
There have been numerous irrigation scheduling studies
reported in the literature. The necessary parts of a scheduling
program in a salinity control effort are discussed by Skogerboe
et al. (1974b) and will not be repeated here. One aspect,
however, should be noted in this section since it will become
important in the discussion of irrigation uniformities in later
sections.
An irrigator does not wish to see parts of his field
"burning" for lack of soil moisture. Consequently, the field is
usually irrigated until the least watered area is adequately
refilled. An irrigation scheduling program which monitors soil
moisture to update and monitor computer simulations will over-
estimate the interval between irrigations (as decided by
irrigators) and underestimate the time water needs to be applied
to the field if it evaluates soil moisture status at a location
other than at the minimum irrigated area. For surface irrigated
systems, soil moisture should be monitored near the end of the
fields, whereas pressure irrigated systems are least watered in
the center of the lateral emission points.
71
-------
SECTION 7
GENERAL CONSIDERATIONS IN IRRIGATION
Approximately one-fourth of the total cultivated land in the
world/ which is about 162 million hectares are presently irri-
gated (Israelsen and Hansen, 1967). Historically, civilizations
have been dependent on the development of irrigated agriculture;
and in many of these same areas today, irrigation still provides
the agrarian basis of society.
However, when the constraints of the entire soil-water-plant
relationships are ignored either through ignorance or lack of
planning, an irrigated agrarian industry will eventually
disappear. A good example is the ancient civilization of
Mesopotamia which flourished in the Tigris-Euphrates Valley 6,000
years ago (Kang, 1972). In 2,000 years the soil became so saline
due to poor irrigation practices and lack of drainage that it has
not recovered to this day. It had been estimated that Mesopotamia
supported as many as 25 million persons. Iraq, which presently
occupies much of this same area, today has a population near 10
million. In fact, the tax records from Mesopotamia show that
barley yields were about 2500 liters/ha, whereas present yields
in this area are only one quarter to one half of this value
CKovda et al., 1973).
When a reliable and suitable supply of water becomes
available for agriculture in a previously dry area, it immedi-
ately results in vast improvements in agricultural production and
assures economic returns to the grower. However, in time,
without proper agronomic practices accompanying the irrigation,
these lands will become unproductive and barren. These "proper"
agronomic practices can include drainage, fertilization, crop
rotation, soil reclamation and management, erosion control, and
the selection of crops best suited to local conditions. All of
these considerations must be integrated into the practice of
irrigation to realize the full potential of irrigated agricul-
ture, which can be many times the initial advantage of irrigation,
OBJECTIVES OF IRRIGATION
Irrigation in arid areas of the world has two primary
objectives: (a) to supply the essential moisture for plant
growth; and (b) to leach (wash out) or dilute chemical salts in
72
-------
the soil. Irrigation water has a side benefit, cooling the soil
and the atmosphere thereby providing a more favorable environment
for plant growth. Irrigation supplements the supply of water
received from precipitation and other types of atmospheric water,
flood waters, and groundwater.
The first objective of supplying the necessary moisture can
be accomplished in several ways. However, regardless of the
method used, the purpose of irrigation is to periodically
replenish the "soil moisture reservoir" of the plant's root zone.
This reservoir is depleted by the consumptive demands of the
plant. The only existing method of irrigation which is an
exception to this rule is drip or trickle irrigation, which
starts with a full root zone reservoir and directly replaces the
water consumed by the plant on an almost daily basis, instead of
waiting until the available soil moisture has been depleted by a
specified value (usually 50 percent to 70 percent of the differ-
ence in soil moisture holding capacity of the root zone between
field capacity and wilting point).
Salts are contributed to water supplies by two main
processes: salt concentrating and salt loading. Salt concentra-
tion effects are due to the removal of water by the consumptive
use of crops and other natural vegetation, the interbasin export
of high-quality water, and the evaporation from the water
surfaces of streams and lakes. As this "pure" water is depleted
from the system, the mineral constituents left behind increase
the concentration in the remaining flow. Salts contributed by
salt loading are due to the chemical weathering of soil and
substrata by irrigation water and natural subsurface flows. Salt
loading is also caused by excessive fertilizer applications,
municipal and industrial wastes, and point sources such as
mineral springs, flowing brine wells, and geysers.
If the salts left behind in the root zone as a result of
evapotranspiration are not periodically leached from the crop
root zone, the land will become unproductive. This second
objective of irrigation is very important and often will occur
naturally during an irrigation. However, the water which passes
through the root zone carrying the excess salts is often severely
restricted from further travel by subsurface conditions. When
this occurs, this leachate will eventually build up into the root
zone causing high salinity levels and poor aeration (water-
logging) . This phenomenon, in fact, has been the downfall of
many great historic civilizations. Today, however, this water-
logging problem can be alleviated with proper drainage control
measures or improved irrigation water management practices. For
this reason, drainage should be considered as an integral part of
any irrigation development project and not as an afterthought.
Another serious problem of irrigated agriculture is soil
erosion, where top soil and soil nutrients are carried by
73
-------
tailwater into the reservoirs, canals, and laterals of downstream
users. Siltation reduces the capacities of drainage and irriga-
tion channels, resulting in costly large-scale maintenance
programs and the installation of expensive structures for its
removal. The useful lifetime of dams and reservoirs is often
computed in terms of the rate of sedimentation.
SOIL-WATER-PLANT RELATIONSHIPS
Soil, water, and plant relationships of particular importance
to irrigated agriculture include: (a) the capacity of the soil
to hold water and still be well drained; (b) the flow character-
istics of water in the soils; (c) the physical properties of the
soil matrix including the organic matter content, soil depth,
soil texture, and soil structure; and (d) soil chemical properties
including the translocation and concentration of soluble salts
and nutrients due to the movement, use, and evaporation of the
soil water. Knowledge of all these relationships and how they
influence each other is critical to all who desire to improve
irrigation practices and obtain the best, most efficient use of
water.
Soil Moisture
If there is either excessive water (waterlogging), or
insufficient water, crop growth will be retarded. While irriga-
tion is an artificial means of adding to the available soil
moisture to prevent moisture deficiencies, poor irrigation
practices create the waterlogging problem. As commonly defined,
the available moisture is that which is held in the soils at a
negative apparent pressure range from one-third bar (field
capacity) to 15 bars (permanent wilting point). However, the
available moisture content within this pressure range will vary
from 25 cm per meter of soil depth (3 in/ft) for some silty loams
to as low as 6 cm per meter of soil depth (0.75 in/ft) for some
sandy soils. As a consequence, the soil type can greatly influ-
ence irrigation management practices. The percentage of water at
the permanent wilting point is usually about half of that at
field capacity, but still much greater than the water content of
air dried soil.
When the available soil moisture is in the range below a 50
percent to 70 percent moisture depletion and approaching the
permanent wilting point, the limited water supply will play an
important role in retarding plant growth. When a plant becomes
"stressed" due to the influence of these soil water deficits,
there are several changes in the physiological processes of the
plant. If these stresses occur during a critical stage such as
flowering or fruiting (these "critical" stage (s) will vary from
plant species to plant species), the crop yields can be severely
74
-------
reduced. If the plant is stressed below the permanent wilting
point, it will probably not recover.
Soil Hydraulic Characteristics
A property of soils which is extremely important to
irrigated agriculture is the rate of infiltration or the time
rate at which water will percolate into the soil. It is influ-
enced by chemical and physical soil properties and the hydraulic
gradient. The configuration of the soil surface (i.e., furrows
or borders), the slope, the roughness, and type of vegetative
cover will also influence infiltration. Whenever the surface
configuration influences the rate of water entry into the soil,
the term "intake rate" is used instead of the "infiltration rate."
Infiltration rates will vary from being relatively high at
the start of an irrigation to a much lower value at the end. It
can also vary throughout the irrigation season as is the case in
the Grand Valley (see Figure 20, Section 5). Water standing on
coarse or sandy soils will infiltrate rapidly, but water on a
very fine-textured clay soil may often stand for days, and the
evaporation rate can be higher than the infiltration rate. The
term cumulative infiltration (or depth of application), which
accounts for these time variations, is used to define the total
amount of water delivered to the root zone during an irrigation.
The depth of application is dependent on the length of run, total
time of application (total volume applied), and the volume rate
of inflow.
Soil Physical Properties
The soil matrix serves.several very valuable functions, not
the least of which is serving as a foundation to hold the plants
upright. It must also furnish nutrients and provide a good
balance between areation and available moisture content.
Soil texture and structure influences the intermolecular
forces and "suctions" of water in unsaturated soils. These
forces can be quite substantial and include the capillarity and
attractive forces resulting from the close contact of soil
particles. Soil texture, primarily soil structure, greatly
influences the distribution of pore sizes, and thereby the perme-
ability of soils to air, water, and roots which is as important
to crop growth as is an adequate supply of nutrients. In fact,
the entire soil-water-plant system is so interrelated that the
failure or lack of one component can cancel the combined benefits
of all the others.
The depth of soil is important because it establishes the
amount of water and nutrients which can be stored, as well as the
physical limits of the root zone. A deep soil is necessary to
75
-------
have a well-drained soil. Shallow soils directly influence tne
rate and depth of root growth.
Irrigation practices are influenced by the degree of root
proliferation since the water supply available to the plant is
limited to the distribution of and soil volume explored in the
crop's root system. Different crops have different root growth
patterns, hence, different moisture extraction patterns.
Obviously, a shallow-rooted crop will require more frequent
irrigations than a deep-wide-rooted crop, given the same soil
moisture holding capacity.
Soil Chemical Properties
The chemical properties of soils can greatly influence the
irrigability of the soil by affecting the hydraulic character-
istics and the suitability of the soil for crop production.
Soils having an excess of soluble salts are designated as saline
soils, and, if the soil has an excess of exchangeable sodium, it
is termed a sodic soil. Sodic soils tend to have very poor soil
structure due to swelling or dispersion properties which tend to
greatly reduce pore size distribution. This has an enormous
effect on the hydraulic properties of the soil. For example, the
hydraulic conductivity of a soil can change as much as three
orders of magnitude when the sodium adsorption ration (SAR)
is reduced from a value of 20 to 1, holding all other soil
properties constant (Dane, 1976).
Excess soil salinity will delay or prevent crop germination
and can substantially reduce the amount and rate of plant growth
because of the high osmotic pressures which develop between the
soil water solution and the plant. These pressures, which appear
to be independent of the type of salts present, greatly impair
the plant's ability to absorb water. In addition, some adverse
effects due to salinity can include nutritional imbalances or
toxicities caused by specific ions (i.e., boron which is toxic in
very small quantities). In sufficient concentrations, even
beneficial salts (fertilizers such as potassium nitrate) can
become toxic to plants.
In addition to the soil chemical characteristics mentioned
above, the soil must also have an adequate supply of available
plant nutrients. Many chemical elements are essential for plant
growth and are necessary to obtain large and satisfactory crop
yields. These include calcium, carbon, hydrogen, iron,
magnesium, nitrogen, oxygen, potassium, pnosphorus, sulfur, and
many other trace elements depending on the type of crop. The
availability of these nutrients to the plant depends to a large
extent upon the moisture content of the soil.
Bacterial activity is also an important part of the
soil-water-plant relationship because this action will often
convert nitrogen to a usable form (nitrogen-fixing). Bacterial
76
-------
action also breaks down organic matter and converts other chemi-
cal compounds into forms usable by the plants. Soil moisture
content, soil structure, and soil aeration directly influence
bacterial activity.
AGRICULTURAL INPUTS
The optimal objective of proper irrigation management is to
maximize efficiencies and minimize the labor and capital require-
ments of that particular irrigation system as much as possible;
and, at the same time, maintain a favorable growing environment
for the plant in order to maximize yields. Some managerial
inputs are dependent on the type of irrigation system and the
design of the system. For example, the degree of automation, the
type of system (sprinklers, trickle, or conventional surface
irrigation), the reuse of field tailwater, soil type, topography
variations in a field or farm, and the existence and location of
management tools such as flow measurement and water control
structures can influence the managerial decision making
processes.
However, management decisions which are common to all
systems, regardless of the types, are the frequency of irriga-
tion, depth of water to be applied, and measures to increase the
uniformity of applications such as land leveling or shaping. In
addition, individual systems can be manipulated to greatly
increase application efficiencies. For example, in furrow
irrigation some growers will use two siphon tubes per furrow at
the start of irrigation (wetting phase), and when the water has
reached the end of the row, one tube is removed (infiltration
stage}. This increases the efficiency by minimizing field
tailwater runoff; however, it requires an additional labor input.
This method of irrigation is called cutback furrow irrigation and
can be easily automated (Evans, 1977).
In recent years, irrigation scheduling services have aided
the farm manager with decisions on how much to apply and how
frequently. Irrigation practices such as preirrigations before
planting, irrigating plants up after planting, or the length of
time per set, are managerial inputs which influence water use
efficiency over the season.
CRITERIA FOR SELECTING METHODS OF IRRIGATION
There are a large number of considerations which must be
taken into account in the selection of an irrigation system.
These factors will vary in importance from location to location
and crop to crop, and a detailed explanation of all considera-
tions is beyond the scope of this report. Briefly stated, these
77
-------
considerations include the compatibility of the system with other
agricultural operations, economic factors, topographic limita-
tions, soil properties and many agronomic and external
influences.
Compatibility
The irrigation system for a field or a farm must be
compatible with other existing farm operations such as land
preparation, cultivation, and harvesting practices. For instance,
the use of the more efficient, large machinery requires longer
and wider fields with wider borders or perhaps even removable
irrigation systems.
Economic Considerations
The type of irrigation system selected is also an economic
decision. Some types of sprinkler systems have high per acre
costs and their use is therefore limited to high value crops.
Other systems have high labor requirements, and some have fairly
high operating costs. Also, some systems have limitations with
respect to the type of soil or the topography on which they can
be used. The expected life of the system, fixed costs, and
annual operating costs (energy, depreciation, taxes, etc.) should
also be included in the analysis when selecting an irrigation
system.
The type and relative cost of power, and availability and
quality of labor, also enters into the type of system to be used.
The type of power could be electricity (phase, voltage, and
horsepower limitations), or internal combustion engine (fuel
type, cost and availability). These factors and others determine
the cost of the water supply.
Topographic Limitations
Restrictions on irrigation system selection due to
topography include groundwater levels , the location and relative
elevation of the water source, field boundaries, acreage in each
field, the location of roads and natural gas lines, electricity
and water lines and other obstructions, the shape of the field,
and the field slope (which can vary dramatically over a field).
Field surface conditions such as relative roughness and gullies
should also be considered.
The slope of the land is very important. Some types of
sprinklers can operate on slopes up to 20 percent or more, but
furrow or graded border irrigation is usually limited to a
maximum slope of around 2 to 6 percent. Trickle irrigation can
be used on slopes up to 60 percent or more.
78
-------
The shape of a field also determines the type of system.
For instance, level borders, furrows, hand-move or solid-set
sprinklers, subsurface, contour ditch, or trickle irrigation
systems can be adjusted to fit almost any field shape; whereas,
a center-pivot sprinkler must have approximately round (or
elliptical) shaped fields. For a side-roll sprinkler, level
furrow, graded border or contour furrow, the field should be
approximately rectangular in shape.
Soil Characteristics
The soil type, soil moisture holding capacity, the intake
rate, and effective soil depth are also criteria which enter into
the type of system selected. For example, sandy soils have a
high intake rate and will accept high volume sprinklers which
would be unacceptable on a tight clay soil.
The moisture holding capacity will influence the size of the
irrigation sets and frequency of irrigations as evidenced by a
sandy soil with low moisture holding capability which requires
frequent, light applications of water. A center-pivot or side-
roll sprinkler or even a trickle irrigation system would perform
satisfactorily in this case.
Other Considerations
Most surface systems, drip irrigation, and some sprinkler
systems can be used for fertigation (fertilizing through the
system) and chemigation, as well as the land application of
municipal and animal wastes. However, there exist advantages as
well as limitations on all systems which should be understood
before implementation.
Some sprinkler systems can be used for frost and freeze
protection and for cooling of crops. Such systems are relatively
expensive and are usually limited to high value crops such as
vegetables, vineyards, and orchards. With sprinklers, the height
of crop can be a significant factor for uniform application since
the sprinklers should generally be above the crops.
External Influences
At times, conditions external to agriculture can influence
the type of system selected. For example, an underground pipe-
line might be required by municipal ordinances, safety and/or
aesthetics if the delivery system passes through an urban area.
Other considerations might include the quality of irrigation
return flows and the quality of incoming water. Also, irrigation
efficiencies might have to be maintained at specified levels as a
result of litigation.
79
-------
IRRIGATION BENEFITS
In 1976 there was almost 23 million hectares (57 million
acres) of irrigated land in the United States, a 4.4 percent
increase over 1975 (1975 had a 2.5 percent increase over 1974)
(Irrigation Journal, 1976). Most of this increase is occurring
in the Midwest and Southeast to supplement natural rainfall.
Irrigation at the optimal time in these areas can increase corn
yields by 50 bushels per acre (2,000 kg/hectare) and 10 to 20
bushels per acre (430 to 860 kg/hectare) for soybeans (Irrigation
Age, 1977). These production increases can be obtained by the
installation of a properly designed and operated irrigation
system.
In 1967, the President's Panel on World Food Supply
estimated that only 44 percent of the potential arable lands in
the world are under cultivation (President's Science Advisory
Committee, 1967). If this land will be put into production, it
will be largely the result of irrigation. Also, it is inter-
esting to note that while only approximately 10 percent of the
United States cropland is irrigated, more than 25 percent of the
annual agricultural production is credited to this acreage.
As mentioned above, irrigation benefits are derived from
minimizing plant moisture stress resulting from long or short
duration droughts which occur even in areas where the annual
precipitation is greater than the evapotranspiration. In short,
irrigation reduces risk. This is especially true in arid areas
such as the Grand Valley, where irrigation can literally turn a
desert into an oasis.
Due to the increased production capabilities and the reduced
risk potential of irrigated land, land values also appreciate.
Land which is worth as little as $25-50 per acre ($60-120/hectare)
without irrigation can be worth as much as $3,000-5,000 per acre
C$7,200-12,000/hectare) with irrigation.
A well-designed irrigation system combined with proper soil
and water management can often improve the quality of the soil as
compared with its natural condition. For example, in most soils,
the organic matter from decaying roots and mulches can increase
the moisture holding capacity. In addition, irrigation can leach
naturally saline soils to levels where large crop yields can be
obtained.
80
-------
SECTION 8
FURROW IRRIGATION
DESCRIPTION OF FURROW IRRIGATION
Furrow irrigation is a method of water application
accomplished by diverting flows into small channels which
traverse the field slope. In irrigated fields, these closely
spaced channels are referred to as furrows, rills, creases, or
corrugations. As the irrigation water flows in the furrows, the
infiltration into the bottom and sides of the furrow is redis-
tributed in the crop root zone for later consumptive utilization.
Efficient furrow irrigation requires that the inlet
discharge and the duration of the irrigation be carefully
coordinated with the field slope, furrow geometry, infiltration
capacity of the soil, and the soil moisture holding characteris-
tics. Crops which are subject to crown or stem injury if covered
with water are often irrigated by furrows. This method is also
well suited for crops which are planted and harvested in rows.
The two-dimensional soil moisture movement condition is advan-
tageous in not only minimizing the wetted surface area but also
in the movement of fertilizers and pesticides toward the central
root zone. The furrows are often used by irrigators in con-
trolling the distribution of water over a field that is not
uniformly graded.
The driving force for furrow irrigation is gravity, but the
subsequent redistribution of soil moisture and evapotranspiration
are functions of many soil-plant-atmospheric parameters. The
water application itself, however, can be divided into three
phases: (a) advance; (b) wetting; and (c) recession. For the
normal practice of irrigating when the soil moisture reservoir
has been depleted 50-75 percent, the recession phase is compara-
tively insignificant (Fok and Bishop, 1965). Infiltration at a
specific point along the furrow begins at the moment the
advancing water front reaches the point (advance phase) and
continues as long as water remains in the furrow (wetting phase).
When the discharge at the head of the furrow is terminated, the
flow recedes down the field until reaching the end (recession
phase).
81
-------
Because irrigation with furrows is a widely used method of
applying water to crops, the evaluation of the technique has been
detailed by a number of investigators. The results of many of
these studies, however, employ different assumptions because of
the difficulties in interrelating the surface hydraulics and
intake phenomena of the soil. Two basic mathematical approaches
have emerged. The first is the hydrodynamic approach using
continuity of mass and momentum to predict the advance-recession
phases (assuming the infiltration characteristics are known).
The second is the volume balance or kinetic approach. In
general, the hydrodynamic approach is too time consuming and
complex for generating a sufficient number of solutions to be
practical. Also, the large spatial variability in soil and
furrow properties render a totally theoretical description
somewhat out of scope with actual field conditions. The volume
balance approach, however, is not only simple to solve but also
is based on easily measured field data. The literature de-
scribing the volume balance approach is very large and has been
well summarized by Gerards (1978) and Karmeli et al. (1978). In
this report, a summary of their works will be utilized as a basis
of explanation and the more interested reader is directed to the
original references for more explicit development.
BASIC FURROW HYDRAULICS
The evaluation of a furrow irrigation system involves a
number of alternative approaches as noted earlier. For the
purpose of this report the primary analysis will be based on the
information collected on a field scale and the subsequent use of
these data in the evaluation. The problem is two-fold. In the
initial stages of design or evaluation, the first investigative
efforts are oriented toward definition of the infiltration rela-
tionships. Later, with a knowledge of intake characteristics,
the advance and uniformities are predicted.
Field Evaluation of Infiltration
Infiltration of water into the bottom and sides of a furrow
is a two-dimensional process, the magnitude of which depends on
depth of flow, furrow shape, and type of soil. Therefore,
accurate information regarding infiltration characteristics may
be obtained under actual flowing conditions or using a number of
available on-site measurement techniques (blocked-furrow infil-
trometers, inflow-outflow measurements, and cylinder infiltrom-
eters). There are limitations associated with each procedure
which may be identified.
The only technique using flowing conditions is known as
infiltration determination based on rate-of-advance data. This
approach is based on the principle of kinematics or volume-
balance and requires accurate knowledge of the water introduced
82
-------
at the head of the furrow (Vq) and the volume of storage in the
furrow at any time (Vs) .
The primary element in surface irrigation evaluations is
definition of soil intake or infiltration rates. Many empirical
equations have been proposed, but the most commonly employed is
the relationship introduced by Kostiakov (1932) :
i = atb .................... (33)
where ,
i = infiltration rate in cm/min;
t = interval since infiltration began, in minutes; and
a,b = empirical regression coefficients.
Integrating Equation 33 over the irrigation interval yields:
I = - tb+1 = AtB ............... (34)
in which I is the cumulative soil infiltration in centimeters.
Because the intake opportunity time varies in a field due to
the time required for water to reach a point, the infiltrated
depth over a field's length will also vary. Thus, if tx is the
time required for the water to advance to the distance x and t
is the total time water is introduced into the field, then
Equation 34 should be written:
I = A(t£ - tx)B ................. (34a)
A commonly employed function expressing the relationship between
the advance rate and time is:
(35)
where ,
x = the distance along the flow path, in meters (m) ;
t = time to advance x meters, in minutes; and
p,r = empirical regression coefficients.
Actually, the parameter r can be approximated without field data
if the infiltration exponent, B, is known (Fok and Bishop, 1965):
r = exp(-0.6B) .................. (36)
Generally, however, r is determined by field data enroute to
defining B. Because equation 35 is an exponential function, the
slope r can be determined by knowing two points on the curve, say
the time required to reach the end of the field, tT , and the
LI
83
-------
time necessary to advance one-half the field length, O.St..,
r = 0.69/ln T ................. (37)
in which:
.................. (38)
Work reported by a number of investigators suggests that r
is primarily dependent on the infiltration rate slope b (or B) as
suggested by Equation 36. The parameter p, however, depends on
the inflow, slope, roughness, and furrow geometry. Data have
been reported which tend to substantiate these conclusions, but a
well verified general predictive capability for p has not been
published so far as the writers now know. Consequently, values
for p must be determined for each irrigation test.
The volume of water infiltrated into the soil per unit width
after the inflow has proceeded to some time is written:
X,
V£ = 10~2 I I dx (39a)
Substituting the expression for I (Equation 34) into Equation 39a
yields
= 10~2-A [ (t£-tx)B dx (39b)
in which,
V = total infiltrated volume into the wetted furrow
length a after t^ minutes, m^/m;
£, = length of furrow wetted as determined by equation 35,
in meters; and
t = total time water was introduced into the furrow,
in minutes.
Noting that the limits of integration in Equation 39b must be
changed,
dx = (I*-) dtx = r-p-t*"1 dtx (40a)
j£
I = 0 , t = 0
* (40b)
84
-------
t
= 10~2-A-r.p [ (t£-tx)B t^"1 dtx (400
The solution to the integral in Equation 40c can be found by
modifying the structure somewhat. Specifically, let,
(41a)
so that by dividing terms by t£ and rearranging,
1
V£ = 10~2-A-r.p.t^+r j (l-t)B t1"1 dt ...... (41b)
0
The solution of Equation 41b can be found in any standard
table for definite integrals and equals,
— --
V£ = 10 •A-p-t -r-B (B+l,r) .......... (42)
where the beta function, r-3( )/ can be approximated by the
relationship (Christiansen et al., 1966):
r-B(B+l,r) =
rb - br +.. 2,
(r+lj (43)
To evaluate the coefficients A and B in Equations 34 and 42,
a mass balance in the furrow can be written. In this case,
assume the total time of application is such that the water just
reaches the end of the furrow U=L, the furrow length). The mass
balance is maintained by equating the furrow inflow and the
volume remaining in surface storage to the volume infiltrating
the soil:
V. = (V - V )/w (44)
X CJ o
where, ^
V. = volume infiltrating the soil at some time, m /m;
1 3
V = volume introduced into the furrow, m ;
q 3
V = storage in the furrow, m ; and
s
w = furrow spacing, in meters.
Generally, the furrow inflow, Vg, is measured with small
flumes or weirs leaving two unknowns in Equation 44. Wilke and
Smerdon (1965) proposed that the average cross-sectional area of
the flow could be described by an exponential function of normal
depth, d :
85
-------
Af = M d .................... (45)
in which, 2
Af = average cross-sectional area of the flow, cm ;
dQ = normal depth, in meters;
M =8.59; and
N = 1.67.
The expression of flow area as a function of normal depth assumes
that the shape of the furrow is known and that the relative shape
of the flow profile remains the same along the entire furrow
length. Given the variability in surface irrigation, the values
of M and N should be determined for each test. The normal depth
can be determined by the Manning equation. Wilke and Smerdon
(1965) used a roughness coefficient of n=0.047, thereby arriving
at dQ as:
d0 = O.eOtQX/S^)* ............... (46)
where ,
Q = flow rate, 1/min; and
SQ = field slope in percent.
If Equation 42 is utilized to describe V^ and Equations 35 and 45
to represent V , then Equation 44 can be written:
s
-2 B+r Vcr ~ X. -A.-lfl"4
10 ^-A-p-t^ (3(B+l,r+l) = -3 - V^ - - • • <47a>
JL Vf
in which,
t. = time at which mass balance is made; and
x. = distance the flow advances in t. minutes, in meters.
Solving for time,
B+r Va~xi V10~4
A-tB+r = - ^ - .......... (47b)
1 10 •wp«B(B+l,r+l)
When Equation 47b is evaluated for various values of advance
time, 0
-------
measurements derived from other techniques. Thus, the problem of
spatial variability at least along the furrow is appropriately
addressed and the variability across the field can be determined
by investigating a number of furrows. And secondly, the data
necessary to calculate infiltration are easily determined. The
investigator diverts a known and constant discharge into the
furrow, notes the times until the flow has advanced one-half the
field length and the field length, and measures the cross-
sectional area. These data along with the field slope and length
allow evaluation of the soil intake characteristics.
As with any field evaluation technique, however, this method
has a number of weaknesses. The volume of actual field data for
verification of the approach is inadequate and the sensitivity of
the predictions to the various assumptions has not been deter-
mined. Consequently, the estimation of surface storage must be
studied further. Specifically, the estimation of average cross-
sectional area and the flow depths along the furrow require on-
site measurement if possible until the experimental data base
becomes large enough to generate verified relationships. It
should also be noted that the values of a and b in Equation 33
depend on the discharge introduced into the furrow since the
normal depth will be greater. A similar effect will occur as a
result of furrow length. The longer the furrow, the less Equa-
tion 34 will apply. One aspect of infiltration seldom addressed,
but of major importance, is the general decrease in intake rates
through an irrigation season due to the effects of previous
irrigations and tillage practices. The frequency of irrigations
is also an important variable because of the moisture content-
hydraulic conductivity function of which Equation 33 is in a
sense an approximation.
Predicting Application and Field Efficiencies
A fairly intensive effort has been devoted in recent years
to accurately predicting the soil moisture depletion in irrigated
fields. The experimental and commercial data currently available
suggests that both the timing and the necessary amounts of water
to apply can be reasonably well estimated. Accomplishing the
scheduling recommendations, however, is another matter in furrow
irrigated areas. If the infiltration characteristics have been
evaluated over the range of commonly encountered conditions, and
the field topographic and operational characteristics are known,
the efficiency of irrigations under alternative regimes can be
predicted.
This analysis begins with the definition of the depth of
moisture needed to refill the crop root zone, D, in cm. Then
from Equation 34, the time necessary to infiltrate the desired
depth is:
tD = (D/A)1/B (48)
87
-------
where tD is time in minutes water must infiltrate at a specific
point to replace the depth D in the root zone. Because the
intake opportunity time varies between the beginning and end of a
furrow, the actual infiltrated depths also vary. Three cases for
the furrow irrigation regime may be detailed: (a) the under-
irrigated case where some of the lower reaches are not completely
refilled (Figure 26a); (b) the case where the minimum irrigated
area is just refilled (Figure 26b); and (c) the general over-
irrigated case (Figure 26c).
The earlier discussion regarding the infiltration evaluation
covered only the part of the irrigation encompassed by the
advance phase, i.e., the period until the furrow stream reaches
the end of the field. Actually, the analysis is valid for
periods longer than the time required to advance the field length
by assuming that the furrow extends indefinitely. Thus, if the
total time water is applied to the furrow (set time) is again
represented by t£, (tA>tL) the length of advance predicted by
Equation 35 would be:
X- = ptj (49)
where l is the total "equivalent" field length, in meters. The
volume of infiltration over the length SL, VA, is determined from
Equation 42.
Referring to Figures 26a, 26b, and 26c again, it is seen
that in order to compute the volume of deep percolation and
tailwater, Equation 41b must actually be solved for various
fractions of t£. For example, for any time t1 such that
0
-------
Figure 26,
L= Field Length, m
£ = Advance Distance During
Irrigation Interval , m
1= Depth of Infiltration, cm
--- Root Zone Soil Moisture
Holding Capacity, cmVcm
Definition sketch of surface irrigation application
uniformity for a) the case where part of the field is
underirrigated, b) the case of zero underirrigation,
and c) conditions of significant overirrigation.
89
-------
M1 = r I (l-t)B t*'1 dt = eRr (51)
0
where M1 is an incomplete beta function related to the upper
limit of integration R.
e = 0.9598 exp(-0.3383B) (52)
and,
f = 1.0170 exp(-0.9763B) (53)
The maximum error, (eM,), between Equation 51 and the 800 incre-
ment numerical solution was -1.7 % <_ eM, <_ 2.7 %. It should also
be noted that the parameter r was eliminated by assuming that the
relationship in Equation 36 was valid.
It is now possible to utilize the preceding analysis to
compute the irrigation efficiency for a furrow system. To do
this, two specific subsets of irrigation efficiency are defined.
The first, application efficiency, AE, is:
= root zone storage
~ total infiltrated volume
A' + A'
L ,. ^ ,, x 100 (54)
Al + A5 + A2
The second, field efficiency, FE, is:
PE = root zone storage
total field deliveries
A1 + A'
= A' + A* + A^ + A' X 10° (55)
*» 1 ' ** f\ * ** *^ * *1 r—
Note that where the least irrigated areas along the furrow are
just refilled, Al and Al are equal to zero.
Values for the respective segments of the infiltrated and
runoff volumes along a furrow are determined using the solutions
to Equation 50 as follows:
Al = XD*D/ XD - L (56)
A' = 10~2-A-p-t*f+r-M' - A' (57)
t £ RD 1
90
-------
A£ = 10 -A-p-t -M£ - AJ - AJ, XD <_ L . . . . (58)
L
A£ = 0, XD >_ L (59)
A^ = L-D - A£ - A£, XD < L (60)
A4 = °' XD >_ L (61)
-i ft~ 2 ,. „ . B-fr, b-br+2 , „ , ,. . ,. , //-o\
= 10 -A-P-t [] - Ai - A2 * A5 • ' (62)
where,
*D
^ = r (l-t) t- dt, RJJ = tjj/t^ ..... (63)
and
RL
ML -
R dt' RL - Vfc£ ..... (64)
Equations 56-64 can be utilized to develop some general
efficiency curves as shown in Figures 27 and 28 (Gerards, 1978) .
EVALUATION OF FURROW IRRIGATION IN GRAND VALLEY
The data collection program discussed by Evans et al. (1978)
resulted in an average f irst-of-season cumulative intake function
(Equation 34) of:
I = 7.82t°*40 .................. (65)
when t is in units of hours rather than minutes. Data collected
during the 1977 irrigation season by Gerards (1978) have resulted
in a slightly lower value of the exponent B (0.33), but the
average value as determined in equation 65 falls within the range
characterized in the Valley. The existing value of A (7.82
cm/hr) is thought to be fairly representative. Evans et al.
C1978) listed two equations describing the general decline in 24
hour cumulative intake:
and
Ir = 0.999 - 0.2245'N + 0.02089-N2 (66)
Ir = 0.3067 + 0.7032/N2 (67)
91
-------
100
90
80
O
c
tt)
•*= 70
LU
c
o
o.
a.
60
50
t0=Time Required to Infiltrate Desired
Depth D into Soil
tu= Time Required for Water to Reach
Lower End of Field
8
Figure 27. Application efficiency relationship for furrow irrigation
for the case of zero underirrigation (after Gerards, 1978)
-------
c
0)
0)
100
80
60
40
20
tD= Time Required to Infiltrate Desired
Depth D into Soil
tL= Time Required for Water to Reach
Lower End of Field
0^6
—— 0.4
8=0.8
to'tL
Figure 28. Field efficiency relationships for furrow irrigation
for the case of zero underirrigation (after Gerards,
1978) .
93
-------
where,
I
= relative 24 hour cumulative infiltration; and
N = number of previous irrigations plus 1.0.
Equation 66 was given as an approximation for perennial cropped
fields, whereas Equation 67 was for annual crops. Gerards (1978)
concluded that the decline in infiltration rate could almost
totally be lumped in the A coefficient of Equation 34. Thus,
rewriting Equations 65, 66, and 67:
and,
I = 7.82(0.999 - 0.2245»N + 0. 02089'N2) t°*40
I = 7.82(0.307 + 0.703/N2)t°'40
(68)
(69)
Field data collected by Gerards (1978) on both advance and
infiltration showed that,
r = 0.977 exp[-0.63B] .............. (70)
which is reasonably close to the Fok and Bishop (1965) approxi-
mation. The results of evaluating p in Equation 35 were less
specific, but yielded the expression:
p = u-q
s
(71)
where ,
Q
u
s —
furrow inflow in liters/minute;
factor ranging from 0.1 to 0.2 for the Grand Valley
conditions studied; and
factor ranging close to 1.0.
Evans et al. (1978) presented three curves describing the
time dependent values of application efficiency under typical
Grand Valley conditions. These functions assumed uniform water
distributions and, therefore, overestimate actual efficiencies
5-10 percent. Using the relationships reported in previous
paragraphs, the writers recomputed application and field effi-
ciencies taking uniformity into account. These results are
shown in Figure 29 as the dashed lines (the solid lines are the
original functions presented by Evans et al., 1978). A summary
of the calculations are given in Table 6.
ALTERNATIVES FOR IMPROVING FURROW IRRIGATION
The annual average application efficiency in the Grand
Valley according to Walker et al. (1977) is approximately 64
percent. Table 6 indicates that if the irrigations were managed
so that the minimally irrigated areas at the bottom end of a
field were not overirrigated, the resulting average application
94
-------
lOOr
50
Alfalfa Orchards
Pasture
j_
j_
j_
0 100
>»
o
c
0>
o
i: 50
c
o
o
o
Q.
Q.
0
100
rfL • I
Attainable
Actual
Corn
Small Grains
50
0
Sugar Beets
0 2 4 6 8 10
Irrigation Number
Figure 29.
Seasonal distribution of computed application
efficiencies for common crops grown in the
Grand Valley.
95
-------
efficiencies would approach 85 to 90 percent. Field efficiencies
will continue to be low, averaging about 36 percent under the
well-managed cases.
TABLE 6. FIELD EFFICIENCY CALCULATIONS FOR
A TYPICAL GRAND VALLEY FIELD
Irrigation
No.
A
D
(cm)
(hr)
(hr)
*
0/'L
AE
FE
Annual Crops
1
2
3
4
5
6
7
8
7.
3.
2.
2.
2.
2.
2.
2.
82
71
95
69
57
50
50
50
9
9
9
9
9
9
9
9
1
9
16
20
22
24
24
24
.42
.12
.26
.48
.95
.59
.59
.59
8
4
4
4
4
4
4
4
0
2
4
5
5
6
6
6
.18
.29
.07
.12
.14
.15
.15
.15
50
90
92
93
94
95
95
95
65
47
40
33
30
30
30
30
Perennial Crops
1
2
3
4
5
6
7
6.22
4.95
4.02
3.40
3.12
3.12
3.12
11
11
11
11
11
11
11
4.16
7.36
12.39
18.83
23.34
23.34
23.34
6
4
4
4
4
4
4
0.69
1.84
3.10
4.71
5.84
5.84
5.84
73
87
91
93
94
94
94
55
50
44
33
30
30
30
In order to improve application efficiencies in the Grand
Valley, two steps require attention. First, irrigation sched-
uling should be based on updating the soil moisture conditions in
the lower ends of the fields. These data would indicate the
minimum depth of irrigation to be applied and the total time
water should remain in the field after it has reached the end of
the furrows. This procedure, if followed, would achieve the 85
to 90 percent efficiency described as attainable above. The
second step in improving application efficiencies involves more
frequent irrigations during the first month of the irrigation
season. More frequent water applications imply much lower (and
linear) infiltration rates, thereby maximizing the uniformity of
the irrigation and minimizing the differences between the upper
and lower ends of the fields. In looking at Table 6 and com-
paring tD and tL, the added labor by the irrigator can be
determined. As an example, consider the annually cropped field
irrigated consistently in 4-24 hour sets. To reach the 85-90
percent application efficiency, the set times need to be tD+tL.
96
-------
Thus, during the first irrigation, the field should be irrigated
in 40 hours rather than the usual 96 hours (an increase in labor
of 96/40 = 2.4 times). Over the entire season, the additional
labor requirements for annually cropped and perennially cropped
fields average 141 percent and 149 percent of existing irrigation
labor requirements, respectively. Converting to a high frequency
irrigation regime during the first month of the irrigation season
would increase labor requirements by almost an order of magnitude
and it is doubtful if this much time would be available. Conse-
quently, the high frequency case would require a restructured
irrigation system, similar to the cut-back method discussed in
the following paragraph.
Even though furrow irrigation application efficiencies can
be substantially improved by increasing the labor input to
existing irrigation practices, there is very little, if any, real
benefit to the irrigator if he does so. In fact, the overirriga-
tion now occurring creates very few detriments to the farm
production system in the Grand Valley. If minimal field tail-
water is to be achieved through increased field or farm effi-
ciency, additional labor to improve these efficiencies would be
even less feasible. Consequently, in the Grand Valley, it is
doubtful that anything short of legislative mandate would induce
the necessary labor inputs to control the salinity contributions
from on-farm sources; the reductions need to be achieved with
structural measures. One such measure is automated cut-back
irrigation as described by Evans (1977). With less labor than
that being invested currently, the irrigator can achieve the
85-90 percent application efficiency and at the same time almost
eliminate field tailwater. High frequency irrigations are
possible with small amounts of additional labor.
97
-------
SECTION 9
BORDER IRRIGATION
DESCRIPTION OF BORDER IRRIGATION
One of the oldest and most widely practiced method of
irrigation in the world is border irrigation. Border irrigation
uses earthen dikes or "borders" to contain the water within
specified boundaries. These borders can be constructed on a
sloping or graded surface or to form basins or level borders.
Borders may also be constructed following the contour in hilly
areas and may be either sloping or level (terraces).
On very steep areas where land leveling costs would be
prohibitive and the soils are usually not deep enough for
leveling, a variation of flood irrigation using dikes is used.
This method is often called guide border irrigation and is used
on pasture or hay crops. Generally speaking, these "borders" are
spaced fairly close together, the runs are short, and uniform-
ities and efficiencies are low. This method has little applica-
tion in the Grand Valley, but is used in high mountain meadows
and grasslands.
The border method is suitable for a wide range of soil
textures. However, extensive and exact land leveling and shaping
is usually required for efficient water use and uniform distribu-
tion. In addition, border dimensions can usually be designed for
efficient operation of planting, tillage, and harvesting
equipment.
Border irrigation efficiencies can be greatly increased by
automation and the method, in general, is especially amenable to
automation. Howe and Heerman (1970) presented a strong case for
the automation of border irrigation. In graded borders, the
uniformity and efficiency depend on the precise cut-off time of '
irrigation, which is often not practical from a labor viewpoint.
In level borders or basins, the exact amount of water applied is
critical since too much could cause overtopping of the dikes
and/or excessive deep percolation losses. Humphreys (1971),
Sweeten and Carton (1970), Erie and Dedrick (1976), Evans (1977),
and others have described several relatively inexpensive methods
by which these systems can be automated.
98
-------
The Water Resources Council (1971) estimated the attainable
field efficiency (without automation) in the Upper Colorado River
Basin to range from 60 to 75 percent for strip or graded borders
and 50 to 80 percent for level borders or basins.
Conversations with local irrigators and canal company
officials in the Grand Valley have shown that there is a definite
opposition to any type of border irrigation due to crusting (and
thereby germination) problems with this method. However, there
are other areas in the western United States and the world which
use this method on similar soils where crusting is controlled by
several different management techniques.
Graded Border Irrigation
Graded border irrigation requires that the field be divided
into strips varying from 10 to 20 meters or more in width and
extending 100 to 800 meters in length. The slope of these
"bordered strips" should not exceed 2 percent for row crops,
which would apply to most of the best lands in the Grand Valley.
Slopes can be as high as 6 percent for small grains and pastures
or hay.
Field efficiency of graded borders is usually about 65
percent, and the application efficiency ranges from 70 to 80
percent with proper management. Bos and Nugteren (1974) in a
worldwide survey of irrigation efficiencies reported that the
average application efficiency for graded borders was about 53
percent. The average for the United States was 57 percent. A
limitation of graded border irrigation is that it generally
requires considerable skill and a higher degree of management
than does furrow irrigation. However, labor requirements can be
lower than other methods.
Graded borders are suitable for all close growing crops
(except rice or other crops grown in ponded water) such as small
grains, alfalfa, and grass hay as well as orchards and vineyards.
It is best suited for soils with moderately low to moderately
high infiltration rates which compares with the range of the
Grand Valley soils. This method should not be used on coarse,
sandy soils with high intake rates or on soils with very low
intake rates (where basins should be used) since the opportunity
time for adequate infiltration would be quite long and both deep
percolation and runoff would be excessive.
Border strips must be leveled carefully and all cross slope
eliminated. At the present time, land leveling in the Grand
Valley would cost approximately $370/hectare ($150/acre) to
convert to graded border irrigation.
Ideally, the correct management of graded borders requires
that the proper amount of water be turned into the border, and
99
-------
the stream be turned off before the water reaches the end of the
border. The purpose is to apply a sheet of water evenly over the
border for uniform infiltration and minimal tailwater. As a
rule-of-thumb, the recession time is usually about 25 percent of
the required opportunity time.
Jensen and Howe (1965) studied low-gradient borders in the
sandy loam soils near Scottsbluff, Nebraska, and found that
application efficiencies (water stored in root zone divided by
delivered water) of 90 to 95 percent were easily obtained. For
maximum efficiency they found that the rate of water application
should be from three to five times the average intake rate. In
addition, if the net depth of application is greater than or
equal to 5 percent of the total fall in the border, an "end-
block" to impound the water is recommended to increase efficiency.
Level Border Irrigation
The level border or basin irrigation method consists of
turning relatively large streams of water into level plots
surrounded by dikes or levees to form basins. There is no
runoff. This method is especially adaptable to soils with
moderate to low permeability rates where other irrigation methods
do not provide an adequate infiltration opportunity time. At
this time, the USDA, Agricultural Research Service is evaluating
a modification of this type of irrigation in the Grand Valley.
They are using a concept of level borders with furrows in an
attempt to circumvent crusting and resulting germination problems
experienced in earlier graded border irrigation experiments in
the area.
To avoid excessive deep percolation, the design application
efficiency should not be less than 80 percent. With proper
management, efficiencies of 90 percent or more are not uncommon.
It is often very difficult to construct these level basins,
and it is also very difficult to maintain a perfectly level land
surface. The advent of laser controlled land planes and scrapers
has greatly helped this problem. However, to avoid low areas or
reverse grades, which would reduce the application efficiency,
the basins are often leveled with a slight grade in the direction
of irrigation. Land leveling and shaping costs for level borders
in the Grand Valley are presently estimated to be about $620/
hectare ($250/acre).
In the study cited earlier by Bos and Nugteren (1974),
application efficiency on a worldwide basis for level borders or
basins averaged about 58 percent. In the United States the
average value was 59 percent. These average figures are lowered
considerably by rice irrigation which is a continuous ponding
method, does not account for precipitation, and generally has
high deep percolation losses.
100
-------
HYDRAULICS OF BORDER IRRIGATION
The basic hydraulics of surface irrigation were described in
Section 8, where recession was assumed to be negligible for the
furrow irrigated soils and field slopes of the Grand Valley.
However, this assumption cannot be made for border irrigation
where recession is a very important component of the irrigation
process.
Evans et al. (1970), Kincaid et al. (1972), Kincaid (1970),
Lewis and Milne (1938), Hall (1956), Bassett (1973), Wu (1972),
Phillips and Farrell (1969), and others have presented several
methods for the calculation of border hydraulics. Recent work by
Katopodes and Strelkoff (1977), Strelkoff and Katopodes (1977),
and Strelkoff (1977) has developed a more complete model for
hydraulic flow which will closely predict recession. For the
field slopes found in the Grand_ Valley (about 70 percent of the
fields between 0.5 and 2 percent slopes), it is sufficient to use
the algebraic approaches proposed by Strelkoff (1977) . The more
rigorous zero inertia model would be more applicable if the
slopes were relatively small (roughly about 0.2 percent or
less) .
Strelkoff (1977) proposed the use of an algebraic model for
the calculation of border hydraulics based on the assumption that
the downstream depth is constant and normal for the unit runoff
at the end of the depletion phase, which is the start of the
recession phase.
The advance curve can be approximated by the volume balance
approach of Hart et al. (1968)
(72)
( '
r y + rT I
y -^o I o
where X is the advance distance,
q is the volume inflow per unit width of border
t is equal to time
r is a shape factor, approximately equal to 0.8
y is the normal depth for q
I is the depth of infiltration at the head of the border
0 given by the Kostiakov equation as defined in Section 8.
I = AtB (73)
and the subsurface shape factor r-j. is equal
r = ~L- (74)
I T+B
101
-------
Recession can be calculated by the following differential
equation:
5/3 .......
where i = length of the field which is inundated by the
receding water front
S = slope of the water surface
S = slope of the ground surface
T = average infiltration rate
GU = coefficient for units in the Manning equation
(in the cgs systems, C = 1)
n = coefficient of roughness for the Mannings equation.
The second term in the right-hand side of the equation represents
the runoff rate out the downstream end of the border where the
flow is assumed to be at normal depth. The above equation can be
simplified by the division of the formula by S £ and defining a
new constant: y
c s 1/2 s 5/2
C = U ° _ y - .............. (76)
nl
For most soils I will approach a constant value with large
infiltration times, which is usually the case for recession.
Using these assumptions, Equation 75 reduces to the form of:
_!z f
dt (77)
where L is the total length of the field, and t is the time at
which the recession phase commences.
The volume of runoff at time tr (for the depletion phase)
before starting the recession phase is given as:
Vro(tr) = VQ - Vy(tr) - VjU^J. (78)
where
(79)
102
-------
S L2
- Hi— ................. (80)
(81)
and tco is the time at which inflow into the border is stopped
and tL is the advance time for water to reach the end of the
border. The computation of runoff during the recession phase
is expressed as a differential equation:
inf ' ' (82)
where q^ f = volume infiltrated.
By use of the above equations it is a relatively simple
matter to compute the depth of infiltration at any point along
the field and the total runoff for any q . At that point, by
use of the techniques described in Section 8/ the application
efficiencies for border irrigation in the Grand Valley can be
easily computed.
EVALUATION OF BORDER IRRIGATION IN THE GRAND VALLEY
As mentioned previously, no attempt was made as part of
this project to physically evaluate graded border irrigations.
Therefore, this analysis will be based on data collected in the
Grand Valley by other investigators such as Gilley (1968), Howe
and Heerman (1970), Kincaid (1970), and Evans et al. (1970).
Graded Borders
Gilley (1968) and Howe and Heerman (1970) used a uniformity
coefficient for graded border irrigation as defined by
Christiansen (1942):
UCC = 100(1 - J) (83)
where y = average of the absolute deviations of the measurements
d = average measurement.
These uniformity coefficients were calculated for measurements
of intake opportunity time (UCCt) and soil moisture (UCCW).
The results indicated that approximately 30 percent of all
irrigations had a UCCW of at least 90 percent and 85 percent of
all irrigations had a UCCW of at least 80 percent. The seasonal
average UCCW for the Grand Valley soils (Billings silty clay
loam) was quite close to 90 percent.
103
-------
The stream size required to attain uniform intake
opportunity time for one site in Grand Valley decreased from 0.01
m^/sec to 0.006 m3/sec per meter of border width (0.11 cfs to
0.06 cfs per foot of border width) as the season progressed. The
intake opportunity time doubled from 60 minutes to 120 minutes
while the infiltrated depth decreased from 10 to 7.6 cm (4 to 3
inches), and the recession rates decreased from 3.05 to 1.52
meters per minute (10 to 5 feet per minute). These results are
quite consistent with results found elsewhere in the Valley for
furrow irrigation.
Howe and Heerman (1970) presented envelope curves (Figure
30) for infiltration depth versus time. Approximately 75 percent
of these data fit within these curves. The upper curve corre-
sponds to a 1.0 intake family as defined by the USDA-SCS, and the
lower curve is a 0.5 intake family.
There was no application efficiency information reported for
the studies, and personal communication with the investigators
has indicated that efficiency data from this work would not be
suitable for analysis. Therefore, utilizing the published data
collected in graded borders in the Grand Valley by Gilley (1968),
Howe and Heerman (1970), and Kincaid (1970), an analysis was
performed using the Strelkoff (1977) algebraic method.
For the purposes of illustration, the results of this
analysis for the "average" field in the Grand Valley (slope =
1.25 percent, length = 150 meters) are shown in Figure 31. The
analysis was done using selected application rates per unit width
and at cut-off times of 80, 100, 120, 150, and 200 percent of the
time for the advancing water front to reach the end of the field.
The time required for the flow to advance the full length of the
border is shown on each line of the graphs in Figure 31.
Extending this analysis indicated that row crops such as
corn would be expected to have a seasonal application efficiency
of about 80 percent. Utilizing a similar distribution of the
infiltrated depths as presented in Figure 20 of Section 5,
alfalfa would seasonally contribute about 5 metric tons of salt
per hectare and corn about 12 metric tons per hectare. The
differences in potential salt loading between graded borders and
existing furrow irrigation practices with good management appear
to be insignificant. The cost-effectiveness of graded borders
would be poorer than furrow irrigation due to the increased costs
of land leveling. For both furrows and graded borders, the
infiltration characteristics of the soils of the Grand Valley are
the controlling factors and not the method of application.
Therefore, it can be concluded that graded borders offer little
advantage over furrow irrigation, and this change is not
warranted.
104
-------
22
20
18
16
W
•- 14
0)
0)
E 12
S 10
1= 1.444 to.384.
100
200 300 400 500 600 700 800
Time in minutes
Figure 30. Characteristic intake curves for graded border irrigation
in the Grand Valley (Howe and Heerman, 1970).
-------
100
80
60
40
>s
O
20
iu o
.o 100
o
o
80
S 60
£
40
20
1= 1.5809 t°-2l4cm
q=0.00372 m3/s-m
q=0.00697 m3/s-m
q=O.OI022 m3/s-m
I i
1= 1.444 t°-384 cm
0 20 40 60 80 100 120 140
Cutoff Time in minutes
Figure 31,
Application efficiency as a function of the
calculated cut-off time (tco) for the "average"
field of 1.25 percent slope, 150 meter lengths
(50 percent soil moisture depletion, discharge
per unit width).
106
-------
Utilizing data from the SCS National Engineering Handbook on
border irrigation (1974), a net depth of application on a 1
percent slope with end blocks on graded borders would have a
maximum border length of 667 feet (203.3 meters). A 1.5 percent
slope would have a maximum length of 444 feet (135.3 meters). As
was shown in Section 5, the median field slope (Figure 19) in the
Valley is about 1.25 percent and the median field length (Figure
18) is about 160 meters (525 feet) with 75 percent of the fields
under 247 meters (810 feet) in length. From these figures it is
obvious that a large portion of the Valley could easily and
efficiently be converted to graded border irrigation if it was
proven advantageous to change.
Level Borders
As was mentioned previously/ there is no data on level
borders in the Grand Valley, but at the present time the
USDA-ARS is conducting experiments in the Grand Valley on level
borders with furrows. Use of the furrows is an attempt to
prevent crusting problems which were encountered in the earlier
investigation of graded borders. This is because the water would
not cover the top of the furrows where the crops would be
planted.
Assuming that these problems can be solved, the very high
application efficiencies possible with level borders provides a
very high potential as a salinity control measure. However, they
do require a much higher degree of management than presently
exists in the area. In addition, since there is no runoff, the
potential for conserving water is obvious.
Due to the high uniformity and control afforded by properly
designed and constructed level borders with good water management
practices, it can be concluded that with a seasonal application
efficiency of 90 percent (with a similar seasonal infiltration
distribution to the one used previously), the annual potential
salt load could be as low as 2.10 metric tons per hectare. With
an 80 percent seasonal application efficiency, the annual salt
contribution would be about 5.15 metric tons per hectare. Again,
due to soil infiltration characteristics, annual row crops such
as corn would be expected to have the higher contribution, while
established crops such as alfalfa and pasture would have the
lower value.
Land leveling costs for level border would be about
$620/hectare ($250/acre) and a lined delivery system and irriga-
tion scheduling would add approximately an additional $400/
hectare ($160/acre) for a total estimated cost of $l,020/hectare,
based on the median field size in the Grand Valley of 2 hectares
C5 acres).
107
-------
At an 80 percent seasonal application efficiency, the
cost-effectiveness of a level border system compared to a con-
servative value of 8 metric ton per hectare contribution under
existing practices (8.00-5.15 = 2.85 metric ton/hectare reduc-
tion) would be approximately $358 per metric ton of salt removed.
This would be without automation, but imposing a very good water
management program. At the 90 percent seasonal application
efficiency, the cost-effectiveness would be $173 per metric ton
of salt removed per hectare (8.0-2.1 = 5.9 ton reduction per
hectare). As can be seen from this analysis, the cost-
effectiveness is quite sensitive to the type of crops, or more
specifically to the soil infiltration characteristics due to
cropping practices and patterns. Automation would add little
cost to these systems, but would provide significant advantages
in maintaining a high degree of water management. Without
automation, the labor requirements would be considerable and
perhaps not acceptable to local growers.
As discussed earlier, 75 percent of the fields in the Grand
Valley are less then 247 meters (810 feet), and by using the
criteria presented by the SCS National Engineering Handbook on
level borders (Figure 32), it can be seen that a large portion of
the Valley could be converted to level borders. It is probable
that an application efficiency of 90 percent is the upper limit
of which would be expected for the Grand Valley. However, since
there are several problems with using this method of irrigation
in the area which needs to be addressed by further research,
level borders will not be considered as potential cost-effective
salinity control measures in this analysis.
108
-------
o
o
UJ
c
o
o
~o.
Q.
<
l_
O)
o
100
,P 90 -
Length in meters
0 50 100 150 200 250 300 350 400 450 500 550
F = Net Application, inches
Q = Discharge per Unit Width , cfs
n = Manning's Friction Factor
IF= SCS Intake Family
600 800 1000
Length in feet
200 1400
1600
1800
Figure 32.
Application efficiency as a function of length for level borders (USDA
SCS, Border Irrigation, 1974). (n = 0.15 for early season irrigations,
n = 0.04 for late season irrigations).
-------
SECTION 10
EVALUATION OF SPRINKLER IRRIGATION
Sprinkler irrigation is one alternative for the control of
irrigation water application which influences the quality of
irrigation return flows. Sprinkler and trickle irrigation
systems are a mechanical means by which the application of water
can be controlled much more precisely than by surface irrigation
methods. Furthermore, these mechanical systems can be automat-
ically or manually operated, and they can apply water continu-
ously or intermittantly in any required quantity. If properly
designed, sprinklers should have very little surface runoff and
can be very efficient.
Reduction in the amount of return flow will also reduce the
total salt loading of the return flows, and for sprinklers this
is usually accomplished by reducing the leaching fraction or, in
other words, reducing the amount of water applied in relation to
the evapotranspiration requirements of the crop. Bernstein and
Francois (1973) of the U.S. Salinity Laboratory have found that
leaching fractions can be reduced to as much as one-fourth of
presently recommended values with no reduction in yields for
alfalfa. Leaching fractions as low as 2 or 3 percent (due more
to soil characteristics than to the method of water application)
are common in the Imperial Valley of California, one of the most
productive areas in the world.
Sprinkler irrigation systems are recommended and used on
practically all types of soils with few limitations due to
topography and on almost all types of crops. This type of
irrigation, with its flexibility and efficient water control, has
permitted a wider range of soils to be irrigated than have
surface water application methods. It has thus allowed more land
to be classed as irrigable. As a direct result, many thousands
of hectares, which were previously considered suitable only for
dryland farming or as wasteland, are being irrigated today and
producing high yields. This phenomenon is particularly evident
in eastern Colorado, western Nebraska, and Kansas.
On some saline soils, as in the Imperial Valley of California,
sprinklers are recommended for better leaching and crop germina-
tion. Sprinklers are especially desirable where soils have a
high permeability and/or low water holding capacity. Sprinklers
110
-------
can offer distinct advantages over other irrigation methods in
dense soils with low permeabilities. In areas where labor costs
are high for surface irrigation, sprinklers are the most econom-
ical way to apply water. In other areas where water costs are
high, sprinklers have proven the most economical method since
surface runoff can be minimal. In many cases, sprinklers have
been shown to increase yields. In the fresh vegetable and fruit
market where color and quality are very important, sprinklers
have some advantages over surface irrigation methods.
Sprinklers can have multiple uses. The same equipment can
be used for irrigation, crop cooling, frost control, and the
application of pesticides, herbicides, and fertilizers. In
addition, modern farming practices which require large equipment
and large fields for economical farming operations are easily
irrigated by sprinklers with no reduction in efficiency.
Many areas in the United States, which annually receive more
than enough precipitation to satisfy crop requirements, are
installing supplemental irrigation systems. This is due to the
fact that rainfall often does not fall at exactly the right time
in the right quantities. A timely irrigation at a critical crop
growth stage, applying only a few inches of water, can often more
than double yields. Sprinklers are used in a large number of
these supplemental irrigation systems due to their adaptability
to large topographic differences and soil conditions.
Sprinklers, like most physical systems, do have
disadvantages. Damage to some crops has been observed when
poor quality irrigation water has been applied to the foliage by
sprinklers (Harding et al., 1958). Also, poor quality water can
leave undesirable deposits or coloring on the leaves or fruit of
the crop. Sprinklers are also capable of increasing the inci-
dence of certain crop diseases such as fire blight in pears,
fungi or foliar bacteria. A major disadvantage of sprinklers is
the relatively high cost, especially for solid-set systems, in
comparison to surface irrigation methods. When gravity cannot
supply sufficient head to operate the system, sprinklers can
require large amounts of energy when the water has to be pumped
to supply the necessary pressure. In many cases, it is often
more economical to use conventional surface irrigation systems.
The advantages and disadvantages of sprinkler systems must be
assessed economically with other irrigation methods. Likewise,
individual types of sprinkler systems should be compared to one
another.
EVALUATING SPRINKLER SYSTEMS
In evaluating any type of irrigation system, there are
several variables which all systems have in common and which
must be determined for a complete analysis. These include
111
-------
infiltration characteristics of the soil, uniformity of water
application, the application efficiency, crop water requirements
and the irrigation frequency.
An important advantage of sprinkler irrigation is that the
application rate can be designed so that the average infiltration
value of the soil is not exceeded, thereby eliminating tailwater
runoff. Fitting the system to the soil characteristics is
important since runoff is economically undesirable because of the
higher cost of water. As described in an earlier section of this
report (Section 7), the infiltration rate is a factor of slope
and vegetative cover as well as the soil's physical and chemical
characteristics. Therefore, each individual sprinkler system is
site-specific. Application rates are controlled by the sprinkler
head design, nozzle sizes, and the pressure at the nozzle. The
wide selection of available sprinkler heads and nozzle sizes
usually permits a designer to select the proper combination to
meet the specific soil and crop requirements. If the sprinkler
is to be used for purposes other than irrigation, such as frost
control, these uses also influence sprinkler selection. In
short, the application rate is a function of design, including
pump selection, sprinkler selection, and pipe sizes.
The uniformity of application of a sprinkler system is a
measure of proper design. Generally, the higher the uniformity,
the better the design. Experience in the field has indicated
that water distribution is usually satisfactory if the uniformity
coefficient is greater than 70 percent. For purposes such as
frost protection or cooling, it is desirable to maintain a
uniformity coefficient greater than 80 percent. The uniformity
coefficient is also often called the distribution efficiency.
An individual nonoverlapping sprinkler generally has a
nonuniform distribution pattern. However, with the proper
design, considering overlapping from other sprinklers, these
differences can be reduced.
Sprinkler distribution patterns have been described by
several statistical coefficients. The first was proposed by
Christiansen (1942) who proposed a uniformity coefficient (UCC)
for sprinkler systems:
n (y, - y)
UCC = 1.0 - I — (84)
i=l N y
where y. is the depth of the ith observation
y is the average depth applied
N is the number of equally spaced observations.
A perfectly uniform distribution is 1.0.
112
-------
There are several other suggested distribution coefficients
including Hart (1961) and Hart and Reynolds (1965) who proposed
that the precipitation from sprinklers was a normal (Gaussian)
distribution and the coefficient (UCH) could be described as:
UCH = 1 - ' s ............... (85)
Y
where s is the standard deviation of the depth measurements.
Hart (1961) and Seniwengse et al. (1972) established the rela-
tionship between UCC and UCH as:
UCC = 0.030 + 0.958 UCH, (r2 = 0.888) ..... (86)
Karmeli (1977) proposed that a simple and effective
statistical description of uniformity was a linear regression.
The linear function is described as:
Y = a + bX .................. (87)
where Y is a dimensionless precipitation depth of (y/y)
X is the fractional area
a,b are linear regression constants (a is Y . , b is the
i ^ j_i_ ? • \ mxn
slope of the line)
y is the depth of precipitation
y is the mean of the observed depths.
The uniformity coefficient (UCL) is then described as:
UCL = 1.0 - 0.25 b .............. (88)
This relationship can be seen in Figure 33a. Use of the UCL as a
statistical description offers many advantages over the UCC and
UCH. For example, the deficiently watered area, the average
watered area, the surplus watered area, and the respective
volumes of water in each of these areas are easily calculated.
Since the UCL is a description of system performance, Y can
also be defined as the depth of water applied (y') divided by the
average depth of the water over the field (y'). The amount of
water required is the soil moisture deficit and will equal a fraction
of Y=1.0 shown in Figure 33b. Therefore, Figure 33b can also be
interpreted as the fractional amount of water required versus the
fractional area. Or, in other words, the horizontal required
water application line can be shifted up or down to intercept
any point on the Y-axis. The maximum practical application from
the agronomic standpoint would be at Y=Ym£ where none of the
area would be underirrigated; however, much of the area will be
overirrigated. That point will be where 100 percent of the
irrigated area will receive at least that dimensionless depth of
water. Operation above this point would excessively waste water
113
-------
2.0
1.5
1.0
£ 0.5
a.
a>
Q
:= 0
V)
9
c
o
'55
c
2.0
1.0
0.5
•mm
man
0.5
1.0
'Deficiently
Watered
Area
:Volume of Deep
Percolation
^Dimensionless Depth
Required to Refill the
Root Zone , Dr
Deficiently
Watered
Volume
Figure 33.
0 0.5 1.0
Fractional Area.X
a) Graphical representation of the linear uniformity
coefficient; b) the uniformity coefficient as related
to system performance.
114
-------
and energy. Operation of the sprinkler system at the Y-intercept
of the requirement line (Y=D =1.0) would have 50 percent of the
area underirrigated and 50 percent overirrigated. Since the
average application would equal the average amount required (or
Y=1.0), this would be an advantageous level to operate the sys-
tem for a return flow quality program. Obviously, a 50 percent
areal deficit would be unacceptable to a grower and a level some-
where between the two levels could be established. This analysis
assumes there is no surface runoff.
Utilizing the concept shown in Figure 33b, it is quite
easy to compute the application efficiency if a specified amount
of the area is deficiently watered:
Application Efficiency = root zone storage ( }
vv •* gross application x '
D -(1-Y . )2 D -(1-Y . )2
r mm7 r mm
AE = ^ = 2£ (89a)
= D -(1-a)2 (89b)
r ~2b
2
The quantity Dr - (1-a) /2b is the dimensionless volume of
applied water actually stored in the root zone, and the dimen-
sionless volume actually applied is 1.0.
The volume of deep percolation can be obtained by
D = (1-AE)D= (90)
P a
where D is the depth of deep percolation in millimeters
D is the average depth of applied irrigation water
a in millimeters
AE is the application efficiency.
The salinity reduction achieved by a sprinkler conversion
depends on the corresponding decrease in the volume of deep
percolation attributed to converting previously surface irrigated
lands to sprinkler systems. Lands already sprinkler irrigated
would probably not convert to surface systems, although a con-
version to drip irrigation may be considered. In any event, this
analysis assumes that efficiencies among the various types of
sprinkler systems are approximately the same and conversion
between types is not included. The reduction in deep percolation
can be written from Equation 90:
115
-------
AD = (l-AAE)D ............... (91)
P a
in which AD is the reduction in deep percolation, mm; and
AAE is improvement in application efficiency expressed
as a fraction.
The deficiently watered area (A ) is given by:
D - Y .
r mm
AD = — b - ................ (92)
Figure 34 shows hypothetical curves of AD and application
efficiency for several values of UCL. In addition, this informa-
tion can be used to develop a linear irrigation scheduling
relationship between the depth of required water and the length
of irrigation (time) for a given application efficiency. This is
given by the relationship:
Length of = [Ymin+(1"Dr)] 0epth of re^ired water) (93)
Irrigation application rate
where Yntin+ (l-Dr) is used as the fractional amount of required
water (Dr£l) , and the application rate is the average of the
sprinkler system. The required water is defined as the amount
(depth) necessary to fill the root zone plus the necessary
leaching fraction. This relationship is shown in Figure 35 and
would be for a specific sprinkler system. As can be seen from
this graph, there is a "policy space" between the lines. The
upper line has a higher efficiency (and a greater areal deficit)
than the lower line which is the lowest practical efficiency at
which a system should operate (no areal deficiency) . A balance
must be attained between the agronomic requirements of 0 percent
of the area deficiently watered and the goals of an irrigation
return flow control program which desires to decrease deep perco-
lation and increase application efficienies to 50 percent or 100
percent areal deficit level. The relationships of application
efficiency and UCL for various areal deficit levels is illustrated
in Figure 36a.
Willardson et al. (1977) and others have stated that due to
variations in wind and other factors, variations which occur in a
single irrigation often tend to be compensated for by subsequent
irrigations. Therefore, it is possible, and often desirable, to
operate the sprinkler system in deficit ranges. The percent
value of this deficit is difficult to ascertain, but is probably
near 10 percent. In addition, there are managerial tools which
can greatly increase application efficiencies. For example,
Willardson et al. (1977) have shown that moving sprinkler heads
by one-half of the distance between adjacent sprinklers each
116
-------
100
) 10 20 30 40
Deficiently Watered Area,Percent
Figure 34. Deficiently watered area in percent.
50
60
117
-------
Figure 35,
Time
Hypothetical graph of the depth of required water
for constant application efficiencies as a function
of time for a given distribution coefficient.
118
-------
irrigation, can increase seasonal uniformity by 5 percent. The
percent increase in application efficiencies at various areal
deficit levels in response to 5 and 10 percent increases in the
UCL is shown in Figure 36b. The importance of this is illustrated
by the following example. If an increase of 2.5 percent in
application efficiency (5 percent increase in UCL) could be
obtained at the 50 percent deficiency level/ it would be equiva-
lent to an increase of up to 12.5 percent at the 0 percent
deficiency level (from Figure 36b). The 0 percent level is the
level at which most growers would prefer to operate. Management
practices which increase uniformity would have more of an impact
at the higher application levels, demonstrating that a workable
balance can be reached. Similar relationships can be determined
for any deficit level by the use of Figure 36a, plotted as in
Figure 36b.
The above example illustrates the fact that after the
irrigation system is designed with as high a uniformity as
possible, it is the management that ultimately determines the
final efficiency. The irrigator decides what deficiency level is
desired for agronomic purposes and then imposes additional
management tools on the system such as irrigation scheduling and
movement of sprinkler heads. However, it should be pointed out
that many managerial alternatives do require additional labor and
would not be implemented unless the marginal cost of water, or
the cost of pollution control reflected in the water cost, was
greater than the additional cost of labor.
Obviously, the higher application efficiencies are desirable
from the standpoint of irrigation return flow quality control.
The relationship of application efficiency to salt pickup per
irrigation, which could also be viewed as the deficit irrigation
level as a function of salt pickup, is shown in Figure 37. This
relationship does not appear to be sensitive to changes in
evapotranspiration rates, but is affected by the quality of
applied water. This curve was calculated from experimental data
on a per irrigation basis because efficiencies, especially in
surface irrigations, will change from one irrigation to the next
(as is illustrated in Section 5: Present Irrigation Practices).
Sprinkler application efficiencies, however, tend to be fairly
consistent over the irrigation season, varying less than 10
percent on the average as compared to a seasonal difference which
can be as much as 70 percent for surface irrigations in the Grand
Valley, depending on the crop.
An examination of Figures 36a and 37 reveals that sprinkler
systems with a UCL of 80 percent operating at the 50 percent
areal deficit range would have a 90 percent application effi-
ciency, and an average salt pickup contribution of 0.2 metric
tons per hectare per irrigation due to deep percolation (500
mg/& water). Over six irrigations, this would contribute only
119
-------
U
c
.2
o
o.
Q.
9
O
6O% Deficit Area
a)
0.5 0.6 0.7 0.8 0.9 1.0
UCL
Application efficiency as a function of the UCL.
Figure 36.
Application efficiency as a function of the UCL,
and the increases in application efficiency as a
result of 5 and 10 percent increases in the UCL
as related to the deficiently watered area.
120
-------
o
O
o
k.
<
c
o
<5
Q.
Percent Increase in Application Efficiency
b) Increase in application efficiency for 5 and 10
percent increase in the UCL as a function of the
deficiently watered area.
Figure 36. (Continued).
121
-------
o 16
o
V
(O
o
14-
E 12
o
10
o
.? 8
Q_
?
JC
O
Q.
O
to
3500 mg/£ leaving root zone
44% reduction in groundwater
flows due to phreatophytes
7800 mg/£ groundwater return
flows to river
500 mg/ g Applied Water
100 mg/g Applied Water
2000
_ Applied Water
Figure 37.
10 20 30 40 50 60 70 80
Application Efficiency in Percent
Relationship between salt pick-up and application
efficiency as a function of the quality of applied
water for the Grand Valley.
122
-------
1.2 metric tons per hectare. The same system operation at a 0
percent areal deficit level would have an application efficiency
of 50 percent and an average salt pickup contribution of about
4.5 metric tons per hectare per irrigation. This efficiency
over six irrigations would_contribute 27 metric tons per hectare.
The same system operating at the 10 percent areal deficit level
would have an application efficiency of 58 percent and a 2.7
metric ton per hectare per irrigation salt pickup for a total
of 16.2 metric tons per season. This compares with present
surface irrigation methods in the Grand Valley, which when com-
bined with the data presented in Figure 21 (Section 5), results
in salt pickup ranging from 20 to 30 metric tons per hectare per
year due to deep percolation and head ditch seepage. Head
ditches would be eliminated under sprinkler systems.
It should be obvious from the above discussion that
management plays a very significant role in the salt contribution
of any system, even potentially efficient systems such as
sprinklers. In other words, the installation of an efficient
system by itself will often not substantially reduce salinity
in return flows.
EVALUATION OF SPRINKLER IRRIGATION IN GRAND VALLEY
Under this project, two sprinkler systems were installed and
evaluated for salinity control effectiveness in the Grand Valley.
These systems were a 5.2 hectare (12.8 acre) permanent overhead
sprinkler system installed on a mature pear orchard and a 4" (10
cm) diameter side-roll wheel-move sprinkler on a 4.05 hectare (10
acre) established alfalfa field. In addition, the USDA Agricul-
tural Research Service has just completed a series of studies
using a center-pivot sprinkler system in the Grand Valley (Duke
et al., 1976). The center-pivot method was chosen by the ARS
primarily for the high degree of water application control which
was afforded and not so much for the evaluation of center pivots
in the Grand Valley.
Past experience with improperly designed sprinkler irrigation
systems in the valley has caused a negative reaction among local
growers. As a consequence, there are few agricultural sprinkler
systems in the area.
The only overhead sprinkling system installed on an orchard
in the Valley was constructed as part of this project. Approxi-
mately 10 percent of the irrigated area in the Valley is in
orchards, and when irrigating pome and deciduous fruits, over-
head sprinklers offer many advantages over conventional surface
irrigation in addition to the obvious salinity benefits. These
systems can be used for cooling, frost protection or bud
retardation, and fertilizer and pesticide applications.
123
-------
The grower who owns and operates this system has been quite
pleased with the results. In the spring of 1976, the harvest on
the part of his orchard not under this system was small due to
frost damage; the frost protection abilities of this system saved
the 5.2 hectares of pears and a full crop was harvested. In such
cases where the gross income from the crop is in excess of $2,500
per hectare ($1,000 per acre) per year, it is obvious that poten-
tial savings can be substantial, and the system could almost pay
for itself in one year.
This system was installed for a total cost of $3,432 per
hectare ($1,389 per acre) in the spring of 1975. During the two
years the system was evaluated, the annual operation and mainte-
nance costs were less than $185 per hectare ($75 per acre)
including frost protection, irrigation, and some cooling.
Taking into consideration the pressure differential from the
top and the lower end of the field, the average application rate
for the system was 3.23 mm/hr (0.127 inches per hour) when the
entire field was in operation at once as in frost protection.
When only half the field was being irrigated at one time, the
application rate was 4.17 mm/hr (0.16 inches per hour), and when
a fourth of the field was in operation, the application rate was
4.39 mm/hr (0.173 inches per hour). The UCL was 86.3 percent
(UCC = 89.0, UCH = 88.5). An examination of the catch-can data
plotted on Figure 38 reveals that the line does not pass exactly
through X = 0.5 at Y = 1.0 as it should theoretically. This is
due primarily to the effect of canopy interference on measure-
ments. This also partially accounts for the low r2 value of
0.874.
Figure 39 illustrates the application efficiencies which
could be expected at various levels of water management or levels
of deficit applications. Figure 40 presents irrigation sched-
uling curves for the three different application rates. This
system was designed with four values so that, if necessary, the
system could be operated in fourths or multiples thereof pro-
viding a large amount of flexibility in the operation and
management of the system.
An evaluation of Figure 37 and Figure 39 in combination
indicates the salt pickup of this system operating at the 0
percent deficiency level contributes about 2.5 metric tons per
hectare per irrigation. For seven irrigations, this would pro-
duce 17.5 metric tons per hectare per season. At the 10 percent
deficiency level, the system would contribute 14 metric tons per
hectare per season at the 20 percent deficiency level, it would
contribute about 7 metric tons per hectare, and at the 50
percent deficiency level about 1.4 metric tons per hectare per
season. Therefore, a workable balance between the goals of
salinity control and crop yield could probably be achieved at
the 10 to 15 percent areal deficit level.
124
-------
1.6
1.5
1.4
1.3
Q. | .2
o
M
jg I.I
c
o
g L0
I
i
0.9
0.8
0.7
0.6
0.5
Overhead Sprinkler
UCL * 86.3%
Application Efficiency=87%
AppMcation Efficiency =59%
"6^0684
0 O.I 02 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Fractional Area - X
Figure 38. Distribution characteristics of the 5.2 hectare
overhead sprinkler system.
125
-------
to
100
90
«
u
t_
4>
0,
.80
c
'o
«*-
«*-
llJ
c
(0
*•
o
o
"o.
o.
70
60
50
Overhead Sprinkler
b * 0.5504
86.3 %
10
20 30 40
Percent of Area in Deficit
50
60
70
Figure 39. Expected application efficiencies for operation of the overhead sprinkler
system at various areal deficit levels.
-------
(A
a>
f
u
.E3
I2
a.
a
O
0
Overhead Sprinkler
50% Deficiency
(87% Application
Efficiency)
0% Deficiency
( 59 % Application
Efficiency)
Ave. Application Rate 0.173 in/hr (4.39mm/hrr
( '/4 of System in Operation)
Ave. Application Rate 0.164 in/hr(4.l7mm/hr)
( */2 of System in Operation)
Ave. Application Rate 0.127 in/hr(3.23mm/hr)
(Entire System in Operation)
12
.
V
10 •£
5
8 .£
-0
a)
"a.
a.
a.
«
O
0
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32
Time of Irrigation in Hours
Figure 40. Irrigation scheduling curve, at the different-application rates, for the
overhead sprinkler system.
-------
As mentioned previously, the system cost was $3,432 per
hectare which discounted over ten years at 8 percent is $512.40
per hectare per year plus annual 0 & M costs of $185 per hectare
for a total annual cost of $697.40 per hectare.
Assuming a conservative annual salinity contribution value
of 20 metric tons per hectare under conventional irrigation
methods, operation of the sprinkler system at the 10 percent
areal deficiency level results in an annual decrease of 6 metric
tons per hectare per season due to deep percolation. Elimination
of head ditches would reduce the salinity by another 2.2 metric
tons per hectare for a total reduction of 8.2 metric tons per
hectare per year. The cost-effectiveness of this permanent
solid-set sprinkler system is $418.54 per metric ton (using only
the initial investment costs and not including annual 0 & M).
Even though this cost is quite high, this system does offer many
advantages other than salinity control to the grower which should
be considered such as frost protection and cooling. This analysis
does not account for annual depreciation, interest, taxes,
insurance, etc.
This system was higher in cost than most solid-set systems
due to its frost protection capabilities. A more reasonable cost
for a 4.05 hectare (10 acre) system would be $2,915 per hectare
($1,180 per acre) with a cost-effectiveness of $356 per metric
ton.
The second sprinkler system evaluated under this project was
a side-roll wheel-move system on 4.05 hectares (10 acres).
Figure 41 represents the uniformity and the application effi-
ciencies for different levels of management. The UCL is 86.7,
the UCC is 89.5, and the UCH is 88.8. Figure 42 presents the
curve of application efficiency versus the present deficiently
watered area. It should be pointed out that Figures 39 and 42
are almost equivalent due to the closeness of their uniformity
coefficients. Figure 43 depicts the irrigation scheduling curves
for the system. There are only two lines presented on this graph
because, unlike Figure 40, this system can only be operated one
set at a time.
The total cost of this system was $7,830.64 or $1,933.49 per
hectare ($783.06 per acre), or $288.15 per hectare when dis-
counted at 8 percent for ten years. The annual operation and
maintenance cost (O & M) has been $128.50 per hectare ($52 per
acre), resulting in total annual costs of $416.65 per hectare.
An analysis similar to that for the overhead solid-set
sprinklers reveals that the side-roll wheel-move sprinkler system
would likewise have the potential to reduce annual salinity by
8.2 metric tons per hectare. The cost-effectiveness of this
system is $236.00 per metric ton of salt removed, based only on
the capital cost of the system. However, the system was
installed on a small field and could be expanded at little
128
-------
£
c
o
1.6
1.5
1.4
1.3
I 0
1.2
i i
I.I
1.0
d>
5 0.9
^0.8
0.7
0.6
0.5
Side roll Sprinkler
UCL = 86.7 %
Application Ef f iciency=93
Application Efficiency = 66%
Dr = 0.731
0 O.I 0.2 0.3 0.4 0.5 0.6 07 0.8 0.9 1.0
Fractional Area-X
Figure 41. Distribution characteristics for the 4.05 hectare
side-roll wheel-move sprinkler system.
129
-------
u>
o
100
g 90
o.
o
c
«
•^ 80
UJ
c
o
o
'i. 70
Q.
60
Sideroll Sprinkler
b = 0.534
UCL = 86.7%
10
20 30 40
Percent of Area in Deficit
50
60
Figure 42. Expected application efficiency for operation of the side-roll wheel-move
sprinkler system at various areal deficit levels.
-------
w
0)
0)
^5
-o 2
.
a.
J=
*-
a.
I I ! I
Sideroll Sprinkler
i i i
12
10 w
8
4 .
o.
2 1
o
0 I 2 3 4 5 6 7 8 9 10 I! 12 13 14 15 16
Time of Irrigation in Hours
Figure 43. Irrigation scheduling curves for the side-roll wheel-move sprinkler system.
-------
additional cost to cover 16.2 hectares (40 acres). This would
result in a cost of about $750 per hectare ($303.50 per acre),
and a cost-effectiveness of $91.46 per metric ton of salt
removed.
Alternative Sprinkler Irrigation Systems
In addition to the permanent solid-set sprinklers and the
side-roll wheel-move sprinkler evaluated in the Grand Valley,
there are several other commercially available sprinkler systems
which could potentially be used in the area. These include hand-
move portable systems, portable solid-set systems, center pivots,
traveler,9and tow-line systems.
Hand-move portable systems were the first type of sprinkler
systems developed and still enjoy wide popularity. They are
usable in any situation where other types of sprinklers can be
used. As the name implies, the laterals of the system are moved
from set to set by hand labor. The mainline may be either buried
and permanent or may be portable. The approximate cost of a
complete hand-move system would be $650 per hectare ($260 per
acre) for a 16.2 hectare (40 acre) field, plus, of course, the
considerable labor requirements to operate the system.
Portable solid-set systems are basically a portable
hand-move system with enough laterals so that the laterals do not
have to be moved. In the Imperial Valley they are often used to
germinate vegetable crops and then the system is removed to
another field; and for the remainder of the season the field is
irrigated by surface methods. In other areas they are removed at
the end of the season for harvesting and tillage operations.
These systems are only slightly less expensive than permanent
solid-set systems due to smaller installation costs.
Many means have been devised to circumvent the labor
requirements of hand-move portable systems, one of which is the
center-pivot system. This sprinkler system rotates about a
central point (pivot) in a large circular or elliptical pattern
and most commonly covers 55 to 61 hectares (135 to 150 acres) per
system. The water is supplied through the pivot, and the
sprinklers are spaced along the pipe. The water application
rates on a center-pivot system vary from very low at the center
to very high at the end due to areal coverage differences. These
systems have several disadvantages. As one example, the corners
of a square field are not irrigated, unless by other systems
because of the circular pattern, and, consequently, the systems
are limited to areas where land values are fairly low. In
addition, the water distribution efficiencies (uniformities) are
often much lower than other sprinkler irrigation systems. On
some heavy soils where the application rate is higher than the
infiltration rate, erosion from runoff can be a problem. In
addition, on heavy soils, the machines often develop traction
132
-------
problems. Due to the heavy soils and small fields of the Grand
Valley, center pivots are not currently recommended. These
systems cost in the vicinity of $976 per hectare ($395 per acre)
for 55 hectares (135 acres) not including a well. The uniformity
andjapplication efficiencies analysis used in this section should
not be applied to center-pivot irrigation without modification of
the procedures.
Traveler or "big-gun" systems are usually limited to soils
with high infiltration rates since the sprinkler head is essen-
tially a large volume outlet "shooting" a large volume of water
up to 60 meters (200 feet) or more. The sprinklers can move down
a lane in the field on a trailer arrangement and pulling a long
flexible hose while irrigating, hence the name traveler. "Big-
gun" sprinklers can also be mounted on permanent towers, thus
becoming a high volume permanent solid-set system.
There are several variations on the traveler design
including a traveling boom type of system which uses several
smaller sprinklers mounted on a large boom to cover approximately
the same area. Traveler systems have many of the same disadvan-
tages of center-pivot systems, although instead of losing land at
the corners of a field, land is lost in the travel lanes every 46
to 122 meters (150 to 400 feet). For many of the same reasons,
traveler or "big-gun" systems are likewise not suitable for the
Grand Valley at this time. Approximate average total costs for a
traveler system are in the range of $660 per hectare ($240 per
acre) for a 16.2 hectare (40 acre) field.
Another type of sprinkler system quite similar to the
side-roll wheel-move concept is the end-tow or tow line. As the
name indicates, the system is mounted on skids or wheels, but is
towed from the end to the next net by a tractor or other vehicle.
These systems cost approximately $555 per hectare ($225 per acre)
for a 40 acre field. However, they are limited to fairly large
fields because they are towed forward to the next set and back to
the next in a zig-zag pattern. Consequently, these systems would
not be adaptable to the small field situations found in the Grand
Valley.
133
-------
SECTION 11
TRICKLE IRRIGATION
DESCRIPTION
A survey conducted in 1975 indicated that there were 54,115
trickle (or drip) irrigated hectares (133,717 acres) in the
United States (Shoji, 1977) . It was also estimated that there
would be more than 200,300 trickle irrigated hectares (495,000
acres) in the U.S. by 1980. A more recent survey conducted in
late 1976 found that California alone presently has 50,200
hectares (124,000 acres) of trickle irrigated crops (Irrigation
Journal, 1976).
Trickle irrigation is a system whereby water and possibly
fertilizer are applied directly to individual plants, as opposed
to irrigating the entire field area as with surface or sprinkler
irrigation. For orchard crops and other widely spaced crops,
this is accomplished with small diameter "laterals" running along
each crop row. "Emitters" attached to the lateral supply each
plant with its water needs. In the case of row crops or truck
crops, products are available with small diameter laser-drilled
orifices spaced at regular intervals along a thin-wall hose,
commonly referred to as "emitter-hose".
With trickle irrigation, water may be provided to the crop
on a low-tension, high-frequency basis, thereby creating a near
optimal soil moisture environment. Because of the high irriga-
tion frequencies, very high water use efficiencies are possible.
Water use efficiency as used in this report is defined as the
crop yield per unit of applied water. Research indicates that
water use efficiency can be increased by 50 percent or more using
trickle irrigation as compared with surface irrigation (Hiler and
Howell, 1972) .
Because only the plants' root zone is supplied with water,
under proper system management little water is lost to deep
percolation, consumption by nonbeneficial plants, or soil surface
evaporation. Wierenga (1977) reported that trickle irrigation
increased cotton yields by more than 8 percent while using 24
percent less applied water as compared to surface irrigation.
Trickle irrigation was also effective in controlling the return
134
-------
flow volume and in maintaining relatively low salinity levels in
the soil adjacent to the emitters.
In addition to reduced water requirements and minimization
of return flows, trickle irrigation has other positive advantages.
These include: (a) relatively saline water may be used under
proper management; (b) sloping or irregularly shaped land areas
may be more easily irrigated; (c) sandy soils may be more
efficiently irrigated; (d) increased production with most crops
is documented; (e) irrigation labor requirements are reduced;
(f) insect, weed, and disease problems are often reduced;
(g) soluble fertilizers and possibly pesticides and carbon
dioxide may be applied through the system; (h) harvesting and
tillage operations may occur simultaneously with irrigation;
(i) systems may be easily automated; and (j ) the practicality of
using low-yielding wells is increased. Also, there is potential
for using sewage or processing effluent water as a water source.
A wetted profile develops in the plants' root zone beneath
each emitter or emitter-hose orifice. The shape of the profile
is dependent on various soil characteristics and is limited by
horizontal flow constraints of the soil. An idealized version of
this profile for a tree crop is shown in Figure 44.
The surface area between widely spaced plants and between
plant rows is dry, receiving moisture only from rainfall.
Because of this, weed control problems may be substantially
reduced and it is possible to have virtually weed-free orchards.
A trickle irrigation system consists of a system "head" and
a distribution network. A pump, filter, flow meter, pressure
gauges, fertilizer injector, valve, pressure regulator, and
controller generally make up an automated system head as shown in
Figure 45. The flow meter and fertilizer injector are optional
equipment but highly desirable, and a controller is necessary
only if the system is to be automated. Anti-surge valves are
often necessary on larger systems.
The distribution network consists of piping, pipe fittings,
emitters, and circuit valves. Valves are actuated electrically
or hydraulically in the case of an automated system.
Drip systems are filtered either by a graduated sand filter
or a screen filter. Both require periodic backflushing which can
be automated. Either type filter may be preceded by a centrif-
ugal separator capable of removing most of the relatively high
density particles. Emitter manufacturers usually specify the
degree of filtration required for their emitter.
Any water soluble fertilizer or other water soluble chemical
may be injected into the trickle system. A pressure differential
can be used to cause flow through a tank as indicated in Figure
135
-------
ORCHARD
CROP
EMITTER
WETTED
PROFILE
ROOT ZONE
Figure 44
A wetted profile develops in the root zone below
each "emitter" or "trickier". This cross section
illustrates an idealized profile below emitters
placed on either side of a tree crop.
136
-------
v FERTILIZER
^- INJECTOR
oo
-j
PRESSURE
REGULATOR
SOLENOID
VALVE
CONTROLLER
Figure 45. Diagram of a typical automated, trickle system "head."
-------
45, or a nutrient metering pump can be used to carefully control
fertilizer applications. In either case, fertilizer is injected
in advance of the filter so that any undissolved solids are
removed and do not cause plugging.
Experience by California growers indicates that continuously
injecting chlorine at a concentration of about one part per
million is desirable for long-term system maintenance. On large
acreages this can be accomplished most economically with a gas
chlorinator. Also, additional chemical injection to control
biological slime buildup in the laterals may be necessary.
Trickle systems operate at relatively low pressure as
compared to sprinkler systems (5 to 20 psi or 35 to 140 kPa
pressure compared to 45 to 100 psi or 310 to 690 kPa). For this
reason, pumping requirements are substantially less than other
pressurized irrigation systems. A pressure regulator is used to
accurately control the lateral line operating pressure. Multiple
pressure regulators may be desirable for locations with large
elevation changes, and in some cases, low cost pressure regula-
tors have been used at the head of each lateral.
Small diameter, polyethylene or polybutylene pipe is
generally used for the system laterals which are laid on the soil
surface along each crop row or are buried to facilitate tillage
operations. Polyethylene pipe is available which is chemically
resistant to ultraviolet radiation. The ultraviolet radiation
causes some plastics to be subject to stress cracking, which has
been a problem with untreated pipe.
The lateral is connected to a manifold which is supplied
with water through a submain and/or main. A typical 6.1-hectare
(15-acre) orchard layout is shown in Figure 46. Laterals usually
run at right angles to the field slope. Manifolds, submains, and
mains are usually buried with short risers supplying laterals
laid on the surface.
A multitude of different types of emitters are available,
the purpose of each being to cause a pressure drop so that only
a small flow of water is discharged. This necessary head loss is
accomplished through the use of orifices, vortices, torturous
paths, impact plates, or a combincition of these. The flow through
a particular emitter is dependent on lateral pressure and may
vary from as low as one liter/ hour (0.26 gallons/hour) to as
much as 30 liters/hour (8 gallons/hour). Figure 47 presents
pressure versus flow curves for a few selected emitters and
emitter-hose products.
Basically, emitters may be classified into two categories.
The "standard" emitter or dripper emits water as a small stream
or drip which contacts the soil surface immediately below the
emitter. An aerosol emitter (also known as foggers, spitters,
138
-------
(~| System head
Set
Set 2
Set 3
1
1"
r
i
>
o
^— Lateral
*- Main
^ — Submain
~— Manifold
-• oir»'
^ oiu ••
"C
oc
1
Figure 46.
A typical 6.1-hectare (15-acre) orchard layout
showing the various system components.
139
-------
o
CO'
oe
•s.
-I
(9
-------
misters, and miniature spinklers) sprays water through the air
for some distance before it contacts the soil surface. Figure 48
illustrates idealized soil moisture cross sections under a
standard emitter and an operating aerosol emitter. Note that
saturated conditions are probable under the standard emitter.
This condition can inhibit root development due to limiting
aeration, but the obvious disadvantage of the aerosol emitter is
increased evaporation losses to the air during emitter operation
and from wet soil surfaces. Additional descriptive materials and
research findings for various crops, etc. may be located in Smith
and Walker (1975), an annotated bibliography on trickle
irrigation.
EMITTER HYDRAULICS
Over the desired range of discharges, the flow
charactersitics of any emitter may be characterized by the power
curve equation as presented by Keller and Karmeli (1975):
Q = a Hb (94)
where Q = emitter discharge, Iph
a = a constant of proportionality which characterizes
each emitter,
H = the working pressure head at the emitter, meters,
b = the emitter discharge exponent.
To determine coefficients a and b, the discharges at two or more
operating pressures must be known. The value of b characterizes
the flow regime and discharge versus pressure relationship of the
emitter. The lower the value of b, the less the discharge will
be affected by pressure variation due to pipe friction or eleva-
tion changes. In the fully turbulent flow regime, b = 0.5, and
in the laminar flow regime, b = 1.0. If an emitter could fully
compensate for changes in operating pressure (i.e., a pressure
compensating emitter), b would equal 0.0. Such an emitter does
not exist although some are reasonably effective as pressure
compensating emitters.
TRICKLE SYSTEM HYDRAULICS
A great deal of useful work has been done during the past
decade toward refining the design procedures for trickle irriga-
tion systems. The most noteworthy of the resulting publications
include Keller and Karmeli (1975), Wu and Gitlin (1974), Wu and
Fangmeier (1975), Howell and Hiler (1974), and Jobling (1974).
In addition, Wu and Gitlin have published various design aids
such as charts and slide rules through the Engineer's Notebook
series. Cooperative Extension Service, University of Hawaii,
Honolulu, Hawaii. Other references to design procedures, design
141
-------
Surface
-Wetted Radius
Standard Emitter (Dripper)
Aerosol Emitter
Spray Pattern
Deep Percolation
Figure 48.
Idealized soil moisture cross sections under a
standard emitter and an operating aerosol emitter,
Equal flow rates from each are assumed (Karmeli
and Smith, 1977).
142
-------
parameters, uniformity criteria, etc. may be found in Smith and
Walker (1975).
TRICKLE SYSTEM UNIFORMITY AND EFFICIENCY
An ideal trickle irrigation system would be one which
exhibits a uniform discharge from every emitter in the system,
resulting in uniform water application throughout the crop.
Unfortunately, such a system is nonexistent primarily because of:
(a) emitter characteristics including manufacturing variability;
and (b) differences in pressure distribution throughout the pipe
network due to frictional head losses (Karmeli et al., 1977). In
addition, elevation changes, emitter clogging, and water
temperature variation affect emitter discharge rates.
The variation in the value of the proportionality constant,
a, in Equation 94 tends to be normally distributed about a mean
value. Keller and Karmeli (1975) have developed a manufacturer's
coefficient of emitter variation, vm, which characterizes emitter
flow rates at a given pressure head as a normal distribution:
where v = manufacturer ' s coefficient of emitter variation
m
a = standard deviation of emitter discharges at a
reference head
y = mean discharge of emitters at a reference head.
Because of the normal distribution concept, 68 percent of an
emitter sample group will have a discharge within +_ one standard
deviation of the mean, about 95 percent will have a discharge
within + two standard deviations of the mean, and 98 percent will
have a discharge within + three standard deviations of the mean.
Soloman (1977) evaluated a number of emitters which
exhibited vm's ranging from a low of 0.02 to a high of 0.40. As
more emitters are performance evaluated over time, manufacturers
will tend to improve their products.
Several studies. have characterized the pressure distribution
along a lateral line (Wu and Gitlin, 1974; and Keller and
Karmeli, 1975) . A rule of thumb was subsequently adopted which
is to keep the discharge difference between simultaneously
operating emitters at a maximum of 10 percent. This allows for
a 10 to 20 percent variation in pressure head along a lateral,
depending on emitter characteristics. A detailed elaboration on
various trickle irrigation uniformity concepts may be found in
Karmeli et al. (1978) .
143
-------
Efficiency of applying water by trickle irrigation as
proposed by Keller and Karmeli (1975) is dependent upon:
(a) the transpiration ratio, TR, and (b) the emission uniformity/
EU. The transpiration ratio is defined as the ratio of water
transpired to water applied to the least watered areas. The
emission uniformity as defined by Keller and Karmeli (1975) takes
into account the uniformity of emitter discharge throughout a
particular system and a method of calculating EU from the
manufacturer's rating curve is also presented.
From Karmeli et al. (1978), characteristics of emitters
which affect efficiency are: (a) variations in discharge rate
due to manufacturing variations; (b) closeness of discharge-
pressure relations to design specifications; (c) the emitter
discharge exponent, b; (d) possible range of suitable operating
pressures; (e) pressure loss in lateral lines due to emitter
connections; (f) susceptibility to clogging; and (g) stability of
the pressure-discharge relationship over time.
Important design criteria which affect efficiency according
to Karmeli et al. (1978) are: (a) efficiency of filtration;
(b) permitted variations in pressure head allowed; (c) base
operating pressure used; (d) degree of flow (or pressure) control;
(e) relationship between discharge and pressure at the control
head; (f) allowance for temperature correction in long path
emitters; (g) chemical treatment to dissolve mineral deposits;
(h) use of secondary safety screening; (i) incorporation of flow
measurement; and (j) allowance for reserve system capacity or
pressure to compensate for reduced flow due to emitter clogging.
E , as:
cl
Keller and Karmeli (1975) defined application efficiency,
E_ = CTR) (EU) (96)
Good system management on the part of the irrigator is very
important in achieving high efficiencies as TR actually depends
upon good management. Some excess water is required for leaching
and providing a small safety margin. Keller and Karmeli (1975)
suggest TR = 0.90 as a reasonable design value for most situa-
tions. Although research supports TR's greater than 0.90, TR in
many cases has proved to be somewhat less for commercially
installed and operated enterprises. This is due to many factors
including: (a) contractor inexperience with trickle irrigation;
(b) cases where agriculturalists have underdesigned and built
their own systems; and (c) irrigator inexperience with trickle
system operation and maintenance. Over time, these problems
should decrease as more systems are built and operated and
additional experience gained.
144
-------
Values of TR and EU are also used in Keller and Karmeli's
(1975) design procedure for computing the gross depth of water
application, the irrigation interval, and the required system
capacity. EU's of 94 percent or above are desirable and design
EU's below 90 percent should not be considered.
TRICKLE IRRIGATION SYSTEM COSTS
Trickle irrigation system costs vary widely due primarily
to: (a) type of crop; (b) water source and quality; (c) degree of
automation; (d) type of emitter utilized; and (e) other regional
factors such as water costs, power costs, and labor (installation)
costs.
Individual emitters range in cost from $0.08 to $3.15 each.
However, the latter has six potential outlets. Polyethylene pipe
(1/2-inch) with ultraviolet radiation protection suitable for
surface applications ranges from $0.16 per meter ($0.05 per foot)
to $0.28 per meter ($0.086 per foot) depending on quantity.
Controllers suitable for the automation of trickle irrigation
systems range in cost from $300 to $1500 depending on quality and
sophistication. Filtration systems cost from $480 to $16,000
depending on the flow capacity and degree of automation (for
backflushing or blowdown).
The initial investment costs for a manually operated system
may be as little as $990/hectare ($400/acre). That initial
investment cost may increase to approximately $2500/ hectare
($1000/acre) or more for a highly automated system which schedule
irrigations as a result of soil moisture data from sensors
located in the field.
Assuming a 10 year system life, 8 percent interest, and
water costs of $65/hectare-meter ($8/acre-foot), Reed et al.
(1977) calculated the annual initial investment costs for a
40-hectare (100-acre) trickle system (in California) as $365/
hectare ($148/acre) after depreciation, interest, and taxes,
while the annual operating costs were calculated as $193/hectare
($78/acre). This indicates a total annual cost of $558/hectare
($226/acre) over the ten year life of the system. Due to the
large field size and conditions encountered in California, these
costs should be considered minimum values.
These costs, however, would be much too low for the Grand
Valley because the filtration requirements are very high (due to
the large amount of suspended sediment and organic matter in the
river water) and the small field sizes. A value of $1800/hectare
(Geohring, 1976) would be a better value for use in the Grand
Valley area. This is discussed in more detail in Section 12.
145
-------
EVALUATION OF TRICKLE IRRIGATION IN GRAND VALLEY
As part of this project there were two trickle irrigation
systems installed, both for the same grower. One was installed
on a peach orchard and the other on an apple orchard. The two
separate systems required two system "heads" and two distribution
networks; this, of course, considerably increased the per hectare
costs. The two systems were installed for $8514 on 2.2 hectares
for a $3870 per hectare cost. However, these systems have the
capacity to be expanded to cover an additional 5 to 6 hectares
with little additional cost resulting in approximately $1800 per
hectare cost. In fact, the drip system installed on the apple
orchard was designed with the intention of eventually covering an
additional 3 hectares. For purposes of this analysis a cost of
$2500 per hectare was used which approximates the cost of this
installation with only one system head.
As was reported in the preceding report, "Implementation of
Agricultural Salinity Control Technology in Grand Valley," (Evans
et al., 1978) these trickle irrigation systems were responsible
for reducing deep percolation by 0.4 ha-m or reducing salt
loading by 17.86 metric tons per year. This resulted in a cost
effectiveness of $308 per metric ton removed annually. However,
due to the economics of scale and using longer field sizes a cost
effectiveness value of $200 per metric ton is more applicable to
the Grand Valley for trickle irrigation.
146
-------
SECTION 12
COMPARISON OF IRRIGATION METHODS FOR SALINITY CONTROL
THE CONCEPT OF COST EFFECTIVENESS
The salinity in irrigation return flows associated with the
farm system itself is amenable to improvement by increasing
irrigation application efficiencies. In previous sections,
irrigation scheduling, rehabilitation and automation of surface
irrigation systems, and conversion to sprinkler or trickle
irrigation systems are described. In this section, the question
of the "best" program to reduce salinity is addressed.
The selection of the "best" or "optimal" on-farm
improvements to reduce the volume of return flows is based on a
minimum cost criterion in this work. In the Grand Valley, the
Federal Government is expected to provide cost-sharing arrange-
ments for the costs incurred in treating the irrigation system.
No funds are expected to be forthcoming to pay either operation
or maintenance costs associated with the use of the improved
systems.
The Federal Government and the Lower Basin water interests
affected by the Grand Valley salinity contribution would like to
maximize the effectiveness of the program, given the funds
appropriated for salinity control. This objective is equivalent
to minimizing costs associated with achieving a preselected level
of salt loading reductions. At the on-farm level, a number of
alternative improvements might be made to improve irrigation
efficiency and thereby reduce salinity. Each may be applied to
various fractions of the local acreage, resulting in a wide range
of expected salinity reductions. The relationship between cost
and salinity reduction for a single alternative and expressing
the potential range of the alternatives application is called a
cost-effectiveness function. For example, let the following
relationship represent the cost-effectiveness function for the
ith alternative for reducing on-farm salinity.
where Y. = cost of removing x-^ tons of salt through
1 implementing the ith on-farm irrigation
system improvement.
147
-------
The optimal on-farm program is evaluated for a predetermined
reduction in the on-farm salinity contributions (xf) by the
following analysis.
min
n
4=1
f . (x. )
(98)
subject to,
n
I *i
£=1
1 xf
(99)
and,
x. < X. ,
i = I/ 2,
n (100)
in which Yf = the minimum costs of reducing the total on-farm
contribution of salinity by x~ tons,
maximum reduction of salinity possible from the
ith alternative, and
number of alternative on-farm salinity control
options.
Xi
n =
The cost-effectiveness relationships are, therefore, the
mathematical tools needed to systematically compare the array of
alternative on-farm improvements which can be implemented to
control salinity. Its use must also incorporate the limits of
each alternative's effectiveness (constraints in the optimization
analysis, Equation 99. These relationships are the end product
of intensive salinity research and their definition represents
the transition between research and implementation.
In this study, the writers have selected a somewhat unusual
set of units to represent the parameters in the cost-effectiveness
functions. Salinity reductions are associated with the control
of salt pickup and expressed in metric tons prevented from
reaching the Colorado River per year. The costs are the 1976
present value estimates of the capital investments. Thus, the
costs are not distributed throughout the life of the improvement.
The resulting units of the cost-effectiveness function are
dollars per metric ton reduction over the life of the improve-
ments. These units are readily associated with the salinity
damages in the Lower Colorado River Basin. Since they only cover
the 30-50 year life of the improvements, a reevaluation of the
salinity control strategies in the Grand Valley at some time in
the future is implied.
The eventual program in the Grand Valley is dictated by its
respective feasibility in comparison to similar cost-effectiveness
148
-------
studies on the other subbasins in the Upper Colorado River Basin.
In fact, the level of investment in the entire river system for
salinity control depends on the level of damages created by the
salinity. Since a completed four level analysis is not available,
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/A 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 U.S. Bureau of Reclamation (Leathers and
Young, 1976). Some as yet unpublished figures now place these
damage figures as high as $375/ton.
SALINITY FROM ON-FARM SOURCES IN THE GRAND VALLEY
The segregation of the Grand Valley water and salt flow
system has been presented in several previous publications.
Since salinity is exclusively a subsurface return flow process in
the Valley, the major components of the on-farm contribution are
head ditch and tailwater ditch seepage and deep percolation. The
most recent estimates by the writers were presented by Walker
et al. (1977), and Walker (1978). The magnitude of the on-farm
salinity contribution in the Grand Valley may be summarized in
Table 7.
TABLE 7. MAGNITUDE OF THE ON-FARM SALINITY
CONTRIBUTION IN THE GRAND VALLEY
Water Losses Salt Pickup
head ditch seepage 100.1 95,500
deep percolation 200.1 190,900
tailwater ditch seepage neglected 0
expressed as millimeters, acreage is 25,000 hectares,
2 expressed as metric tons, each millimeter of subsurf<
flow represents 954 metric tons of salt pickup.
The Soil Conservation Service estimates that on-farm ditches
contribute 145,250 metric tons to the river system each year and
a contribution by deep percolation of 126,800 tons (Kruse, 1977).
The Agricultural Research Service estimates that ditch and deep
percolation salinity contributions are 103,500 tons and 129,800
149
-------
tons, respectively (USDA-ARS, 1977; and Kruse, 1977). Thus, the
on-farra totals by these three sources are within 20 percent of
each other, even though the segregations are somewhat different.
COST-EFFECTIVENESS RELATIONS
The on-farra alternatives for reducing salinity in the Grand
Valley can be discussed according to their earlier description:
(a) irrigation scheduling; (b) improvements in the existing
surface irrigation system; (c) conversion to sprinkle irrigation;
and (d) conversion to trickle irrigation. Each alternative is
intended to improve the irrigation application efficiency and
thereby reduce the volume of on-farm ditch seepage and deep
percolation.
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., 1974b). A
west-wide review of irrigation scheduling by Jensen (1975)
indicated that a 10 percent improvement (from 40 to 50 percent)
is realistically possible without system conversions or more
energy intensive operations. In the Grand Valley, a very simple
irrigation scheduling service which included water measurement
and farmer training would cost an estimated $30/ha and would very
optimistically reduce return flow salinity by about 20,000 metric
tons annually (Walker et al., 1978). Since it is not known how
irrigation efficiencies may be distributed, it is assumed that
these figures may be linearly extrapolated yielding a cost-
effectiveness function for irrigation scheduling of $37.50/ton
with a limit of 20,000 metric tons amenable to this approach.
The overall impact of irrigation scheduling being only 10
percent of the total estimated on-farm potential improvement is
insignificant by itself when considering the sensitivity of these
types of costing estimates. Consequently, irrigation scheduling
should be considered part of other measures rather than a
separate individual salinity control measure.
Improving theExisting Surface Irrigation System
Irrigation efficiency can often be substantially improved by
rebuilding and remodeling existing systems. The most commonly
employed irrigation method in the Valley is the furrow irrigation
method. Structural improvements in this system may include
concrete lined head ditches or gated pipe to reduce 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, changing to a border
150
-------
irrigation method, and automation to provide better control.
Flow measurement and scheduling services 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, 1:1 side slope, slip form
concrete). A cost figure for concrete lining of this size, well
within the range encountered in the last two seasons in the
Valley, is about $7.50/meter (1975 cost base). Six-inch diameter
aluminum gated pipe, which would carry about the same flows,
would cost approximately the same and can be arbitrarily sub-
stituted with equal cost-effectiveness. There are approximately
1.3 million meters of head ditches in the Grand Valley contrib-
uting an estimated 95,500 metric tons of salt to the river
annually. If linings were assumed to be 90 percent effective
(0.9 x 95,500 = 86,000), the cost-effectiveness of head ditch
improvements would be $113.40/ton (1.3 million meters x
$7.50/m v 86,000 tons).
Automatic cut-back furrow irrigation systems have
demonstrated improved application efficiencies of 75 or 80
percent (Evans, 1977), thereby affecting an additional 60,000 ton
decrease beyond the effects of the linings. In 1975, the
installed cost of the cut-back systems was $11.50/m. Thus, the
salt load reductions by lining head ditch (86,000 tons) and the
additional 60,000 metric ton salt reduction resulting from
increased application efficiency yields a cost-effectiveness of
$102.40/ton. Because of the small size of these ditches, a
linear distribution can be assumed without introducing signifi-
cant error. In the case of the Grand Valley, it appears automa-
tion may be added to surface irrigation systems for the purpose
of increasing application efficiency at about the same cost-
effectiveness as the simple head ditch or gated pipe improvements
($113.40/ton compared with $102.40/ton).
Field lengths can be modified and the fields leveled to
improve the uniformity of the water applications under surface
irrigation, particularly in soils having a relatively high
infiltration capacity. In the Grand Valley, however, the soils
have a low infiltration capacity, and the fields have a 1 to 2
percent slope so that the control of lateral flow distributions
are adequately made by the furrows. Uniformities are already
high and could be improved by varying the furrow flow rate such
as with a cut-back system. It is unlikely, therefore, that land
leveling or adjusting the field geometry should even be con-
sidered. Furthermore, local trials with border irrigation, where
land leveling and field length adjustments are necessary, did not
indicate higher application efficiencies than those already
achievable. Consequently, these on-farm improvements appear
infeasible at this time in the Grand Valley.
151
-------
System Conversion
In order to completely control irrigation return flows, the
method of applying irrigation water needs to be independent of
soil properties (i.e., sprinkler and trickle irrigation systems).
In earlier sections, the sprinkler irrigation application effi-
ciency was shown to be approximately 80 percent. Trickle systems
could be expected to operate at the 90 percent level. Applying
sprinkler systems to the average field size in the Grand Valley
(2-3 hectares) would be very expensive, so most systems would
only irrigate the larger or multiple fields . An estimate of the
area dependent costs of various sprinkler and trickle irrigation
systems is given in Figure 49, which indicates that portable
sprinkler irrigation systems (side -roll and hand-move) would cost
about $900 per hectare for a coverage of 10 hectares and $600 per
hectare if these areas were doubled. According to Walker et al.
(1977), 90 percent of the Grand Valley fields are less than 10
hectares so that the $900 per hectare side-roll sprinkler cost is
probably a conservative figure. Trickle irrigation systems would
cost approximately $1,800 per hectare for most local field sizes
(Geohring, 1976) . Assuming irrigators would consolidate fields
sufficiently to avoid the high costs for irrigating small fields,
and assuming application efficiencies of 80 percent and 90
percent for sprinkler and trickier systems, respectively, the
salt loading reduction for each system can be calculated as
follows (an existing application efficiency of 64 percent is
determined from the valley hydro-salinity data) :
SLR = SCDS + . (1 - [jzjJTjl) ........ (101)
where,
SLR = tons of salt load reduction per hectare;
SCDS = tons of salt reduction per hectare assuming the
pressurized systems eliminate head ditches;
TOFS = total on-farm salinity, 190,900 tons;
TA = total irrigated acreage, 25,000 ha; and
AE = application efficiency expressed as a fraction.
Thus, for sprinkler systems the per hectare salt decrease is 6.84
tons and for trickle irrigation systems, 8.96 tons. Mobile or
portable sprinkler systems would have average salinity cost-
effectiveness ratios of between $131.58/ton (assuming $900/ha
capital cost), while the costs for trickle. systems would be about
$200.89/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.
152
-------
OJ
2.0
1.8
1.6
1.4
0> I 9
0. '•£
O
§ 1.0
CO
O
O
0.8
- 0.6
O
GC
(A
O
O
0.4
0.2
D Solid Set Sprinkler
A Trickle
O Side-roll Sprinkler
• Handmove Sprinkler
y = U5+0.078/x
y = 0.95+9.4 xiO'Vx
y= 0.25 + 0.13/x
y= 0.14 + 0.13/x
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
Area Ratio, Area/25 ha
Figure 49. Cost relationships for pressurized irrigation systems (Walker, 1978) .
-------
OPTIMAL ON-FARM STRATEGIES
A summary of the individual cost-effectiveness functions for
the various alternative on-farm improvements are given in Table
8.
TABLE 8. COST-EFFECTIVENESS FUNCTIONS FOR ON-FARM
IMPROVEMENTS IN THE GRAND VALLEY
1)
2)
3)
4)
Alternative
head ditch lining
No. 1 -f automation
sprinkler irrigation
trickle irrigation
Function
Yhd =
Ycb =
Ys =
Yt =
113
102
131
200
.40
.40
.58
.89
Xhd
X
X
X
cb
s
t
X
X
X
X
Limitations
hd
cb
s
t
<_ 86,
<_ 146
1 171
<_ 224
000
,000
,000
,000
tons
tons
tons
tons
irrigation scheduling assumed to be part of each alternative.
2
subscripts are defined as: hd = head ditches; cb = automated
cut-back irrigation; s = sprinkler; and t = trickle.
The optimal on-farm program is developed by computing the
minimum cost strategy at various levels of on-farm salinity
reductions using the relationships summarized above. The results
shown in Figure 50 are those presented by Walker (1978) which
aggregate the head ditch linings into the automated case. The
actually computed cost-effectiveness relationship for on-farm
improvements is the step function shown as the solid lines. The
broken curve represents a best fit nonlinear distribution. The
assumption of linear or average cost-effectiveness functions was
made originally to alleviate the difficulty in defining the
variability experienced in the real system. The nonlinear curve
helps reestablish the curvilinear characteristic of such
relationships.
The best on-farm improvements in the Grand Valley shown in
Figure 50 might be discussed in terms of an implementation of
better on-farm irrigation practices in the Grand Valley. About
50 percent of the salt loading presently occurring from over-
irrigation can be reduced by lining and automating the farm head
ditches with concrete or gated pipe, and then carefully following
irrigation scheduling recommendations. The value of the automa-
tion is that the labor requirement in more careful irrigations is
eliminated, and by so doing, irrigation efficiencies can be
increased. This is the simplest and least costly alternative in
the Grand Valley. Sprinkler irrigation systems can be introduced
if it is decided that the on-farm salinity contribution must be
154
-------
50
en
t/j
O
O
Q.
O
O
40
30
20
10
Trickle
,' Irrigation '
a
• Irrigation •
'.Scheduling'-
Irrigation
Scheduling
^;x Head'.•>••• .;:;•
/.'-Ditch Linings v
a /:•;
rrigation Scheduling
Sprinkler
Irrigation
S
100
200
Figure 50.
Salinity Reduction, thousands of metric tons
Cost-effectiveness function for the first level,
on-farm improvement alternatives, in the Grand Valley
(Walker, 1978).
155
-------
reduced by about 60 percent (171,000 metric tons annually).
However, the existing field sizing is too small for economical
sprinkler systems and substantial consolidation would be
required. No costs have been assigned to the consolidation
requirement. Trickle irrigation can be introduced to expand on-
farm salinity control from 171,000 tons to about 224,000 tons
annually (60 to 78 percent). Again, farming and cropping
practices would require modification. It should be noted that
several forms of trickle irrigation are available to meet various
farmer desires.
156
-------
REFERENCES
Bassett/ D. L., 1973. A Dynamic Model of Overland Flow in Border
Irrigation. Unpublished Ph.D. Dissertation, University of
Idaho, Moscow, Idaho.
Beckwith, E. G., 1854. Report of Explorations for a Route
for the Pacific Railroad: U.S. Pacific R.R. Explor. V. 2.,
128 p.
Bernstein, L. and L. E. Francois, 1973. Leaching Requirement
Studies: Sensitivity of Alfalfa to Salinity of Irrigation
and Drainage Waters. Soil Sci. Soc. Amer. Proc. 37:931-942.
Blaney, H. T. and W. D. Griddle, 1950. Determining Water
Requirements in Irrigated Areas from Climatological and
Irrigation Data. U.S. Department of Agriculture, Soil
Conservation Service, SCS-TP96.
Bos, M. G. and J. Nugteren, 1974. On Irrigation Efficiencies.
International Institute for Land Reclamation and Improve-
ment. Pub. 19, P.O. Box 45, Wageningen, The Netherlands.
Christiansen, J. E., 1942. Irrigation by Sprinkling. California
Agri. Exper. Sta. Bull. No. 670, University of California,
Davis, California.
Christiansen, J. E., A. A. Bishop, R. W. Kiefer, and Y. Fok,
1966. Evaluation of Intake Rate Constants as Related to
Advance of Water in Surface Irrigation. Trans, of ASAE
9(l):671-674.
Dane, Jacob H., 1976. Soil Hydraulic Conductivity-Salt
Relationship. Unpub. Ph.D. Dissertation, Colorado State
University, Fort Collins, Colorado.
Doqrenbos, J. and W. O. Pruitt, 1977. Crop Water Requirements
(Revised Edition). FAO Irrigation and Drainage Paper 24,
Food and Agricultural Organization of the United Nations,
Rome, Italy.
157
-------
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. Agri. Res. Serv., U.S. Dept. Agri., Fort
Collins/ Colorado, October.
Elkin, A. D., 1976. Grand Valley Salinity Study: Investigations
of Sediment and Salt Yields in Diffuse Areas, Mesa County,
Colorado. Review draft sub. for State Conservation
Engineer, Soil Conservation Service, Denver, Colorado.
Erie, L. J. and A. R. Dedrick, 1976. Automation of an Open Ditch
Irrigation Conveyance System Utilizing Tile Outlets. Paper
No. 76-2050, Presented at 1976 Annual Meeting of ASAE,
Lincoln, Nebraska, June.
Evans, N. A., D. F. Heerman, 0. W. Howe, D. C. Kincaid, 1970.
Hydraulics of Low-Gradient Border Irrigation Systems.
Natural Resources Center Compl. Report Series No. 19,
Colorado State University, Fort Collins, Colorado.
Evans, R. G., 1977. Improved Semi-Automatic Gates for Cut-Back
Surface Irrigation Systems. Trans. ASAE 20(1):105-112,
January.
Evans, R. G., W. R. Walker, G. V. Skogerboe, and C. W. Binder,
1978. Implementation of Agricultural Salinity Control
Technology in Grand Valley. Environmental Protection Series
(in preparation), Robert S. Kerr Environmental Research
Lab., Office of Research and Development, U.S. Environmental
Protection Agency, Ada, Oklahoma.
Fok, Y. S. and A. A. Bishop, 1965. Analysis of Water Advance in
Surface Irrigation. J. Irr. and Dr. Div., ASCE, V. 91, No.
IRl, Proc. Paper 4251, pp. 99-116, March.
Geohring, L. D., 1976. Optimization of Trickle Irrigation System
Design. Unpublished M.S. Thesis, Dept. of Agricultural
Engineering, Colorado State University, Fort Collins,
Colorado, August.
Gerards, J. L. M. H., 1978. Predicting and Improving Furrow
Irrigation Efficiency. Unpublished Ph.D. Dissertation,
Agri. and Chem. Engr. Dept., Colorado State University,
Fort Collins, Colorado, December.
Gilley, James R., 1968. Intake Function and Border Irrigation.
Unpublished M.S. Thesis, Colorado State University,
Fort Collins, Colorado.
Hall, W. A., 1956. Estimating Irrigation Border Flow. Agri.
Engr., Vol. 37, April.
158
-------
Harding, R. B., M. P. Miller and M. Fireman, 1958. Absorption of
Salts by Citrus Leaves During Sprinkling with Water Suitable
for Surface Irrigation. Proc. Amer. Soc. Hort. Sci.,
71:218-256.
Hart, W. E., 1961. Overhead Irrigation Pattern Parameters.
Agri. Engr.f pp. 354-355, July.
Hart, W. E., D. L. Bassett and T. Strelkoff, 1968. Surface
Irrigation Hydraulics - Kinematics. J. Irr. and Dr. Div.,
ASCE, V. 94, No. IR4, December.
Hart, W. E. and W. N. Reynolds, 1965. Analytical Design of
Sprinkler Systems. Trans. ASAE, 8(l):83-85, 89, January-
February.
Hiler, E. A. and T. A. Howell, 1972. Crop Response to Trickle
Irrigation and Subsurface Irrigation. ASAE 1972 Winter
Meeting, Chicago, Illinois, December.
Howe, O. W. and D. F. Heerman, 1970. Efficient Border Irrigation
Design and Operation. Trans. ASAE, 13(1): 126-130.
Howell, T. A. and E. A. Hiler, 1974. Trickle Irrigation Lateral
Design. Trans. ASAE, 17(5):902-908.
Humphreys, A. S., 1971. Automatic Furrow Irrigation Systems.
Trans. ASAE, 14 (3):446, 470.
Irrigation Age, 1977. Does it pay to irrigate? Vol. 11, No. 9,
St. Paul, Minnesota, July-August.
Irrigation Journal, 1976. 1976 Irrigation Survey. 26(6):23-30,
November-December.
Israelsen, O. W. and V. E. Hansen, 1967. Irrigation Principles
and Practices. 3rd edition, John Wiley and Sons, New York.
Jensen, M. E. (ed.), 1973. Consumptive Use of Water and
Irrigation Water Requirements. ASCE, New York, New York.
Jensen, M. E., 1975. Scientific Irrigation Scheduling for
Salinity Control of Irrigation Return Flows. EPA-600/2-75-
964. Robert S. Kerr Environmental Research Lab., Office of
Research and Development, U.S. Environmental Protection
Agency, Ada, Oklahoma, November.
Jensen, M. E. and H. R. Haise, 1963. Estimating
Evapotranspiration from Solar Radiation. J. Irr. and Drain.
Div., ASCE, 89:15-41.
159
-------
Jensen, M. E. and O. W. Howe, 1965. Performance and Design of
Border Checks on a Sandy Soil. Trans. ASAE, 8 (1):141-145.
Jobling, G. A., 1974. Trickle Irrigation Design Manual - Parts 1
and 2. New Zealand Agricultural Engineering Institute,
Lincoln College, Canterbury, New Zealand, September.
Kang, S. T., 1972. Irrigation in Ancient Mesopotamia. Water
Resources Bulletin, Vol. 8, No. 3, pp. 619-624, June.
Karmeli, D., 1977. Water Distribution Patterns for Sprinkler and
Surface Irrigation Systems. In: Proceedings of National
Conference on Irrigation Return Flow Quality Management,
J. P. Law and G. V. Skogerboe, ed,, Dept. Agri. and Chem.
Engr., Colorado State University, Fort Collins, Colorado,
May.
Karmeli, D., L. J. Salazar and W. R. Walker, 1978. Assessing the
Spatial Variability of Irrigation Water Applications. (In
press) Environmental Protection Agency, Ada, Oklahoma.
Karmeli, D. and S. W. Smith, 1977. Aerosol Emitters for Trickle
Irrigation. Proceedings of International Agricultural
Plastics Congress, San Diego, California, April.
Katopodes, N. D. and T. Strelkoff, 1977. Hydrodynamics of Border
Irrigation. J. Irr. and Drain. Div., ASCE, Vol. 103, No.
IR3, September.
Keller, J. and D. Karmeli, 1975. Trickle Irrigation. Rain Bird
Sprinkler Manufacturing Corp., Glendora, California.
Kincaid, D. C., 1970. Hydrodynamics of Border Irrigation.
Unpublished Ph.D. Dissertation, Colorado State University,
Fort Collins, Colorado.
Kincaid, D. C. and D. F. Heerman, 1974. Scheduling Irrigations
Using a Programmable Calculator. U.S. Department of
Agriculture, Agricultural Research Service, ARS-NC-12,
February.
Kincaid, D. C., D. F. Heerman and E. G. Kruse, 1972.
Hydrodynamics of Border Irrigation Advance. Trans. ASAE,
15(4):674-680.
Kostiakov, A. N., 1932. On the Dynamics of the Coefficient of
Water Percolation in Soils and on the Necessity for Studying
it from a Dynamic Point of View for Purposes of Ameliora-
tion. Trans. 6th Com. Int. Soc. Soil Sci., Part A. Russian,
pp. 17-21.
160
-------
Kovdaf V. A., C. Van Den Berg and R. M. Hagen, editors, 1973.
Irritation, Drainage and Salinity. An International Source
Book, FAO/UNESCO, Geneva.
Kruse, E. G., 1977. Minutes of the Grand Valley Salinity
Coordinating Committee, Grand Junction, Colorado, February.
Leathers, K. L., 1975. The Economics of Managing Saline
Irrigation Return Flows in the Upper Colorado River Basin:
A Case Study of Grand Valley, Colorado. Ph.D. Dissertation,
Department of Economics, Colorado State University,
Fort Collins, Colorado.
Leathers, K. L. and R. A. Young, 1976. Evaluating Economic
Impacts of Programs for Control of Saline Irrigation Return
Flows: A Case Study of the Grand Valley, Colorado. Report
Project 68-01-2660, Region VIII, Environmental Protection
Agency, Denver, Colorado, June.
Lewis, M .R. and W. E. Milne, 1938. Analysis of Border
Irrigation. Agri. Engr., 19 (6):267-272.
Penman, H. L., 1948. Natural Evaporation from Open Water, Bare
Soil, and Grass. Proc. Royal Society of London, A198:116-
140.
President's Science Advisory Committee, 1967. The World Food
Problem. A Report to the President of the USA. Chapter 7,
Water and Land, pp. 405-469.
Phillip, J. R. and D. A. Farrell, 1964. General Solution of the
Infiltration Advance Problem in Irrigated Hydraulics. J.
Geophys. Res., 69:621-631, February.
Reed, A. D., J. L. Meyer, F. K. Aljibury and A. W. Marsh, 1977.
Irrigation Costs. Water and Irrigation, i(l):12-13, 24-25,
November.
Seniwengse, D., I. P. Wu and W. N. Reynolds, 1972. Skewness and
Kurtosis Influence on Uniformity Coefficients and Sprinkler
Irrigation Design. Trans. ASAE, 15(2):266-271, March-April.
Shoji, K., 1977. Drip Irrigation, Sci. Amer., 237 (5):62-68,
November.
Skogerboe, G. V., J. W. H. Barrett, B. J. Treat, D. M. McWhorter,
1978a. Irrigation Practices, Return Flow Salinity, and Crop
Yields. (In preparation) Office of Research and Development,
U.S. Environmental Protection Agency, Ada, Oklahoma.
161
-------
Skogerboe, G. V., D. M. McWhorter and J. E. Ayars, 1978b.
Irrigation Practices and Return Flow Salinity. (In prepara-
tion) Office of Research and Development, U.S. Environmental
Protection Agency, Ada, Oklahoma.
Skogerboe, G. V. and W. R. Walker, 1972. Evaluation of Canal
Lining for Salinity Control in Grand Valley. Report EPA-R2-
72-047, Office of Research and Development, Environmental
Protection Agency, Washington, D.C., October.
Skogerboe, G. V., W. R. Walker, R. S. Bennett, J. E. Ayars and
J. H. Taylor, 1974a. Evaluation of Drainage for Salinity
Control in Grand Valley. Report EPA-660/2-74-052, Office of
Research and Development, Environmental Protection Agency,
Washington, D.C., August.
Skogerboe, G. V., W. R. Walker, J. H. Taylor and R. S. Bennett,
1974b. Evaluation of Irrigation Scheduling for Salinity
Control in Grand Valley. Report EPA-660/2-74-084, Office of
Research and Development, Environmental Protection Agency,
Washington, D.C., June.
Smith, S. W. and W. R. Walker, 1975. Annotated Bibliography on
Trickle Irrigation. Environmental Resources Center Informa-
tion Series Report 16, Colorado State University,
Fort Collins, Colorado, June.
Smith, S. W. and W. R. Walker, 1976. Food Potential from Home
Gardens. Paper presented at Winter Meeting of ASAE,
Chicago, December.
Solomon, K., 1977. Manufacturing Variation of Emitters in
Trickle Irrigation Systems. Amer. Soc. Agri. Engr. Paper
No. 77-7009, June.
Strelkoff, T. and N. 0. Katopodes, 1977. Border-Irrigation
Hydraulics with Zero Inertia. J. Irr. and Drain. Div.,
ASCE, Vol. 103, No. IR3, September.
Strelkoff, T., 1977. Algebraic Computation of Flow in Border
Irrigation. J. Irr. and Drain. Div., ASCE, Vol. 103, No.
IR3, September.
Sweeten, J. M. and J. E. Carton, 1970. The Hydraulics of an
Automated Furrow Irrigation System with Rectangular Side
Weir Outlets. Trans. ASCE, 13(6):746-751, June.
U.S. Department of Agriculture, Agricultural Research Service,
1977. Alleviation of Salt Load in Irrigation Water Return
Flow of the Upper Colorado River Basin. Fort Collins,
Colorado, September.
162
-------
U.S. Department of Agriculture, Soil Conservation Service, 1974.
National Engineering Handbook, Section 15: Irrigation,
Chapter 4: Border Irrigation. Washington, D.C.
U.S. Department of Agriculture, Soil Conservation Service, 1974.
National Engineering Handbook, Section 15: Irrigation,
Chapter 11: Sprinkler Irrigation. Washington, D.C.
U.S. Department of Agriculture, Soil Conservation Service,
1976. Inventory of Conservation Plan Needs for the Grand
Valley. Open File Data, Grand Junction, Colorado.
U.S. Department of Agriculture, Soil Conservation Service,
and Colorado Agricultural Experiment Station, 1955. Soil
Survey, Grand Junction Area, Colorado. Series 1940, No. 19,
November, 118 p.
U.S. Department of Commerce, Environmental Science Services
Administration, Environmental Data Service, 1968. Local
Climatological Data, Grand Junction, Colorado.
U.S. Department of Commerce, Environmental Science Services
Administration, Environmental Data Service, 1972. 1969
Census of Agriculture, Volume 1—Area Reports, Part 41—
Colorado, May.
U.S. Department of Interior, Bureau of Reclamation, 1975.
Initial Cost Estimates for Grand Valley Canal and Lateral
Linings. Personal Communication with USER Personnel in
Grand Junction, Colorado.
U.S. Environmental Protection Agency, 1971. The Mineral Quality
Problem in the Colorado River Basin. Summary Report and
Appendices A, B, C, and D. Region 8, Denver, Colorado.
Valentine, V. E., 1974. Impacts of Colorado River Salinity. J.
Irr. and Dr. Div., ASCE, V. 100, No. IR4, pp. 495-510,
December.
Walker, W. R., 1970. Hydro-salinity Model of the Grand Valley.
M.S. Thesis CET-71WRW8. Civil Engineering Department,
College of Engineering, Colorado State University, Fort
Collins, Colorado, August.
Walker, W. R., 1975. A Systematic Procedure for Taxing
Agricultural Pollution Sources. Grant* NK-42122, Civil and
Environmental Technical Program, National Science Foundation,
Washington, D. C., October.
163
-------
Walker, W. R., 1978. Integrating Desalination and Agricultural
Salinity Control Alternatives. Environmental Protection
Technical Series (in press), Office of Research and Develop-
ment, Robert S. Kerr Environmental Research Lab., U.S.
Environmental Protection Agency, Ada, Oklahoma.
Walker, W. R. and G. V. Skogerboe, 1971. Agricultural Land Use
in the Grand Valley. Agri. Engr. Dept., Colorado State
University, Fort Collins, Colorado.
Walker, W. R., G. V. Skogerboe and R. G. Evans, 1977. Development
of Best Management Practices for Salinity Control in Grand
Valley. In: Proc. National Conference on Irrigation Return
Flow Quality Management, J. P. Law and G. V. Skogerboe,
editors, Dept. Agri. and Chem. Engr., Colorado State
University, Fort Collins, Colorado, May.
Walker, W. R., G. V. Skogerboe, and R. G. Evans, 1978. Best
Management Practices for Salinity Control in Grand Valley.
Environmental Protection Technical Series (in preparation),
Robert S. Kerr Environmental Research Lab., Office of Res.
and Devel., U.S. Environmental Protection Agency, Ada,
Oklahoma.
Water Resources Council, Upper Colorado Region State-Federal
Inter-Agency Group, 1971. Upper Colorado Region Compre-
hensive Framework Study Appendix X, Irrigation and Drainage,
Water Resources Council, Pacific Southwest Inter-Agency
Comm. Hu., June.
Wierenga, D. J., 1977. Influence of Trickle and Surface
Irrigation on Return Flow Quality. Environmental Protection
Agency, Report EPA-600/2-77-093. Office of Research and
Development, Ada, Oklahoma.
Wilke, 0. and E. T. Smerdon, 1965. A Solution of the Irrigation
Advance Problem. J. Irr. and Drain. Div., ASCE, Vol. 91,
No. IRS, September.
Willardson, L. S., R. J. Hanks and R. D. Bliesner, 1977. Field
Evaluation of Sprinkler Irrigation for Management of Irriga-
tion Return Flow. In; Proc. National Conference on Irriga-
tion Return Flow Quality Management, Fort Collins, Colorado,
May 16-19.
Wu, I. and D. D. Fangmeier, 1975. Hydraulic Design of Twin-
Chamber Trickle Irrigation Laterals. Agri. Exper. Sta.
Tech. Bull. 216, University of Arizona, Tucson, Arizona.
Wu, I. and H. M. Gitlin, 1974. Design of Drip Irrigation Lines.
Hawaii Agri. Exper. Sta. Tech. Bull. 96, University of
Hawaii, Honolulu, Hawaii, June.
164
-------
Young, R. A,, G. E. Radosevich, S. L. Gray, and K. L. Leathers,
1975. Economic and Institutional Analysis of Colorado Water
Quality Management. Completion Report Series No. 61.
Environmental Resources Center, Colorado State University,
Fort Collins, Colorado, March.
165
-------
BIBLIOGRAPHY
Bernstein, L. and L. E. Francois, 1975. Effects of Frequency of
Sprinkling with Saline Waters Compared with Daily Drip
Irrigation. Agron. J., 67:185-190, March-April.
Bernstein, L. and L. E. Francois, 1976. Comparison of Drip,
Furrow, and Sprinkler Irrigation. Soil Sci., 115:76-86.
Colorado Agricultural Experiment Station, 1955. Irrigation
Water Application and Drainage of Irrigated Land in the
Upper Colorado River Basin, Progress Report 1954, Project
W-28, Department of Civil Engineering, Colorado A & M
College, Fort Collins, Colorado, March, 38 p.
Colorado Agricultural Experiment Station, 1955. Irrigation Water
Application and Drainage of Irrigated Lands in the Upper
Colorado River Basin. Contributing Project Progress Report,
Western Regional Research Project W-28, November, 37 p.
Colorado River Board of California, 1970. Need for Controlling
Salinity of the Colorado River. The Resources Agency, State
of California, August, 89 p.
Colorado Water Conservation Board and U.S. Department of
Agriculture, 1965. Water and Related Land Resources
Colorado River Basin in Colorado, Denver, Colorado, May,
183 p.
Decker, R. S., 1951. Progress Report on Dranage Project (1945 to
Jan., 1951). Grand Junction, Colorado, Lower Grand Valley
Soil Conservation District, Mesa County, Colorado, January,
37 p.
Duke, H. R., E. G. Kruse, S. R. Olsen, D. F. Champion, 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,
Colorado. Review Draft Submitted for the State Conservation
Engineer, Soil Conservation Service, U.S. Department of
Agriculture, Denver, Colorado.
166
-------
Evans, R. G., S. W. Smith, W. R. Walker and G. V. Skogerboe,
1976. Irrigation Field Days Report 1976. Agri. Engr. Dept.,
Colorado State University, Fort Collins, Colorado,
August.
Fischbach, P. E. and B. R. Somerhalder, 1971. Efficiencies of an
Automated Surface Irrigation System with and without a
Runoff Re-Use System. Trans. ASCE, 14(4):717, April.
Fok, Y. S., A. A. Bishop and C. C. Shih, 1971. The Effect of
Intake Equations on the Development of the Water Advance
Equations for Surface Irrigation. Trans. ASAE, 14(5):
801-805.
Fremont, J. C., 1845. Report of the Exploring Expedition to the
Rocky Mountains in the Year 1842 and to Oregon and North
California in the Years 1843-44: Washington, Gales and
Seaton, U.S. Senate, 693 p.
Goldberg, D., D. Gornat and D. Rimon, 1976. Drip Irrigation.
Drip Irrigation Sci. Publ., Kfar Shmaryahu, Israel.
Grand Junction Chamber of Commerce, 1975. Grand Junction,
Colorado—An Economic Overview, 1975-76.
Hagan, Robert M., Howard R. Haise and Talcott Wa. Edminster,
editors, 1967. Irrigation of Agricultural Lands. No. 11 in
the series, Agronomy, American Society of Agronomy, Madison,
Wisconsin, 1180 p.
Hafen, L. R., 1927. Coming of the White Men; Exploration and
Acquisition, in History of Colorado: Denver Linderman Co.,
Inc., State Hist. Nat. History Soc. Colorado, Volume 1, 428
P-
Hall, W. A., 1956. Estimating Irrigation Border Flow. Agri.
Engr., Vol. 37, April.
Hall, W. A. and J. A. Dracup, 1970. Water Resources Systems
Engineering. McGraw-Hill, Inc., New York, New York.
Hayden, V. F., 1877. Report of Progress for the Year 1875: U.S.
Geol. and Geog. Survey Terr., Embracing Colorado and Parts
of Adjacent Territories, 827 p.
Hughes, W. R., 1971. Irrigation Costs, Center Pivot vs. Portable
Sprinkler Irrigation System, Texas High Plains. Texas Agri.
Exper. Sta. Inform. Report 71-1. Texas A & M University.
167
-------
Hyatt, M. Leon, 1970. Analog Computer Model of the Hydrologic
and Salinity Flow of Systems within the Upper Colorado River
Basin. Ph.D. Dissertation, Dept. of Civil Engineering,
College of Engineering, Utah State University, Logan, Utah,
July.
Hyatt, M. L., J. P. Riley, M. L. McKee and E. K. Israelsen, 1970.
Computer Simulation of the Hydrologic Salinity Flow System
within the Upper Colorado River Basin. Utah Water Research
Laboratory, Report PRWG54-1, Utah State University, Logan,
Utah, July.
lorns, W. V., C. H. Hembree and G. L. Oakland, 1965. Water
Resources of the Upper Colorado River Basin. Geological
Survey Professional Paper 441. U.S. Government Printing
Office, Washington, D.C.
Jensen, M .E., 1967. Evaluating Irrigation Efficiency. J. Irr.
and Drain. Div., ASCE, IRl, March.
Kneese, A. V., 1964. The Economics of Regional Water Quality
Management. The John Hopkins Press, Baltimore, Maryland.
Kuhn, H. W. and A. W. Tucker, 1951. Nonlinear Programming. In;
Proc. 2nd Berkeley Symp. Mathe., Stat., and Prob. J. Neyman,
editor. University of California Press, Berkeley, California,
Lacewell, R. D. and W. F. Hughes, 1971. A Comparison of Capital
Requirements and Labor Use, Alternative Sprinkler Irrigation
Systems, Texas High Plains. Texas Agri. Exper. Sta. Inform.
Report 71-3, Texas A & M University.
Law, J. P., Jr., J. M. Davidson and W. Reed, 1970. Degradation
of Water Quality in Irrigation Return Flows. Oklahoma State
University, Agri. Exper. Sta. Bull. B-684, October.
Lohman, S. M., 1965. Geology and Artesian Water Supply, Grand
Junction Area, Colorado. Geological Survey Professional
Paper 451, U.S. Government Printing Office, Washington,
D.C., 149 p.
Marr, James C., 1964. The Border Method of Irrigation,
California Agri. Exper. Sta. Circ. 408, University of
California, Davis, California.
Merriam, John L., 1968. Irrigation System Evaluation and
Improvement. Agri. Exper. Dept., California State Poly.
College, San Luis Obispo, California.
Miller, D. G., 1916. The Seepage and Alkali Problems in the
Grand Valley, Colorado. Office of Public Roads and Rural
Engineering, Drainage Investigations, March, 43 p.
168
-------
Pair, Claude A., editor, 1975. Sprinkler Irrigation, Sprinkler
Irrigation Association, Silver Springs, Maryland, 4th
edition.
Prehn, W. L., J. L. McGaugh, C. Wong, J. J. Strobel and
E. F. Miller, 1970. Desalting Cost Calculating Procedures.
Res. and Devel. Prog. Report 555, Office of Saline Water,
U.S. Dept. of the Interior, Washington, D.C., May.
Probstein, R. F., 1973. Desalination. Amer. Sci., 61(3):
280-293, May-June.
Reed, A. D., J. L. Meyer and F. K. Aljibury, 1976. Irrigation
Costs. Leaflet 2875, Coop. Extension Service, University of
California, February.
Schneider, E. J., 1975. Surficial Geology of the Grand Junction-
Fruita Area, Mesa County, Colorado. Unpublished M.S.
Thesis, Colorado State University, Fort Collins, Colorado,
October.
Somehalder, B. R., 1958. Comparing Efficiencies in Irrigation
Water Application. Agri. Engr., 39 (3):156-159.
Sternberg, G. V. The Grand Valley Canal and Water Rights. Date
Unknown, Grand Valley Irrigation Company, Grand Junction,
Colorado.
Thomann, R. V., 1972. Systems Analysis and Water Quality
Management. Env. Sci. Serv. Div., Environmental Research
and Application, Inc., New York, New York.
U.S. Department of Agriculture, Soil Conservation Service and
U.S. Department of the Interior, Bureau of Reclamation,
1959. Irrigation on Western Farms. Agri. Inform. Bull.
199, U.S. Government Printing Office, Washington, D.C.
U.S. Department of Agriculture, U.S. Salinity Laboratory, 1954.
Diagnosis and Improvement of Saline and Alkali Soils.
Agricultural Handbook No. 60, February.
U.S. Department of Agriculture and Colorado Agricultural
Experiment Station, 1957. Annual Research Report, Soil,
Water, and Crop Management Studies in the Upper Colorado
River Basin. Colorado State University, Fort Collins,
Colorado, March, 80 p.
U.S. Department of the Interior, Bureau of Reclamation, 1968.
Use of Water on Federal Irrigation Projects, Final Report
1965-1968. Volume 1, Summary and Efficiencies, Grand Valley
Project, Colorado, Region 4, Salt Lake City, Utah.
169
-------
U.S. Department of the Interior, Bureau of Reclamation, Region 4,
1969. Use of Water on Federal Irrigation Projects, Final
Report 1965-1968, Crop and Irrigation Data, Grand Valley
Project, Volume II.
U.S. Department of the Interior, Bureau of Reclamation, 1963.
Linings for Irrigation Canals. Denver Federal Center,
Denver, Colorado.
U.S. Department of the Interior, Bureau of Reclamation and Office
of Saline Water, 1972. Desalting Handbook for Planners.
Denver, Colorado, May.
U.S. Department of the Interior, Bureau of Reclamation and Office
of Saline Water, 1973. Colorado River International
Salinity Control Project, Executive Summary, September.
U.S. Geological Survey, 1976. Salt-Load Computations—Colorado
River: Cameo, Colorado to Cisco, Utah. Parts 1 and 2.
Open File Report, Denver, Colorado.
Walker, W. R., 1977. Combining Agricultural Improvements and
Desalination of Return Flows to Optimize Local Salinity
Control Policies. Paper presented at the National Con-
ference on Irrigation Return Flow Quality Management, Fort
Collins, Colorado, May 16-19, 203-213 pp.
Walker, W. R. and G. V. Skogerboe, 1973. Mathematical Modeling
of Water Management Strategies in Urbanizing River Basins.
Compl. Report Series 45, Environmental Resources Center,
Colorado State University, Fort Collins, Colorado, June.
Walker, W. R., T. L. Huntzinger and G. V. Skogerboe, 1973.
Coordination of Agricultural and Urban Water Quality
Management in the Utah Lake Drainage Area. Tech. Completion
Report to Office of Water Resources Research, U.S. Depart-
ment of the Interior, Report AER72-73 WRW-THL-GVS27,
Environmental Resources Center, Colorado State University,
Fort Collins, Colorado, June.
Walker, W. R., S. W. Smith and L. D. Geohring, 1976.
Evapotranspiration Potential Under Trickle Irrigation.
Amer. Soc. Agri. Engrs. Paper No. 76-2009, December.
Water Resources Council, 1972. OBERS Projections, Regional
Economic Activity in the U.S.; Volume 4, Washington, D.C.
Westesen, G. L., 1975. Salinity Control for Western Colorado.
Unpublished Ph.D. Dissertation. Colorado State University,
Fort Collins, Colorado, February.
170
-------
Wilde, D. J. and C. S. Beightler, 1967. Foundations of
Optimization. Prentice-Hall, Inc., Englewood Cliffs,
New Jersey.
Willardson, L. S. and A. A. Bishop, 1967. Analysis of Surface
Irrigation Application Efficiency. J. Irr. and Drain. Div.,
ASCE, IR2, June.
Worstell, R. V., 1975. An Experimental Burried Multiset
Irrigation System. Paper No. 75-2540, presented at
Winter Meeting, ASAE, Chicago, Illinois, December.
171
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/2-78-161
2.
3. RECIPIENT'S ACCESSION>NO.
4. TITLE AND SUBTITLE
EVALUATION OF IRRIGATION METHODS FOR
SALINITY CONTROL IN GRAND VALLEY
5. REPORT DATE
July 1978 issuing date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Robert G. Evans, Wynn R. Walker, Gaylord V.
kogerboe and Stephen W. Smith
8. PERFORMING ORGANIZATION REPORT NO,
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Agricultural and Chemical Engineering Departmen
Colorado State University
Tort Collins, Colorado 80523
10. PROGRAM ELEMENT NO.
: 1BB770
11. CONTRACT/GRANT NO.
Grant No. S-802985
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
tobert S. Kerr Environmental Research Laborator
)ffice of Research and Development
J. S. Environmental Protection Agency
Oklahoma 74820
14. SPONSORING AGENCY CODE
EPA/600/15
15. SUPPLEMENTARY NOTES
184 pages, 50 fig., 8 tab., 91 ref.
16. ABSTRACT
Irrigation return flows in the Upper Colorado River Basin carry
large salt loads as a result of contact with the saline soils and the
marine derived geologic substratum. The Grand Valley of western
Colorado is a major contributor to the salinity problems of the basin
and is, therefore, a logical region to test the effectiveness of agri-
cultural salinity control alternatives. This study emphasized the
implementation of on-farm salinity control alternatives; primarily
evaluating irrigation scheduling, furrow irrigation, sprinkler irriga-
tion, and trickle irrigation. Border irrigation was also evaluated,
but was not implemented as part of this study. The cost-effectiveness
of the various on-farm alternatives in the Grand Valley is summarized
and presented in this report.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Irrigation
Salinity
Saline soils
Water quality
Water pollution
Water loss
Colorado River
Grand Valley
Salinity control
Irrigation (methods,
(management, systems)
Return flows
98C
3. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
188
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
172
U. S. GOVERNMENT PRINTING OFFICE: 1978-757-140/1410 Region No. SHI
------- |