EPA 660/2 74 084
August 1974
Environmental
Evaluation of Drainage for Salinity
Control in Grand Valley
Office of Research and De^elop/nam
U.S. Environmental Protection Again
Washington, D C. 20450
-------
RESEARCH .REPORTING SERIES
Research reports of the Office of Research and
Monitoring, Environmental Protection Agency, have
been grouped into five series. These five broad
categories were established to facilitate further
development and application of environmental
technology. Elimination of traditional grouping
was consciously planned to foster technology
transfer and a maximum interface in related
fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL
PROTECTION TECHNOLOGY . series. This series
describes research performed to develop and
demonstrate instrumentation, equipment and
methodology to repair or prevent environmental
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.
EPA REVIEW NOTICE
This report has "been reviewed "by the Office of Research and
Development, EPA, and approved for publication. Approval does
not signify that the contents necessarily reflect the views
and policies of the Environmental Protection Agency, nor does
mention of trade names or commercial products constitute
endorsement or recommendation for use.
-------
EPA-660/2-74-084
August 1974
EVALUATION OF DRAINAGE
FOR SALINITY CONTROL
IN GRAND VALLEY
by
Gaylord V. Skogerboe
Wynn R. Walker
Ray S. Bennett
James E. Ayars
James H. Taylor
Grant No. S-800278
Program Element 1BB039
Roap/Task 21 AYR 015
Project Officer
Dr. James P. Law, Jr.
Robert S. Kerr Environmental Research Laboratory
P.O. Box 1198
Ada, Oklahoma 74820
Prepared for
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. Environmental Protection Agency
Washington, D. C. 20460
For sale by the Superintendent oC Documents, U.S. Government Printing Office, Washington, D.C. 20102 - Price $1.75
-------
ABSTRACT
Irrigation return flows in the Grand Valley of Western
Colorado contribute to the serious salinity problems in
the Colorado River Basin by carrying large salt loads
resulting from contact with local saline soils and aquifers,
Since the valley is one of the more significant salt
sources, it is therefore a logical area for evaluation of
the effectiveness of various salinity control measures.
This study has emphasized two on-farm control alternatives,
namely, irrigation scheduling and field drainage. The
contents of this report consider the latter measure.
Three farms were extensively studied during the 1972
and 1973 irrigation seasons to identify drainage needs and
the effect field relief drainage would have on reducing
salinity in the return flows. During the spring of 1973,
a perforated plastic pipe drainage system was installed on
one of the farms. Each farm was then incorporated into an
irrigation scheduling program. The results indicate that
while field drainage is effective in skimming water off
the top of the water table where salinity concentrations
are typically 20%-30% less saline, the high costs emphasize
the need to reduce seepage losses by lining canals and mini-
mize deep percolation losses through improved on-farm water
management in order to minimize the requirements for drain-
age facilities.
English units are used throughout this report. For English
to Metric conversion, refer to the table of equivalents
in the SECTION XI.
This report was submitted in fulfillment of Grant No.
S-800278 by Colorado State University under the sponsorship
of the U.S. Environmental Protection Agency. Work was
completed as of March 31, 1974.
-------
CONTENTS
Page
Abstract ii
List of Figures iv
List of Tables vi
Acknowledgements viii
Sections
I Conclusions 1
II Recommendations 3
III Introduction 4
IV Previous Drainage Investigations 14
V Drainage Design Methods 28
VI Field Investigations 40
VII Design, Construction and Evaluation of
Farm Drainage 63
VIII Drainage Evaluation for Grand Valley 83
IX Bibliography 95
X List of Publications 98
XI List of Symbols and Equivalents 99
111
-------
FIGURES
Figure Page
1 The Colorado River Basin 5
2 The Grand Valley of Colorado 6
3 Normal precipitation and temperature
at Grand Junction/ Colorado 8
4 Agricultural land use in the Grand Valley 9
5 Location of study farms in demonstration
area ^2
6 Boundaries of Grand Junction Drainage
District 20
7 Drillers log and well construction 25
8 Model for Hooghoudt's steady state
drainage equation 30
9 Model of the transient drainage
equation 32
10 Model for transient drainage equation
on impermeable barrier 36
11 Topographic map of the Canaday field 41
12 Topographic map of the Kelleher field 42
13 Topographic map of the Wareham field 43
14 Relationship of the average soil electrical
conductivity to depth in the soil profile
on the study fields for 1972 48
15 Geometry of Ernst's single-auger-hole
method used in homogeneous soil ,_i
16 Example plot of the recovery data for a
single-auger-hole hydraulic conductivity
test 53
17 Relation between leaching requirement and
drain spacing for the Canaday field 66
IV
-------
FIGURES (Cont.)
Figure Page
18 Relation between leaching requirement
and drain spacing for the Kelleher field 67
19 Relation between leaching requirement
and drain spacing for the Wareham field 68
20 Wareham farm drainage system layout 71
21 View of pipe installation 73
22 Graphical water budget for the Wareham
farm during its first irrigation after
drain installation 76
23 Average daily discharge from the Wareham
farm drainage system during the first
irrigation after installation 77
24 Graphical water budget for the Wareham
farm during its second irrigation after
drain installation 78
25 Graphical salt budget for the Wareham
farm during its first irrigation after
drain installation 80
26 Graphical salt budget for the Wareham
farm during its second irrigation after
drain installation 81
-------
TABLES
Pac
Description of farms in the demonstration
area included in the drainage and irriga-
tion scheduling studies 13
2 Summary of water quality samples taken
from test wells during 1949 24
3 Electrical conductivity values for
soils on the Canaday field 45
4 Electrical conductivity values for
soils on the Kelleher field 46
5 Electrical conductivity values for
soils on the Wareham field 47
6 Analysis of the textural classification
and moisture holding capacity of the
soils on the study fields 50
7 Hydraulic conductivity data for some
fields in the Grand Valley Salinity
Control Demonstration Project 55
8 Example calculation of irrigation
schedule for corn using the Jensen-
Haise method 60
9 Example of proposed yearly recharge
schedule used for drain spacing based on
an irrigation schedule for corn 61
10 Textural analysis of the soil profiles
of the auger holes used for hydraulic
conductivity tests on the study field 65
11 Results of irrigation efficiency tests
during the 1972 irrigation season on
the Wareham field 69
12 Agricultural land use in the Grand Valley 85
13 Grand Valley water budget for 1968
water year 87
14 Grand Valley distribution of canal flows
in 1968 88
VI
-------
TABLES (Cont.)
Table Page
15 Salt budget for Grand Valley during 1968 89
VI1
-------
ACKNOWLEDGEMENTS
The authors are indebted to the individuals who carefully
attended to the daily details of the field and laboratory
analyses. These people included Ms. Barbara Mancuso,
Mr. George Bargsten, Mr. Ted Hall, Mr. Chuck Binder, Mr.
John Bargsten, and Mr. Gregory Sharpe.
The cooperation of Mr. Bob Wareham, Mr. Jack Kelleher, and
Mr. Frank Canaday who allowed this investigation to proceed
on their lands is also greatly appreciated.
The actual computer irrigation scheduling service was
provided by the Grand Junction Office of the U.S. Bureau of
Reclamation. The cooperative attitude of Mr. Bill McCleneghan
certainly contributed to the success of these studies. In
addition, the aid offered by Mr. Newton E. Noyes, Soil
Scientist, USER, for field data collection during initial
work is also apprediated.
The construction of the drainage system could not have been
completed if not for the willingness of the Grand Junction
Drainage District to excavate the trenches. Thanks are
made to Mr. Howard K. Heist, Mr. Capper Alexander, and Mr.
J. Wesley Land, Board of Directors, and Mr. Charles Tilton,
Superintendent.
The writers would also like to thank Ms. Lee Kettering for
typing the final 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 demonstration grant.
Gaylord V. Skogerboe
Wynn R. Walker
Ray S. Bennett
James E. Ayars
James H. Taylor
Vlll
-------
SECTION I
CONCLUSIONS
Drainage investigation in the Grand Valley began shortly after
the turn of this century when local orchards began failing due
to saline high water tables. Study showed the soils to be
not only saline but also having low permeabilities. At the
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
these drainage needs/ the solutions were clearly set forth but
never fully implemented because of the large capital invest-
ment required. However, the citizens of Grand Valley did
elect to form a drainage district supported by a mill tax
levy in order to construct open ditch drains and some buried
tile drains to correct trouble spots.
The construction of open drains has played an important role
in Grand Valley. These drains serve as outlets for tile
drainage systems, as well as intercepting and conveying tail-
water runoff which would otherwise flow over surface lands,
infiltrate, and contribute to additional subsurface ground-
water 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 a different purposethat being the
skimming of water from the top of the water table before it
reaches equilibrium with the highly saline soils and aqui-
fers below, as well as demonstrating to local farmers the
benefits in increased crop production by improved drainage.
Three farms were selected for 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. In particular, in-
creasing irrigation efficiency during the early season would
sufficiently reduce deep percolation losses, which in turn
would keep the groundwater level at a satisfactory depth
below the ground surface to allow good crop production.
The results from the two farms illustrate the adage"an
ounce of prevention is worth a pound of cure". Thus, the
first steps in a salinity control program are to minimize:
(a) seepage losses from canals and laterals; and (b)
deep percolation losses from croplands (ideally, the deep
percolation losses would not exceed the leaching requirement).
By minimizing the amount of moisture reaching the ground-
water, the requirements for field drainage will also be
minimized.
-------
The third farm had been originally selected for investigation
as an example of the worst conditions encountered in Grand
Valley. An 11.6-acre (4.7 hectares) field on this farm
was selected for construction of a field drainage relief
system. Besides having a very high groundwater level,
the soils have low permeability, high salt content, and the
topography is irregular. In order to correct these defi-
ciencies, the following measures were taken: (a) a drain-
age system consisting of 4-inch diameter (10.2 centimeters)
perforated corrugated plastic pipe was installed on 40-foot
(12.2 meters) centers at an average depth of 6 feet (1.8
meters); (b) the field was leveled to allow better surface
irrigation; (c) the field was plowed to a depth of 2 feet
(60.1 centimeters) to increase surface permeability; and
(d) the field was planted in salt tolerant Jose Tall
Wheatgrass with a cover crop of oats.
Studies of the three farms, plus two additional farms
investigated for irrigation scheduling, show that field
drainage effluents had a salinity averaging 3000 mg/1 less
than the present subsurface irrigation return flows
reaching the Colorado River.
A principal advantage of field drainage (e.g., tile of
perforated pipe) is that the effluent is a point source
which can then be placed into a collection system for
disposal (e.g., evaporation ponds, deep well injection,
or desalination). Drainage in conjunction with salt
disposal would be required to achieve a zero discharge
policy for irrigation return flows.
As part of this study, an alternative use of drainage
was considered. During the 1950's, pump drainage from
the deep cobble aquifer was tested and proved most effective
for reclaiming croplands. By itself, pump drainage
offers no salinity control benefits because the salinity
of the pump drainage effluent is comparable to the salinity
of subsurface irrigation return flows reaching the
Colorado River. Pump drainage in combination with desal-
ination would be effective in reducing salt loads returned
to the river. In determining the costs of pump drainage
in combination with desalting, it becomes apparent that this
alternative is quite costly. However, with the recent
advances in desalination technology, this alternative
method of decreasing salt loads of river systems is certain
to become increasingly feasible as time progresses. This
control measure would likely be considered as the final
step in an overall salinity control program, which would
only occur at some time in the future.
-------
SECTION II
RECOMMENDATIONS
Monitoring should be continued on the Wareham farm where a
drainage system consisting of 4-inch (10.2 centimeters)
diameter perforated corrugated plastic pipe was installed
during the spring of 1973. In particular, the long-term
benefits in skimming the less saline groundwater flows should
be established, as well as evaluating the length of time
required to reclaim this cropland to allow the production
of higher cash value crops.
A thorough analysis of desalting technology should be under-
taken as applied to reducing salt loads from irrigation
return flows. Most desalination studies are geared towards
producing high quality effluents for satisfying municipal
or industrial water demands. For irrigation return flows,
considerable economies can be realized by removing only a
fraction of the total salt load (e.g., reducing salinity
concentrations by one-half or two-thirds),
An overall salinity control program for Grand Valley will
require a combination of canal and lateral lining, on-farm
irrigation improvements, and drainage facilities. The cost
effectiveness of each salinity control measure should be
developed, which would relate cost of the measure to the
reduction in salt load reaching the Colorado River. Then,
the optimal use of drainage facilities in combination with
the other salinity control measures can be established.
This analysis would not only provide the cost distribution
among the various measures, but would also provide guide-
lines as to the timing sequence for implementation.
-------
SECTION III
INTRODUCTION
STATEMENT OF THE PROBLEM
The necessity for coordinating irrigation, drainage, and salin-
ity control activities in arid regions of the world has been
repeatedly described since the earliest times in recorded
history. Relics of abandoned irrigation systems, alkali
deserts, and saline water resources are evident from the
Tigris and Euphrates River Basins to the Rio Grande in New
Mexico and Texas. In each historical case, the rapidity
with which drainage problems developed into local crises and
often regional concern has been startling (Luthin, 1966) .
One of the more recent cases where irrigation, drainage, and
salinity have become factors in the development of water for
societal needs is in the Colorado River Basin (Figure 1). The
problem has taken on a new dimension in that the sources of the
salinity are generally not the bearers of the damage. As a
result, concerned parties from each of the seven basin states
and the Republic of Mexico have become actively engaged in
finding technical and political remedies for the mounting
salinity concentrations.
The U.S. Environmental Protection Agency (EPA) is one
of the institutions involved with managing the quality of
the river flows and is the agency directed by federal man-
date to alleviate water pollution problems. In response, the
EPA has launched comprehensive research, development, and
demonstration programs to upgrade salinity control technol-
ogy to the level necessary to combat the problem on a basin-
wide basis.
Since a significant portion of the total salt load being trans-
ported by the river is derived from irrigated agriculture,
the initial studies have been directed towards improving irri-
gation systems. One of the several important efforts to
develop salinity control technology has been the Grand Valley
Salinity Control Demonstration Project located in the irrigated
confines of the Grand Valley in western Colorado (Figure 2).
THE STUDY AREA
The Grand Valley area is among the most significant sources of
salinity in the Colorado River Basin. Water entering the near-
surface aquifers in the valley become heavily laden with salts
dissolved from the marine soils and shale occurring extensively
in the area. The primary source of salt is the Mancos Shale
-------
Figure 1. The Colorado River Basin.
-------
en
Grand Valley Salinity
Control Demonstration
Project
Gunnison
River
Figure 2. The Grand Valley of Colorado.
-------
formation, which was formed by the alternate advance and
recession of prehistoric inland seas once dominating the
western United States. Since most of the water contacting
these aquifers comes from conveyance (canals and laterals)
seepage and deep percolation from overirrigation, the emphasis
of salinity control technology is in improving both the
conveyance (water delivery) and farm subsystems.
Agricultural Land Use
Early explorers envisioned the Grand Valley as a poor risk
for agriculturally related activities because of sparce rain-
fall. However, the first pioneering farmers rapidly sur-
mounted this restriction by irrigating with water diverted
from the rivers entering the valley. Through a long strug-
gle, an irrigation system evolved to supplement the other-
wise meager supply of precipitation during the hot summer
months (Figure 3). In time, the ageless futility of irri-
gation without adequate drainage was demonstrated in the val-
ley when the low lying acreage became waterlogged with highly
saline groundwater. Today, the failure to completely over-
come these conditions is still evident as illustrated by a
summary of agricultural land use in the valley presented
in Figure 4, where most of the acreage of phreatophytes and
barren soil, as well as much of the pasture acreage, is the
result of drainage problems.
Irrigation Practices
Furrow irrigation is the prevalent method of applying water
to croplands in the valley. Small laterals carrying one to
five cubic feet per second (cfs)* divert water from irri-
gation company or district operated canal systems to one or
more irrigators. Water then flows into field head ditches
where it is available to supply the growing crops and main-
tain a salt balance in the root zone. The agricultural
economy, consisting mainly of alfalfa, corn, sugar beet,
orchard, and small grains, is served by a more than ade-
quate water supply. In fact, the 70,830 acres of land under
this type of cultivation enjoys a total diversion of more
than eight acre-feet per acre during normal years. Consid-
ering that the evapotranspiration of these lands is usually
less than three acre-feet per acre, it is obvious that
existing irrigation efficiencies are extremely low.
The variation in the local climate separates the agricul-
tural setting into three primary regions. In the eastern
*For conversion to metric units, see SECTION XI.
-------
GRAND JUNCTION, COLO.
Alt. 4843 ft.
8.29" annual
c
o
o
-------
120
100
O)
0
< 80
O
O
o^
c
i so
0
0>
w.
0
0>
en
^ 40
T3
c
O
_l
20
0
-
-
S~
Sugar Beets
Orchards
Grain
Idle
Pasture
Corn
Alfalfa
Irrigable
Croplands
^Miscellaneous
Industrial
Municipal
Municipal-
Industrial
Open Water
Surfaces
Phreatophytes
Barren
Soil
Phreatophytes
and
Barren Soil
Open Water
Municipal -
Industrial
Phreatophytes
and
Barren Soil
Irrigable
Croplands
Total
Figure 4. Agricultural land use in the Grand Valley
(Walker and Skogerboe, 1971).
-------
end of the valley, the protective proximity to the abrupt
Grand Mesa results in some extension of the growing season,
allowing apple, peach, and pear crops to mature. In the
western part of the valley, the primary emphasis is on pro-
ducing corn, alfalfa, sugar beets, and small grains. Be-
tween these two regions is a transition zone of small farms
and the urban setting of Grand Junction. The farms in this
area are particularly affected by adverse drainage conditions
while contributing large salt loads to the river. Because
of these conditions, this project was set up encompassing
a small area within this region (Figure 2).
PURPOSE OF STUDY
The purpose of this project has been to further the devel-
opment of technology needed to improve the quality of flows
in the Colorado River by evaluating the effects of improv-
ing both structural and non-structural components of irri-
gation systems as a means of minimizing groundwater flows
contacting the saline subsurface soils and geologic forma-
tions. The initial phases were begun in 1968 to evaluate
canal and lateral linings as salinity control measures.
Those results, reported by Skogerboe and Walker (1972a)f
demonstrated the need for further investigations concerning
the on-farm water management practices. As a result, a
second and third phase program was undertaken to determine
the feasibility of two farm management improvementsirri-
gation scheduling and drainagein controlling salinity.
The results of the second phase are reported in the pre-
vious project report entitled "Evaluation of Irrigation
Scheduling for Salinity Control in the Grand Valley". This
report is presented to summarize the findings related to the
third phase, field drainage. The experience and data gener-
ated by the first and second phases of this project have
been important prerequisites to the successful conclusion
of this study.
The test area is characteristically operated by small unit
farmers and the soils are severely affected by the high
water table conditions. Agricultural productivity, there-
fore, is not presently sufficient to support most of the
occupants and many have outside jobs in local businesses
or industry. Besides evaluating drainage as a salinity
control measure, one of the concerns of the investigators
was in demonstrating the benefits of drainage to the indi*-
vidual land owners. These lands were once among the valley's
most productive (at the turn of the last century) and a
significant impetus could be generated locally in support of
salinity control programs if such a measure was instru-
mental in increasing agricultural productivities of these
salt-affected lands.
10
-------
SCOPE OF THE STUDY
Five fields in the area, located in Figure 5 and described
in Table 1, were incorporated in the study to represent a
cross-section of agricultural practices in the Grand Valley.
Three of the farms (Kelleher, Canaday, and Wareham farms)
were included primarily as part of the drainage investiga-
tions, while the remaining two (Bulla and Martin farms)
were specifically used for evaluating irrigation scheduling.
During the 1972 irrigation season, irrigation practices
were monitored on the Kelleher, Canaday, and Wareham farms.
Then, during the spring of 1973, a perforated plastic pipe
drainage system was constructed on the Wareham farm. All
three farms were then incorporated into the irrigation
scheduling program during the 1973 irrigation season, which
was done cooperatively with the U.S. Bureau of Reclamation
(USER) valley-wide irrigation scheduling program, thereby
strengthening the results of both studies. At the same
time, drainage outflows were monitored from the Wareham
farm.
In addition to the drainage-related evaluations, data
collection and analysis activities relative to the impor-
tant hydro-salinity parameters in the test area were main-
tained to provide continuity with earlier data. The
investigators concluded that such efforts were necessary
to detecting any changes relative to the improvement of
water management practices in the area and to refine
the results of the earlier studies, if desired. Of course,
the size, scope, and detail with which any research effort is
conducted must be compromised with time, talent, and
funding provided to the researchers. A workable balance
was achieved in this project while maintaining a high
degree of sensitivity towards the goals of the project.
11
-------
Stub Ditch
ro
Government
Highline
Canal
Figure 5. Location of study farms in demonstration area.
-------
Table 1. DESCRIPTION OF FARMS IN THE DEMONSTRATION AREA
INCLUDED IN THE DRAINAGE AND IRRIGATION SCHEDU-
LING STUDIES
Farm
Martin
Bui la
Canaday
Kelleher
Wareham
Crop
Corn
Barley
Corn
Barley
Oats
Pasture
Alfalfa
Crested
Crop
Acreage
9.2
10.7
15.0
17.1
9.8
1.0
17.4
13.6
Field
Capacity
22.3
24.2
23.9
26.5
25.0
25.8
30.5
29.3
Wilting
Point
10.7
13.4
12.1
12.8
12.2
14.1
16.7
16.7
Wheatgrass
13
-------
SECTION IV
PREVIOUS DRAINAGE INVESTIGATIONS
GENERAL
The inadequacy of both natural and man-made drainage systems
in the Grand Valley have been repeatedly demonstrated by
high water tables, flooded basements, and insect problems.
During the final two decades of the last century, the local
soils supported an agricultural system of orchards, forage
crops, small grains, and gardens. By about 1905, however,
there began to be an increasingly significant acreage affected
by poor drainage and crop production began to decline.
Efforts to remedy these conditions were often off-set by
additional acreages being irrigated, especially after the
implementation of the Grand Valley Project of the Bureau
of Reclamation. Today, almost 30% of the irrigable acreage
in Grand Valley supports only marginal valued pasture, hay,
and grain fields.
Drainage in the valley has passed through three major eras.
First, as the early drainage problems were encountered
between 1890 and 1908, the U.S. Department of Agriculture
conducted extensive surveys to define the cause of the pro-
blems. Results of that first study formed the basis for
the second period between 1915 and 1945 when the Grand
Junction Drainage District evolved. Finally, the interval
between 1945 and 1960 marked a period of specialized study
instigated to evaluate specific drainage and land reclama-
tion alternatives.
In this section, it is the intention of the authors to summar-
ize the findings of these periods as a means of correlating
them with the results of this study.
EARLY DRAINAGE INVESTIGATIONS
The high salinity content of the substrata and the lack of
natural drainage were quickly recognized as the major drain-
age problems in the Grand Valley. Consequently, in 1908
the U.S. Department of Agriculture through its Office of
Public Roads and Rural Engineering initiated local drain-
age studies to delineate the specific nature of the problem
and suggest appropriate remedies (Miller, 1916).
This study encompassed the valley lying north of the Colo-
rado River between Palisade and Loma. At the time, the most
predominant agricultural enterprise was the fruit industry
which also exhibited the first signs of rising groundwater
levels. This period pre-dated the construction of the
14
-------
Government Highline Canal, indicating that conditions would
worsen and a solution would be needed in the immediate future.
To accomplish the goals of the project, research was con-
ducted in four major areas: (1) nature and characteristics
of the soils and subsoils; (2) groundwater; (3) local
salinity problems; and (4) description of the irrigation
waters.
Nature of Local Soils
Silt and clay constitute the principal elements of all the
soils except in what is known as the Billings fine sandy
loam which primarily contains very fine sand. Even though
these soils are often difficult to till and crust readily
if flooded during irrigation, they are nevertheless very
productive.
Miller (1916) found that most of the soils examined were
deep and relatively uniform in nature through the upper soil
profiles. An underlying gravel aquifer was identified
throughout much of the area ranging in depth below the soil
surface from five feet to more than 30 feet. As a means of
establishing the physical dimensions of the cobble aquifer,
fifteen experimental wells were drilled to the underlying
shale, and information was collected from local residents
who had installed wells to water livestock.
Groundwater
The groundwater levels in the Grand Valley area have been
steadily rising since irrigation was introduced. They had
also been increasing in salt content during this interval,
with concentrations at the time of the study of about 10,000
ppm in some localities. The salinity consisted of about
60 percent sulfates, 30 percent chlorides, and 10 percent
bicarbonates and nitrates.' In the early history of the
valley, it was common practice to dig wells to the under-
lying gravel in order to obtain domestic and stock water
during the winter months when the canals were shut down. As
irrigation increased, the water from many of these wells
became so badly alkaline as to be entirely unfit for human
drinking purposes and generally so for stock. By the time
Miller's study was initiated, only a few wells at either
end of the valley were in use.
Salinity Conditions
In connection with the work that was being conducted by
Miller (1916) in the valley, a total of 392 soil samples
15
-------
were collected from 22 tracts of land lying north of the
Denver and Rio Grande Railroad line between Clifton and
Fruita. The samples, which were submitted to the U.S.
Bureau of Soils for analysis, indicated an average constit-
uent content of: (1) calcium sulfate or gypsum, 49.5 per-
cent; (2) sodium chloride or common salt, 13.6 percent; (3)
sodium sulfate or Glaubers salts, 10.4 percent; (4) magnesium
sulfate or Epsom salts, 9.7 percent; (6) calcium chloride,
2.1 percent; (7) magnesium chloride, 1.6 percent; and (8)
nitrates, 2.1 percent. A reclassification of the above
results gives: (1) gypsum, 49.5 percent; (2) sulfates,
other than gypsum, 20.1 percent; (3) chlorides, 17.3 percent;
(4) bicarbonates, 7.5 percent; and (5) nitrates, 2.1 percent.
Quality of the Irrigation Water
Irrespective of the action of capillarity as a factor in
the accumulation of the alkali salts in certain soils of
the Grand Valley, due consideration was given to the quan-
tities that may have been deposited through the application
of irrigation water. The nature of the salts in the Colo-
rado River at this time did not differ markedly from data
being collected today.
Recommendations
The primary recommendation from the study was to construct
an open drain system that would penetrate the underlying
cobble aquifer. In addition to the open drain system, it
was proposed that tile lines running north and south through
the area and spaced at 1/4 mile intervals should be installed.
It was felt at this time that the system described above
would provide a workable solution to the drainage problem in
the area.
The cost of such a system was, at best, difficult to esti-
mate, but using construction cost figures in 1916 the
average per acre cost was somewhat less than $35.00.
In his summary, Miller (1916) made the following statement.
"The drainage of much of the land of the valley is practicable
only under community organization, and not then unless a
thorough system of drainage be installed in accordance
with plans based upon full knowledge and appreciation of the
underlying conditions." Although the construction of Miller's
drainage plan was not immediately undertaken as suggested,
no doubt he had much to do with the formation of the Grand
Junction Drainage District.
16
-------
GRAND JUNCTION DRAINAGE DISTRICT
By 1915, the fact that the drainage problem was almost valley-
wide and the realization that the upper lands and canals con-
tributed to the lowland problem were generally accepted. With
the plans for the construction of the Government Highline
Canal nearing approval, valley residents in accordance with
the recommendations of Mr. Miller began thinking of a valley-
wide drainage system. On September 7, 1915, a three member
board of directors met in Grand Junction to organize a drain-
age district. Business included the election of Gus. J.
Johnson as president of the Board and the selection of "The
Grand Valley Drainage District" as the name of the organi-
zation. Following this meeting, the proper legal papers
were drawn up and sent to the State Capital for approval
and formal recognition of the district. In November of
1915, the Drainage District contracted with the U.S. Depart-
ment of the Interior to conduct a feasibility of the drain-
age possibilities, including a plan with an accompanying
cost estimate.
On April 24, 1917, the Board of Directors received notice
that the preliminary study had been completed and a tentative
design formulated. The letter also revealed that the system
would cost approximately 1.7 million dollars which because
of budget restrictions could not be financed by the Federal
Government. To a valley with a population of less than 12,000,
the thought of raising this much money was staggering, thus
making the full-scale drainage system impossible. As an
alternative, a much smaller project was proposed. Since
the Highline Canal currently under construction would need
wasteways for unused water, the Government suggested
that many of the natural washes be combined with man-made
wasteways at such a depth as to remove the waste water
and provide some lowland drainage. Although the cost was
still almost $300,000, it was connected with the Federal
irrigation project and thus could be financed through
existing arrangements. Under this proposal, the Drainage
District was responsible for providing rights-of-way
for all proposed drains and lifetime maintenance of all
channels.
The need for a method of obtaining revenue for the District
was now apparent. On May 21, 1917, the proposition to
assess the land owners in the valley based on the benefits
to be received was presented. Provisions were made on
May 29, 1917, to obtain the needed data which included the
name and address of each land owner, a description of the
land owned, and an estimate of the benefits to be derived
from the project. This information was then published by
the District, along with the estimated benefits to each
17
-------
piece of land. A period during which the land owners could
formally contest the estimated benefits was designated.
Having dealt with all protests, the District made the first
assessments on the land in the district on September 14, 1917,
Further negotiations with the Government resulted in a new
cost-sharing proposal on the smaller scale drainage project.
Under the new proposal, the Drainage District was to pay
40% of the right-of-way fees and 40% of the channel main-
tenance cost. These costs could be repaid over a ten-year
period at no interest, but at the end of the 10-year period
a new maintenance agreement would have to be developed.
In addition, if the District could not repay the debt in
the 10-year period, the loan could be extended at an interest
rate of 6% per annum. This proposal was approved by the
Board of Directors and a special election called for Novem-
ber 19, 1917, at which time the contract was approved and
signed.
Once the method for securing operating funds and entering
into the first construction contract with the Federal
Government had been resolved, the Drainage District began
formal operation. Many agreements for rights-of-way were
made and channels constructed during the period from 1918
through 1923. The size of the system to be maintained grew
to the extent that superintendents were needed to handle
the work. Thus, on February 12, 1921, M.G. Goucher and
A.A. Jones were hired as superintendents of maintenance and
construction.
On June 6, 1923, the name of the organization was changed
to "The Grand Junction Drainge District" by a vote of the
people. Provisions were also made for regular elections for
members of the Board of Directors.
August 1, 1923, is possibly the most important date in the
history of the District. Faced with the task of enlarging
the drainage system, the District encountered the critical
question of how to raise the needed capital. Many sugges-
tions for obtaining capital were put forth and two of them,
namely, selling bonds and a tax mill levy, were placed on
the ballot of a special election held on this day. Fortun-
ately for the drainage program in Grand Valley, the people
voted in favor of the mill levy. The tax levy was set at
4 mills, which in 1923 amounted to approximately $70,000;
for operation of the Drainage District.
Thoughts again centered on a major full-scale drainage
system for the valley. The Reclamation Service plans were
revived and modified. A call for bids went out on December
11, 1923, and the low bidder was the Winterburn and Lumsden
18
-------
Construction Co. The contract was signed and construction
began on a major open channel drainage system which comprises
much of the present day drainage system.
The present boundaries of the District are shown in Figure
6. The District has approximately 400 miles of open channel
and 150 miles of tiled drains within its boundaries. The
open channels are quite evenly dispersed throughout the
valley, whereas most of the tile lines are found under the
orchards near Palisade. With current policy, the District
handles the construction of open drains and installation of tile
drains, as well as normal maintenance on all drains after con-
struction, at no cost to the farmer. The farmers are required
to provide the rights-of-way for open drains and all materials
used for tile drains (gravel and pipe). It is interesting
that the specifications used by the District are the same
ones used on the original Government contracts, although
some limited modifications to bring them up to date have
been included.
RECENT DRAINAGE INVESTIGATIONS
Drainage investigations in the Grand Valley have been con-
ducted almost continually since the work of Miller in the
early 1900's and the subsequent formation of the Grand
Junction Drainage District. With the advent of World War
II and the need for higher crop production, the value of
irrigated land greatly increased. This brought forth a
new call for improved drainage in the valley, along with a
willingness for both individual and Government funding. In
answer to this call came renewed effort by Government
agencies to solve the problem. A committee was formed which
included members from the Soil Conservation Service; Bureau
of Plant Industry, Soils, and Agricultural Engineering
(BPISSAE); and Colorado ASM College. A summary entitled
"Progress Report on Drainage Project, (1945 to Jan. 1951),
Lower Grand Valley S.C.D., Mesa, Co., Colorado," was
prepared in July, 1951, by Rey S. Decker, Head, Regional
Drainage and Earth Testing Section of the S.C.D. (Decker,
1951).
Initial Investigations
A project area was selected for intensive study in a locale
about five miles northwest of Grand Junction, covering about
4500 acres. A community known as Appleton was located
along the east central boundary of the project area, an
area that was also included in the Miller study in 1908.
19
-------
Area within the drainage
district boundary
to
o
Figure J. Boundaries of Grand Junction Drainage District.
-------
This area contained a number of apple orchards at the time
of Miller's study, but by 1945 there were no commercial
orchards remaining.
A number of drains had been installed in the area during the
period 1924-1945 by the Grand Junction Drainage District.
While these drains provided an outlet for field tailwater
and surplus irrigation diversions, they were not particu-
larly effective in alleviating the drainage problem in the
project area. It was not uncommon to find the water table
within a few inches below the ground surface of the surface
observation wells located on the banks of deep 8 foot -
10 foot drains. Some drains located near the river, where
gravel could be tapped, appeared to function satisfactorily
as was predicted by Miller (1916).
At the time of these later investigations, it was difficult
to fully evaluate the effectiveness of the existing drainage
system. According to Miller (1916) , the water table was
rising in 1916, and yet in 1945 it was at nearly the same
level as in 1916. The system evidently prevented any
additional rise in water table levels and undoubtedly bene-
fited the remaining cultivated acreage.
The Soil Conservation Service (SCS) drainage investigations
were initiated in early 1946 through a request for assis-
tance. A farm known as the Willsea farm, located in the
south central portion of the project area, 1 mile south
and 1/2 mile west of the Appleton corner, was selected for
intensive study. Conditions on the 160 acres were severly
salt affected and most of the land had been abandoned.
A number of piezometers were installed on the farm in early
1946. Dr. Fireman and Mr. Reeves, U.S. Regional Salinity
Laboratory, were working in the area during the summer of
1946 in connection with the B.P.I.S. & A.E. and Colorado
A&M soil survey and became interested in the Willsea project.
Several additional piezometers were installed under their
direction and the data analyzed. The results of the piezo-
meter data indicated an upward flow condition in the area.
In one case, the loss of head in the vertical direction was
3.37 feet in a vertical distance of 7 feet (from the 14
foot to 7 foot piezometers), or a vertical hydraulic grad-
ient of 0.48 feet. Information indicated that the water is
brought into the area through the underlying cobble aquifer
at a depth of between 14 and 21 feet. Since the subsurface
soils had such a low hydraulic conductivity, the surface
drains, which range in depth from 10-12 feet, were ineffective
in removing the upward flow of water.
21
-------
The possibility of pump drainage to relieve the vertical
gradients in the area was considered early in 1947. In
April, 1947, an 8 inch well was drilled by Mr. Willsea.
The drillers log showed the first eighteen feet were local
soils, followed by three feet of sand, three feet of tight
clay and ten feet of cobble and gravel. An 8 1/4 inch
casing, set on the bottom of the hole, was perforated at
depths of 18-20 feet and 24-34 feet. Water rose in the
casing to within 6 feet of the surface and was bailed out
at about 40 gallons per minute (gpm) with no apparent
drawdown.
This well was tested by SCS personnel on April 5, 1947, by
continuous pumping for five hours at a maximum discharge of
100 gpm. A drawdown of 12 feet was effected in about 1/2
minute, but the water level could not be lowered beyond
the 18 foot depth. Also, no changes in water table eleva-
tions were.measurable in piezometers 150 feet from the
well at the end of the pump test.
Although the Willsea pump test was not entirely successful,
the Soil Conservation District supervisors and cooperators
were now aroused to the possibilities of pumping for drainage,
A general plan of investigation was prepared by the regional
and district offices for discussion and approval by the
supervisors.
A working agreement between the Lower Grand Valley Soil
Conservation District and the Grand Junction Drainage
District was executed in early 1948. The area was gridded
with twenty-five deep test holes to determine the depth to
gravel and pressure potential. Most of these holes were
40-50 feet deep with one extending to 78 feet. Hydrostatic
pressure was encountered in most holes upon contact with
the gravel, and water actually flowed from many of the
holes for several days or even months after they were put
down.
Upon completion of the deep hole grid and analysis of the
data relative to depth to gravel, hydrostatic pressure, etc.,
24 sets of 3/8 inch piezometers were installed. Piezometric
installations varied from sets of 2 pipes 7 and 14 feet in
length to sets of 3 pipes 7, 14, and 28 feet, or longer.
A total of 60 pipes (865 feet) were installed on the project.
Water level readings were started in May, 1948, and contin-
ued at intervals of 2-4 weeks until December, 1949.
Due to the limitation of the jetted and augered holes,
it was impossible to determine the thickness of the gravel
substrata using these methods. Since the thickness of the
aquifer is very important in determining hydraulic
22
-------
characteristics of the material, a method for determining
the thickness had to be found. In order to gather this infor-
mation, Mesa County, through the County Soils and Drainage
Committee, provided $800 for drilling six test wells. Each
well was six inches in diameter, and all but No. 6 (which
was abandoned because of insufficient funds) were drilled
through clay and gravel into the underlying shale to a
depth of five feet. Samples were taken from all formations
encountered during drilling and then were analyzed. Addi-
tionally, a number of water samples from various wells,
piezometers, drains, and the rivers were collected during
the summer of 1949. A summary of these sample analyses is
presented in Table 2.
All investigational data collected on this project pointed
to the provision for adequate drainage as the first require-
ment in reclamation and rehabilitation of the project area.
The deep artesian aquifer under the entire area, the presence
of upward groundwater flow, and the ineffectiveness of deep
open drains in the area all pointed toward pump drainage
as the proper method, regardless of just where and how the
water enters the aquifer or what causes the variation in
pressure.
Field Evaluation of Pump Drainage
With the completion of the feasibility studies and esti-
mates, the decision was made to install a drainage well
at Bethel Corners. Tentative plans for construction of
the well were as follows: A 24-inch diameter well with a
screen 25 feet long would be installed at the bottom of the
hole and surrounded by a 6-inch gravel pack. This 25 feet
is in a fine gravel and sand formation. The remaining 30
feet/ which is in a heavy billings silty clay loam soil,
would be cased with a 12-inch standard steel pipe. There
was still some question as to the necessity or desirability
of a gravel pack, but further evaluations led to its exclu-
sion.
During the next Board meetings, the plans and financing by
public subscription were approved. The Mesa County Agri-
cultural Research Committee donated $1700, with the remaining
$1800 being contributed by local business firms, banks,
public utilities and service clubs. In addition, the Grand
Junction Drainage District agreed to pay for the necessary
power for pump operations with the Public Service Company
of Colorado contributing the power line. The job was com-
pleted in the latter part of June, 1951. The drillers
log and casing construction are shown in Figure 7.
23
-------
Table 2. SUMMARY OF WATER QUALITY SAMPLES TAKEN FROM TEST WELLS DURING 1949 (DECKER,
1951).
Sample No.
TDS Calcium Magnesium Sodium Chloride Sulfate Bicarbonate
(ppm) (ppm) (ppm) (ppm) (ppm) (ppm) (ppm)
1
2
3
4
5
6
Sample No.
1
2
3
4
5
6
9794 672 379 1897 860
9915 700 414 1848 868
2750 476 103 196 140
5585 644 224 744 234
1081 115 27 192 240
941 156 34 66 22
Source and Notes
Well 10 feet into gravel aquifer, located in
Willsea well
Local piezometer 6 feet deep
Spring at foot of Fruitridge
Leach water (drainage interception)
Colorado River at 5th Street Bridge
Gunnison River just north of AEC Compound
5547 427
5560 425
1525 310
3393 346
273 234
448 215
deep drain near
-------
Drainage Well
Construction
Drillers Well Log
12" Spiral Welded
Steel Pipe 7 go.
25' Brass
Well Screen
1/8" Openings
Clays,
Sandy Clay,
a
Silty Clay
Cobbles
Gravel
Sand
Shale
\VN\X\
[>^\*
KSX\-^I
. i
Figure 7. Drillers log and well construction
Depth, Ft.
l- 0
- 10
- 20
-30
-40
-50
L-60
25
-------
After the well-developing procedure had been concluded, a
pump test of 30 hours duration was conducted. The well
yielded an average flow rate of 250 gpm during the test,
which was far below the estimated yield of 600 to 900 gpm.
The pump was started for continuous operation on October
25, 1951, and except for numerous power failures, per-
formed satisfactorily. By the end of 1951, the water level
in the cobble strata had been lowered 12 feet at a distance
of 50 feet from the well, 6 to 8 feet at 400 feet from the
well, 1 to 3 feet at 1,600 feet from the well, and 1 to
1.4 feet at 3,200 feet from the well. Water levels in
the clay loam soils were lowered between 0.22 feet and 1.50
feet during the same period. As can be seen from this pre-
liminary data, the well was having a pronounced effect on
the water table in the surrounding area.
The water table continued to decline steadily during the
first four months of 1952. However, during May there was
a sharp decrease in the rate of decline. Since the irri-
gation water was turned into the system about April 1 and
field irrigation was begun during April, it was believed
that the decline in the rate of lowering of the water
table was due to the increased flow of water in the area.
Data collected in later years bore out this assumption.
The salinity of the water over the first period of pumping
remained fairly constant at about 1 percent salt. The
flow rate from the pump was increased from 175 gpm to 280
gpm in March of 1952 by adjustments made on the pump.
In 1952, plans for the second stage of the project were
finalized and the work began. This consisted of 16 test
plots 30 by 60 feet located on the farm bordering the well
in the northwest section. This ground was not completely
abandoned, but was in very poor condition. The principal
objective of this phase of the project was to determine if
the ground could be reclaimed after the water table had
been lowered by pumping.
The plots were leached and the crops planted. These inclu-
ded alfalfa, sugar beets, grain, and corn. Since this
project entailed much more than just drainage, a detailed
discussion will not be presented here. At this point, it
is sufficient to say that while the pump was operating,
it was possible to produce "normal" crop yields in this
area with very careful management. This bears witness to
the fact that the well was a solution to the drainage
problem in this area at the time (Shumaker, et al., 1967).
The pump was shut off on February 14, 1955, with the almost
immediate result being an increase in the head in the aqui-
fer. The water table did not begin rising immediately since
26
-------
the aquifer is overlain by a dense clay layer with very low
permeability. However, since this layer is not continuous,
the water table was eventually affected. By the end of the
growing season, the water table under the plots on the local
farm had risen 3-4 feet.
The pump was used on a part-time basis until 1959, but
only to protect the crop rotation plots in the land recla-
mation study. To the authors' knowledge, the pump has not
been operated since 1960.
A drive through the area today finds the pump still there,
but it is crusted with salt and overgrown by weeds. The
farms that were restored to productivity have once again
gone back to growing only highly salt-tolerant native
vegetation. For it seems that while the method was shown
to be effective, the owners of the surrounding property
were either unwilling or unable to support the cost of
operating the pump on the income from agriculture.
27
-------
SECTION V
DRAINAGE DESIGN METHODS
The primary purpose of drainage systems for agricultural
lands is to provide a soil environment including air and
water which can productively support plant growth. The
design of drainage systems should consider the nature of
the crops, soils, climate, and local practices in order that
the following basic factors in drainage be identified
(Corey, 1961) :
1. The depth to which the critical oxygen diffusion
rate necessary for plant growth occurs;
2. The maximum allowable soil moisture content which
allows the critical oxygen diffusion rate;
3. The design method for determining drain depths
and spacings which incorporates the most sensi-
tive characteristics in the soil environment; and
4. The design which accounts for special events such
as long-term reclamation of the soils.
Although these basic factors represent the ideal approach
to drainage, the data necessary to evaluate each factor are
generally lacking and design must be made on the basis of
sound judgement and previous experience.
The existing drainage design techniques have been categorized
into four major approaches (Hedstrom, et al., 1971, and
Corey, 1961):
1. Use of drainage coefficients;
2. Establishing an optimum water table depth;
3. Designing for a specified rate of water table
decline; and
4. Incorporating a fluctuating water table system.
Each of these design approaches apply to different types
of drainage conditions, and thus, the selection depends on
the requirements of the sets.
DRAINAGE DESIGN METHOD FOR GRAND VALLEY
In the Grand Valley area, the most important considerations
for selecting a drainage design method are the characteristics
28
-------
of an irrigated agriculture in a semi-arid climate. In
addition, a special consideration must be made for the ar-
tesian conditions produced by the partially confined cobble
aquifer discussed by Skogerboe and Walker (1972a). Since
the upward movement of groundwater is generally not en-
countered in the test area, a discussion of drainage when
vertical gradients exist will be left until a later section.
Under the conditions noted above, two methods of drainage
design seem most applicable: (1) optimum water table and
(2) falling water table. In the following paragraphs, the
most commonly used techniques in these categories will be
discussed.
Optimum Water Table
The optimum water table approach is a steady state solution
used throughout the world in humid areas having low inten-
sity and long duration rainfall patterns. The Soil Con-
servation Service, U.S. Department of Agriculture, has
adapted this approach for use in arid and semi-arid regions
on irrigated lands by assuming the irrigation to be a uni-
form recharge event distributed over the irrigation inter-
val.
Most of the initial work on this approach was done by
Dr. S.B. Hooghoudt of the Netherlands and is based on the
physical model depicted in Figure 8. The model makes the
following assumptions:
1. The recharge rate to the water table is constant
in time and space;
2. The flow into the drains is equal to the flow
reaching the water table (i.e., steady state);
3. The drains are parallel and at the same depth;
and
4. The drains perform in a similar manner to open
drain ditches in that no flow crosses the tile.
Based on continuity considerations and Darcy's law, the
Hooghoudt equation is developed (U.S. Department of
Agriculture, 1971),
4Kh
s* - -- ( + 2d)
29
-------
Recharge rate w
///////////////////////////////////////////////////////////// stratum
Figure 8. Model for Hooghoudt's steady state drainage equation (Ayars, 1972)
-------
where S = distance between drains, feet
K = hydraulic conductivity, inches/day
w = uniform recharge rate, inches/day
hm = height of water table at mid-point between
drains, feet
d = saturated depth below the drains, feet.
The first step in using the equation is to select an opti-
mum depth for the water table based on individual crop needs,
or by previous experience in the area. A value for the re-
charge rate is then selected. In humid regions, this can be
a drainage coefficient, while in arid regions it would be
equal to the deep percolation from an irrigation. Next, the
depth to the impermeable boundary is established from sub-
surface exploration. The saturated depth below the drain
(d) is then calculated as being equal to the depth to the
barrier minus the depth of drain. The value for the height
of the water table at the midpoint of the drains (h ) is
equal to the depth of drain minus the selected deptK of
the water table. Once a depth of drain is selected, the
spacing can be computed and a cost of construction esti-
mated. If the values of d are large, Equation 1 is not
valid and a corrected depth, d', is determined from curves
prepared by Dr. Hooghoudt (Luthin, 1966).
Falling Water Table
The falling water table, or transient analysis, was developed
by engineers of the U.S. Bureau of Reclamation for use in
design of irrigation projects in arid and semi-arid areas.
This method attempted to incorporate the transient nature of
irrigation water and as many of the soil and groundwater
conditions as possible. This development was considered
necessary because most of the work in drainage prior to
this time was accomplished assuming steady state conditions or
had been developed to meet the needs of a particular area
(Dumm, 1954). The model used in the development is sche-
matically shown in Figure 9. The following conditions are
assumed to exist:
1. The total recharge reaching the water table due
to irrigation or precipitation is assumed to be
instantaneous (i.e., the water table ele-
vation is raised instantly to a new elevation);
2. As flow into the open drainage ditches occurs,
the water table descends and drainage from the
soil keeps pace with the descent of the water
table, assuming that the region above the water
table is completely drained; and
31
-------
Soil surface
Figure 9. Model of the transient drainage equation (Ayars, 1972)
-------
3. Flow above the water table is assumed to be zero.
Again, the continuity equation for the model shown in
Figure 9 is combined with Darcy's law; and the flow
section h + D is assumed to equal some average value D,
the equation is given as;
a a2" = 9h (2)
3x2 9t
in which,
KD
where h = height of water table above the drains, feet,
K = hydraulic conductivity, inches/hour,
d = specific yield of soil,
t = time, hours,
D = depth of flow below drains, feet
x = distance measured horizontally from the drain, feet.
Solutions to the equation are in the form of a Fourier
series, which are dependent on initial and boundary condi-
tions. Solutions which originated in the field of heat
transfer have been applied to the groundwater field in
equations known as Glover's equation, the transient equa-
tion, and also the Bureau of Reclamation equation.
A particular solution of the transient equation is used
by the Bureau of Reclamation in conjunction with the con-
cept of "dynamic equilibrium". In using this concept,
the elevation of the water table is permitted to fluctu-
ate during the growing season, but the long-term average
elevation is fixed. Use of the equation also requires
determining the depth to barrier, the hydraulic conductiv-
ity and specific yield of the soil, and developing a
schedule of recharge events. Having established these
factors, the depth of the drains can be varied and the
maximum spacing based on deep percolation can be computed.
Since this equation is used primarily in arid and semi-
arid regions, the water table depth is usually assumed to
be at least four feet in order to prevent evaporation of
groundwater from the soil surface and an accompanying
accumulation of salts.
Dumm (1964) reported that Glover originally solved
Equation 2 for the case of the drains located above an
impermeable barrier by assuming a horizontal water table
as the initial condition. In subsequent solutions by
Tapp and Moody (Dumm, 1967) , the assumption of an initially
33
-------
CO
192 I
TT3 n=l,3,5,
n-1
(-1) ~2~
n2--*
TT2
n5
TT2n2at
L2
horizontal water table was not considered an accurate
representation, so the water table shape was changed to a
fourth order parabola. This solution is currently used by
the Bureau of Reclamation. The Fourier series solution
of the transient equation for the height of the water
table at the midpoint between the drains is:
y
C,t_ J-Jf. L, \ j. ; f. || n u \j, L. (~\\
where a = diffusivity Kd/s,
K = hydraulic conductivity, inches/hour
d = saturated depth below drain, feet
t = time, hours,
x = distance measured horizontally from the drain,
feet
y . = height of water table above the drain at
x/ distance x and time t, feet
c = midpoint between drains were x = L/2, feet.
The initial and boundary conditions used in the solution
are:
= rc,o (L3x - 3L2x2 + 4Lx3 - 2x")
x,o
Initial conditions:
. 8*c
L*
Boundary conditions: t>^0,x=OorL
y . = 0 and y_ . = 0
o,t L,t
Consideration must also be given to the physical situation
where the drains are located on the impermeable barrier.
Solutions to Equation 2 for this condition have been pro-
vided independently by Boussinesq and Glover (van
Schilfgaarde, 1970). The equation is:
L = 2S =- - 1
|9KHt
(4)
where L = spacing, feet,
K = hydraulic conductivity, inches/ hour
t = drainout period, days
S = specific yield, %
Z = saturated thickness of aquifer at distance x
from drains, feet,
34
-------
c = midpoint between drains, feet,
H = initial saturated depth at midpoint between
drains, feet.
The parameters are shown in Figure 10.
The decision to design the drains on or above the barrier
depends on the ratio of the saturated depth below the
drain to the height of water table above the drain at
the midpoint between parallel drains. Dumm (1964) reports
that if this ratio is less than 0.10, the drains should be
designed on the barrier, and if the ratio is greater
than 0.8, the design should use the equation for drains
over the barrier. If the ratio falls in the range 0.1 to
0.8, then the best judgment of the designer must be used
to select the proper method for solution.
The computations are started by assuming a depth and
spacing for the drain and a maximum water table elevation.
Using the recharge schedule, the depth of the water table
is computed for each recharge and drainout period through
the year until the starting point is again reached. If
the elevation of the water has returned to the originally
assumed elevation, the proper spacing for the given depth
has been selected. If this is not the case, a new spacing
is selected and the final elevation is then recomputed.
Usually, after two trials a straight line interpolation
between the computed values of the final water table posi-
tion will give the correct spacing. The computations
are begun with the last irrigation of the season, since
this is the time the water table elevation is assumed to
be highest. A first estimate of the spacing can be
made using the steady state Equation 1 with the value
for uniform recharge (w) being equal to the deep perco-
lation losses divided by the minimum recharge interval.
A computer program was developed by Ayars (1972) to
perform these calculations.
REFINEMENTS IN DRAINAGE DESIGN
In general, the equations used in these drainage designs
assume that the water table marks the upper boundary
of the saturated zone. This assumption implies that no
capillary fringe exists above the water table, that no
horizontal flow occurs above the water table, and that the
region above the water table is aerated to such an extent
that it can provide an acceptable environment for plant
growth. The validity of the assumption varies and is
primarily dependent on the texture and structure of the
soil. For example, a sandy soil would have a small
35
-------
Soil Surface
CT\
Initial position of groundwater
f
/
posMjor.^--3^
^.^~~ Permability-K
Specific yield-S
/////////////////////;
I ~1
///////////////A
. I _ _
r---^ \
7 "~~-. \
5 Impermeable
Stratum
Figure 10. Model for transient drainage equation on impermeable barrier.
-------
capillary fringe and the assumption would be fairly
good, whereas a fine textured soil with poor structure
would have a large capillary fringe and the assumption
that the water table marked the upper limit of the satur-
ated zone would be a poor one.
Duke (1972) developed a method using the Dupuit-Forchheimer
assumptions in conjunction with the mass continuity
equation in the following form:
= effective porosity as defined by Brooks and
e Corey (1964) ,
K = saturated hydraulic conductivity, inches/hour
Y = equivalent saturated thickness of aquifer, feet,
5
Y, = equivalent permeable thickness of aquifer, feet,
x = horizontal coordinate, feet
t = time, days
Q = volumetric flux rate, cfs.
The variables Y, and Y which account for the effects of
capillary flow and storage are defined by the equations,
Yk " Y + Hk (6)
Ys = Y + Hs (7)
where H, = equivalent permeable height above the water
table, feet,
H = equivalent saturated height above the water table,
s feet,
Y = saturated thickness of the aquifer, feet.
The effective porosity ((> and the variables H and H are
described using the soileproperty relationships developed
by Brooks and Corey (1964) , mainly the bubbling pressure,
pore-size distribution index, and the residual saturation.
Using these same soil property relationships, Duke also
defines an elevation (Z ) above the water table at which
the degree of partial saturation permits adequate soil
aeration. With application of flow theory in partially
saturated and saturated soils, Duke developed the relation-
ships needed to describe flow to drains from above and
below the water table.
From this analysis, it was found that the water table
fell faster when it was not as in the classical equa-
tions. This would mean that the classical equations give
37
-------
spacings that are too narrow. However, when the zone of
aeration is considered, the drain spacings have to be
reduced in order to maintain the required aerated zone.
This means that drain spacings computed using the
classical equations are too wide. The effect of the addi-
tional height of saturated soil negated the increased
rate of water table decline thus requiring spacings
narrower than those predicted by the classical theory.
Because the soils in the Grand Valley area have low
permeabilities, the adjustments proposed by Duke (1972) ,
will be made on the falling water table approach
developed by the Bureau of Reclamation.
FAILURE OF EXISTING SYSTEM
After analyzing methods of drainage design in the pre-
vious paragraphs, it is necessary to consider the type
of drains which should be used. Excess irrigation water
and soils with poor drainage characteristics have been
identified in the current study and in previous research
as the major cause for high water tables in the Grand
Valley. The attempts to alleviate these conditions to
date have largely involved open drainage ditches.
However, based on an analysis by Kirkham (1960), the
system of open drains cannot economically be made
effective in releiving the waterlogged condition. Kirkham
analyzed the problem of drainage of ponded fields overlying
a gravel substratum which is typical of the conditions
in Grand Valley. Based on this model, Kirkham concluded:
1. When the depth of the ponded water equals zero,
and if the drain spacing is greater than six
times the drain depth, the proportion of water
entering ditches through the wall will be small
compared to that reaching the ditches by under-
lying gravel;
2. If the depth of the ponded water and the water in
the drain each equal zero, then no water will
seep through the ditch walls provided the gravel
is infinitely permeable compared with the over-
burden; and
/
3. When the spacing is greater than six times the
drain depth, the influence on drainage will be a
function of the height of the water in the ditch.
The conditions in the first conclusion are met immediately
following an irrigation, since the drain spacings are
38
-------
considerably greater than six times the drain depths and
the depth of ponded water equals zero. This means that
for deep percolation to reach the drains it must first
travel to the cobble aquifer. The presence of the clay
layer in the profile retards this drainage and thus con-
tributes to developing high water tables.
The second conclusion indicates that during the winter when
the drainage ditches are empty, seepage is restricted
to the cobble aquifer and again the clay layer retards
the movement of water. This means that more groundwater
can be retained over the winter months, which aids plant
growth, but it also means that soil moisture storage
capacity is reduced and chances for high water tables
are increased.
For the case when the spacing is greater than six times
the drain depth, which is the case in the Grand Valley,
drainage depends on the height of the water in the ditch.
During the irrigation season, the depth of flow is usually
one to two feet so it will not be significant in improving
drainage.
If open ditch drains were spaced roughly 80 feet apart,
based on Kirkham's work, the drainage problem could be
solved. However, this would not be economical since most
of the cropland would be lost to open ditches. This
analysis indicates that reclamation of lands by leaching
in the study area must be accomplished by means of
drainage other than open drains. In this case, field
relief drainage is best suited to the problem of water
table control.
39
-------
SECTION VI
FIELD INVESTIGATIONS
Investigations were conducted during the summer of 1972
to gather data necessary for completing a drainage design
for the three farms in the study area and to evaluate the
applicability of the results of previous research for
use in the study.
Winger and Luthin (1966) as well as Christiansen and Grassi
(1969) have suggested a series of investigations necessary
to gather all pertinent data needed for a drainage design
investigations to be completed:
1. Topographic survey of fields to be drained;
2. Subsurface investigations to determine soil
properties and groundwater flow characteristics;
3. Investigate water table movement;
4. Determine sources of excess water;
5. Estimate leaching requirements;
6. Develop irrigation schedules; and
7. Compute groundwater balance.
TOPOGRAPHIC SURVEY
Topographic surveys are necessary for designing tile grade
line, computing areas to be drained, identifying tile
outlets, and as a base for measuring the slope and fluctua-
tions of the water table. The survey of the three fields to
be drained was performed by project personnel using a level
and 100-foot tape. Contours were drawn at one-foot ele-
vation intervals and all lateral distances were measured
with the tape. The results of the topographic surveys
are shown in Figures 11, 12, and 13.
The slope of the fields on the Kelleher and Canaday farms
averaged 0.56% in the north-south direction. Contours
in each field are uniformly spaced over the length of the
field and are parallel across the fields. Surface irri-
gation with relatively high efficiencies and even distri-
bution should be possible on these fields because of the
uniformity of the slope. In contrast to these fields,
40
-------
Open Ditch Drain
% D ROAD
| , 604"
4,5'
SCALE
j
4,9'
o so no
feet
zoo
Figure 11 . Topographic map of the Canaday field.
41
-------
618
4643
620'
WATER SURFACE ELEVATIONS
34'
Q
<
O
34'
"4630-2
"4630-3
SCALE
°4630-4
DRAIN
0 oo
fJP
200
Figure 12. Topographic map of the Kelleher field.
42
-------
£ D ROAD
30'
734'
34'
ID
00
0>
UJ
UJ
111
(O
o:
(O
o
00
480
SCALE
so
100
feet
zoo
Figure 13. Topographic map of the Wareham field.
-------
the Wareham field has a very irregular shape which makes
efficient irrigation very difficult. The large variation in
slope along the length of an irrigation furrow makes it
difficult to select the stream size which will be most
efficient in terms of water distribution along the length
of the furrow.
SUBSURFACE INVESTIGATIONS
The subsurface investigations were conducted to determine
soil groups, their location and continuity, salt-affected
soils, and areas of high water table. Soil moisture
characteristics, field capacity, wilting percentage,
available moisture and capillary distribution, as well as
the hydraulic conductivity, were also determined during
this phase of the study.
Salt levels in the soils of the three study farms were
determined by project personnel at the beginning, in the
middle, and at the end of the growing season. Soil samples
were taken at one-foot intervals to a depth of four feet at
nine stations on each study farm. The samples were then
composited by one-foot intervals for the three stations at
the head, middle, and bottom of the field and taken to the
project laboratory in Grand Junction for chemical analyses.
Electrical conductivities were measured on the soil
moisture extracts and are tabulated in Tables 3,4, and 5.
In addition, the ionic constituents for selected samples
were determined and are presented by Ayars (1972). As
a means of visual interpretation of these results, the
average electrical conductivities for each sampling period
are plotted in Figure 14. These plots show the movement
and accumulation of salts within the soil profile throughout
the growing season.
Generally, salt concentrations tend to increase towards
the lower end of a field since a greater application of
irrigation water is made at the top of the field. The
data in Tables 3,4, and 5 do not confirm this hypothesis,
indicating the local effects of relatively flat land
slopes, soils of low permeability, and irregular field
topography.
The average electrical conductivities shown in Figure 14 /
give some indication of the quality of the land, as well
as water management on each of these fields. On the Canaday
field, the salts in the upper two feet of soil increase
dramatically over the growing season. This indicates
insufficient water was supplied in the summer to adequately
leach the soil. The levels of salt are still acceptable
44
-------
Table 3. ELECTRICAL CONDUCTIVITY VALUES FOR SOILS ON THE
CANADAY FIELD.
Electrical Conductivity of Composite Samples
By Field Location (ymhos/cm).
Date of
Sampling
6/23/72
7/26/72
10/ 5/72
Depth of
Sample
(feet)
0-1
1-2
2-3
3-4
0-1
1-2
2-3
3-4
0-1
1-2
2-3
3-4
North
End
1635
6647
4220
4590
1444
4540
4275
4650
6280
5787
5036
4540
Location
Middle
2005
2638
4861
5899
2167
2112
5072
5684
4885
7495
6397
7337
South
End
1741
1159
1504
4115
1648
1135
4731
6077
2425
2005
5994
5945
Average
1794
3481
4745
4868
1753
2596
4693
5470
4530
5095
5809
5941
45
-------
Table 4. ELECTRICAL CONDUCTIVITY VALUES FOR SOILS ON THE
KELLEHER FIELD.
Electrical Conductivity of Composite Samples
By Field Location (ymhos/cm).
Date of
Sampling
6/28/72
7/24/72
10/ 5/72
Depth of
Sample
(feet)
0-1
1-2
2-3
3-4
0-1
1-2
2-3
3-4
0-1
1-2
2-3
3-4
North
End
1782
1175
1120
6959
2884
1602
3817
3726
2090
1072
4723
6178
Location
Middle
1635
1226
1073
7164
1498
1139
954
3090
2315
1229
1194
966
South
End
1637
1637
7164
6571
2218
1346
5365
3405
3043
1259
7402
7184
Average
1685
1346
3119
6898
2200
1362
3379
3407
2483
1187
4440
4776
46
-------
Table 5. ELECTRICAL CONDUCTIVITY VALUES FOR SOILS ON THE
WAREHAM FIELD.
Electrical Conductivity of Composite Samples
By Field Location (ymhos/cm).
Date of
Sampling
7/ 6/72
8/11/72
10/ 5/72
Depth of
Sample
(feet)
0-1
1-2
2-3
3-4
0-1
1-2
2-3
3-4
0-1
1-2
2-3
3-4
West
Side
1595
3769
6158
4884
3869
7004
4865
4495
Location
Middle
5195
13379
15266
15927
7878
13456
15316
16793
East
Side
3079
11166
11680
12741
4354
11197
11386
12835
Average
3289
9438
11035
11184
5367
10552
10522
11374
No Data
47
-------
0
1
2
3
4
CANADAY FIELD Sampling Dote
^
X
M
^
""
\
\
^^
1
\
>
\l
1
6/23/72
0 7/26/72
Q 10/5/72
0 1-0 2-0 3-0 4-0 5-0 frO 7-0 BO 9-0 10-0 11-0 12-0
KELLEHER FIELD
Sampling Data
o
1 1
O
1 2
JQ
e
o
CO
- 4
L
<
Gj£>
^
ia-i
A,
\
~- -
-^«
6/28/72
0 7/24/72
B 10/5/72
o 0 1-0 2-0 3-0 4-0 5-0 6-0 7-0 8-0 9-O 10-0 11-0 12-0
to
WAREHAM FIELD
Sampling Date
1-0 2-0 3-0 4-0 5-0 6-0 7-0 8-0 9-0 10-0 11-0 12-0
Electrical Conductivity * I03 //mhos
Figure 14. Relationship of the average soil electrical
conductivity to depth in the soil profile on
the study fields for 1972.
48
-------
in that they_will not restrict plant growth at the present
time, but this field should be carefully managed to prevent
further buildup of salts.
The soil on the Kelleher field is relatively free of
salts and was maintained that way throughout the 1972 growing
season. The first irrigation was quite effective in
leaching the salts from the four-foot depth of the root zone.
After the first irrigation, there was some increase in
salts, but these can easily be leached and will not be a
problem for future productivity of the field.
The soil on the Wareham farm is already high in salts
below a depth of one foot. Figure 14 shows that the
salts increased during the summer, indicating insufficient
water being applied for leaching. Consequently, this
field requires a more salt-tolerant crop and more careful
application of irrigation water.
Mechanical analysis to determine soil texture, as well
as pressure plate tests to estimate soil moisture values
at saturation, field capacity and wilting point, for the
soils in the study fields were conducted in the Soils
Laboratory at Colorado State University. The results of
these laboratory analyses are presented in Table 6. The
soils were generally clays and silty clays containing
very little sand. The total available water (the water
available to plants for growth) was computed to be 2.4
inches per foot of soil based on the soil moisture and
soil moisture tension data between 1/3 and 15 bars given
in Table 6.
Hydraulic conductivity was estimated using the single-
auger-hole method discussed by Luthin (1966). This
method was considered the most practical technique
because of the simplicity of data collection and the ease
of computation. The auger-hole method has the additional
advantages of using soil water for the measurement, using
a large sample, and reflecting the horizontal component
of conductivity.
The method used for determining hydraulic conductivities
from auger-hole data in which an impermeable boundary is
at a great depth is shown in Figure 15 (Maasland and
Haskew, 1957). The assumptions used in this development
are:
1. The water table is not lowered in the region
around the auger hole when the hole is pumped at
the beginning of the test;
49
-------
6 TEXTURAL CLASSIFICATION AND MOISTURE HOLDING CAPACITY OF THE SOILS ON THE STUDY
FIELDS>
in
o
Farm
Canaday
Wareham
Kelleher
*Duplicate
Sampling
Location in
Field
SE Corner
SW Corner
Top
NE Corner
SE Corner
Top
Top
SE Corner
SW Corner
Values
Percent Moisture by Weight for
Given Pressures
Sand Silt
Clay
(%) (%) (%) Texture
3 56
9 47
9* 48*
15 41
50
48*
39
39*
46
44*
57
56*
57
54*
54
41
44
43*
44
50
52*
61
61*
54
56*
43
44*
43
46*
46
Texture Codes - SiCL
SiC
C
CL
L
SiC
SiC
SiC*
SiC
C
C*
C
C*
C
C*
C
C*
C
C*
C
: Silty
: Silty
: Clay
: Clay
: Loam
0
Bar
40.0
43.4
42.2
52.5
49.4
45.8
44.4
45.1
44.0
Clay
Clay
Loam
1/3
Bar
26.
27.
24.
29.
30.
28.
25.
26.
30.
Loam
8
6
4
5
6
8
5
0
0
1
Bar
18.
18.
16.
21.
23.
21.
18.
18.
19.
4
8
8
3
1
2
5
9
7
10
Bar
12.7
14.0
12.9
16.6
18.0
16.3
14.0
13.8
14.2
15
Bar
13.3
13.2
13.2
15.1
17.3
15.4
13.4
13.4
13.4
-------
2a
Soil Surface
Ay in At
Figure 15.
Geometry of single-auger-hole method used in
homogeneous soil (Ayars, 1972).
51
-------
2. Flow into the auger hole is assumed to be lateral;
and
3. Recovery measurements should be limited to one-
fourth of the depth of the water removed.
Ernst derived an empirical equation for the case shown in
Figure 15 based on a numerical analysis of the exact solution
(Maasland and Haskew, 1957). Ernst's empirical equation is:
K = 4000 _ fal [Ayl (8)
(20 + d/a) (2 - y/d) ~ yH At
where K = hydraulic conductivity, inches/hour
Ay = rise of water surface in the auger hole during
the time interval At, feet,
d = depth of auger hole below the water table, feet,
y = distance from static water table to elevation of
water in the auger hole, feet
a = radius of auger hole, feet
s = distance from the bottom of the auger hole to
the impermeable boundary, feet.
The values of hydraulic conductivity have an accuracy of
+20 percent if the following conditions relating the size
of the auger hole and the position of the water table (with
lengths in centimeters) are met:
3 0.2, s > d
where the parameters are as given in Figure 15.
Data used in calculating hydraulic conductivities including
depth of hole, depth to water surface at equilibrium, and
rate of rise of water in the auger hole after the water
had been pumped down to a new elevation were collected
by project personnel. The collected data were recorded
and hydraulic conductivities computed on a form used by
the United States Buraeu of Reclamation (USER).
Once the data were transferred to the USSR form, the com-
putations were straightforward. The data for the recovery
rate are plotted as shown on Figure 16 from which the
value for the total depth of drawdown (y ) is estimated.
Then, a value for 0.8y is calculated ana plotted on the
graph. The values for°y and 0.8y are then averaged to
give a mean y. After computing the ratios of mean depth
to water table divided by the radius of auger hole and
initial depth of water table divided by the radius of auger
hole, the solution diagram of Maasland and Haskew (1957)
which employs these ratios can be used. The solution diagram
selected for use depends on whether the auger hole terminates
52-
-------
in
it)
2-1
2-3
2-5
I
I
2-7
2-9
3-1
= 3-13
8
12
0-8y=2-50
28
40
16 20 24
TIME-SECONDS
Figure 3.6. Example plot of the recovery data for a single auger hole hydraulic conductivity
test.
-------
on the impermeable boundary or the distance from the
bottom of the auger hole to the barrier is infinite.
Once the coefficient is taken from the solution diagrams,
it is used with the increments of time and depth computed
for the water table movement from y to 0.8y in order
to compute the hydraulic conductivity. °
Initially, hydraulic conductivities were computed based on
the assumption of the impermeable layer being at an infinite
depth below the end of the auger hole. However, after con-
sidering the stratification of the soil, and the existence
of a tight clay layer at a depth of six to ten feet below
the surface, the conductivities were recomputed assuming
the auger hole terminated on the impermeable boundary. Tests
run in this clay layer showed conductivities of less than
0.043 inches per hour.
The values for all the tests run on the three fields, along
with other fields in the study area, are summarized in
Table 7. In each instance where the values of hydraulic
conductivity have been recomputed, the auger hole terminated
on or very near to the clay layer.
The values for the hydraulic conductivities were very
low in the silty clay soils. A textural analysis of the
soils indicated they were quite dense and had very little
aggregated structure. With these conditions and considering
the soil type, conductivities of less than one to two
feet per day can be expected. In contrast to the silty clay
soils, tests run on river sands and sandy loams produced
conductivity values of 53 feet per day and 13 feet per
day, respectively. Some problems were encountered in
measuring hydraulic conductivity because of the lack of a
high water table.
WATER TABLE INVESTIGATIONS
The water table investigations were conducted to determine
the slope and fluctuation in elevation of the water table,
along with establishing areas of high water table over the
growing season. From these data, estimates were made of
the natural groundwater flow, along with identifying
sources of excess water at the grid point. Access tubes
were installed in each field where soil moisture and
salinity samples were taken and read weekly during the
growing season. The data collected for 1972 show that a
high water table did not exist during the growing season,
although data collected by Skogerboe and Walker (1972b)
indicated water table problems in earlier years in the
54
-------
Table 7-
HYDRAULIC CONDUCTIVITY DATA FOR SOME FIELDS IN
THE GRAND VALLEY SALINITY CONTROL DEMONSTRATION
PROJECT.
Test
No. Farm
1
2
3
4
5
6
7
8
9
10
11
12
Bulla
Kelleher
Canaday
Martin
No test
Kelleher
Wareham
Kelleher
Canaday
Canaday
Bulla
Wareham
1
2
1
2
1
2
1A
2A
IB
2B
1
2
1
2
1
2
1
1
2
1
2
Hydraulic
Depth of Conductivity
Test (ft) S=°° S=0
27 98 1-70
0.98
29 8 ^ °-76
2'9 " 8'3 0.49
53.30
6-° ~ 9'8 45.80
8.5 -11.3 1.33
" - 8-7 oil
*»-"! o!"
64 92 °-36
6-4 " 9-2 0.33
9 0 -11 9 1'57
y.u 11. y 1>49
, o ,, o 0.068
5.8 -11.0 0>0?4
6.9 -11.0 0.038
0.46
0.46
7 3 -10 7 13-8
7.J 1U./ 14^g
1.89
1.10
0.85
0.68
N/S
N/A
1.50
0.67
0.53
0.30
0.37
0.60
0.55
1.89
1.71
0.086
0.084
0.046
0.55
0.57
N/A
N/A
Soil Type at
Test Depth
Lt. bn silty clay
loam, moderately
dense & compact
Lt. bn gray heavy
silty clay, massive
River sand-gravel
Massive It. bn
gray silty clay
loam
Lt. bn gray silty
clay dense, mas-
sive
Heavy silty clay
dense, massive
No data
Med gray silty
clay dense mas-
sive to gray bn
heavy loam
Lt. bn gray silty
clay loam, dense
to Bn gray silty
clay loam dense &
compact, massive
Brown gray silty
clay massive,
dense , compact
Brown-gray heavy
loam, silty clay
loam massive mod-
erately compact
Brown loam to
reddish brown
fine sandy loam
55
-------
locality of those farms. A definite answer cannot be readily
given to explain the low water table during this year. Much
lower groundwater levels were also found on other farms
being studied in this area on which measurements have been
made for three years. It is believed that the low
winter moisture for the past year, which was the lowest
precipitation measured during 82 years of record, effectively
reduced the soil permeability due to a lack of mechanical
structuring of the soil as it alternately freezes and thaws.
Therefore, less water moved into the soil both during the
winter because of low precipitation and during summer
because of reduced soil permeability. Thus, water tables
were generally lower during the 1972 irrigation season.
SOURCES OF EXCESS WATER
An important aspect of drainage studies and subsequent
tile drainage designs is evaluating the sources of the
water causing the waterlogging conditions. In most instan-
ces, deep percolation from irrigation or precipitation,
seepage from canals, movement of water from adjacent
areas, and artesian water are the major sources of excess
water. Data collected during the water table investi-
gations indicate that each of these possibilities exist
in the test area.
The net irrigation on the field (infiltration into the
soil root zone) was calculated from inflow-outflow data
collected by continuous stage recorders mounted on flumes
installed in the head and tailwater ditches of each field.
Deep percolation from irrigation was determined by measuring
the net inflow to the field and subtracting the estimated
consumptive use for the plants and the change in root
zone soil moisture.
Data on the slope of the water table, the height of
the water in a field and the thickness of the aquifer,
which were taken in previous investigations, can be used
to estimate the natural groundwater flow and its source.
The slope of the water table and area of the flow section
are the data needed to compute the volume of groundwater
flow using Darcy's law, as given in the following form:
Q = K D L i (9)
where Q = total flow, cfs,
K = hydraulic conductivity, feet/sec,
D = permeable depth, feet,
L = width of flow boundary, feet
i = slope of water table.
56
-------
The groundwater contribution to the drainage system from
adjacent areas can also be estimated using this equation.
The volume of water from artesian sources is dependent on
the hydraulic head in the aquifer and the thickness and
hydraulic conductivity of the overlying materials. Piezo-
meters extending to various depths in the soil profile,
as well as the cobble aquifer, were used to determine the
general gradients in the study area. Data reported by
Skogerboe and Walker (1972b) show the average vertical
gradients to be downward in the study area. It was the
experience of the investigators that when the cobble
aquifer was penetrated by an auger hole, water would
immediately be present, but its elevation was less than
the equilibrium elevation in the hole, thus also indicating
a downward vertical gradient towards the aquifer.
Of the sources discussed, only deep percolation from irri-
gation is considered significant in this study. Seepage
from canals has been eliminated because none of the fields
are bounded by a canal. Since the area is semi-arid,
with the majority of rains occurring in the summer being
less than 0.1 of an inch, deep percolation from precipi-
tation is not significant. The existence of downward
gradients to the aquifer and the relative impermeability
of the clay layer over the aquifer eliminate the artesian
source from further consideration.
Groundwater flow into the fields is difficult to estimate.
However, two of the fields in the study are bounded on
two sides by 12-foot deep drainage ditches, one being
bounded on the north and east and the other on the east and
south. The third field has a 12-foot ditch at its south
end. It is assumed, therefore, that groundwater flow from
adjacent areas into the three fields is not significant
because the ditches act as barriers to flow through the
field.
LEACHING REQUIREMENT
For irrigated agriculture in arid and semi-arid areas,
the maintenance of a salt balance in the root zone is
essential for continued productivity. To achieve this
balance, water in excess of the consumptive needs of the
crop must pass through the root zone. The United States
Salinity Laboratory has defined the leaching requirement
as the fraction of irrigation water which must be used to
control salinity, and which can be mathematically expressed
as (U.S. Department of Agriculture, 1954);
(10)
57
-------
where D = depth of water, inches,
D, = depth of drainage water, inches,
D. = depth of irrigation water, inches,
IVr
EC = electrical conductivity in ymhos/cm,
LR = leaching requirement expressed as a fraction
Alternately, the depths of drainage can be expressed as
a function of the consumptive use requirement of the plant,
D :
cw
EC.
Ddw * E* ^ CW {11)
The leaching requirement concept assumes a long-term aver-
age of salt concentration levels, a uniform water applica-
tion, no precipitation of soluble salts in the soil, and
no salt uptake by the crop.
IRRIGATION SCHEDULES
Irrigation schedules are required for each crop grown
on a field in order to estimate the deep percolation from
irrigation of each crop, along with determining which crop
will be the limiting case. The elements required to con-
struct a schedule include the length of the irrigation sea-
son, effective rainfall, snowmelt, total readily available
water, and estimates of the daily consumptive use.
The first elements are easily obtained since the irrigation
season is fixed by the irrigation company and climatological
data from the U.S. Weather Bureau is available to estimate
the effective depths of snow and rain.
Estimating consumptive use requires selecting an evapo-
transpiration equation which is suitable for use in the
area and is compatible with available data. The
Blaney-Criddle formula, as modified by the Soil Conserva-
tion Service, and the Jensen-Haise formula were compared
on estimated total consumptive use and daily consumptive
use in relation to consumptive use values computed by
the U.S. Bureau of Reclamation's irrigation scheduling pro-
gram in the Grand Valley. Although the Jensen-Haise
method estimated consumptive use values somewhat higher
than the other two, it was selected because it would pro-
vide a factor of safety in the drainage design (which is
true when farm deliveries are properly managed, such as
by irrigation scheduling).
58
-------
The Jensen-Haise equations are
Eta = CT(T * Tx)Rs
CT -
C - 50 mb
C -
H (e2 - ex) ..............
C2 = 13°F ................. (is)
Cl = 68°F - (3.6°F elev/1000) ........ (16)
TX = 27.5°F - 0.25 (e2 - e^ °F/mb - (elev/1000) (17)
where e^ = saturation vapor pressure of the mean maximum
temperature for the warmest month, millibars,
T = mean monthly temperature, °F,
R = average daily solar radiation, langleys,
o
E = evapotranspiration of well-watered alfalfa,
langleys (langleys x 0.000673 = inches).
Once the constants for the area have been established, use
of the equation requires only the mean daily temperature,
the average daily solar radiation for the month, ana
a crop coefficient which gives the actual plant consumptive
use as a function of the plant growth stage.
The data and the method used in computing an irrigation
schedule for corn are shown in Table 8 . The allowable
depletion was computed based on a four-foot root zone and
a 50-percent depletion of the totally available water.
The crop coefficients were given as a function of the
percentage of the growth until full crop cover. In this
case, the interval used to change coefficients was eight
days.
The date of irrigation will be specified as the date when
the readily available water in the soil has been depleted
as computed by summing the daily consumptive use values.
The daily use value is equal to the monthly estimated
evapotranspiration (which has the units of inches per day)
multiplied by the crop coefficient.
Once the dates for the irrigation have been established
they are combined with natural recharge events to provide
the recharge event schedule needed for the spacing compu-
tation, as shown in Table 9. The proposed irrigation
schedules used in this study are given by Ayars (1972) ,
59
-------
Table 8. EXAMPLE CALCULATION OF IRRIGATION SCHEDULE FOR
CORN USING THE JENSEN-HAISE METHOD.
Inter-
val
Et
P
(in/day)
Crop Co- Daily use Depletion Date of
efficient (in/day) in Inter- Irrigation
yal (inches)
April
15
May
15-23 .276 0.20
24-31 0.23
June
1 .372 0.23
2-10 0.29
11-19 0.38
20-28 0.49
29-30 0.61
July
1-6 .402 0.61
7-15 0.72
16-19 0.82
19-23
24-31 0.91
August
1-2 .342 0,96
2-8
9-18 0.99
19-28 0.99
29-30 0.93
September
1-4 .256 0.93
4-8
8-18 0.82
,0552
,0635
.1080
.1820
.2270
.2450
.2890
.3290
.3660
.3280
.3280
.3380
.3380
.3380
.2380
,2100
0.44
0.44
0.09
0.86
1.13
1.46
0.45
1.47
2.32
1.31
1.31
2.92
0.65
1.97
3.38
3.38
0.68
0.95
0.95
2.10
28.25
April 15
June 30
July 19
August 2
August 18
September 4
Assumptions:
1. allowable soil moisture depletion =4.9 inches
2. preirrigated to fill root zone on April 15
3. crop planted May 15
4. 85 days to full crop coverage of soil surface
60
-------
Table 9. EXAMPLE OF PROPOSED YEARLY RECHARGE SCHEDULE
USED FOR DRAIN SPACING BASED ON AN IRRIGATION
SCHEDULE FOR CORN.
Recharge
Source
I
B
I
I
I
I
I
I
B
Date of
Recharge
Sept 4
Dec 25
April 15
June 3 0
July 19
Aug 2
Aug 18
Sept 4
Dec 25
Interval
Between
Recharge
(Day)
112
111
76
19
15
16
17
112
Depth of
Irrigation
(inches)
0
0
4.9
4.9
4.9
4.9
4.9
4.9
I = Irrigation
B = Between Irrigations
61
-------
GROUNDWATER BALANCE
Data from each of the previous investigations are compiled
at this point in the form of an equation to estimate the
volume of groundwater to be removed by natural or arti-
ficial drainage methods to achieve dynamic equilibrium.
Christiansen and Grassi (1969) give the following mass
balance equation for determining drainage requirements:
IR + CS + P + GW. + GW - ET - ET - GW, - DR = + AGWS (18)
10 a c n a
where IR =
CS =
P =
GW. =
10
GW =
a
ET =
c
GW , =
. a
DR =
AGWS =
contribution to the groundwater from water
applied by irrigation, acre-feet
canal seepage losses reaching the groundwater,
acre-feet;
precipitation reaching groundwater, acre-feet?
net groundwater inflow directly from, or out-
flow to the adjacent area, where a plus sign
indicates a groundwater accretion, acre-feet;
groundwater inflow from artesian aquifers,
acre-feet
the evapotranspiration by agricultural crops
from groundwater, acre-feet
downward drainage to pumped aquifers, acre-feet;
outflow from the drainage system, acre-feet;
change in groundwater storage where a plus
sign indicates groundwater accretion and a rise
in the water table, acre-feet.
When the system has achieved dynamic equilibrium for a
season, AGWS =0. In this application of drainage technol-
ogy to field drainage in the Grand Valley, Equation 18
reduces to:
IR - ET = AGWS (19)
C
62
-------
SECTION VII
DESIGN, CONSTRUCTION AND EVALUATION OF FARM DRAINAGE
GENERAL DESIGN FACTORS
The investigations reported in the previous section indi-
cated that the primary parameters in field drainage design
in the Grand Valley are deep percolation, evapotranspira-
tion by crops, and groundwater storage changes. Deep perco-
lation depends on many factors describing the condition of
the soil, uptake rate by the crops, and irrigation practices,
The relationships between the water and salt flows within
the confines of a farm (inflows, precipitation, field
tailwater, deep percolation, evapotranspiration, soil
moisture storage changes, etc.) have been traditionally
described by an efficiency value. For example, irrigation,
farm, field, application, and water use efficiencies are
commonly used, but often not consistantly. Even in the
exhaustive treatment of the various measures of irrigation
efficiency given by the American Society of Agronomy
in its Monograph No. 11, there are discrepancies among
the contributing authors. A worthwhile statement is
made in Chapter 61, p. 1120, pointing out the disparity
in use of such terms and noting that no standards have
been accepted (Hagen, Haise, and Edminster, 1967).
In the evaluation of on-farm improvements designed as
salinity control measures, an absolute necessity exists for
delineating the effects of field tailwater and deep perco-
lation. On page 776 of the Agronomy Monograph No. 11,
irrigation, farm and field efficiencies are distinctive
depending on the point of measurement in the irrigation
system. The work reported in this writing and similar
work by Skogerboe and Walker (1972a) and Skogerboe, Walker,
Taylor, and Bennett (1974) has encompassed only the farm
boundaries. The measure of irrigation efficiency there-
fore selected and denoted "farm efficiency" evaluated
the percent of water supplied to the farm or farms which
was consumptively used by the crops. It should be noted
that inefficiencies result when insufficient water is not
made available to the plants because of field tailwater or
deep percolation. To delineate the effects of deep perco-
lation, a measure defined as "application efficiency"
which is congruent with uses in the Agronomy Monograph No.
11 on pages 877, 878, 894, 1121, and 1122 was used. Appli-
cation efficiency thus defined is the percentage of water
applied to the soil which is consumptively used by the
crops. In this case, inefficiency results only from deep
percolation losses (Hagen, Haise, and Edminster, 1967).
63
-------
A series of curves using the irrigation schedule for each
of the major field crops grown in Grand Valley was developed,
which related the leaching requirement to the drain spacings
for the physical conditions found in each study field. An
analysis to determine whether the maximum spacing could be
achieved in these fields by designing the drains above the
barrier or on the barrier indicated that the drains
designed on the barrier will have the maximum spacing.
Consequently, the curves of drain spacings versus leaching
requirement were developed for drains placed on the
barrier. The values for hydraulic conductivity and
depth to barrier for each field used in the analysis were
determined based on experience in the field, coupled
with the data presented in Tables 9 (example) and 10. The
values for the specific yield were taken from Dumm (1967).
These spacing design curves are presented as Figures 17, 18,
and 19.
SELECTION OF CONSTRUCTION SITES
In evaluating the irrigation and drainage needs on each of
the three farms, it became apparent that the only field
needing drainage was the Wareham farm (Ayars, 1972).
Both the Kelleher farm and the Canaday farms were rela-
tively well managed and could thus prevent high water
tables by increasing the efficiency of early irrigations.
Since the drainage investigation results for these two
latter fields are reported by Ayars (1972) , the results
relevant to the Wareham field will be emphasized herein.
Field Description
The Wareham field contained 11.6 acres of alfalfa and weeds
being used as a pasture. The field was pastured continuously
even during irrigation, resulting in the soil surface
being highly compacted. The soils are silty clays,
silty clay loams, and clays, which are generally dense and
massive, having very poor structure and low values for
hydraulic conductivities. The salt content is very high
with the electrical conductivity averaging over 9 mmhos/cm
through the soil profile. Figure 14 shows that the salt
content increases over the growing season, implying that
the irrigation water was ineffective in leaching the soil.
Water management on this field was extremely poor during
the study period as shown by the efficiency data in Table
11. The presence of livestock during irrigation periods
contributed to this efficiency by destroying the furrows
used for irrigation.
64
-------
Table 10. TEXTURAL ANALYSIS OF THE SOIL PROFILES OF THE AUGER HOLES USED FOR HYDRAULIC
CONDUCTIVITY TESTS ON THE STUDY FIELD
Location
in Field
1 -
2 -
3 -
4 -
5 -
6 -
7 -
8 -
9 -
10 -
11 -
12 -
South end
of Field
Light
Gray
silty
clay
massive
dense
compact
Brown
Sandy
Loam
NW
Corner
Silty
Clay Loam
Loam
Silty
Clay
Loam
Loam to
Silt
Loam
Brn Gr
Si Clay
Loam
SiltLoam
massive
Silty
Clay
Loam
dense
compact
Center
Silty
Clay
Loam
Silt
Loam
Silty
Clay
Loam
Silty
Clay
SE
Corner
Light
Gray
heavy
Si Cl
Loam,
massive,
dense
Light
Brown
<3r Silt
Clay
Loam
Massive,
Unstable
When
Saturated
NE
Corner
Lt Gr Brn
Sicl Loam
Mod Gran-
ular
Light Brn
Gray, Si
Clay Loam
moderate-
ly dense
massive
Medium
Gray It.
silty cl
dense,
massive,
sticky
Brown to
Gray Brn
heavy
loam
massive
SW
Side
Lt Gr
Brn Silt
Loam to
Silt Cl
Loam
Brown
Gray
Light
Silty
Clay
moder-
ately
compact
massive
Brn Gr
heavy Si
Cl dense
massive
SW
Corner
Gr Brn Si
Cl Loam
Gr SiClLoait
Granular
Lt Gr Silt
Clay moder-
massive
Brn loam
to light
clay
loam
Lt brn
loamy sand
unstable
Brn fine
sand loam
North
Center
Silty Clay
Silty Clay
Loam
Silty
Clay
Silty Clay
Loam
Brown fine
sandy loam
-------
Hydraulic conductivity = 0.76 ft/dc
Depth to drains = 7
Depth to barrier = 7
ft
ft
Barley
Alfalfa
Pasture
Corn
Sugar Beets
CTl
100
SPACING (feet)
ISO
zoo
o
r
o
m
n
n
70 o
m
z
o
80 p
90
100
Figure 17. Relation between leaching requirement and drain spacing for the Canaday field,
-------
Hydraulic Conductivity = 0.76 ft/day
Depth to Barrier = 8 ft
Depth to Drains = 8 ft
Barley
Alfalfa
Pasture
Corn
Sugar Beets
too
200
SPACING (feet)
300
Figure 18. Relation between leaching requirement and drain spacing for the Kelleher field.
-------
Hydraulic Conductivity =0.57 ft/day
Depth to Drain = 6 ft
CO
LEACHING REQUIREMENT
_ .
==s=5=
uepuu
.
"=»--*
U(J D
^^
etJLi J_e
A
0
X
a
^x=
i- D 1C
- Barley
- Alfalfa
- Pasture
- Corn
- Sugar Beets
-©-
APPLICATION EFFICIENCY (%)
o o o o
f- 00 O O
50
SPACING (feet)
100
Figure 19. Relation between leaching requirement and drain spacing for the Wareham field,
-------
Table 11. RESULTS OF IRRIGATION EFFICIENCY TESTS DURING THE 1972 IRRIGATION SEASON ON
WAREHAM FIELD.
10
Irri-
gation
Period
6/12-6/28
8/ 3-8/10
Field
Inflow
(inches)
9.12
14.76
Field
Outflow
(inches)
4.56
5.13
Net
Appli-
cation
(inches)
4.56
9.63
Soil
Moisture
Storage
Change
(inches)
0
+3.68
Crop
Use
(inches)
1.09
1.93
Perco-
lation
from the
root zone
(inches)
3.47
4.02
Appli-
cation
Effi-
ciency
(%)
24.0
58.3
Irri-
gation
Effi-
2
ciency
(%)
11.9
38.0
1. Application Efficiency =
2. Irrigation Efficiency =
Crop use + soil moisture storage change
Net Application
Crop use + soil moisture storage change
Total Inflow
x 100
x 100
Note: The water was turned on September 15, 1972 and allowed to run at will until
October 30, 1972, which made it impossible to calculate water use efficiencies
for this irrigation.
-------
Drainage Design
The hydraulic conductivity on the Wareham farm used for
design purposes was estimated to be 0.57 feet per day with
the minimum depth to the clay barrier material being 6.0
feet. The leaching requirement was set at 8 mmhos/cm,
the minimum permissible requirement needed to maintain the
electrical conductivity of the soil in this field. Since
the irrigation water has a typical value of abou 0.8 mmhos/cm,
the leaching requirement is determined to be 10%. Based
on these criteria, and using Figure 19, the drain spacing
was estimated at about 40 feet (Ayars, 1972).
DRAINAGE SYSTEM CONSTRUCTION
The topographic map, Figure 13, indicated the direction of
field slope and the direction the laterals and collector
drains would be laid. Hence, the laterals were installed
in the east-west direction and the collector drain in the
north-south direction making an exit into the open drain
in the southeast corner of the field as shown in Figure
20. The total length of pipe installed was approximately
11,500 feet.
During the early part of 1973, the pipe sizes were deter-
mined and ordered. The lateral lines were 4-inch diameter
perforated plastic and the collector drain was 6-inch per-
forated plastic pipe. The pipe was a spiral design which
allowed the pipes to be screwed together using special
couplers.
Construction Activities
Construction began on May 14, 1973, with the Grand Junction
Drainage District supplying labor, a track driven backhoe
with a 30-inch bucket to make the excavation, a caterpillar
tractor to cover the open trench, and a front-end loader
to place the gravel used for the filter around the pipe.
The drain installation began by clearing strips of ground
20 feet wide on 40-foot centers in the field where grade
lines and surface profiles were determined. The minimum
grade on the lateral lines was 0.5%, while that of the collec-
tor drain was 0.4%.
The construction began by the excavation of the collector
line starting .at the drain outlet and proceeding into the
field for a distance of 40 feet and then north along the
east edge of the field stopping 40 feet from the north
70
-------
edge of the field. As this trench was to be left open for
a period of time, it was benched to prevent any caving
that may ordinarily occur. Stakes were driven on grade
every 40 feet in the bottom of the trench and gravel placed
to the top of the stakes. The 6-inch collector drain was
then installed with a tee on 40-foot centers for the connection
of the lateral lines.
After the collector trench was excavated and the pipe laid,
work began on the lateral lines. The lines were excavated
beginning at the collector trench and moving west. As the
excavation of the individual lines proceeded, away from
the collector trench some distance, the 4-inch perforated
plastic pipe was connected to the collector pipe and laid
in the lateral trench. The gravel was then poured into the
trench using the front end loader with the fine grading
accomplished by men working in the trench. After the
gravel was placed, the pipe was lifted slightly to allow
some gravel to go under the pipe to provide some permeable
material on which the pipe could rest. A plastic sheet 4
inches wide was placed on top of the pipe to insure that no
fine material would enter the pipe from the area above.
A typical cross-sectional view of the pipe, gravel, and
plastic installation is shown in Figure 21. As soon as the
plastic had been lain over the lateral pipe, gravel was
then placed around the next 40 feet of collector drain
between laterals and the plastic cover placed over the
6-inch collector line. Then both the lateral trench and
the 40-foot section of collector trench were closed by
the bulldozer.
The average amount of trench that could be excavated and
pipe placed was about 1200 feet a day. The construction
was completed on June 1 and all equipment was removed.
Post-construction Activities
After the drainage system had been installed, a tractor
with a ripper implement was used to loosen the top 12 to
24 inches soil compacted by the construction. In addition,
the construction had left mounds of unsettled earth
overlying each trench which were consolidated by
placing a furrow over the top of each trench and diverting
water from the irrigation head ditch. The collector drain
trench was difficult to settle because of the width with
which it had been excavated and the difficulty in getting
water into the furrow over the drain. Even with the prob-
lems of getting water to this trench, settlement was
observed to have taken place along most of its length.
71
-------
-------
Figure 21. View of pipe installation,
73
-------
Following the settling of the drain trenches, the field was
planted to Jose Tall Wheatgrass with a cover crop of oats.
While the grass is not a major cash crop, it is one of
the most salt-tolerant and thus well suited to the Wareham
field. In a few years this field should be reclaimed
sufficiently to allow a higher cash value crop to be grown.
EVALUATION OF FIELD DRAINAGE
By the time planting of the Jose Tall Wheatgrass on the
Wareham farm was completed, only two irrigations were
required to sustain the crop through the remainder of the
season. Data collected from these two irrigations, along
with water quality samples taken from field water tables
during the study, provided the information from which field
drainage was evaluated as a salinity control measure.
Wareham Field Data
Several factors inherent in the field drainage on the
Wareham farm require mention before the data are presented
and analyzed. The upper soils on the farm were shown by
soil salt analyses to be severely affected by poor water
management in recent years. It was expected that the drain-
age effluents during initial tests would be laden with
salts leached from the soil reservoir. As subsequent irri-
gations are made, the quality of the drain effluent will
be expected to improve significantly, allowing the invest-
ment in the system to yield improved salinity control.
In another regard, it is almost certain that flows
passing into the drainage system will come from the soil
overlying the lines rather than any significant lateral
movements. The field was badly compacted during previous
years and during the drain installations. It is thus
obvious that several years of careful land and water use
will be necessary to improve the effectiveness of the drain-
age system. These factors lead to the conclusion that
the real effectiveness of drainage should be determined
over a much longer period. In fact, this same field will
continue to be monitored during the 1974, 1975, and 1976
irrigation seasons as a part of the demonstration project
"Implementation of Agricultural Salinity Control Technology
in Grand Valley," which is being funded by EPA. However,
because considerable data has been collected from this and
other studies, significant observations can be made regarding
local drainage.
74
-------
During the irrigations on the Wareham farm, a careful pro-
gram of water and salt budgeting was undertaken. This
program, which was developed and utilized in several pre-
vious studies, also included measurements of a portion of
the water percolating below the root zone when intercepted
by the drain lines. The budgeting procedure incorporates
inflow-outflow measurements with soil moisture readings
and evapotranspiration estimates to delineate the indi-
vidual flows. Generally, these data are presented in
tabular form, but due to the limited number of budgeting
intervals (two), the results in the Wareham field are
presented graphically.
The water budget for the first irrigation is shown in
Figure 22. Flow measuring flumes at both the inlet and
exits determined that 12.8 acre-feet were added to the
root zone (11.2 inches), of which 3.4 acre-feet were
transpired by the crop (3 inches). Soil moisture samples
at the beginning and end of the irrigation indicated that
the soil reservoir moisture increased by 7.5 acre-feet
(6.6 inches). The outflow from the drainage system was
measured twice daily resulting in the hydrograph shown in
Figure 23, which indicates about 0.25 acre-feet (0.2 inches)
were actually intercepted by the drain lines. Comparing
these flows indicates that 1.6 acre-feet (1.4 inches) per-
colated past the drains into the deeper groundwater.
Again, it would seem that the poor condition of the soils
limited the effectiveness of the drains.
The irrigations conducted by project personnel were designed
to be as efficient as possible, although this practice may
not have been representative of uncontrolled fields. Two
measures of efficiency, farm efficiency and application
efficiency, can be defined to indicate the degree of
success achieved. Farm efficiency (FE) is calculated by
dividing the sum of evapotranspiration (subtracting
effective precipitation) and root zone soil moisture
storage change by the water supplied to the field. Thus,
FE = (3.4 ac-ft +7.5 ac-ft)/21.6 ac-ft, or slightly over
50%. Application efficiency, which is the same as farm
efficiency except that field tailwater is subtracted
from the denominator, was 85%. Of the flows percolating
into the area of the drain lines, only about 16% was
actually intercepted. However, as stated before, this
fraction should be significantly improved as the field
comes under better management.
The data for the second irrigation, shown in Figure 24,
indicate results similar to the first irrigation, except that
the soils were already moist, resulting in a great deal more
deep percolation. It is interesting to note that the drain-
age system did not remove significantly more water than
during the first irrigation. These facts suggest
75
-------
lnflows = 2l.6af
evapotranspiration = 3.4 af
crop surface-^ T
flow measuring flume
field tailwater= 8.8 af
cr>
JiiUiiilj
root zone
odditions = 12.8 of
root zone boundary
root zone
moisture change:
7.5af
i deep
V percolation= 1.9 af
\ /
tile drain
lines
percolation into
cobble aquifer= 1.6 af
aq fer .;'/.£
;.. ;. _.:;; ;'.'.«.'>?
.' . ?-.-; .*«-' " *..'.
/////s/;/////
mancos shale
water table
field drainage=0.3af
subsurface
return flow= 1.6 af
Figure 22. Graphical water budget for the Wareham farm during its first irrigation
after drain installation.
-------
15
c
"E
10
c
O
C
o
l_
Q
7 8 9 10 II 12 13 14
Duration of first irrigation in Aug , days
16
Figure 23. Average daily discharge from the Wareham farm drainage system during
the first irrigation after installation.
-------
inflow= 16.1 af
evapotranspiration = 2.8 af
crop surface^ T
-o
00
mug
flow measuring flume
field tailwater = 5.3af
root zone v
additions= 10.8 af
root zone boundary
^
root zone
moisture change
0 af
I deep
V percolation=8.0 af
\ / \,
tile drain
lines
percolation into
cobble aquifer = 7.7 af
'-.'i-tt-F.?'-
* &;&£
*.:*-'." V-'J-f-*'-
*.*-V«".i '** **V
.'. ;_"»«'*
'?'* '."**'*''»"**'»
water table
field drainage = 0.3 af
subsurface
return flow=7.7af
mancos shale
Figure 24. Graphical water budget for the Wareham farm during its second
irrigation after drain installation.
-------
that the spacing is too far apart. Hopefully, the
reclamation of the field soils will improve drainage. The
two measures of irrigation efficiency for this irrigation
were 18% for farm efficiency and 26% for application
efficiency, indicating a much poorer irrigation efficiency
because of the already high level of soil moisture storage.
By applying average salinity concentrations measured through-
out the field environs, a salt budget during each irrigation
was determined as shown in Figures 25 and 26. It is inter-
esting that the second irrigation, which was much less
efficient, contributed more than seven times more salt
to the return flow system than did the first. The concen-
tration of salts leaving the drains during the first irri-
gation were 2440 ppm less than the second. Since the
groundwater concentrations in this area are also about
7000-8000 ppm, the drainage system resulted in about 1 ton
of salt reduction as compared to a field without drainage.
The values presented in Figures 25 and 26 are averaged from
about 7-21 water quality analyses and do not necessarily
reflect an important result. During the periods of high
discharge from the drains, the quality is comparable to the
nearby open drain, about 2000-4000 ppm. This would suggest
that the high flows occurred from percolation immediately
over the drains, where the soils had been disturbed.
Irrigation of the Wareham field during ensuing years will
extend the sphere of influence of the drains to the entire
field. When they become completely effective in this manner,
the large quantity of salt contained in the soil profile will
be leached. The salinity concentration in the profile at
that time will approach the 4000-5000 mg/1 level encountered
in the better managed fields. At the present time, the
concentrations of saturated extracts from soils on the
Wareham field are between 13,000 and 17,000 mg/1. If
existing data are indicative of the results to be expected
in the future, it is possible to predict when the drainage
system will have removed the excess salts from the soil
profile. For example, if the annual application efficiency
continues to be about 60%, then approximately twenty
inches of deep percolation will be lost annually. Data
describing the salinity concentration of flows intercepted
by or passing beneath the drainage system reveals an aver-
age of about 5000-7000 ppm. The annual salt pickup can
thus be computed as about 150 tons. If it is further
assumed that the saturated extract represents most of the
salts available in the soil, or at least depletes the
storage to the point where the next extract sample would be no
more than 5000 mg/1, then the salt tonnage to be removed by
the drainage is about 350 tons, assuming also an effective
porosity of 31% (Avars, 1972). Thus, the reclamation of
79
-------
inflows = 14.7tons (500 ppm)
crop surface
00
o
^
flow measuring flume
field tailwater=6tons (500 ppm)
twmw\n Y\f\»tfvi\t'Mi
root zone boundary
salt
^«pickup=4.7 tc
v'
/&-___
/
tile drain
lines
«£ ( :V salt pickup = ?
intTtvTTTT f""-"-irrtl!
± root zone
" additions = 8. 7 to
>ns i deep
v percolation = 8-7
V
^ ~
percolation into
A cobble aquifer =
V (
- - .'. 1 cobble aquife - ;'.'°:.'.
tit Tr rr-" -^-
ns
tons (3360 ppm)
y~
L ^
l.3tons
5200 ppm)
;' «.'-'.': '.?';
-.' :"'"''i". .''.':'"
''' i ''.";' »''"'
-'»'. '.;.Vvo-°' *'»>
water table
field drainage=2.l tons
(5200 ppm)
subsurface
return flow=!7.4 tons
(8000 ppm)
mancos
Figure 25. Graphical salt budget for the Wareham farm during its first irrigation
after drain installation.
-------
inflows = 13.1 tons (600 ppm)
crop surface
co
flow measuring flume
field tailwater=4.3 tons
,, ,,, -f">^1. (600 ppm)
iliJiiiiiA^ *><*
root zone boundary
root zone
additions =8.8 tons
(600 ppm)
salt
I pickup=74.3tons
I deep
V percolation=8.8tons (808ppm)
tile drain
lines
percolation into
cobble aquifer = 80 tons
(7640 ppm)
'cobble aquifer
''/"...."....>..?-.-.
'*.'''''»'.*? -i '*'
''°[.***."-* I'"."*"' ?
.' "?-^! '*"*'*.'."> "
v.>"' :'!*:-v-y.':"
TWW^/////////^^^
water table
field drainage = 3.l tons
(7640 ppm)
subsurface
return flow=83.8 tons
(8000 ppm)
Figure 26. Graphical salt budget for the Wareham farm during its second
irrigation after drain installation.
-------
the Wareham farm should be completed in about three irri-
gation seasons. These figures are/ of course, crude esti-
mates at this point because insufficient data have been
collected. It could be safely assumed that salt leaching
would be the greatest during the first few years. In the
following irrigation seasons, more data will be obtained
to substantiate these results.
To the reader of these results, the small effect of the
drainage system on the Wareham farm probably raises doubts
as to the value of such a salinity control measure. Ques-
tions arise regarding other special salt reducing measures,
such as desalting, because of the high cost of reducing
salinity. The importance of these measures, including
field drainage, nevertheless exists in present salinity
control technology. Each technique has associated with it
an effect and a cost which generally changes in proportion
to the amount of the source that has already been treated.
Thus, an examination of the marginal costs with scale
indicate that an optimal salinity control strategy involves
even the most exotic treatments when the degree of required
treatment becomes high. The evaluation of these factors
and the development of such strategies is the subject of
another research project, but it is these answers which
are sought, not how well drainage or canal lining works.
It is therefore important that the development of "what to
do" be soundly based on "how to do", which is a major
objective of projects such as this.
Analysis of Other Data
During the period of this project, samples of water were
taken from the water table under several fields included
in both the irrigation scheduling and drainage phases.
Some of these data were presented in SECTION VI. Values
of groundwater salinity generally exceed these data by
30 to 50%, indicating that significant salts are picked up
beyond the farm environment. It should be noted that much
of the salt in the upper soils is undoubtedly due to poor
drainage and would be eventually leached. However, studies
should be forthcoming to completely substantiate this con-
clusion.
The data from better managed fields indicate that field
drainage has much more potential than indicated on the Ware-
ham farm. However, the real need for field drainage is
affected by the improvements in water management on the
farm and in the conveyance system. This subject will be
discussed separately in the following section.
82
-------
SECTION VIII
DRAINAGE EVALUATION FOR GRAND VALLEY
The use of drainage systems in the Grand Valley for reducing
the salinity of irrigation return flows requires that the
groundwater be removed before it has reached chemical
equilibrium with the underlying aquifers. Since these
requirements restrict drainage methods to field relief
systems, several questions regarding the feasibility of
this program remain unanswered if improvements are made
in conveyance and irrigation networks. Such questions
include:
1. If conveyance and farm improvements are made,
what will be the field drainage requirements?
2. Since pump drainage has been clearly demonstrated
as the cheapest and more effective method, is it
possible that treatment of these flows is a better
strategy?
3. How are drainage or salinity control policies
reflective of future changes such as urbanization,
energy development, food and fibre needs, and
social goals?
4. Will future technological advances view these
decisions favorably?
Certainly, the results of this study do not answer these
questions since they demonstrate only that some measure of
salinity control is possible with relief drainage. In
this section, the intent is to determine the effect which
other salinity control measures will have on drainage
requirements and test the feasibility of pump drainage in
conjunction with desalination. To accomplish this task,
limited as it will be by the lack of evidence, the first
topic must be a definition of the local hydro-salinity
system.
GRAND VALLEY HYDRO-SALINITY SYSTEM
Unfortunately, during a period of great'concern for the
problem of salinity in the Colorado River Basin, the impact
of individual salinity sources is encompassed within the
limits of measurement accuracy. In the Grand Valley area,
the depletion from the Colorado and Gunnison Rivers, as
well as the salt contributed by the area, is less than
five percent of the mean annual flows. This allows those
83
-------
with limited vision and questionable competence to suggest
the valley salt contributions and corresponding impacts
of salinity control alternatives remain in question. Some
insist that general data deficiencies preclude meaningful
formulation of plans for local improvement or for justifying
one project over another. A look at what can be said
with existing data may be helpful.
There are two methods for establishing the impact an area
has on water and salt flows. The first is the input-output
model alluded to above and the second is hydro-salinity
modeling of the internal water uses.
Input-Output Analysis
Inflows to the Grand Valley occur as flows in the Colorado
River, Gunnison River, and precipitation. In addition, a
small quantity of water is imported for domestic and indus-
trial purposes, and a possibility exists that precipitation
on the watershed adjacent to the valley may contribute
via diffuse groundwater inflows. Neither of these latter
flows are deemed significant, especially the inflow from
surrounding lands because of the low annual precipitation
(8-10 inches) and high evaporative demands (40-45 inches).
As a means of better identification, data for the 1968
water year from the U.S. Geological Survey (USGS) and U.S.
Weather Bureau can be utilized. Inflows passing the USGS
gaging stations "Colorado River near Cameo" (2,413,000
acre-feet), "Plateau Creek near Cameo" (112,000 acre-feet),
and "Gunnison River near Grand Junction" (1,444,000 acre-
feet) totaled 3,968,000 acre-feet carrying an estimated
salt load of 3,070,500 tons. The outflows passing the
station "Colorado River at Colo-Utah State Line" totaled
3,722,000 acre-feet and approximately 3,771,000 tons of salt.
These figures represent either published data or inter-
polations thereof. It should be noted that the state line
station collects only limited quality data,
A comparison of the inflows and outflows indicates that
246,000 acre-feet of water were depleted from the system
and 701,000 tons of salt added. Precipitation records
indicate that approximately 75,000 acre-feet fel-1 on the
land encompassed by-the irrigated boundaries of which it is
estimated that 25,000 acre-feet could be classed as "effec-
tive on the irrigated acreages." These estimates are :
congruent with similar computations presented by lorns,
et al. (1965), Hyatt (1970), U.S. Environmental Protection
Agency (1971).
84
-------
Another check on these numbers can be made from land use
data collected by Walker and Skogerboe (1971) which was
summarized earlier in Figure 4. A somewhat more definitive
breakdown is presented in Table 12. Westesen (1974)
estimated that the consumptive use based on the pan
Table 12. AGRICULTURAL LAND USE IN THE GRAND VALLEY,
Land Use
Irrigated
Idl =
Dwelling & Premises
Open Water
Phreatophyte
Natural Terrain
Total 1
Acreage
60,844
9,706
10,678
1,699
15,174
16,607
114,708
Percent
of Total
53
8.5
9.3
1.5
13.2
14.5
100.0
Roads and railways have been omitted.
evaporation data from the U.S. Weather Bureau and calcula-
tions using the Modified Jensen-Haise method amounted to
about 295,000 acre-feet annually, including almost 25,000
acre-feet of effective precipitation on other vegetative
uses. Thus, the inflow-outflow data for this particular
year regarding water flow is acceptable. An examination of
the salt flows will be noted for comparison in the following
paragraphs.
Hydro-Salinity Budgeting
The second approach to establishing the effects of water
use in the Grand Valley is to model the complex inter-
relationships associated with irrigation and drainage.
Several parameters are added to the analysis to account
for the various flows which take place.
The first segment encountered is the delineation of the
canal diversions. As the water is diverted from the
rivers into the canals and ditches, a certain portion of
85
-------
the flow seeps or evaporates from the conveyance surfaces,
while still another fraction is spilled into wasteways as
a means of regulating capacity. The remainder of the flow
is diverted through small headgates into an extensive lat-
eral system leading to the fields. It is important in
this type of analysis that each flow path be defined,
because each results in a different salinity effect. For
example, the evaporative losses concentrate the salts in
the remaining flows, whereas the seepage enters the saline
groundwater basin and results in salt pickup.
Lateral diversions eventually become seepage, field tail-
water, root zone additions or evaporation, as was the
case above. In a similar manner, the root zone additions
result in cropland consumptive use or deep percolation.
When deep percolation is combined with seepage losses, a
groundwater flow segment is begun which results in the
severe salt loadings common in the valley. A great deal
of the groundwater is consumed by water-loving phreato-
phytes abundant in the area and some of the flows are
intercepted by the open-ditch drainage system. A substan-
tial amount returns to the rivers through aquifers making
precise measurement difficult.
Westesen (1974) examined the 1968 water year in some detail
and combined many of the principles discussed by Walker
(1970) into an accounting of the flows derived for irri-
gation in the Grand Valley. His results, shown in Tables
13, 14, and 15, compare very well with data collected by
the authors in recent years.
Interpretation of Data
The budgets contained in Tables 13, 14, and 15 include some
important insights to the water use practices in the Grand
Valley. It has generally been the practice to state the
results of budgeting procedures in terms of efficiencies,
in order to extend the conclusions to other areas. Most
notable, efficiencies such as conveyance efficiency, irriga-
tion efficiency, etc. are commonly found in the literature.
Since a great deal of variation can be found in the specific
definitions of these terms, the following paragraphs will
define a term and discuss its value in the Grand Valley.
Possibly the most general measure of how well water is
utilized in an agricultural area could be termed regional
irrigation efficiency. If irrigation efficiency is defined
as the percentage of the total diversions which are bene-
ficially used by crops, then from Table 15 it can be seen
that for the Grand Valley an efficiency of about 27% will
86
-------
Table 13. GRAND VALLEY WATER BUDGET FOR 1968 WATER YEAR.
Budget Item Acre-Feet
Surface Inflows
Colorado River near Cameo, Colorado 2,413,000
Plateau Creek near Cameo, Colorado 112,000
Gunnison River near Grand Junction,
Colorado 1,443,000
Total 3,968,000
Effective Precipitation
Cropland 25,000
Phreatophytes Total 5,400
30,400
System Depletions
Water Surface Evaporation
Canals 8,000
Rivers 8,000
Phreatophyte Consumption
Along Canals and Drains 64,000
Adjacent to Rivers 21,400
Cropland Consumption 175,000
Total 276,400
Surface Outflows
Colorado River at Colorado-Utah State Line 3,722,000
87
-------
Table 14. GRAND VALLEY DISTRIBUTION OF CANAL FLOWS IN 1968
Budget Item
Canal Diversions
Spillage
Seepage
Evaporation
Lateral Diversions
Acre-Feet
560,000
Total
Acre-Feet
^103,000
25,000
8,000
424,000
560,000
Lateral Diversions
Seepage
Field Tailwater
Root Zone Diversions
424,000
Total
51,000
162,000
211,000
424,000
Root Zone Diversions
Evapotranspiration
Deep Percolation
211,000
Total
150,000
61,000
236,000
Groundwater Return Flows
Phre a tophyte Cons umpt i on
Subsurface and Drain Flows
137,000
Total
60,000
77,000
137,000
88
-------
Table 15. SALT BUDGET FOR GRAND VALLEY DURING 1968.
Budget Item
Flow
(acre-feet)
Inflows
Colorado River 2,413,000
near Cameo
Plateau Creek 112,000
near Cameo
Gunnison River 1,443,000
near Grand Jet.
Concentration Salt Load
(ppm)
(tons)
454
454
769
1,490,000
69,000
1,511,000
Total 3,070,000
Outflows
Colorado River 3,722,000
near Colo-Utah
State Line
745
3,771,000
Salt Pickup
701,000
89
-------
be realized. This efficiency is determined by dividing the
cropland consumption minus effective precipitation by the
canal diversions. To improve irrigation efficiency, several
management practices and structural improvements could be
made by canal companies and irrigation districts. For
example, by eliminating spillage in the system as a means
of capacity management and replacing it by call periods and
diversion regulation, the efficiency could be increased by
18% to more than 45%. Canal linings would further enhance
this measure to almost 50%. The other available improve-
ments are largely of an individual nature depending on the
care and control of water by the irrigators.
Associated with the irrigation efficiency noted above are
two more specific measures of conveyance efficiency. Canal
conveyance efficiency and lateral conveyence efficiency
may be taken as the percentages of the carried flows
which reached the intended destinations. In the valley,
the efficiencies of both systems are 94% and 88%, respec-
tively.
Once the flows reach the lateral and farm ditch systems, it
is possible to attach an efficiency measure to the irri-
gators themselves. Skogerboe and Walker (1972a) define
farm efficiency as the percentage of water availalbe to the
farm which is consumptively used. Thus, farm efficiency is
approximately 35%. This-value can also be significantly
improved by better water management. Specifically, the
minimization of field tailwater and lateral linings could
potentially increase farm efficiency to 86%. Certainly,
a reasonable figure would be 60-70% if effective programs
were undertaken.
Probably the most important measure of efficiency with
respect to salinity control is termed application effi-
ciency. This value represents the fraction of the flows
applied to the root zone reservoir that is utilized by
the crops. Its importance is that deep percolation is
directly evaluated. In the Grand Valley, an average
value of application efficiency is about 71%. The most
significant improvement to this value can be made through
a coordinated and effective irrigation scheduling program.
Although other conclusions can be drawn from these budgets,
the preceding discussion will serve the following exami-
nation of drainage alternatives.
IMPACT OF WATER MANAGEMENT ON DRAINAGE
The water and salt flows for the 1968 Water Year are typical
of results presented by several investigators such as lorns,
90
-------
et al. (1965), Hyatt (1970), and the U.S. Environmental
Protection Agency (1971). The important budget parameter,
salt pickup, is currently a topic of wide discussion, but
its value for the Grand Valley can be expected to vary be-
tween 0.5 and 1.0 million tons of salt annually. In the
opinion of the authors after several years of detailed
study of the Grand Valley area, the variation in salt pickup
is probably due primarily to the available data rather than
periodic changes in water use practices.
With these budget data as the basis, it is interesting to
examine the need for field drainage as improvements become
implemented in the irrigation system. Such local improve-
ments as canal linings, lateral linings, and better on-farm
water management (irrigation scheduling in its total per-
spective, which includes on-farm irrigation improvements)
will affect water table levels by significantly reducing
the groundwater inflows and thus easing the demand on the
natural drainage mechanisms. Several examples may demon-
strate this point. In 1970, a canal and lateral lining
program was undertaken as part of an earlier phase of this
project with the results reported by Skogerboe and Walker
(1972a). Several farmers below the Mesa County Ditch
have since related to the authors that the linings seemed
to lower local water tables and significantly improve their
lands. Another example occurred as a part of a small
lateral lining project further west by the Soil Conservation
Service ASCS program in which nearby water tables were lowered
several feet. Such examples are commonly reported in the
Grand Valley area and are considered the basis for suggesting
conveyance channel linings may be a partial solution to
salinity.
One other aspect of the Grand Valley condition that should
be mentioned. The cobble aquifer underlying (one-half) of
the valley is on the order of 1Q3 to 104 more permeable
than the soils, yet the hydraulic gradients are quite compar-
able. The obvious conclusion must be that most irrigation
return flows passing through the groundwater system are
occurring as flow in this aquifer. As a result, most flows
from seepage or deep percolation are moving downward
rather than laterally. A notable exception exists when the
leaky aquifer develops a vertical gradient and supplies
water to the upper water table.
The previously noted conditions suggest that much of the
local water table problems are due to over-irrigation,
especially along the higher northern lands in the area.
Lower areas and isolated trouble spots are affected by
excessive groundwater flows trying to leave the area.
If the local canals and laterals were lined (including
farm head ditches). Table 14 indicates that 77,000 acre-feet
91
-------
annually, which amounts to 55% of the groundwater inputs,
would be prevented from contributing to local drainage prob-
lems. (If only the canals were lined, the groundwater
would be decreased by only 18%). Such improvements may
also reduce the evapotranspiration from phreatophytes and
result in significant water savings as well. Canal linings
appear to be the initial program for controlling salinity
in the Grand Valley although it is the least effective
alternative available.
Probably the greatest potential for salinity control lies
in on-farm water management which directly includes the
lateral conveyance system. Together, deep percolation and
lateral seepage contribute 82% of the groundwater flows.
If effective irrigation scheduling programs are incorporated
locally, which means accompanying the scheduling services
with rehabilitation of the irrigation systems, the need
for field drainage will be diminished.
Thus, the first steps in a salinity control program are to
minimize: (a) seepage losses from canals and laterals;
and (b) deep percolation losses from croplands (ideally,
the deep percolation losses would not exceed the leaching
requirement). By minimizing the amount of moisture reaching
the groundwater, the requirements for field drainage will
also be minimized. As higher levels of salinity reduction
are sought, field drainage becomes a more feasible com-
ponent of a valley-wide salinity control program.
PUMP DRAINAGE AND DESALINATION
The development of salinity control technology to date
has been exclusively oriented towards preventing the flows
from contacting saline soils and aquifers. An alternative
approach would be to simply treat the salt ladened irriga-
tion return flows. Such a program in the Grand Valley area
could either be through a system of field relief drains
intercepting the downward flows or pump drainage, both of
which would be collected and desalted.
Desalting Technology
The technology of desalting brackish waters, or even highly
mineralized sea water, is developing at an exciting rate. ,
However, until recently, its use has been primarily to
produce high quality water rather than treat brackish flows
to amend regional salinity problems. For waters having
salinity concentrations between 2,000 and 10,000 ppm, the
two most feasible desalination processes are reverse
osmosis and electrodialysis. Desalination plants of this
nature have generally indicated some economy with scale and
92
-------
have, therefore, tended to be large. Small plants with
capacities up to 10 cfs show only slight economies with
scale, and since such plants are likely to be more appli-
cable in the Grand Valley, their cost can be assumed
high. A more detailed analysis is beyond the scope or
intention of this report.
The costs of treating the groundwater flows, such as those
in the Grand Valley, are reported to be on the order of $150
per acre-foot. Thus, for the local groundwater, the costs
per ton of salt removed would be about $15 per ton of salt
removed assuming a product water with 500 ppm. This figure
agrees generally with data reported by Westesen (1974).
Desalting Pump Drainage Effluents
The earlier review of pump drainage experiments in the
Grand Valley indicated that the wells affected an area up
to one-half mile in diameter with a discharge of less than
280 gallons per minute (0.56 cfs). To pump significantly
more than this quantity of groundwater would have exceeded
the inflow to the well area. As a result, to establish a
10 cfs flow into a desalination plant would require a
considerable collection and conveyance system. Plants
larger than 10 cfs would not likely be utilized in the
Grand Valley since the economies of scale would be more
than offset by the transmission costs. Thus, desalting
drainage effluents in the area could be expected to remove
salts for about $15 per ton plus pumping and transport
costs, which may amount to less than $5/ton (Westesen,
1974) .
Table 14 points out that the 77,000 acre-feet of groundwater
return flow contributes 701,000 tons of additional salts
to the Colorado River. The use of pump drainage and
desalting in controlling this salt loading depends on the
relative feasibility of improving the elements of the irri-
gation system. As a basis for comparison, the annual costs
of collecting and treating the groundwater at an assumed
rate of $17 per ton of salt removed are about $12 million.
Westesen (1974) derives cost functions for canal linings,
lateral linings, and on-farm improvements and then opti-
mizes these functions to arrive at optimal dollar invest-
ments to achieve various degrees of salt loading reduc-
tions in the Grand Valley. This analysis indicates an
annual cost of $5.4 million (6-7/8% interest and 50
year repayment period) to achieve a maximum reduction
of 582,000 tons by reducing canal seepage by 15,000 acre-
feet, lateral seepage by 33,000 acre-feet, and on-farm
deep percolation by 54,900 acre-feet. The additions to
the groundwater from canal and lateral seepage after linings
93
-------
would produce 163,000 tons of salt pickup/ whereas the
deep percolation from the crop lands amounting to 4% leach-
ing would be more saline than the groundwater and there-
fore pickup no salt. Thus, if the remaining 163,000
tons of salt were removed through desalting, ($1.8 million
annual cost), the costs would be $7.2 million annually ($5.4
million plus $1.8 million) to produce a zero salinity
discharge from the Grand Valley. It can thus be seen, that
desalting drainage flows is necessary to achieve zero
discharge, but in a gradually implemented salinity control
program, it is likely to be added after much of the
irrigation system is improved. It should be noted, however,
that the point where such use of desalting of irrigation
return flows is made should be determined by a more
exhaustive analysis.
94
-------
SECTION IX
BIBLIOGRAPHY
1. Ayars, J.E. 1972. Drainage of Irrigated Lands in
Grand Valley. MS Thesis. Agricultural Engineering
Department, Colorado State University, Fort Collins,
Colorado.
2. Brooks, R.H. and A.T. Corey. 1964. Hydraulic Proper-
ties of Porous Media. Colorado State University.
Hydrology Paper No. 3, Fort Collins, Colorado.
3. Christiansen, J.E. and C.J. Grassi. 1969. Manual
on Drainage of Irrigated Lands. Utah State
University, Logan, Utah. March.
4. Corey, A.T. 1961. Subsurface Drainage. Class notes
for AE 560. Agricultural Engineering Department,
Colorado State University, Fort Collins, Colorado.
5. Decker, R.S. 1951. Progress Report on Drainage Pro-
ject (1945 to January, 1951) Grand Junction, Colo-
rado. Unpublished report. Lower Grand Valley
Soil Conservation District, Mesa County, Colorado.
January.
6. Duke, H.R. 1972. Drainage Design Based on Aeration.
Unpublished PhD Dissertation, Colorado State
University, Fort Collins, Colorado.
7. Dumm, L.D. 1954. Drain-Spacing Formula. Agricultural
Engineering. Vol 35, No 10, p 726-730. October.
8. Dumm, L.D. 1964. Transient-Flow Concept in Subsur-
face Drainage: Its Validity and Use. Transactions
of the American Society of Agricultural Engineers,
Vol 7, No 1, p 142-146, 151.
9. Dumm, L.D. 1967. Transient-Flow Theory: Its Uses
in Subsurface Drainage of Irrigated Land. Paper
presented at the Water Resources Conference,
Irrigation and Drainage Division, ASCE, New York,
New York.
10. Hagen, R.M., H.R. Haise and T.W. Edminster: 1967.
Irrigation of Agricultural Lands. Agronomy
Monograph Series No. 11, American Society of
Agronomy, Madison, Wisconsin.
95
-------
11. Hyatt, M.L. 1970. Analog Computer Model of the
Hydrologic and Salinity Flow Systems Within the
Upper Colorado River Basin. Unpublished Ph.D.
Dissertation. Department of Civil Engineering,
Utah State University, Logan, Utah. November.
12. lorns, W.V., C.H. Hembree, and G.L. Oakland. 1965.
Water Resources of the Upper Colorado River Basin.
Technical Report. Geological Survey Professional
Paper 441. U.S. Government Printing Office,
Washington, D.C.
13. Kirkham, D. 1960. Seepage into Ditches from a Plane
Water Table Overlying a Gravel Substratum. Journal
of Geophysical Research, Vol 65, No 4, p 1267-
1272. April.
14. Luthin, J.N. 1966. Drainage Engineering. John Wiley
and Sons, Inc. New York.
15. Maasland, M. and H.C. Haskew. 1957. The Auger Hole
Method of Measuring the Hydraulic Conductivity of
Soil and Its Application to Tile Drainage Problems.
3rd Congress of the International Commission on
Irrigation and Drainage. 8:8.09 - 8.14
16. Miller, D.G. 1916. The Seepage and Alkali Problem
in the Grand Valley of Colorado. Office of
Public Roads and Rural Engineering, Drainage Inves-
tigations. March.
17. Shumaker, G.A., C.W. Robinson, W.D. Kemper, H. Golus,
and N. Amemiya. 1967. Improved Soil Productivity
in Western Colorado with Fertilizers and Alfalfa.
Colorado Agricultural Experiment Station Technical
Bulletin 91. January
18. Skogerboe, G.V. and W.R. Walker. 1972a. Evaluation
of Canal Lining for Salinity Control in Grand
Valley. Environmental Protection Technology
Series, EPA-R2-72-047. Office of Research and
Monitoring, U.S. Environmental Protection Agency,
Washington, D.C. October.
19. Skogerboe, G.V..and W.R. Walker. 1972b. Grand Valley
Salinity Control Demonstration Project, Data Report.
Environmental Protection Agency, Project 13030 DOA.
Contract 14-01-201. Agricultural Engineering
Department, Colorado State University, Fort Collins,
Colorado. September.
96
-------
20. Skogerboe, G.V., W.R. Walker, J.H. Taylor and R.S.
Bennett. 1974. Evaluation of Irrigation Schedu-
ling for Salinity Control in Grand Valley. Environ-
mental Protection Technology Series, EPA-660/2-74-
052. Office of Research and Monitoring, U.S.
Environmental Protection Agency, Washington, D.C.
June.
21. U.S. Department of Agriculture, Soil Conservation Ser-
vice. 1971. National Engineering Handbook Section
16, Drainage of Agricultural Land. May.
22. U.S. Department of Agriculture, United States Salinity
Laboratory. 1954. Diagnosis and Improvement of
Saline and Alkali Soils. Agriculture Handbook No
60. February.
23. U.S. Environmental Protection Agency. 1971. The
Mineral Quality Problem in the Colorado River
Basin. Summary Report and Appendices A,B,C, and D.
Regions VIII and IX. Denver, Colorado.
24. van Schilfgaarde, J. 1970. Theory of Flow into Drains.
Advances in Hydroscience, Vol 6, Academic Press.
New York.
25. Walker, W.R. 1970. Hydro-Salinity Model of Grand
Valley. Unpublished M.S. Thesis. Civil Engineering
Department, Colorado State University, Fort Collins,
Colorado. August.
26. Walker, W.R. and G.V. Skogerboe. 1971. Agricultural
Land Use in the Grand Valley. Agricultural
Engineering Department, Colorado State University,
Fort Collins, Colorado. July.
27. Westesen, G.L. 1974. Salinity Control for Western
Colorado. Unpublished Ph.D. Dissertation. Agri-
cultural Engineering Department, Colorado State
University, Fort Collins, Colorado.
28. Winger, R.J./ Jr. and J.N. Luthin. 1966. Guide for
Investigations of Subsurface Drainage Problems
on Irrigated Lands. American Society of Agricul-
tural Engineers. SP-04-66,
97
-------
SECTION X
LIST OF PUBLICATIONS
U.S. Environmental Protection Agency and Colorado State
University. 1972. Managing Irrigated Agriculture to
Improve Water Quality. Proceedings of National Con-
ference on Managing Irrigated Agriculture to Improve
Water Quality. May 16-18, Grand Junction, Colorado.
Ayars, J.E. 1972. Drainage of Irrigated Lands in Grand
Valley. Unpublished M.S. Thesis, Agricultural Engin-
eering Department, Colorado State University, Fort
Collins, Colorado.
Skogerboe, G.V., Walker, W.R., Bennett, R,S., and Taylor,
J.H. 1973. Irrigation Scheduling for Reducing
Salinity from Grand Valley. Paper 73-2532. Presented
at the 1973 Winter Meeting of the American Society of
Agricultural Engineers, December 11-14, 1973. Chicago,
Illinois.
Bargsten, G., Skogerboe, G.V., and Walker, W.R. 1974.
The Grand Valley: An Environmental Challenge.
Colored brochure and taped slide presentation prepared
by Colorado State University.
98
-------
SECTION XI
LIST OF SYMBOLS AND EQUIVALENTS
Symbol Definition
CS canal seepage, acre-feet
3/D saturated depth below drains, ft
d depth of water table below auger
hole, ft
depth of evapotranspiration, in
depth of drainage water, in
depth of irrigation water, in
DR drainage outflow, acre-feet
EC, specific conductance of drainage
water, ymhos/cm
EC. specific conductance of irrigation
water, umhos/cm
E potential evapotranspiration from
well-watered alfalfa, cal cm"
day"1
ET evapotranspiration by agricultural
crops, acre-feet
GW groundwater inflows from artesian
aquifers, acre-feet
GW, downward drainage to pumped aqui-
fer, acre-feet
GW. ' net groundwater inflow, or outflow
10 from adjacent areas, acre-feet
GWS groundwater storage change, acre-
feet
h water table height above drains, ft
h water table height at the midpoint
m between drains, ft
H initial saturated thickness of
aquifer at midpoint between
drains, ft
H equivalent permeable height above
* water table, ft
H equivalent saturated height above
s water table, ft
i hydraulic gradient ft/ft
IR deep percolation, acre-feet
K Hydraulic Conductivity, in/hr
99
-------
Symbol Definition
P precipitation, acre-feet
Q volumetric flux rate, cfs ,
R solar radiation, cal cm 2 day
s
s distance from bottom of the auger
hole to the impermeable boundary, ft
S,X,L distance between drains, ft
t measure of various times , days , hrs
T temperature , °F
T ,C. ,C, ,C~,C,, regional constants
X "t J. £ ti
w uniform recharge rate, in/day
y distance from static water table to
elevation of water in auger hole, ft
y total depth of drawdown in auger hole,
ft
Y, equivalent permeable thickness of
aquifer , ft
Y equivalent saturated thickness of
3 aquifer , ft
y . height of water table at a distance
x from drains at time t, ft
z,Y saturated thickness of aquifer, ft
z height above water table where
a adequate soil aeration exists, ft
a diffusivity, m-ft/hr
c|>d' specific yield, %
effective porosity
ENGLISH-METRIC EQUIVALENTS
1 inch = 2.54 centimeters
1 foot = 0.3048 meters
1 acre-foot = 1,233.62 cubic meters
1 cubic foot per second = 0.02832 cubic meters per second
1 gallon (U.S.) per minute = 0.06308 liters per second
1 degree Fahrenheit = 5/9 degrees centigrade
100
-------
SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
.-!.''Report No,
w
4. Title EVALUATION OF DRAINAGE FOR SALINITY CONTROL
IN GRAND VALLEY,
7. AiuhoKs) Skogerboe, G.V., waiJcer, W.R., Bennett,
Ray S., Ayars, James E., Taylor, James H.
Agricultural Engineering Department, Colorado
State University, Fort Collins, Colorado.
12, Sponsoring .Organization
15. Supplementary N'otc:-
EPA Report No. EPA-660/2-74-084, August 1974.
5. Report Date
6.
8. Performing Organization
Recori No,
11. Conirjot/G-'ar.l No
S-800278
13 Ti ::-? of Report and
J- vn.d Covered
16. Abstract
Irrigation return flows in the Grand Valley of Western Colorado con-
tribute to the serious salinity problems in the Colorado River Basin by
carrying large salt loads resulting from contact with local saline soils
and aquifers. Since the valley is one of the more significant salt
sources, it is therefore a logical area for evaluation of the effective-
ness of various salinity control measures. This study has emphasized
two on-farm control alternatives, namely, irrigation scheduling and
field drainage. The contents of this report consider the latter measure.
Three farms were extensively studied during the 1972 and 1973 irrigation
seasons to identify drainage needs and the effect field relief drainage
would have on reducing salinity in the return flows. During the spring
of 1973, a perforated plastic pipe drainage system was installed on one
of the farms. Each farm was then incorporated into an irrigation
scheduling program. The results indicate that while field drainage is
effective in skimming water off the top of the water table where salinity
concentrations are typically 20%-30% less saline, the high costs
emphasize the need to reduce seepage losses by lining canals and mini-
mize deep percolation losses through improved on-farm water management *
order to minimize the requirements for drainage facilities.
in
Colorado River, *Deep percolation, Drainage, Irrigation, Irrigation
effects, Irrigation efficiency, Irrigation water, *Return flow, Saline
soils. Saline water, *Salinity, Water distribution (applied), Water loss,
Water pollution sources, Water quality.
i?b. identities Grand Valley, Irrigation management, Salinity control.
17c. COWRR Field & Group
18. Availability
19. Security Glass.
(Report)
20. Security Class.
2-1. No. of
Pages
21. Price
Send To:
WATER RESOURCES SCIENTIFIC INFORMATION CENTER
UA. DEPARTMENT OF THE INTERIOR
WASHINGTON. D.C. tO240
Abstractor Gaviorfl w. Skoaerboe
Institution
Colorado State University
/YRSIC 102 {REV. JUNE 1971)
------- |