EPA-R 2-73-265
June 1973 Environmental Protection Technology Series
Irrigation Management For Control
of Quality of Irrigation Return Flow
Office of Research and Monitoring
U.S. Environmental Protection Agency
Washington, D.C. 20460
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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
U. Environmental Monitoring
5. Socioeconomic Environmental Studies
i •• ".,
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.
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EPA-R2-73-265
June 1973
IRRIGATION MANAGEMENT
FOR CONTROL OF
QUALITY OF IRRIGATION RETURN FLOW
by
Larry G. King
R. John Hanks
Utah State University
Logan, Utah 84322
Project #13030 FDJ
Program Element #1B2039
Project Officer
Dr. James P. Law, Jr.
U. S. Environmental Protection Agency
Robert S. Kerr Environmental Research Laboratory
P. O. Box 1198
Ada, Oklahoma 74820
Prepared for
OFFICE OF RESEARCH AND MONITORING
U. S. ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D. C. 20460
- -•' f "; >j \ i », ". '« ', V.n^^.
For sale by the Superintendent of Documents, pfigt •flwernmeg^Printlng Office, Washington, B.C. 20402
Price $3.45 dotijestic pD^tpaid tfr^yg^) Bookstore
' ' '*"'" • M "
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EPA Review Notice
This report has been reviewed by the Environmental
Protection Agency 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.
11
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ABSTRACT
Maintaining irrigated agriculture on a permanent basis is impossible
without some deterioration of quality of water as it moves through the
soil to the groundwater and eventually returns to the stream. Even if
all salt loading could be eliminated, the concentrating effect would
remain because the process of evapotranspiration extracts nearly pure
water leaving the salts behind. Control over irrigation return flow
quality is desirable. One possibility for control might be to use the
unsaturated soil profile including the crop root zone as a temporary
salt reservoir and provide excess water for leaching and salt discharge
when desired. Such control requires detailed knowledge of water and
salt movement through the root zone of the crops.
Two models were developed and tested in the field for describing flow
of water and salt through the soil with extraction of water by evapo-
transpiration. One model was designed for use as an irrigation man-
agement tool while the other model was initially intended to provide a
detailed understanding of the water and salt flow through the soil. The
best management model will probably result from a combination of
the two models described in this report.
Timing of irrigation was tested as a management variable. With all
other conditions the same, the model predicts that as the time interval
between irrigations increases, the season totals of salt removed from
the root zone, salt remaining in the profile, and water required for
leaching tend to level off. However, the irrigation frequency has a
significant effect upon when the salt is discharged during the season.
Results indicate that managing irrigation for control of return flow
quality requires good control of depth and timing of irrigations. Some
needs for further research are given in the report.
111
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CONTENTS
Section Page
I Conclusions 1
II Recommendations 3
III Introduction 7
IV Review of Literature 11
V Development of Models 25
VI Testing of Models 59
VII Use of Models for Irrigation Management 163
VIII Summary 177
IX Acknowledgments 183
X References 185
XI Publications Resulting From Project 191
XII Appendices 193
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FIGURES
No. Page
1 Typical layer of soil in simplified model. 27
2 Location map, Hullinger farm, Vernal, Utah. 60
3 Farm layout. 6l
4 Pressure potential vs water content for Mesa sandy
loam soil. Condition A was used in the computation.
Condition B was used to test the sensitivity of the
model. 79
5 Water content vs hydraulic conductivity for Mesa
sandy loam soil. 80
6 Variation of Ca-Mg exchange coefficient with solution
concentration (a) surface soil, (b) subsoil. 83
7 Variation of Ca-Na exchange coefficient with solution
concentration (a) surface soil, (b) subsoil. 84
8 Measured values (points) of leaching factor at three
initial moisture contents compared with curves
calculated from the leaching factor function. 91
9 Logarithmic plot of leaching factor vs effluent ratio
used to develop the leaching factor function showing
measured values (points) compared to curves calcu-
lated from the resulting leaching factor function. 93
10 Upper limit of field moisture, Qr , in each soil layer
fm
in Block 5 as determined from moisture content mea-
sured 9. 5 and 33. 5 hours after an irrigation ended
(measured values are averaged from 5 locations). 106
11 Comparison of measured (M) and calculated (C) pro-
files of moisture content, 9, and electrical conductivity
of soil solution, EC , for Block 3. 109
s
VI
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FIGURES (Continued)
No. Page
12 Comparison of measured (M) and calculated (C) pro-
files of moisture content, 9, and electrical conductivity
of soil solution, EC , for Block 5. 110
s
13 Comparison of measured (M) and calculated (C) pro-
files of moisture content, 9, and electrical conductivity
of soil solution, EC , for Block 6. Ill
s
14 Comparison of measured (M) and calculated (C) pro-
files of moisture content, 9, and electrical conductivity
of soil solution, EC , for Block 7. 112
s
15 Comparison of measured (M) and calculated (C) pro-
files of moisture content, 9, and electrical conductivity
of soil solution, EC , after adjusting moisture extrac-
s
tion pattern to minimize differences in calculated and
measured 9 profiles for Block 3. 117
16 Comparison of measured (M) and calculated (C) pro-
files of moisture content, 9, and electrical conductivity
of soil solution, EC , after adjusting moisture extrac-
s
tion pattern to minimize differences in calculated
and measured 9 profiles for Block 5. 118
17 Measured (M) EC for Block 3 compared with calcu-
s
lated (C) values resulting from letting ER = 0. 5 ER,
ER is effluent ratio. 119
18 Measured (M) EC for Block 5 compared with calcu-
s
lated (C) values resulting from letting ER = 0. 5 ER,
ER is effluent ratio. 119
19 Water flux at the surface (evapotranspiration and pre-
cipitation, cm/hr) vs time for oats in the 9-day
interval in 1970. 121
VII
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FIGURES (Continued)
No. Page
20 Comparison of the water content profiles as predicted
(dotted) and measured (solid) for oats in 1970.
(a) 24 hrs, (b) 72 hrs, (c) 120 hrs, (d)2l6hrs 122
21 Comparison of water content profiles as measured
(solid) and predicted (dotted) for crop 1 alfalfa in
1971. (a, c) 24 hrs after precipitation, (b, d) end of
irrigation interval. 124
22 Comparison of water content profiles as measured
(solid) and predicted (dotted) for crop 2 alfalfa in
1971. (a, c) 24 hrs after irrigation, (b, d) end of
irrigation interval. 125
23 Comparison of water content profiles as measured
(solid) and predicted (dotted) for crop 3 alfalfa in
1971. (a) end of irrigation interval, (b) 24 hrs after
irrigation, (c) 48 hrs after irrigation, (d) end of
irrigation interval. 126
24 Comparison of measured (dots) and predicted (solid
lines) water content profiles for alfalfa in 1971.
(a) 30 cm, (b) 70 cm, (c) 100 cm depth. 127
25 Comparison of actual, predicted, and potential evapo-
transpiration during the 9-day period with that pre-
dicted for oats in 1970. 128
26 Variation of actual ET/Penman E for alfalfa in 1971. 129
27 Variation of root water potential of alfalfa in 1971.
The increase in Hroot is due to precipitation.
(a) crop 1, (b) crop 2, (c) crop 3. 131
28 Comparison of actual (dots) and predicted (solid line)
upward flow from the water table for oats during the
9-day interval in 1970. 132
29 Comparison of actual (dots) and predicted (solid line)
upward flow of water from the water table for alfalfa
in 1971. 133
Vlll
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FIGURES (Continued)
No.
30 Hroot during the 9-day period as predicted from 30,
45, and 70 cm root distribution. 135
31 Comparison of measured water content profiles for
soil condition A and B at the end of the 9-day period
in 1970, oats. 136
32 Comparison of measured and predicted water content
profiles at the end of a 9-day period in 1970 assuming
root distribution 30, 45, and 70 cm. 138
33 Comparison of water content profiles as predicted,
9 was initialized after each hay cut (dots), 9 was
initialized at the beginning of the season (solid lines);
(a, c) three days after hay cut, (b, d) at the end of the
crop. 140
34 Cumulative evapotranspiration vs time compared with
predicted evapotranspiration where the lower limit of
Hroot was -40 bars and -20 bars (data for desert soil
from Curlew Valley, Utah). 141
35 Relative root extraction of alfalfa as a function of time
after irrigation and depth. 143
36 Comparison of predicted (dotted) and measured (solid)
water content and total salt concentration profiles for
conditions of Case #1. 144
37 Comparison of predicted (dotted) and measured (solid)
ion concentration profiles for conditions of Case #1. 145
38 Comparison of predicted (dotted) and measured (solid)
water content and total salt concentration profiles for
conditions of Case #2. 147
39 Comparison of predicted (dotted) and measured (solid)
ion concentration profiles for conditions of Case #2. 149
IX
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FIGURES (Continued)
No. Page
40 Comparison of predicted (dotted) and measured (solid)
water content and total salt concentration profiles for
conditions of Case #3. 150
41 Comparison of predicted (dotted) and measured (solid)
ion concentration profiles for conditions of Case #3. 151
42 Comparison of predicted (dotted) and measured (solid)
water content profiles for alfalfa (a) 324 hrs, (b) 339
hrs, and (c) 627 hrs. 153
43 Comparison of saturation extract (solid) and soil sol-
ution (dotted) electrical conductivity profiles for
alfalfa (a) 324 hrs, (b) 339 hrs, and (c) 627 hrs. 154
44 Comparison of predicted (dotted) and measured (solid)
total salt concentration profiles for alfalfa (a) 324 hrs,
(b) 339 hrs, and (c) 627 hrs. Both the predicted histo-
grams and continuous curves are shown. 155
45 Comparison of predicted (dotted) and measured (solid)
calcium concentration profiles for alfalfa (a) 324 hrs,
(b) 339 hrs, and (c) 627 hrs. Both the predicted histo-
grams and continuous curves are shown. 156
46 Comparison of predicted (dotted) and measured (solid)
magnesium concentration profiles for alfalfa (a) 324 hrs,
(b) 339 hrs, and (c) 627 hrs. Both the predicted histo-
grams and continuous curves are shown. 157
47 Comparison of predicted (dotted) and measured (solid)
sodium concentration profiles for alfalfa (a) 324 hrs,
(b) 339 hrs, and (c) 627 hrs. Both the predicted histo-
grams and continuous curves are shown. 158
48 Comparison of predicted (dotted) and measured (solid)
chloride concentration profiles for alfalfa (a) 324 hrs,
(b) 339 hrs, and (c) 627 hrs. Both the predicted histo-
grams and continuous curves are shown. 160
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FIGURES (Continued)
No. Page
49 Predicted drainage and salt concentration of the drainage
water over a period of 627 hrs. 161
50 Generally increasing concentrations of irrigation water
in mmho/cm during the growing season. (The circled
values are the concentrations at each irrigation). 165
51 Generally decreasing concentrations of irrigation water
in mmho/cm during the growing season. (The circled
values are the concentrations at each irrigation). 166
52 Season totals of salt existing, salt leaving, water
applied, and leaching water as functions of irrigation
frequency for problem ACF. 172
53 Season totals of salt existing, salt leaving, water
applied, and leaching water as functions of irrigation
frequency for problem BCF. 173
54 Results of problem ACF for each irrigation of the
season for 8 and 20 days between irrigations. 174
55 Results of problem BCF for each irrigation of the
season for 8 and 20 days between irrigations. 175
56 Hydrograph of discharge from drain 4 during 1971. 283
57 Hydrograph of discharge from drain 5 during 1971. 284
58 Hydrograph of discharge from drain 3 during 1971. 285
59 Hydrograph of discharge from drain 6 during 1971. 285
60 Season total results for problem ACG. 286
6l Season total results for problem BCG. 287
62 Season total results for problem ACH. 288
63 Season total results for problem BCH. 289
XI
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FIGURES (Continued)
No. Page
64 Season total results for problem ACL 290
65 Season total results for problem BCI. 291
66 Season total results for problem ADF. 292
67 Season total results for problem BDF. 293
68 Season total results for problem ADG. 294
69 Season total results for problem BDG. 295
70 Season total results for problem ADH. 296
71 Season total results for problem BDH. 297
72 Season total results for problem ADI. 298
73 Season total results for problem BDI. 299
74 Season total results for problem AEF. 300
75 Season total results for problem BEF. 301
76 Season total results for problem AEG. 302
77 Season total results for problem BEG. 303
78 Season total results for problem AEH. 304
79 Season total results for problem BEH. 305
80 Season total results for problem AEI. 306
81 Season total results for problem BEL 307
xn
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TABLES
No. Page
1 Summary of results from laboratory technique of
soil calibration to determine leaching factor (LF)
for Hullinger farm soil. 30
2 Results of calibration of the neutron probe. 66
3 Irrigation schedules for various irrigation blocks on
the Hullinger farm between first and second cuttings
of alfalfa in 1971. 70
4 Irrigation schedules for various irrigation blocks on
the Hullinger farm between second and third cuttings
of alfalfa in 1971. 71
5 Initial conditions for field experiments. 74
6 Boundary condition in the field experiment for soil
water and salt flow. Started August 17, 1971. 75
7 Chemical composition of irrigation water. 76
8 Initial soil conditions for column experiments. 77
9 Concentrations (EC in mmho/cm) used to determine
LF. 86
10 Leaching factor for various effluent ratios (Mesa
sandy loam, 6.0 inch samples) for initial moisture
content of 0.20 (volumetric). 87
11 Leaching factor for various effluent ratios (Mesa
sandy loam, 6. 0 inch samples) for initial moisture
content of 0. 15 (volumetric). 89
12 Leaching factor for various effluent ratios (Mesa
sandy loam, 6. 0 inch samples) for initial moisture
content of 0. 05 (volumetric). 90
13 Volumetric moisture content (9) measured by neutron
meter on dates of soil sampling. 96
Xlll
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TABLES (Continued)
No. Page
14 EC of the top one foot of soil at six sites within each
e
irrigation block as determined from soil samples
taken on June 22, August 3, and September 9. 97
15 Analysis of variance for EC of soil samples from
"
the top one foot of soil taken on June 22, August 3,
and September 9. 98
16 Irrigation schedule and depth and EC of irrigation
water for Block 3 during the evaluation period. 100
17 Irrigation schedule and depth and EC of irrigation
water for Block 4 during the evaluation period. 101
18 Irrigation schedule and depth and EC of irrigation
water for Block 5 during the evaluation period. 102
19 Irrigation schedule and depth and EC of irrigation
water for Block 6 during the evaluation period. 103
20 Irrigation schedule and depth and EC of irrigation
water for Block 7 during the evaluation period. 104
21 The upper limit of field moisture (9. ) for each soil
fm
layer and irrigation block. 107
22 Net upward movement of water into the soil profile,
as determined from total irrigation water applied,
total ET, and soil moisture measurements. 113
23 Percent moisture extracted by plant roots that is
required to match calculated moisture content
profiles to corresponding measured profiles. 115
24 Comparison of predicted evapotranspiration, evapo-
ration, transpiration, and water flow as influenced
by different soil properties for a nine-day period
starting July 28, 1,970 at Vernal, Utah (no precipitation). 137
xiv
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TABLES (Continued)
No. Page
25 Comparison of evapotranspiration, upward flow of
water from the water table and Hroot at the end of
the nine-day interval in 1970. 137
26 Effect of change in upper boundary condition and root
depth on evaporation, transpiration and upward water
flow (11 days). 139
27 Concentration constraints for each soil layer used in
hypothetical problem. 1 64
28 Depth in inches of water applied during each irrigation. 164
29 Salt leaving the root zone in tons per acre for each
irrigation. 167
30 Depth in inches of leaching water required for each
irrigation. 167
31 Salt leaving the root zone in tons per acre for each
irrigation when the depth of water applied is input. 168
32 Concentration of the soil solution in millimhos per
centimeter after each irrigation interval when the
computed concentration exceeded the critical con-
centration. 169
33 Values of irrigation water EC, initial EC , and con-
s
centration constraints used in simplified model for
solution of 24 problems, (mmho/cm) 171
34 Rain, irrigation and actual evapotranspiration data for
alfalfa in 1971. Rain and irrigation data were measured
by rain gauge, evapotranspiration data -were measured
by the lysimeter. 239
35 Average soil water content (9) of six sites in the field,
as measured by the neutron probe, and equivalent depth
of water in the soil profile for alfalfa in 1971, and for
oats in 1970. 243
xv
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TABLES (Continued)
No. Page
36 Average soil water content (9) of two sites in two ly-
simeters as measured by the neutron probe, and
equivalent depth of water in the soil profile for alfalfa
in 1971. 244
37 Average soil water content (9) of four sites in the field,
as measured by the gamma probe, for alfalfa in 1971. 245
38 Average soil water content (9) of two sites in two ly-
simeters as measured by the gamma probe, for alf-
alfa in 1971. 246
39 Climatic data and potential evapotranspiration as calcu-
lated by Penman modified method for alfalfa in 1971. 247
40 Electrical conductivity (mmho/cm) of drain effluent
measured periodically in the field with a portable
conductivity meter in 1971. 252
41 Typical composition of Drain 5 effluent collected at
one-hour intervals on August 4, 1971. 254
42 Piezometric data typical of conditions during the irri-
gation season on the Hullinger farm (6-29-71). 255
43 Piezometric data typical of early spring conditions on
the Hullinger farm (5-4-71). 257
44 Electrical conductivity of the soil solution (EC ) as
s
calculated from average values of electrical conductivity
of saturation extract (EC ), soil water content by weight
e
at saturation (W ), and from field water content by
e
weight (W), which was obtained from the average vol-
umetric moisture content (9) of each layer and from bulk
density determinations. 259
45 Typical composition of salts in Hullinger farm soils. 261
xvi
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TABLES (Continued)
No. Page
46 Typical composition of groundwater samples from
observation holes. 262
47 Field measurements of EC (|j.mhos/cm) of ground-
water samples from observation holes. 263
48 Field measurements of EC (|j.mhos/cm) of ground-
water samples from selected piezometers. 265
49 Average values of transmissability, T, hydraulic
conductivity, K, specific yield, V, and a from
constant discharge test, a - T/V. 268
50 Values of hydraulic conductivity, K, by auger-hole
method and corresponding specific yield, V, from
Figure 7 of Dumm (1968). 268
51 Soil properties used for computations made. Mesa
sandy clay loam soil. 269
52 Root distribution (RDF), salt content (SE) for alfalfa
in 1971 and initial water content for alfalfa crop 1
(9 ), crop 2 (9 ), crop 3 (0 ) versus depth used for
JL w j
the computations made. 272
53 Root distribution (RDF), assumed for oats in 1970
with initial electrical conductivity (SE), and initial
water content (9 ) versus depth. 273
54 Flux at the surface for alfalfa in 1971, evapotrans-
piration (ET), soil surface flux (WF), positive values
are precipitation, negative values are evaporation, and
salt concentration (SF) versus time. 274
55 Measured bulk density, water content, electrical con-
ductivity, and ion concentration profiles for conditions
of Case #1. 278
XVII
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TABLES (Continued)
No. Page
56 Measured bulk density, water content, electrical
conductivity, and ion concentration profiles for
conditions of Case #2. 279
57 Measured bulk density, water content, electrical
conductivity, and ion concentration profiles for
conditions of Case #3. 280
58 Chemical analyses of saturation extract for field
experiment. 281
59 Water content (9) profiles for salt flow field ex-
periment. 282
60 Electrical conductivity (|j.mho/cm) profiles at the
field water content for the salt flow field experi-
ment. 282
XVlll
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SECTION I
CONCLUSIONS
The models developed and described in this report can be used to
investigate the possibility of exercising some control over irrigation
return flow quality by proper irrigation management. In order to
fully assess the possibilities, further model development and testing
is needed. The simplified model is well suited for investigating a
rather wide range of management variables because of very small
computer time required. However, as pointed out in the body of the
report, some field situations may not be adequately described with
the simplified model in its present form. Its most notable limitation
is the inability to handle upward flow from the water table.
The detailed model does an excellent job of predicting moisture move-
ment in the field. Its ability to predict salt movement needs improve-
ment. The model describes total salt movement better than movement
of individual ions. It was concluded that the best management tool
would probably result from a combination of the two models. Model
development and field evaluation should continue.
The concept of temporarily storing salt in the soil profile appears to
have merit. Timing of irrigations was tested as a management variable
and found to have a significant effect upon water and salt movements.
With all other conditions the same, the model predicts that as the
frequency of irrigation decreases (time interval between irrigations
increases), the season totals of salt removed from the soil profile,
salt remaining in the profile, and water required for leaching tend to
level off. That is, there is a fairly wide range of irrigation frequencies
which would be practical to use in the field which do not change seasonal
totals to any significant extent. However, the irrigation frequency has
an important effect upon when during the season the salt is removed
from the soil profile. Under conditions tested, the less frequent
irrigation tend to release salt earlier in the season. The above
results were obtained by not allowing the electrical conductivity of
the soil water to exceed certain constraints.
The results indicate that control over quality of soil profile effluent
will require precise control of water on the farm, particularly the
depth and timing of irrigations. Some of the costs of establishing
adequate systems could result in benefits other than increased control
of water quality. Not the least of such benefits could be increased
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yield and quality of crops. To maintain the control over return flow
quality which might be gained in the soil profile once the water enters
the saturated zone, sophisticated drainage systems may also be
required.
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SECTION II
R E C OMME NDAT IONS
It is recommended that the models should be further developed and
field tested to arrive at a practical model which can serve as a tool
for irrigation management with the objective of return flow quality
control. The field testing should include the water table depth and
irrigation water quality as variables. It is recommended that this
work first be continued on the Hullinger farm. Later it will be
necessary to test the models against data from other locations having
different field conditions including different crops, soils, climate, etc.
Initial efforts to improve the simplified model should be concentrated
on adequately estimating the movement of water since water is the
transporting medium for the salt. Of primary concern is the incap-
ability of the model to account for upward flow of water from the
saturated zone. Redistribution of moisture should also be considered
to compensate for variation in moisture extraction from different
soil layers and for situations when insufficient irrigation water is
applied to bring all layers to the upper limit of field moisture. Once
the water flow has been accurately described, there is hope for pre-
dicting salt movement, whether an empirical method is used or whether
an attempt is made to describe in detail the chemical processes
involved.
The simplified model predictions of salt movement were shown to be
significantly greater than indicated by the field measurements. This
implies that the leaching factor function did not provide an adequate
means of simulating salt movement. Sources of error could be the
method of laboratory measurement or the development of the leaching
factor function from laboratory data. Rate of application of water to
the disturbed soil columns in the laboratory ranged from 1.1 to 2. 3
inches per hour, as compared with the irrigation application rate on
the field experimental plots of 0. 25 inches per hour. The development
of the leaching factor function included extrapolation to regions of much
higher initial moisture contents than were studied in the laboratory.
•Only initial volumetric moisture contents of 0. 05, 0. 15, and 0. 20
were used in the laboratory to arrive at leaching factors for various
effluent ratios. Measured field moisture contents used as initial
conditions to test the model were often between 0. 30 and 0. 40.
-------
It is recommended that other approaches to obtaining the leaching
factor function be studied. One approach might be to use field measure-
ments of the electrical conductivity of the soil solution (EC ) to
s
indicate areas where undisturbed soil samples might be taken. The
undisturbed samples could be used in place of the disturbed soil
columns to determine the leaching factor. The EC of the samples
s
could cover the range that would be expected in the field. When
calibrating the soil, initial moisture content and all other conditions
should be as close as possible to conditions in the area to which the
model is to be applied. Another approach may be to make use of the
detailed model (requiring large amounts of information as input) to
determine a leaching factor function. Although the detailed model
itself may be of limited value from a management standpoint, because
of excessive amount of computer time required, it might serve to
calibrate the soil in an area of interest. The simplified model could
then be used to schedule irrigation according to predicted salt and
water conditions.
The detailed model provides a basic framework for solving problems
that involve water quality and quantity in irrigation return flow, since
salt movement in the soil depends primarily on water movement.
Moreover, development of the model provides a basic step in irrigation
water management, as to how much and when to irrigate.
Some of the weaknesses of this model are that it did not consider
hysteresis or layered soil although both of these have been considered
earlier. Further assumptions were that the soil properties did not
change with time. Moreover, this model requires some assumption
regarding the partitioning of potential evapotranspiration into potential
transpiration and potential evaporation directly from the soil. At
present, this partition is done rather crudely based on an estimate of
percent of cover of the plant.
Therefore, further research for the development of this program
should be pursued. The recommended research is: 1. Development
of the program to account for the variation of soil and climate para-
meters with time, therefore increasing the accuracy of computed
values. 2. Simplifications of the model to reduce computer time and
input data needed since the accuracy of the computed values is fair
enough for many practical purposes.
Since the detailed model was not tested under a variety of initial and
boundary conditions for salt flow, it should be further investigated in
-------
the field and laboratory to determine its suitability. In addition, there
appears to be at least five related areas where more investigation is
needed to improve and test this model. They are:
1. What is the effect of "built in" dispersion in numerical
methods on the salt flow?
2. How do the activity coefficients of different ionic species
vary at high salt concentration in soil solutions?
3. How do the exchange coefficients behave in the mixed salt
solutions at high salt concentrations?
4. What is the correction due to other complex ion formations
at high salt concentrations?
5. Because it was concluded that powdered salt does not
dissolve immediately after wetting under unsaturated flow
conditions, it is recommended that salt solutions rather
than salt crystals should be used in field studies.
The basis for using the soil profile as a salt storage reservoir is the
concept that crops can tolerate higher concentrations of salt in the soil
water where the roots are less dense. The effects upon plant physiology
and crop yields of salt distribution in the root zone need to be more
accurately defined. Results of such studies could provide reasonable
concentration constraints for various parts of the root zone to be used
in the models. It is probable that some situations may require the
incorporation of a time dependent root development and extraction
pattern into the models.
Economics of irrigation management should be studied in considerable
detail recognizing benefits other than control of return flow quality.
Flow of water and salt in the saturated zone within the groundwater
needs to be evaluated if valley wide salinity control is to be practical.
Effects of both man-made and natural drainage must be considered.
Such studies are necessary before benefits from irrigation scheduling
on a district or valley wide basis can be determined. Another defi-
ciency involves data collection under field condition. Many uncertain-
ties in measured data made a full evaluation of the model difficult.
Methods for obtaining more reliable data should be developed. More
reliable methods for determining the electrical conductivity of the
soil solution in the field are required. Alternatives are solution ex-
traction or in-place salinity sensors. Extraction of a sufficiently
large volume of solution was a problem in this study. Probes for
-------
field measurement of salinity tested in this study did not perform sat-
isfactorily under field conditions.
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SECTION III
INTRODUCTION
The recent (February, 1972) session of the Federal-State Enforcement
Conference on the Colorado River held in Las Vegas, Nevada, re-
emphasized the problem of salinity in the Colorado River Basin. The
considerations of the session were based mainly upon a report by
Regions VIII and IX of the United States Environmental Protection
Agency (1971) entitled "The Mineral Quality Problem in the Colorado
River Basin. " Included in the conclusions of the report are the
following:
1. Salinity (total dissolved solids) is the most serious water
quality problem in the Colorado River Basin.
2. Salinity concentrations in the Colorado River system are
affected by two basic processes:
(a) salt loading, the addition of mineral salts from various
natural and man-made sources; and
(b) salt concentrating, the loss of water from the system
through evaporation, transpiration, and out-of-Basin
export.
3. Salinity control in the Colorado River Basin may be accom-
plished by the alternatives of:
(a) augmentation of Basin water supply;
(b) reduction of salt loads (including improvement of
irrigation and drainage practices);
(c) limitation of further depletion of Basin water supply.
This report deals with the possibility for controlling the quality of
irrigation return flow by proper management of the application of
irrigation water. Such management depends upon knowledge of water
and salt movement through the root zone of the crops. Return flow
of water to streams from irrigation water applied to fields is profoundly
influenced by the soil through which it flows. There is, first of all a
very large decrease in the amount of the irrigation water appearing as
return flow because of return to the atmosphere as a vapor during the
evapotranspiration process. Decrease in water may be complete but
commonly ranges from 90 to about 50 percent of the irrigation applied.
Since soluble salts are mostly excluded from plant uptake and are left
behind in the soil during evaporation, there is a concentrating effect of
the salts in the solution drained from a soil compared to the solution
concentration entering. The water draining from the soils may be so
-------
high in salts that its further use is severely limited—a serious problem
in the Colorado River Basin. In addition, the natural weathering of
soils with precipitation, solution and exchange of constituents in the soil
solution with the solid soil particles further influences the concentration
of the soil solution. Further complicating the picture is the time delay,
amounting to storage, in movement of constituents in the soil water
from one part of the soil to another.
Irrigation return flow quality is affected in many segments of the
water's path from diversion until its return to the stream, lake, or
groundwater. This report considers the possibility for influencing
return flow quality within the root zone of crops. The other segments
of the water path were not included in the study. All segments would
need to o>i considered to assess the full impact of any proposed control
measure.
Objectives
Before it is possible to develop rational management procedures, taking
into account the quality of the irrigation return flow, it is necessary to
be able to describe the major aspects of the system. It was the purpose
of this research to develop and field test rational models for predicting
the salt and water status within the soil between the time of entry as
irrigation water and the time of departure as drainage water, or eva-
poration from the soil, or transpiration by the plant.
Specifically the objectives were:
1. To develop a model to be used as a tool for irrigation manage-
ment encompassing the factors having a significant effect
on the quality of irrigation return flow.
2. To develop a model for prediction of the simultaneous flow
of salt and water in a soil subject to irrigation. For purposes
of implementation the objective was broken down into two
parts:
(a) to develop and field test a model for estimating soil
water flow subject to natural precipitation, irrigation,
root extraction and transpiration by plants, evaporation
of water directly from the soil and drainage;
(b) to develop and field test a model for predicting salt
distribution in the soil and drainage water under irrigated
field conditions.
8
-------
Organization of Research
The research to meet the stated objectives was conducted in several
parts. The model development proceeded with a two-pronged approach
resulting in the "simplified" and "detailed" models explained in the
report. The simplified model was intended to provide a tool for irri-
gation management. It was formulated to require a small amount of
computer time and a minimum of field data as input and to allow con-
sideration of a wide range of variation of factors affecting the quality
of irrigation return flow. It was expected that the model would predict
gross effects rather than detailed ones. On the other hand, the main
purpose of the detailed model was to understand the specifics of simul-
taneous water and salt flow through the crop root zones. The detailed
model was based more closely on known physical principles and laws
governing water movement through partially saturated soils.
Both models were tested against data measured in the field during the
irrigation season. The field data were collected on the Hullinger
farm near Vernal, Utah. About 35 acres of the farm were operated
specifically for the quality of irrigation return flow studies.
Laboratory work was needed to test some modeling concepts as well
as to analyze the samples taken in the field. Examples of laboratory
studies were the determination of the leaching factor function for the
simplified model and the soil characteristics for the detailed model.
It was necessary to conduct laboratory column studies to aid in eval-
uation of salt movement description capabilities of the detailed model.
-------
SECTION IV
REVIEW OF LITERATURE
A current approach to the field soil water cycle is based on recognition
that the field and all its components--soil, plant, and atmosphere
taken together — form a physically unified and dynamic system (Gardner,
i960; Cowan, 1965) in which various flow processes occur sequentially
like links in a chain. This unified system has been called "SPAC"
(for "soil-plant-atmosphere-continuum") by J. R. Philip (1966). In
this system, flow takes place from higher to lower potential, with the
concept "water potential" equally valid and applicable in soil, plant,
and atmosphere alike.
To characterize the SPAC physically, therefore, it is necessary to
evaluate the potential of water and its change with distance and time
along the entire path of water movement (Hillel, 1971). The flow rate
is everywhere inversely proportional to an appropriate resistance.
The flow path includes the water movement in the soil toward the roots,
absorption into the roots, transport in the roots to the steins through
the xylem to the leaves, evaporation in the intercellular air spaces
of the leaves, vapor-diffusion through the stomatal cavities and openings
to the quiescent air layer in contact with the leaf surface and through
it to the turbulent boundary layer, whence the vapor is finally trans-
ported to the external atmosphere.
Soil water flow to plant root has been studied by a number of investi-
gators. The studies of Philip (1957), Gardner (I960), and Molz et al.
(1968) consider the radial flow of water to a single root. However,
other studies (Ogata, Richards, and Gardner, I960; Gardner; 1964;
Whistler, Klute, and Millington, 1968; Molz and Remson, 1970, 1971;
and Molz, 1971) deal with the removal of moisture by the root zone
as a whole without considering explicitly the effects of individual roots.
For convenience, the term "microscopic" is used for the flow process
in the vicinity of a single root, and "macroscopic" for the overall
moisture extraction process in an entire root zone.
Models for Root Extraction
Soil water potential decreases as soil water content decreases. The
soil will deliver water to the root as long as the water potential in the
root is maintained less than in the soil. However, as a root extracts
water from the soil in contact with it, the water potential in the soil
11
-------
contact zone may decrease, as well as the hydraulic conductivity.
Water uptake may decrease, assuming the root water potential stays
constant, unless additional water can move in from the farther reaches
of the soil in direct contact with the root. In order for this additional
water to become available to the plant, not only must the soil water
potential be greater than the root water potential, but the hydraulic
conductivity of the soil must be large enough so that water will move
toward and into the root at a rate sufficient to compensate the plant for
its own loss of water to the atmosphere by transpiration.
These principles have been applied on both a microscopic and macro-
scopic scale. These two approaches will now be discussed in detail.
Microscopic Approach or Single Root Model
In this approach the details of the flow about a single root are examined.
On the assumption that a typical root can be represented by an infinitely
long, narrow cylinder of constant radius and water-absorbing charac-
teristic (effectively a line sink), and that soil water movement toward
the root is radial, the appropriate form of the flow equation is:
08 1 o
ot ~ r or
where Q is volumetric soil water content, D is diffusivity, t is time,
and r is radial distance from the axis of the root. Assuming constant
flux at the surface, Gardner (I960) solved this equation subject to the
following initial and boundary conditions:
q = ZiraK^r- = ZiraD^- r = a, t >0 [2]
or or
where a is the root radius, h is matric potential, K is hydraulic con-
ductivity, and q is the rate of water uptake by the root or the flux of
water at the root surface expressed as volume of water per unit length
of root per unit time. The solution of Equation [l] subject to Equation
[2] for constant D and K and sufficiently long time is:
12
-------
h - ho = Ah =
ln
4Dt
2
r /
[3]
where y is Euler's constant = 0. 57722 ... . From this equation, it
is possible to calculate the gradient Ah that will develop at any time
between the soil at a distance (r - a) from the root (i. e. , the initial
soil water potential h ) and the matric potential h at the root-to-soil
contact zone. Since diffusivity, time, and radius at the root occur in
a logarithmic term in Equation [3], Ah is much less sensitive to these
three factors than to q and K. Gardner (i960) showed that a ten
thousandfold variation in D would cause only about a ninefold variation
in Ah, hence the assumption of an average constant value of D does
not introduce a serious error. Similarly, Gardner showed that root
size is not extremely important; the root diameter should be important
only when resistance to water entry in the root is large compared with
resistance to water movement in the soil. This is probably the case
only in wet soils. Moreover, the variation in K, due to Ah, was
considered to be no larger than the uncertainties in determination of
K, so that the assumption of a constant K was valid for not too large K.
Equation [3] shows that the gradient Ah, or the increase of soil water
potential above the initial value, is directly proportional to the rate of
water uptake and inversely proportional to the hydraulic conductivity of
the soil. The root water potential can, therefore, be expected to depend
on these two factors as well as on the average soil water potential.
Hence, when soil water potential is high and conductivity high, Ah is
small and the potential in the root will not differ markedly from the
potential in the soil. When soil water potential decreases and soil
hydraulic conductivity decreases, the potential difference (or gradient)
needed to maintain the same flow rate must increase correspondingly.
As long as the transpiration of the plant is not too high, and as long
as the hydraulic conductivity of the soil is adequate and the density of
the roots is sufficient, the plant can extract water from the soil at the
rate needed to maintain normal activity. However, the moment the
rate of extraction drops below the rate of transpiration (either because
of high evaporative demand by the atmosphere, and/or because of low
soil conductivity, and/or because the root system is too sparse), the
plant necessarily loses water, and if it cannot adjust its root water
potential or its root density so as to increase the rate of soil water
uptake, the plant may suffer from loss of turgor. This situation will
sooner or later cause the plant to wilt.
13
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Limitations of the Microscopic Approach
The limitations of the microscopic approach are:
1. The diffusivity, D, and hydraulic conductivity, K, of the soil
were assumed constant (Gardner, I960), while they change
as soil water and salt concentration change with time and
depth.
2. The model has been based on the assumption that the roots
are uniformly distributed in the rooting zone, and that the
average soil water potential is similarly uniform within the
rooting zone (Gardner, I960; Molz et al. , 1968). In actual
fact, root systems in the field are seldom, if ever, uniform
with depth.
3. Another limitation of the microscopic approach is the deter-
mination of the correct boundary condition at the root surface.
Most authors have used either a constant flux condition
(Gardner, I960) or a constant head condition (Molz et al. ,
1968). The correct condition would probably be some com-
bination of both that varied temporally (Molz and Remson,
1970). Moreover, if an attempt is made to treat realistic-
ally more than one root at a time, it becomes very difficult
to specify the geometry correctly. An added difficulty is
measuring the necessary variables with macroscopic in-
struments.
Based on the microscopic approach, the usual method for studying the
composite soil-plant system has been to consider flow to a single
"typical root. " The results are then multiplied by an "average" root
density to obtain generalizations concerning the entire root-plant
system (Gardner, I960; Cowan, 1965).
Macroscopic Approach or Bulk Root Model
In this model the flow to individual roots is ignored and the overall
root system is assumed to extract moisture from each differential
volume of the root zone at some rate. At a given point, this rate
can depend on position in a coordinate system, water content, soil
conductivity, time, etc. The water-removing roots may then be
represented as an extraction (sink) term in the soil water flow equation.
Ogata, Richards, and Gardner (I960); Gardner (1964); Whistler et al.
,(1968); Molz and Remson (1970, 1971); and Molz (1971) have considered
14
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the macroscopic approach. Gardner (1964) modified Equation [3] from
a single root system to an entire root system:
W = (h . - h .J/R [4]
plant soil
•where W is the rate of water uptake per unit volume of soil, h , is
plant
water potential within the plant root, h is the total water potential
in the soil, and R is the resistance to water movement in the soil, R ,
s
and the plant, R . In specifying R, one can assume that the soil and
P
the plant resistance can be added in series so that R = R + R . Gardner
p s
and Ehlig (1962) suggested that R may be small compared to R ; there-
p s
fore, it is assumed to be negligible. According to this, Gardner (1964)
assumed that the water potential is uniform throughout the entire root
system at any one time. On the other hand, Molz and Remson (1970)
devised an extraction term that depended only on depth and transpiration
rate. They used an empirical rule, given by Danielson (1967) that
40 percent, 30 percent, 20 percent, and 10 percent of the total trans-
piration requirements comes from each successively deeper quarter
of the root zone. Molz and Remson (1970) considered these numbers
40, 30, 20, and 10 of no special significance but they regarded them as
"reasonable" quantities to write their root extraction term:
c.i * • !• 8T ^ rn
S(z) =- - = — + - 0< z < v [5]
where S(z) is the water extraction rate per unit volume of soil, z is
the vertical distance positive downward, v is the vertical length of
the root system, T is the transpiration rate per unit area of soil sur-
face. In some cases, T is interpreted as an "average" transpiration
rate.
The total water extraction rate from a volume of soil of unit cross
section bounded by the horizontal planes z = z and z = z where
J. w
z < z is:
1 ^
Z2
S(z)dz [6]
15
-------
Because the extraction rate from the root zone equals the transpiration
rate, then:
T =
S(z)dz = -
1. 6T
l.STz
0
[7]
It can be verified that Equation [5] meets the stated percentage require-
ments by integrating over the appropriate portions of the root zone. To
account for root systems that are growing so that v = v(t), Molz and
Remson (1970) generalized Equation [5] to:
, .,
(z, t) = -
. 6Tz
-
(v(t)f
+
rol
[8]
Combining Equation [8] with the general flow equation in one dimension,
and assuming steady state conditions, they obtained the partial differen-
tial equation:
- (az-b)
[9]
where D is diffusivity, D= K dh/B9, h is matric potential, 9 is volum-
etric water content, a = - 1. 6T/v , and b = 1. 8T/v. Equation [9] was
applied to the data from an experiment of Gardner and Ehlig (1962) and
yielded reasonable results.
Limitations of the Macroscopic Approach
The macroscopic approach has been studied under controlled experi-
ments, but it has not been widely used and knowledge of its utility and
behavior is limited under field conditions. Other limitations of the
macroscopic models that have been studied are:
1. A uniform root distribution and water potential were assumed
throughout the root system at any one time (Gardner, 1964).
These assumptions rarely exist under field conditions. It
was also assumed that the plant resistance to water movement
was negligible compared to the soil resistance to water
movement (Gardner, 1964), but roots are not uniformly per-
meable to moisture (Slayter, I960).
16
-------
2. Steady state was assumed to solve the model (Whistler, Klute
and Millington, 1968; Molz and Remson, 1970). Steady state
rarely occurs in the field.
3. A constant "average" transpiration rate and an initial uniform
moisture content of approximately field capacity were used
to solve the macroscopic model by Molz and Remson (1970
and 1971) and Molz (1971) utilizing controlled column exper-
imental data collected by Gardner and Ehlig (1962) and
Gardner (1964).
Moreover, extraction models such as Equations [5] and [8] may give
reasonable qualitative results for higher moisture contents, but it is
doubtful if they will agree in detail with experimental results. One
reason for this is that as the upper layers of soil dry, more of the
transpiration requirements comes from deeper roots in the wetter
soil (van Bavel, Stirk, and Brust, 1968). This is not accounted for in
Equations [5] and [8]. However, for a steady state, the moisture
extraction pattern is static and models such as Equations [8] and [9]
can yield reasonable results (Molz and Remson, 1970).
The macroscopic approach has significant advantages over the micro-
scopic approach. The geometry for a one-dimensional model is quite
simple. The boundary conditions are easy to identify and apply com-
pared with those that occur at the root surface in the microscopic
treatment. The upper boundary conditions are usually taken at the soil
surface; thus evaporation, rainfall, or zero flow conditions can be
accounted for. The lower boundary might be an impermeable layer or
water table. Moreover, any results obtained from the macroscopic
model apply directly to the SPAC as a whole.
Column Chromatography
Most of the models developed for tracing salt distribution in soils are
based on the laws of conservation of mass. They state that the amount
of salt added by water applied to the soil layers, minus the amount leached
out and the amount absorbed by plants is equal to the net increment
(positive or negative) of salts in the soil layer.
Any attempt to gather information on the vertical transport of different
ions or salt solutions through the soil results in a mass of chromato-
graphic theories. Two different approaches can be defined in the
literature. The first one is based on the kinetic process called the
17
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"rate theory" (DeVault, 1943; Hiester and Vermeulen, 1952; and Lap-
idus and Amundson, 1952). The second one is the plate theory of
Glueckauf (1949), Thornthwaite, Mather, and Nakamura (i960), Dutt
et al. (1971), and Bresler (1967) in which the height of a plate in the
column is the unit of calculation. Historical development of the two
different schools of thought will be reviewed separately in the following
sections.
Rate Theory
One of the simplest rate theories is that of. De Vault (1943). It is
also described as the equilibrium chromatography. It requires that
the penetrating solution move through the porous medium at such a
rate that a dynamic equilibrium between the ions in solution and adsorbed
phase shall be maintained. The theory starts with a material balance
over a cross sectional layer of the column of thickness dz:
dc dc dE
r~ + a ^~ + ~
oz dv
where c is the concentration of solute in the solution phase, E is the
concentration of solute in the solid phase, z is the distance from the
top of the column, a is the pore or void fraction of the column and v is
the volume of the solution fed to the column. Under saturated flow the
general solution of this equation is
where is the amount of adsorber per unit of length, f ' (c) is the
derivative of f(c) with respect to c, f (c) is the adsorption isotherm
defined in such a way the E = 4*f(c) and g(c) is any function determined
by the initial distribution of solute through the column.
Rible and Davis (1955) applied this theory with some success to predict
ion distribution in soils. The theory is less involved mathematically
but is limited in application to soil because of the assumption of
instantaneous equilibrium and negligible channeling.
Hiester and Vermeulen (1952) started with another material balance
equation:
18
-------
__
c)u
V
ov /u
u
[12]
where u is the bulk packed volume of the column (ua ~ void volume)
up to point z. Their work was the extension of work started by Thomas
(1944) who took account of the rate of exchange by second order kinetics.
The starting point is
+ BX
B + AX
[13]
and the rate equation being
If
- E> - T
-------
applied. Gardner and Brooks (1957) distinguished between immobile
and mobile salt moving with the same velocity as the leaching front.
They adopted and tested the theory of Hiester and Vermeulen (1952) in
laboratory column and field plots of Pachappa sandy loam. Agreement
between the predicted and experimental values was found to be satis-
factory.
The model of Hiester and Vermeulen differs from the proceeding model
of De Vault in that rate dependent processes are considered in lieu of
the assumption of equilibrium. However, both the models ignore the
dispersion of salts.
The third model that is based on kinetics rs by Lapidus and Amundson
(1952). They have developed a model which takes into account the
dispersion in addition to the mass flow. Previous work of Nielsen and
Biggar (1962) has shown this model as the most satisfactory of all
models investigated for predicting the spreading of a non- interacting
solute, in porous media, where spreading results from diffusion and
dispersion. When exchange is also considered the material balance
over a layer dz is,
, 2 ~ az dt a
oz
where D is the dispersion coefficient. Depending upon the boundary
conditions, the equation can be solved analytically (Nielsen and Biggar,
1962) or numerically (Lai, 1970). Some of the assumptions implied
in the above model are that the velocity profile can be represented by
an average v, the diffusion coefficient is constant, equilibrium between
the two phases is established and there exists some relationship between
the ions in solution and the exchanger. A comparative study of three
models, De Vault (1943), Hiester and Vermeulen (1952), and Lapidus
and Amundson (1952) was reported by Biggar and Nielsen (1963) using
Oakley sand. They concluded that all the theories were generally
inadequate to describe the experimental values. The lack of agreement
was attributed to the inadequate description of exchange, the use of the
average value of the flow velocity and the diffusion coefficient.
Plate Theory
In the plate theories the column is regarded as being divided into a
large number of segments or plates. Within each plate the concentration
20
-------
is considered to be uniform both in sorbent and liquid phases, the two
concentrations being assumed to be at equilibrium. It is immaterial
whether an exchange process, diffusion process, or any other process is
envisaged as the main dispersion process. It is also implied that
there is only one unit of length to which this definition applies. If the
height of the plate is too long, the concentration may not be regarded
as uniform and if it is too short no equilibrium is possible between the
two concentrations.
One of the plate theories that has been extensively tested in the soil
system is that of Glueckauf (1949). The starting equation is,
df(c)
d
A
2
= 0
[18]
where A is the plate height. In 1956, van der Molen applied this theory
to the desalinization of soils under the influence of Dutch climate (mean
annual precipitation about 70 cm). The solution of Equation [18] for a
homogeneous saline profile at large values of N and in the case of a
linear adsorption isotherm, may be represented by
[19]
where N is the number of depths above a distance z, p = v/crpd,
si
erfc
i 2 f *
n = 1 - — \
TT Jo
-U
e du, p is the density of the soil, and d is the
distance from the soil surface. Some general agreement was found in
theoretical and observed values. Dyer (1965) studied the distribution
of chloride and nitrate ions in adjacent irrigated and non-irrigated areas
and observed a close fit of theoretical values with the observed ones.
Finally, there are two other very practical theories that have never-
theless retained the characteristics of chromatographic transport.
Both the theories consider the fixed plate height. Thornthwaite et al.
(1960) and Frissel and Poelstra (1964) have described the transport of
strontium through soils. Their method is based on Martin and Synge
(1941) theory except that the plate height is fixed and it is assumed that
0. 1 part of Sr in each layer is leached downward to the next layer, for
21
-------
every unit of the leaching solution added to the soil. If at the beginning
of leaching only one layer is loaded, the concentration in the nth layer
c is found from
n
c =
n
t'l(0.1)n-1(0.9)t'-n
(f - n+l)!(n - 1)!
[20]
where c is the total concentration in the first layer and t1 is the number
o
of leaching cycles.
The other approach which has received widespread attention is by Dutt
(1963) and his co-workers. He has used a method for calculating the
quality of water percolating through soil containing gypsum. The
concentration of salts at any depth and time is given by
cj.=
(es - e°\
es.
+ c.
'9°
i
es.
[21]
where i and j are depth and time, respectively. 6 is the moisture con-
tent and 9S. is pore volume at any depth, c. is then corrected for
solubility of minerals and exchange with the soil.
The advantage of this type of approach is that it is possible to introduce
such factors as solubility of minerals, etc. Since exchange constants
are used it means no linear adsorption isotherm is necessary. The
main drawbacks of Dutt's (1963) model are that the process is discontin-
uous and unknown dispersion is present even when physical dispersion
is ignored in the model.
Review of the different models applied to the soil for describing the
movement of salt are discussed by Frissel et al. (1967) and Biggar and
Nielsen (1963). For the most part previous investigators have used
constant flow velocities. A notable exception is the work of Bresler
and Hanks (1969) who describe the numerical technique for simultaneous
flow of water and salt in unsaturated soils and allow for time dependent
velocities. This work was essentially a combination of Bresler's
(1967) model for salt flow, and Hanks and Bower's (1962) model for
water flow. The model starts with a material balance equation
22
-------
d(6c)
9D
(vc)
+ S
[22]
where v is the volumetric flux of water given by Darcy's law, t is the
time, S is the sink or source term due to the solubility of mineral or
exchange between solid and solution phase. Equation [22] is similar
to the equation given by Lapidus and Amundson (1952). The present
model of Bresler and Hanks (1969) contains the important features of
rate as well as plate theory. The plate height is variable with depth
but is constant with time. The model ignored the dispersion and sink
or source term. However, a critical examination of the numerical
method indicates a tendency for the concentration profile to spread for
noninteracting salts rather than have a sharp profile, thus indicating a
"built in" dispersion in numerical approximation like Dutt (1963). The
model has been tested in the laboratory and gave values which agreed well
with the experimental results.
23
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SECTION V
DEVELOPMENT OF MODELS
A very important aspect of water quality in rivers of arid regions is
salinity (total dissolved solids). Since irrigation return flow constitutes
a large part of the influent to such rivers, control of the salinity of
irrigation return flow is vital to any program of salinity control in a
river basin. Irrigation practices can greatly affect the quality of
irrigation return flow. Proper management of the application of irri-
gation water depends upon knowledge of water and salt movement through
the root zone of the crops. Two different models were developed for
describing flow of water and salt through the soil with extraction of
water by evapotranspiration. The two are called "simplified" and
"detailed" models for the purposes of this report. The development
of each model is outlined in the following.
Simplified Model
The simplified model was developed to serve as a tool for irrigation
management. It was formulated to require a small amount of computer
time and a minimum of field data as input and to allow consideration of
a wide range of factors affecting the quality of irrigation return flow.
The simplified model was designed to predict gross effects rather than
detailed ones.
Two separate versions of the simplified model were developed. The
two are called "prediction" and "evaluation" versions according to
the general philosophy of their use. The evaluation version uses a pre-
determined irrigation schedule, specifying the timing, depth and quality
of water applied for each irrigation, to determine the effects of the
schedule upon quality and quantity of water entering the saturated zone
and upon the salinity status within the unsaturated soil profile. The
prediction version differs in that it determines the proper depth of
water to be applied in each irrigation so that the concentration of salts
in the soil moisture does not exceed a preset value. The details of the
prediction version of the simplified model will be given first.
Prediction Version
The prediction version of the simplified model is based upon the concept
of temporarily storing salt in the soil profile and leaching only when
25
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necessary to prevent the salt from becoming too concentrated in the
soil moisture. The unsaturated zone is divided into "n" layers of equal
thickness. A constraint is set on the allowable concentration in each
layer. The calculation begins by adding to the top layer sufficient
water to fill the available soil water reservoir for the entire unsaturated
zone. The computer program calculates the movement of water and
salt from layer to layer through the profile. If the concentration con-
straint of any layer is exceeded, then the computer program iterates
by adding more water until the constraint is satisfied. After the proper
depth of water to be applied in a given irrigation has been determined,
the final conditions existing in the profile (after passing of the time in-
terval between irrigations) become the initial conditions for the next
irrigation. Thus, the entire irrigation season is covered in one compu-
ter run.
The crop is assumed to extract pure water leaving the salt behind in
the soil moisture. The water and salt are assumed to move downward
through the soil — lateral and upward movement are not allowed. The
model uses an "upper limit of field moisture" concept i. e. , after an
irrigation, downward drainage of water occurs until the soil reaches
the upper limit of field moisture, after which all downward movement
of water ceases. The upper limit of field moisture must be determined
for each soil layer under conditions to be encountered in the field. For
layers near and including the water table, the upper limit will be the
saturated moisture content.
Figure 1 shows a typical layer of soil with the symbols as follows:
DX is the thickness of the layer.
ET is the total depth of water extracted from the layer by
evapotranspiration.
d is the depth of water entering the layer.
e
9 is the initial volumetric moisture content of the layer.
o
9 is the volumetric moisture content when the soil contains
the upper limit of field moisture.
9 is the final volumetric moisture content existing in the layer
at the end of the irrigation interval.
d is the depth of water leaving the layer.
C , C , C, , C., and C , denote the corresponding concentration
e o f m f 1
of salt in the water.
26
-------
A
x
o
e
_v
cf
m
Cf
ef
-~1 I
..J
d
Figure 1. Typical layer of soil in simplified model.
27
-------
The movement of water is treated in a fairly simple manner. Since
drainage from a particular layer ceases when the soil reaches the upper
limit of field moisture, the depth of water leaving the layer is equal to
the depth entering minus the depth required to bring the soil layer to the
upper limit. Thus, in equation form
d. = d - DX (9. - 9 ) [23]
1 e fm o
After the soil layer reaches the upper limit of field moisture, the only
loss of water from the layer is by evapotranspiration. This version of
the model assumes that the minimum amount of water applied is that
required to bring each soil layer to the upper limit of the field moisture.
Thus, the final moisture content of the layer is determined from the
difference between the amount of water at the upper limit and the amount
extracted by evapotranspiration for the period between irrigations. In
equation form, the final moisture content is given by
9,. = 9r - ET/DX [24]
f fm
The movement of salt is more difficult to describe. A mass balance
on salt of any layer can be written as
C d + C d = C.d, + C, d, [25]
e e o o 11 fm fm
in which d and d. are depth of water corresponding to 9 and 9 ,
o fm o im
respectively, i. e. , d = DX 9 and d = DX9 . Since it is
assumed that evapotranspiration removes salt-free water from the layer,
the mass of salt in the layer does not change as the moisture content is
reduced from 9 to 9 „; however, the salt becomes more concentrated
fm f
in the water remaining in the layer (C > C ). In other words
C d = C^d and Equation [25] can be written
fm fm f f
C d + C d = C d. + C.d. [26]
ee oo 11 ff
28
-------
All terms in Equation [26], except C and C , are known or can be
determined. The final concentration, C , is not allowed to become
greater than a certain value (concentration constraint) and can be
solved for only if C is known.
Using soil samples from the field, a laboratory method of calibrating
the soil to estimate C was developed (Rasheed, 1970; Titavunno,
1971). Details of this calibration are given later in this report in the
section entitled "Testing of Models". This calibration technique was
based upon a leaching factor, LF, defined as
LF = C_
-------
Table 1. Summary of results from laboratory technique of soil
calibration to determine leaching factor (LF) for Hullinger
farm soil.
Effluent
Ratio
(ER)
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.25
1.50
1.75
2.00
2.25
2.50
2.75
3.00
Leaching Factor (LF)
6 =0.05
o
0.201
0.275
0.303
0.365
0.412
0.432
0.461
0.495
0.520
0.541
0.586
0.633
0.681
0.719
0.741
0.763
0.787
0.798
8 =0.15
0
0.118
0.192
0.261
0.312
0.359
0.393
0.441
0.461
0.485
0.519
0.572
0.621
0.662
0.702
0.733
0.757
0.771
0.793
9 =0.20
o
0.084
0.143
0.195
0. 272
0.303
0. 353
0.394
0.422
0.462
0.483
0.553
0.606
0.652
0.681
0.713
0.735
0.762
0.776
ER = Effluent Ratio = d./d.
1 fm
30
-------
3. The number of irrigation intervals is computed.
4. If time has elapsed between the field sampling (from which
initial conditions were established) and the first irrigation,
the moisture loss by ET in this period is accounted for and
the initial conditions are adjusted accordingly.
5. At the time of the first irrigation, the depth of water necessary
to fill all layers of the soil profile to the upper limit of field
moisture (9 ) is calculated. This depth of water is used as
im
a first trial for the depth of water to be applied as the first
irrigation.
6. The depth of water computed in Step 5 is set equal to d for
the top layer of the soil profile.
7. The depth leaving the layer is computed from Equation [23].
8. The effluent ratio (d,/d,. ) and initial moisture content for
1 fm
the layer are used in the leaching factor function to obtain
the leaching factor (L.F).
9. The EC of the water leaving the layer is computed from
Equation [27] where it is assumed that the EC is a direct
measure of the concentration of salts in the water
(1 mmho/cm = 640 ppm): C = LF(C d + C d )/d.
1 oo eel
10. The EC at the upper limit of field capacity (C ) is calculated
from Equation [25], i. e.,
C, = (C d + C d - C.dJ/cL
fm e e o o 11 fm
11. The volumetric moisture content at the end of the irrigation
interval (immediately before the next irrigation), 9 , is
calculated from Equation [24] where ET denotes the depth of
water extracted from the particular soil layer by evapotrans-
piration during the interval of time following the irrigation.
12. The EC of the soil moisture at the end of the irrigation interval
(CJ is calculated from C^ = C, 9^ /9,.
f f fm fm f
13. If 9 is less than the wilting percentage, the problem is ter-
minated because the interval between irrigations is too long.
31
-------
14. A test is made to see if the concentration constraint for the
layer is satisfied. Let the upper limit of EC (concentration
constraint) be denoted as C and the iteration limit be denoted
C . Then if C < C + C, ,, d, and C, for the layer are set
tol f — t tol 11
equal to d and C for the next layer and calculation proceeds
e e
by returning to Step 7.
15. If C > C + C , the trial depth of water applied (Step 5)
is increased and calculations are repeated for the layer beginning
with Step 7. This iteration continues until a depth of applied
water is found by the method of false position (Kunz, 1957)
such that C - C < C < C + C ,. Then d, and C, for the
t tol — f — t tol 1 1
layer are set equal to d and C for the next layer and cal-
e e
culation proceeds by returning to Step 7.
16. Calculation continues until each layer of the profile success-
ively satisfies the concentration constraint. Then conditions
are re-initialized and the calculations are repeated for the
next irrigation.
17. Calculations continue until all irrigations of the season have
been 'considered.
18. i When one complete problem is finished the program auto-
matically proceeds to the next problem.
The output of the program is best illustrated by the two example pro-
blems included in the Appendix. The print control integer is used to
select either a long output (Example 1, Appendix A) or a short output
(Example 2, Appendix A). Both types of output include listings of all
the input data. The long output includes the salt existing, the moisture
content, and the EC of the soil moisture for each layer of soil immed-
iately prior to the first irrigation and after each irrigation interval.
Also given are the depth of water applied, the amount of salt leaving
the soil profile, the depth of leaching water, the leaching percentage,
and the ET for each irrigation interval and for the season. The short
output deletes the salt existing, the moisture content, and the EC of the
soil moisture for each layer after each irrigation interval.
The reader will note from the FORTRAN listing of the prediction version
(Appendix A) that as now formulated, the EC of the irrigation water
and the interval between irrigations are constant for the entire season.
32
-------
A simple program modification would allow these quantities to vary
through the season in some predetermined manner.
Evaluation Version
The main difference between the evaluation version and the prediction
version is that the depth of water to be applied for each irrigation is
specified as input to the evaluation version. That is, an irrigation
schedule specifying depth, timing, and EC of irrigation applications is
evaluated as to its effect upon the quality of water leaving the profile and
the salinity status within the profile. No constraint or limit is placed
on the EC of the soil moisture and the computations do not involve iter-
ation but are sequential from layer to layer and irrigation to irrigation.
In any irrigation interval, the calculation of conditions existing in the
profile on any given day is possible, and these conditions can be printed
out for comparison with field measurements. The program automatically
reinitializes using the calculated conditions and proceeds through the
season.
In the evaluation version, there may be situations where the applied
irrigation water is not enough to completely fill all layers of the soil
to the upper limit of field moisture. In such cases, the water is
assumed to fill each layer in succession beginning with the surface
layer. When a layer is reached where the water entering from the layer
above is not sufficient to fill the layer to 9 , all the water is assumed
to be retained in the layer; i. e. , the irrigation water does not penetrate
below this layer for this particular irrigation. For such a situation
the final moisture content is computed from
9 = 9 + d - ET/DX [28]
foe
Also, for this layer d < DX (9 - 9 ) and the layer fills to a moisture
e fm o
content equal to 9 + d /DX instead of 9r . If 6 =9 +d /DX and
o e f m a o e
d = DX9 , then Equation [25] becomes
a a
Cd +Cd = C d [29]
e e o o a a
And since C d = C d , Equation [29] is equivalent to Equation [26] where
cl cL x I
d. = 0. Since d is known and d, = 0, the leaching factor function is not
la 1
33
-------
needed for this layer and C can be calculated directly from Equation
[29].
This version of the simplified model is based upon the evaluation of an
irrigation schedule in which the depth, timing, and EC of applied water
are specified for each irrigation. The program is designed to allow
comparison of computer results with field measurements at any day of
the season. The season may be divided into a number of evaluation
periods including parts of (or all of) one or more irrigation intervals
and need not begin and end with the irrigation intervals. In one pass
through the computer, several evaluation periods can be considered at
one or mere field locations.
A FORTRAN listing of the computer program for the evaluation version
of the simplified model is given in Appendix A. A step-by-step de-
scription of the computer program for the evaluation version follows:
1. The input data are read. These data include the total number
of evaluation periods for the computer pass, and for each
evaluation period: the thickness of soil layers, a number
identifying the field location, a number identifying the eval-
uation period, the number of irrigations in the evaluation
period, the number of days from the beginning of the eval-
uation period to the first irrigation, the depth of water for
each irrigation, the EC of the applied water for each irrigation,
the length of each irrigation interval, the initial moisture
content of each layer, the initial EC of the moisture in each
layer, the moisture extraction pattern, the upper limit of
field moisture for each layer, the lower limit of moisture
(wilting percentage) of each layer, the maximum EC recom-
mended for each layer (comparison purposes only), the ET
for each day of the evaluation period. If the particular
evaluation period immediately follows a period already
calculated at the same location, the data of the above list
from the initial moisture content to the maximum EC rec-
ommended for each layer need not be given as input but are
already available internally.
2. The moisture content, EC of soil moisture, and amount of
salt for each layer immediately prior to the first irrigation
are calculated.
3. The depth of water required to fill the entire profile to the
upper limit of field moisture is calculated.
34
-------
4. The depth of water applied for the first irrigation is set
equal to d for the top layer.
6
5. The depth of water equivalent to the initial moisture content,
6 , and the upper limit of field moisture, 9 , are computed
o fm
from d = DX9 and d, = DX9,. .
o o fm fm
6. If d + d < d.. , all the water applied is retained in this
e o fm
layer and d = 0. The final moisture content of the layer is
computed from Equation [28] and the final EC of the layer is
computed from Equation [26] (with d = 0).
7. If d + d > d,. , the depth of water leaving the layer is
e o fm
calculated using Equation [23], Then, Steps 8 through 12,
inclusive, of the description of the prediction version are
followed.
8. If 9 is less than the wilting percentage, calculation proceeds
but an asterisk is printed after the value of 9 . If the final EC
of the layer is greater than the maximum EC recommended, an
asterisk is printed after the value of EC of the layer.
9. The d and EC of water leaving the layer are set equal to d
and EC of water entering the next layer and Steps 5 through
8 are repeated for the next layer.
10. After all layers have been considered the leaching water
and amount of salt leaving the bottom layer are computed.
11. The final conditions in the profile become the initial conditions
of the next irrigation interval and calculations are repeated until
all irrigations of the evaluation period are completed.
12. If data for another evaluation period follow, the entire calcu-
lation procedure is repeated.
The output of the program is illustrated by an example problem (Example
3, Appendix A). First, all of the input data is printed. This example
is for block 5 (field location) and has two evaluation periods. The
particular period is denoted by the second number following the word
"block". The value of C gives the EC of irrigation water applied, KM
denotes the number of days following the irrigation (irrigation interval),
and KM1 gives the number of days from the beginning of the evaluation
period to the first irrigation.
35
-------
Detailed Model
The purpose of the detailed model was to understand the specifics of
simultaneous water and salt flow through field soils. The detailed model
was designed to determine the salt and water content within the soil
and in the drainage water as a function of time and depth for saturated
and unsaturated soil water flow. Since the water is the transporting
medium for the salt, the development of the detailed model was handled
in two parts. The first part was the development of a "water model" to
describe soil water flow subject to natural precipitation, irrigation, root
extraction and transpiration by plants, evaporation of water directly
from the soil, and drainage. The second^part was the development of a
"salt model" to predict salt distribution in the soil and drainage water
under irrigated field conditions. The salt model is built upon the
water model as a foundation. The water model and the salt model are
described separately in the following.
Water Model
None of the previous models, discussed in the Review of Literature,
have been applied to field conditions. For these reasons, and in order
to encounter more variables as they exist under field conditions, a new
macroscopic approach has been developed and tested under field con-
ditions.
The bulk root model developed herein is a modification of the soil water
flow model of Hanks, Klute and Bresler (1969). The principal modifi-
cation involves the consideration of extraction by plant roots. The
general flow equation without root extraction for one dimension given
by Hanks, Klute and Bresler (1969) is:
o8 \j i „,«» '-'J-A r^Di
where 9 is volumetric water content, t is time, z is depth, K is hy-
draulic conductivity, H is hydraulic head (sum of pressure head, h,
and gravity head, z). The modification of the above equation by a
plant root extraction term, A(z), gives:
=
dt ~ dz
A(z) [31]
36
-------
A(z) is the root extraction term or the sink term and depends on the root
density function (the fraction of total active roots per unit volume of soil),
soil conductivity, and the difference between pressure potential of water
in the plant root and the pressure potential of soil water. Thus, the
source term is defined as:
A. [Hroot + (RRES • z) - h(z) - S(z)l • RDF(z) • K(z) r,?1
A(z) = LJ^J
Az
where Hroot is an effective water potential in the root at the soil
surface where z is considered zero, RRES = (1 + R ). R is a
c c
flow coefficient. When RRES is multiplied by z, the product will
account for the gravity term and friction loss in the root water poten-
tial, so that root water potential at depth z is higher than the root
water potential at the surface (Hroot) by a gravity term and friction
loss term, (assuming that the friction loss in the root is independent
of flow), h(z) is the soil matric potential at depth z, S(z) is the salt
(osmotic) potential at depth z, RDF(z) is the proportion of total active
roots in depth increment Az, and K(z) is the hydraulic conductivity
at depth z and it is a function of 9. The soil matric potential, h(z)
and the hydraulic conductivity, K(z) are assumed to be unique functions
of soil water content (hysteresis ignored). The validity of the assump-
tion that a unique relation of hydraulic conductivity to a volumetric
water content, K(9), exists is affected by hysteresis to a much lesser
degree than is the K(h) function (Topp and Miller, 1966; Poulovassilis,
I96v). The Hroot term is dependent on plant, climatic and soil
conditions. The value of Hroot will depend on plant conditions since
they govern the root distribution function, RDF(z). Hroot will depend
on climatic conditions since they define potential transpiration, dis-
cussed in detail later. The value of Hroot will depend on soil conditions
since h(z), K(z), S(z) will be soil properties (which will vary greatly
from wet to dry soil). In the model, a value of Hroot is "hunted" for
until the plant root extraction over the total profile is equal to potential
transpiration provided the value of Hroot is higher than the value of
plant water potential below which the plant will not go and thus wilting
will occur (Hwilt). Thus, in the model Hroot is bounded on the wet end
by (Hroot = 0. 0) and the dry end by (Hroot = Hwilt).
The basic input data needed for the solution of the model are:
1. Soil properties h vs 9 and K vs 9 curves covering the range
of water content to be encountered in the problem. The
value of 9-saturated and 9-air dry must also be known.
37
-------
2. 9 vs z and S vs z at the beginning, or at t = 0.
3. Plant properties, root distribution function RDF(z) and
the value of Hwilt.
4. Boundary and climatic properties which include the potential
evapotranspiration and potential transpiration (from which
potential evaporation can be deduced) as a function of time.
These data will come basically from climatic variables of
solar or net radiation, air temperature, air humidity, and
wind speed and the proportion of ground covered by actively
transpiring plants, or measurements of actual evapotrans-
piration. Potential infiltration, and precipitation as a func-
tion of time, are also needed.
5. Presence or absence of water table or layer restricting water
flow at the lower boundary.
The output data that the solution of the model will give are:
1. Cumulative evapotranspiration, transpiration and evaporation
as functions of time.
2. Volumetric soil water content, 9, soil water potential, h,
as functions of time and depth.
3. Cumulative water flow (upward or downward) through the
lower boundary as a function of time.
4. The value of Hroot as a function of time.
Theory and Basis for the Model Development. Equation [30] results
from combining Darcy's law for flow in an unsaturated soil with the
continuity equation. The assumptions underlying this development
are:
1. The fluid of interest, water, is continuously connected
throughout the flow region and is incompressible.
2. Inertial forces are not significant as compared to viscous
forces.
3. Flow is isothermal, vertical and one-dimensional.
4. Biological phenomena have no effect on soil water flow.
5. Air freely and instantaneously escapes from the system as
water accumulates in it.
38
-------
6. Soil does not shrink or swell as water content changes.
7. Water content either increases or decreases monotonically,
thus avoiding the effects of hysteresis of soil properties.
Equation [31] is a modification of Equation [30], so the following assump-
tions were imposed for its development.
1. The roots are considered to be distributed in a continuous
(but not necessarily uniform) manner.
2. No water is stored or consumed by the plant itself.
Equation [30] is a second-order, nonlinear, partial differential equation
of parabolic type. Hanks and Bowers (1962) solved Equation [30] and
developed an implicit-type finite-difference model for infiltration in
layered soil. Hanks, Klute and Bresler (1969) modified the solution
to estimate infiltration, redistribution, drainage, and evaporation as
they occur under field conditions. Since the present model, Equation
[31], is a modification of Equation [30], the generalized numerical
solution is presented herein.
For one-dimensional vertical flow from Equation [31 ]
- A(z) [33]
£z
This equation needs to be transformed so that there is only one variable.
Rubin (1966) mentioned three possible ways of doing this transformation.
The transformation used was developed by Richards (1931) involving
the left-hand side of Equation [33]:
C(9) = [34]
where C(9) is the soil water differential capacity. By the chain rule
of calculus:
The substitution of Equation [35] into Equation [33] yields:
39
-------
K(9)
+ A(z)
[36]
where the hydraulic head (H = h + z) is the only dependent variable.
The finite-difference form of the left-hand side term of Equation [36]
is:
+ c
i i
j-1
AT
= c
j-1/2
At
[37]
where the subscript i represents the depth of a node, and the super-
script j represents time.
The first step in finite differencing the first term on the right of
Equation [36] is:
K(9)
i
Az.
K-
[38]
where the identifier 1 is the mesh increment between nodes i-1 and i,
the identifier 2 is the mesh increment between nodes i and i+1, and the
identifier 3 is the mesh increment between nodes i-1 and i+1. Solving
for the second and third term on the right-hand side of Equation [38]
yields:
K
ZH
Bz
1
(Ki^
lAzi]
[Hi-l
+
2
HLi
^~1+
2
H? \
i
K
[39]
%H
dz
2
^2\
1AZ2J
i i
I 2 '
Hi+l +
2
i i
Hi+l
/
where K is the average of the K values corresponding to the 9 values
at nodes (i-1, j-1), (i-1, j), (i, j-1) and (i, j), and KZ is similarly
associated with nodes (i, j-1), (i, j), (i+1, j-1) and (i+1, j). Another
way of defining K and K that has been used is:
1 ^
40
-------
K
K
and
K - K
K2 - K
[40]
The substitution of Equations [39] and [40] into Equation [38] yields:
Az
I? + HJ ^
i i
J-1/2
[41]
Hanks and Bowers (1962), and Hanks, Klute and Bresler (1969) assumed
constant depth increments, therefore, having:
Azi = Az2 = AZ3
In this model variable depth increments are considered, hence,
Az , Az_, and Az are not equal and are defined by:
L £ 3
Az = z. - z. ; Az = z - z.; Az = (z - z. )/2
1 ii-l 2 i+l i 3 i+l i-l
[42]
Finally, the finite difference for the last term of Equation [36] is:
RDF. (hp"! -
j-1/2
i i
Az,
[43]
where hp? = Hrootjrt + (RRES) z ; and hs] = hj.~ + s]~
i 0 i 111
[44]
Substituting Equations [37], [41], and [43] into Equation [36], and sub-
stituting for H = h + z, yields:
41
-------
hj -
1
c
-l/2
1
AZ3
/ iJ'1 , t,J uJ-1 uJ , 0 \
f h. , + h. , - h. - h. + 2z
i-l i-l i i
2Az
i •!• i
jJ-1/2
Ki-l/2
At
i \ i /
,-_i ; . t45]
+ RDF. (hpj -
h. + h. - h.+1 - h.+
1 + 2z \
2Az_ 1
\ 2 /
11 11
Equation [45] was the basic linear equation used to solve the model. This
equation was programmed and solved by computer from a knowledge of
appropriate boundary and initial conditions. Detailed explanation of the
computer program and the solution of Equation [45] is presented in the
following.
General Program Description. The FORTRAN program is given in
Appendix B. The input and boundary data necessary for the program
must be obtained for the specific crop and field condition for which
the study is to be done. The program calculates the different variables
for any time period and prints the output at any time interval required.
A step-by-step description of the program follows:
Step 1. The program reads and prints all the input and boundary
data. These data include tables of conductivity and soil
water pressure head as functions of water content, and
root distribution as functions of depth. The potential
water and salt flux at the surface, as well as potential
evaporation and evapotranspiration as functions of time
are also input data a~ are the maximum and minimum
plant water potential. Other input information needed
are the initial time increment to be used, the upper and
lower limits on pressure head and water content (that is,
saturation and air dry), the length of time the computation
is to run, and the condition of the lower boundary (two
conditions, a constant pressure head or no flux are pro-
vided).
Step 2. The diffusivity as a function of water content is computed
and printed, as well as the pressure head as a function
of water content at the different depth increments.
Step 3. The subroutine "plot" is called and water and salt con-
tent versus depth are plotted for the first time increment.
42
-------
Step 4. From the initial water content as a function of depth,
values of hydraulic conductivity as a function of depth
are computed by the procedure outlined by Hanks and
Bowers (1962). Values of the specific water capacity
(C = A9/Ah) as function of depth are computed from the
water content and the pressure head-water content re-
lations. A surface pressure head is computed to give
the estimated flux at the surface in conformance with
boundary conditions applying at the time using the
following equation:
n, j. v, v, K x A \
(h + h - h - h + Az)
ER = -5 - - - [46]
where ER is the flux at the surface, h and h are the
pressure heads at the surface at the end and beginning of
the time interval, h and h are the pressure heads at
depth Az from the surface at the beginning and end of the
time interval and K . is the hydraulic conductivity
1 / ^
assumed constant over the time interval and applying
between the surface and z = Az. The surface pressure
head is allowed to vary only between limits (that is,
saturation or air dry). So the computed flux may be
different from the potential flux. To solve Equation [46]
a value of h is assumed (h' = Hdry, if it is evapo-
ration, h = Hwet if it is precipitation) since it has not
been computed yet.
Step 5. A value of Hroot is hunted that satisfies the condition
(Sink
-------
Step 6. The tridiagonal matrix is solved for the pressure head
at the end of the time interval at each depth increment
as described by Hanks and Bowers (1962). The only
difference is Az is variable in the model used herein.
Step 7. The water content at each depth increment is computed
from a knowledge of pressure head at each depth incre-
ment and water capacity as functions of depth and pressure
head-water content relations, using the following formula:
9J+1 = CJ [hJ+1 -- hJ] +9J [47]
1 11 1 J 1 J
The values of h. and h. are computed in Step 6.
Step 8. The program tests the total change in water content
(SA9 £ ConQ, where ConQ is the largest total water
content change allowed for each computation). If
ZA9_> ConQ, then the time is reduced by half and the
program goes back to Step 6. If SA9 <_ ConQ the pro-
gram proceeds to Step 9.
Step 9. The program computes the water flux at the surface and
at the bottom boundaries.
Step 10. Cumulative values of various variables are computed,
desired output is printed, a new A*t is chosen that
satisfies the condition I&9 <_ ConQ, and the values of
h. and 9. taken as the new initial conditions h.,
11 i
Step 11. The cumulative time is checked to adjust the potential
boundary conditions if necessary. The process is re-
peated from Step 4 above until completion.
Salt Model
The present model is essentially the combination of the model for water
and salt flow by Bresler and Hanks (1969) and Dutt et al. (1971) models
for solubility of minerals and exchange between the solution and solid
phase. The essential features of the water flow model were discussed
earlier. One-dimensional flow is considered in the model.
44
-------
The rate of flow of salts at any plane in the direction of flow may be
given by the equation
[48]
The first term on the right, in the above equation, represents the
contribution from diffusion to the flow of solute and the second term
represents the contribution from viscous flow. S is the sink or source
term due to solubility of minerals and exchange of ions in solution with
solid phase. Each component of Equation [48] is discussed separately.
Mass Flow of Salts. If the dispersion is absent and no sink or source
exists, the flow of salt is due to the mass flow of water expressed as
[49]
Numerical approximation of Equation [49] leads to
At
cJ-l/2 _ -j-1
i i-1
Az
J-l/2
c
i-1
[50]
with the approximation, c. = c. and c. _ = c. , , Equation
11 i-l i-l
[50] reduces to
cj =
r j-1/2 j-1 -j-1/2 j-1 At
(v. c. - v. c. ) -T—
i-l i-l i i Az
[51]
Equation [51] and its modification are used to compute the mass flow
of salt due to water.
Dispersion of Salts. If there is no dispersion, there should be piston
flow of salts and sharp boundary in the salt distribution should exist at
the wetting front. Since the numerical approximation involves the mixing
of solutions and then averaging over a new water content (Equation [51])
45
-------
a diffuse salt boundary exists at the wetting front. Although in the present
model dispersion is ignored explicitly, the mixing of salt indicates a
"built in" dispersion in the numerical method of salt flow.
Sink or Source Term. The concentration of salts at each depth is modified
due to the chemical reactions like precipitation or dissolution of minerals
and exchange between ions in solution and soil matrix. Both these pro-
cesses contribute to the source or sink term in Equation [48].
Dissolution or Precipitation of Gypsum. A slightly soluble salt often
present or added to the soil is gypsum. An equation relating gypsum
to other constituents in soil is
CaS04 • 2H24~~ + 2^0 [52]
The solubility of gypsum is described by the solubility product constant
concept
= a a = C C T' = 2- 4 x 10'5 [53]
Ca SO, Ca SOA
4 4
where Ksp is the solubility product constant, a is the activity of the ions
designated, y is the activity coefficients of divalent ions (7^ = TCQ ^'
4
and c is the equilibrium concentration of ions designated which are defined
further as follows.
Let x moles per liter of Ca and SO ~~ that dissolve or precipitate
I J^
and c° , c° are the initial molar concentrations of Ca and SO ,
Ca SO. •*
4 ++
respectively. Then the change in relative composition of Ca and
is
46
-------
Combining Equations [54] and [55] with Equation [53], results in an equa-
tion of the form
x2 + Bx + C = 0 [56]
where
B = c_ + ~°
Ca
o o
= CCaCSO
4
Equation [56] can be solved for x.
Undissociated Ca and Mg Sulfate. In addition to the dissolution or
precipitation of gypsum, the CaSO , Ca , SO , HO system involves
^t ^t C*
the formation of undissociated CaSO.. The dissociation constant
4
K- q^o-, of ion- pair is defined as
K[CaSO°] = A
L 4 4 4
where c o is the molar concentration of the ion-pairs and y for
CaoO .
ion-pairs is taken as unity.
Let x, be the moles per liter of Ca and SO. which forms undis-
1 r 4
sociated CaSO... If the initial concentration of CaSO. ion-pair is
o 4 4
c o then the change in concentration will be
\jSiO\J .
CCa = °Ca - Xl [58J
O
<"* — P — 5C
A S°x, 1
4 4
47
-------
CCaSO° = CCaSO° + Xl
4 4
when Equations [58], [59], and [60] are combined with Equation [57],
rearrangement yields an equation of the form
2
Ax + Bx + C = 0 [61]
The chemistry of undissociated MgSO is,. similar to CaSO and results
in an equation similar to Equation [6l], where
A = Y
B = ~ ( K[CaSO°] or [MgSO°] + ^ CCa or Mg + ^
r - V
7 °Ca or Mg°SO " [CaSO°] or [MgSO°] °CaSO° or MgSO°
Equation [61 ] can be solved for x When the system contains gypsum,
the undissociated CaSOx becomes constant
4
CCaSO° = Ksp/K[CaSO°] [62]
Dissolution or Precipitation of Lime. An equation relating to the dis-
sociation of lime in water with its constituent is shown as
CaCO ^ Ca++ + CO "~ [63]
and the solubility of calcite is usually described by the solubility product
constant Ksp:
KSP =
48
-------
where a is the activity of ions designated by the subscript. Since CO
concentration is a function of partial pressure, and HCO concentration
is usually the predominant form in which CO occurs in soil water
L*
systems, it is more convenient to consider the following reactions.
H CO + CaCO ^ Ca++ + 2HCO " [65]
c* 3 3 O
K = aaa [66]
If an equilibrium system is under constant pressure of CO and if the
LJ
activity coefficient of non- charged species (H CO ) is unity, Equation
[66] becomes
2 =
ZE = Z'2 = CCaCHC03
where y is the activity of association.
It has been pointed out by Olsen and Watanabe (1959) that the solubility
of CaCO in the soil is different from pure calcite, and the HCO
J £* -3
content in the soil solution is variable at different moisture contents.
This in turn means that the value of Z, in the soil, varies with water
content. A comparison of Equation [64] with Equations [67] and [68]
shows Z and ZE to be equivalent to the solubility product constant.
Dutt et al. (1971) determined the following relationship between Z
and water content:
log Z = - 1. 68 log W - 4. 46 [69]
where W is water content by weight expressed as percent. The same
relation is used in the present model. ZE is then estimated from
Equation [68].
49
-------
Using the same argument as in the case of solubility of gypsum that x
is the moles per liter of Ca that dissolves or precipitates, then the
equilibrium concentration of Ca and HCO is
c_ = c° + x. [70]
•Ca Ca ' 2
o
c = c +
TT> T-3(~T} /
ri^i\J n.\j\J &
Substituting Equations [70] and [71] into Equation [68] results in a cubic
equation
4x23 + B x22 + C x2 + D = 0 [72]
where
T, „
B = 4 CCa
2
o o o
°HCO + 4 °Ca °HCO
_ o o
D = c c
WfO r"a
JTIO v^ v^d
Equation [72] can be solved for x by Newton Raphson iteration method.
Cation Exchange. An equation that described Ca-Mg exchange is
aCa/aMg = KCa-Mg ECa/EMg
where K^ ,, is the exchange coefficient for Ca and Mg. Let y moles
Ca-Mg
of Mg per gm of soil go into solution or be adsorbed. Let the initial
++ ++ o o
concentration of Ca and Mg be c and c_, moles/liter in the
Ca Mg
50
-------
solution phase and E^, , E, , be moles/gm adsorbed on the soil matrix.
Ca Mg ++ ++
The change in the relative composition of Ca and Mg from the
interaction of solution and adsorbed phase is then
ECa = ECa
[74]
,0
EMg EMg
'Ca
[75]
[76]
CMg = CMg
[77]
where (3 is the ratio of grn of soil to liter of solution. Combining
Equations [74] to [77] with Equation [73] results in quadratic expression
Ay + By + C = 0
[78]
where
A = (3 1 - K
Ca-Mg
B = (3
E
Mg
KCa-MgECa
+ c + K c
Ca Ca-Mg Mg
°Ca Mg " Ca-Mg Mg Mg
Equation [78] can be solved for y.
Gapon's equation was used to describe the non-symmetrical exchange
between Ca and Na
aCa/aNa KCa-NaECa Na
[79]
51
-------
Using the same reasoning for calculating the. equilibrium concentration
as in the case of Ca-Mg exchange, Equation [79] reduces to
432
Ay + By + Cy + Dy + E = 0
[80]
where y is the change in concentration required to reach equilibrium
from initial concentration, and
A = - 4 K _ p
Ca-Na ^
B =
KCa-NaECap + KCa-NaCNa
where y , is the ratio of activity coefficient of Ca to Na,
i I £
2
C = 4y
1/2
Ca
2 o
Ca-Na°Na
D =
E =
" 4KCa-Na(3ECa
o o
Ca CNa
NaYl /2
4c + E p
Ca Na
2
2vf E° c°
Ca-Na Ca Na
2 2
TT° ° PC ° F°
Na°Ca'yi/2 ~ Ca-Na °Na Ca
Na Na
Equations [56], [6l], [72], [78], and [80] are used to calculate the
equilibrium concentrations.
Description of Computer Program. The computer model of Dutt et al.
(1971) for solubility of minerals and exchange between ions in solution
and soil was combined with the salt and water transport model of Bresler
and Hanks (1969). The resultant model consists of a main program and
five subprograms. The subprograms are designated as: (1) PLOT,
(2) EXCH, (3) EQEXCH, (4) SALT, and (5) ACOF.
The complete FORTRAN program is listed in Appendix B. The main
program does several things. First, it reads the initial and boundary
52
-------
conditions. The initial conditions in his experiment include the con-
centration of salts applied on the soil surface at the beginning of the
experiment. Since the salts were applied in the powder form rather than
in solution, it was assumed that they were soluble at the given water
content of the soil. The program then calls for subroutine EQEXCH.
This subroutine calculates CaSO , MgSO ion-pairs and equilibrium
concentration of exchangeable ions. The input and transformed data
are then printed to provide the user with a record. Concurrently, the
main program calls for subroutine PLOT which plots the water and
salt content with depth. After setting various counters and initializing
certain values, the program computes the new values of pressure head
and water content.
The routine then executes a large outer loop for the number of depths
in a profile. Within this loop the routine checks for the amount of
water leaving or entering the top or bottom of a soil segment at a
particular depth. If the amount of moisture flow is not negligible,
subroutine SALT is called which computes the flow of salts due to mass
flow of water. A check is then made to call the subroutine EXCH. The
check insures that changes in concentration of ions due to solubility
of minerals and exchange are calculated every hour rather than every
At. No great difference was noted in the predicted values when sub-
routine EXCH was called each At. The counter for this check is
initialized to zero after each call for subroutine EXCH.
Then the program increments the time counter with At and initializes
the old values with the recently computed values of the variables used
in salt and water flow. The routine then calls for subroutine PLOT and
prints the output.
A check is then made for the new boundary conditions and cumulative
time for which the program is allowed to run. If the time equals the
cumulative time it then stops after the subroutine PLOT is called
and the needed output information is printed. Otherwise, it goes back
to statement 16 and executes for the next At increment.
The input data needed (besides that listed earlier for the water flow
program) are as follows:
1. Activity coefficient-ionic strength tabular data covering the
range of ionic strength encountered in the system.
2. Chemical composition-depth tabular data at the beginning
(initial conditions). This involves the knowledge of the
53
-------
chemical analysis of the important chemical species. At pre-
sent, Ca, Mg, Na cations and Cl, SO , and HCO3 anions are
considered.
3. Chemical composition of the irrigation or rain water (boundary
conditions).
The type of output data available is almost infinite. Consequently, a
selection of the desired data (besides that listed earlier for the water
flow model) is made from the following:
1. Chemical composition of the soil solution vs depth and time
during the period.
2. Chemical composition of the water going into the water table
or up from the water table as a function of time.
The EXCH subroutine is called in the main program approximately every
hour (real time) or at each At if At is greater or equal to one hour. This
implies that in a time of one hour equilibrium is established between
the ions in the solution and solid phase. Adjustment in the concentration
of different ions due to solubility of minerals and exchange with soil
particles is made in this subroutine. The adjusted concentrations are
then returned to the main program.
Since the concentrations of exchangeable cations are necessary to
predict changes in soil solute composition and reliable analytical
methods are not available when excess calcium carbonate is present,
an improved method for their calculation is necessary. The EQEXCH
subroutine calculates exchangeable ions from initial soil analysis. It
also calculates the concentration of Ca , Mg , SO , CaSO ion-
pair and MgSO ion-pair from their total analysis. Theory underlying
this subroutine is discussed in the following sections.
Sulfate occurs in basic solution in more than one form. In addition
to free sulfate ions, there are two forms which have been shown to be
of importance in base saturated soil-water systems; these are undis-
sociated, soluble CaSO (Dutt, 1964) and MgSO (Tanji and Doneen,
1966). Thus the total sulfate in solution is
CTS04 = °S04 + CCaS04
54
-------
Similarly, the total calcium, c and magnesium, c is
TCa TJVIg
CTCa = CCa + C [82]
CTMg = °Mg + °MgS04
The thernaodynamic equilibrium constant for equilibrium between the
undissociated species in solution and the appropriate ions is
aCaaSO
- [84]
and
aMgaSO
aMgSO°
Combining Equations [82] and [84], we get
-------
where
x = c
SO
A = y.
B =
7,
(K[CaSO°] + K[MgSO°]
4-
(G
TCa TMg
C = K[CaSO°]
4J
K
- CTS04K[CaSO°] + K[MgSO°]
D = CTS04 K[MgSO°]
Equation [88] is solved by Newton Raphson method for c . Concen-
4
trations of Ca and Mg are calculated using Equations [82], [83],
[86], and [87].
Equations [73] and [79] are used to describe Ca-Mg and Ca-Na exchange
in this model. If calcium, magnesium, and sodium are the only cations
in the soil then
ET = ECa + EMg + ENa
[89]
where E is the cation exchange capacity. Combining Equations [73]
and [79] with Equation [89] results in
56
-------
ET
E = - ± - r90i
Ca a K a L J
Na Ca-Mg Mg
K / - a
Na-CaVa_ Ca
Ca
Exchangeable cation concentrations are calculated using Equations [79],
[89], and [90]. The EQEXCH subroutine is called only once at the start
in the main program.
The SALT subroutine calculates the changes in salt concentration due to
mass flow of water. The mass flow of salt is computed by Equation
[49].
The ACOF subroutine is called in both subroutines EQEXCH and EXCH.
It calculates the activity coefficients of monovalent and divalent ions.
In dilute solution, activity coefficients of ions can be adequately des-
cribed by a modified form of Debye H'uckel law for mixed electrolytes
0.509 Z2 JT
logy. = -
1 +
where
I = ~ £ c.Z2 [92]
2p i=i i i
where i is the ion species of interest, n is the total number of ion
species in solution, Z is the valence, and p is density of the solution
-------
7.KC1
As a first approximation, it is assumed
, NaCl . ,
± _ [94]
This subroutine uses the table value of divalent or monovalent ion
activity coefficient corresponding to a given ionic (I) strength.
58
-------
SECTION VI
TESTING OF MODELS
Before the details of the testing of the models are discussed descrip-
tions are given of the field facilities and type of data collected and the
laboratory experiments and type of data collected.
,'
Field Facilities and Data
The field work was conducted on the Hullinger farm in the Ashley Valley
near Vernal, Utah (Figure 2). The farm was leased on a year-to-year
basis beginning October 1, 1969, with the University having the option
to renew the lease for a period of at least ten years. This type of a
lease agreement assured the availability of the farm for research
purposes for a ten year period. The total area of the farm is approx-
imately 52 acres, of which about 35 acres lying north of the Naples
Drain was the study area. A map of the farm is shown in Figure 3.
Drainage System
Construction of a tile drainage system was completed in March, 1970.
The system consisted of six separate drains discharging into the
natural drainage channel as shown on the map of Figure 3. Each drain
had a manhole designed to accommodate a V-notch weir and water
stage recorder (Type A-35, Leupold & Stevens) for measuring and
recording the drain discharge and to provide access for water quality
measurements of drainage effluent.
Drains 1, 2, 3, 4, and 5 are spaced 200 feet apart. Drain 6 is 350 feet
west of drain 5. The depth of drains averages approximately five
feet from ground surface to the invert of the tile. The drains are con-
structed of six-inch concrete tongue and groove pipe in 36-inch lengths
with a minimum of a four-inch gravel envelope surrounding the pipe.
Nearly all of the trench was dug with a trenching machine which left
approximately a two-foot width of trench, hence, the gravel envelope
along the side of the pipe is thicker than the minimum of four inches.
About 400 feet east of drain 1 and parallel to it, there exists a deep
tile drain which has its primary function the drainage of the Vernal
Municipal Airport runway. The drain is estimated to be in excess of
eight feet deep along the eastern boundary of the Hullinger farm.
59
-------
- 27'30"
n '-"'ss ~ .cc Til
7' I; 7T '•
-------
_ J c.J
f-> t
\
fe- •
r'
"I*
( -j
]$
;i *
. '
I "" '
1 ^ i ^ *
o H I ""• >] a-1
^ -i i ^ ' 5^, ^i
< ^ i ** St ' > '
2 ', *! ..>'V '! ' ^!
AO i A ^' 'r ^ '
; o»*-t2i v ' A '
. • v ' ?r » t .
T
-~ k'.
6!
>vA
%,
I
-«.»'
^,
J « PHDBl Sl*SOX
'. . rswr nc» siANfinri*
FARM LAYOUT
« 'JO (00 JOO
Figure 3. Farm layout.
-------
jPiezometers and Observation Holes
The solid black dots on Figure 3 indicate the location of sets of piez-
ometers which are used to measure groundwater potential gradients,
the direction of groundwater flow, and the water table elevation. Each
set has pipes extending to depths of 6, 9, and 12 feet below ground sur-
face. It was expected that the primary direction of groundwater flow
would be to the east, essentially parallel to ground surface. Although
the amount of irrigation water applied to the farm was controlled easily
by the sprinkler system, surrounding farmers continued to use a flooding
method of irrigation. Hence, groundwater was also expected to move
toward the farm from the north. The piezometers were located to detect
these groundwater movements.
Figure 3 also shows the location of observation holes used to sample
groundwater quality. The observation holes labeled B and C north of
the road penetrate to shale as do the seven unlabeled holes around the
edge of the study area.
Sprinkler System
A solid-set automated sprinkler system was installed on the farm. The
system has electric valves which are wired to give irrigation in blocks
of four laterals (two on either side of a drain) operating simultaneously.
The blocks are indicated near the center of Figure 3 by the brackets
and circled numbers 1 through 9. The laterals run north and south,
parallel to the drains, and are spaced 50 feet apart. Sprinklers are
spaced thirty feet apart on each lateral. All of the system is above
ground. The system is designed such that the time of irrigation of any
one block can be set from a few minutes up to 24 hours, and the system
will automatically sequence from one block to the next. Any one or
more blocks can be completely skipped in an irrigation sequence.
The sprinkler system is designed to deliver approximately one quarter
inch of water per hour and is powered by a 25-horsepower, 3 phase
electric pump which removes water from an irrigation pond holding
enough water for two hours of operation of the system. The pond is
lined with a 20-mil thick black PVC exposed lining and has an over-
flow which will allow excess water to spill into the Naples Drain.
Electrical power is supplied separately to the instrument trailer
located on the north edge of the farm. This power operates the auto-
mated valves and other instrumentation.
62
-------
Crops History
Prior to the University's operating the farm, the crops consisted
mainly of irrigated pasture with a small acreage of oats and alfalfa
in the area immediately north of the Naples Drain. The entire farm was
flood irrigated. In the first week of June, 1970, the 35 acres north of
the Naples Drain was seeded to alfalfa with oats as a nurse crop and
irrigation with the sprinkler system began in the latter part of June.
Prior to seeding, soil samples were taken which were analyzed for
nutrient availability. Phosphate was applied at the recommended rate
of about 90 pounds per acre and 35 pounds of available nitrogen were
applied to provide good growth of the oats. The crop was field chopped
in the late dough stage.
Due to a rather uneven stand of alfalfa, alfalfa was reseeded with a
drill in the existing stand in the spring of 1971. Until the first cutting,
rather frequent irrigations were applied to obtain a good alfalfa stand.
Thereafter various irrigation frequencies were used and data were
collected to field test the models.
EyajDotranspiration
Actual evapotranspiration was measured by means of lysimeters.
Potential evaporation (E ) was calculated from a combination equation
X
developed by Penman (1963) using daily values of a minimum number
of meteorological parameters. The required meteorological data con-
sist of:
1. Daily maximum and minimum air temperatures.
2. Daily solar radiation.
3. Average dew point temperature.
4. Daily wind run at a known height.
The combination equation is:
EF ' -ST (Rn) + 77 (15'36) » + °'01 w) (es - ea> [97]
where A is the slope of the saturation vapor pressure-temperature curve,
Y is the psychrometric constant equal to 0. 57 for Vernal conditions, w
63
-------
is the total daily wind run in miles, e is the mean saturation vapor
s
pressure in mb, e is the saturation vapor pressure at mean dew point
a -2 -1
temperature in mb, Rn is the daily net radiation in cal cm T . The
parameters A/(A + y) and y/(A + y) are mean air temperature sensi-
tive factors whose sum is 1. 0 (Jensen, 1966). It was assumed that soil
heat flow was negligible.
The net radiation (Rn) was calculated from
Rn = (1 - p)R - RL [98]
where p (albedo) is reflection coefficient assumed equal to 0. 20, and
R is total incoming solar radiation in cal cm T . R , the net long
-2 -1
wave back radiation in cal cm T was calculated from:
R = [0.98 - (0.67 + 0.044e 1/2)] [0.5855 (10~7)]
i t 2L
[(T + 273)4 + (T . + 273)4] [99]
max mm J L J
where T and T . are maximum and minimum air temperature
max mm
C, respectively. The data for actual and potential evapotranspiration
were measured periodically twice a day.
Potential evapotranspiration for a given agricultural crop can be related
to potential evaporation from a free water surface by:
E = KE [100]
where E is potential evapotranspiration, K is crop factor (dimension-
less), and E is potential evaporation from free water surface.
F
Equation [100] is applicable when soil water is not limiting.
Soil water content profiles were arrived at by measuring the water
content of the soil at different depths before and after each irrigation
using neutron and gamma scattering devices. Details of these measure
ments are given later.
64
-------
Lysimeters
Two lysimeters 4 by 4 by 4 feet were installed in the Vernal farm. The
lysimeters used were similar to those developed by Hanks and Shawcroft
(1965). The total weight of the lysimeter was distributed over the two
wooden blocks which sat on two rubber bags. The pressure of the water
in the bags was equal to the total weight of the inner tank and contents
divided by the area of the two wooden blocks. The wooden blocks were
used to maintain a constant area over which the weight was distributed.
The pressure was measured as the height of water in the standpipe
(active tube). The "dummy" standpipe was used for temperature
correction.
The change in weight of the lysimeter was due to evapotranspiration or
precipitation. Moreover, the weight changes are most conveniently
expressed as an equivalent depth of water. The equation expressing
this relation was given by Hanks and Shawcroft (1965):
A Pf
E = Ah -^- —S- [101]
a A. p
1 w
where E is evapotranspiration (or precipitation) in cm of water,
cl
Ah is corrected change in height of fluid in standpipe, A is the area
over which the weight is distributed, A is the area of the bottom
of the lysimeter, p is the density of fluid in the standpipe, and p is
A Pf
the density of water. In other words (— ) is the calibration coef-
A, p
1 W
ficient of the lysimeter. In the case of the lysimeters installed for
this experiment, it was equal to 0. 53. The value of Ah was measured
from readings of the standpipe (active and dummy) at two different
times. Hence, for the lysimeters used in the field experiment,
Equation [101] becomes:
E * 0.53 [(A - A) - (D - D>] [102]
where A and D are readings of active and dummy standpipes at first
period, and A~ and D are readings of active and dummy standpipes at
<£ tL
second period, respectively. The data collected is presented in Appen
dix C, Table 34.
65
-------
Neutron Probe
Soil moisture determinations were made by the neutron scattering
method. Equipment manufactured by Troxler Electronic Laboratories
of Raleigh, North Carolina was utilized. The probe was Model 1255,
1. 865 inches diameter with americuim-beryllium as a fast neutron
source, and with a nominal activity level of 100 millicuries. The
sealer was Model 2651 with count indicators and was battery operated.
Moisture content on a volume basis was determined by taking neutron
counts at the desired depths, comparing them to the neutron counts
through the standard and then applying the calibration equation. Read-
ings at various depths were made by inserting the neutron probe into
access tubes penetrating the root zone to a depth of 7. 0 feet. These
access tubes were made of two-inch outside diameter aluminum pipes,
placed vertically in the soil by augering. While not in use each tube
was closed by a rubber stopper to prevent the tube from filling with
water while irrigation was taking place.
The probe was calibrated to compare results with a general calibration
supplied by the manufacturer. One metal barrel 46 cm diameter and 56
cm high was filled up to 45 cm with air dry soil. Another barrel was filled
with field moist soil and a third barrel was filled with field moist soil
brought to saturation and then drained for 48 hours. The moisture
contents of the soil were determined gravimetric ally and counts per
minute of the neutron probe were taken at 20, 23, and 25 cm depth
in each of the barrels and the average count computed. The ratio of
the counts per minute in the soil to the shield standard for each soil
was calculated. The results are tabulated in Table 2.
Table 2. Results of calibration of the neutron probe.
Relative Water content Bulk Water content
Sample counts by weight density by volume
R gm/cm 9
Air dry soil
Field moist soil
Field moist soil
(before saturation)
Field moist soil
(after drainage)
0.062
0.562
0.601
1.089
0.013
0.159
0. 137
0.239
1.482
1.354
1.548
1.548
0.019
0.216
0. 212
0.370
.\ ' •
-------
The barrel cialibration resulted in the formula:
9 = 0.3591 R - 0. 0038 [103]
as cotnpared to
8 = 0.4149R - 0.0410 [104]
supplied by the manufacturer. 0 is water content by volume and R is
th^ ratio of soil count rate to shield standard count rate. The differences
between the calibration curves do not allow drawing a conclusion as
to Whether different soils require separate calibration curves as recom-
mended by Mortier and Deboodt (1956), McGuinnes, Driebelbus, and
Hajfold (1961), and Nimah (1968) or whether one calibration is enough,
aS reported by Gardner and Kirkham (1952). Equation [103] was used
for1 moisture determination throughout this study. Tables 35 and 36,
Appendix C, summarize the data collected during the 1971 growing
season.
Gamma Probe
The two-probe gamma density gauge used in this study was manufactured
by Troxler Electronic Laboratories of Raleigh, North Carolina. The
137
two»probe density gauge was Model 2376 and used Cs as a source of
gamma photons of 661 Kev energy with a nominal activity level of five
miilicuries. The detector utilized a thallium activated sodium iodide
crystal. The system used a pulse height analyzer which rejects all
radiation above and below a 661 Kev energy level.
count rate in the soil, I, is given by the following:
I = IQ [exp(-(nspb + uw0pw)X)] [105]
Where I is radiation intensity with no interference, p is the bulk
dehsity of the soil, 9 is the volumetric water content, p is the density
df water, and |JL and (J. are the mass absorption coefficients of oven
s w
soil and Water, respectively, and x is the thickness of the sample
67
-------
(cm). Accurate values of the mass absorption coefficients of the soil
and the water are needed if Equation [105] is to be used for determining
density and water content of the soil (Davidson, Biggar, and Nielsen,
1963). As the water content increases, the radiation passing through
the sample decreases. It is apparent from Equation [105] that changes
in the bulk density of the soil cause corresponding variation in the
radiation intensity passing through the soil water system. If the bulk
density is constant, changes in "I" from one period to the next are
due to changes in water content. Although this is a major assumption
of the method,', it offers no limitation for many agricultural soils.
Equation [105] requires a knowledge of I , p. , \j. , p and p to calculate
0 from detector count rate reading, I.
The attenuation coefficient or mass absorption of oven dry soil and
water were determined for Mesa fine sandy loam and water. The
procedure for determining them was essentially the same as given
by Davidson, Biggar and Nielsen (1963). The attenuation coefficients
for soil and water were measured as 0. 065 and 0. 067, respectively.
These results are lower than those reported by Davidson, Biggar and
Nielsen (1963) which were 0. 077 (soil) and 0. 082 (water). The reason
for these differences is not known. Measurements on the other soils
yielded almost identical lower results. Therefore, the values 0. 065
(soil) and 0. 067 (water) were used throughout this study. The processed
data is shown in Appendix C, Tables 37 and 38.
Climatic Data
A weather station was located on the farm, as shown in Figure 3.
Measurements of global radiation, wind velocity, and wet and dry
bulb temperatures were taken during the experiment.
Global radiation was measured by a radiometer Model No. 633, Science
Associates, 230 Nassau St. , Box 230, Princeton, N. J. It has a
-2 -1
sensitivity of about 8 millivolts per cal cm min , with an effective
wavelength range of 0. 3 to 2. 0 microns. The measurements were
recorded on an integrator using this formula:
R = 2.7775 [(0.1016 Dx) - (I) (min)] [106]
where R is total radiation, Dx is the difference in integrator readings
68
-------
at two different times, I is the average "zero" current intensity during
the time interval, and min is the lapsed period in minutes between the time
of measurements. The net radiation was calculated from the total rad-
iation using Equation [98]. Data of R and computed R and R are shown
in Table 39, Appendix C.
Wind velocity was measured at 200 cm above the soil surface by an ane-
mometer (Science Associates, U.S. Weather Bureau Specification Number
450. 6103). The anemometer consists of three conical cups of 2.75 inches
in diameter mounted on a rotor with a turning diameter of 12. 5 inches,
a starting speed of 3 mph, and an accuracy of i 1. 5 mph to' 70 mph. The
measurements were taken by a totalizing remote electrical counter that
was read twice daily. The data collected is tabulated in Table 39,
Appendix C.
The wet and dry bulb temperatures were measured at about 200 cm height
by a sling psychrometer (Science Associates, U. S. Weather Bureau
Specification Number 450. 1016). It utilized two matched thermometers,
9. 5 inches long, accurate to i 0. 3° F above 0° F and — 0. 5° F below
0°F, mounted on a stainless steel backing. Measurements were made
twice daily. Table 39, Appendix C, shows the data.
Daily maximum and minimum temperatures were measured at the
weather station located at the Vernal Airport about 1500 feet east of
the research farm.
The values of e and e (Equation [97]) were estimated from the following
S 3.
equations:
e = 6.10127 + 0.4538 DB + 0.01217 DB2 + 0.004156 DB3 [107]
s J
and
e = e - 0.57288 (1 + 0.00115 WB)(DB - WB) [108]
3. S
where DB and WB are dry and wet bulb temperatures in C. The data
are tabulated in Table 39, Appendix C.
Irrigation Data
During the 1970 season, with oats as the primary crop, the entire
farm received the same schedule of irrigation. Conductivity recorders
69
-------
were used to measure the EC of the applied water. Considerable
difficulty was experienced with the battery powered recorders in the
field. Periodic measurements on samples brought into the laboratory
indicated many malfunctions of the recorders.
In 1971, due to reseeding the alfalfa, rather light frequent irrigations
were used until the first cutting in June as shown in Table 34, Appendix
C. At the time of the first cutting, irrigation schedules were devised
for the various irrigation blocks. The desired schedules for the period
between the first and second cuttings of alfalfa are indicated in Table 3.
Table 4 gives the desired schedules between the second and third cuttings.
The schedules were designed in an attempt to eliminate the necessity of
irrigating on weekends. The EC of the applied water was measured in
the field during 1971 with a portable conductivity meter. The actual
timing, depth, and EC of the irrigations are given in Tables 16 through
20, later in this section. Typical composition of the irrigation water
is given in Table 7 later in this section.
Table 3. Irrigation schedules for various irrigation blocks on the
Hullinger farm between first and second cuttings of alfalfa
in 1971.
Irrigation
Block Interval
(days)
1 #
2 *
3 3.5
Block
4
5
6
Irrigation
Interval
(days)
7
10. 5
14
Block
7
8
9
Irrigation
Interval
(days)
17.5
17.5
*
# Definite schedule not attempted
Drain Discharge
In 1970, water stage recorders were installed in the manholes of drains
4, 5, and 6. The 12-inch float of water stage recorder was centered
in a 14-inch diameter stilling well attached to a weir box with a standard
90° V-notch weir. During 1970, drains 1, 2 and 3 did not discharge
water into the Naples Drain. In the spring of 1971, water stage recorders
were installed in the manholes of drains 2, 3, 4, 5, and 6. Data
70
-------
collected on the discharge of the drains is shown graphically in Figures
5.6 through 59 of Appendix C.
Table 4. Irrigation schedules for various irrigation blocks on the
Hullinger farm between second and third cuttings of alfalfa
in 1971.
Irrigation
Block Interval
(days)
1 *
2
3 17.5
Block
4
5
6
Irrigation
Interval
(days)
14
10.5
7
Block
7
8
9
Irrigation
Interval
(days)
3.5
3. 5
•.!„
-r>
Definite schedule not attempted
During 1970 the conductivity recorders were also used on the drain
effluent. The same problems as described above under "Irrigation
Data" were encountered with the recorders. The details of the EC
data for 1970 are considered unreliable and are not included in this
report. In general the EC of the drain effluent ranged from 1. 2
mmho/cm to 2.4 mmho/cm. In 1971, use of the recorders was aban-
doned and periodic measurements of EC were made in the field with
the portable conductivity meter. Results for 1971 are given in Table
40, Appendix C. Typical composition of the drain effluent is given in
Table 41 of Appendix C.
Piezometric Data
The 80 sets of piezometers shown in Figure 3 were read about weekly
in 1970 and daily for most of the 1971 irrigation season. The data are
too voluminous to include in this report. Samples of the piezometric
data which are considered typical of the irrigation season and of early
spring conditions are tabulated in Tables 42 and 43 of Appendix C.
Field locations are specified with a number, a letter, a number, a
dash (or letter, N), and a number in sequence. The first number
designates a drain, the letter denotes the direction from the drain (E,
71
-------
east; or W, west), the next number gives the distance from the drain,
the dash means south of the north boundary fence of the farm, and the
last number denotes the distance of the piezometer set from the fence.
If the letter, N, is used instead of the dash, the piezometer set is
located north of the fence. For example, "3W20-400" means that the
set is 20 feet west of drain 3 and 400 feet south of the north boundary
fence; "3W5N4" means that the set is 5 feet west of drain 3 and 4 feet
north of the fence.
Analysis of the piezometric data indicates that there is no upward leak-
age of water in the saturated zone; i. e. , no artesian pressure exists.
The general movement of groundwater is from west to east with a slight
southerly component which is most noticeable when the farm immediately
to the north is being irrigated.
Soil Samples
During the 1971 season, the soil was sampled on 3 dates in 1-foot
increments to a depth of 6 feet at six locations in irrigation blocks
3, 4, 5, 6, 7, 8, and 9. The samples were analyzed for moisture
content and EC of soil moisture. A summary of the analyses is given
in Table 44 of Appendix C. Typical composition of salts in the Hullin-
ger farm soils is given in Table 45 of Appendix C.
Groundwater Samples
Typical composition of the groundwater as determined from samples
taken from the observation holes is given in Table 46 of Appendix C.
EC measurements made in the field on water samples taken from the
observation holes are given in Table 47 of Appendix C.
Samples of water were extracted from the saturated zone at 6, 9, and
12 foot depths through pumping the piezometers. This was primarily
a test to see if the piezometers could serve a dual purpose, i. e. , to
provide a site for both piezometric and water quality data. Because
of mud flow into and up the piezometer pipe it was determined that the
open piezometer pipe, while good for piezometric data, would not serve
as a water sampling structure. A ceramic cup should be used for ex-
tracting groundwater samples from the soils. Results are given in
Table 48 of Appendix C. Sampling was begun within a day after flushing
the pipes with city water. Hence, the quality changes reported are
probably not representative of the groundwater for the first few samples.
72
-------
Hydraulic Conductivity Measurements
In September, 1970, field measurements (Jamil, 1971) were made of
the hydraulic conductivity of soils on the Hullinger farm using the auger-
hole method and a ditch test developed by Jenab (1967). The nominclature
for location of the auger hole tests is the same as used to describe
piezometer locations. The auger hole tests were conducted in stages.
The first stage measured the hydraulic conductivity (K) from the water
table (about four feet) to about eight feet below ground surface. The se-
cond stage gave K at depths between 8 and 11 feet. Results are given
in Tables 49 and 50 of Appendix C.
Field Experiment for Detailed Salt Model
The field experiment was conducted on the Hullinger farm. The soil
type was Mesa sandy loam. Tensiometer cups were installed in the
center of the plot at 15, 45, 75, 105, and 165 cm depth at site A
(3E95-380) and 15, 45, 75, 135, and 165 cm depths at site B (3E50-370).
To facilitate the collection of reasonable amounts of soil solution for
electrical conductivity (EC) measurements, suction was applied on the
solution cups for 8 to 12 hours depending upon the moisture content of
the soil. Soil samples were collected for chemical analyses at three
different times during the experiment. Samples were taken at 30 cm
intervals to a depth of 120 cm. Alfalfa was the major crop grown.
Sprinklers were used as a means of irrigation. CaCl • 2H,O(4390.4 kg/ha)
<-• di
and NaCl (3561. 6 kg/ha) were applied in dry form to the soil surface
before the first and second irrigation cycles. Initial and boundary
conditions to the above experiment are given in Tables 5 and 6, respect-
ively. Chemical composition of irrigation water is reported in Table
7. Soil moisture distribution was determined by the neutron probe and
water loss by evapotranspiration was estimated from the lysimeter
data.
Laboratory Experiments and Data
Detailed Salt Model Column Studies
The laboratory experiment was conducted using a lucite column
packed with air dry soil obtained from the Hullinger farm. The column
consisted of 12 stacked rings with an inner diameter of 10.4 cm and
an outer diameter of 11.4 cm. The top ring was 8.5 cm high, whereas
73
-------
Table 5. Initial conditions for field experiments.
Depth
(cm)
0 -
30 -
55 -
100 -
115 -
30
55
100
115
165
Water
Content
(8)
0. 2347
0. 2446
0.2764
0. 3053
0.3661
Calcium Magnesium
(meq/1)
36.0
25.75
27.25
35.10
32.0
(meq/1)
14.31
14.19
16.29
19.95
16.25
Sodium
(meq/1)
5.04
4.22
7.13
4. 91
4.39
Sulfate
(meq/1)
44.25
34.08
44.05
57.84
50.54
Chloride Bicarbonate
(meq/1)
10.35
9.16
5.67
1.30
1.26
(meq/1)
0.75
0.92
0. 95
0.82
0. 83
Gypsum
(gm/lOOgn
0.0
0.5
0.5
0.5
0.5
-------
Table 6. Boundary condition in the field experiment for soil water
and salt flow. Started August 17, 1971.
Time
Interval
(hrs)
0 -
24 -
40 -
48 -
72 -
192 -
264 -
324 -
339 -
408 -
410 -
480 -
504 -
528 -
552 -
576 -
600 -
24
40
48
72
192
264
324
339
408
410
480
504
528
552
576
600
627
Flux at the Surface
(cm/hr)
-0.
0.
0.
-0.
-0.
-0.
-0.
0.
-0.
0.
-0.
0.
-0.
0.
-0.
-0.
-0.
300(1
64
0
211(1
187(1
135(1
219(1
62
224(1
37
190(1
0021
226(1
05
227(1
198(1
191(1
o"
o"
0~
0"
0~
o"
0~
o"
0~
o"
o"
2
2
2
2
2
2
2
2
2
2
2
ET Flux
(cm/hr)
-0.
0.
0.
-0.
-0.
-0.
-0.
0.
-0.
0.
-0.
0.
-0.
0.
-0.
-0.
-0.
^1
300(10 )
0
0
-1
211(10 )
1
187(10 )
_i
135(10 )
1
219(10"1)
0
-1
224(10 )
0
-1
190(10 )
0
i
226(10 )
0
1
227(10 )
1
198(10 )
j
191(10" )
Comment
Irrigation
Irrigation
Rain
Rain
Rain
75
-------
Table 7. Chemical composition of irrigation water.
EC 864 fimho/cm at 25°C
Ca
Mg
Na+
Cl"
HCO "
so4"
CaSO ion-pair
MgSO ion- pair
3.16
3.88
1.6
0.17
0.17
8.3
0.84
1.02
meq/1
meq/1
meq/1
meq/1
meq/1
meq/1
meq/1
meq/1
the other 11 rings were 5. 1 cm high. The rings were interlocked by a
groove and projection arrangement coated with petroleum gel to prevent
leakage of water from the column. The whole column was bolted
together by three brass rods. The bottom ring had a plate at the bottom
with an outlet at its center to collect the effluent. To avoid sealing
the outlet with soil, it was covered with a screen and a filter paper.
In order to avoid layering of soil in the column while packing, the
following procedure was adopted: Two sieves of 4 mm and 2 mm
size were placed one above the other at the top of the column. Air
dried, sieved soil is passed through the 4 mm and then onto the 2 mm
sieve at such a rate that sieves were not blocked. The column was
filled to a height of about 61 cm. The soil was leveled at the surface
by hand. The uniformity in the packing was checked with the density
probe. If the density of any part of the column was not within i 0. 05
_3
gm/cm of the mean density, the column was repacked. (Davidson
et al., 1963).
Three different cases of initial and boundary conditions were con-
sidered:
Case #1. "Sprinkler irrigation" condition with a layer of salt at the
soil surface. CaCl2 • 2H2O salt was applied at the rate of (4547. 2 kg/ha)
76
-------
before wetting with the irrigation water. The soil was tested by simu-
lated sprinkler irrigation using a constant flow pump at a rate of 0. 57
cm/hr. The soil was leached until the wetting front nearly reached the
bottom of the column (35. 6 hrs. ). The column was then segmented. Each
segment was weighed to estimate the bulk density. Portions of the soil
from each segment were used to extract soil solution and to determine
the water content. Exchangeable cations were determined from the
other portion of the soil left in each segment. The chemical composition
of irrigation water and soil is reported in Tables 7 and 8, respectively.
Table 8. Initial soil conditions for column experiments.
Case #1 Case #2 and #3
Calcium (meq/1)
Magnesium (meq/1)
Sodium (meq/1)
Sulfate (meq/1)
Chloride (meq/1)
Bicarbonate (meq/1)
Exchange capacity (meq/100 gm)
Gypsum (gm/100 gm)
Water content (fraction)
15.83
11.31
1.67
26.80
0.75
1.26
11.0
0.0
0.0175
15.0
9. 87
1.49
24. 78
0. 30
1.28
14.0
0.5
0.0175
Case #2.' "Irrigation" with a layer of salt at the soil surface. The
salts applied were CaCl • 2H O (1993.6 kg/ha), MgCl • 6H O
£t Ct & &
(3225. 6 kg/ha), and NaCl (1523. 6 kg/ha). The chemical composition
of the soil used in this case is given in Table 8. The soil was wetted
with distilled water by simulated rain (0. 58 cm/hr) for 37. 6 hours at
which time the wetting front was nearly at the bottom of the column.
The column was then segmented and analyzed by the same procedure as
in case #1.
Case #3. "Irrigation-evaporation-irrigation" with a layer of salt at
each irrigation. Before wetting, CaCl • 2H O salt was applied at the
w L*
rate of 4547. 2 kg/ha. The soil was wetted for 35. 4 hours by simulated
sprinkler irrigation (0. 59 cm/hr). The same soil was used as in case #2.
77
-------
The irrigation water applied had the same composition as in case #1. A
water table was created at the end of infiltration and evaporation at the
rate of 0. 095 cm/hr was allowed for 75. 8 hours. The chemical
composition of the imposed water table was the same as that in the
irrigation water. Evaporation at a rate of 0. 030 cm/hr was then
continued without a water table and with the bottom outlet plugged for
another 196. 8 hours. At the end of evaporation, the soil was wetted
by simulated irrigation (0. 78 cm/hr for 23.7 hours) with a layer of salt
at the soil surface. The salt applied was NaCl (3427. 2 kg/ha). During
infiltration the bottom outlet was unplugged. At the end of the last irri-
gation, the column was segmented and analyzed by the same procedure
as in cases #1 and #2.
Physical Properties of the Soil. In order to test the applicability of the
computer model it is required to have appropriate data of the hydraulic
properties of the soil. These properties are hydraulic conductivity-
water content (Figure 4) and pressure head-water content (Figure 5)
relationships. The data reported by Andrade (1971) for Mesa sandy
loam was used in this study.
Chemical Analysis. Electrical conductivity of the soil solution was
measured with a Beckman Model RC-19 conductivity bridge using a
2 ml pipet cell with a cell constant of one. Measurements were taken
at room temperature and corrected to 25° C.
Chloride concentration was determined potentiometrically using a silver
billet electrode and a saturated calomel reference electrode in con-
junction with a Corning Model 12 expanded scale pH meter.
The solution extract was diluted with lanthanum oxide in concentrated
HC1 and the concentration of calcium, magnesium, and sodium was
analyzed by atomic adsorption spectophotometer (Perkin-Elmer Model
303).
Bicarbonate ion concentration in the irrigation water was calculated
using the relationship
K +
H2° + C°2 * H + HC°3
78
-------
Condition B —
Pressure potential -cm (log scale)
Figure 4. Pressure potential vs water content for Mesa sandy loam soil. Condition A was used
in the computation. Condition B was used to test the sensitivity of the model.
-------
oo
o
.5 -.
o>
o>
§3
o
0>
2 -
.1 -
10
.-8
10
-7
io~6 io"5 io"4 icr5
K-cm/hour (log scale)
10
-2
10"
Figure 5. Water content vs hydraulic conductivity for Mesa sandy loam soil.
-------
K= -^ - - [110]
C°2
where a is the activity of the ions designated, a = my, m is the molality
and Y is the activity coefficient. At the reference state y ~~. ~ a =1
C02 H2°
in pure water. Thus y^^ can be replaced by rn = cP , where
Ov-/— C/CJ_ (_/(_/
£4 Lt £*
c is Henry's law constant (0. 0344 at 25 C), P^^ is the partial pressure
C°2
-4 -7
of CO in atmospheres (3x10 ) and K = 4. 45 (10 ).
Bicarbonate ion concentration in the soil solution was estimated from the
relationship given by Equation [64] and
K +
HCO3 ^ H + CO3 [111]
K = - - i [112]
HC03
where K = 4. 69 (10 ). Details of this method are given by Olsen and
Watanabe (1959). These concentrations were just an approximation and
were corrected by subroutine EXCH to bring them into equilibrium with
the system.
The concentration of sulfate ions was estimated from the difference of
total anions and the summation of chloride and bicarbonate ions.
For the analysis of exchangeable cations (Richards, 1954), 5 to 7 gms
of wet soil sample was washed with 150 ml of 95 percent ethanol in a
leaching funnel until free of .chloride. Exchangeable calcium and
magnesium were extracted by leaching with 100 ml of 1 N sodium
acetate at pH 8. 2. A similar procedure was followed for exchangeable
sodium except that it was extracted with IN ammonium acetate (pH 7. 0).
Analysis of cations was made as described previously.
Because of the insufficient amount of solution collected in the field
experiments for chemical analysis, soil samples were collected and
81
-------
saturation paste prepared (Richards, 1954). The saturation extracts
were analyzed as described previously.
Exchange Constant. Exchange constants are defined by Equations [51J
and [57]. Their values were determined from the known concentrations
of ions in the solution and exchangeable phase. Although their name -;„
implies a constant value, they vary with the total salt concentration in
the present system. It would be more appropriate to define them as
exchange coefficient rather than exchange constant. Figures 6 and 7
are the plots of these coefficients with total salt concentration. Exchange
coefficients for case #1 are given by Figures 6a and 7a, while for cases
#2 and #3, their values are given in Figures 6b and 7b, respectively.
Leaching Factor
The leaching factor, LF, is defined by Equation [27] as the mass of salt
leaving a layer of soil divided by the sum of the initial mass of salt
in the layer and the mass of salt entering the layer. Rasheed (1970)
reasoned that LF should depend upon the following dimensionless ratios:
Moisture content ratio, Q /Q.
o fm
Concentration ratio, C /C
o e
Effluent ratio, d, /d,.
1 fm
Experimental Equipment. A laboratory experiment was designed to
determine the leaching factor for 6-inch layers of Mesa sandy loam.
The equipment consisted of three parts or units: the application unit;
the container unit; and the collection unit.
The application unit consisted of a water reservoir, a connecting tube,
a constant head regulator, a swivel union, a rotating plastic disk, and
capillary tubes. The water reservoir (one gallon capacity) was
connected to the swivel union by a flexible tube (L D. 0. 25 inches) that
passed through the pressure head regulator. The swivel union was
connected to a shaft that delivered water to the capillary tubes and
: otated the circular disk. The rotating disk was provided with 35
polyethelene capillary tubes that were connected to the disk in a manner
that assured uniform application of water to the soil samples. The
plastic disk was rotated at a rate of 2 rpm by a small motor through a
82
-------
2,0r
(a)
o>
I L°
\
50
00
150
200
2.0T
(b)
I
o
O
1.0
\
\
y-
0.6*30.
50
100
150
200
Concentration of solution (meq/l)
Figure 6. Variation of Ca-Mg exchange coefficient with solution con-
centration (a) surface soil, (b) subsoil.
83
-------
10.0
o 5.0
o
50
(a)
y = 4.54
100
150
200
5.0
2.5
(b)
y= 1.58
50 100 150
Concentration of solution (meq/l)
200
Figure 7. Variation of Ca-Na exchange coefficient with solution
concentration (a) surface soil, (b) subsoil.
84
-------
pulley attached to the connecting shaft. The application rate of the ap-
paratus was calibrated prior to the experimentation.
The container unit consisted of a plastic cylinder, a porous plate and
a rigid effluent tube. The base of the cylinder (7. 0 inches high and
I. D. 5. 7 inches ) was fitted with a glass bead porous plate after a cir-
cular ridge had been cut in the bottom of the cylinder. A small space
was provided between the porous plate and the base of the container and
was vented by a rigid plastic tube to provide an outlet for fluid leaving
the sample.
The collection unit consisted of a flask, a graduated cylinder, a vacuum
pump, and a mercury manometer. The graduated cylinder was connected
to the outlet of the sample container by a flexible plastic tube. The
flask was connected between the graduated cylinder and the suction line
of the pump with the same type of tubing. The mercury manometer was
also connected to the suction line.
Experimental Procedure. Bulk soil samples were obtained from two
separate locations on the Hullinger farm. The samples were thoroughly
mixed and sieved through a 2 mm metal sieve and stored in plastic
bags in the laboratory. The average initial salt content in the soil
samples was determined according to the procedure recommended by
Richards (1954); i.e., measurement of the electrical conductivity of
saturation extracts.
Soil samples with a specific salt and water content were prepared by
adding calculated amounts of water and salt to the soil as prepared
above. The quantities of water and salt required to bring the salt and
water content of each subsample to a specific level were mixed (distilled
water and salt, NaCl) and a solution was obtained. The soil samples were
sprayed with the prepared solutions while being rotated in a small
electric mixer. Irrigation water of the specified concentration was
prepared in the one gallon water reservoir by adding predetermined
amounts of salt (NaCl) to distilled water.
Prepared samples with known salt and water contents were placed in
the sample containers in one-half inch layers and compacted to a bulk
density of 1. 36 i 0. 06 gm/cm3 with a special device (0. 5 inch thick
plastic disk, 5.0 inch diameter, 9.0 inch long handle). This process
continued until the 6. 0 inch thick samples were prepared. The con-
tainers with the samples were placed under the rotating applicator
85
-------
disks and specific amounts of irrigation water from the reservoir with
known concentrations were applied. Water collected under a suction
of one-third atmosphere was removed at specified intervals to measure
effluent conductivity.
The amount of salt entering any sample was determined from the depth
and concentration of water applied. The amount of salt leaving the
sample was calculated from the depth of water collected and its con-
centration. The leaching factor was then determined from Equation [27].
Experimental Results. Leaching factors for various effluent ratios
were determined for the soil samples under different initial moisture
content and concentration ratios. Samples were prepared according
to the procedure outlined previously. Initial moisture content levels
of 0. 20, 0. 15, and 0. 05 were investigated with varying concentration
ratios.
Soil samples with an initial moisture content (volumetric) of 0. 20 were
prepared in 6. 0 inch layers. Irrigation water concentrations, C , of
C
1. 00 and 2. 00 mmho/cm were prepared in one gallon water reservoirs.
Soil water concentrations, C , of 3. 00, 4. 00 and 6. 00 mmho/cm were
o
obtained by adding precise amounts of salt (NaCl) to the soil samples.
Four different experiments were conducted with varying concentration
ratios as shown in Table 9.
Table 9. Concentrations (EC in mmho/cm) used to determine LF.
Experiment
A
B
C
D
C
e
2. 00
2.00
2.00
1.00
C
o
3.00
4.00
6.00
4.00
C 1C
o e
1.50
2.00
3.00
4.00
Leaching factors were determined for various effluent ratios using
Equation [27] from the depth and concentration of water entering and
leaving the soil sample, as well as the concentration and amount of
water in the soil sample. The results are summarized in Table 10.
86
-------
Table 10. Leaching factor for various effluent ratios (Mesa sandy
loam, 6. 0 inch samples) for initial moisture content
of 0. 20 (volumetric).
Leaching Factor, (LF)
Vdfm
0.1
0.2
0.3
0.4
0.5
0. 6
0.7
0. 8
0.9
1.0
1.25
1.50
1.75
2.00
2.25
2.50
2.75
3.00
A
0. 081
0. 140
0.223
0.275
0. 313
0. 365
0. 391
0.430
0.467
0.500
0. 555
0. 590
0. 651
0. 680
0.702
0.710
0.752
0.750
B
0.085
0.148
0.201
0.261
0.308
0.347
0. 378
0.421
0.452
0.478
0.550
0.610
0. 653
0. 678
0.713
0.725
0.761
0.771
C
0.087
0.143
0.188
0.280
0.291
0. 302
0.381
0.418
0.458
0.473
0.543
0. 603
0. 654
0.682
0.715
0.741
0.771
0.793
D
0.081
0. 141
0. 196
0.270
0.291
0.348
0. 391
0.420
0.461
0.481
0.565
0. 622
0. 650
0.683
0.721
0.764
0.765
0.791
Average
LF
0.084
0.143
0. 195
0.272
0. 303
0. 353
0. 394
0.422
0.462
0.483
0. 553
0. 606
0.652
0. 681
0.713
0.735
0.762
0.776
A: The case where C = 2. 00 mmho/cm, C = 3. 00 mmho/cm
e o
concentration ratio = 1.5
B: The case where C = 2. 00 mmho/cm. C = 4. 00 mmho/cm
e o
concentration ratio = 2. 0
C: The case where C =2.00 mmho/cm, C = 6. 00 mmho/cm
e o
concentration ratio = 3. 0
Dr The case where C =1.00 mmho/cm. C =4.00 mmho/cm
e o
concentration ratio = 4. 0
87
-------
Soil samples with initial moisture contents (volumetric) of 0. 15 and 0. 05
were prepared as above in 6. 0 inch layers and the same four experiments
listed in Table 9 were conducted. The results are summarized in Tables
11 and 12.
The experimental results presented in Tables 10, 11, and 12 giving the
leaching factors in terms of dimensionless effluent ratios under varying
initial boundary conditions revealed the following:
1. The leaching factor for the same effluent ratios did not change
substantially with the same initial moisture content for
varying concentration ratios. However, it must be empha-
sized here that this consistency may only apply to the parti-
cular soil samples (6.0 inch layers prepared according to
the procedure outlined previously) and the concentration ratio
ranges considered.
2. The leaching factor for the same effluent ratios and concen-
tration ratios varied substantially with the initial moisture
content. Relatively large differences between the leaching
factors were observed with low effluent ratio values and
smaller differences were observed for increasing effluent
values.
3. The effluent concentrations leaving the soil samples approached
the concentrations of the applied water when the effluent
ratios approached the value of 3.0. It was also observed that
for an effluent ratio of 0. 1 or less the concentration leaving
was approximately equal to the initial concentration of the
soil water.
In Figure 8 data points are shown for the average leaching factor given
in Tables 10, 11, and 12 versus the effluent ratio for soil samples
with the three different initial moisture contents. The curves in
Figure 8 are calculated from the leaching factor function explained
in the following. Similar leaching factor curves may be obtained for
any other soil by following the procedure outlined above. The slopes
and the degree of variation in the leaching factor curves will vary from
soil to soil depending upon soil structure, texture, and other pertinent
variables. The average values of LF were used in preparation of
Table 1. Thus, Table 1 contains the summary of the leaching factor
determinations upon which the leaching factor function was developed
as a subroutine to the computer programs for the simplified model.
88
-------
Table 11. Leaching factor for various effluent ratios (Mesa sandy
loam, 6. 0 inch samples) for initial moisture content of
0.15 (volumetric).
Leaching Factor, (LF)
Vdfm
0.1
0.2
0.3
0.4
0.5
0. 6
0.7
0.8
0.9
1.0
1.25
1. 50
1.75
2.00
2.25
2. 50
2.75
3.00
A
0.115
0.186
0.250
0. 311
0. 371
0.395
0.442
0.460
0.483
0.517
0.573
0.620
0.661
0.705
0.734
0.755
0.769
0.791
B
0.128
0.196
0.266
0. 317
0.372
0.383
0.440
0.466
0.486
0.522
0.570
0. 623
0.665
0.704
0.734
0.758
0.773
0.795
C
0. 109
0.207
0.261
0.301
0.368
0.393
0.439
0.461
0.491
0.522
0.571
0. 622
0.660
0.700
0.735
0.756
0.762
0.793
D
0. 118
0. 179
0.267
0. 319
0. 364
0.401
0.442
0.455
0.482
0. 515
0.572
0.619
0. 661
0. 701
0.725
0.759
0.779
0.791
Average
LF
0. 118
0.192
0.261
0. 312
0.359
0.393
0.441
0.461
0.485
0.519
0.572
0. 621
0.662
0. 702
0. 733
0.757
0.771
0.793
A: The case where C = 2. 00 mmho/cm, C =
concentration ratio =
B: The case where C =
e
concentration ratio =
C: The case where C =
e
concentration ratio -
D: The case where C =
e
concentration ratio =
1.5
2. 00 mmho/cm, C
c
2.0
2. 00 mmho/cm, C
3.0
1.00 mmho/cm, C
4.0
3. 00 mmho/cm
4. 00 mmho/cm
6. 00 mmho/cm
4. 00 mmho/cm
89
-------
Table 12. Leaching factor for various effluent ratios (Mesa sandy
loam, 6. 0 inch samples) for initial moisture content of
0. 05 (volumetric).
Leaching Factor, (LF)
d,/d
1 fm
0.1
0.2
0.3
0.4
0.5
0. 6
0.7
0.8
0.9
1.0
1.25
1. 50
1.75
2. 00
2.25
2.50
2.75
3.00
A
0. 198
0.276
0.303
0.365
0.411
0.430
0.461
0.494
0.519
0.540
0.587
0. 631
0.679
0.723
0.742
0.761
0.788
0.798
B
0.205
0.272
0.300
0.375
0.413
0.433
0.458
0.499
0.522
0.543
0. 582
0. 640
0.681
0.715
0.743
0. 760
0.791
0. 804
C
0.204
0.274
0.308
0.357
0.407
0.435
0.461
0.487
0.520
0.541
0.581
0. 630
0.680
0.725
0.738
0.769
0.782
0.794
D
0.199
0.277
0.301
0.361
0.416
0.428
0.464
0.496
0.518
0.541
0.596
0.630
0.682
0.712
0.747
0.760
0.787
0.796
Average
LF
0.201
0.275
0.303
0.365
0.412
0.432
0.461
0.495
0.520
0.541
0.586
0. 633
0.681
0. 719
0.741
0.763
0.787
0.798
cm
cm
A: The case where C = 2. 00 mmho/cm, C = 3. 00 mmho/
e o
concentration ratio = 1.5
B: The case where C = 2. 00 mmho/cm, C ; = 4. 00 mmho/
e o
concentration ratio = 2.0
C: The case where C = 2. 00 mmho/cm, C = 6. 00 mmho/cm
e o
concentration ratio = 3.0
D: The case where C = 1. 00 mmho/cm, C = 4. 00 mmho/cm
e o
concentration ratio = 4. 0
90
-------
U
o
u.
o>
c
JC
o
o
0>
Effluent Ratio, ER
Figure 8. Measured values (points) of leaching factor at three initial moisture contents compared
with curves calculated from the leaching factor function.
-------
Leaching Factor Function. In working with the data of Table 1, it was
found that a logarithmic plot could be used to produce a family of curves.
First, a function of the form
In y = b + b In x + b (In x)2 + b. (In x)3 + b /x [113]
L £ 3 TJ 3
in which y is the leaching factor (LF) and x is the effluent ratio (d,/df ),
was used to fit the data of Table 1. In order to produce a family of non-
intersecting curves slightly different fitting points were used, a total of
20 fitting points were used for each initial moisture content. For
0=0. 05, the measured LF at effluent ratios of 0. 3, 1. 25, and 3. 0 were
o
omitted and LF values of 0. 854, 0. 885, 0. 900, 0. 905, 0. 915 were used
for effluent ratios of 4, 5, 6, 7, and 10, respectively. For 9 =0.15,
all measured data of Table 1 were used as fitting points and in addition
LF values of 0. 867 and 0. 890 were used for effluent ratios of 6 and 10,
respectively. For 0=0. 20, all measured values were used and LF
values of 0. 860 and 0. 890 for effluent ratios of 6 and 10, respectively,
were added.
Each of the coefficients, b through b , inclusive, of Equation [113] may
be thought of as functions of 0 . To complete the family of curves, a par-
abola of the form
2
b. = a.. + a._0 + a.. (0 ) , i = 1,2, . . ., 5 [114]
i il i2 o i3 o J
was fit through each set of b vs 0 data (i = 1, 2, . . ., 5). That is, the
coefficients a., were determined so that Equation [114] passed exactly
J .
through each b vs 9 point. The resulting 5 by 3 matrix of a., values is
contained in the LF function subroutine (see the FORTRAN listings in
Appendix A). For example with i = 1, b has the values -0. 55492, -0. 66130,
and-0. 86851 for© equal to 0. 05, 0.15, and 0. 20, respectively. The final
o
result was a non-intersecting family of curves with 0 as a parameter.
In the final family, the curves resulting from Equation [113] were used
for effluent ratios in the range, 0. 2 < x < 3. For x < 0. 2 and xj> 3,
straight lines on the logarithmic plot were used (Figure 9). The
92
-------
sD
OJ
1 1 1 1 I I I |
I 1 I I I I I I
.01
Figure 9.
.02
.04 .06 O.I
.2 .4 .6
Effluent Ratio, ER
1.0
Logarithmic plot of leaching factor vs effluent ratio used to develop the leaching factor
function showing measured values (points) compared to curves calculated from the
resulting leaching factor function.
-------
equations were
b
y = b, x (x < 0. 2) [115]
6
and
bg
Y =bgx V (X> 3) [116]
Coefficients, b, through b , in Equations [115] and [116] were determined
so that the straight lines were tangent to the curves of Equation [113]
for each initial moisture content at effluent ratio values of 0. 2 and 3.
Details for determining the coefficients b, through b are given as
follows: Note that Equation [116] can be written in the form
In y = In b + b In x
which is the slope intercept form of the straight line on a logarithmic
plot. Since b is the slope of the straight line, it must equal the slop(
of Equation [113] at x = 3. The slope of Equation [113] is
In x + 3b4 (1. x)2 - b5/r
Thus
d (In y)
*9 " d(lnx)
+ 2b3 In 3 + 3b4 (In 3)2 - bg/3
x = 3
and
bg =
in which y is the value of the leaching factor from Equation [113] for
x = 3. In the computer routine, whenever Equation [116] calculated a
leaching factor value greater than 1, the leaching factor was set equal
to 1.
94
-------
Simplified Model
Field data for testing the simplified model were collected during the
1971 irrigation season in which the crop was alfalfa. The evaluation
version was used for comparison of computer model calculations with
field measurements. In order to use the prediction version, the compu-
ter model would have to be run for the entire season to determine an
irrigation schedule. Then all field work would have to be conducted
according to this schedule. Maintaining a strict schedule in the field
would have been difficult. The irrigation water was not available on
a strict demand nor was its quality accurately predictable. An accurate
forecast of daily evapotranspiration could not be made at the beginning
of the season. A reasonable overall schedule of field work was devel-
oped, including the irrigation schedules outlined in Tables 3 and 4.
Data were collected for testing the simplified model.
Data and Input Preparation
Because of reseeding the alfalfa in the spring of 1971 rather frequent
irrigations were used until the first cutting. On June 22 soil samples
were taken and the data furnished the initial conditions for the model.
Soil samples were also taken on August 3 and September 9 to compare
with calculated results on these dates. The samples were analyzed in
the laboratory to determine the moisture content gravimetrically and
the electrical conductivity of the saturation extract, EC (Table 44,
Appendix C).
The moisture content data from the soil samples were not used because
they did not appear to be reliable. In order for the moisture content
from soil samples to have been the same as determined by the neutron
meter, the bulk density of the soil would have to have been as high as
2. 0 in some locations. The difference may have been due to the small
size of the soil cores and loss of moisture from the samples while
they were in storage for several months. Consequently, the volumetric
soil moisture content (9) as determined by the neutron meter on the
same days that the soil samples were taken was used in testing the
model (Table 13).
Inspection of the EC data indicated the probability that no change in
t?
salt content of the soil occurred during the season. This was confirmed
by statistical analysis of the data for the top one foot of the soil profile
(Table 14). Analysis of variance showed no significant differences at
95
-------
Table 13. Volumetric moisture content (9) measured by neutron meter
on dates of soil sampling.
June 22
August 3
September 9
Depth
(inches)
12
18
30
42
54
66
12
18
30
42
54
66
12
18
30
42
54
66
Block 3
.236
.274
.273
.332
. 336
.409
. 303
.311
. 302
. 320
.401
.329
.324
.323
.351
.414
Block 5*
.200
.248
.238
.274
.327
.396
.252
.276
.264
.294
.385
.414
.275
.288
.280
.313
.389
.411
Block 6
.226
.298
.293
.366
.411
.418
.295
.323
.346
.406
.411
' .299
.337
.391
.400
Block 7
.231
.243
.289
. 363
.416
.409
.242
.249
.354
.396
.410
.282
.290
.363
.383
.406
* Average of 6 sites
the 10 percent level between the means of EC values for the three
sampling dates (Table 15). It is probable that analysis of data from
any other soil depth increment would yield similar results because of
the large differences between values for a given block and sampling
time.
Examination of data from the top one foot of soil reveals even more
information because it is the only zone that consistently receives the
same treatment within a given block; i. e., the same depth and concen-
tration of irrigation water is theoretically applied to all sites within
each block. Therefore, when the soil at two sites within a block has
the same EC value at a given time, the values should also be similar
e
when checked at a later time. Table 14 shows the variation which
96
-------
Table 14. EC of the top one foot of soil at six sites within each irri-
e
gation block as determined from soil samples taken on
June 22, August 3, and September 9.
Site
Block 3 NW
NE
MW
ME
SW
SE
Block 5 NW
NE
MW
ME
SW
SE
Block 6 NW
NE
MW
ME
SW
SE
Block 7 NW
NE
MW
ME
SW
SE
EC (mmho/cm)
e
June 22
1.43
1.98
1. 98
3.43
2. 00
2. 30
0.99
1.25
1.45
1.84
1.66
1.63
2.81
1.24
3. 30
5.16
0.94
3.25
2.80
2.66
4.14
3. 04
3.35
2.88
EC (mmho/cm)
e
Aug. 3
2.70
1.78
2.45
1.79
2.12
1.43
1.34
1. 33
1.53
3.41
2.79
2. 72
2. 64
2. 94
2.77
1.37
3.06
2. 64
3.03
2.91
8.40
2.70
EC (mmho/cm)
e
Sept. 9
2. 98
1. 60
1.21
1.24
1.19
1.52
1.20
1.44
1.24
1. 65
1.73
1.00
2.85
4. 61
1.45
1.82
4. 13
3.68
3.37
3.33
3. 05
3. 15
3. 83
2. 18
97
-------
Table 15. Analysis of variance for EC of soil samples from the top
e
one foot of soil taken on June 22, August 3, and September 9.
Source of
Variation
Degrees of
Freedom
Mean
Squares
Block 3
Time of sampling
Experimental error
Total
2
14
16
0.598
1.091
1.029
0.548*
Block 5
Time of sampling
Experimental error
Total
2
15
17
0. 614
0.327
0.361
1.877*
Block 6
Time of sampling
Experimental error
Total
2
15
17
0.391
1.460
1.334
0.268*
Block 7
Time of sampling 2
Experimental error 14
Total 16
1.095
1.998
1.885
0.548*
*Not significant at 1 0 percent level
actually existed at such sites. For example, on June 22 the EC at
sites Block 3 NE and MW was 1. 98 mmho/cm. However, on August 3
the EC had decreased at Block 3 NE to 1.78 mmho/cm, and increased
at Block 3 MW to 2.45 mmho/cm. This illustrates the differences, that
exist between what is expected theoretically and what occurred under
this experimental procedure. The reasons for the differences probably
include taking samples from slightly different locations at a site,
nonhomogeneous soil within blocks, lack of uniformity of irrigation
water application, and inaccuracy of the laboratory method for deter-
mining EC .
98
-------
Although it could not be shown that changes occurred in the salt content
of the soil profile during the season, this did not prevent the accom-
plishment of the objectives of the study. It was assumed that if the
model to be evaluated was adequate, it would predict that there would
be no significant changes, in accordance with the measured field
conditions. Also, regardless of any difficulties that may have existed
with respect to the field data representing the salinity status of the soil
profile, sufficient information was available to evaluate the ability of
the model to predict water movement. This was especially true of
Block 5, where there were six access tubes from which moisture content
of the soil profile was determined by the neutron probe.
The shortest interval of time used in the simplified model is one day
(24 hours). Daily ET during the growing season was obtained by
averaging data from two lysimeters (Table 34, Appendix C). The period
of measurement for ET was from 8 a.m. of one day until 8 a.m. of the
next day. The data of Table 34 are recorded on the date of ending of
the 24-hour measurement period. In the simplified model, if irrigation
occurs on a given day, the ET of that day is included in the interval
following the irrigation. Since the major part of the measured ET
occurred during daylight hours, for testing the simplified model, the
daily ET was assigned to the date of beginning of the 24-hour measure-
ment period. For example, in testing the simplified model, the ET of
0. 84 cm recorded for May 1 5 in Table 34 was used for May 14, etc.
Electrical conductivity (EC) of irrigation water was usually measured
(Tables 16 through 20). Where no measurement was available an
estimate was made, based on measurements taken close to the time of
that irrigation. The range in measured EC of irrigation water during
the season was 0. 80 to 1. 30 mmho/cm. Rain water was assumed to
have an EC of 0.01 mmho/cm. Tables 16 through 20 show the schedule
of irrigations as they actually occurred in the field.
Selection of input values of the wilting percentage and recommended max-
imum EC for each soil layer was arbitrary since these values were
s
used only for comparison purposes. A volumetric moisture content of
0. 08 (15-bar water content) was assumed for the wilting point of the
soil on the experimental farm. Recommended maximum EC values
were chosen arbitrarily as 4, 5, 6, and 7 mmho/cm for soil layers
1, 2, 3, and 4 respectively. For the deeper layers where there was
assumed to be no moisture extraction by plant roots, 100 mmho/cm
was input.
99
-------
Table 1 6. Irrigation schedule and depth and EC of irrigation water for
Block 3 during the evaluation period.
Date
of
Irrigation
June 22 #
June 28
July 2
July 5
July 9
July 12
July 16
July 20
July 23
July 27
Aug. 3#
Aug. 13
Aug. 16
Aug. 30
Sept. 8
Sept. 9#
Length of
Irrigation
Interval
(days )
(6*)
4
3
4
3
4
4
3
4
(8*)
17
(9*)
3
14
9
(2*)
Depth
Applied
(inches)
3.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.25
3.75
5.50
.48**
EC of
Irrigation
Water
(mmho/cm)
1.27
1.29
.80
.98
.86
1.05
.94
1.30
1.00
1.20
1.21
.86
.01
# Date of soil sampling
* Days between soil measurements and irrigation
Rain
100
-------
Table 17. Irrigation schedule and depth and EC of irrigation water for
Block 4 during the evaluation period.
June 22 #
Aug. 3#
Sept. 9#
Date
of
Irrigation
June 28
July 5
July 12
July 19
July 27
Aug. 14
Aug. 28
Sept. 8
Length of
Irrigation Depth
Interval Applied
(days) (inches)
(6*)
3.00
7
2.00
7
2.00
7
2.00
8
2.00
(8*)
18
4.00
14
4.00
11
. 48**
(2*)
EC of
Irrigation
Water
(mmho/cm)
1.27
.80
.86
.94
1.00
1.20
.85
.01
# Date of soil sampling
* Days between soil measurements and irrigation
** Rain
101
-------
Table 18. Irrigation schedule and depth and EC of irrigation water for
Block 5 during the evaluation period.
June 22 #
Aug. 3#
Sept. 9#
Date
of
Irrigation
June 29
July 10
July 20
July 29
Aug. 18
Aug. 30
Sept. 8
Length of
Irrigation
Interval
(days )
(7*)
11
10
9
(6*)
20
(14*)
12
9
(2*)
Depth
Applied
(inches)
3.00
3.00
3.00
.83
4.00
3.00
.48**
EC of
Irrigation
Water
(mmho/cm)
1.27
.98
1.53
1.00
.94
. 86
.01
# Date of soil sampling
* Days between soil measurements and irrigation
** Rain
102
-------
Table 19. Irrigation schedule and depth and EC of irrigation water for
Block 6 during the evaluation period.
June 22 #
Aug. 3#
Sept. 9#
Date
of
Irrigation
June 30
July 13
July 23
July 28
Aug. 15
Aug. 24
Aug. 31
Sept. 8
Length of
Irrigation
Interval
(days)
(8*)
13
10
5
(7*)
18
(11*)
9
7
10
(2*)
Depth
Applied
(inches)
3.00
3.25
.75
4.00
2.00
2.00
2.00
. 48**
EC of
Irrigation
Water
(mmho/cm)
1.29
.86
1.30
1.00
1.20
.84
1.23
.01
# Date of soil sampling
* Days between soil measurements and irrigation
** Rain
103
-------
Table 20. Irrigation schedule and depth and EC of irrigation water for
Block 7 during the evaluation period.
June 22 #
Aug. 3#
Sept. 9#
Date
of
Irrigation
June 30
July 7
July 18
July 29
Aug. 15
Aug. 18
Aug. 24
Aug. 29
Sept. 1
Sept. 8
Length of
Irrigation
Interval
(days)
(8*)
7
11
11
(6*)
17
(11*)
3
6
5
3
7
(2*)
Depth
Applied
(inches)
3.00
.50
5.62
.83
1.00
1.00
1.00
1.00
.75
. 48**
EC of
Irrigation
Water
(mmho/cm)
1.29
. 80
.94
1.00
1.21
.94
.84
.86
1.23
.01
# Date of soil sampling
* Days between soil measurements and irrigation
** Rain
104
-------
Because the computer program requires the input of the electrical
conductivity of the soil solution (EC ), it was necessary to convert the
S
EC data to this form. Assuming homogeneous field soils within a
e
given irrigation block, the volumetric moisture content under saturated
conditions in the field was estimated from, neutron meter readings. The
field bulk density was then calculated from the values using the particle
3
density of 2. 65 gm/cm . The bulk density values for irrigation Blocks
3, 5, 6, and 7 were found to be 1. 43, 1.56, 1.56, and 1.55, respectively.
Using the values of bulk density, the volumetric moisture contents from
the neutron meter at the three dates of soil sampling were converted to
moisture content by weight, W. Then EC was computed from
S
w
EC = —- EC
s W e
where W is the moisture content by weight at saturation of the sample
used to obtain the extract. The average EC and W values for each
soil layer and irrigation block were used in the calculations. These
averages and the corresponding calculated values of EC and values
of 9, which were used in testing the model are given in Table 44,
Appendix C.
Six-inch soil layers were used for testing the model since the laboratory
soil samples used to establish the leaching factor function were 6-
inches thick. The number of soil layers considered for each irrigation
block was determined on the basis of piezometer readings made through-
out the period. Determining the average depth to the water table made
it possible to consider only the unsaturated zone in the calculations.
This permits the calculation of the amount of salt entering the saturated
region and increasing the groundwater salt load as well as becoming
a potential pollutant to receiving streams.
The root distribution for the alfalfa on the experimental plot was esti-
mated by analyzing soil samples for carbon content. It was concluded
that the moisture extraction for 6-inch intervals from the soil surface
to a depth of 2 feet was 41%, 30%, 19%, and 10%, respectively.
Moisture content profiles determined from neutron probe readings
made at various time intervals after irrigations were used to establish
values of 9, in each soil layer of each block. Figure 10 illustrates
fm
105
-------
Moisture Content, 6
0>
<
1
2
3
4
5
6
7
•
8
9
10
II
3 O.I 0.2 0.3 0.4 0.5
. i i i i i
1 ,1—
33.5 Hours
After Irrigation \
\
\
\
{
!-
\
1
9.5 Hours
After Irrigation
[i
i
L
Qfm
\
\
11
1
Figure 10. Upper limit of field moisture, 9 , in each soil layer in
Block 5 as determined from moisture content measured
9. 5 and 33. 5 hours after an irrigation ended (measured
values are averaged from 5 locations).
106
-------
the method used. Moisture content profiles are shown as measured 9. 5
and 33. 5 hours after an irrigation ended on Block 5. It was assumed
that downward drainage had essentially ceased in the upper part of the
profile after 33. 5 hours, since further moisture loss could be accounted
for as ET. Part of the moisture loss in the upper part of the profile
was accounted for in the measured ET of 0. 20 inch during the 24-hour
period between measurements with the neutron probe. The rest of the
moisture loss in the upper part of the profile showed up as increase of
moisture content in the lower part during the 24-hour period. Even
after 33. 5 hours, downward drainage appears to be occurring in the
lower part of the profile. Root extraction of moisture was determined
to be negligible in the lower part of the profile. The moisture content
after 9. 5 hours was taken as 9 for the lower part of the profile since
im
it was considered to be closer to the equilibrium condition. The upper
limit of field moisture for the other blocks was determined by the same
method but with less extensive data. The values of 9 that were used
fm
to test the simplified model are shown in Table 21.
Table 21. The upper limit of field moisture (9 ) for each soil layer
and irrigation block.
Soil
Layer
1
2
3
4
5
6
7
8
9
10
11
3
. 338
.338
.338
.338
.338
.341
.347
.365
.395
.415
.425
Irrigation
5
.311
.311
.311
.311
.311
.319
. 330
.351
.385
.406
.415
Block
6
. 330
.330
.330
.334
.342
. 360
.388
.404
7
.311
.311
.311
.311
. 342
.360
.388
.404
107
-------
Model Results
Results obtained by using the simplified model on Blocks 3, 5, 6, and
7 are shown on Figures 11 through 14. The moisture content, 9, and
electrical conductivity of the soil solution, EC , for each soil layer
s
are shown for input values on June 22 and for measured and calculated
values at the two checkpoints (August 3 and September 9). The computer
output for Block 5 is included in Appendix A as Example 3.
Water Movement. In comparing the predicted and measured moisture
contents, it should be kept in mind that the model assumed no moisture
extraction by plant roots below the fourth layer. Therefore, once 9
or any lesser moisture content was reached below this layer, the
moisture content was never less than this value. All layers must reach
9 before any water enters the saturated zone.
fm
At only three of the eight checkpoints included in the four blocks were
all layers at 9 . These were for Block 3 (Figure lib) and Block 6
fm
(Figures 13 a and 13b). From the computer output it was found that
this condition resulted when only 3 of the 38 irrigations applied on the
four blocks resulted in water entering the saturated zone. Two of
these occurred between the first and second checkpoints on Block 3
and one was prior to the first checkpoint on Block 6. This does not
agree with the drain discharge measurements which indicated contin-
uous flow during the test period from Blocks 6 and 7, and occasional
flow from Block 5.
It must therefore be concluded that there was upward movement of
water from the saturated zone which the model could not account for.
This conclusion is substantiated by Table 22 which gives the depth of
water that exists in the unsaturated soil zone which cannot be accounted
for by considering only irrigation water applied and evapotranspiration
during the study period. In computing values of Table 22, loss of water
from the soil profile to the saturated zone was not estimated. If down-
ward drainage was occurring during the periods, then total upward flow
would have been greater than calculated. However, net values of
upward flow as computed in Table 22 would be correct if the applied
irrigation water and ET are correct. A negative value in columns 4
or 5 indicate a net downward movement of water from the soil profile
into the saturated zone.
108
-------
e
0 Qi 02 0.3 0.4 0.5
2
3
M6-22—
_ 8
'5 9
-------
I
2
3
4
5
6
7
8
9
10
I I
e
O.I 0.2 0,3 0.4 0.5
M 8-3
h— C8-3
M6-22
EC s (mmho/cm)
0 2 4 6 8 10
1
2
3
«- 4
>> g
-1 6
"o 7
co 8
9
10
1 I
1
Mill
i
M6-22-
*
I
; u
: r
! — C8-3
i
i
1
|— M8-3
r J
i
i
. i
~
i
i
1
(a)
(O
a>
- 7
-------
e
0 0.1 02 0.3 0.4 0.5
I
2
3
•5 6
to 7
8
9
M 6-22
M8-3
C 8-3
ECS (mmho/cm)
4 6 8 10 12 14
(a)
(O
e
0 O.I 0.2 0.3 0.4 0.5
I
2
^ 3
£4
35
6 6
CA) 7
8
9
i r \
C9-9
M 9-9
(b)
0
7
8
EC (mmho/cm)
8 10 12 14 16
M9-9
(d)
C 9-9
J
Figure 13. Comparison of measured (M) and calculated (C) profiles of moisture content, 9, and
electrical conductivity of soil solution, EC , for Block 6.
s
-------
IN)
e
0 O.I 0.2 0.3 0.4 0.5
1
|3
C3
^i P
-J 5
~ 6
w 7
8
9
• ™
! C8-3-— 1\
VT— M 8-3
vl
; \Y
. M 6-22-Vl '
* \
(a)
©
EC (mmho/ cm)
s
02468 10 12
1 ' I ' ' ' ' ' j '
2 C8.3 (_ !
fe3 : L_
>, 4 • M 8 -3 ' 1
° • , J
5 ' 1
— c ~ 1
° - 1 1
-° 7 M 6 -22-j!
8 L [t
(c)
EC (mmho/cm)
s
0 O.I 0.2 0.3 0.4 0.5 0 2 4 6 8 10 12 14 16 18 2O „ 104 106
1
2
9 3
>» A
O H
-J 5
- 6
to 7
8
9
. ' 'V ' . n '
X 2
1 \ o 4
C 9-9 -L _ ^ - M 9-
**^ w • Ja ^ 1T| *J
L "o 6 .
\ °° 7 .
\| 8[ [
i
i
~~. i
i j
i
9 j
C9-9
r
(b)
(d)
Figure 14. Comparison of measured (M) and calculated (C) profiles of moisture content, 6, and
electrical conductivity of soil solution, EC , for Block 7.
s
-------
Table 22. Net upward movement of water into the soil profile, as determined from total irrigation
water applied, total ET, and soil moisture measurements.
o
•»— I
fc
0)
PU
C5
C^™
•
3 ii
•g H
M W
fl) ^^
C^ TO
s "o
"* H
c
J\ «H
I— 1
*J *"*
S*>o
0 II
* U
bo --J
3 rt
^ j^
< o
H
Block
3
5
6
7
3
5
6
7
(1)
Total
Irrigation
Water
Applied
(inches)
11.00
9.83
11.00
9.95
10.98
7.48
6.48
5.23
(2)
Irrigation
Water
Minus ET
(inches)
2.23
1.06
2.23
1. 18
4. 87
1.37
0.37
-0. 88
(3)
Measured
Increase in
Soil Water
During Period
(inches)
2.63
2. 51
2.52
1. 12
1.50
0.92
0. 57
-1.04
(4)
Net
Upward
Movement
During Period
(inches) *
0.40
1.45
0.29
-0. 06
-3.37
-0.45
0. 20
1.92
(5)
Accumulated
Net Upward
Movement
(inches)
0.40
1.45
0.29
-0.06
-2. 97
1. 00
0.49
1. 86
* Column 3 minus column 2
-------
The calculated moisture content was usually less than measured values
in the upper four soil layers. Such differences could be attributed to
actual upward movement of water in the field which could not occur
in the model. However, part of the difference may be due to not
allowing moisture extraction by ET in the model below the fourth layer.
Figures 11 a, lib, 12 a, and 12 b show situations in which measured and
calculated 9's would agree better if the ET extraction was extended
deeper into the soil profile. That is, if part of the ET came from layers
5 and 6, the calculated 6 would be less in these layers and greater in
layers 1 through 4. Determination of root extraction pattern in the field
is an extremely difficult task. Excavation for new drain construction
in the spring of 1972 revealed numerous plant roots at depths greater
than 2 feet (bottom of layer 4).
The lack of capability of the model to account for redistribution of soil
moisture is emphasized in Figure 14b wherein the calculated 9's of
layers 3 and 4 are considerably less than measured values. This
situation resulted when light, frequent irrigations were applied (see
Table 20). Insufficient water was applied for the model to calculate
any percolation past the second layer into the third or fourth layers in
the period from August 3 to September 9 in Block 7. Consequently,
the moisture was continuously depleted from these two layers by evap-
otranspiration since water could not enter from top or bottom of these
layers in the model. Differences in soil-water potential would obviously
not allow this situation to exist under field conditions.
Figure 13 b illustrates the error that may result from selecting wrong
values of 9. . Layers 5-8 are filled to Q, , yet the measured moisture
fm fm }
content in these layers is greater than calculated. This result cannot
be explained since soil moisture measurements that were used to deter-
mine 9 were made after an irrigation of sufficient depth to fill the
fm
soil to the upper limit of field moisture in all layers. Since the water
table was lower on September 9 than on the day when the 9 values
fm
were determined, the situation could not be reconciled. The situation
shows the importance of selecting the proper values of 9
A fluctuating water table would be difficult to simulate with the simpli-
f::£.d model. The difficulty arises primarily from the influence of water
fible fluctuations on 9^ . A fluctuating water table might be modeled
fm
in two different ways. First, the total season could be separated into
periods in which the water table and 9 values could be considered
114
-------
constant. The computer program could be operated in a stepwise fashion
by inputing the proper values of 9 for each period. The second way
of operating the model would be to use the average water table depths
and constant values of 9 for the entire season. The second approach
fm
was used for the results of this report.
Salt Movement. Since water serves as the transporting medium for the
dissolved salts, any errors in predicting water movement compound the
problems of accurate prediction of salt movement. Figures 11 through
14 show that agreement between calculated and measured EC is generally
s
poor. To minimize the errors in the calculated EC profiles that result
s
from the differences in calculated and measured 9, the moisture extraction
pattern was changed for Blocks 3 and 5 such that the average difference
between measured and calculated 9 at the two checkpoints was equal for
all layers. Table 23 shows the resulting extraction patterns. Extraction
by ET was limited to the top five layers of Block 5. Figures 15 and 16
show the resulting 9 and EC profiles. This exercise showed that the
s
model is not extremely sensitive to errors in the moisture extraction
pattern; i. e. , large changes in percent extraction of a layer are needed
to produce significant changes in moisture content.
Table 23. Percent moisture extracted by plant roots that is required
to match calculated moisture content profiles to corres-
ponding measured profiles.
Soil
Layer
1
2
3
4
5
6
7
8
9
Block
16
16
13
11
11
11
8
8
6
Percent Moisture
Extraction
3 Block 5
40
17
10
11
12
115
-------
From Figures 15 and 16, it appears that the model predicted more
leaching than actually occurred. Salts from the upper layers were
moved downward by the model to a greater extent than actually occurred
according to measurements. The measured values in Figure 15
indicate that the change in EC between June 22 and August 3 and be-
s
tween August 3 and September 9 was due primarily to the increase in
moisture content. The shape of these measured profiles remained
essentially the same. The change in the profile for Block 5 (Figure 16)
cannot be so explained. In this case the profile remained nearly the same
shape (except for layers 5 and 6) but concentrations generally increased
as the moisture content increased between June 22 and August 3.
An effort was made to reduce the predicted salt leaching by making a
change in the leaching factor subprogram. The effluent ratio (ER)
was multiplied by 0. 5 before computing the leaching factor. Figures
17 and 18 show that leaching was reduced but that although calculated
EC profiles were different, agreement between measured and calculated
s
profiles was not significantly improved. Calculations were also made
wherein the effluent ratio was multiplied by 0. 7 and 0. 3 with no better
results. The sensitivity of the model to changes affecting the leaching
factor function is exhibited by this work.
Earlier discussion on data used in the model is significant in the analysis
of the effectiveness of the model to describe salt movement. In addition
to the problems dealing with determining EC , error also resulted from
"
changing values of EC to EC . Perhaps more important is the fact
e s
that with the exception of Block 5, only one moisture content profile
was determined on each of the three sampling dates, and this was at a
different location than where soil samples were taken for EC deter-
e
mination. The correlation between moisture content and concentration
of the soil solution as input to the model and at two checkpoints may
therefore be questioned.
Detailed Model
Water Model
The computer program for the water model (Appendix B) developed from
Equation 45 was used to predict evapotranspiration, soil water flow,
and soil water content profiles as functions of time on the Hullinger
116
-------
e
e
0 Q! 0.2 0.3 0.4 0-5
0 0.1 0.2 0.3 0.4 0.5
2
3
4
fc 5
5 6
7
_ 8
5 9
W 10
I I
M6-22
M8-3
C 8-3
j!
4
3|
7
= 8l
o° sT
!0|"
C 9-9
— M9-9
(a)
ECS (mmho/cm)
ECS (mmno/cm)
8 10
1
2
3
4
fc 5
o 6
*
-1 7
8
•5 9
^ 10
1!
1- ' tl
,n
i i™
t j
•M8-3-i 1
-
* \~ ~
i
i
i
i
l
: e
•••HI
1
/
— -C8-3
— M6-22
1
0
8 iO
w
O
_J
'o
C/5
|
3
6
7
8
9
10
i!
: i ; I i i
- h :
l.
r T
i
r :
„ i .
! ., r* Q-Q
i L/ ;? y
1 1 — 1
. a- j L
r
i
L. ' ,_, -,
!
: ' r
Figure 15.
(b)
Comparison of measured (M) and calculated (C) profiles
of moisture content, 9, and electrical conductivity of soil
solution, EC , after adjusting moisture extraction pattern
s
to minimize differences in calculated and measured 8
profiles for Block 3.
117
-------
e
e
2
3
4
£ 5
o 6
-1 7
_ 8
-5 9
CO
10
I I
0
0.1 0.2 03 0.4 0.5
T 1
M6-22
C8-3
M8-3
(a)
ECS (mmho/cm)
2 4 6 8 10
1
2
3
4
« 5
5 6
7
_ 8
'5 Q
CO y
10
1 1
1 —
•
•
r
T"
i
y
...
— i — i — i
— M 6-22
— C 8-3
1
— M8-3
0 Ql Q2 0.3 0.4 Q5
1 r-
2
3
4
5
8
'o 9
wio
II
C9-9
1
9-9
ECS (mmho/cm)
2 4 6 8 10
M 9-9
(b)
Figure 16. Comparison of measured (M) and calculated (C) profiles
of moisture content, 9, and electrical conductivity of soil
solution, EC , after adjusting moisture extraction pattern
s
to minimize differences in calculated and measured 9
profiles for Block 5.
118
-------
ECe (mmho/cm)
8 10
0
8 10
5,
o
CO
1
2
3
4
5
6
7
8
9
10
1 1
i n i i | i I
. M8-3H
i
-1 C8-3
j I ER=0.5ER
: in
1 r
,1
i
i
- IP
,1 C8-3
No Change
in ER
!L
I
2
3
4
- 7
o
to 8
9
10
M9-9
C9-9
No Change
in ER
C9-9
ER=0.5ER
Figure 17. Measured (M) EC for Block 3 compared with calculated
(C) values resulting from letting ER = 0. 5 ER, ER is
effluent ratio.
0
EC (mmho/cm)
8 10
8 10
1
2
3
- 4
» 5
o
-i 6
_ 7
0 Q
CO °
9
10
1 1
•
1 i • i
C R 3
j 1~ ER-0.5ER 2
! 3
C 8 3
[Tl — No Change % 4
•
J "j in ER ^5
[ J ! -J 6
r -~ - 7
>— M8-3 to 8
T" 9
1
t r
I
i i "~ "
l rPR = OSp-R
r i
i ^^— ^J
i i l
L !J J C9-9
'J [- No Change
u: ln tK
»
1
1
f— M9-9
!
t r
Figure 18. Measured (M) ECg for Block 5 compared with calculated
(C) values resulting from letting ER = 0. 5ER, ER is
effluent ratio.
119
-------
farm. The crops used were oats in 1970, and alfalfa in 1971. Predicted
values were compared to the actual as measured in the field.
The program predictions covered nine days of the 1970 growing season,
and the entire growing season in 1971 for a fixed irrigation interval of
10.5 days. The results show the soil water profiles, evapotranspiration,
drainage, and plant root potential as a function of time.
Input Data Used in 1970 and 1971. The input data used for the computa-
tion are tabulated in Appendix C, Tables 51, 52, 53, and 54. Figures
4 and 5 show the soil properties as determined by Andrade (1971) for
undisturbed samples (data were extrapolated to cover the whole range
of the soil water content). Tables 52 and 53 (Appendix C) also show
the plant root distribution for the two crops.
Figure 19 and Table 54 (Appendix C) show the potential flux at the sur-
face for 1970 and 1971, respectively. The fluxes include the rate of
potential evapotranspiration and precipitation (rain and/or irrigation)
as functions of time for the total time of computation. These data are
the surface boundary conditions needed for the computation. The bottom
boundary condition was a constant pressure head at 165 cm (the water
table).
Results. The program was run for one irrigation interval during 1970
due to the lack of continuous field data for comparison of actual versus
computed data. The computed results of 1970 and 1971 as compared to
the actual measurements are shown in the following order:
1. Soil water profiles at different times of season.
2. Evapotranspiration as a function of time.
3. Water flow through the lower boundary as a function of time.
4. Plant root potential as a function of time.
Soil Water Profiles. Figure 20 shows the actual and computed water
content profiles for oats in 1970. Water contents were measured by
the neutron probe at 30, 45, 75, 105, 135 and 165 cm depth. A linear
relation was assumed to exist between any two depths. For the top
30 cm, the water content at 75 and 30 cm was extrapolated linearly.
This was done because the effective diameter of the neutron probe was
120
-------
0.051
1
X
O
1
-------
0 .1
Water Content (6)
.2 .3 .4 .5 0 .1 .2 .3
.4 .5
20
60
100
140 -
o
£ 180 j.
a.
Q)
O
;
- crop-oats
7/31/1970 (a)
- crop-oats
8/2/1970 (b)
o 20
60
100
140
180.
.8/4/1970 (c)
i i
.8/8/1970 (d)
Figure 20. Comparison of the water content profiles as predicted
(dotted) and measured (solid) for oats in 1970. (a) 24 hrs,
(b) 72 hrs, (c) 120 hrs, (d) 216 hrs
122
-------
more than 30 cm, so no points could be measured between 0 and 30 cm.
The comparison was better when the redistribution stage reached an
end.
For alfalfa in 1971, similar results were reached as shown in Figure
21 for the first crop, Figure 22 for the second crop, and Figure 23 for
the third crop. The results of computed and actual soil water content
showed-excellent agreement, especially after 48 hours of irrigation or
heavy rain.
Figure 24 shows water content with respect to time for alfalfa in 1971
for the entire season of 116 days. The computed values agree very
well at all depths with the measured. The greatest difference was at
30 cm depth. The disagreements at 30 cm occurred mostly after irri-
gation in the redistribution stage. This might be due to the assumption
that there was no hysteresis effect on the soil properties, and/or due
to the nonuniform field soil.
Evapotranspiration. Figure 25 shows a comparison among the computed,
actual and Penman cumulative evapotranspiration (ET) for 1970. The
actual ET was measured from daily readings of two lysimeters installed
in the field, the Penman ET was calculated from Equation [97] using
measured field data. The model computed 4. 9 cm cumulative ET in
1970 which was 0. 4 cm less than the actual ET. This might be due
to two factors:
1. The root distribution was assumed uniformly distributed to
a depth of 30 cm, which is generally not true.
2. The value of Hroot reached the minimum allowable (-15 bars)
at 155 hours where the cumulative computed ET started to
become less than the cumulative actual ET, as shown in
Figure 25. The minimum value allowed for Hroot, -15 bars,
was chosen arbitrarily. Lower values of Hroot -20 or -40
bars would have decreased the difference between cumulative
computed ET and cumulative actual ET. This condition was
considered and details of its effect are discussed in a later
section.
The ratio of actual to potential evaporation (E) seemed to vary with the
irrigation cycle and the stage of growth of the crop (Figure 26). At 938
and 1945 hours, the decrease in the ratio of actual evapotranspiration
(ET) to potential (E) was caused by cutting the alfalfa crop. The ratio
123
-------
O.i
Water convent - 6
0.3 Q5 0.1
20
60
I
100 ' 1\
r L\
\
140 L \
r A
E
o
, 160
_Crop 1 \
May 31,1971 \ (a)
_
JT
m
\tr
T3
.- 20
%
i i 1 1 i i
\
r i
60
100 i
I
140
180
Crop I
June 11,1971
i
U
_Crop I
June 22,1971
(d)
Figure 21. Comparison of water content profiles as measured (solid)
and predicted (dotted) for crop 1 alfalfa in 1971. (a, c)
24 hrs after precipitation, (b, d) end of irrigation interval.
124
-------
Water content - 6
O.I 0.3 0.5 O.I 0.3 0.5
20
60
100
140
o
' 180
_c
Crop 2 V
June 29,1971
I-
i
h
(a)
Crop 2
July 7,1971
(b)
'9 20
60
100
140
180
I Crop 2 \!
i July 10,1971
T i r
I-
(O
_ Crop 2
"July 19,1971
(d)
Figure 22. Comparison of water content profiles as measured (solid)
and predicted (dotted) for crop 2 alfalfa in 1971. (a, c)
24 hrs after irrigation, (b, d) end of irrigation interval.
125
-------
Water content - 6
0.!
20
60
100
I4O
180-
03
Crop 3
Aug. 16,1971
Q.
0>
•D
•5 20
r
60 .
100
140
Crop 3
180 (_ Aug.19,197!
0.5
0.1
0.3
Crop 3
(a) L Aug. 18,1971
(0
_O5
(b)
Crop 3
Aug. 29,1971 (d)
Figure 23. Comparison of water content profiles as measured (solid)
and predicted (dotted) for crop 3 alfalfa in 1971. (a) end
of irrigation interval, (b) 24 hrs after irrigation, (c) 48
hrs after irrigation, (d) end of irrigation interval.
126
-------
0.4
0.3
0.2
01
. (c) 6 at 100 cm depth
^_- -— - ^_^*r"~~^— *— __^
• ^'^ ^^"^ +S~^39-^ ^j** ** •%•
.
1 1 I 1 1 1 1
0.4
0.3
Q 0.2
O.I
c
o
o
. (b) 6 at 70 cm depth
- (a) 9 at 30 cm depth
300
900
1500
Time - hours
2700
Figure 24. Comparison of measured (dots) and predicted (solid lines) water content profiles for
alfalfa in 1971. (a) 30 cm, (b) 70 cm, (c) 100 cm depth.
-------
IN)
oo
O
I
h-
UJ
-------
1.8
I = Irrigation
R=Rain
3
O
>>
O
-C
300
mRLR I Rl
_LJJL-1 I -JJL L
900 1500
Time- hours
R
L..J.
2100
,R RR
I i III
2700
Figure 26. Variation of actual ET/Penman E for alfalfa in 1971.
-------
of actual ET to potential E varied from about 0. 57 to 1. 48 and averaged
about 1.06. The lowest ratios occurred, as expected, after cutting or
early in the season. It was originally intended to use values of the crop
factor (i. e. , the ratio of actual ET to potential E) published for other
regions for estimating ET. This resulted in considerable error in the
computed versus measured values over short periods, although the long
period errors were smaller. Consequently, it was assumed that the
actual ET was equal to the potential ET for the computations to follow
for evaluation of the other predictions other than ET. The irrigation
amount was sufficiently high so that the value of Hroot was always above
the limiting value (Figure 27). Thus, the computed ET should be equal
to the measured ET. This indicates that for detailed estimation of ET,
the use of a generalized crop factor with a Penman type E measure-
ment may be considerably in error even if soil water is not limiting.
Possibly, this is due to underestimation of the influence of advection
by the Penman equation (when the ratio is more than 1). When the
ratio is less than 1. 0 as after cutting there is undoubtedly a plant
factor responsible, and a possible change in the relation of potential
evaporation to transpiration not accounted for in the model.
Flow from/to the Water Table. In the 1970 growing season, only up-
ward flow from the water table occurred in the nine days test interval.
Figure 28 shows that the computed cumulative upward flow added up
to 2. 2 cm which was 0. 1 cm greater than the actual. The actual up-
ward flow was measured by measuring the right hand side components
of Equation [117],
FLOW = AM - I + ET [117]
where AM is the change in moisture content in the field, as measured
by the neutron probe, I is irrigation or precipitation, ET is evapotrans-
piration as measured by the lysimeters, and FLOW is flow through
the lower boundary. If FLOW is positive, the flow through the lower
boundary is upward, otherwise it is downward.
Figure 29 shows the cumulative,flow through the bottom boundary as
compared to the actual for 1971. The actual upward flow was con-
sistently greater than the predicted except at the end of the first crop.
The total actual upward flow was 4. 8 cm as compared to 0. 0 cm pre-
dicted for the entire growing season (116 days). This difference might
130
-------
Time - hours
T-—r^ 69Q
(b) crc; 2
(c) crop 3
Figure 27. Variation of root water potential of alfalfa in 1971. The increase in Hroot is due to
precipitation, (a) crop 1, (b) crop 2, (c) crop 3.
-------
O
I
^(D
.0
O
4L
50
100
Time- iiours
150
o
Figure 28. Comparison of actual (dots) and predicted (solid line) upward flow from the water table
for oats during the 9-day interval in 1970.
-------
10.0
9.0
8.0
„ •—«—• Predicted upward flow (O initialized after each hay cut)
• • Measured upward flow t»
Predicted upward flow (9 initialized at the beginning
of the season)
Time- hours
Figure 29. Comparison of actual (dots) and predicted (solid line) upward flow of water from the
water table for alfalfa in 1971.
-------
be due to the uncertainty of measurement of water content in the top 30
cm of depth was the average for that depth. Figure 29 shows that late
in the season, or at 2400 hours, 19 days before the cut of the third
crop, downward flow to the water table started. This was due to the
larger amount of water applied to induce downward flow. The trends
of predicted and actual data agree during this period.
Root Water Potential (Hroot) at the Surface. Figure 30 shows the var-
iation of Hroot during the nine-day interval for oats. The Hroot reached
-15 bars, which is the minimum allowable beyond which wilting occurs
at 155 hours. Figures 27 and 30 show that Hroot increased when pre-
cipitation occurred, and decreased when the water content decreased
toward the end of the irrigation cycle. In 1971, as shown in Figure 27,
Hroot rarely reached -1 bar; this might be due in part to the greater
depth of the root system for alfalfa as compared to oats in 1 970, but it
was primarily due to increased addition of water. In both years, the
average conditions over the day were used as a boundary condition.
Consequently, predicted changes of Hroot values with time during the
day did not occur. It would be more realistic, but cost more field
and computer time, if the potential ET was varied with time during
the day for both seasons. If this was allowed, the program would be
expected to predict the variations in Hroot values during the day, since
it predicted the variations during the whole season.
Sensitivity of Water Model. The sensitivity of the model to various
parameters was tested by comparison of two soil conditions (A + B).
Most of the tests were conducted for the data from the nine-day
interval in 1970. The pressure potential was varied in these two
conditions as shown in Figure 4. Condition A caused evapotranspiration
and transpiration to be greater than condition B, while the reverse was
true for evaporation and upward water flow. The comparison is tabulated
in Table 24.
The water content profiles were quite different in the active root ex-
traction zone. At the end of the period the water content at 30 cm depth
was about 0. 10 for condition A and about 0.12 for condition B, Figure
31 shows these data. For these computations Hroot fell to -15 bars one
day earlier for condition B than for condition A (Figure 28).
Another test of sensitivity of the model was made using different root
extraction depths of 30, 45, and 60 cm for oats in 1970. Evapotrans-
piration and upward flow from the water table for the 45 and 60 cm root
134
-------
Time - hours
96 144 192
-2 -
-16-
Figure 30. Hroot during the 9-day period as predicted from 30, 45,
and 70 cm root distribution.
135
-------
E
o
a.
-------
extraction were higher than the actual and the 30 cm root extraction.
The results are tabulated in Table 25.
Table 24. Comparison of predicted evapotranspiration, evaporation,
transpiration, and water flow as influenced by different soil
properties for a nine-day period starting July 28, 1970 at
Vernal, Utah (no precipitation).
Condition A
45 cm root depth
Condition B
45 cm root depth
Evapotranspiration
Evaporation
Transpiration
Water flow from the
water table
6. 01 cm
0. 64 cm
5. 37 cm
2. 44 cm
5. 79 cm
0. 77 cm
5. 02 cm
2. 58 cm
Table 25. Comparison of evapotranspiration, upward flow of water
from the water table and Hroot at the end of the nine-day
interval in 1970.
Root depth
Evapotranspiration
(cm)
Upward
water flow
(cm)
Hroot-bars
(end of interval)
30 cm
45 cm
60 cm
Actual
4.9
5.8
5.8
5.3
3.2
2.3
2.7
2.1
-15
-11
- 2
The predicted water content profiles varied from the measured with
the 30 cm root extraction giving best results compared to the measured
as shown in Figure 32. In this test, the flux at the surface was varied.
Potential evaporation was assumed to be 10 percent and 50 percent of
potential evapotranspiration. The program was run for these two
137
-------
0.1
20
40
60
o
80
Q.
O)
Water content - 6
0.2 0.3 0.4
0.5
(8100
i
r
120
i
i
i
measured
30cm root depth
°45cm root depth
t—*-* 70cm root depth
140 U
i
L
i
!60 L
j
t
L
Figure 32. Comparison of measured and predicted water content
profiles at the end of a 9-day period in 1970 assuming
root distribution 30, 45, and 70 cm.
138
-------
conditions and for the three root depths. The results are tabulated in
Table 26. These computations show that ET and upward flow from the
water table are less when E is greatest. The 9 profiles show E = 0. 1 ET
to be the most reasonable.
Table 26. Effect of change in upper boundary condition and root depth
on evaporation, transpiration and upward water flow
(11 days).
Surface flux E = 0. 1 ET E = 0. 5 ET
Root depth - cm
Evaporation
Transpiration
ET
Upward water flow
30
. 62
5.70
6.32
5.43
45
.62
6.37
6.99
6.35
60
.62
6. 37
6.99
7.76
30
2. 68
3. 26
5.94
5. 38
45
2.99
3.58
6.57
5.94
60
2.99
3.58
6.57
6.78
A sensitivity test was run on the data of the 1971 growing season. In
this test, the initial moisture content was reinitialized at the beginning
of each crop as compared to one initial moisture content at the beginning
of the season. The water content profiles were essentially the same,
especially for the first irrigation after cutting in both cases, as shown
in Figure 33. Figure 29 shows the difference in upward flow for both
cases.
Another test of sensitivity of the model was made using data from a
desert soil, where the lower limit for Hroot was varied. The original
soil water content was high simulating spring conditions. Figure 34
shows cumulative ET where the lower limit was allowed to drop to -20
and -40 bars as well as cumulative potential ET. The data show that
cumulative ET at 48 days was 7. 6 cm for the -20 bar limit compared to
8. 3 for the -40 bar limit. The computed data indicated that the lower
limit of Hroot was reached at 24 days for -20 bars and 30 days for -40
bars.
From the last two tests it appears that under irrigated conditions one
initial water content profile is needed at the beginning of the growing
season. And, it also appears that the value chosen for the lower limit
139
-------
20
60
IOO
140
180 .
Water content -• 0
.3 .A _ .1
.(a)Crop 2
June 25,1971
.3
Xb)Crop 2
Aug., 3,1971
0>
20
60
100
140
ISO
I I
Jc) Crop 3
Aug.6,1971
_(d) Crop 3
Sept.8,1971
Figure 33. Comparison of water content profiles as predicted, 9
was initialized after each hay cut (dots), 9 was initialized
at the beginning of the season (solid lines); (a, c) three
days after hay cut, (b, d) at the end of the crop.
140
-------
22
20 -
18
16
i
-APotential ET
~° -20 Bar min allowable for Hroot
-° -40 Bar min allowable for Hroot
10
15 20 25 30 35 40 45 50
Time- days
Figure 34. Cumulative evapotranspiration vs time compared with
predicted evapotranspiration where the lower limit of
Hroot was -40 bars and -20 bars (data for desert soil
from Curlew Valley, Utah).
141
-------
does not make very large differences in ET. Other than these, exact
field conditions and soil properties are needed for the program to
compute comparable results.
Another type of information computed is shown in Figure 35 as the
relative root extraction of alfalfa as function of depth and time after
irrigation. After irrigation, maximum root extraction was near the
surface probably due to high water content there. As time increased
the relative root extraction zone deepened. At about 150 hours, for
all cases shown, the maximum extraction was near the bottom of the
root zone. This was due to a higher water content there maintained
by upward flow from the water table.
Salt Model-Column Experiment
Case #1. Figure 36a is the plot of experimental and predicted soil
moisture distribution after 35. 6 hours of infiltration. Total salt
distribution curves corresponding to the soil moisture distribution
are given in Figure 36b. The predicted water content is slightly
higher than the measured values at depths greater than 40 cm and
vice versa at depths below 40 cm. These differences are probably
due to the hydraulic parameters used in this model which were deter-
mined for an undisturbed soil while in the column the soil was loosely
packed.
Observed and predicted total salt concentration (Figure 36b) have sim-
ilar distribution patterns. The depth at which the maximum concentration
occurs is almost the same in both cases. The concentration of salt in
the upper 18 cm had the same total concentration as that of the irrigation
water. However, below 18 cm there were some differences between
the measured and predicted values. The predicted concentrations were
less than the measured values between 18 and 33 cm while below 33 cm,
the reverse was true. These differences are hard to explain with the
present state of information. One of the reasons for high predicted
salt concentrations below 40 cm is the low predicted water content.
However, the agreement is considered good enough for most purposes.
The comparison of the experimental and predicted concentrations of
individual ions comprising the total salts is plotted in Figure 37. Since
the sulfate and bicarbonate ion concentrations were calculated and not
measured the plot for these ions are not drawn. Calcium and magnesium
142
-------
Relative Root Absorption
.01 .02 03 04 .05 .06 .0! 02 .03 .04 05 .06 .07
70
80-
\
152 hours 70^ x r^
Q0\!.f
(a)
Crop I. Alfalfa 1971
.' X
F-;
i (b)
202 hours
106 hours
— 154 hours
Crop 2. Alfalfa 1971
.0,1 .02 .03 .0,4 .Q5 .Q6 .Q7
90-
(C)
Crop 3. Alfalfa 1971
-86hours
-36 hours
•I 06 hours
•I 57 hours
Figure 35. Relative root extraction of alfalfa as a function of time
after irrigation and depth.
143
-------
10
20
E
o
a.
«>
o
30
40
50
Water content (9)
O.I 0.2 0.3
0.4
(a)
Total salt concentration (meq/l)
90 (80
60 60L
Figure 36. Comparison of predicted (dotted) and measured (solid) water content and total salt con-
centration profiles for conditions of Case #1.
-------
(Jl
Calcium (meq/l)
40 80
o
ex
0>
Q
10
20
30
40
50
60
Magnesium (meq/l)
60 120
Sodium (meq/l)
10 20
Chloride (meq/l)
80 160
\
(a)
(b)
(c)
(d)
Figure 37. Comparison of predicted (dotted) and measured (solid) ion concentration profiles for
conditions of Case #1.
-------
includes the corresponding ions and ion-pairs. Ion-pairs of sodium
ions are assumed to be the same as the total sodium concentration.
In general, both the cations and anions followed the same distribution
as that of total salts. The concentration of each ion increased with
depth and maximum concentration occurred at about 58 cm. Predicted
concentration of calcium, magnesium, and sodium seemed to be in close
correspondence with the experimental values at low salt concentration.
However, there is a significant difference between computed and measured
cation concentrations at total salt concentration greater than 45 meq/1.
This lack of agreement seems to result from the inadequate description
of the cation exchange process at the higher salt concentrations. Since
measured and predicted total salts distribution are in reasonable agree-
ment, it is expected that the cations comprising the total salts also
follows the same trend. This, however, is not true. The predicted
calcium concentration is about 1 . 5 to 2 times greater than its measured
values. Since relative concentration of each cation is controlled by the
exchange coefficient, the above differences seems to be due to inadequate
information concerning exchange coefficients.
It has been assumed in this study that a given exchange coefficient-total
salt concentration relationship holds at all levels of salt concentration.
This assumption is not necessarily true. Since concentration of each
cation at the end of infiltration is affected by the composition of solution
in the early hours of infiltration, the correct values of exchange coef-
ficients seem to be important at high salt concentration in soils.
Another cause for disagreement may be the assumption involving the
activity coefficients. It has been assumed that y = 'Y
(_
-------
10
20
E
u
Q.
-------
water content and total salt distribution at the end of 37. 6 hours of in-
filtration. There is good agreement between the observed and the
predicted water content distributions. However, the measured total
salt concentration is quite different than the predicted values. There
is not any regular increase with depth of the measured total salts.
There is no well defined depth at which maximum concentrations of
total salts occur. This kind of behavior may result from the assumption
that all the salts are soluble at initial soil water content. Since the
salts were applied in the powder form, it seems that some of the salts
were not solublized after the first wetting. Because the water was
applied in drops and manually checked for its uniform application at
the surface, it is believed that these salts eventually became dissolved
at irregular time intervals and led to this type of distribution. There
may also be analysis problems or errors unaccounted for.
Figure 39 gives the distribution of individual ions. Measured concen-
tration of almost all the ions follows the same general distribution of
total salts. There is poor agreement between the measured and com-
puted values for all the ions. The model at its present stage does not
predict adequately the distribution of individual ions in the soil profile.
Case #3. Figure 40 shows the soil moisture and total salt distribution
at the end of the experiment where wetting-drying-wetting cycle was
followed. Agreement between measured and predicted water content
was poor. Measured total salts distribution indicated the presence of
two peaks at about 12 and 52 cm depths, while the model predicted a
single depth (38 cm) at which maximum concentration occurred. It
was expected that all the salts would have moved to the bottom of the
column at the end of the second infiltration. As sodium ions (Figure
41 c) are the major components contributing to the peak in total salt
concentration, at 12 cm depth, it may be that all the NaCl salt added
before the second irrigation apparently did not dissolve immediately
after irrigation, as is assumed in the model.
Salt Model-Field Experiment
The detailed salt model was also tested under field conditions at the
Hullinger farm near Vernal, Utah. Water movement and, thus, the
salt movement due to the presence of roots was also considered. In
order to avoid the complexity arising due to layered soil, the soil
profile was assumed to have uniform properties throughout. Presence
148
-------
Calcium (meq/l)
60 120
10
20 H
a>
Q
Magnesium (meq/l)
40 80
Sodium (meq/l)
20 40
Chloride (meq/l)
80 160
\
Figure 39. Comparison of predicted (dotted) and measured (solid) ion concentration profiles for
conditions of Case #2.
-------
en
O
E
o
Q.
O)
Q
10
20
30
40
50
60^
Water content (0)
0.3 0.4 0.5
Total salt concentration (meq/l)
90 180
Figure 40. Comparison of predicted (dotted) and measured (solid) water content and total salt
concentration profiles for conditions of Case #3.
-------
Calcium (meq/l)
Magnesium (meq/l)
Sodium (meq/l)
Chloride (meq/l)
40
80
40
80
40
80
60
120
o
.
a>
a
10
20
30
40
50
60
(c)
(d)
Figure 41. Comparison of predicted (dotted) and measured (solid) ion concentration profiles for
conditions of Case #3.
-------
of gypsum was considered in the initial conditions below 30 cm depth.
The model was tested over a period of two drying and wetting cycles.
Hysteresis in the hydraulic properties was ignored. Comparison of
the predicted and measured values was made at three different times
in the cycle. Since no measurements of individual ions were made on
the solution samples at field water content, an approximate method
was used to arrive at the concentrations from the saturation extraction
analysis. The method involves the assumption that the individual ion
concentration changes in the same proportion with changing water con-
tent as does the electrical conductivity of the solution. This assump-
tion may not be exactly valid for complex ions and ions which react
with the soils. Since chloride ions do not interact with the soil, it is
expected that the given assumption holds good for chloride.
Figure 42 presents the water content distribution at three different
times during the cycle. There is good correspondence between the
measured and predicted values on the first (Figure 42a) and the third
(Figure 42c) samplings. The poorest agreement is shortly after irri-
gation (Figure 42b) where the computed water flow is not distributed
within the soil as much as the measured. This has been discussed
earlier.
Electrical conductivities of solution at field water content and satura-
tion extract are plotted in Figure 43. The ratio of the two values was
used to correct the saturation extract analysis to get ion concentration
(Figures 44-47) at field water content. For the third sampling
(Figure 44c), the predicted values closely relate to the corrected total
salt concentration. Since the saturation extract analysis represented
an average of 30 cm depth, the corrected concentrations are also
represented by histograms. The depth at which the maximum concen-
tration occurs is the same in measured and predicted distributions.
Figures 45, 46, and 47 give the individual cation distribution. Measured
calcium concentrations are generally less than the predicted values,
while the reverse is true for sodium and magnesium concentrations.
These differences seem to result from the assumption that cation con-
centration changes in the same proportion as does the EC of the solu-
tion. Since the preference of exchanger for the ions of higher valence
increased with dilution of the solution (Helfferich, 1962) it is expected
that the proportionate increase in calcium and magnesium be more
than in sodium. The approximation used to get the ion concentration
at field water content, however, assumes the same dilution effect for
all the cations.
152
-------
Water Content (0)
0.2
0.4
0.2
0.4
0.2
0.4
Ul
E
o
a.
0)
Q
20
40
60
80
100
120
140
160
1801-
(b)
(O
Figure 42. Comparison of predicted (dotted) and measured (solid) water content profiles for alfalfa
(a) 324 hrs, (b) 339 hrs, and (c) 627 hrs.
-------
Electrical conductivity (mmhos/cm)
Ul
a.
a
0
20
40
60
80
100
120
140
160
180
100 200
, |
- \ \
\ ""^s
\ x
" / '''
/ s
1
1
[
/
/
\
\
1
1
1
(a)
100
—I—
200
100
200
(b)
(c)
Figure 43. Comparison of saturation extract (solid) and soil solution (dotted) electrical conductivity
profiles for alfalfa (a) 334 hrs, (b) 339 hrs, and (c) 627 hrs.
-------
Total salt concentration (mtq/l)
un
01
100 200 100 200 100 200
^^ i i "*^
20
40
60
J 80
£ 100
n
«T
a
120
140
160
180
\J
4-
1
/
,-t
[ f
1
v^
^x
1
/
^
i
r
f
1
1
- ! (a)
•
"--^ I1
"^t--— ,
1 '
1 /
y
/\
t /r
. 1
. J
t
-
i
- 1 (b)
_
••=-__ i" - — i
*"^>>.
^\
^)
•'
- V*
- '!
/ 1
k
I
r
i
i
i
- | (c)
Figure 44. Comparison of predicted (dotted) and measured (solid) total salt concentration profiles
for alfalfa (a) 324 hrs, (b) 339 hrs, and (c) 627 hrs. Both the predicted histograms
and continuous curves are shown.
-------
Ul
100
200
Calcium (meq/l)
100
200
100
200
20
40
60
80
E
o
^ 100
£
1" 120
140
160
180
.
-
-
-
-
»
fc
",
rr
)
1
I
I
i
i
i
i
'•>
y
/
/
4 '
K
f
J
--
(a)
,.,
—
-
™
-
-
-
-
•»
1
""H— --
i •»
L ^
y
KJ
I/
!
I
I
i
1
1
i
1
i
(b)
1
,_
.
.
1
~^h\
| "i
V
/J
1
- I
- J
- 1
1
I
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(c)
Figure 45. Comparison of predicted (dotted) and measured (solid) calcium concentration profiles
for alfalfa (a) 324 hrs, (b) 339 hrs, and (c) 627 hrs. Both the predicted histograms
and continuous curves are shown.
-------
Ul
-J
50
100
Magnesium (meq/l)
50 100
50
100
20
40
60
~ 80
100
.*-
o.
o
Q 120
140
160
180
<" \
. X1,
I
I/
- ,<
'I
r
i
ii
i
i
\
N
/
f
1
\
y
\
(o)
T
^ 1
Si
i
-
/
!
_
X
s
X
/
_ /
V
\
{
l\
V1
T~ t
(b)
^ ' '
\
- \
I X
^
XI
\\
!/
r;> J
. /
f i
i/
i
- i
I
i
(c)
Figure 46. Comparison of predicted (dotted) and measured (solid) magnesium concentration profiles
for alfalfa (a) 324 hrs, (b) 339 hrs, and (c) 627 hrs. Both the predicted histograms and
continuous curves are shown.
-------
(J\
00
50
.c
u
0>
Q
20
40
60
80
120
140
160
i«n
J
• ' r
j|
'i (a)
100
Sodium (meq/l)
50 100
->
(b)
;f
j
"
50
100
(c)
Figure 47. Comparison of predicted (dotted) and measured (solid) sodium concentration profiles
for alfalfa (a) 324 hrs, (b) 339 hrs, and (c) 627 hrs. Both the predicted histograms
and continuous curves are shown.
-------
Sodium concentration measured in the saturation extract is also higher
than the computed values while the opposite is true for the magnesium
and calcium concentrations. Since the area under total salt curves
is about the same for both measured and predicted distribution, the
relative concentration of cations depends upon the exchange coefficients
as discussed previously in Case #1.
Chloride concentrations are plotted in Figure 48. It follows about the
same distribution as that of total salts. The agreement between the
measured and predicted chloride concentration is fair. However, the
depth at which the maximum chloride ion concentration occurs is
deeper in the measured than in the predicted distribution. This lack
of agreement may be due to the discontinuous nature of measured
chloride distribution curve.
Figure 49 gives the depth and salt concentration of the drainage water
during this experiment. Since no measurements were made, only
computed values are plotted. It shows the capability of this model
to provide this kind of information, which is useful in devising a
scheme for quality control of irrigation return flow.
159
-------
Chloride (meq/l)
100
200
20
40
60
80
£ 100
"a.
o>
° 120
140
160
180
-
/
I/
/f
Jl
i
V"
— — i, \s ^s
\
1 I
1 .X
X
(a)
••>^.
-
1
f
/I
^
1 V
"^•-1—
j
j,.--
./•'' i
f
y zoo ion ?n
: — i
.X
(b)
^" ~ S '
T|
x'i
• x '
r. •
/I
i /
T
r
i
(c)
Figure 48. Comparison of predicted (dotted) and measured (solid) chloride concentration profiles
for alfalfa (a) 324 hrs, (b) 339 hrs, and (c) 627 hrs. Both the predicted histograms
and continuous curves are shown.
-------
c
o
o
u
0
54
53
C 52
v.
o-
c 51
50
0
100
200
300
400
500
600
700
100
200
300
400
500
600
700
Time (hr)
Figure 49. Predicted drainage and salt concentration of the drainage water over a period of 627 hrs.
-------
SECTION VII
USE OF MODELS FOR
IRRIGATION MANAGEMENT
Irrigation management for water quality control has many important
facets. The major idea upon which the research work of this report
is based is that the soil profile may be used as a salt storage reser-
voir. The goal of irrigation management would be to control the
releases from this salt reservoir while also producing agricultural
crops economically. The simplified model only was tested in this
section although the detailed model could have been used at a much
higher cost in computer time.
Irrigation Water Quality
The quality of the irrigation water supply influences good irrigation
management practices. The question arises as to whether the seasonal
average concentration of salts in applied irrigation water would be
adequate for modeling or whether the concentration must be accurately
known for each irrigation. The simplified model (prediction version)
was used to calculate the depth of water to be applied for each irrigation
(14-day interval) of the season such that EC for each soil layer did not
s
exceed the "concentration constraints" of Table 27. The EC of all
irrigation water was 1. 8 mmho/cm. Results were compared with two
other methods of calculation.
First, the prediction version was operated from irrigation to irrigation,
treating each irrigation interval as a season, so that EC of irrigation
water could vary according to a generally increasing function of time
(Figure 50) or a generally decreasing function (Figure 51). The sea-
sonal average EC of irrigation water was 1. 8 mmho/cm in all cases.
All other conditions of the problem remained the same including the
concentration constraints. Results are given in Tables 28, 29, and 30.
The results of the seasonal average case were nearly the same as those
for the case in which the concentration increased. Only the difference
between the predictions of salt leaving the root zone (Table 29) may
be significant. However, there is a significant difference between the
average concentration case and the decreasing concentration case for
all three output parameters (depth of irrigation water, salt leaving the
root zone, and leaching water). If it is necessary to predict the amount
163
-------
of salt leaving the root zone for each irrigation, it is obvious from the
comparison of the three cases in each table that the use of the seasonal
average is not adequate.
Table 27. Concentration constraints for each soil layer used in
hypothetical problem.
Soil
Layer
1
2
3
4
5
Concentration
Constraint
(mmho/cm)
4.0
4.4
4.8
5.2
5.6
Soil
Layer
6
7
8
9
10
Concentration
Constraint
(mmho/cm)
6.0
6.4
6.8
7.2
7.6
Table 28. Depth in inches of water applied during each irrigation.
Irrigation
Number
1
2
3
4
5
6
7
8
Seasonal
Average
5.83
2.38
5.37
6.04
4.95
4.95
4.60
4.08
Increasing
Concentration
5.83
2.38
5.48
4.81
4.57
5.69
5.73
3.66
Decreasing
Concentration
5.83
6.37
6.68
5.81
4.62
5.26
4.51
3.84
TOTAL
38.22
38.15
42.92
164
-------
3.0
25
2.0
o
E
E
c
o
u
c
o
o
1.5
1.0
0.5 -
0.0
23456
Irrigation Interval Number
8
Figure 50. Generally increasing concentrations of irrigation water in
mmho/cm during the growing season. (The circled values
are the concentrations at each irrigation).
165
-------
3.0
2.5
2.0
I is
O
o
u
c
o
o
1.0
0.5
0.0
2 3 4 ^5
Irrigation Interval Number
8
Figure 51. Generally decreasing concentrations of irrigation water in
mmho/cm during the growing season. (The circled values
are the concentrations at each irrigation).
166
-------
Table 29. Salt leaving the root zone in tons per acre for each
irrigation.
Irrigation
Number
1
2
3
4
5
6
7
8
TOTAL
Table 30. Depth
Seasonal
Average
.00
.00
.57
.71
.23
.43
.52
.52
2.98
in inches of
Increasing
Concentration
.00
.00
.53
.21
.07
.69
.99
.27
2.76
leaching water required
Decreasing
Concentration
.00
1.21
1.07
.62
.10
.58
.48
.40
4.46
for each
irrigation.
Irrigation
Number
1
2
3
4
5
6
7
8
Seasonal
Average
.00
.00
1.87
1.98
.60
.97
1.08
1.05
Increasing
Concentration
.00
.00
1.98
.75
.22
1.71
2.21
.63
Decreasing
Concentration
.00
3.99
3.18
1.75
.27
1.28
.99
.82
TOTAL
7.55
7.50
12.28
167
-------
The second method of calculation for comparison was to use the depth
for each irrigation calculated by the seasonal average EC and the value
of EC of each irrigation from Figures 50 and 51 as input to the eval-
uation version. Results are shown in Tables 31 and 32. If it is
assumed that the values in Table 31 for increasing concentration and
decreasing concentration were actual, then attempting to model these
conditions with the seasonal average EC of irrigation water would result
in overpredicting salt discharge in the first case and underpredicting it
in the second case. Table 32 shows EC of each soil layer at the end of
s
each irrigation interval whenever EC exceeded the concentration con-
straints of Table 27. S
Table 31. Salt leaving the root zone in tons per acre for each irri-
gation when the depth of water applied is input.
Irrigation
Number
1
2
3
4
5
6
7
8
Seasonal
Average
.00
.00
.57
.71
.23
.43
.52
.52
Increasing
Concentration
.00
.00
.50
.57
.18
.35
.44
.47
Decreasing
Concentration
.00
.00
.62
.81
.27
.49
.58
.57
TOTAL
2.98
2.51
3. 34
Admittedly, this exercise was brief and more modeling of various
situations is needed. However, when EC of irrigation water fluc-
tuates substantially, the actual EC of applied water for each irrigation
instead of the'seasonal average should be used in modeling salt
discharges.
168
-------
o
vO
Table 32. Concentration of the soil solution in millimhos per centimeter after each irrigation
interval when the computed concentration exceeded the critical concentration.
Soil
Layer
1
2
3
4
5
6
7
8
9
10
Concentration Irrigation Interval Number
oonsrraxnt 13345678
(mmho/cm)
4.00 5.91 5.63 4.44 4.75
4.40 4.92 5.16 4.63
4.80 5.35 4.86
5.20 5.42
5.60 5.71
6.00
6.40 6.45 6.88 6.63
6.80 7.60 7.65 7.19
7.20 7.55 8.04 7.94
6.05
6.53
6.96
7.54
7.60 7.70 8.05 8.02
Note: Values left of the double line are for the decreasing concentration case, and those right of
the double line are for the case of increasing concentration.
-------
Irrigation Timing
In order to demonstrate the utility of the models for irrigation manage-
ment, 24 separate problems were solved with the simplified model
(prediction version). The 24 problems were designed to include all
combinations of 2 values of irrigation water EC, 3 curves of initial
EC , and 4 curves of concentration constraints. All other data were
s
the same for all problems and are shown in Examples 1 and 2, Appen-
dix A. Table 33 gives the values used for irrigation water EC, initial
EC , and concentration constraints. All 24 problems had the same total
initial salt content of 1. 92 tons/acre, but its distribution in the soil
profile varied. The irrigation season was 121 days long. The 121-st
day was included to make a valid end point for comparison. An
irrigation occurred on the 121-st day with no subsequent ET. Thus
all computer runs for the different intervals between irrigations began
with the same moisture deficit and ended with the soil moisture at 0. .
fm
For the 121-day period, intervals between irrigations of 2, 3, 4, 5, 6,
8, 10, 12, 15, and 20 days were used. A 24-day interval dried the soil
below the wilting point somewhere in the season and hence was not
acceptable.
Figures 52 and 53 show the results of problems ACF and BCF, respect-
ively (see footnote, Table 33) at the end of the 121-day season as a
function of the interval between irrigations (irrigation frequency). Sim-
ilar figures for the other problems are included in Appendix C (Figures
60 - 81). From Figure 52 for irrigation water EC equal to 1. 5 mmho/cm,
it is seen that as the irrigation interval increases, the leaching water
tends toward a nearly constant value. Coincident with the nearly con-
stant leaching water, the salt removed from the root zone tends to level
off as does the total water applied. The salt remaining in the profile
continues to decrease although not very significantly. The important
aspect from a management standpoint is that there is considerable
range of irrigation frequencies over which seasonal results do not
change significantly. Figure 53, for irrigation water EC equal to
2.0 mmho/cm, shows similar results. Although the curves begin high
for short intervals between irrigations, they tend to level off over a
considerable range of irrigation frequencies.
Figures 54 and 55 show the results of problems ACF and BCF, respect-
ively, for each irrigation during the season with irrigation intervals
of 8 and 20 days. Both of these irrigation frequencies are on the level
170
-------
parts of the curves of Figures 52 and 53. Figures 54 and 55 show the
trend of longer intervals releasing salt from the soil profile earlier
in the season than the shorter intervals.
Table 33. Values of irrigation water, EC, initial EC , and concen-
s
tration constraints used in simplified model for solution of
24 problems, (mmho/cm)
Irrigation Water EC
A* B
1. 5
2.0
Soil
Layer
1
2
3
4
5
6
7
8
9
10
11
12
Initial EC
s
_C_
3. 68
2. 83
2.45
2.30
2. 16
2. 16
2. 04
1. 94
1. 94
1.75
1.67
1. 60
D
1. 38
1. 38
1.47
1. 65
1. 80
1. 80
2. 16
2.26
2.26
2.45
2.53
2. 60
Jl
5. 98
4.28
3.43
2. 95
2. 53
2. 53
1. 93
1.61
1. 61
1. 05
0. 82
0. 60
Concentration
_F_
6.00
6. 00
6.00
6.00
6.00
6. 00
6.00
6.00
6.00
6.00
6. 00
6. 00
_G_
5. 00
5. 18
5. 36
5. 55
5. 73
5.91
6.09
6.27
6.45
6.64
6. 82
7.00
Constraints
_H
4. 00
4. 36
4.73
5. 09
5.45
5. 82
6. 18
6. 55
6.91
7.27
7. 64
8.00
_I
3. 00
3.55
4.09
4. 64
5. 18
5.73
6.27
6. 82
7.36
7.91
8.45
9.00
*The letters A through I are used to designate the particular values
used; i. e. , problem ACF uses column A, C, and F, of this table
The above results indicate possibilities for control of drainage water
quality as it leaves the root zone. On a valley-wide basis two possible
alternative modes of management might be: (1) Irrigate different farms
at different frequencies so as to maintain a nearly constant quality of
drainage effluent during the season; or (2) Irrigate all farms at nearly
the same frequency so as to peak the salt discharge at some convenient
time. This peak of salt discharge might be diverted to an evaporation
basin or other suitable salt sink in areas where man-made drainage
systems are extensive.
171
-------
8 r-
9
O
«e
c
o
o
to
Irrigation Water EC= 1.5 mmho/cm
-.60
Salt Existing
Water Applied
Salt Leaving
40
20
a.
«
a
i
0 5 10 15
Interval Between Irrigations (Days)
Figure 52. Season totals of salt existing, salt leaving, water applied, and leaching water as functions
of irrigation frequency for problem ACF.
-------
8
0>
k_
o
<
^
g 4
o
o
CO
Irrigation Water EC= 2.0 mmho/cm
\
Salt Existing
Water Applied
-,60
— Leaching Water J
40
o
c
a.
4)
Q
20
0 5 10 15 20
Interval Between Irrigations (Days)
Figure 53. Season totals of salt existing, salt leaving, water applied, and leaching water as functions
of irrigation frequency for problem BCF.
-------
10
8
o
2
o 0
IS
o
c
H
8
Is
0
I4
Irrigation Water E C = 1.5 mmho/cm
20 Days Between Irrigations
Salt
Remaining
in Profile
Leaching
Water
ET
Salt
Removed
8 Days Between Irrigations
1
20
40 _. tn .60
Time (Days)
(JO
100
10
8
8
120
Figure 54. Results of problem ACF for each irrigation of the season for 8 and 20 days between
irrigations.
-------
01
10
8
6
4
_
*
u
< 2
M
C
o
-
Irrigation
-
—
-
-
_
20 Days
o
"8
o
! 6
u
&
.C
Q. 4
0>
O
«
|2
0
-
-
j^
CO
8 Days
i
0
1"
— i
Water EC= 2.0 m mho/cm
Between Irrigations
Between
20
-
Irrigations
40 T.
M. f r\ M.I*
Salt
Remaining
In Profile
1
-
— Leaching
Water
T
r. Salt
/ Removed
, /
r
-
-
—
-,
n r
-
i
,
1
1
1
. e'o e'o 100 i
* i
-
0
10
8
6
4
2
0
8
6
4
2
0
Figure 55. Results of problem BCF for each irrigation of the season for 8 and 20 days between
irrigations.
-------
More research is needed on how to use the models to develop irrigation
management practices which will exercise control over quality of irri-
gation return flow. The examples presented indicate that results are
very site-specific and that broad generalizations are difficult if not
impossible to make.
Considerable further work is needed in order to predict the fate of the
water after it leaves the root zone until it arrives as return flow in
the stream or groundwater body. Study must be given to factors such as
residence times, travel paths, degree of mixing with groundwater
underflow before full evaluation can be made of managing irrigation to
achieve water quality control. It is evident from the work on control
in the root zone that very sophisticated irrigation systems capable of
precise control over depth and timing of irrigation are necessary. Such
systems do exist but are rather expensive. For full benefit efficient
drainage systems having short residence times and capable of flexible
control are also deemed necessary.
176
-------
SECTION VIII
SUMMARY
Two basically different models were developed for predicting the
movement of water and salt through the root zone of growing crops.
The two were termed "simplified" and "detailed" models for the pur-
poses of this report.
Simplified Model
The simplified model is basically a unit cell mixing model. Long-term
drainage and upward movement of water are ignored. Water entering
a given soil layer increases its moisture content to a maximum (0 )
fm
and the excess water passes on to the next lower layer. Further loss
of water from the layer is limited to the extraction by ET during the
interval following the irrigation. The salt movement is described in
terms of the leaching factor, defined as the mass of salt leaving the
layer divided by the sum of the mass existing prior to irrigation plus
the mass entering.
The prediction version of the simplified model is based upon the concept
of temporarily storing salt in the soil profile and leaching only when
necessary to prevent the concentration of salt in the soil solution from
exceeding a pre-set concentration constraint. This version determines
the depth of water to be applied for each irrigation for a given irrigation
water quality and irrigation frequency. The necessary input data
include:
1. The number and thickness of the soil layers.
2. The concentration of salt in the irrigation water.
3. The length of the season and the interval between irrigations.
4. The time between initial soil sampling and the first
irrigation.
5. The moisture content and concentration of salt in each layer
at initial sampling.
6. For each layer: the fraction of total ET, the upper and lower
limits of field moisture, and the maximum allowable con-
centration of salt in the soil solution.
177
-------
7. The daily ET for the irrigation season.
8. The leaching factor function for the particular soil.
The evaluation version of the simplified model predicts the water and
salt status of the soil profile irrigated according to a given schedule
which specifies the depth, timing, and water quality of each irrigation.
This version did not predict the field measurements with any accuracy.
Ignoring upward flow seriously limits the usefulness of the model in
many cases. The uncertainty with which the leaching factor function
can be determined for a given soil further limits the model's utility.
From a study using the simplified model for irrigation management, it
was found that use of seasonal average quality of irrigation water may
not be satisfactory. Whenever the quality fluctuates significantly, it
is probably necessary to know the actual quality for each irrigation to
reasonably predict salt movement. Studies also showed that season
totals of leaching water and salt leaving the soil profile are nearly
constant for a rather wide range of irrigation frequencies. However,
timing of salt releases was affected by irrigation frequency, with the
less frequent irrigations tending to release salt earlier in the season.
This would be expected because larger amounts of water tend to move the
salts lower.
Detailed Model
Water Model
A mathematical model was developed to predict soil water profiles,
evaporation, transpiration, drainage, and root potential at the surface
in a cropped field as functions of time. The model is for one dimen-
sional unsteady state flow conditions, and can be applied to irrigated
and non-irrigated crops.
The model consists of a second-order nonlinear partial differential
equation of a parabolic type with a plant extraction term:
IT =
where A(z) is the root extraction term which depends on root density
function, hydraulic conductivity of the soil, plant water potential and
178
-------
soil water potential difference. The solution for the above equation
was obtained by a numerical method using a digital computer. The
basic input data needed for the solution of the model are:
1. Soil properties: water potential and hydraulic conductivity vs
water content curves covering the range of water content to
be encountered in the problem; initial water content and
salt profiles.
2. Plant properties: root distribution (effective moisture ex-
traction) and the minimum and maximum values allowed
for the root water potential.
3. Boundary and climatic properties: precipitation, potential
evapotranspiration, potential transpiration, and evaporation
as functions of time; presence or absence of water table or
layer restricting water flow at the lower boundary.
Soil, plant, and climatic parameters were determined in the field. The
total study included two years of field experiments. The crops were
oats seeded to alfalfa in 1970 and alfalfa in 1971. Two lysimeters were
used to measure actual ET. Neutron and gamma probes were used
to measure soil water content profiles. Climatic data were collected
from a weather station installed in the field.
The cumulative computed ET was 4. 9 cm which was 0. 4 cm less than
the actual (measured) ET during the nine-day interval in 1970. The
use of published crop coefficients together with Penman's equation
gave estimates of evapotranspiration that were considerably in error
in 1971. Right after cutting the alfalfa, estimated evapotranspiration
was too high while later on it was too low. The overall seasonal
average of estimated and measured ET was quite close. Since daily
estimates were needed to check other parts of the model, the actual
measured values of ET were used as the boundary conditions for this
purpose. The computed soil water content vs depth profiles agreed
very well with measured soil water content vs depth profiles for both
crops in 1970 and 1971.
Computed cumulative upward water flow from the water table was
2. 2 cm which was 0. 10 cm greater than measured in the nine-day
period in 1970. However, for 116 days in 1971 the computed cumula-
tive upward flow from the water table was 4. 8 cm as compared to
1.6 cm measured upward flow for the whole season.
179
-------
Salt Model
A model was developed to describe the simultaneous flow of water and
salts in soils under varying initial and boundary conditions. Water and
thus the salt movement due to plant root extraction was also considered.
To predict the distribution of adsorbed ionic species, corrections were
made in their concentrations due to sink or source terms. Specific
chemical processes contributing to the sink or source term in the
model are:
1. Dissolution or precipitation of gypsum and lime.
2. Formation of undissociated Ca and Mg sulfate.
3. Exchange between cations in solution and the soil matrix.
The principles of solubility product and equilibrium exchange were used.
The solutes considered were Ca , Mg , Na , and Cl . The model
was tested under field and laboratory conditions. Three cases with
different initial and boundary conditions were studied in the laboratory.
In the field, the experiment was conducted with alfalfa as the major
crop.
Two wetting and drying cycles were monitored in the field. Measure-
ments of water content and salt concentrations were made three times
in the experiment. Experimental measurements were then compared
with the predicted values. There was a close correspondence between
the measured and predicted water content in all experiments. However,
predicted total salt concentrations agreed fairly well with the measured
values only in the field and one of the column experiments. Chloride
ions followed the same distribution pattern as that of total salts in
the above experiments. Predicted calcium concentration was higher
than the measured values while the opposite was true for predicted
magnesium and sodium concentration. It is postulated that these
differences result because of: (1) insufficient description of the ex-
change and activity coefficients at high salt concentrations, and (2) other
complex ion formation not included in the model at the present time.
In two laboratory experiments there was poor agreement between the
predicted and measured total salt concentration. The lack of agree-
ment seemed to result from the assumptions involved in the present
model or some reasons unknown at the present time. Since the salts
were applied to the soil surface in the powder form, they were assumed
to be soluble at the initial water content. It was concluded that this
180
-------
assumption is one of the reasons for the apparent differences in the
predicted and measured values. The investigation regarding the
applicability of the model suggests that more tests are needed. It
does appear to yield approximately correct values for total salt but
individual species are not as accurately described.
181
-------
SECTION DC
ACKNOWLEDGMENTS
Many individuals assisted, encouraged, and supported various phases
of work leading to this report. The authors would particularly like to
acknowledge the help of Dr. H. B. Peterson, USU,who directed the
research grant in its first year.
An advisory committee offered valuable help from time-to-time. This
committee consisted of USU faculty members N. B. Jones, Dr. R. L.
Smith, Dr. H. B. Peterson, Dr. E. J. Middlebrooks, and EPA personnel
M. B. Rainey, Richard Sotiros, Jim Vincent, Russel Freeman, and
Dr. J. P. Law, Jr.
The research work was begun on July 1, 1968, under grant #WP-
01492-01 (N) 1. The work continued from October 1, 1969, until
March 31, 1972, under grant #13030 FDJ. Mr. Richard Sotiros, EPA,
Denver, served as Project Office from the beginning of the research
until June 30, 1971. From July 1, 1971, Dr. James P. Law, Jr.,
EPA, Ada, was Project Officer.
This report covers two of four subprojects of the research grant.
The other two subprojects are covered in separate reports: "Cation
Transport in Soils and Factors Affecting Soil Carbonate Solubility"
by J. J. Jurinak, Sung-Ho Lai, and J. J. Hassett; and "Herbicide
Contamination of Surface Runoff Waters" by J. O. Evans and
D. R. Duseja. The authors express special appreciation to M. J.
Mickelson and R. B. Backus who served as farm managers in Vernal
at different times and supervised the farming operations and field
data collection. Appreciation is also expressed to the several graduate
students whose theses and dissertations are listed in Section XI.
183
-------
SECTION X
REFERENCES
Alfaro, J. F. 1965. A laboratory study of the effect of water appli-
cation rate on leaching efficiency. Unpublished M. S. Thesis. Utah
State University Library, Logan, Utah. 59 p.
Andrade, R. B. 1971. The influence of bulk density on the hydraulic
conductivity and water content-matric suction relations of two soils.
Unpublished M. S. Thesis. Utah State University Library, Logan,
Utah. 49 p.
Biggar, J. W. , and D. R. Nielsen. 1963. Miscible displacement, V.
Exchange processes. Soil Sci. Soc. Amer. Proc. 27:623-627.
Biggar, J. W. , and D. R. Nielsen. 1967. Miscible displacement and
leaching phenomenon, p. 254-274. ^n Irrigation of Agricultural Lands,
Amer. Soc. Agron. , Madison, Wisconsin. 1180 p.
Bower, C. A. , W. R. Gardner, and J. O. Goertzen. 1957. Dynamics
of cation exchange in soil columns. Soil Sci. Soc. Amer. Proc. 21:
20-24.
Bresler, E. 1967. A model for tracing salt distribution in the soil
profile. Soil Sci. 104:227-233.
Bresler, E. , and R. J. Hanks. 1969. Numerical method of estimating
simultaneous flow of water and salts in unsaturated soils. Soil Sci.
Soc. Amer. Proc. 33:827-832.
Cowan, I. R. 1965. Transport of water in soil-plant-atmosphere
system. Journal of Applied Ecology 2:221-229.
Danielson, R. E. 1967. Root systems in relation to irrigation.
p. 390-413. Jn Irrigation of Agricultural Lands. Amer. Soc. Agron.,
Madison, Wisconsin. 1180 p.
Davidson, J. M. , J. W. Biggar, and D. R. Nielsen. 1963. Gamma-
radiation attenuation for measuring bulk density and transient water
flow in porous media. Journal of Geophysical Research 68:4777-4783.
185
-------
DeVault, D. 1943. The theory of chromatography. J. Amer. Chem.
Soc. 65:532-540.
Dumm, L,. D. 1968. Subsurface drainage by transient-flow theory.
J. Irrigation and Drainage Division, Proc. Amer. Soc. Civil Engr.
94:505-519.
Dutt, G. R. 1963. Development of a computer program for calculating
the ionic composition of percolating waters. Dept. Irrigation, Univ.
of Calif. Davis. Contribution No. 50. 35 p.
Dutt, G. R. 1964. Effect of small amounts of gypsum in soils on the
solutes in effluents. Soil Sci. Soc. Amer. Proc. 28:754-757.
Dutt, G. R., T. C. Tucker, M. J. Shaffer, and W. J. Moore. 1971.
Predicting nitrate content of agricultural drain water. Dept. of
Agriculture, Chemistry and Soils. Univ. of Arizona, Tucson. 101 p.
Dyer, K. L,. 1965. Interpretation of chloride and nitrate ion distribu-
tion pattern in adjacent irrigated and non-irrigated Panoche soils.
Soil Sci. Soc. Amer. Proc. 29:170-176.
Freeze, R. A. 1969. The mechanism of natural groundwater recharge
and discharge. L One dimensional vertical, unsteady, unsaturated
flow above a recharging or discharging groundwater flow system. Water
Resource Res. , 5:153-171.
Frissel, M. J. , and P. Poelstra. 1964. A theoretical approach to the
movement of strontium through soils. Soil Sci. 98:274-277.
Frissel, M. J. , and P. Poelstra. 1967. Chromatographic transport
through soils. I. Theoretical evaluations. Plant and Soils 26:285-302.
Gardner, W. R. 1960. Dynamic aspects of water availability to plants.
Soil Sci. 89:63-73.
Gardner, W. R. 1964. Relation of root distribution to water uptake
and availability. Agronomy Journal 56:35-41.
Gardner, W. R. , and R. H. Brooks. 1957. A descriptive theory of
leaching. Soil Sci. 83:295-304.
Gardner, W. R. , and C. F. Ehlig. 1962. The influence of soil water
on transpiration by plants. Journal of Geophysical Research 68:5719-
5724.
186
-------
Gardner, W. R. , and D. Kirkham. 1952. Determination of soil mois-
ture by neutron scattering. Soil Sci. 73:391-401.
Glueckauf, E. 1949. Theory of chromatography. PVI. J. Chem.
Soc. 3280-3285.
Gupta, S. C. 1972. Model for predicting simultaneous distribution of
salt and water in soil. Unpublished PhD Dissertation, Utah State
University Library, Logan, Utah. 112 p.
Hanks, R. J. , and S. B. Bowers. 1962. Numerical solution of moisture
flow equation for infiltration into layered soils. Soil Sci. Soc. Amer.
Proc. 26:530-534.
Hanks, R. J. , A. Klute, and E. Bresler. 1969. A numeric method
for estimating infiltration, redistribution, drainage, and evaporation
of water from soil. Water Resources Res. 5:1064-1069.
Hanks, R. J. , and R. W. Shawcroft. 1965. An economical lysimeter
for evapotranspiration studies. Note in Agronomy Journal 57:634-
637.
Helfferich, F. 1962. Ion exchange. McGraw-Hill Book Company, Inc.
624 p.
Hiester, N. K. , and T. Vermeulen. 1952. Saturation performance of
ion-exchange and absorption columns. Chem. Engr. Prog. 48:505-516.
Hillel, D. 1971. Soil and Water: Physical Principles and Processes.
pp. 201-220. Academic Press, Inc., New York.
Jamil, Abdul. 1971. Comparison of field methods for measuring
hydraulic conductivity. Unpublished M.S. Thesis. Utah State Univer-
sity Library, Logan, Utah. 104 p.
Jenab, S. A. 1967. Development of a drainage function for the transient
case and a two dimensional groundwater mound study to evaluate aquifer
parameters. Unpublished PhD Dissertation. Utah State University
Library, Logan, Utah
Jensen, M. E. 1966. Empirical methods of estimating or predicting
evapotranspiration using radiation. Proc. ET and Its Role in Water
Resources Management, Amer. Soc. Agric. Engr., Chicago 49-53.
187
-------
Kunz, K. S. 1957. Numerical Analysis, pp. 4-6. McGraw-Hill,
New York. 381 p.
Lai, S. 1970. Cation exchange and transport in soil columns under-
going miscible displacement. Unpublished PhD Dissertation. Utah
State University Library, Logan, Utah. 128 p.
Lapidus, L. , and N. R. Amundson. 1952. Mathematics of adsorption
in beds. VL The effect of longitudinal diffusion in ion exchange and
chromatographic columns. J. Phy. Chem. 56:984-988.
Martin, A. J. P. , and R. L. M. Synge. 1941. A theory of chromato-
graphy. Biochem. J. 35:1358-1364.
McGuinnes, J. L. , R. F. Driebelbus, and L. L. Harold. 1961. Soil
moisture measurement with the neutron method supplement weighing
lysimeters. Soil Sci. Soc. Amer. Proc. 25:239-245.
Molz, F. J. 1971. Interaction of water uptake and root distribution.
Agronomy Journal 63:608-610.
Molz, F. J. , and L Remson. 1970. Extraction-term models of soil
moisture use by transpiring plants. Water Resources Res. 6:1346-
1356.
Molz, F. J. , and L Remson. 1971. Application of an extraction-term
model to the study of the moisture flow to plant roots. Agronomy
Journal 63:72-77.
Molz, F. J. , I. Remson, A. A. Fungaroli, and R. L. Drake. 1968.
Soil moisture availability for transpiration. Water Resources Res.
4:1161-1169.
Mortier, P., and M. Deboodt. 1956. Determination of soil moisture
by neutron scattering. Netherlands Journal of Agriculture Science
4:111-118.
Nielsen, D. R. , and J. W. Biggar. 1962. Miscible displacement: III
Theoretical considerations. Soil Sci. Soc. Amer. Proc. 26:216-221.
Nimah, M. N. 1968. The influence of irrigation intervals on water use
efficiency measured by the neutron scattering method. Unpublished
M.S. Thesis, American University of Beirut, Beirut, Lebanon.
188
-------
Nimah, M. N. 1972. Model for estimating soil water flow, water con-
tent, evapotranspiration, and root extraction. Unpublished PhD Disser-
tation. Utah State University Library, Logan, Utah. 131 p.
Ogata, G. L. , L. A. Richards, and W. R. Gardner. I960. Transpir-
ation of alfalfa determined from soil water content changes. Soil Sci.
89:179-182.
Olsen, S. R. , and F. S. Watanabe. 1959. Solubility of calcium car-
bonate in calcareous soils. Soil Sci. 88:123-129.
Penman, H. L. 1963. Vegetation and hydrology. Technical Communi-
cation No. 53, Commonwealth Bureau of Soils, Harpenden, England.
125 pp.
Philip, J. R. 1957. The physical principles of soil water movement
during the irrigation cycle. Proceedings International Congress of
Irrigation Drainage, 3rd 8:125-154.
Philip, J. R. 1966. Plant water relations: Some physical aspects.
Annual Review of Plant Physiology 17:245-268.
Poulovassilis, A. 1969. The effect of hysteresis of pore water on the
hydraulic conductivity. J. Soil Sci. 20:52-56.
Rasheed. H. R. 1970. Irrigation management to control the quality of
return flow. Unpublished PhD Dissertation. Utah State University
Library, Logan, Utah.
Rible, J. M. , and L. E. Davis. 1955. Ion exchange in soil columns.
Soil Sci. 79:41-47.
Richards, L. A. 1931. Capillary conduction of liquids in porous
medium. Physics 1, 318-333.
Richards, L. A. 1954. Diagnosis and improvement of saline and alk-
ali soils. USDA Agriculture Handbook, No. 60. 160 p.
Robinson, R. A. , and R. H. Stokes. 1955. Electrolyte solutions.
Academic Press Inc. New York. 512 p.
Rubin, J. 1966. Theory of rainfall uptake by soils initially drier than
their field capacity and its applications. Water Resources Res. 2:
739-749.
189
-------
Slatyer, R. O. I960. Absorption of water by plants. Botanical Review
26:331-392.
Tanji, K. K. , and L. D. Doneen. 1966. Predictions on the solubility
of gypsum in aqueous solutions. Water Resources Res. 2:543-548.
Thomas, H. C. 1944. Heterogeneous ion exchange in a flowing system.
J. Amer. Chem. Soc. 66:1664-1666.
Thornthwaite, C. W. , J. R. Mather, and J. K. Nakamura. 1960.
Movement of radioactive strontium in soils. Sci. 131:1015-1019.
Topp, C. G. , and E. E. Miller. 1966. Hysteresis moisture character-
istics and hydraulic conductivities for glass bead media. Soil Sci.
Soc. Amer. Proc. 30:156-162.
United States Environmental Protection Agency. 1971. The mineral
quality problem in the Colorado River Basin.
van Bavel, C. H. M. , G. B. Stirk, and K. J. Brust. 1968. Hydraulic
properties of a clay loam soil and the field measurement of water
uptake by roots. I. Interpretation of water content and pressure
profiles. Soil Sci. Soc. Amer. Proc. 32:310-317.
van der Molen, W. H. 1956. Desalinization of saline soils as a column
process. Soil Sci. 8:19-27.
Whistler, F. D. , A. Klute, and R. J. Millington. 1968. Analysis of
steady state evapotranspiration from soil columns. Soil Sci. Soc.
Amer. Proc. 32:167-174.
Titavunno, P. 1971. Quality of leachate from Vernal project soil as
affected by certain conditions in the soil and applied water. Unpublished
M.S. Thesis. Utah State University Library, Logan, Utah. 132 p.
190
-------
SECTION XI
PUBLICATIONS RESULTING FROM PROJECT
Theses and Dissertations
Backus, R. B, 1973. Field evaluation of a computer model for manage-
ment of irrigation return flow quality. M.S. Thesis. Utah State
University.
Campbell, M. D. 1969. Salinity and water potential sensor for evalu-
ation of soil water quality. M. S. Thesis. Utah State University
(Partial support from this project).
Gupta, S. C. 1972. Model for predicting simultaneous distribution of
salt and water in soils. PhD Dissertation. Utah State University.
Jamil, Abdul. 1971. Comparison of field methods for measuring
hydraulic conductivity. M. S. Thesis. Utah State University (Partial
support from this project).
Khalil-Ur-Rehman, M. 1971. Field evaluation of various transient
drainage equations. M.S. Thesis. Utah State University. (Partial
support from this project).
Nimah, M. N. 1972. Model for estimating soil water flow, water
content, evapotranspiration and root extraction. PhD Dissertation.
Utah State University.
Olson, B. R. , Jr. 1971. Evaluation of fluorescent dyes as possible
tracers for irrigation return flow measurement. M. S. Thesis. Utah
State University (Partial support from this project).
Rasheed, H. R. 1970. Irrigation management to control the quality of
return flow. PhD Dissertation. Utah State University.
Titavunno, P. 1971. Quality of leachate from Vernal project soil as
affected by certain conditions in the soil and applied water. M. S.
Thesis. Utah State University.
191
-------
Papers and Publications
Bresler, E. , and R. J. Hanks. 1969. Numerical method for estimating
simultaneous flow of water and salt in unsaturated soils. Soil Sci.
Soc. Amer. Proc. 33:827-833 (Partial support from this project).
Gupta, S. C. , and R. J. Hanks. 1972. Influence of water content on
electrical conductivity of the soil. Soil Sci. Soc. Amer. Proc. 36:
855-857.
Keller, J. , and H. R. Rasheed. 1969. Controlled leaching with unsat-
urated flow. ASCE, Irrigation and Drainage Division Specialty Confer-
ence, "Water in 2020. " Austin, Texas, November 5-7.
King, L. G. , and R. B. Backus. 1972. Drainage water quality as
affected by irrigation scheduling. ASCE, Irrigation and Drainage
Division Specialty Conference, "The Age of Changing Priorities for
Land & Water. " Spokane, Washington, September 27 28.
King, L. G. , R. J. Hanks, M. N. Nimah, S. C. Gupta, and R. B. Backus.
1972. Modeling subsurface return flows in Ashley Valley. Proc.
National Conference on Managing Irrigated Agriculture to Improve
Water Quality. May 16- 18, Grand Junction, Colorado, pp. 241-256.
King, L. G. , H. R. Rasheed, and J. Keller. 1971. Irrigation scheduling
and drainage water quality. Presented at ASCE National Water Resources
Engineering Meeting. Phoenix, Arizona, January 11-15.
Nimah, M. N. , and R. J. Hanks. 1972. Model for estimating soil
water, plant and atmospheric interrelations I. Description and sen-
sitivity. Submitted to Soil Sci. Soc. Amer. Proc.
Nimah, M. N. , and R. J. Hanks. 1972. Model for estimating soil
water, plant and atmospheric interrelations. IL Field test. Submitted
to Soil Sci. Soc. Amer. Proc.
Rasheed, H. R. , L,. G. King, and J. Keller. 1970. Irrigation scheduling
based on water and salt budgets. ASAE, Annual Meeting Rocky Mountain
Region, Fort Collins, Colorado, April 10-11.
Rasheed, H. R. , L. G. King, and J. Keller. 1970. Sprinkler irrigation
scheduling based on water and salt budgets. Winter Meeting ASAE,
Chicago, December 8 - 11, Paper No. 70-736.
192
-------
SECTION XII
APPENDICES
Page
A. Simplified Model
FORTRAN Listing of Prediction Version 194
Example 1 - Long Output Prediction Version 202
Example 2 - Short Output Prediction Version 204
FORTRAN Listing of Evaluation Version 206
Example 3 - Sample Output Evaluation Version 210
B. Detailed Model
FORTRAN Listing of Water Model 215
FORTRAN Listing Combined Water and Salt Models 223
C. Data and Results
Tables 34 through 60 239
Figures 56 through 81 283
193
-------
APPENDIX A
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CFII|-OFC(TI»CFriIt/OF(I)
TFIiFIII.LT.QTdll GO To \ t
niFTfFi i i-r r i [ i
tfrl
IF mir .r.r.r ' toi i r>p to IR
1 7 r^NT INUF
r>f to i qs
1 0 '0 1 R1*
F°TOt 1 1 I /OFT
0 F « r 9 H I I 1
CL 1 t > -°F I3T it .f Pi « 1 ni U I'T 1 ' I»I F »' i III I/ r(|. l I 1
CFCI 1 1 - ( fiFv .r c II 1 •r-r (I l«r: ( • I-! t H I'l L 1 ' l I/ "F r
r.n T o l •»«;
ten 11. H i ;o.
195
-------
IS*
iss
1'S7
isa
rri
177
17.?
17«
i'7s
17(1
177
I7«
17<»
iBii
mi
l'B7
181
ran
1'87
ISA
i=DL I I I
OFI!Cl=OFC(Ifl-IOKHCI»ETTIJ+1ll/li.»«l7.l
CFI TCCOFCI if i «rrr ITC i /or < ic i
ni^ = CF I I CI -""< I K I
TF(iIF) I1<5S. 7?il"
r>nr»»inTF»»i»i-») i/ i~tf »-ojrn
DFii>=nn
fir IR T IT it if
OFTCFC i i) • i?. •• »
DF» -nn< n«» ,-.«r «
01 (T i rnr « M- «orr -TUT i
IF CIL 1 1> .tr .,i. ' 'r,n • c i 3l=
000
nan
ono
nOO
000
new
187
nnn
196
1'97
190
i'99
znn
rnt
?n«
709
7\<\
711
717
7*11
716
7t7
7|B
7ri9
7?fl
771
777
7?\
77»
77S
7?ft
921
?79
rjrj
?ji
7J7
noo
oon
oon
nnn
nan
000
nan
noo
ooo
Onn
nOO
non
oon
000
oon
non
nnn
nnn
nnn
non
onn
fifin
Dim
unn
nrm
OOU
oon
000
nnn
nnn
ntm
nnn
nm
nor>
nfll
onn
0(10
nnn
nor
ntm
000
OnO
ooo
ono
000
ndo
nrm
197
196
197
OF*:OBIII
CL (I I ;PF|OFr.EP) «(nr (I i«CC (I l*PFxt ro (i i i /ILI I I
CFCI t» = tOE»»r««i i »T u »»CE IT I-PLU i »CI.«T» i/vc
RO TO 1 H<1
DLiTi=n.
cL(Ti=u.
fFCI II = (DE«*CBII I»OF II >*CE(I I) /PFC
CEII»li:CLI I )
OFIT»1I=OL I II
OF(TCI=QFCCICI -I«>K net •F.TTij«tn
rF(TC»=OFciio »fFr (ici /OF t tr i
OIF = CFIICI -CTI 1C I
IFHOSIOIF >.LT .CTTOL » G3 TO 7?
T.FIOIFI 191.22.1^?
OIFB1=DIF
Rirno
00r«l* IOTFP 1«(°-R 1 II /( DIFRl-niFBI
OIFBIOIF
B=BI
TFino.LF.*! GO TO t
TFint I II .LF.II. I GO TC 117
FPT"L (II /OFC
ct U)-°FIOF»,FRI *ior il i»ct it )»rr«,
CFP( t) =inF.X«CBIII*Or II )«CE IT I-PLII
RP TO 198
OLII i :n.
ci 111:0.
CFCI D:IOF.X«C^ a )*"F u i«cr u H /DFC
I/OK i )
OF(I*H=DLIII
OFIICI=OFCI ICI-IRKIICI »fTT l.)«l )t
CFI IC>:OFCIIC)«CFC (TCI /f Fl If I
nlF«:CF( ICI-CT (tfl
TFcniFi.LT .CTTOL i r,n TO ?z
r," TO 195 -
OIF4irDIF
OOr*+IOIF4»l»J-») ) /IOIFA-OIF Al
E.a) GO TO i q^
B=PT
DF I 1 1 =DO -
on u 9f 1=1 .ic
OFrrBFCI I) • 1?. •"»
DFX=Oi»! T Ml 7.«r>X-
HL 1T IrOF ( I I- (PF'-T-x i
TFintt II .tr.u. > GO Tr. in?
CL IT »:PFIOE»tE»l '(OF (I I«CFH »*DFX« tPIII )/nLll >
CFCI U = IOex»CRIII*nr II »»C£ I' t-f'LIF MCt-II) I/RFC
60 TO 1 198
1197 DI. aim.
CtlTl=0.
rrn iirioEi»CBiii*onu«CEcr n /ore
756
1196 OEIT»1>=OHI1
eF«TCI=OFC(IC)-IRKIIC) •FTTIJ+HI /IOX« 17.1
196
-------
717 ono CFI TCCOFCI ici*rFrtin/OFI ir i
718 Ofln HTFPrCFC IC1-CT(ICI
7iq nan IFIi8s nnn UT»*l(I.j)rOFI II «OX« ,87«CF(I )
717 noo sqn rso»i,j,rj*p»j(J>»UTP»IIi.ji
7«8 nnn no s«»i I:I.N
7»t nnn OFI« i.ji =OFI 11
?sn odn ssi CFK I.J)=CFIII
751 noO DFPTH
7S7 nnn PL I.M TTHLI j) «ion./nn
7S8 non BUH:BUH«-WLPt(J)
7"5S noO 731 Jrj«l
7Bn non KFTKF»KM
Xt>i nnn KKTKK+KM
767 non TOrTD»no
761 non BLT:CHLT»100./Tn
71* nOO IFIJ.Lf.JMix) GO 1C SS5
765 nan c»n "PiNT(Run.r.rR»,CBi.cri .rHL.ct'Li ITT. cfTOL.nrPTH.nr.t T.r ii.jfs
766 nnn l*.tF.Q)
002 000 DIMENSION MS.3) iB<9)
OC3 OCO 0»T»( (AC It J» tJ=li3) 11= 11 SI/- .6 5575 i T .CH3«l.t -70. 536 • .158r8 t-7. 118T t
0 i» OCO X22.5«mt-.0«'»719,l.«(081f-11.71il f-.P197T7t-. 3r 1"» 3.2 . 5H 71 f .03?7Slt
005 000 X-2."»902.15.651/
006 000 DO 10 I=l>5
007 000 10 B«T)=A(Itl)+AI I.2J«OEX + *II.T)»8EX»»?
008 000 IFCER.LT.0.2) GP TO 1
009 000 IF(ER.8E.0.2.AND.ER.LE.3.> GO TO 7
010 000 3 PFLOO=B(l)»BCZ>»ALOOt3.»*BI3)»<»l_<»C3.l l» »2»BC«1)« ( »LOG< 3. I) •»I + '> ( 5
Oil 000 XI/3.
012 OCO PF3=EXP(PFL031
013 000 BI9)=B(2)*2.»B(3I»AL06(3.>»J.»BI*)«t*LOG(J.IJ»»2-B(5)/3.
Om 000 B(8)=PF3/3.»*BC4>
015 000 PF=B(8I»ER**BI9I
016 000 IFIPF.GT.l.J PF=1.
017 000 GO TO 1
CIS 000 1 PFLOG=B+e<2)»ALOG<.2>»BO)»
-------
n"i
nn?
nfo»
nos
nnr
nn*
nnq
mo
(Til
ni?
TIS
T16
«T1*
n?3
071
n?S
n?fi
n?7
n?«
nx?
nao
n«i
tti»»
rr«s
n«R
n«a
n^"»
nsu
nnn
nor
nou
noo
ono
onn
ono
nnn
noil
ooo
ciiin
nrm
000
onn
non
000
noo
000
onn
DOM
non
ono
non
0(10
DOO
nnn
nno
OOn
nno
oon
000
ono
nan
non
nnn
noo
non
non
noo
000
onn
000
onn
nno
ono
onu
non
ono
onn
nnn
nnn
not!
cnn
000
flfill
flfil
tt6«
fl6«i
O67
rrea
07O
070
(T7S
n?7
fT78
(ISO
P81
ITS?
083
(TA«
DOO
000
000
nno
nan
000
000
000
000
oou
000
OOO
ooo
000
000
000
000
000
ono
OOn
000
000
000
nan
DUO
R».ORI.OFI . r.Fr.oT.RK.Pt. t§>LT .in. rrr, TTH. r-.r M • -L
?PA.uTPA.wTPM .N.IPPTNT )
niMFNsioN r a« i?n> .Cfi<7u. ?rvn, CHLI?;HI i.ri 17111 .P^THI/, i. I,F TI i«,i i ,t
ITT< ism . nnM?ni .on <2u-;>na>.OF cizni .or t?o I.O> .PL < ?i >)> ,
?ni .uLPt < 2nni . UTP» t <7[,,2 IKJI .u Tp«<7n> .OBI ( ?.)> . mi t ?,i i
URITEIG .sum
son rop«ATt • IINPUTS*. nx. 'LAYE<> RK arr M
i . • ("MHO/CM) « i
wRTTFit.sm i ti ."M n ,OFC< i>. n d i.cn n . i n ,NI
sni FOPMATMH . ?;•)(. i? ,'»Fq.? ,Fin.?i
UPTTEIR .SO?K:.PX.L'KM.KMI .TTTOL
50? FOO«AT(' Or' .F',.? .«X. 'PXi'.Fn.?.!!*, -LT' . M. ux .'KH T' . I7.<4X . 'KHlr • ,1
n e Y
o.u GO TO ?dni
URTTF(fi.5n3>
503 FOPW»T<« INITIAI SOIL CONDTT IONS • .u -\x ,T& RY Fv«f>oT"t.-,^f
U.'L»YFB 08 fR '.SSX . •( TMCHF1) •/ lux. • (MMHO/CM) '.I?!
?t«»i
sn> ir n . r i-- 1 ,NI
GO TO so?
SOF, TFCT.EO.N) BO TO si 7
I=T»I
i n .004 (
5U7'
iFfjn»x.GE.«)r.n TO «;o^
no TO tsjn. si i. si ?i ,JM*X
sin wp'TFifi.sm
513 «-OP«4T(1 IHHFOIS TFLY PCIOB TO IRPI-. j
I/M> S^IL s»Lf HOIST <-ONr
7 T/»c CONT ifno/Ci T/«r '•ONT
TF««Hi.eo.n) G" TO r^,,,,
no SBR isi.s
WRTTF(&.<>I,o««] < i» .r BI IT i . (
.u «FHI.« .
J- IMTF.--VAL 1*
>,nr '/nx. • i_AYr-
si« FOPMAT d7.?r7.u.F <».«,
GO TO snni
sooo oo
K T. JI.OFI i i.
11
) .cr HT. ji .
UPTTE (
ir
iri.opji ti .r p»(i i , iw'p« K i. j i .;FI / >, ji ,rr 1 1 j. ji ,
i<;c4 j ( j| ,j r] .jM»xl
*.«t /x.i 1 1 »x.F7.m»
. ( J.r-rPTHI J) . j : 1 . jH»x )
N« ,x». I (ux . •'• (•!., I-' ir«,j7
I J) . j : 1 .
l:',ri..:>
UPTTt (d ,.s^l 1FT f( I I . ( J.r-r
*-M FOI»<»T| «OF.T PP.TI- ir r"R
ItlMr.FU.?,' IN«1 I
URTTE(K.5 J?MWIP»(JI . j:l. JH«»)
137 FnoM4T, 1lx. H S» . 'SALT Lr»VINP: '.F« .7. •
WRTTE(F »SST) «CH_ (J). J:l . JM»X I
5S3 FOPM»T< 31X. II «t'LF»CHlN6 W»TFR:-.FI>.7. • INMI
WRITE(Bt53«) «RL (J).Jri, J«»x)
530 FOPHAK J2x. 112* t «LF*CH REO:'.FS.?.- PERCFNTMI
WRTTECR.SSBI (J.FTT cj«u.j = j. JMAXI
S35 FO°MAT( 30X. U »X . «FT .INTERVAL «.I2. 1Hr.F».? .• IN'))
BO TO S85
511 wRITE(fi.SlS) (J.jrj. 71
M5 FORIATC' IM^FniATFLY PRIOR TO I RR I G 1 • . ?( 3X . • AF TFU IR7IG JKTFRVA
IL'.I?)/«O SOIL SALT MOIST CONC« .ix. 71 7».«s»LT HOIST CONC •
7)/«X. -LAYER T/AC TONT HMHO/ CM' . 1 X , ?( SX • «T / AC PONT MMHO/fM'll
TFtKMl.FO.nl GO TO COUI'i
no fise I = I»N
K86 WR TTE (fi . S 11 II. WTPA d I i 88 1 < I) .C Bl ( T I , J WTPA 1 t I . J ) .OFU T . JI . CF I (I. J I ,
1J=T.JH«X)
PO TO BOni
ROOC 00 P.6 flfi 1-1 «N
SKOf WPITE (F.51*) I.UTP8 (I I.OP.AI II .rBA(I) . IWTPAId. JI.OFI ( T. JI.CFUT. J) .
?I»X t • OF PTH IPPIG'.I?
MRITF.(6.5I01TSPA. (TSPAK JI tjri
MRTTE(K.6«)f TTtl ),(J,OEPTH( JI
R31 F09HATCOET PRIOR TO IRRI6 lr'.'F«.?t» IN'
1. 1HZ.FU.?.' IN»I)
URTTE(R>CS?) (uLPAiji.jrit JMAXI
fiJ7 FORMATC 31Xt 7( JX. "SALT LFAVIHI-'iFH.?. " T/ ACM I
WRTTE1K.6S3MCHL (JI t J = l .JMAX I
198
-------
nfts
HSR
ft* 7
rf88
RBI
tin
nil
ni?
ni3
fVHl
nis
niR
ni7
nia
mi
rnn
mi
rn?
IO3
in«
Irtfi
1O7
ins
i ni
I'm
vi i
11'
11*
1 1«
CIS
1 16
I'l 7
1 IS
I'll
i?n
1"71
177
l'?J
1 ?«
125
1 ?R
127
t?R
1 ?1
130
rsi
!'3?
1 ?3
l"3*
1 35
U6
1 37
t 3R
1 31
i«n
1*7
103
1««
1'ttS
1'ofi
1*7
1 H*
I'll
1 SO
1 SI
1'57
1'S3
1 SO
1'SS
156
1S7
1S8
l"51
rf.il
IRI
167
163
!'&<«
IRS
lf.fi
167
160
•inn
nnn
oon
non
00(1
nnn
non
000
pnn '
onn
nno
nnu
OiJO
nnn
onn
nnn
nnn
nnn
nnn
000
0011
nnn
nnn
nno
nnn
01)0
nnf.
Dili'
ono
000
nnn
nnn
000
noo
oon
onn
ono
000
nnn
non
000
ono
onn
nnu
non
000
noo
oon
noo
nnn
nnn
nnn
noo
oou
ono
non
oor
nnn
000
noo
nan
000
OOfi
nno
nno
oon
onn
nno
nob
POO
nno
000
noo
non
oan
ono
oou
nor1
oon
oon
non
n on
non
RS3 FOOMATI 31X. 7( IX. 'Lr«CHING w A TF R : ' . F u . 7. • INMI
URTTEIf..63UI(RllJI.Jrl.JMAXI
R3i Fp'HATI 3?x. ?(?*. 'LE4CH RED:' .FS.2 • • PERCENT'))
UP T T E ( R • R 3S I IJ.ETT ( J * 1 1 . .1 = 1 • JH A X 1
P3s FOo-tT i 3nx. 7(«x , 'FT, INTERVAL •• 12. IH:. FM .? .• IMMI
Gn TO sss
S17 URTTFCR ,5161 ( J. j: 1. 31
SIR FPRMATl* fMEOIATrLY PRIOR TC IKRTG J • . 3 1 3« • ' «r TFR IRfilb
1L',I2)/M) SOUL SALT MOTS' CONC' . 1 * , 3 ( 'X • • SALT "OIST
7>/Sltt)I>WTPAII>.nnilII»rbl(I).IUTPAl(IiJI.OFllTiJl.rF
\ J; 1 , JMJ x 1
GO TO 7001
70110 00 77R6 1:1 .N
77«F> «RTTF(fi.SllllI.WT'JA(!l,P!1AII),rBAIII.I*TpAll!.JI,0'"I(I,J).CF
1 J=l . J*AX )
7|)ni URTTE(P,.S3niTSPi. ITSPA] (JI .jrl.jf.tx)
WRTTrtR.731)£rT((l>
1 . 1HT. Fll. 7. • IN • 1 1
URTTFK.737l(WlrHIJ).j:l.JM«x)
737 FOP- AT 1 31X. 3( ?> . 'S »L T L E • W TN Kr • . «"ii . 7. . T/»r«ll
wPTTf if, , 7S3 1 (CM | j I . j:| . jniir i
7S3 flOU«T(3)X.3l3».'LF»rHlNri U«Tr»:',F'i,7." I'.'ll
wR'Tfcr, i'^<.MH ijt.jri«jr*AX!
73u FPOM t j I 371. K 7« ,»lcArH 0^1-'. ''.?.' P! Rf NT • 1 1
WR1TE(R.73SI IJ.fTT (J*l),j:1.JMAXI
73S FORM AT ( 3i)x . 31 UX . *F T i INTER VAL • > I ^. 1 >J:« Fli . ? . • IN'I)
r,o TO s»i
Sni vff TTCIR , si7) i j, jr t, i )
S17 FpR^itC" (MMfOTATFLT PRIOP T c, IRPTC. 1 • , a 1 3X . • AF T F * f f a ICj
lL'.I?)/*d SOU S»LT HOIST CONC* .IX. »C 7» ,'SJLT MOIST
7 I/Mr, 'LArrp J/jr fONI HMHO/ r H ' . 1 X . HI SI . ' T / »C TPNT «MH
IFIKM1.FO.OI GO TO KOlIU
00 1R R 1 1 1 . N
88R WPTTEIR.5ialI.uTPAII).CRllII,Ce)II)<37 FORMAT 1 31X. M( 3X . *s ALT LFAvTNG: ' . Fn .7. ' T/AT'll
WPITEIf.B S3) 1C w. 1 J I . j;l ,q 1
SS3 FORMAT I 31X. «l 3X. 'LE«CHING U A TTP. r • . F« . ?. - IN'II
HRTTEIR.R J»l IRK JI t J=I. « )
R3i> FORMAT! 37X. m 7X . 'LFACH REO-'.F9.7.' PFRCFNT'I)
HRITEIfi.fl3S)IJ«ETTIJ*ll.J-l««l
BSE FORMATI 30x. mux . -ET. INTERVAL •. 12. iH = .Fu,7 .• IN*)I
IX^f,
IF UMAX. GT .UIGO TO 7i,
KO TO * <*S
70 IFIJMAX. GE .IX IGO TO 90
JX°~ JHA X-IXP* 1
r,o TO i mi. 10 ,?. in 3. IUM > . JXP
10PI IFIIX.F0.1S.OR.rx.r,l.7«).OR.IX.F0.3<>.OR.IX.r3.«1.CR.IX.EO.Sc
1FO.K1I GO TC la 1
URTTEI6.111I IJ.JrlXO.JMAX)
111 FORMATI1H .1C4FTFR IRRIG IN Tf RV «L * . I 3. «X ) / 1MO. 1 1 ' SALT *
ICONf • ,7X )/lH .11' T/AC CONT MMHO/ CI* « , BX I 1
GO TO 3
inl WPTTC (K.71.1 IJ.JrIXP. JMAX )
71 FORMAT! 1H1. 11 'AFTFR IP.RIG IN Tr RV AL • . I 3. ux 1 / 1HO. 1 1 • SAL? "
1COVC " .7X I/I N .) 1 * T/AC CONT MMHO / CH> , «JX 1 1
3 00 77 1:1. N
77 WRTTE(F.?3)IWTt>A1 II.JI.OFKI.Jl.CFKI.JI.jrlxP.JMAX)
73 FOPHATI1H FR.l4.F7.il ,Ffl.u, UIF J 7.I1.F7.0 , ffi.ul 1
UP1TFIR.?miTSPAl(J).JTlXP.JHAX)
711 FOPMATI1H . FR.t .0 l?nx tF 7.<() )
WRTTF»R,?S)IJ.PFPTH(J).jrIXO.JMAX)
75 FOP-ATI 1HI1. I I'f/f RTH 1° P I K • . T '. I H z . r u . ?, » TW'.SXI)
tfPITE(F.7R)«KLB»IJ).j:IXP.J«*xi
?R FO°wATIlh »H'S»LT LFAVlMn^'.Fo.?.' T/A1"*.'-*))
VRITE(fi.?7MCMltJI.J:IXP,Jl.JM(1»1
yd FOPMATI1H ,H*lrAru P""f}: • ,F<;.7, • ,"f ?C F NT ' ,u » 1 I
IkiTFR V»
CONf •
'I/CH' 1 I
1 1 T. JI •
1(T, JI .
T n T r r> v A
roNC *
1 /CM' 1 1
1
-------
1 7n
i7i
177
V7J
170
«7S
V76
177
i'7s
1 79
isn
isi
IB?
IRT
I'BB
185
las
V87
1'88
i'8<»
i<»n
I
non
nao
nnn
nnn
OHO
noo
OHO
nnn
nnri
nnn
onu
onn
nnn
nnn
nnO
oon
nnn
HOO
nnn
onn
ono
onn
nnO
OOn
000
OnYl
nnn
1.7. • TN'.CXII
W 1 T t t r . ?s> i .1 -F 'T t ,i» i > • i- i »P ..I i
?<* FOR«ATI1H . I I *FT • INTERVAL*. I *• 1
GO TO «.an .ix.r 3.s°.o* .1 x.
IFO.eq) GO TO 107
u/lHu.?( • SALT M"JST
icONf ,7x >/IH .?t« T/AC CONT MMHO/CN*. sx i )
GO TO a
in? WOT'EIK.JD ( J.JTIXP.JHAX »
31 FCOMAU 1H|. 7( • AFTFP IR9IC, IN IF RV AL • . I 3. It ) / 1 H fl. ? ( • SALT "OIST
ICQNC • ,7x t/i H ,?<• T/»C ro»n HHHO/C*'. *.x 1 1
B no v 1=1. H
'*? WTTEIF .? n CWTPM 1 1. j> .OF i u.j i .rri u ,ji, j- T*P.JPAX>
WRTTE(K.? t J«nFPTH( J) . jr IIP.JMt*)
TV FO»«AT( 1HO- 7( »CrPTH IRRIf,',T 1.1Hr.r« .?, » IN'.SXJI
UPTTI «;.•<&) (WLTI iji.j = iiPtjHAx i
Jfi Ff)OM»T(lH .7l*SALT LF i V ING = • .F B . / . - 1/4r',SX>)
WRITE(fi , ^571 (CHL ( J) . J- IX°. JH»X)
WPTTFCK.^SI (PL IJI.J
JP FOOWAKIH .^CLEATH prc-«.rs.?.« FFWCENT- .MX 1 1
WRJTEJU. ^ql| J.FTI IJ«1 ) . J = IXP,JMAX)
39 FOP.MATC1H . 71 «ET. INTERVAL '.1^. IHr. Ft .2« • TN'.SXI)
GO TO SB5
mot IFITI.EO.I«I.OR .IX.FO .?9.oi? .ix.ro.^«».OR.ix .ra.ui.oR.tx.r'J .
iro.«-.9i GO TO IIM
; ,qnq»t j, jn»
.ix.
T/AT CONI
HMHO/CM'. sx i )
i cr-Nr • ,7x t/i H .•?
so TO s
ins WRITER. «J.J:IXD.JMAI >
«1 FOOMHJ IHlt ^I'AFTFr- JPRIG INTFPV AL • . M. HX > / I Hfl. ^ I •
icoNc« .7x)/iH .^(' T/«T CONT MMHO/CM-, ** 1 1
s no «? J^I.N
«? WRITr«f..??» CKlPA) ( I.JI -OF 1 (T .J » ,ff 1 t I ,JI, j; ixP. JMAX t
uRrreiRt?*) ITSPAI ( j) . J=IXP«JHAXI
MRTTEIE.OSM J.PFPTHC j) . JIIXP.JHAXI
is FORMAT ( i HO. ^t TTPTH IPPIG'.M.IHI.FII.?. • IN'.SXII
WRTTE (R ,i»6> I«L°A u> . J=IXP. JMAX i
IF FOO«»T(1H .TC'^ILI LF AVINGr'.f *.?. • T/»M.SX>»
UPTTF(f. .1 7) (CHI IJI . jrl XP. JHAXI
17 FO"»»T(1H . K'tfArHTNG WATFP T« .FH.7 .« Itj'.SXI)
UPTTF (fi .148) (RL IJ) . J: IXP. JMAX )
779
731
737
733
7X*
735
73fi
?37
738
739
740
?*l
?«?
?«3
7««
nnn
ODD
non
onn
nnn
fjnn
nnn
onn
OOn
nno
nnn
nnn
ontj
000
OflO
OHO
OOn
000
000
OflO
7*«7
7*8
?«<»
750
7S|
9S7
000
000
000
DOO
OOO
000
000
OOXJ
000
not)
000
OflO
DOO
BOO
WPITEIB.H9I t J.ETt ( J*l ), J-IXP.JMAX)
u° FORMATIIH . m «FT . I^TFPV AL • . n. i H;.F q.?. • IN«.«;X))
GO TO SRI
inn« iFirx.ro. i<>.oa .IX.FO .?«. OR .IX.EQ.V>.I-?.IX .r ).«•). o*.i)' .r i.^^.r^ .T
iro.M) GO TO mu
WITEC^ .on') i J.J=IXP, jn«x i
908 FO°H»T<1H . « I • A F T E D IP°ir. TN lf 5 V AL • • M. u» ) / 1 '•< •!, 14 I • '!(_' •••.:''
icoNC'.7x)/in .»i» T/HC CONT MMHO/CK*. sx i i
GO TO c.
l^o MP TTE (r. ,5 ( | ( J. j; l»n, JMAX >
SI F«°«aT I 1H1> «( • AFT^P I o r> J f. IK T| S V tL * • I "• UX > / 1 M .'-I* ' *> L T ''r 1 r. T
1 COWf • i7< I/I H ,«(• T/»r r"Nl .MIHII/CH". sir I I ,.
fi no <;? i = i.w
s? HPTTEIK.?^) (WTPAI i I.JI.OFHI .j i .tFi ci . j>. j: tx"i JMAX i
HRITECF .711 IT«;PAI ij>. JZI
uRTTEtf ,ss) < J.PFPTHI ji .
SS FORMAT I IHOt Ot «DT°TH IQ RIG • . I •<. 1 H~ . F« .?. • TM'.SXI)
HRTTE«t;.56MytP»«J).J=IXP.JNAXI
56 FORHATCIH ."K'SALT LF A VINHr • ,FH . 7 . • T/«c«.SX>»
HRTTEI6.57MCHHJI. JrlXP. JMAX1
57 FOPMATJ1H .M'LEACMING «ATr» =• .Fn.? . • IN«.ST»
URITE(fitS8MRL ( J ) . jrlXP . JM*X >
58 FOOMATflH .i»(«LEArH RFO: • .F <;.7. • "F^CFNT • .H X I )
MRTTEI6.59) ( J.ETT( J*l I. JTIXP.JMAXI
59 FORHATC1H . WI'ET. INTERVAL '.I^t IHr.FI. 7. • tN'.^XI)
GO TO SR5
907 IFIIX.E0.19.0R.IX.EO .29.0R .1 X. EO . VI. OR.TX .FC .B9.0R .TX.E 0 .59. OR .1 X.
1F0.69) 60 TO 90
UPITEfE .!» (J. JrlXP.IX)
1 FOPNATI1H .*I*»FTER IRRIG INTERVAL • il 3» «X I . "AFTER IRRIB INTF&VAl.' t
H3/tHO.«U- SALT HOIST CONC',7XI.* SALT MOIST CONC«/1H . 1 « •
7. T/AC CONT MBHO/CM' .5 X ». • T/AC CONT MMHO/CM'I
GO TO 7
90 MRITEJ6.61M J.JrIXP.IX )
61 FORMAT! 1H1. *(«»FTER IRRIG INTERVAL • t I 3. « I . -AFTER IRHIT TNTFKVAL'.
II3/1M0.4C SALT MOIST CONC-.7XI.' SALT HOISI CONC • /IH . <• ( •
7 T/AC CONT MHHO/ CH« .5 X • . • T/AC CONT MMHO/C^'I
7 00 62 Irl.N
200
-------
7SS
75«
75S
756
7S7
758
/SI
76n
761
767
763
76«
76S
766
767
7fi«
76i
770
771
777
7"7J
774
775
776
777
77«
77<)
7Bci
7si
?«^
•701
•7««
785
786
7A7
?fl«
9&1
790
7si
291
7SS
796
797
798
799
TOO
SOI
T07
501
ro«
JOS
TDK
Ttl7
T1O
til
TlS
•X16
T19
T20
T71
T77
T?3
t?»
175
17B
000
000
000
000
000 '
000"
OflO
000
000
000'
Dno
000
DrfO
BOO
000
000
non
000 '
000 '
000
OflO
ntm
000
000
flOO
OnO
oon '
nno
nnn '
nuo
000
OOtl
omi
OOO
OOP
000
nnn
ono
our
HOD "
DOT!
0.00
000
0(10
OOO
000 '
000'
000
000
000'
000'
nno
OOU
000
000
DOO '
DOO
000'
000
nrio
DUO'
Ono
000'
000
DHO '
000'
000
nail
000
000
OOP
DOn
OUO
000
000
DOT!
i JXD
• in1
6? VRTTEI6.73I (KTPA1 < I.JI .OFlfl.J (.'Fll I .Jl. JTIXP.IX )
URI TEIR .?«> ( TS°A1 (J). J-TXP.Ilfl
HRTTE (f .65M J.DFPTHIJI . J-IXP.T XI
65 FORMS! I 1HU. 1 ( 'PFPTH IP RI G ' i f < • 1 H - . F K . ?. • IN • i iX ) i • OF \- 1 H
MHr.FU.7.1 IN'I
WRITE . • SAL T LF A VINT,: ' . F« .7
t i • T/AC' )
WRTTEI6 .671 CH Rt 0; • . F S ./. • PE rfc FNT • ,o i > . • Lf if M -T Or • .- «,.?.-
1PFPTCNTM
UOTTEIfi.fit)) ( J.FTT < J»l I . J^IXP.l »|
61 FOP^tTllH . HI "ET . IHTER V»L ' . ( 1. IHr.FH.?. • IN • . S» I. •( T , INTI ^ivit • . I ' i
IF(JM»x.GE .IXP ) GO TO HO
GO TO SKS
til TF UMAX. LT .IX I bO TO 8
RO TO 9tl7
n JXP:JM4X-I»P« I
GO TO I IHO) >10('7i inns . int.
SB5 WPTTE«6."?nn)
inn FOP"AT(f «/i
GO TO 711110
71101 VPTTEC; .?no?»
7on? FOOIJTC' INITIAL snii
1 •//• l»r f P 0:> r '
7P/CM ) •. qx , • (T/ACI CONT
TF(KMl.FO.n) GO TO TOtll
DO 7UQT 1-1 >N
70U3 WRITE(F..?00«II.OfiA (I I ,CPA I I) .uTP«< I)
700» FOOMATI I7tF 7.7.FR.2 .8X. SFfl.ii)
GP TO too<»
nn ino3 I;I.N
W»TTF if .?UKI a) i.np» IT i . CR« 1 1) .w TP AI n . as* 1 1 >
URITE(fi.200 S) TS.PA.FTT(1 )
70US FOPMAK 7CX. • TOTAL • . F 7.» .fix. 'PPIOR FT:«.F5.?//I
HRTTFIF- .7HD6)
7006 FPPMATI 19X . "DA1L Y F V AP OT R ANSPT R A T I ON1 1? TX . • t I NCHE S I • )
WRTTE(6>?DO 7)
7007 FOR«AT(« t.7l1OAY FT «H
Nxrll-l)/7«l
DO ZOOS Mrl.NX
7DOP UPTTE(6.70U1MKK,ET(KK l.KKrM.L.NXt
?Dfl9 FpPHATC- • I 7. FH.2 ,f.( I S. FH .7 I I
WRITE(K.2(l?n»
702P FOPMATf'l AFTfP SALT SALT WATCR LEACHING LEACH'Nr.
IFT FORV IRPIG EXISTING LFAVINK APPLIFP WATFP °rn.
7TNTFRVAL'/' INTFRVAL (T/ACI (T/AC) ( IM ITMI
3) (IN)'I
WRITE (6 i?071X J.TSPAK J) . WLPAC J) . DEP TH (J 1 . CHL( J). 9t(JI.FTT(J»l».J-
11 1 J*AX>
70?1 FO»MAT(I6>F10.7.F9.2,Fin.7tF8.2.F11.2 .F9.?l
URITE<6.70?2UT';PAM JMAX » , flUH. TO. CHLT , RL T .TFT I
7027 FPRHATI1 SF ASON • . FR .7.F9.7 . Flo .2 .F )>. 7-F 1 1 .7. F1.7 »
GP TO quno
700P URITE(6t9ni)
901 VOO«ATI« SEASON TOTALS'!
WRTTEJ6.907ITO
907 FOPMATCCi PFPTH OF IRRIGATION WATFR ;«.Fr.2.'
I ^' ".* .1*1 OP T;
: rot.; • /• • . i'i
II ,CR1 ( I I
1 1
9HT FPP^AT(5X. • AMOUNT OF SALT LFAVINT, THI ROOT ?ONF r'.FS.?
I ACRE'!
URITE(fi.90tlCHLT
90« FOP«AT(SX.*nEPTH OF LE«CHING WATFR r'.Fc.j, • INTHFS • )
URTTE<6.9nS)RLT
9US FOPHATJ SX. 'LEACHING REOUIRfMFNT r'.Ffi.?.' Pf RCFNT ' !
MRITE(Kt90F)TET
90F FPRHAT(SX. 'DEPTH OF EV APOTP « MS P IV i T TON r'.F=.7,
«PO() CONTINUF
RFTUBN
FND
TONS
201
-------
INPUTS LAYER RK OFC
1 .17 .78
7 .12 .7fi
3 .11 .78
» .11 .28
S .10 .28
f> .09 .28
^ .08 .28
8 .07 .78
9 .OS .28 .
in .no .28
11 .03 .78
17 .03 .78
Cr ?.no 0*= .in L = l?l KH-W KMl= P
INITIAL SOIL CONDITIONS
LAYER
OB
CB
IMHHP/CN
1
7
3
*
S
6
7
8
9
in
ti
12
HWEOIAT
SOIL
LAYER
1
2
3
4
r
6
7
8
9
in
1 1
17
TOTAL i
ET PRIOR
-to
.13
.15
.16
.17
.17
.18
.19
-19
.71
.77
.73
ELY PRI
S»LT
T/AC
.2601
• ?4?0
.7738
.7053
-I'm
* 1693
. mi .
.1331
.1149
. H959
.PTRS
. Ofinn
.9717
5.98
4.78
3.43
2.95
7-53
7.79
1.93
1 .61
1-39
1 .05
• «?
.60
OR TO
MOIST
CONT
. i nnn
• i^no
. 1 5 no
-if.no
. I7nn
. 1 7nri
. IBOP
• 1 9nn
. 1 9fio
.7100
.7701)
.73nn
TO I PR IG 1 =
1 OAT ET
1 .09
7 .10
3 .10
4 .in
5 .11
6 .11
7 .17
B .17
9 . 17
ll1 .13
11 .13
PRIG 1
CONC
MMHO/CH
5 .9»nn
4 .7800
3. 43 00
7. 9" nu
7.53110
'i .7" no
1. 93 nu
1 ,6ino
1 . 3" no
1 . 115 fill
.a? nn
.60IIU
.nn IN
DAY ET OA»
1 7 . » 23
13.5 74
14 , f. 25
15.7 26
16 . 8 27
17.9 78
1 ft .70 29
19 .i-0 30
20 .70 31
21 .70 37
22 .71 33
GT n
( MMHO/CH 1
118 5.CII1
(j • r. . 1 8
P8 5.36
08 5.55
US 5.7!
08 5.91
08 6.09
08 6.27
08 6.45
08 6.64
OB 6.8?
08 7.00
CTTOL: .001
ET DAY
.71 34 .
.27 *5 .
. 2' 36 .
.23 37 .
.2* 38 .
.25 39 .
.25 «n .
.26 41.
.26 42 .
.27 43.
.27 44 .
AFTER IRDIG 1MTFRV AL 1
SALT HOIST
T/AC CON!
. 20" 4 .748°
.2615 .7580
.3017 .7596
.3276 .7598
. 3 4f. 4 . 76 1 7
.3395 . ?63r
.3245 .7653
-29in .767?
.2436 .2708
.1»C6 .7727
.1 276 .7745
.075P .7745
'.01 74
nFPTH iRRir. jz
S «LT L EAVING i
LFAC^ING UATfO
LEACH REO: .n
FTtlNTERVlL \-
riNC
MHMO/ CM
1 .IP °?
2. 37^F
7.5* 93
2.8«'P7
7.1906
f . 16 77
2. "118
7.5057
2. OF 73
l.Sf SO
l.n?7H
.67HS
7.5R I N
.III. I/AC
- . • |M JK
1 """'f.FNT
1 . 1 '• IN
DA ILY
ET DiY TT
77 »S
77 46
27 47
78 48
78 49
28 5Q
78 51
28 5?
79 S3
29 54
79 55
AFTER
SALT
T/AT
. 'f. « 6
. ?«\<\
. 31 7U
.339°
. 3* 'ill
. 35 u 3
.3' 46
.79 = 1
. 74 OQ
. 1 R P.P.
.1?"3
.0750
3.1 7S
• EPTM
" ALT L
F & rp ?
LF ACH
'.79
.30
.3(1
.30
. I'j
.3fl
.W
.51
. Jl
.31
'.11
FV AFl)TR»N^'' IHATIO'
« I HC Mf
DAY ET
56 . 3?
* 7 .37
5 » . 5;
5 •» .32
60 .37
61 .31
67 .3D
63 . < U
64 . V,
65 .79
56 .2->
IRR1G INTfRVAL 7
HO?ST
TINT
.''13
.<>'iS6
,?«8 S
.7 4B5
- 7 51 3
.?l:'l ?
.7 «;•» i
.759°
. 7 f.«. 7
. 7 F.f> '
.7 71 u
.7 71 <1
( wc-N
ri.7^ U,
S I
0»V FT n»
67 ,7«
6« .79 •">
(.0 .^0 pp
7i> .79 PI
71 .7P 87
77 .2" P3
7^ ,7« P4
74 ,?p ««.
75 ,?F ft4 1
. 3 P3 5
. 3 c.r- r.
. *. 1 6 • .
. ?S° 7
. 1 940
. 1 ^7 '
.1-77..
'..4?f,
fPlf i-'
'.'LI L 1 f
. . . , (J | .
T L!Tn -
r T . I M ; '
» F' OA t E T
.?"( 89 .24
.77 «, j . 2tt
.77 uj .2}
.77 H^ .73
.2R 93 .23
.76 94 .22
.75 '5 .22
.25 ^6 .22
. 7' Q7 . 2/
.?"• ""F. .2<
. 7 c i^ ,J2
Ri r- l«TrHvAL 3
fOISI r ONC
rCNt MMHO/fM
.^1 4h ' . 195K
./>*'iU 3 . 1?48
. ^3 7P 3 . 1
.^U55 3.5'' lr
. •>.:.',•••
v t «.-/..;.. T .
PAY FT DAY ET DAY El
100 .22 111 .20
1 r, 1 . / 1 112 .20
112 .05 .2254 J.5743
.37qi .2300 3.7915
.4084 .2300 4.0830
.4322 .2345 4.2368
.4337 .2391 4.1707
,4()Su .2436 i. 8223
.3513 .2482 3.2547
.27S1 .2573 £HVAL 4-2.73 IN
H
X
§
TI
i—1
0)
TO
O
C
a,
i-i-
n
rt-
0)
H
CO
i-"
O
3
-------
AFTER IRRIG INTERVAL «;
AFTF9 IQPIG INTERVAL 6
IRPIf,
8FTFR IftKTC *NT£PV«.L P
AFTER IRRIG INTERVAL
SALT
T /AC
.7976
.3645
.4114
.4571
-491O
.5057
.4778
.4038
.3111
-?18»
.1 380
.0813
4.tS57
HOIST
CONC
CONT MM HO /CM
.1967 3.4778
.7712 3.7885
.7261
.7761
.7310
.7359
.7408
.7079
.6475
.9163
.9084
. 5134
.7457 3.7778
.7555 7. 7Q91
.7604 1
.7653
.7653
.9785
.1957
.7046
SALT
T/AC
.7906
.3664
.4333
.4983
.5574
.5846
.5580
.4 738
.3534
.2366
.1455
.0841
4.S820
MOIST
CONT
.1910
.71 72
.2771
.2274
.7777
.2329
.2381
.24 34
.2538
.2591
.7643
.2613
CONC
HMHC/CM
3.4969
3.8778
4.4785
5.1501
5.6783
5.7700 '
5.3867
4 .4758
3.7002
7.0496
1.2653
.7317
SALT
T/AC
. 7577
.3206
.38S»
.4587
.5389
.6060
.6355
.6064
.11 55
.30 79
.7643
.1657
5.1476
HOIST
CONT
.1 9f 14
.?21U
.7259
.2259
.7308
.23' 8
.7407
. 7456
.? S«.4
.261)3
.765 3
. 7 65 3
roNC
MMHO/CM
3 . Cl 1 "• °
1 . 3 3i> 2
3 ,° 71 u
4.6671)
5 . 3 f,6 9
5.909?
6 . 0 70 3
S.f, 767
4.6 34 ft
3.0?1- 7
? . 7 90 o
1 . 4 36 2
StLT MUST
TONC
T/AT r<-lNT MMHO/CM
. >U7 3 ,7|. 1? 2
. 79SS .7 ? Ml 3
. 3«69 .??,',"> 1
.*TRu -MB 3 S
.64*5 .7*29 6
.K 71f .?i, 7fi 6
. f>3P? ."-'Sf.8 S
.S 1? 3 .76 IS 1
.418] .?(, 61 3
• 79S7 .7h6l 2
S.S7F. 6
.P^ 55
.02 7'
.16 15
.1275
.(H 34
.Si 68
.U893
.2367
.71.fi
.7b79
.6122
.Sb i»4
SALT
T/AC
.2161
,2n 66
.3275
. JflOl
. 1511
.5342
.6187
. 68 35
. 70 IS
. 6521
. S5i6
. 431o
5. 86 73
MOIST
CONT
.2086
.2296
.2338
.2338
.2380
.2422
. 2461
.2SQ6
.2590
.2632
.2674
. 2674
CONC
MMHO/CM
2.7155
2.8697
3.2205
3.7407
4.3576
S.0704
5.7720
6.2704
6.2260
5.6957
4.7592
3. 7109
OfPTH IPRIG 5=7.7^ IN
S*IT tCAVIMG: .DO T/AC
LEACHING UATCRr .00 IN
tFACH REPr .00 PFBCENT
ET.INTERVAL 5=2-91 IN
DEPTH I»RIG 6=2.91 IN
SALT LFAVING; .00 T/AC
LEACHING UATER= .Ot< IN
LEACH RFOr .00 PERCENT
ET,INTERVAL 6=3.11 IN
DEPTH IRRIG 7r«.fu TN
SALT LF*VINRT .11 T/4C
LESCHlNf, MATERrl.SD TN
LEACH RFOr 32.77 PFRtFNT
ET.INTERVAL 7:2.95 IN
flrt>TH IHPTP d=M.77 IN
SILT LE»VlN
SALT
T/AC
.7536
.'906
.3764
.3724
.4354
.5137
.6071
.6846
-7334
.7180
.6445
.5317
6.1065
DEPTH I
HOIST
CONT
-7168
.7354
.7391
.7391
.7428
.7466
-750S
.254U
.7614
-7651
.7689
.7689
RBtr, if
CONC
MM HO /C M
2.6892
7.0377
3. 1 SB 2
3. 5803
4. 1720
4. 79DO
5.5303
6.1469
6.4498
6.7753
5.5107
4. 5468
I-"*. 95 T N
SALT
T/AC
.2582
.2933
.3761
.3669
.4224
.4930
.5776
.6667
.7367
.7538
.7127
.6221
6.2296
DEPTH 1
MOIST
CONT
.2208
.2382
.2417
.2417
.2452
.7«87
.2*21
.2* 56
.2626
.7^*1
.2696
.7646
PRIG 1 1
CONC
MMHO/CH
7.6884
2.83117
3.1U20
3.4901
3 . 96 10
» . 55 76
5.2663
S.9962
6.4500
6.51 75
K.0786
S.3PS3
1=3.75 IN
SALT
T , «C
.2628
.297*.
.3? 91
.36 70
.41 71
.48 1?
.5601
.K1 43
.7301
.77O4
.75 76
.691?
R.31 39
DEPTH t
MOIST
CONT
.773f
.7407
. 713S
-2 135
.2 168
. 7 50 7
.2535
.2 56 "
.26311
.7 66 7
.77HI
.7 TOt
RR I G 1 7
CONf
MMHO/^M
2 .7 ril B
? .S "79
3.1 OGf.
3.1 64 3
3 . P P.7 i
1 . 1 77 7
S.079 7
*." !?•>
6 . 3 71 5
f,.fc 395
R.I up 9
« .9 837
:T.51 IM
S»LT
1/1C
. ? 97 7
.I 796
.35«7
. '9FS
.ni|7 3
.S IfiJ
.5673
.E.7S 7
.7««3
. 7 P*4
.7*911
.7 OP 3
t.r c,7 s
f'fr TH i
W01S1
rn NT
.?« (M.
.?(-. .Ill
• ?R if'
.70 nil
.?POP
.7PIIO
.7801'
.780(1
.7*00
.7PilP
.7801
. ?B nr>
URI r i
TONC
HHHlJ /CM
7.4J2R
2 ,7Db7
?.^ii 90
3 .7SSU
3 .f-7 79
4 . 1 g 93
1 .«? 22
S.S« 77
R .1 5 71
R.I it fl*.
6 . U ID
S .7u 9?
i:j .'i« IN
SALT LEAVING: .33 T/AC
LEACHING UATER=1.«3 IN
LEACH REO=36.28 PF»CENT
ET.INTERVAL 10=2.73 TN
SALT LEAVING: ,» PCfNI
r T , JNTf o v i ] <- .[> j ] M
SEASON TOTALS
ntPTH OF IRRIGATION W«TER = X^.ST INCHES
•MOUNT OF SALT LEAVING THE uofn ?ONE r 1.91 TONS PFP ACRE
DEPTH OF LEACHTNG U»TF<' = 9.57 INCHES
LEACHTNG REOUTOEMFNT - 70.89 PERCFNT
DEPTH OF EVAPOTRAWSPIPATION : 78.19 INCHf.
-------
Example 2 - Short Output Prediction Version
1 •->••
c
I VI
0 "Y
1
7
7
4
=>
P
7
8
<-!
10
11
17
1 3
1 1
1 5
1 6
17
18
U 1 >
7. Oil
TIAL
LAVE
1
?
3
1
*.
6
7
8
9
10
11
17
ET
.09
.10
.10
.10
.11
.11
.17
.12
.12
.13
.13
• It
.15
.16
.17
.18
.19
.20
SOI
R
•
•
*
•
•
•
.
•
•
»
•
•
HA
1°*
70
21
2?
23
21
25
76
77
78
29
30
31
32
33
3U
35
36
OX r
La
1
1
1
.50
L CONOTTIO
Od
(
10
1 3
!«;
16
17
17
18
19
19
21
27
73
Y ET
.20
.20
.2J
. 21
.21
. 27
.23
. 23
.21
.25
.25
. 26
.76
.77
.27
.77
.27
.27
TH
MMHO/C
c.. 98
1.28
3.13
7.95
7. 53
7.79
1.93
1.61
1.39
1. U5
.82
.60
PAI
PAY
37
38
39
ID
11
12
13
11
15
16
17
18
19
50
51
52
53
51
Tt W
1
2
U
f,
7
9
il
1
2
L -1
MS
M)
LY F
ET
.28
.78
.78
.28
.78
.?<»
.79
.29
.79
.30
.30
-30
.30
.30
.30
.31
.31
.31
WH.
. 1 7
. ) 2
. 1 1
. 1 1
. If)
.08
.07
.115
. 1 l *
?1
I
T<>TAL
V.POTP
( INCH
OAY
55 .
56 .
57 .
58 .
59 .
6U .
61 .
62 .
63 .
61 .
65 .
66 .
67 .
68 .
69 .
70 .
71 .
72 .
pr r
. "f-
.78
. 78
.78
.78
. 78
.78
. ?8
.7°.
. 78
KH--
HHF
c
( T
. 7
. 7
. ?
.2
.1
. 1
.1
- 1
.1
.0
• 0
.r.
1.9
AN<
ES)
ET
31
3?
77
32
37
37
31
30
30
30
29
29
79
79
29
29
78
23
1C
l"! I A T r
4LT
/6C )
60 1
120
?"*. 8
nr, 3
971
F9 3
si 1
331
119
O C Q
' o »
FOO
71 2
"MAT
DAY
73
71
75
76
77
7P
79
80
81
8?
83
81
**•
86
87
88
89
90
KM
0
• 1 *
.U
• L1
. 1 1
.1'
.('
.0
.0
.u
.('
1 : n
LY PRTOP
M f
1ST
r ON T ( M
. 1
. 1
. ]
.1
. I
. 1
. 1
. ]
. 1
.7
. ?
. 7
m-ii s
^iifi (4
son .3
oU n 2
7Ufi 2
7b'l 2
80 n 1
^00 \
9l''T 1
inn i
/»nn
30'i
1 V T
i MMi-i"1. /r* i
8 «-. . r • i
8 5.18
i\ ^ . ^ r
4 5.7 3
R e .9 1
« '•> . U n
fl c, . 7 7
f. f . 1 5
P, f-. . f 0
A 7 . P I,
rrTOLT .K:)
TO IPRTo 1
CONG
HMO /CM)
.9?r ii
. 78|M,
. i *pn
. P 5 n o
.5 "*OO
. 79|i('(
. 9 300
.6 Hili
.3«f LI
. t">5lll!
. 8 ?l'n
.^nr-(j
PPIO" fTr .{M.
10W
FT
.7*
.28
.?*
.7°
.28
.78
.27
.27
.27
.26
• ?f
.75
.25
.25
.75
.75
.71
.71
OAY
91
97
°3
91
95
96
97
98
99
100
101
102
103
inn
IPS'
ID 6
107
108
FT OAY f'T
.73 1 IJ9 . -M
.7T 1 in .?ii
.73 11] .71
.7? 11^ . ?u
.77 113 .7P
.7? Ill ,7i
.7-> 115 .70
.77 116 .71.1
,7? 117 .7U
.7? 118 .?il
,?1 119 .71!
.71 l?f! .19
.'1 171 .fiO
.71
.71
.71
. '1
,71
204
-------
AFTER
INTERVAL
1
2
3
a
5
•;,
7
1
9
111
1?
1 \
TASON
SALT
EXISTING
( T/ AC )
3.D?
3. 1^
3.«3
S. 7c;
«*. IT
U. 5<*
5. 1U
5. S3
5. Q7
fi. 11
fi. 31
&. fin
f>. 60
CAI T
LE AV IN '
( T/ ar )
.un
.no
.00
.iJd
.mi
,!jn
.11
.?(^
. 3«
-33
.<*?
.un
1 .07
WATFr LF'CMINT.
(
7
I
I
7
7
7
q
(4
U
1
3
1
US
TN )
.Sf
.III
.7?
.3f
.73
.^0
,f.o
. 77
.R1
*g!
.51
.T°
.57
( IN 1
.un
.Ul>
.Of
.or
.on
.ijn
1 .50
1 . °>7
1 .S3
1 .'43
1 .«?
.01'
-> .5?
LF4CM II' P
( p r P (• i- h. T )
• 1 • ;
.l-i'
. nil
. 1 IL
. til,
.P-i
37. 77
3S, 1 7
3<>. K°
un"u'°
aii. «4 7
. f'P
71 . P 1
205
-------
FORTRAN Listing of Evaluation Version
1* f THIS VERSION DOCS NOT ITERATE ON DEPTH APPLIED. INSTEAD BOTH DEPTH AND
?• C CONCENTRATION OF IRRIGATION WATER ARE INPUT
I* C UTAH STATE UNIVERSITY
»• C PROJECT WG S« FUPCA
«;• C DEFINITIONS
6* C C IS THE CONCENTRATION OF IRRIGATION WATER HKHO/CH
T* C CB IS THE AVERAGE INITIAL CONCENTRATION OF THE SOIL SOLUTION HMHO /CH
8* C CE IS THE CONCENTRATION OF MATER ENTERING A LATER MMHO/CM
•»• C CF IS THE FINAL COCENTRATION OF SOIL SOLUTION MMHO/CM. JUST BEFORE
IB* C THE NFXT IRRIGATION
If* C CFC IS THE CONCENTRATION AT FIELD CAPACITY
1?* C CL IS THE CONCENTRATION OF WATER LEAVING A LAYER HHHO/CH
IT* C CT IS THE CRITICAL CONCENTRATION OF SOIL SOLUTION MMHO/CM
1C* C OT IS THE THICKNESS OF EACH LAYER FT.
1«?» C DO IS THF DEPTH AP PLIE O/ IRRI G ATION
16* C DE IS THE DEPTH OF WATER ENTERING A LAYER
IT* C DL IS THE DEPTH OF WATER LEAVING A LAYER.
!«• C ET IS THE EVAPOTRANSPIRATION INCHES
1<* C I DESIGNATES A PARTICULAR LAYER
?0» C I CHECK INDICATES WHICH FIELD DATA CHECKPOINT IS APPLICABLE
71* C J DESIGNATES A PARTICULAR IRRIGATION
??• C KF IS THE FIRST DAY OF A GIVEN IRRIGATION INTERVAL
?3« C KK IS THE LAST DAY OF A GIVFN IRRIGATION INTERVAL
?•• C KM IS THE NUMBER OF DAYS IN THE IRRIGATION INTERVAL
?S» C KN1 IS THE NUMBER OF DAYS FROM INITIAL SAMPLING TO FIRST IRRIGATION
76* C L IS THE LENGTH IN DAYS OF THE PERIOD UNDER STUDY
77* C N IS THE NUMBER OF LAYERS IN THE ROOT ZONE
?8* C NB IS THE NUMBER OF THE BLOCK BEING IRRIGATED
74* C NI IS THE NUMBER OF IRRIGATIONS DURING THE PERIOD UNDER STUDY
3fl* C NP IS THE NUMBER OF PERIODS BEING RUN
3i* c OB is THE INITIAL MOISTURE CONTENT VOLUMETRIC
37* C OF IS THE FINAL MOISTURE CONTENT JUST BEFORE THE NEXT IRRIGATION
33* C OFC IS THE MOISTURF CONTENT AT FIELD CAPACITY VOLUMETRIC
*•• C OT IS THE CRITICAL MOISTURE CONTENT VOLUMETRIC
3S* C RK IS THE PERCENTAGE OF MOISTURE EXTRACTED FROM A SOIL LAYER
36* C WTPA IS THE AMOUNT OF SALT IN A GIVEN LAYER
37» DIMENSION CB«20» . 08 < EO I .OFCI M I . 9T I 20 > . CT (?d > »RK I 70 » .WTPA ( 20 > t DE I 2
3d* 1 or.CEIPOI»OLI20).CLieo>.OFI20l . CFI80I «CAII20».ET U5OI.C8T 120).
34* 2ETT( isor.wTPAit2or.cFT izov.cnoi .Dctloi.Kni 30 r. SB 11201 .»F 11201.
«!• DATA AST. BLANK /1H>.1H /
• 2* REAO(St?)NP
43* ? FORMAT(I2)
««• ICOUNTrl
BS» 1»EAD(5. 100) DX.N.NB.ICHECK.NI.KH1
«K* 100 FORMATIF3.0VSI2I
«T* REAOC5. IDT) IDDIJ) tJ=l.NI)
»«« READC5. inr>tC«J)WJTl.NII
• 4* READ(S> SSOXKMIJI t J = l .Nil
sn* sso FORMAT c«nr? )
SI* TFdCHECK.NE.l IGO TO 400
S7* REAOIS.«or>IOB(I)«I=l.N)
S3* tOl FORMAT113FE.D)
54* PEAO(S.«OD (C8(I ).!-!. N)
SS* READ (5. 10D (RK (II .1 = 1 .N)
56* RFAOIS. lODIOFCdl.Irl.NI
S7* REAOIS.inr* IOT(I ) .1=1 .N)
Sft* RE AD I S« 101') (CT II It 1 = 1. N I
St* 101 FOPMATI 16FS.O)
K0« knO L = KN1
61* DO SOD Jrl.WI
fi?» SOO L=L»KH
63* 3 RE»DC5.102MET«KI.K = 1.LI
6»* 107 FORMAT I 20 F* . 21
65* J=l '
fifi. KFrl»KMl
£7* KK=KM(J(*KM1
CM* WRTTE«6,»02)N8.ICMECK
6
-------
T8» 21 OAT ET OA» ET DAT IT OAT ETM
7«;* 1JT8 FORMAT! I£.F7.3»F8.2r«X.«l IS.F4.2M
BO* NX=IL-1»/»»1
8t* 00 <0< I = I.IT
HZ* URTTF.(6»tOH) I .OB ( II .CB< I) . ( LL t ETC LL I . LL = I. L.MX I
S3* kO« IFII.ro. NXIGO TO «OS
84* HO! FOR»UT IL LET (UK ,LL=H. L.NX »
SS* GO TO kPS
s<»* »os TFII.E~O.N» GO TO «ne
«W* 1 = 1*1
SI* WRITER. 1991 It IiOBIIII .Ceill >.II=ItN)
«»2* 1OS FOB»*TII6.FT.l.Fi.2l
SU* H06 NIl^NI*!
<»»• 00 » Hri.Nl 1
•)!>•
<«fi*
97* DO 1* 1 = 1. 'N
98* Or (OFCt I I-ORII II »OI«
44* I* <;»»±S»M»0
inn* iFiKRi.ee. oi'Eo TO ?i
int'» oo s I=I*KNI
S ETT( llrETTt 1I»FT (II
no «u 1=1. H
OBS-OB(I)
OR (I IrOBCI »- CPKC I) «FTT (1 II /
IF (OBI I) .GE.O. » GO TO 380'
lid* 380 CRII )=OBS*CRS/ORII >
III* ?3 TSP»tO'.0
1I?» IFIJ.NE.ll GO TO S75
Ut* 00 11 1 = 1, N
I IV* MTPtlI>=BB( I I»0(*0.890«*CBIT »
115* 11 TSP» = T«>P»»WTP*CI I
11R* GO TO ?17
117» 57S SAH=0.t)
tiff* 00 SOS 1 = 1. M-
11*7* 0=<9FC< I I-OBI1 » *OX« 12'.0
l?n* SOS StM=S*H»0
171 • 217 00 16 I=KF.KK
l?2* 16 ETTIJ»1ISETTU»II»ETII 1
173* CF(l)=C(JI
!?«» 27 OFII)=DO(J1
I?S* 00 15 1=1 t*
126* OFC=«FC(t>*12.n*OI
177* OFX=OBII )*DX*l?.n-
128* OTOT»L=OE«I)«DEX
12»1* irinTOTAt.GT.OFOSO TO 20(1
tSH* 0»I=DTOT»L
131* 8»I( II=0»I/(12.«OX1
132* 60 TO 62
i"?3* ?nn OAK II=OFC«I i
13** DL (I J = DEfI >- (DFC-OEI t
|3S« ER=Ot«H/OFC
I3fi* OEX=OB(M
I 37* CL«I )=PF(9EX.£RI •IDEII >• CE 1 1 >»OEX* CB ( 1 1 I/OLI2I
|3B» CAK II=IOEX*CB(I I»OE(I I*CE(I HOL(ll»CLCII I/OFC
13-)* 60 TO 66
1*0* 62 DL«II=(r.'
1*1* CL=DLCI»
MS* IFU ETTt Jl^nl.0001 t .6T.DDIJI) 60 TO 67
MR* ULPA=OLfN)*CL(N)»0.870*/l2!.tf
M7* 60 TO 58
|M* 67 WUPAtO.O-
!»?• 68 00 17 1=1.*
t«i»T* OF(I)=CAH II-IRK1I »*ETTIJ»1) »/
1M» CF(II=8»I( II «C«I (I»/8F(I I
1ST* IFIOFdl .SE.OVI 60 TO IT
153* BFIT)=0.
IS«* 17 CONTINUE
1SS* TSPAldOitl '
156* 00 373 1=1. N
|57* UTPAlMI =«F( I) *OI*.arO«*CFII I
158* 323 TSPA1STSPA1»HTPA1M»
15*J* «l? 08 »1S Irl.N-
160* IFICFdl .ffT.CT IIII60 TO «17
IC1* CFTIIlrBLANK
207
-------
IK7* GO TO S7S
IR3* »1 7 rFTt I)=AST
Ifi*. 375 IF IOF( I) J-T.OT II >) GO TO 37f,
IfiS* OFTCD-8LANK
Ififi* GO TO 113
Ifi7» 37C OFT( I» rAST
>6B» «13 CONTINUE
«&<)• TFIJ.NE.l) GO TO SOG
|Tn« 00 177 I-l.N-
»7t» IFICB(I) .GT. CT (T I) GO TO *15
17?* CRTII)=BLANK
I71» GO TO » IB
17*. »15 CBT(lt=AST
ITS* «1K IF-IOB(I) 4.T.6T (T It GO TO 178
176. ORT< I)=BLANK
177* GO TO 377
»78» 37B BBT< I)=AST
171» 377 CONTINUE
I Sn* WRT.TEIG.h03)Cll) .DX.KMII1 > .KM]
I«l« »03 FORMATI'1C: •.FS.2.«X.*OX = •tFk.2•»*•'KM= «.I?.k08>J.J
183* 408 FOftWATCOCONDITIONS IMMEOIATFXT PRIOR CONDITIONS AFTER IRRIGAT
18»» 1ION*/' TO IRRIGATION«,I3t17X.'INTERVAL*.I3/«0 ' SOIL SALT MOIST
IBS* 2 CONC SALT HOIST CONC*/ • LATER T/AC CON T HHHO/CH
I8R« 3 T/AC CWT HNHO/CH")
187* URITE(G.«1«) (T.WTPK II ,OB( II .OBT 11 ) .C8111 , C8T \ 11 ,VT P» 1 (I J . OF (I I . QF
188» ITCH .CF« II tCFT (I ). 1 = 1.N)
18
WRTTEI6.7IUTSPAI :
711 FORMAT1' TOTAL * .F 8. rf/>
?DTT» 7On~URITEIG.317IJ.DDIJ)
'DT* 312 FORMAT!' DEPTH OF UATER APPLIED FOR IRRIGATION'.13.' ='.F5.2.' INC
XHES')
WRTTEIG.313IWLPA
21U* 313 FORMAT!' AMOUNT OF SALT ENTERING SATURATED ZONE =«.F».2.» TONS PER
?lf» I ACRE'I
?!?• CHL-DDIJ>-SAM
71t» WRITEI6.31SICHL
7»«* 315 FORMATI' LEACHING WATER ='.F|1.2.' INCHES' I
RLrCHL. 1DO!.0/DO( J)
WRTTE(6.31G)RL
7IT* 316 FORfATI' LEACHING PFRCENTAGE : '.F7.2.' PERCENT')
71** IFIJ.NE.1.0R.KM1.EO.OIGO TO 777
719* URITE(6.m8) J.ETTI1)
770* «18 FOPMATI' ET PRIOR TO T RR IGAT ION'. 13 . • ='.F5.2.* INCHES')
771* 777 WRITEI6.31«IJ.ETT
777* DO SOT 1 = 1.N-
778* OBII)=OF(I)
72"»» 501 CBIDrCFII)
730« IFU.LE.NI) GO TO ?7
731* IFIICOUNT.EQ JtPI 60 TO 512
73?* ICOUNT=ICOUNT*1
733* 60 TO 1
7M» 51? STOP
73S* END
208
-------
001 000 FUNCTION PF
OC3 OCO OATA((All.J> i J=l .3) .1 = 11 51/- .6 5575 . T .C434.. -70. 53 £ • .4 58 r 8 »- •*. 118: t
OOt ODD X22. Silt-.011719t 1.1(081.-11.7 11 .- ,P197'7. -. 3r It 3. 2 . 51 71, .03"7P1 •
005 000 X-2.4S02.15.651/
006 000 DO 10 1=1.5
007 000 10 B(T)rA(I ,1)»A< I. 2)«OFX + A( 1.3 >»QEX»»?
008 000 IF(ER.LT.O.Z) GO TO 1
009 000 IFIER.6E.0.2.ANO.ER.LE.3.) GO TO 2
010 000 3 PFLOO=B«1)»BC2»»*UOO(3.)»BI3)»CALOBI 3.1 l»«2*B«1)»C»tOr,«3.n«»:+B'5
Oil 000 X)/3.
012 OCO PF3=EXPCPFLOO»
013 000 8(9)=B(2)+2.«B(3)»ALOG(3.I+3.«B(1).(ALOG(7.I)««?-8(5)/3.
Oil 000 B(81=PF3/3.»*B<3>
015 000 PF=B(S)»ER**B(9)
016 000 IFIPF.GT.l.) PF=1.
017 000 60 TO «!
018 000 1 PFL06=Btl) + 8(2l»»I.OC«.2l»8«'n«**2-B(5I/.2
022 000 B(6)=PF2/.2»*8(7)
023 000 PF=B(6)*ER««B(7l
024 000 60 TO 4
025 000 2 PFLOG=B(1I + B(2)»ALOG(ERI+BI 3UCALOCIER) )« • 2»B( 4I« I ALOG (ER H •• 3 + BI1;
026 000 Xl/ER
027 DOC PFrEXP(PFLOG)
028 COO 4 CONTINUE
029 OCO RETURN
030 000 END
209
-------
Example 3 - Sample Output Evaluation Version
IWUTS
BLOCK S,
LAYER
1
I NI T I AL
L AYER
1
7
3
4
S
6
7
8
9
If)
11
SOIL
OR
.18*1
.194
.774
.746
.740
.746
.764
.786
.31 4
.345
.379
4
S
6
7
8
9
in
11
CO NO IT IONS
CR
(MMHO/ CM )
4.71
4.71
3.09
3'.n9
7.94
7.94
3.73
*. 73
3.14
3.14
7.84
RK
.4 1
.3n
.1 9
.10
.nn
.on
.on
.00
.00
.01
.on
DAILY
DAY ET
1 .71
2.19
3 .15
4 .DO
5.13
6 .20
7 .00
8 .Dd
9 .20
10 .24
11 .28
OFC
.311
.311
.311
.311
-311
.319
.330
. 3 SI
.385
. U OF.
-41S
OT
.08
.08
.0 6
.08
.00
.00
.ntl
.00
.Dfl
.00
.00
EVAPOTRANSPIR AT
( INCHE
DAY ET
12 .78
13 .76
14 .75
IS .76
16 .26
17 .26
18 .26
19 . 3D
20 . 37
21 .35
77 .77
S )
DAY ET
73 .72
24 .74
2S .73
26 .76
27 .HO*
28 .00"
29 .nn"
30 .DO
31 .74
32 .77
33 .25
CT
(MMHO/CM )i
4. OH
s. tin
6.00
7.00
l on .'0 o
1 nn .'D o
inn. oo
100 .'DO
ion. no
1 nn .'o o
inn.'no
ION
DAY ET
34 .23
35 .23
36 .27
37 .31
38 .34
39 .31
40 .25
41 .22
42 .17
43 106
Cr 1.77
DX- .SO
KHz 11
CONDITIONS IMMEDIATELY PRIOR
TO IRRIGATION i
KMlr 7
CONDITIONS AFTER IRRIGATION
INTERVAL 1
SOIL
LAYER
1
7
3
4
5
6
7
8
q
10
11
TOT AL 4
SALT
T/AC
.3710
• 3977
.3fll7
. 33na
-3071
-3148
.3711
.4(170
.4291
.4715
.4684
.16*47
MOIST
CO NT
.1709
.isnn
.1961
.7^13
.74 no
.7460
.7640
.78611
.3140
.34SO
.3790
CONC
MMHO/CM
7 '. OS 33 *
' 6Ln916»
3.5790 *
3.?«59
? . 94 no
2. 94 no '
3.7300 *
3.2300
3 . 1 4 no
3.14DO
?.84nn '
SALT
T/AC
.3031
.4845
-B097
.3797
.5071
.3148
.371 1
.HOPn
.4291
.471 5
.4684
4.441 0
MOIST
CO NT
. 13 68
.1835
.7303
.2228
.2400
.2460
.2640
.7860
.3140
.345n '
.3790
CONC
MMHO/CM
5. (1931 •:
6'.tf675*
5'.O871
3.9150
7.9400
2. 9% 00
3. ft 00
3. 2*5 00
3 . 1 ft 00
3. 14 DO
2 . #4 00
DEPTH OF WATER APPLIED FOR IRRIGATION 1
AMOUNT OF SALT ENTERING SATURATED 70NF =
LEACHING WATER - -7.93 INCHES
LEACHING PERCENTARF 3 -97.73 PERCENT
ET PRIOR TO IRRIGATION 1 - .88 INCHES
TOTAL ET FOR IRRIGATION INTERVAL i - ?.ss
= 3.t>0 INCHES
.00 TONS PER ACRE
INCHES
210
-------
BLOCK S<
C z
98
KM r
CONDITIONS AFTER IPRIG INTERVAL ?
SOIL
LAYER
1 •
7 .
3 .
4
5 •
6 .
7
8 .
9 •
10 •
11 •
TOTAL 4.
SALT
T/ AC
2384
47Q3
6336
5157
3394
3148
3711
4070
4791
4715
4684
6543
MOIST
CONT
.1579
.1990
.7401
.7737
.7693
.7460
.7640
.7860
.3140
.3450
.3790
CONC
MMHO/CM
3.4689
5.4306*
6'.O642*
4.3>99
2.8955
2.9400 '
3.7300 '
3 .2500 '
3.1400 '
3.V400 '
2.8400
DEPTH OF WATER APPLIED FOR IRRIGATION 2 - 3.00 INCHES
AMOUNT OF SALT ENTERIN3 SATURATED ZONE - .00 'TONS PER ACR F
LEACHING WATER : -7.4fl INCHES
LEACHING PERCENTAGE - -87.73 PERCENT
TOTAL ET FOR IRRIGATION INTERVAL 7 = 2.24 INCHES
BIOCK5.1 C r 1. 5 3 KMrg
CONDITIONS AFTER IRRIG INTERVAL 3
SOIL
LAYER
1
7
3
4
5
C
7
8
9
in
1 1
SALT
T/ AC
.7598
.4587
• R939
• K424
.4778
.3K14
• 3777
.4070
.4791
.4715
.4684
MOIST
CONT
.1914
.7735
.755R
.7818
.3110
.3190
-77fiO
.78ftO
.3140
.3450
.379O
CONC
MMHO/CM
3.H83
4.7in9
6.2381*
5.7373
3.1741
2.6P31
3.1448
3.2300
3.1400
3.1400
7.8400
TOTAL 4.9877
DEPTH OF WATER APPLIED FOR IRRIGATION 3 - 3.DO INCHES
AMOUNT OF SALT ENTERING SATURATED ZONF r '.00 TONS PER ACRE
LEACHING WATER - -1.72 INCHES
LEACHING PERCENTAGE - -57.40 PERCFNT
TOTAL ET FOR IRRIGATION INTERVAL 3 - 1.75 INCHES
211
-------
BLOCK S. 1
C r 1.
KM r 6
CONDITIONS AFTER TRRIG INTERVAL
SOIL
LAYER
1
7
1
4
5
6
7
8
9
in
i i
T OTAL 5
SALT
T/ AC
• in??
• i76n
.6939
.6174
.4778
.1614
. 1777
. *»n?n
.4291
.4715
.4684
. fT4~74
MOIST
CO NT
.21*8
.1748
.7178
.7593
.1110
.1190
.2760
.7860
.31 40
.1450
.1790
CONC
MMHO/CM
t.1743
6 . 25 89 *
7.4911*
5.6917
1.1711
7.6031
1 . 14 18
1.2300 '
3.1400 '
3.1100 '
2.8400
DEPTH OF WATER APPLIED FOR IRRIGATION 4 =
AMOUNT OF SALT ENTERING SATURATED 70N F = .00
LEACHING WATER = -2.64 INCHES
LEACHING PERCENTAGE ~ -118.31 PERCENT
TOTAL ET FOR IRRIGATION INTERVAL
I.Dfl
5. DO
fi.DO
7.60
Ion. DO
1 on ."n o
ion .'DO
1 on .'0 o
l on . n o
I on .-n a
1 00 .'D 0
INITIAL SOIL
L AVER OB
i
2
1
4
5
6
7
8
9
in
if
• 719
.175
.713
.759
-111
.119
.776
.786
.314
.145
.379
CONDITIONS
CB
(MMHO/CM >
1.17
6.76
7.49
5.69
1.12
7.60
1-14
1.73
1.14
1.14
7.84
DAILY EVAPOTR ANSPIRAT ION
DAY
1
2
3
4
5
6
7
8
9
10
ET
.06
.12
.14
.13
.12
.15
.19
.23
.24
.26
(
DAY
11
17
13
11
15
16
17
18
19
20
INCHES )
FT
.29
.29
.77
.do
.70
.18
.17
.18
.18
.18
DAY
21
22
23
21
25
26
27
28
79
30
ET
.14
.13
.11
.18
.72
.11
.?n
.r»T
.22
.17
DAY
31
32
33 '
31
35 I
36 ,
37 ,
ET
.17
.19
.00
.21
.00
.22
.19
212
-------
C r
.94
DXz .SO
K Mir
CONDITIONS IMMEDIATELY PRIOR
TO IRRIGATION 1
SOIL SALT
LAYER T/AC
1
7
3
4
5
f,
7
R
9
in
1 1
T OT AL
-3027
.4760
.6939
.6424
.4>?R
-3G14
.3777
."»020
.4291
.4715
.4684
5 . P4'74
HOIST
CONT
.04 86*
.O503»
.1340
.71 78
.31 10
.3)90
.776O
.7860
• 314D
.3450
.3790
CONC
M HHO/CM
14.
21 =
11 „
f, .
5 .
7.
3.
3.
3.
3.
7 .
7«76*
7660*'
S99&*
/760
1741
60 31
144ft
73 OD
1400
1400
8400
CONDITIONS AFTER IRRIGATION
INTERVAL 1
SALT
T/AC
.2276
.501 8
. P i'5 3
.6474
.4228
.361 4
.3777
. U Of i J
-4 29 1
.U 71 S
.4 684
.3?ni
HO IS T
CONT
.1757
.712O
.7148
.1848
.31 10
.31 90
.7760
.7R6D
.^51 <*0
.3M SO
-3790
CONC
MHHO/CM
2.9769
5.4^91*
1 0.8*613*
7.9858*
3. 1741
2.6031
3.f44B
3.7^no
3 . I'k 00
3 . 1 U fJO
2.fl*00
DEPTH OF WATER APPLIED F0
7
R
9
in
ti
TOTAL 5
SALT
T/AC
. 1866
.4107
.918?
.9343
• 53nrf
.3K83
.3887
.un?o
.4791
.4715
.4684
.5077
HOIST
CONT
.7770
.2495
.?771
.79H5
.31 10
.3190
.3193
.7860
.3140
.3450
.3790
CONC
MMHP/CM
1 .889?
3.7875
7.7549«
7.3897»
3. "160
2.6577
2.7936
3.P30D
3.1400
3.1400
7.R4 00
DEPTH OF WATER APPLIED FOR IRRIGATION 2 - 3. DO INCHES
AHOUNT OF SALT FNTFRTNG SATURATED ZONE - '.00 TONS PER ACRE
LEACHING WATER r -1.4ft INCHES
LEACHING PERCENTAGE - -4R.73 PERCETJT
TOTAL ET FOR IRRIGATION INTERVAL 7 - 1.23 INCHES
213
-------
BLOCKS.? c - . n i KMT?
CONDITIONS AFTER IRRIG INTERVAL 1
SOIL
LAYER
1
7
S
f,
7
8
q
i n
i l
TOT AL
SALT
T/ AC
1KK9
umr
9187
MOIST
C.ONT
.7ft U
.31 in
roNc
MMHO/CM
i. SM no '
A ,
7 ,
7,
7.
.«»n?n
.U71S
> 14684
an
SR78'
TIRO
7^00
lunn
RUno
s.
DEPTH OF WATFR APPLIED FOP IRRIGATION 1 -
AMOUNT OF SALT FNTFRING SATURATED 70NF - .
LFACHING WATFR - -7.71 INCHES
LFACHIN6 PERCFNTAHF - -tiFn.'83 PERCFNT
TOTAL ET FOR IRRIGATION INTERVAL 3 - .Hi
US INCHES
TONS PER ACRE
INCHES
214
-------
APPENDIX B
DETAILED MODEL
FORTRAN Listing of Water Model
c».. •••••*•••..•..*.............*.. ...,.................*.......*..........
SALT AND WATER FLOW. l«* 7?
IF1"".! MAIN,MAIN
PROGRAM-SOU WATER.SALT .FLOW WITH PLANT UPTAKF.
C PROGRAM OF FTR. ?q,197?
C CONO TS LARC-FST W A TFQ FLUX AT HOT TfiM • T A A; Q FOR H(KK) CON«.ItNT » «
C FROM GUI OP HU )rGt I )
C CT«« IS LOWEST VALUF OF OFL T PFRM I T T FP- - IF AS LOW STOPS
C HCRY IS PRESSURE OF LOWEST POSSIBLr WATFR CONTENT
C OD TS ORFSSUPF TARl.F ( WE TT ING)ST ARTINT- WITH LOWEST PRIrM)RF
C 0 TS CONOIJCTI VI TY TAPLE STARTING WITH LOWEST W»TER rcNTFNT V"LUE
C PO SAME AS AROVF. EXCEPT STARTS F30M WFTTING
C C TS WATER CAPACITY AS A FUNCTION OF O.EPTH "FGINNJNG AT TOP
C DFLX IS DEPTH INCRFHF.NT
C W TS WATf0 rONTFNT AS A FUNfTIOK OF DEPTH nF{>lNNINC IT TOP
C H TS WATER PPESSURF AS A FUNCTIO* OF OFPTH RfCIKNlNf, AT TOP
C WATL IS LOWEST POSSIBLE UATEP CONTENT
C WATH IS HIGHFST POSST3LF. WATER CONTFKT
C CB TS A CONSTANT TO "ULTIPLY 0 APPAY HY--USUALLY 1. U
C K IS NO. OF nFLX INCPFMENTS .MM NO. OF TIMFS H»W PRINTFP.KIT K'O.OF A \7
C START HEPE FOR A NFW PROGRAM A H
C Ml IS TO PRINT H.U ARRAYS EACH ITF.R..TFR NO. OF V FLFMENTS A [H
C HROOT IS THF. ACTUAL ROOT UATFR POTENTIAL
C RB REPRESENTS PLANT UPTAKE ADDITIONS
C HLOU IS THF MINIMUM ROOT POTENTIAL ALLOWED
C HHI IS THF. MAXIMIM POOT POTENTIAL ALLOWED
C ET IS THE POTENTIAL FVAPOTRANSPIRAT ION, ALWAYS NEGATIVE
C WFDO IS THF WATER FLOW RATE AT THF SURFACE
C ETPL IS THF POTENTIAL T R ANSPIRA TI ON . ALW AYS NEGATIVE.
C TET IS THE BOUNDARY POTENTIAL ET,ALWAYS NEGATIVE,LTV ARRAY
C«**««»DD ,H.G'V'W'Pnp ' A< SEISS'SO'ARRAYS ARE OF SAME DIMENSIONS AT LFAST=KK
C...«,.SF«TET-V ARRAYS ARE OF SAME DIMENSIONS AT LEASTrlFR
C«««««»P«0'T«ARF OF FOUAL DIMENSIONS, =fi0 AT MOST
cl**»*»*»*»***»*»********«******************************************************
DIMENSION D0« 7SI.H(2SI.G( 25», Y I 25 1. W< 75 ». ROFI 2«i) . A«?SI. Sf (? 5»
DIMENSION SS< ?5 ».SD(?S) ,CI?SI ,B
-------
••••••••*••••••••••••••••••••«•••••»••••••«••••••••••••• •••««»•*•»»•
PEAO 163. ML to
A 11
l « in
REAO »T = 1 .KK )
KCrl
UFDOr- .009
ET:TFT< I)
LLrMM ft 10
REAOCS. 16S) > I i 1. NO)
R< 4D4S. IBS) (P( T) tlz It NO)
»E«0 IfcS. ( WIT > >I=1 >KK ) » ?5
REftO lf,5i ( VI T) .1-1 .TFR) 8 JT.
RE80 165. DELXtDETT .GRAVY tCONO. DrtU .TTME
RE80 165. TT.CUHT .TAA.HLOU.HHI. RRFS
PEOO 16S. HORY.HUET .U*TL> VATH.CB
REHO 165. ISF(I» .1 = 1 .IER J
READ 1S5. 1ST 1 1 I . Ir l.KK )
URTTE 1C. 161 1
URITEI6.163) K. MM.TFR .NB. WO
P{ 1 »=P( 1»»1.0E»03
T(l)=0.0 * V
00 <»on I =2. NO
T(II=OELW»TII-1 )
9PP P«I )=PCI)«1.0F«03
READ 165*100(1) .1-1 .KK»
SEI1I=SF(U
SMft XrS.O
DELTrOETT
TMrl.O-TT A 7F
TB3=1.0-TAA A 77
YMAXrWATH » 8?
DO 1M 1 = 1. KK
SS(II=SF(I)
SO»T»=SE .RDF (1 ),SF <1 )
00 3 1=7. KK
0(11=0(11* (P«T »-P< I-H
J=JW(I»-T<1) )/DELH*1.0
H< UrfPI J»1»-PIJ»I »«W( I) -T(J)|/OFLU*P( J)
C« I ) TDELW/ (P(J+1)-P(JI I
G(T)=H(I) A (if
WRITE J 6.16F) T«I ).P< D.TW.ni I),C(I ).DnU) .W< T) .HID.ROFd ).Sf (II
CONTINUE
DO ? I=N.NO
TW=0(I)
OdJrnill* «P«T I-P( I-1» )»CB*OfT-IF
? WRITF 16*166) T ( I ) . P ( I ) .T W. D» II
c»*» «••*•*»*»**••••*»•••»•**••••*•»»•••»•***•*****•*••••*•***************
C 0 IS NOW DIFFUSIVITY TIMES OELW NOT CONDUCTIVITY
WRITE (K.179)
DO S I=?.IFR.?
216
-------
S WRITE 16.166) V( I),V(I-l»tTFT(I-1 >.SFt 1-1 )
WRITE (6.180)
WRITE (6. 166) DFLX.OFTT ,GRAW.CONO.OELW.TIME
WRITE (6.1B1)
WRITE (6.166) TT.CUMT .TAA.HLOW.HHI.ROES
WRITE (6,|7?t
WRITE (6«|f6l HDRV.HWFT,WATL»WATH.CB s Ci,
KCH = 1
HROOT=G(2) 4 15
9UNOF=U.n A } S IF (HT-GI ) 20 .3?. ?0
?0 B(I):(DIFFA-niFFB) /(Hl-BI) • I7'"1
IF (1-1 ) 21 .? 1. 33 * 1 ?1
71 IF (EOR-(l.U) 72.33.??
r> ERT(R(l)«(H(l)«TT-H(?)*TT-G(?)»T»'»G(l)«TM»DD(?)))/nn(?)
IF ( AOS( 1.1»EOR-ER )-ARS (P. 1»EOR) I 236.236.23
?3 iFtKCK.ro.n no TO ??n
IF (KCK-20)305.23fe.236
•>»f> H(Hr(l.l«EOP»nO(2)/P(l)»H(?)«TT-r, Ul»TH»Gt2)-TM-OD(?))/TT
IF (Htn.LT.HHRY) H(l)rHORY
IF (H<1I .GT.HWET) H(1)=HWET
GO TO 33
??l. HtllrHKP
W(l)rWKP
KCK=KCK+1
GO TO 19
30"= KCK = KCK»!
IF (ER-EOR) 2H.33.26
2.inf*3>sn
30 H( DrtPt J*l )-P(J )l «RR*P( J» » 1 3»
71 8 TWW=(WI 1 )*Y( 1 I )»Q. 5
217
-------
3?
33
J=(TUU-T(1M/OELV*1.0
RR: ( TWW-TI J) J/QELW
OIFFAr(0-D(J»)«RR»DU)
HIr(P(J»l)-PtJ))*BR+P«J>
GO TO 219
P(I)= + Y
3T CONTINUE
KCK = 1
IF CFOR.GT.O.n. AND. ET.GE.O-UI GO TO
IF JEDP.GT.O.O. AND. ET.LT.0.0) GO TO
Stf. ft ETPLrf.T-fOR
IF (ET.GE.0.0) GO TO 3<<
IF CF.TPL-0.0» 365.39.39
5SS 5 TTPL=ET
C**« ****»•*****»*»*•*•*********•**•*»»»«'
A 1 10
A 1 11
A I 1?
1 <•?
1 U>4
I US
1 IK
A 1 «i
a 1 si
5555
,»*•****»**«»«»
SEAPCHING FOR
HHOLO=HROOT
HROOTrHLOW
SINKrO.O
00 7^0 Ir2.K
THE PROPER HROOT VALUE
•» ?n
111
HI?
H 7>
090
491
40S
400
401
7SII
00 «*?0 1=2. K
IF (HROnT-F (I).GT.O.Cl) 60 TO H 20
SINK=B«I )*PDF« I)*OT-EtIM»SINK
CONTINUE
IF (-5INK-ETPL .RT.O. 0) BO TO «D 2
HROOT=HHOtn
HROOTzl ,2*HPOOT
DO «»21 1=2. K
IF I H»OnT-E(I ).GT.O.n» GO TO «• 21
SINK=R»I I*POF< H«(HROOT-£(in*SlNK
CONTINUE
IF (SINK-ETPL>««1 It40?» 41 0
HR|.0=HROOT
HPOOTzHHOLO
LCOUNTrO
HRnoTro. R»HROOT
LCOUNT=LCOUNT+1
IF (LfOUNT.FO.1;) GO TO u qn
SINKrO.O
DO H?.? 1=2. K
IF (HPOOT-FCI J.GT.O.D) GO TO «« 22
SINKreHI»*POF« I) *( HROOT- El I) »*SINK
CONTINUE
IF(STNK-F.TPL)Ul?.«»n?. «1 3
HRHIzHROOT
GO TO 4^1
HRHI=HHI
LCOUNT=0
HROOT=HHOLO
SINK=0.0
DO 400 I=2.K
IF (HPOOT-EtD.GT.0.0) GO TO 400
SINK =8 (I )*ROF( IJ*(HROOT-E«I»)*SINK
CONTINUE
LCOUNT=LCOUNT»1
IF403. 402.404
B«
BP
R B
218
-------
HO r HRlOrHROOT pp
HROOTZ0.5*r\ 1=2 .KK
300 IF (HI II-HWET-DOtI 1 I R0.60»5!>
55 H(II=MWET*OD(I )
60 CONTINUE » 1 M7
C» •»••••••••••••«•«••»•••*»•«••••••»•»•»••••»••••••*»•••»••»***»•»»••*••»
C COMPUTATION OF WATER CONTENT^ AS A FUNCTION OF PRESSURES JUST COUP A 199
IFIHI1I.GE.HWET.OR.HI 1I.LF.HORYI GO TO 1005
WFOO=f OR
H(ll=tEOR*00(?)/Bll)+Ht?l»TT-Gll)«TH»6t2l*TH-OOC?»l/TT
GO TO 134
10M5 WFDDr'U II* (IH( 1 I -H ( 211 *TT »IGI 1I-GC2 I I«TM + ODI?I 1/001 ?) R 1 B9
114 1=1
6? IF IHIII-Gltll 65.11P»K5
65
NLO = 1
J=?5
66 IF (H(II-P(J)I 67.72,^8
67 NHI=J
GO TO 69
68 NLOrJ
69 JT=J
?U6
2U7
? 0«
2 09
2 10
2 a
? 12
2 13
219
-------
J=(NHT-NLO)/7»NLO
IF »J-JT> 66.70t66
7U IF CHCI)-PCJH 7l.7?f72
71 J=J-1
72 WAT= (H 1 1 1-PC JM*nELW/C P( J*l ) -P CJ>) «T (J)
2 1U
2 I*
? if
i 17
? Ifi
W( I) = UAT
GO TO 117
lit WCI)=VCT) A 31.0
11 7 DO 7fl« IZ2.KK
?6fl W< I ) rf (I I « (H )»Y < I)
GO TO 2f><*
SUM 7 = 0. (I A * 2F.
330
3 3?
no m i = 2.K
SUM1=UCI»»SUM1
IF ( »RS«SUH1-SUM2» -ftfl^lStlMI) ) 1^1. 131.1 TO
Hi' SUH1;<;uMl-SU^?
131 CONTIMUF
IF ( APS SEC?)=CSSC2l«YC2l-S<;i 7I«UFRO)/UC7)
GO TO 200
7r>n IFCUFRO.LT.O.O)GO TO 707
GO TO 206
702 IF C UFPO.GT.O. 0)00 TO 70S
GO TO 200
•»:«) SECT.»l) = *UFQU-SSCI»1 )«UFRO)/UI I*D
220
-------
?t'0 IFCSFJI+1 ).LT.U.O) SF( 1*1 )=SSII*1 I
<»QO CONTINUE
DO 704 Irl.KK
704 SD< I) = Sem»WU) a J4C
70S IF(FOR-U.O) 13*. 136. 13S
13^ RUNOFF (EOQ-UFDn) «OEIT« RUNOF A 3 45
iJC, TIMErTIMF»OEl T a ? 46
IF U.L-MMI 13*. 137. 137 A J 47
1'7 CALL PLOT ) TIME.CUF.EOR. WFnD.HROOT .CUHSi Clt«<0 tSIIM A. WF ROD. WFlltl .SE
1 (K )
IF JSUMJ-iJ.O) 131. 301. MS
*U DELTr?.0»OFLT
GO TO IMS
U'' TU = ABSICONO«nELT/SUH^) « 3 S7
11M IF (TW-0.1«OFTT) l«lt 142t »? A T 59
I'll TW=0.1*OFTT
GO TO 1 44
112 IF(TW-1000.n»PETT) ] U«j ,l«tl««3
lU-« TU=inOl).0*DETT
1"M IF(TW.GT.2.0»DELT) GO TO V) 1
DELTrTy
C*«* •*•*•••*»••*•*>****•*••*•*»*•*»••**••**•••>***»* ••••»•*•• *• »• •«•«*•»»
C ----- TEST TO SEE IF EtfAP OR RtlN INTENSITY «EOR» H»S CHANGED » 3^
14^ IF « TIMf-V(KC« )) » 148 tl »7 .1 1ft
147 CALL PLOT « KK >W A TH , V, DO tSH A X. SD »
WRITE (6.166) (H(I ) .ITJ ,KK ) A 371
WR ITE (fill KB) (SF( I) .Irl.KK)
WRITE(fi.l66)(A(I).Tr7,KK)
WRITEI6.184)
WRITE (6. 18 6 I TIME.CWF.EOR. wrOD.HPOOT ,CUMS. CUHP.SUMA. WFROD. WFUU .SE
I (K)
DELTrOFTT A T 7S
EOR=V«KC»2I
SE(1)=SF(KC»?)
ET=TET(Kr»2)
KCrKC»2
GO TO 151 4 * ™
IF CTIMF»DELT-VIKC+1) 1151* 151. 119
DELT=V(KC»1)-TIME
151 LI_rLL»l * ' *•
IF iTIME-rilMT) 153. IS?. IS? 4 7 Cc
15? IF I ML -L MM) 1 62 .IfiZ .1 A J V
IS7 r(l):
GO TO 16 » *&
16? STOP ' Mllfi
221
-------
c • ••
17ft
17?
1811
181
>••• ••••••*•*••••••••»»••
••••••••••••••»••••••••••••«•••«
FORMAT J?QT3»
FORMAT (7rio.*n
FORMAT (1 IF 11.14)
FORMAT (1HH K MM IFP NfU
FORMAT tnw WATER POTTNTIAI CONDUCTIVITY OIFFUSIVITY
1C(U OFPTH W-DEPTH H-OEPTH POF-nfpiH Sf-PrPIH)
FORMAT (SJH HORY HWFT WATL
FOPMAT (SUM TIME FNfl SOIL FLUX FT FLUX
FORMAT (6KH OELX DETT GRAVY
1 TIME I
FORMAT (66H TT CUMT TAA
1 KRESI
13H FORMATI1H .« TIME CWF FOR
1 CUMS TUMP TRANS. WFROD
END
t « 11
A 14 M
U AT H
rowo
HLOU
WFOO
WFUU
r in
"f LU
HHI
HROOT
SE(K>
17-
11
in
1?
•t
S
SUBROUTINE PLOT(N.WM«X.WVALUF.XVALUE.TMAX.TVALUfl
DiMfM<;TON ALINFI IOI».WVALUE«?SI ,XVALUF»^S i. T VALUE (?si
DATA FILL.AXIS.CHAR.fHAB.-SAMF/lH .1 H . . IHW . 1 HS . 1 H* /
WRITE (6.71 WH»X.TMAX
00 1 J=l. 101
ALINE (J» TAXIS
WRITE <6.B> (ALINE (K) .K rl .101 »
DO 7 J=l. 10 1
ALINE(J):FILL
00 t L = 1.N
J=inO.()»(WVALUF« L) /WMAX)+ l.S
JjrinO.O«(T VALUE «LI/TMAXI»1.5
IFIJ.LT.ll J-l
IFIJ.GT.ini) JrlUl
IF(JJ.LT.1I JJ= 1
IF (JJ.GT.lnil JJ=101
IF ( J-JJI 10.1 1. 10
ALINE (Ji:«?AMF
GO TO 1?
ALINE IJI=CHAR
AL TNE ( JJI=CHAB
WPITEC6.9) XVALUEI LI . UVALUE«D.TVALOE«L). 'ALINEIKI.Krl. 10 1)
AltNF»J)rFILL
s ALINE (i ITAXI*:
CONTINUE'
oo s j = i. 101
*LTNE(J>rAXT«;
WRITE (fi.fl) (ALINE (K> .K = l .1011
RETURN
FORMAT I20H X VALUE WVALUE SV AL UF .«iX. 17H
1 MAX SALT CONCENTRATION IS«.F6.?.1H )
FORMAT (31X,iniAl)
FORMATdH .Ffi.l .F9.4.F8.P.7H .101*11
END
14U
«»C
H7
MAX W AT CONT IS .F7.«, •
222
-------
FORTRAN Listing Combined Water and Salt Models
C PROGRAM-SOIL UATtP.SALT .fI OH UITH PLANT UPTAK'
C PROGRAM OF SEP. 2S. 1«» 71
c HWET is PRESSURE OF HIGHFST POSSIBLE WATER CONTENT
C V IS BOUNDARY CONDITIONS AT TOP »ND TIMES CONDITIONS APPLT
C DETT IS TIME INCREMENT TO START UITH AND LOUEST TO USE
C CONO IS SMALLEST UATfRCONTfNT CHANGF ALLOWED EACH COMPUTATION
C GRAVY IS GRAVITY COMPONENT USUALLY THE SAME AS OELX
C OELW IS WATER CONTENT DIFFERENCE CORRfSPONO ING TO TABLE INCREMENTS
C T IS HATFR CONTENT TAflLE HAS EQUAL SPACED INCREMENTS
C TIME IS CUMULATIVE Tl>-£ AT START OF COMPUTATION
C TT IS 1.0 FOR LAASONfN AND 0.5 FOR CRANK NICHOLSON
C CUMT IS TIME AT END OF COMPUTATION
c TAAzit FOR ?ERO FLUX AT BOTTOM.TAA^O FOR HIK«O CONSTANT A
C FROM GCI I OR HI I I=G( I)
C CTM IS LOWEST VALUE OF DELT PERM ITTED-- IF AS LOW STOPS
C HORY IS PRESSURE OF LOWEST POSSIBLE WATER CONTINT
C PP IS PRESSURE TABLE I WCTT INGISTARTING WITH LOWEST PRESSURE
C 0 IS CONDUCTIVITY TABLE STARTING WITH LOWEST WATER CONTENT VALUE
C 00 SAME AS ABOVE EXCEPT STARTS FROM WETTING
C C IS WATER CAPACITY AS A FUNCTION OF DEPTH BEGINNING AT TOP
C DELX IS DEPTH INCREMENT
C W IS WATER CONTENT AS A FUNCTION OF DEPTH BEGINNING AT TOP
C H IS WATER PRESSURE AS A FUNCTION OF DEPTH BEGINNING AT TOP
C WATL IS LOWEST POSSIBLE WATER CONTENT
C WATH IS HIGHFST POSSIBLE WATER CONTENT
C CB IS A CONSTANT TO MULTIPLY 0 ARRAY RY--USUALLY 1.0
C K IS NO. OF DELX INCREMENTS.MM NO. OF TIMES H»W PRINTED.KIT NO.OF A 1?
C STAPT HERE FOR A NEW PROGRAM A 13
C MI IS TO PRINT H.W ARRAYS EACH ITER..IER NO. OF V ELEMENTS A Ik
C HROOT IS THE ACTUAL ROOT WATER POTENTIAL
C BB REPRESENTS PLANT UPTAKE ADDITIONS
C HLOW IS THE MINIMUM ROOT POTENTIAL ALLOWED
C HHI IS THE MAX1MIM ROOT POTENTIAL ALLOWED
C ET IS THE POTENTIAL E VAPOTR ANSPIR AT ION . AL W* YS NEGATIVE
C WFDO IS THE WATER FLOW RATE AT THE SURFACE
C ETPL IS THE POTENTIAL TRANSPIRATION.ALWAYS NEGATIVE
C SUMS—SALT CONCENTRATION GOING OUT
C TET IS THE BOUNDARY POTENTIAL ET.ALWAYS NEC AT IVE.LI V ARRAY
C DD.H.G.Y.U.ROF, A.SE.SS.SO ARRAYS ARE OF SAME DIMENSION AT LEAST =KK
C P.D.T.ARE OF EQUAL DIMENSIONS.»»E EQUAL TO 60 AT MOST
C SF.TET.V ARRAYS ARE OF SAME DIMENSION AT LEAST rl ER
C CS=C»LCIUM.MS=MAGNESHIM,SN=SOOIUM.CLrCHLORIDE•SU=SULPH»TE.HC-8ICARBON ATE
C CE.ME.EN.ARE EXCHANGBLE CALCIUM.MAGNESlUM,SODIUM
C CAL.CAS.ARE TALCITE.
C CAl.CAS.ARE CALCITE AND G YPSUM. CSO.MGSO. ARE ION PAIRS
c csG.Mso.SNO.cuotHCO.suo.csx.MGsx.ARF OLD CONCENTRATIOS
C AM.*C.SAM.SAC.ARE TABLES OF IONIC-STRENGTH ACTIVITY COEFFICIENT OF
C CALCIUM AND SODIUM IONS
C TCA.TM6.ARE TOTALCONCERAT IONS1CATIONS*ION-PAIR SI
DIMENSION CFI 35) .MFC 3 51 .SNF i 3 51 .SUF t3S) .CSOF I 35) . MGSF <3 5) .CLF(TS)
DIMENSION HCFI3S)
DIMENSION D0< 251 .HI 2SI . Gl 25) . VI 251 . U«25).ROFC 25) » AC 251 . SE 12 51
DIMENSION SSI25).SDI25).C(25>.B(2S).E<25).F(2S)
DIMENSION SFIB5).TETI6S).VI65)
DIMENSION Pt50> .0(50) .T J60)
DIMENSION CS<27).MS(27>.SN<27).SU(27).CLC27).HCI27> .CE< 26>»KF <2fi)
DIMENSION ENt 26 ) .CAS • 77 ) . CSOC 27 > .MGSX (2 7) .T MG 12 71
DIMENSION CSGI27) .MSOI2 7) .SNOI27) .CLOI2 7) .HCO(?7> •SUO(?7> .CSX 12 7)
DIMENSION AMI ?7» .AC! 77) .SAMI2 R) .«, AC 12 fi»
DIMENSION TCAI26I
DIMENSION CAl1271.MGSOI?7I
REAL MF .MGSF
REAL MGSO .MGSX.MSP
REAL MSO
223
-------
REAL MS.HE.MF A, MSA
WRITEI6.8765)
> 5 FORMATI1H1. 25 X« •••••••»»•»•»«*•»«*«»«••••••*«•••»»»•••«**•*•««»•«»
WRI TF. (6.8766)
87T,f> FORH«T(1H .SMX.'CROP *L F AL F A . .BOO T DEPTH IS I?) FEET.M
WRI TE (8 .S999)
9 I TCTII) tT-1 .IFRI
REAO(S.l(.5t ( "OF ( I ) .1 -1 .KK »
KCrl
ET=TET( 1»
LU=MH A 19
REAOCS. 16 S) (P( I ) .Ii 1. NO)
REAOIS. If 5) (0( I ) . 1= l.NO)
READ 165. (mil .1=1 .KKI A 25
READ 165. (VII) tl = l .IER» A 2F-
READ 16S. OELX.OETT .CRAW. CONO.DELU .TIME
READ 165. TT.CUMT ,T AA.HLOW.HHI.RRES
REAO 165. HORf.HUET .U ATL. UATH.C8
I BOUNORY CONDITIONS FOR SALT FLOW
READ 165. CSF.I = ! . IER)
READC5. 165)(SNF(II. 1=1. IER)
RE A D ( 5 . 16 5 ) ( S UF ( 1 1 . I = 1. If R I
READ* 5. 165) (CLF ( I) . Ir 1. It R )
READI5. 165) (HCF I II . 1= 1. ICR)
RE AD I 5. 165) .1=1 .IER)
RCAOCS.16SUMGSFII) .1=1 .IER I
WRITEI6.166) ICF(I). Irl. IER)
UR I TE < 6 . 1 66 ) t MF < 1 1 . I - 1. IE R >
WRITE (6.1 66) (SNF (I) ,1=1 .IER)
WRITE (6. 166) (SUF(I) .1=1 .IER)
WRITE (6. 166 » (CLF II I .1=1. IER I
WRITE(6.166MHCF(I> .1=1 .IER)
WRITE (6. 166) JCSOF< II » I- 1. IER»
WRITE(6.166) (MGSF(I). 1= 1. IER)
REAOIS. 165)AM
REAO(S. 165)AC
REAO(S. 16SISAM
REAOIS. 165)SAC
WRITE (6*1 66) I AH (I I. BC( I). 1=1. 271
WRITr(6.166)(SAK(I»,«;AC(I).I=1.26l
TNfI»L CONDITIONS FOP SALT FLOW
REAO(S. 165)(CS(I).1 =
REAOIS. 165)(MSI I ) .1 =
REAOIS.165)(SN(11.1=
REAOIS. 165)(SU(I)«T =
READIS.165)(CLII).I=
.KK )
• KK)
.KK)
.KK )
.KK)
REAOIS. 165) 1C AH II • 1= 1. KK I
RE A 0 I S . 16 5) I C AS I 11 . I~ 1. KX )
WRITE 16.166) ICSII). 1=1. KKI
WRI TE I 6 . 1 66 I I MS ( I ) . I- 1. KK )
WRITE I 6.166) ISNI I) . I- 1. KK )
WRITE I 6.1Kb) (SU( I) . I" 1. KK)
WRITF<6.1661(CL(11•1 = I.KK)
WRITE 16*166)IHC(I).1= 1.KKI
WRITF 16 .166 I (CAL ID .1=1 .KK I
224
-------
URITC(6.168I(C»S(II.I-1 ,KK
WRITE (6.169)
WRITE «Etl63> K .MM. IfR. NR ,
SMA XrUATH»«00.
Ptll:P = CEA
ME« II=MEA
EN( II-ENA
CSO(I»=CSP
6 CT
WRITf (6.
GCSO(II«HGSO(It
CONTINUE
,CL
).Ct( U
CL(2)=2S90.9Bft8
875 WRlTE(6t911»
00 910 1=1. KK
910 WRITEI6>1K6MCS( 1 1 t HS< 1 1 >SN < I ) i SUI 1 1 tCL ( 1 1 1 HC( I) t CF ( I > t HE 1 1 1 1 EN (I )
l.CAS(I) tCSO(D)
W9ITE(6.166»HGSO
C-
CSCll=CF< II
NSI 1»-MF ( 1)
SNI 1)-SNF( 1 I
SU( 1)=SUF(1 I
CLCll^CLFCll
HCI 1 )-HCF(l I
CSO(1»=CSOF(1
CUFLX=0.0
COR-V(1»
DELTrOETT
TM=1.0-TT
TBB=1.0-TAA
VNA XrWATH
00 It 1=1 tKK
A Tf>
A 77
A 82
i «
som=sEii>*wm
r < 1 1 =w 1 1 1
PIT=O.O
DO 15 I=2»K
WRITE 16.1701
Tu=om
DI1»=«D«1I«(PC2>-P« 111 )«CB
J=«U»11-T(1)»/OELW» 1.0
87
89
39
225
-------
«(W(1I-T(JI)/DFLW»PIJ)
G ( 1 I =H I 1)
C tI)=OE LW/IPCJ»1>-PIJ) )
WRITE: i 6.166) T< 11 .PI i I.TU.D.c< D.OOI it .u< i> .HI 11 .RDFII I..SFU >
DO 1 1=2.KK
TWrOIT)
0(1 » rOt I>» IPI I I-P< 1-1 I I »CB+Dt I- II » «»1
J=(Hill-Till)/DCLU«1.0
H(I)=fP(J»l)-P(j))*(u(II-TCJI)/DFLU»P(J)
C( I >=DELW/ (PtJ»l)-PIJM
GIT 1 iH( I) * 86
WRITE ( 6.166) I ( I ) ,P( IJ .TW.Dt I) tCCI >.DD< I ) .W( U .HI II .ROFII I.SFII I
CONTINUE
DO 2 I-N.NO
TWrDII)
C
2 WRITE (6.166) T < 11 . PI I) .T W. DC I)
C D IS NOW DIFFUSIVITY TIMES DELW NOT CONDUCTIVITY
WRI TE 16. 179)
DO S Ir2.IER.2
WRITE
WRITE
WRITE
WRITE
WRITE
WRITE
WRITE
6.166) V(I).V(I-1).TET(I-1).SFII-1>
6. 180)
6. 166) DELX.DETT.GRAVY.CONO.DELW .TIHE
6. 1A1)
6.166) TT.CUMT.TAA.HLOW.HHl.RP.ES
6. 172)
6.166) HDRY.HWET .WATL. WATH.CB
KCK = 1 * 93
HROOT=GI2I
RUNOFzQ.O A 95
CUMS=0.0 * *
CUMBrO.O * *7
CUMHrO.O * *
CALL PLOT IKK .WATH,W.OO.SHAX.SO)
WRITEI6.166I TIME
C COMPUTATION OF CONDUCTIVITY IB) AND WATER CAPACITY (C I A 99
16 TOP-WATH Aim
BOT = WATL A 1 01
HKP=H(1)
WKP=W<1)
IF (COR-0.0) 17.19.18 A 102
17 WIMZWATL A 103
Hit)=HORY A 1Ott
GO TO 19 A 1 05
18 Will rWATH * 1 G6
HI 1 ) rHWCT A 1 Q7
19 TWU= I Wl 1) »YI 1 I ) »0.5 A 1 OB
J=(TWW-TI1))/DFLW»1.0
BB = ITWW-T IJI ) /DELW A 1 ID
DIFFAr IDIJ* l)-n(J) )«BR»D(J) A ill
HI=(P(J»1)-PIJ)>»BB»PIJI A 1 12
DO 37 1 = 1 *K A 1 13
J=ITH -T(1))/DCLW»l.0
BB = ITW-T(J) I/DELW A 1 IE
DIFFfl^IOIJ*1)-DIJ))«BP»0(J) A 117
GlrCP(J»ll-PIJI)«BB»P«J)
?\ 9 IFJHI-6II20.32. 2O
20 811lr«DIFFA-DIFFBI/«MI-GI) A 1ZD
IF JI-1) 21 .2 1. 33 A 1 a
21 IF (EOR-O.OI 22.33.2?
27 ER = (BlU»(Hlll«TT-H(2I*TT-6
-------
IFIHIll .LT.HDRY > HIU-HORY
IF (HI1I.GT.HWCT) HUlrHWET
GO TO 33
2211 HUJ-WKP
KCKzKCK*!
GO TO 19
305 KCK=KCK*1
IF (ER-EORI ?4. 33.26
24 IF (U(l)-WATH) 25.33.33 A 1 2*
25 BOTrWt 1 » A 1 27
U(1)-(U(1)*TOP)»0.5 A 128
GO TO 28 A 1 29
26 IF 33.33.27 A 1 30
27 TOP-kMl) A 1 31
W(l I-«W(1 )«80T) »0.5 * 132
78 J=( U< ll-TCU >/OELW+1. 0
BBrtWd I-T IJM/DELU * 134
IFIEOR-O.OI 30.3 3.30
30 HlllrlPI J»l 1-P(JM •flfUPlJ) » 158
21 8 TWU-«U< 1)*Y(1))*O.S
J-«TWW-T( 1)»/OELM»1.0
BB:«T«U-T t JU/DELW A 1 U3
OIFFA = <0( J+U-OJ J» )»BB + D(J» A 1 11
HI=IPCJ»lI-P(J)I«BB»PIJI • 112
GO TO 219
32 BID rtD< J*l »-OC J>! /JP( J«H -PCJ »> » 1 «2
IF « T-l I 33 .2 1. 33 A 1 43
33 TuyrTu a 1 44
HI=GI A 1 45
OIFFAzOIFFB A 1 46
TW=(U (I »1 ) « Y( I* 1) I »n.5 A 147
j:(TW -T( 1))/OELU*! .0
35 C < I»l) =OELU/ (P« J*1)-P( J» ) A 151
37 CONTINUE A 1 54
KCtCl
IF (EOR.GT.0.0. AND. ET.GE.O.Ot GO TO 6^66
IFIEOR.GT.0.0.AND.ET.LT.0.01 GO TO 5555
6«*6 ETPL=ET-EOR
IF(ET.GE.O.O) GO TO 19
IFCETPL-O.OI 365.39.3*
365 HHOLP=HROOT
HROOTzHLOW BB
SINKrO.O
00 250 Ir2.K
7SO EIIl=G«tl-0.5715«SEI I) -00«I»»RRES
DO «20 Ir2.K
IF«HROOT-E(I) .GT.0.0) GO TO 420
SINK=BCII»ROFIII»«HROOT-E(III»SINK
HPT) CONTINUE
IF(SINK-ETPL.GT.O.O> GO TO 402
HROOTrHHOLO
Min HROOT=1.2»HROOT
SINKCO.O
DO 4?1 Ir2.K
IF IHROOT-EII ) .GT.0.0) GO TO 421
SINK =81 II»RDF J1)»«^ROOT-EIIH»SINK
4?l CONTINUE
IF(SINK-£TPL> 41 1.40?« 41 0
111 HRLOrHROOT
HROOTrHHOLD
LCOUNT=0
41? HROOT=0.8»HROOT
LCOUNTrLCOUNT*!
IFILCOUNT.EO.S) GO TO 490
SINKrO.O
00 4?2 1=2. K
IFIHROOT-EII ).GT.O.O» GO TO 422
SINKrBU»»ROF « 1 1 »l HROOT-E t H ) »SINK
227
-------
47? CONTINUE
IFISlNK-ETPI.> GO TO 407
4(1) iB(I).IHROOT-E( I»»2.0»RDFII »/ ( DOt I »1 I - DO 1 I- 1 ):)
GO TO 406
407 AdtrQ.O
HOf. CONTINUE
C ----------------------------------------------------------
C --- COMPUTATION OF TRIOIAGONAL MATRIX MAIN BODY A 158
38 DO 42 1 = 2. K B 159
POTrCOD (1*1 I-DDI 1-1 M/» 2. 0»OELT » B 160
= IDD » « BC I- 1) /OLX A B 1622
l)«(TM««GCI-l»-G(II)»OLXA»»A«I>»«nnJI«l)-DO«I-lM»0. 5>/TT
IF(I-2I 390. 39 Ot 40
190 IF(H(1).GE.HWFT.OR.H( ll.LE.HDRV I 00 TO 394
OA=DA-I (BJI-1 )/OLXA»»CTH«JG«I-l I -Gil I) »DL XA ) )/TT«EOR/TT
BR=BR-B (1-1 I/OLXA
GO TO 393
V?4 OA=OA»H(I-1 )»B«I-1»/OLXA
193 F(l
GO TO 4 2 A
40 If
41 E(I
=OA/BB
= (B (I t/OLXBI/RR
I-KI 41 tl 1.43 *
z(B(n/OLXB»/(BR-(B(I-ll/DLXA)»E«I-l)l ft
= (DA* (8(1-1 )/OLXA)*F»FCI-1»)/ B
44 1=1-1 *
661
6,7
R9
70
7?
73
7«
741
7B
77
IF 47. 46*46
46 H«KK»=H(KI«00(KK»-00«K > B 1 78
47 DO 60 1=2. KK
300 IF (H(II-HUET-OOII)I fiO .6 0. 55
SS H(II=HWET»00(I> ,,
60 CONTINUE ' • 1 f7
228
-------
134
62
65
66
67
68
69
70
71
72
1 If.
11 7
26ft
269
COMPUTATION OF WATER CONTENTS AS A FUNCTION OF PRESSURES JUST COUP
IFIHf ll.GE.HUET.OR.HI U.LE.HDRTI 60 TO 1006
WFOOrEOR
Htl) =IEOR*DO( 21/8(1 ) «H( 2>*TT-Gf 1 ) »TH *G ( 21 »T M-OD( 2 > >/TT
GO TO 1 3D
UFDD=B( 1)» ((HI 1)-H( ?I)«TT»(GI 1>-G(? ) I*TM«00(2> "DO! 2)
1=1
IF (H(I>-G(I)I 65.116.65
NHI = 5«l
NLO = 1
J=2S
IF (H(I)-PCJI) 67.72. R8
NHI = J
GO TO 69
A 199
JT=J
J=f NHI-NIO)/?»NLO
IF IJ- JT) 6f>. 7Q .66
IF IHIII-PIJM 71.72.72
J=J-1
UAT= (H(I I-PC J) )>DELU/ 63 tl 32
IFIOELT-OETT.O. D63.& 3. 133
OELTrO.S«OELT
GO TO 38
SUM 1=0.0
SUM 2=0.0
00 ROD I=2«K
SUMlrWd >• (DD( I»1)-ODI 1-1) )/2.«SUMl
SUM7=yjH»(DOCI*l»-00«I-lll/2.»SU»12
CUF=SUM1-PIT
UFROD=(SUM1-SUM2)/OELT
UFUU=B(N6I*( (HCNBIHINB»l))»TT*IGINBI-GtNB*l)l»TM»00«NB»l>-00«NR)>
1/«DD«NB»1I-DO(NB)I
CUMS=WFOD«OELT«CUMS
CUMB=MFUU»OELT»CUMB
SUMA=SUMA»SINK«DELT
CHFLX=ISUM1-SUM2»
KB=K-1
-------------------------------------------------------
00
MSO(I»=MS(I)
SNO(II=SN(H
CLO(I)=CL(II
HCO(II=HC(D
SUO(I)=SU(I>
CSX(II=CSO(I)
MCSX(II=MCSO(T>
CONTINUE
STIMrSTIM»OELT
KB=K-l
MASS FLOW OF DIFFERENT IONIC SPECIES
DO 920 1=1. KB
DEL X=
2 06
207
10
11
12
13
W
15
2 17
» 5 UD
A 3 26
327
3 2P
329
3 3D
331
332
A 33 6
A 3 *»1
A 31 3A
229
-------
1/IDOIIMI-DOIIM
UFROr«B(I»l»« < -H«I»?) >»1T««G< 1*1 >-GC t»?)l • TM»On« I«
JI)*DCLT I /(DO(I« 21-001 I* 1» )
7S4 IFI AflS(UFRU) .UT. 0.000 1. ANO. ARS
CL3 = CLOU»2»
CL4=W( I »1 I
CLS=V«I»1 I
CALL SALT (CL 1. CL2* CL 3. CL . MFRU .WFR D. OELX . I .f OR )
CSI I«1)=CL6
CL1-MSOCI I
CL2-MSO
CL2=HGSX«I»ll
CL3-MGSX« r*2)
CALL SALT ICL l.CL2t CL ^.CL«».CL S.CLK.yFRU,UFRD.O£LX .1 .FOR >
MGSO(I«1)=CLR
SEC I»1)=CSCI«1I»MS«I*U»SNII« U»CSO«HGSO(I*1 I;
TCA«I+1 )=CS(I»1)»CSO(I* 1)
TMG(I»l)rMS(I*ll »MGSO( 1*1 )
LS=I*1
IFISTIM.LT.l.OIGO TO <*2 0
47S UArU(I«l)
CSA=CS(I*1)
MS«=MS«I»1)
SNArSNII*!)
SUA=SU
CLArCL«I»l)
HCA=HC(I+ 1>
CEArCE(I*l»
MEA=ME(I«1)
CSP=CSO(I»1 »
HSP=MGSOII*1>
CAP=CAL(I»1I
CASA=CAS(I»1>
SEA=SE(I»1»
CALL EXCHICSAtMSA.SNA.SUA.CLA.HCA.CEA.MEA.ENA.CSP.MSP.CASA. CAP.UA .
KSEA .AM. AC.SAH.SACI
CS(I*1»=CSA
MS(I«1I=MSA
230
-------
SN( I«1I=SNA
CL(I»1I-CLA
HC( 1*1 »:HCA
CE( I»1I=CEA
ME(I»lt-MEA
EN( 1*1) -ENA
CSO(I»1 )=CSP
MGSOCI* 1I=MSP
CAL (1*1 I -CAP
CAS(I*1 irCASA
SE(I»ll=SEA
IFICSII*!
IFIMSII*!
IFISNII*!
IFICASII*
.LT.O.UICSI I« 1>-0.0
.LT.O.UtMSii« llro.0
.LT.O.OISNII* 1)=0.0
.LT.O.OISUII* I)=0.0
>.L T.O.OICASIi*i> =0.0
TF ICSOt I* l).LT.O.O)CSOtI*l>=D.O
TC« 11*1 I=CS(I «ll *CSO« I« II
THG (1*1 I=HS(I *1)«HGSO(I»1)
97D CONTINUE
IFJSTIM.GE.l.OSTIHrn.O
c -------------------------------------------------------------
00 704 1=1. KK
70U S0( I) = SE(I)*V( I » B 3<«%
7DF, IF (FOR-O.D) I3fi. 136. 135
13S RUNOF3 ( EOP-ur DD) »OFL T*RUNOF A 34%
13K TIHE=TIME»OELr A 3 «6
IF CLL-MMI I3R.137. 117 A 3 »7
117 CALL PLOT (KK .MATH. W. DO «S HA X. SO »
WRITE (6.166) (HID tlzl .KK ) A 344
WffITE(6tlR6l (SCI It. Irl.KK)
URITEC6.166) (All 1.1=7. K»
WRITE (6.1 111 (CSI I). MS I IJ.SNU l.SUC I) ,ri_< I). KCIII . CE ( I» . ME (I ). EN I I I
J.CASII) .SE(I) .1-1. LS)
WRITE (6.2 001 )
2001 FORMAT (1H . ?X . *C ASO • . *X . *MGSO • . « .• CAL • .7X. • TC A' . 7X .' TMG* I
URITEI6.2000I (CSOI I».MCSO( D.CAL III .TCA(I). TMG (It .1=1 .LSt
LL =0 A3 52
WRITE (fit 1841
Hfl WRITE (6.1111 TIME. CWF. EOR, HROOT. RUNOF . CUHS .CUHB. SUM* .WFROO .W FUU. S
IF tSUNS-0.0) 139. 301 • 1 39
mi OELTr?.0«OELT
GO TO 145
13S TW=ABSICONO»OfLT/SUMU A 3 57
14H IF (TW-0. 1«OE TT I 14 1. 14 2. 14 2 A 359
141 TU = 0.t*OETT
GO TO 144
14? 1FITU-1000.OOETTI1 44.1 44.143
143 TH=1000.0»DETT
144 IF ( TW.GT . 2.0»DEL T) 00 TO 301
OELTrTW
C --- TEST TO SEE IF EVAP OR RAIN INTFHSITY IEOR) HAS CHANGED » 3 P-e
14f, IFIT1HE-VIKC* 1) I 148 .147 .148
147 CALL PLOT I KK .W ATH. U. 00 ,SM A X. SO )
WRITE 16.166) IHII ) .1 rl .KK ) * 3 71
WRITE 16.1 661
-------
MS! 1
CSt I
SNI 1
CLI 1
SUI 1
CSOl
MGSO
HCI 1
KC=KC»2
rMFlKC*? I
= CF IKC*? >
= SNF IKC« 2»
= CLFIKC«?I
= SUFIKC* ?)
I :CSOF !KC* 21
I I=MGSFIKC«2»
IF ITIME.LT.374.Q.OR.TIHE.GE.1 T9. »
SN(?»:SN«2»»«630.55SS/W(2H
GO TO 1 SI
143
14 •*
1S1
IS?
1ST
1SS
ISfi
157
is*
1ST
160
161
16?
161
16T,
n
]<;
i?n
17?
18fl
181
184
911
GO TO 151
IFITIME*DELT-
DELTrVIKC*! >-
LL=LL»l
IF ITIME-CUMT
IF (ML-LMMI 1
Yll 1 riim 1 »YC
J=IY!1»-TI1M
BB = I Yd I -T(JI
IF (EOR-O.OI
VIKC*1 1 1 15 1. 151. 149
TIME
> 15 3. 15 ?. 15 ?
62 . 1 62 . 1
II 1 «0.5
/OELW»1.0
I/DELU
155.156. 15 S
GJll=«PlJ+ll-PCJII«BB»PtJl
00 1M I = 2»KK
J=tWIT)-Tlll}
RB = «W« U-T(J)
G< 1 > :(P ( J*l 1 -
TU=
-------
SUBROUTINE PLOTCN.WHAX.WVALUE .X VALUE.TM AX ,T V M-UE)
DIMENSION AL1NEI10D.UVALUEI2 5) .XVALUFJ2S). TV »LUE I? S>
DATA FILL.AXIS.CHAR .CHAR.SAME/IN .1 H .. I HW . 1 HS • 1 H* /
WRITE (6.7) WMAX.TMAX
00 1 Jr
ALINEIJ
WRITE 16.8) I ALINE IK > .K=l .101 I P 25
DO 7 J:
ALINE(J
ALINE(1
DO «l L =
. 10 1 B Z?
= AXIS B 23
. 10 1 B ?7
3FILL B 28
= AXIS
t N
J=100.0*IUVALUf(LI/WMAXI* 1.5
JJ=100.0*(TVALUECL)/TMAX>*1.5
IFIJ.LT.ll J: 1
IFIJ.GT.101) J=101
IFIJJ.LT.ll JJr1
IFIJJ.GT.101) JJ-10 1
IF IJ-JJ) 10.1 1. 10
11 ALINE IJI=SAMF
GO TO 12
10 ALINE (J)=CHAR
ALINE IJJ)=CHAR
12 WRITEI6>SI XVALUECD.WVALUEtL J.TVALUEIL). (ALINEIK).K=1. 101)
ALINE(JJ1-FILL
ALINE i
S5 ALIN
« CONTINUE B «42
DO S J = l. 101 B tSAC(?6)
DOUBLE PRECISION 22?
MH=1
1 = PW1»100.0/1.16
B-inonoo.o/Pu i
B1=PW1
A = A/UOOO.O»?.0>
F = F/UOOU. 0*2.0)
G=G/ I 1000.0*2.0 I
S=S/1000.0
H=H/1000.0
HC03rHC03/10UO.
AGSO:AGSO/( 1000.*?.)
CASOrCASO/l 10 HO.* 2. I
DA IS KICA-NAIEXCHANGC COEFFCIEN7
DA=«i.5377
0=0.25»S.O/SFA
U=SO»T ( 2.0* < A*F»G» *0. S» «S»H»HCO 31 )
IF(U**2.LT.0.003IGO TO 100
CALL ACOFIAMt ACtSAMtSACtUtAOItAMOl
ASA=Ani*AMO**?.Q
GO TO 101
ASA=EXPI-7.0?«*U/I 1.0+UJ)
1U1 IFICAL) 1000tE02t603
IK = 1
AAAZOS2.
ZErAAA/I
60 TO 24
233
-------
Ml IK:?
ZE:(-1.68
ZE:EXP 26 .1 A. IS
7f> X-0.0
UrSORTC2.Q« I A»F»GI «n.S« 27 t2 R. 28
71 XZXXT*B
XXT=Q.O
A = t »X
G:6*t
U=SO«?T I 2.0* • A«F*G) »0."i» IS*H*HCO 3) I
IFIU»«2.LT.Q.QO 3IGO TO 106
CALL AC OF ( AH. At .SAH .S»C tU «A01 tAHO)
AA=ADT*>?
GO TO 7
AArEXPI-9.366»U/ ( l.»U» )
7 Bflr- J».9E-3»AA»A»AA»G»
CC=AA»A»G-«».SF- 3»CASO
XXXXrBB»B8-1. 0»* A.CC
IFIXXXX 135. 3S .36
TS Xl=0.0
GO TO 37
v; Xl=l-BB-SQRT«XXXX» )/(?.Q*AA)
17 C»SO=CASO*Xl
A=A-X1
G=6-X1
60 TO OH
1R IFI6)lt 1.6
f. IF { A»l. 1.7
1 IF«C»SO)«»i«.<»U .7
XXT=XXT-X/B
C*SOrCASO»CA«i 1
XXT-XXT-C1S1/8
41 t? = A
ITrl
IFiS)80tl81 .SO
Ml IF«SAT)80.S1S.80
BO IJ = ?
Z=S*T/10.
Zl = ?
GO TO 5
MO 3 Z=CT/10.
zi-z
S U=SORTI 2.0«l«*r»G) »O.S» (S»H»HC03»
234
-------
IFtU*»2.LT.O.OO 3IGO 10 107
CALL ACOFIAM.AC.SAM.S»C.U.ADI.AMO)
EX=ADT/AMO**2
60 TO 108
1H7 EX:EXP« <-2. 3<« 1»U)/I l.Q«U»
10 B AAr-(».0*DA*DA*B*B
BB:1.0»8»CEX«2.0«OA»0«»ET.B»OA»DA»S»
CC = «l.n»EX»-1.0»DA»DA»B»ET««B»ET«2.0»S>-DA»OA«S»S
DO=SAT*EX*«l.a*A*SAT*B>«2.0*DA*DA*ET*S*(2.Q*B*ET«S)
EErSAT«SAT«A*EX-OA»OA»S«S*ET«ET
81 ZZr-t(«(AA»Z»BBI•Z*CC)*Z»DOI«Z»EE >
ZZZ=HJ«I.O»A«»Z»3.0«flRJ»Z*?.0»CC>«Z»DOI
ZZrZZ/ZZZ
IF I ZZ-0.0 » 302 13 03.307
303 IFCZ-0.Of302.515t 302
302 ZZZ=ZZ/Z
Z=Z»ZZ
IFdH.6E.5IGO TO 83
IH=IH»1
IF(OABS(ZZZ)-0.001) «3 .8 3. 81
83 IFI Z.GE .0.0)60 TO 305
IF«SAT.LT.ABS«Z»2.0» »Z:SAT/?.0
31)5 A:A»B»Z
IF( A»S10t 510. SI 2
SS2 SATrSAl-2.» Z
SSI ETrET*?
5SU S=S»2.»B»Z
S10 A = A-R.Z
Zr-Zl
IF JMX.GE.SIGC TO 51 ?
MX:MX«1
60 TO 81
SI t S3S-?.0»B«Z
IF(MX.GE.5)00 TO 51 3
MXrM*.1
IF«SI550.55n.Sl 3
51 3 ETrET-7
IF/(2.0*AA)
Az«»B*Y
F-F-B«r
ETrf T-Y
CT:CT»Y
IFI6) 790t 730. T) 1
791 IF(F»790.790.792
7S2 IF(U*«2.LT.O.n03»GO TO 109
CALL ACOFJAM.AC.SAM.SAC.U.AOI.AHO)
AArAOI**2
GO TO 110
1119 AA=EXPI-9.366«U/ « l.»U) )
11U BBr-I5.9E-3»AA»F»A*.G)
CC=AA*F*G-5.9r-3»AGSO
XXXXrBB»BB-1.0«AA*CC
IF(XXXX)7S3.793 .79*
7<»3 X1=D.O
60 TO 795
79 M X1 = (-RB-SORT(XXXX) )/(2.0«AAJ
AGSO=A6SO*X1
F=F-X1
G=G-X1
235
-------
WO CONTINUE
60 TO 1600.601) .IK
mi AAm.o
BB=«.0*HC03» A
CC=HC03»*2««».0*A*HC03
DOrA»HC03**2-ZE
IF«MC03-At61. 61 .62
f>\ Z=-HC03/«».
GO TO 650
6? Z=-A/2.
fi^U 71=7
KJ ZZr- II « AA«?»BB»*Z»CC l»Z»om
IF ( zz-o.mson .101 .300
^111 IF< 7ZZ-O.UI Tnn.soo. son
300 22-22/222
222-22/2
2-7+22
IF I IT.6E .S)GO TO 64
ITrIT»l
IF « D»BS I 222) -.001)64. 6u .6 3
feu *;*»?
HC03^IC03»2.« Z
IF«HC03»75?.TS2.651
7S2 HC03=HC03-2.*Z
» = *-?
Z = -Z1
GO TO 63
KS 1 IF «»)75?. 752. 75 3
7S3 C*L=C»L-Z
ZX=»»HC03»»2
IF « ZX-7E I 60fi. F.US.60S
fins DEL-4-41
IFdG.Gf .5)00 TO S
IG=IG»1
iFiorL-i.or-5ms.d9.2ti
i.c5t-5 121. sn««»n
SO IFIOCL-l.Of-515 1.51 .?«•
SI OEL = »-*3
S? lF«OEL-1.0C-5»8.8.2«»
R »P = »
1000 CONTINUE
K7 CONTINUE
*-*«lOOO. 0»2.0
F:F»1000.0»?.0
S=S*1000.Q
6zG»1000. 0*2.0
H=H*IOOO.O
HCOJrHC 03*1000.
C ASOzC ASO*1 00 n. 0*2.0
AGSOzAGSO*! O00.«2.0
SE»=A»F»S*CASO+AGSO
RETURN
END
SUBROUTINE EOFXCHI CA. AHG.SOS. CL rSO. HC03 .E 5. C5.SA5 tC»SOt AGSO .SEA .AM
T.AT.SAM.SAC)
DIMENSION AMI 77 >.AC(27).S*Mt26).SACI2BI
CA=CA/<1000.0*2.0)
AMG=*M6/I1000.0*2.0)
SOSrSOS/1000.
SO=SO/(1000.0*2.01
CL=CL/1000.
HCO3rMC03/1000.0
236
-------
EC=0.11E-03
DA IS KCNA-CAI QR 1.0/K(CA-NA» EXCHANGE COEFFCIENT
DArn.31 IS
Dr0.25*«>.0/SF »
CASOrO.O
U3SORT«2.0««C»»*MG«SOI»0. 5» ( SOS»HCO 3«CL » )
IF IU*»?.LT.O.Oa 3)GO TO <4?
CALL ACOF(AM.AC.SiM,SAC.U.ADl.AMO>
ACT?:AOI»»2
GO TO 150
ACT2=fXP(-9. 3fit»U/ ( 1. 0*U> 1
IF (SOI 1000.71 3. 71 7
71 2 AArACT?. ACT?
B8rACT2»(10.8f-3»(ACT?«(AMG»CA-SO»))
CC=?B.91E-6*(ACT2»(AMr,«<».9E-3*IC»»5.0E-3l-(SO«10.aE-3»M
DDr-SO«28.91F-B
WJO Z:SO/?.
««! U Z 1 = Z
(f> 3 Z?-- « C AA»Z*BB >•?» CC ) »Z*DO)
ZZZ=ZZ/Z
Z^Z»ZZ
IF » ARS< ZZZ»- .00 1 )8« 0. «• 0. 86 3
fW U SOTrSO
SO-Z
IF (SOI 710.710 .7 11
71 U SO=SOT
Z = Z1
60 TO ft 63
71 1 CASXrSO»CA»ArT?/l«».9F-3»ACT2«SO>
CXrCA-CASX
AGSX^SO»AMG»ACT2/(5.9F-3«ACT?«SO)
AMXzAMG- AGSX
UU=SO»T (2.0* I CX * AMX »SO » *0 .5* ( SOS*HC03*CL > )
IF ( ABSIUU/U-1 . 1-1. Of -») W .«»0. "41
« 1 U:UU
SO^SPT
GO TO it 2
40 CASO=CASX
AGSOrAGSX
CA=CX
AMG3AHX
n 3 ACTlrSORT(»CT2>
ACTM=SORT (ACT 1)
ACTM=SORT( ACTH)
CArCA»2.
AHG=AMG*2.
C--CA.MG.ARE IN EQUIVALENT/LITER
ES=EC/((ACTM*SOS/(OA*SQRT(ACT1*CA)»«1.+ ID* ACTl»ANG/< ACT1 »C A)
SAS=ACTN«SOS»E5/(SGRT|ACT 1»CA»*OA1
CS=EC-E5-SA5
C5=C5/2.
CA-CA. 1000.0
AH6-AMG*! 000.0
C- — CA.M6.ARE IN Mf /LITER
SOS = SOS •1000.0
CL=CL*1000.U
SOrSO*1000.0«2.0
HC03=HC03*1000.0
CASO =C ASO*1 00 0. 0*7.0
AGSO=*ESO*1000.0*2.0
SEA:CA»AMG»SOS*CASO»AGSO
URTTE(6.10niCA. AMG.SOS. CL .SO. H"C03 .t 5. f 5 .S AS .'AGSO. C»SO.SEA
IOU FOBNAT( 12E10.<4l
1000 RETURN
END
237
-------
SUBROUTINE SALTSE(3>iV( 3)
1=1
SSII)=A
SS«I«1»=B
SSII»?irC
U(I»1)=0
TCI»1»=E
IFIJ.EO.HGO TO 201
IFJUFRU.GE.O.O.AND.WFRO.GE.O.OIGO TO 70S
IM yFRU.LE.O.n.AND.WFPD.LE.0.0)00 TO 70 9
IFIHFRU.GE.O.O.AND.MFRD.LE.O.OIGO TO 70S
IF!UFRU.LE.O.O.AND.WFRD.GE.O.OJGO TO ?10
70S SEII«1)=ISSII«1)»YII«1»»CSSI II«WFRU-SS (I •»! > *WFROI /DEL XI /W II »1 »
GO TO ?00 '
?ni IF (EOP-0.0) 20 3t 20»t TO?
!FIWFRD.GT.O.O)GO TO ?0 6
SE«?I=(SS(?)»¥I2)-«SS<3)«UFRD)/OELX I/HI 2)
GO TO 200
206 SEI ?»-- I SS I 2 ) • WFRD I/DEL X I/UI2)
GO TO 200
?n<» IF IUFRD.LT .0.0)00 TO 707
GO TO 206
702 IFJWFRO.GT.O.niGO TO 205
711 a SEII»l»:lSS(I*ll»TII*ll»ISSII»»MFRU-SS 11 «2I • WFRD » /DEL X I /W II »1 >
GO TO 200 '
209 SE 11*11 = 1 SSCI»] I •YII»1I»(SSU*1 »»UFRU-SSII«2I»WFRDJ/OELX)/U(I»D
GO TO 200
710 SEII*l)=ISS(I»l»»tlI*l)»(SSII»lI«UFRU-SSII*1I«HFROI/DELX)/UII»1»
IFISE«I»1).LT.O.O»SE(I* 1>=SSI 1*11
F=SEII»1I
RETURN
END
SUBROUTINE ACOFI «N. AC.S AH .5 AC .U.ADI .AHOI
DIMENSION AN( 771 tAC(27) .SAMI26I tSACI2fi)
U=U»»?
IF(U.LF.1S.O)60 TO 1
AOI=587.0
GO TO "2
DO 751 I=lt27
IFIU.GT.AHII) IGO TO 7 SI
AG=U-AM
-------
Table 34.
APPENDIX C
DATA AND RESULTS
Rain, irrigation and actual evapotranspiration data for alf-
alfa in 1971. Rain and irrigation data were measured by rain
gauge, evapotranspiration data were measured by the lysimeter,
Date
May 15, 1971
May 16, 1971
May 17, 1971
May 18, 1971
May 19, 1971
May 20, 1971
May 21, 1971
May 22, 1971
May 23, 1971
May 24, 1971
May 25, 1971
May 26, 1971
May 27, 1971
May 28, 1971
May 29, 1971
May 30, 1971
May 31, 1971
June 1, 1971
June 2, 1971
June 3, 1971
June 4, 1971
June 5, 1971
June 6, 1971
June 7, 1971
June 8, 1971
June 9, 1971
June 10, 1971
June 11, 1971
June 12, 1971
June 13, 1971
June 14, 1971
June 15, 1971
„ . T . fc. ET-cm
Rain Irrigation
cm cm _ .
Lysimeter
.84
1.63 .38
.20 .05
.04
.53
.48
.32
1.77 1.01
1.57 .37
.09
.53
.85
.16
2.79 .00
.65
.71
.77
.16
.48
2.99 .32
.08
.08
.53
.53
.48
.53
4.83 .27
.59
1.27
.24
.71
.58
ET-cm
West
Lysimeter
.84
-.25
.09
.15
.42
.42
.42
.42
-.35
-.07
.64
.42
.48
.00
.65
.71
.77
.37
.26
.16
.08
.08
.37
.37
.37
.37
.05
.00
.42
.50
.45
.48
Average
ET-cm
.84
.07
.07
.10
.48
.45
.37
.72
.01
.01
.58
.64
.32
.00
.65
.71
.77
.26
.37
.24
.08
.08
.45
.45
.42
.45
.16
.29
.85
.37
.58
.53
Cumu-
lative
cm
.84
.91
.98
1.08
1.56
2.01
2.38
3.10
3.11
3.12
3.70
4.34
4.66
4.66
5.31
6.02
6.75
7.05
7.42
7.66
7.74
7.82
8.27
8.72
9.14
9.59
9.75
10.04
10.89
11.26
11.84
12.37
239
-------
Table 34. Continued
Date
June 16, 1971
June 17, 1971
June 18, 1971
June 19, 1971
June 20, 1971
June 21, 1971
June 22, 1971
June 23, 1971
June 24, 1971
June 25, 1971
June 26, 1971
June 27, 1971
June 28, 1971
June 29, 1971
June 30, 1971
July 1, 1971
July 2, 1971
July 3, 1971
July 4, 1971
July 5, 1971
July 6, 1971
July 7, 1971
July 8, 1971
July 9, 1971
July 10, 1971
July 11, 1971
July 12, 1971
July 13, 1971
July 14, 1971
July 15, 1971
July 16, 1971
July 17, 1971
July 18, 1971
July 19, 1971
July 20, 1971
July 21, 1971
July 22, 1971
July 23, 1971
July 24, 1971
July 25, 1971
Rain Irrigation
i!*ciS t
cm cm T .
Lysimeter
.58
.53
.64
.90
.90
.03 .90
.54
.54
.47
.27
.13 .00
.26
.42
6.05 .00
.27 .00
.51
.62
.70
.72
.67
.64
.67
.65
.67
6.73 .67
.76
.90
.87
.64
.55
.36
.48
.15
.08 .00
7.24 .00
.10 .00
.00
.53
.47
.46
ET-cm
West
Lysimeter
.64
.42
.58
.85
.60
.73
.54
.54
.47
.47
.00
.37
.62
.00
.00
.51
.62
.70
.72
.67
.64
.67
.65
.67
.67
.76
.98
.93
.74
.55
.84
.68
1.17
.00
.00
.00
.00
.80
.64
.80
Average
ET-cm
.61
.48
.61
.87
.75
.81
.54
.54
.47
.37
.00
.32
.52
.00
.00
.51
.62
.70
.72
.67
.64
.67
.65
.67
.67
.76
.94
.90
.69
.55
.60
.58
.66
.00
.00
.00
.00
.62
.55
.63
Cumu-
lative
cm
12.98
13.46
14.07
14.94
15.69
16.50
17.04
17.58
18.05
18.42
18.42
18.74
19.06
19.06
19.06
19.57
20.19
20.89
21.61
22.28
22.92
23.59
24.24
24.91
25.58
26.34
27.28
28.18
28.87
29.42
30.02
30.60
31.26
31.26
31.26
31.26
31.26
31.88
32.43
33.06
240
-------
Table 34. Continued
^ . Rain
Date
cm
July 26, 1971 .03
July 27, 1971
July 28, 1971
July 29, 1971
July 30, 1971
July 31, 1971
Aug. 1, 1971
Aug. 2, 1971
Aug. 3, 1971
Aug. 4, 1971
Aug. 5, 1971
Aug. 6, 1971
Aug. 7, 1971
Aug. 8, 1971
Aug. 9, 1971
Aug. 10, 1971
Aug. 11, 1971
Aug. 12, 1971
Aug. 13, 1971
Aug. 14, 1971
Aug. 15, 1971
Aug. 16, 1971
Aug. 17, 1971
Aug. 18, 1971
Aug. 19, 1971
Aug. 20, 1971
Aug. 21, 1971
Aug. 22, 1971
Aug. 23, 1971
Aug. 24, 1971
Aug. 25, 1971
Aug. 26, 1971
Aug. 27, 1971
Aug. 28, 1971
Aug. 29, 1971
Aug. 30, 1971
Aug. 31, 1971
T ., „., ET-cm
Irrigation East
cm T
Lysimeter
.45
.45
.52
2.57 .86
.72
.64
_
-
.36
-.21
-
.26
.05
.26
.22
.32
.32
.48
.53
.41
.58
.58
-
10.18
-
.16
.18
.27
-
-
-
.33
.29
.46
.55
9.25 .28
.50
ET-cm
West
Lysimeter
.73
.73
.85
.70
1.02
.95
—
-
.50
.53
-
.35
.66
.37
.38
.46
.66
.69
.67
.90
.90
.88
-
-
-
.74
.69
.65
-
-
—
.33
.29
.46
.55
.28
.50
. Cumu-
Average . ^ .
ET-cm latlVe
cm
.59
.59
.68
.78
.87
.79
.63
.56
.43
.16
.15
.31
.36
.32
.30
.39
.49
.58
.60
.66
.74
.73
.69
.00
.51
.45
.43
.46
.45
.46
.35
.33
.29
.46
.55
.28
.50
33.65
34.24
34.92
35.70
36.57
37.86
37.99
38.55
38.98
39.14
39.29
39.60
39.96
40.28
40.58
40.97
41.46
42.04
42.64
43.30
44.04
44.77
45.46
45.46
45.97
46.42
46.85
47.31
47.76
48.22
48.57
48.90
49.19
49.65
50.20
50.48
50.98
241
-------
Table 34. Continued
Date
Sept.
Sept.
Sept.
Sept.
Sept.
Sept.
Sept.
Sept.
Sept.
Sept.
Sept.
1,
2,
3,
4,
5,
6,
7,
8,
9,
10
11
D • T -i 4.- ET-cm
Rain Irrigation _,
liast
cm cm T .
Lysimeter
1971
1971 .74
1971
1971
1971
1971 .05
1971
1971 1.21
1971
, 1971
, 1971
.49
.56
.42
.43
.48
.00
.54
.00
.18
.48
.52
ET-cm
West
Lysimeter
.49
.53
.42
.43
.48
.00
.54
.00
.92
.48
.52
Average
.49
.55
.42
.43
.48
.00
.54
.00
.55
.48
.52
Cumu-
&
cm
51.47
52.02
52.44
52.87
53.35
53.35
53.89
53.89
54.44
54.92
55.44
242
-------
Table 35. Average soil water content (9) of six sites in the field, as
measured by the neutron probe, and equivalent depth of water
in the soil profile for alfalfa in 1971, and for oats in 1970,
Date
May 13,
May 31,
June
June
June
June
July
July
July
July
July
Aug.
Aug.
Aug.
Aug.
Aug.
Aug.
Aug.
Sept
July
Aug.
Aug.
Aug.
9,
11
22
29
8,
10
19
21
22
3,
16
18
19
29
30
31
. 8
31
2,
4,
8,
1971
1971
1971
, 1971
, 1971
, 1971
1971
, 1971
, 1971
, 1971
, 1971
1971
, 1971
, 1971
, 1971
, 1971
, 1971
, 1971
, 1971
, 1970
1970
1970
1970
30
.153
.290
.259
.312
.202
.315
.223
.321
.231
.313
.301
.252
.197
.316
.302
.244
.321
.306
.275
.197
.163
.127
.112
45
.268
.284
.283
.314
.248
.303
.259
.322
.266
.318
.305
.276
.244
.322
.310
.279
.325
.314
.288
.295
.273
.250
.233
Depth
75
.267
.247
.264
.294
.238
.260
.246
.280
.253
.310
.302
.264
.246
.320
.311
.272
.325
.316
.280
.257
.262
.257
.247
- cm
105
.276
.262
.281
.289
.273
.283
.277
.275
.279
.307
.311
.294
.285
.334
.343
.308
.335
.343
.313
.295
.295
.290
.288
135
.308
.350
.378
.375
.327
.382
.377
.371
.380
.386
.386
.385
.381
.402
.404
.389
.400
.398
.389
.378
.380
.377
.378
165
.373
.388
.408
.403
.396
.413
.405
.400
.413
.414
.412
.414
.413
.419
.421
.420
.419
.420
.411
.462
.463
.455
.462
Equiv.
Water
Depth
(cm)
46
52
53
57
47
56
51
56
52
59
58
54
50
61
60
54
61
60
56
.407
.556
.766
.456
.947
.600
.121
.990
.128
.255
.286
.116
.304
.151
.386
.845
.540
.641
.370
243
-------
Table 36. Average soil water content (8) of two sites in two lysimeters
as measured by the neutron probe, and equivalent depth of
water in the soil profile for alfalfa in 1971.
Date
May 13, 1971
May 31, 1971
June 9, 1971
June 11, 1971
June 22, 1971
June 29, 1971
July 8, 1971
July 10, 1971
July 19, 1971
July 21, 1971
July 22, 1971
Aug. 3, 1971
Aug. 16, 1971
Aug. 18, 1971
Aug. 19, 1971
Aug. 29, 1971
Aug. 30, 1971
Aug. 31, 1971
Sept. 8, 1971
Depth - cm
30
.205
.283
.256
.311
.207
.315
.204
.325
.204
.309
.299
.221
.154
.311
.290
.212
.318
.296
.255
45
.262
.283
.277
.314
.250
.308
.233
.317
.226
.316
.295
.226
.162
.311
.291
.224
.323
.296
.250
60
.279
.292
.301
.332
.278
.294
.258
.302
.249
.327
.308
.239
.177
.318
.300
.232
.329
.310
.258
75
.302
.312
.326
.344
.311
.304
.280
.281
.265
.332
.323
.257
.189
.272
.298
.237
.327
.320
.277
82.5
.325
.333
.337
.353
.322
.307
.287
.280
.264
.328
.325
.257
.185
.252
.284
.228
.314
.315
.273
Equivalent
Water Depth
(cm)
22.433
26.109
25.310
28.765
22.362
27.369
21.020
27.500
20.371
28.283
27.155
20.704
14.826
26.767
25.957
19.765
28.585
26.972
23.041
244
-------
Table 37. Average soil water content (6) of four sites in the field, as measured by the gamma probe,
for alfalfa in 1971.
Ul
Date
May 14
May 31
June 9
June 11
June 22
June 30
July 8
July 10
July 19
July 21
July 21
July 22
Aug. 3
Aug . 16
Aug. 18
Aug. 19
Aug. 29
Aug. 30
Aug. 31
Sept. 8
Depth - cm
7.5
.260
.319
.231
.333
.165
.299
.211
.361
.192
.325
.327
.309
.241
.159
.298
.329
.208
.353
.322
.287
15
.264
.297
.234
.290
.202
.299
.246
.342
.231
.313
.326
.302
.251
.186
.271
.330
.228
.346
.322
.285
22.5
.236
.252
.205
.284
.149
.252
.226
.302
.191
.267
.289
.265
.220
.171
.260
.274
.196
.303
.282
.240
30
.240
.230
.216
.264
.163
.250
.234
.291
.209
.277
.292
.271
.233
.192
.233
.280
.208
.290
.265
.244
37.5
.264
.241
.238
.275
.202
.246
.249
.287
.234
.289
.293
.276
.250
.226
.236
.282
.250
.304
.277
.264
45
.271
.255
.261
.298
.228
.263
.269
.316
.257
.314
.339
.318
.269
.244
.289
.332
.263
.334
.312
.276
52.5
.269
.241
.249
.274
.223
.224
.258
.278
.258
.309
.328
.300
.268
.237
.279
.324
.268
.334
.316
.277
60
.281
.244
.244
.293
.223
.237
.264
.380
.248
.312
.329
.318
.277
.253
.295
.345
.281
.363
.354
.292
67.5
.241
.225
.220
.249
.224
.217
.257
.229
.234
.280
.294
.285
.265
.228
.264
.306
.247
.321
.310
.291
75
. 2.^2
.220
.230
.246
.228
.229
.254
.235
.241
.301
.304
.288
.265
.247
.276
.309
.293
.322
.319
.283
90
.264
.255
.257
.263
.265
.269
.287
.258
.273
.304
.324
.311
.293
.289
.274
.334
.291
.320
.322
.290
105
.273
.267
.283
.294
.299
.306
.324
.296
.305
.333
.351
.356
.344
.334
.320
.379
.359
.395
.400
.368
120
.305
.293
.325
.317
.328
.347
.366
.336
.339
.364
.378
.379
.364
.361
.376
.417
.366
.403
.421
.366
-------
Table 38. Average soil water content (6)
probe, for alfalfa in 1971.
of two sites in two lysimeters as measured by the gamma
Date
May 14
May 31
June 9
June 11
June 22
June 30
July 8
July 10
July 19
July 21
July 21
July 22
Aug. 3
Aug . 16
Aug. 18
Aug. 19
Aug. 29
Aug. 30
Aug. 31
Sept. 8
Depth - cm
7.5
.270
.312
.226
.326
.161
.289
.220
.351
.180
.297
.290
.281
.220
.141
.287
.290
.168
.327
.310
-
15
.265
.311
.248
.319
.181
.294
.236
.340
.186
.307
.304
.304
.223
.158
.296
.309
.184
.311
.312
-
22.5
.262
.283
.238
.315
.184
.274
.239
.351
.183
.315
.285
.272
.209
.156
.295
.302
.191
.324
.308
-
30
.280
.294
.256
.336
.218
.307
.253
.339
.206
.324
.311
.300
.272
.180
.322
.324
.208
.361
.311
-
37.5
.286
.284
.273
.305
.238
.288
.265
.371
.240
.325
.323
.296
.233
.174
.311
.314
.219
.339
.318
-
45
.300
.287
.281
.330
.242
.296
.274
.334
.232
.315
.311
.296
.240
.175
.309
.328
.220
.343
.315
-
52.5
.324
.311
.316
.348
.262
.301
.297
.293
.255
.338
.335
.312
.244
.186
.345
.331
.225
.360
.342
—
60
.326
.307
.311
.356
.275
.312
.312
.280
.270
.332
.325
.311
.263
.190
.326
.331
.233
.356
.347
—
67.5
.332
.306
.317
.347
.290
.283
.295
.287
.243
.317
.331
.319
.258
.174
.306
.313
.235
.341
.334
—
75
.346
.333
.352
.363
.313
.321
.327
.225
.285
.327
.342
.352
.285
.205
.258
.326
.242
.361
.354
—
82.5
.346
.330
.350
.370
.323
.325
.325
.296
.274
.355
.372
.372
.269
.203
.245
.270
.223
.325
.341
—
-------
Table 39. Climatic data and potential evapotranspiration as calculated by Penman modified method
for alfalfa in 1971.
Radiation
Date Total Net Long
ly/min ly/min ly/min
May 15
May 16
May 17
May 18
May 19
May 20
May 21
May 22
May 23
May 24
May 25
May 26
May 27
May 28
May 29
May 30
May 31
June 1
June 2
June 3
June 4
June 5
June 6
June 7
June 8
June 9
June 10
.27
.50
.22
.43
.49
.60
.39
.57
.43
.51
.45
.50
.42
.40
.40
.40
.40
.31
.38
.35
.42
.43
.48
.48
.44
.42
.28
.14
.33
.08
.25
.30
.43
.22
.38
.25
.33
.27
.31
.29
.23
.23
.23
.23
.17
.22
.24
.26
.26
.30
.30
.28
.27
.15
.07
.08
.09
.10
.09
.08
.09
.08
.10
.09
.09
.09
.07
.09
.08
.09
.08
.08
.08
.08
.07
.08
.08
.08
.07
.07
.07
Wind
mi /day
71.9
84.1
160.6
62.8
74.2
90.0
77.7
173.0
76.4
67.6
64.4
5.7
.3
84.8
84.8
84.8
84.8
86.4
66.5
59.5
108.5
94.5
79.4
79.4
45.0
62.0
60.0
Temperature
Dry Bulb
°C
18.61
16.11
11.11
6.11
8.20
12.30
10.00
15.40
9.44
9.44
11.70
14.40
18.75
14.86
14.86
14.86
14.86
16.53
15.00
17.64
17.79
16.66
14.72
14.72
19.00
20.80
19.00
Wet Bulb
°C
11.67
10.83
6.67
2.50
4.30
6.39
5.56
7.08
5.83
6.94
7.78
9.17
10.55
9.44
9.44
9.44
9.44
10.00
8.89
10.95
11.24
10.97
10.28
10.28
11.67
13.00
13.20
Soil
°C
9.50
9.50
10.00
10.75
9.65
9.25
8.50
8.00
7.75
8.25
8.00
9.50
8.63
10.00
10.00
10.00
10.00
8.50
10.75
10.87
10.00
10.50
10.00
10.00
10.50
10.75
11.50
Vapour Pressure
Saturated
MB
21.44
18.31
13.21
9.42
10.86
14.40
12.27
17.50
11.82
11.82
13.71
16.45
21.60
16.89
16.89
16.89
16.89
18.80
17.05
20.10
20.37
18.97
16.74
16.74
21.99
24.40
21.20
Actual
MB
17.41
15.25
10.65
7.35
8.61
10.90
9.71
12.70
9.74
10.38
11.46
13.39
16.89
13.76
13.76
13.76
13.76
15.02
13.51
16.30
16.57
15.67
14.16
14.16
17.73
20.00
18.20
ET-Pen ET-cum
cm/ day cm
.30
.59
.19
.37
.47
.51
.36
.74
.40
.49
.45
.53
.49
.43
.43
.43
.43
.35
.41
.50
.56
.49
.53
.53
.54
.55
.31
.30
.89
1.08
1.45
1.92
2.43
2.79
3.53
3.93
4.42
4.87
5.40
5.89
6.32
6.75
7.18
7.61
7.96
8.37
8.87
9.43
9.92
10.45
10.98
11.52
12.07
12.38
-------
Table 39. Continued
CO
^
00
Radiation
Date Total Net Long
ly/min ly/min ly/min
June 11
June 12
June 13
June 14
June 15
June 16
June 17
June 18
June 19
June 20
June 21
June 22
June 23
June 24
June 25
June 26
June 27
June 28
June 29
June 30
July 1
July 2
July 3
July 4
July 5
July 6
July 7
July 8
.28
.46
.50
.43
.43
.41
.43
.38
.34
.48
.48
.43
.39
.41
.46
.51
.32
.53
.42
.38
.43
.45
.45
.45
.45
.43
.42
.47
.15
.30
.32
.27
.27
.27
.27
.24
.22
.33
.33
.29
.27
.28
.32
.36
.20
.34
.28
.23
.29
.29
.29
.29
.29
.27
.27
.30
.07
.08
.08
.07
.06
.07
.08
.06
.05
.06
.06
.05
.04
.05
.05
.05
.05
.08
.06
.07
.06
.07
.07
.07
.07
.07
.07
.07
Wind
mi /day
60.0
60.0
47.1
60.0
54.5
60.9
61.6
72.4
62.8
52.4
52.4
56.6
123.0
82.9
83.1
83.3
100.6
128.8
126.4
65.7
65.0
78.0
78.6
89.7
93.0
63.3
94.6
93.0
Temperature
Dry Bulb
°C
19.00
16.90
17.17
20.00
21.88
21.50
18.61
24.52
26.00
23.06
23.06
24.86
26.75
26.70
26.05
25.40
25.56
18.89
23.72
19.44
22.43
20.00
19.44
19.17
19.44
20.00
20.28
20.28
Wet Bulb
°C
13.20
11.11
11.30
13.82
14.28
14.52
12.78
15.56
16.20
15.56
15.56
15.90
15.00
14.75
14.50
14.25
14.17
11.67
14.44
12.50
12.12
14.44
14.72
13.06
13.33
13.39
14.72
15.28
Soil
°C
11.50
12.00
11.80
10.12
9.67
9.70
12.50
12.30
12.58
12.25
12.25
9.06
13.00
13.00
13.70
14.75
13.50
14.25
15.60
16.00
15.75
16.00
15.50
15.75
16.00
16.25
16.00
16.75
Vapour Pressure
Saturated
MB
21.20
19.30
19.50
23.82
26.21
25.62
21.44
30.60
33.48
28.13
28.13
31.28
37.90
34.85
33.55
32.25
32.58
21.82
29.26
22.58
27.18
23.37
22.58
22.20
22.58
23.37
23.77
23.77
Actual
MB
18.20
15.92
16.10
19.88
21.78
21.58
18.06
25.45
27.76
23.75
23.75
26.07
30.43
27.87
26.84
25.81
25.95
17.62
23.86
18.54
21.19
20.13
19.83
18.64
19.03
19.81
20.54
20.86
ET-Pen ET-cum.
cm/ day cm
.31
.57
.56
.53
.56
.52
.50
.52
.54
.60
.60
.61
.58
.66
.70
.73
.47
.67
.62
.45
.64
.56
.54
.56
.55
.53
.53
.58
12.69
13.26
13.82
14.35
14.91
15.43
15.93
16.45
16.99
17.59
18.19
18.80
19.38
20.04
20.74
21.47
21.94
22.61
23.23
23.68
24.32
24.88
25.42
25.98
26.53
27.06
27.59
28.17
-------
Table 39. Continued
c\>
Radiation
Date Total Net Long
ly/min ly/min ly/min
July 9
July 10
July 11
July 12
July 13
July 14
July 15
July 16
July 17
July 18
July 19
July 20
July 21
July 22
July 23
July 24
July 25
July 26
July 27
July 28
July 29
July 30
July 31
Aug. 1
Aug. 2
Aug. 3
Aug. 4
Aug. 5
.43
.50
.51
.54
.53
.42
.44
.50
.49
.37
.29
.20
.31
.37
.31
.48
.48
.45
.45
.45
.48
.46
.44
.42
.40
.38
.42
.28
.27
.32
.33
.36
.36
.28
.30
.33
.34
.26
.17
.09
.16
.22
.17
.31
.32
.29
.29
.29
.32
.30
.28
.26
.25
.23
.25
.15
.07
.08
.08
.07
.07
.06
.06
.07
.05
.04
.06
.07
.08
.08
.07
.07
.07
.07
.07
.07
.07
.07
.07
.07
.07
.07
.08
.08
Wind
mi/day
62.1
52.2
52.2
52.2
71.4
72.2
68.4
36.3
43.7
46.0
52.4
34.6
15.0
53.9
67.2
42.9
42.9
42.9
45.0
38.1
35.6
34.4
33.2
32.0
30.8
29.8
48.4
50.7
Temperature
Dry Bulb
°C
19.17
18.06
18.89
20.00
20.58
21.11
21.39
20.83
25.00
27.78
22.78
16.94
15.00
16.39
17.78
18.60
19.17
19.44
20.00
18.61
18.06
18.08
18.10
18.12
18.14
19.17
15.56
17.22
Wet Bulb Soil
°C °C
13.89
12.50
13.06
13.61
15.00
18.33
18.89
16.39
18.06
20.28
18.06
14.72
13.75
14.58
15.00
15.00
15.00
15.00
15.56
16.11
17.78
17.34
16.90
16.46
16.02
15.56
13.33
13.61
16.50
16.50
16.50
16.50
16.50
16.25
16.25
16.50
16.25
16.25
16.50
16.50
16.50
16.25
16.50
16.50
16.25
16.25
16.25
16.00
16.00
15.75
15.75
15.75
15.75
15.75
15.50
15.50
Vapour Pressure
Saturated
MB
22.20
20.71
21.81
23.37
24.18
25.02
25.44
24.60
31.55
37.00
27.66
19.30
17.05
18.64
20.35
21.44
22.20
22.58
23.37
21.44
20.71
21.01
21.31
21.61
21.91
22.20
17.67
19.65
Actual
MB
19.12
17.48
18.42
19.65
20.94
23.39
23.98
22.00
27.48
32.61
24.90
18.01
16.32
17.58
18.73
19.33
19.77
19.99
20.78
19.98
20.55
20.46
20.37
20.28
20.19
20.09
16.38
17.55
ET-Pen ET-cum.
cm/ day cm
.51
.59
.61
.68
.67
.52
.55
.62
.68
.53
.34
.16
.27
.37
.32
.56
.58
.53
.54
.52
.55
.53
.51
.49
.47
.43
.43
.28
28.68
29.27
29.88
30.56
31.23
31.75
32.30
32.92
33.60
34.13
34.47
34.63
34.90
35.27
35.59
36.15
36.73
36.26
37.80
38.32
38.87
39.40
39.91
40.40
40.87
41.30
41.73
42.01
-------
Table 39. Continued
Radiation
Date Total Net Long
ly/min ly/min ly/min
Aug. 6
Aug. 7
Aug. 8
Aug. 9
Aug. 10
Aug. 11
Aug. 12
Aug. 13
Aug. 14
Aug. 15
t^ Aug. 16
g Aug. 17
Aug. 18
Aug. 19
Aug. 20
Aug. 21
Aug. 22
Aug. 23
Aug. 24
Aug. 25
Aug. 26
Aug. 27
Aug. 28
Aug. 29
Aug. 30
Sept. 1
Sept. 2
Sept. 3
.37
.36
.24
.24
.36
.47
.39
.43
.43
.41
.43
.48
.34
.35
.29
.37
.42
.44
.37
.45
.19
.30
.30
.38
.40
.45
.43
.41
.24
.25
.15
.15
.23
.31
.24
.27
.27
.27
.29
.34
.20
.19
.15
.22
.27
.28
.22
.29
.08
.17
.18
.24
.25
.30
.27
.24
.06
.04
.04
.04
.06
.07
.07
.07
.07
.06
.05
.05
.07
.09
.08
.07
.06
.07
.07
.07
.07
.07
.06
.06
.06
.06
.07
.09
Wind
mi /day
43.9
60.9
63.6
63.6
56.7
47.6
69.7
57.9
60.7
46.9
41.0
26.9
8.7
82.7
41.8
49.6
37.3
58.3
48.1
32.3
21.5
39.4
40.7
40.8
75.0
62.5
60.0
100.8
Temperature
Dry Bulb
°C
23.89
28.89
27.78
27.78
22.22
21.67
22.22
20.83
20.28
23.06
26.11
26.11
20.56
15.00
15.83
18.06
21.11
20.56
18.89
19.17
18.33
18.61
21.39
22.22
20.28
22.50
19.44
12.50
Wet Bulb
°C
16.67
18.33
17.78
17.78
15.00
13.61
13.89
14.17
13.89
14.72
16.39
16.39
14.31
12.08
12.78
14.72
15.83
15.83
14.44
14.44
15.56
16.11
17.50
18.33
16.67
17.22
15.00
9.72
Soil
°C
15.50
15.75
16.00
16.00
16.50
16.50
17.25
17.75
17.75
17.75
18.00
18.25
17.75
18.50
18.75
18.50
18.25
18.00
18.00
17.75
18.00
18.25
18.00
17.50
17.50
17.50
17.00
17.00
Vapour Pressure
Saturated
MB
29.55
39.39
37.00
37.00
26.76
25.87
26.76
24.59
23.77
28.13
33.65
33.65
24.18
17.05
17.99
20.71
25.02
24.18
21.82
22.20
21.07
21.44
25.44
26.76
23.77
27.20
22.58
14.49
Actual
MB
25.34
33.21
31.16
31.16
22.55
21.19
21.91
20.71
20.05
23.27
27.97
27.97
20.54
15.35
16.21
18.67
21.94
21.43
19.23
19.45
19.45
19.98
23.17
24.48
21.66
24.12
19.99
12.88
ET-Pen ET-cum.
cm/ day cm
.48
.55
.35
.35
.46
.60
.50
.54
.52
.54
.60
.69
.39
.34
.27
.40
.51
.54
.41
.53
.15
.30
.34
.47
.48
.59
.51
.40
42.49
43.04
43.39
43.74
44.20
44.80
45.30
45.84
46.36
46.90
47.50
48.19
48.58
48.92
49.19
49.59
50.10
50.64
51.05
51.58
51.73
52.03
52.37
52.84
53.32
54.18
54.69
55.09
-------
Table 39. Continued
Radiation
Date
Sept.
Sept.
Sept.
Sept.
Sept.
Sept.
Sept.
Sept.
Total Net Long
ly/min ly/min ly/min
4
5
6
7
8
9
10
11
.28
.45
.45
.40
.38
.38
.38
.36
.13
.30
.29
.25
.22
.22
.23
.21
.09
.07
.07
.08
.08
.08
.08
.07
Wind
mi/ day
53.3
50.3
43.7
74.3
45.5
44.0
42.3
35.4
Temperature
Dry Bulb
°C
10.83
18.06
18.89
16.39
14.44
11.67
13.89
17.22
Wet Bulb
°C
8.06
11.11
12.22
12.50
11.94
10.67
11.39
13.06
Soil
°C
16.50
16.50
16.00
15.75
15.50
15.50
15.25
15.25
Vapour Pressure
Saturated
MB
12.97
20.70
21.82
18.64
16.45
13.71
15.86
19.65
Actual
MB
11.37
16.68
17.94
16.38
15.00
13.07
14.41
17.23
ET-Pen ET-cum.
cm/ day cm
.23
.55
.55
.44
.38
.35
.38
.38
55.32
55.87
56.42
56.86
57.24
57.59
57.97
58.35
Ol
-------
Table 40. Electrical conductivity (mmho/cm) of drain effluent measured
periodically in the field with a portable conductivity meter
in 1971.
June 10
18
24
29
30
July 2
5
6
8
9
12
13
15
19
21
22
26
27
28
29
30
Aug. 2
6
12
16
17
18
19
20
21
23
24
25
26
27
28
30
31 3500
Drain
234
2050
1890
1830
1710
1690
1840
1840
1750
1660
1730
1830
1740
1910 1630
1770
1690
1420
1960
1790
1610
1660
1510
2340 2460 1650
2220 1710
1970 1750
1710
1710
1730
1700
1710
1610
1740
1710
1730
1990 1710
5
1950
1950
1800
1640
1530
1910
1770
1660
1670
1600
1640
1620
1630
1820
1610
1720
1650
1610
1660
1670
1540
1520
1490
1450
1390
1540
1550
1610
1560
1570
1550
1520
1540
1470
1590
1570
1570
1540
6 Airport
1560
1440
1330
1660
1560
1520
1890
1490
1500
1470
1640
1680
1520
1290
1420
1470
1460
1360
1140
1520
1390
1450
1550
1390
1350
1430
1450
1420 1630
252
-------
Table 40. Continued
^ fc Drain
Date — x ^ ;
Airport
Sept. 1
2
3
8
1960 1770
1780
1750
1670
1560
1560
1610
1530
1440
1500
9 1670 1460
10 1610 1450 1550
13 1480
14 1540
15 1460
16 1440
17 1375
18 1370
19 1395
20 1400
21 1390
22 1390
23 1425
253
-------
Table 41. Typical composition of Drain 5 effluent collected at one-hour intervals on August 4, 1971.
IN)
Ol
1 1 1 1
Ca^* Mg**
(meq/1) (meq/1)
13.2 6.7
12.4 6.7
6.5
6.7
6.7
6.6
6.6
7.2
6.7
12.0 7.6
13.2 6.6
6.9
6.5
6.6
6.7
6.7
6.7
6.7
6.7
6.7
6.6
6.7
6.7
$ 12. 7 6.7
8
H
Na+
(meq/1)
1.1
1.1
1.1
1.1
1.1
1.2
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.2
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
co--
(meq/1)
0.90
1.3
1.9
1.9
1.1
2.2
1.9
2.4
1.1
1.3
1.9
1.1
1.1
1.5
1.3
1.1
1.9
1.9
1.3
1.9
2.0
1.5
1.6
HCO"3
(meq/1)
11.1
12.0
10.7
10.3
10.2
10.7
9.4
10.1
9.6
10.9
10.8
10.4
10.9
11.2
10.6
11.1
11.1
10.6
10.2
10.7
10.7
10.4
10.5
10.6
Cl
(meq/1)
0.34
0.34
0.35
0.35
0.35
0.45
0.34
0.40
0.34
0.34
0.38
0.38
0.32
0.35
0.35
0.35
0.32
0.35
0.38
0.38
0.40
0.40
0.45
0.37
S°~4~
(meq/1)
3.8
3.4
3.6
3.9
3.9
3.9
4.0
4.0
3.9
3.9
3.6
3.8
3.8
3.8
3.9
3.7
3.7
3.2
3.7
3.7
3.6
3.8
3.4
3.7
N0~3
(ppm)
1.8
1.4
1.4
1.4
1.4
.9
2.5
1.3
1.9
1.9
1.7
1.9
2.5
1.8
2.0
1.9
1.8
2.7
2.1
2.4
2.0
2.1
1.8
1.9
EC
(ymho/cm)
1362
1365
1376
1371
1370
1379
1373
1351
1342
1347
1338
1350
1359
1341
1334
1319
1351
1370
1358
1382
1380
1375
1375
1359
II
Ca concentration - solubility of CaSO,
-------
Table 42. Piozometric data typical of conditions during the irrigation season on the Hullinger
farm (6-29-71).
Water Table Depth (ft)
Location
1W100N4
1W100N50
3W5N4
3W5N47
3W100N4
3W100N43
5W175N12
5W175N50
6W5N12
6W5N50
3W100-20
3W5-20
1W100-20
1W100-150
2W100-150
3E20-150
3E5-150
3W5-150
3W20-150
3W100-150
4W100-150
5W175-150
5W175-20
12
3.63
3.84
3.45
3.53
3.24
2.68
3.30
3.12
2.80
3.00
3.77
3.99
4.31
5.44
4.70
4.56
4.60
4.64
4.43
4.31
2.99
3.77
4.42
9
3.66
3.83
3.48
3.45
3.33
2.61
3.22
3.13
2.78
3.05
3.78
3.99
4.33
5.40
4.70
4.56
4.60
4.42
4.31
3.01
3.80
4.44
6
3.60
3.83
3.47
3.46
2.42
2.62
3.22
3.14
2.74
2.76
3.75
4.11
4.33
5.42
4.73
4.57
4.60
4.64
4.43
4.32
3.03
3.80
4.44
Elev.* Top
of Pipe
58
59
63
63
64
63
71
71
73
73
64
63
59
59
62
63
63
63
63
64
67
71
72
.81
.14
.35
.43
.38
.91
.06
.20
.59
.87
.81
.67
.51
.16
.05
.36
.66
.87
.89
.94
.07
.50
.17
Water Table Depth (ft)
Location
6E50-150
6E20-150
6E5-150
6W5-150
6W20-150
6W43-150
6W5-20
6W149-400
6W50-400
6W20-400
6W5-400
6E5-400
6E20-400
6E50-400
6E100-400
5W175-400
5W100-400
5W20-400
5W5-400
5E5-400
5E20-400
4W100-400
4W20-400
12
4.39
4.44
4.62
4.50
4.32
3.99
4.24
4.65
3.38
4.00
4.40
4.50
4.30
4.30
3.90
3.78
4.02
4.22
2.01
4.38
4.02
4.25
4.25
9
4.40
4.46
4.60
4.50
4.35
3.97
4.34
4.66
4.00
4.35
4.40
5.80
4.29
4.28
3.97
3.77
4.02
4.24
2.01
4.40
4.00
4.28
4.25
6
4.40
4.49
4.75
4.55
4.35
4.02
4.30
4.62
4.02
4.38
4.42
6.00
4.35
4.30
3.98
3.77
3.99
4.20
2.02
4.43
4.02
4.25
4.22
Elev.* Top
of Pipe
73
74
74
74
74
75
74
76
74
74
73
73
73
73
73
71
70
69
69
68
68
67
66
.57
.04
.44
.54
.73
.18
.50
.60
.72
.07
.86
.85
.41
.05
.21
.07
.25
.13
.05
.97
.60
.53
.41
-------
Table 42. Continued
Ul
Water Table Depth (ft)
Location
4W5-400
4E5-400
4E20-400
3W100-400
3W50-400
3W20-400
3W5-400
3E5-400
3E20-400
3E50-400
2W100-400
2W20-400
2W5-400
2E5-400
2E20-400
1W100-400
1W20-400
12
4.29
4.26
4.19
5.22
5.50
5.44
5.53
5.54
5.35
5.34
5.02
5.01
5.02
5.25
5.10
5.23
5.67
9
4.30
4.28
4.19
5.24
5.58
5.44
5.51
5.55
5.38
5.30
5.06
5.02
5.02
5.20
5.09
5.24
5.70
6
4.32
4.29
4.20
5.25
5.59
5.47
5.50
5.50
5.35
5.35
5.02
5.01
5.01
5.20
5.11
5.23
5.71
Elev.* Top
of Pipe
66.25
66.08
65.73
65.24
64.65
64.04
63.80
63.62
63.14
62.68
61.85
60.47
60.24
60.09
59.82
58.37
57.37
Water Table Depth (ft)
Location
1W5-400
1W100-650
2W100-650
3E20-650
3E5-650
3W5-650
3W20-650
3W100-650
4W100-650
5W175-650
6E50-650
6E20-650
6E5-650
6W5-650
6W20-650
6W50-650
6W150-650
12
6.90
6.03
6.30
6.30
6.30
6.20
6.30
5.72
6.23
6.57
6.83
6.73
6.74
6.80
7.00
9 6
5.60 5.62
6.91
6.03
6.32
6.30
6.28
6.18
6.30
6.12
5.77
6.32
6.58
6.75
6.73
6.77
6.81
7.02
Elev.* Top
of Pipe
57.11
58.85
61.00
63.05
62.66
62.81
63.05
64.66
68.59
72.42
74.22
74.75
75.11
75.28
75.44
75.82
77.23
*Elevation above mean sea level is value plus 5200 feet,
-------
Table 43. Piezometric data typical of early spring conditions on the Hullinger farm (5-4-71).
Water Table Depth (ft)
Location
1W100N4
1W100N50
3W5N4
3W5N47
3W100N4
3W100N43
5W175N12
5W175N50
6W5N12
6W5N50
3W100-20
3W5-20
1W100-20
1W100-150
2W100-150
3E20-150
3E5-150
3W5-150
3W20-150
3W100-150
4W100-150
5W175-150
5W175-20
12
6.27
6.59
6.14
6.21
5.94
5.38
6.45
6.35
6.51
6.78
6.40
6.54
6.96
7.62
7.10
6.98
7.02
7.06
6.85
6.67
5.28
6.59
7.51
9 6
6.27
6.61
6.14
6.20
5.94 5.94
5.36 5.37
6.42
6.38
6.50
6.78
6.42
6.54
6.96
7.62
7.10
6.98
7.02
6.85
6.67
5.28 5.33
6.59
7.51
Elev.* Top
of Pipe
58.85
59.14
63.35
63.43
64.38
63.91
71.06
71.20
73.59
73.87
64.81
63.67
59.51
59.16
62.05
63.36
63.66
63.87
63.89
64.94
67.07
71.50
72.17
Water Table Depth (ft)
Location
6E50-150
6E20-150
6E5-150
6W5-150
6W20-150
6W43-150
6W5-20
6W149-400
6W50-400
6W20-400
6W5-400
6E5-400
6E20-400
6E50-400
6E100-400
5W175-400
5W100-400
5W2 0-400
5W5-400
5E5-400
5E20-400
4W100-400
4W20-400
12
7.46
7.53
7.69
7.61
7.55
7.74
7.64
8.02
7.40
7.24
7.22
7.35
7.05
7.00
6.49
6.16
6.28
6.28
6.37
6.40
6.17
6.18
6.10
9 6
7.46
7.53
7.69
7.61
7.57
7.76
7.66
8.02
7.40
7.24
7.22
7.37
7.05
6.99
6.58
6.20
6.28
6.28
6.37
6.40
6.18
6.18
6.10
Elev.* Top
of Pipe
73.57
74.04
74.44
74.54
74.73
75.18
74.50
76.60
74.72
74.07
73.86
73.85
73.41
73.05
73.21
71.07
70.25
69.13
69.05
68.97
68.60
67.53
66.41
-------
Table 43. Continued
00
Water Table Depth (ft)
Location
4W5-400
4E5-400
4E20-400
3W100-400
3W50-400
3W20-400
3W5-400
3E5-400
3E20-400
3E50-400
2W100-400
2W20-400
2W5-400
2E5-400
2E20-400
1W100-400
1W20-400
12
6.12
6.11
6.02
7.12
7.46
7.43
7.53
7.53
7.28
7.22
7.00
6.97
6.95
6.98
6.90
6.90
7.20
9 6
6.12
6.11
6.02 6.02
7.12
7.46
7.43
7.52
7.53
7.29
7.23
7.01
6.97
6.96
6.97
6.89
6.91
7.20
Elev.* Top
of Pipe
66.25
66.08
65.73
65.24
64.65
64.04
63.80
63.62
63.14
62.68
61.85
60.47
60.24
60.09
59.82
58.37
57.37
Water Table Depth (ft)
Location
1W5-400
1W100-650
2W100-650
3E20-650
3E5-650
3W5-650
3W20-650
3W100-650
4W100-650
5W175-650
6E50-650
6E20-650
6E5-650
6W5-650
6W20-650
6W50-650
6W150-650
12
7.84
7.04
7.32
7.34
7.30
7.23
7.45
7.70
8.44
8.68
8.88
8.95
8.92
9.03
9.48
9 6
7.14
7.84
7.04
7.33
7.36
7.33
7.24
7.46
7.78
8.42
8.67
8.89
8.95
8.93
9.03
Elev.* Top
of Pipe
57.11
58.85
61.00
63.05
62.66
62.81
63.05
64.66
68.59
72.42
74.22
74.75
75.11
75.28
75.44
75.82
77.23
*Elevation above mean sea level is value plus 5200 feet.
-------
Table 44. Electrical conductivity of the soil solution (EC ) as calcu-
s
lated from average values of electrical conductivity of
saturation extract (EC ), soil water content by weight at
saturation (W ), and from field water content by weight (W),
which was obtained from the average volumetric moisture
content (6) of each layer and from bulk density determin-
ations .
Soil Depth
Increment (ft)
June 22
Block 3 0-1
1-2
2-3
3-4
4-5
5-6
Block 5 0-1
1-2
2-3
3-4
4-5
5-6
Block 6 0-1
1-2
2-3
3-4
4-5
5-6
Block 7 0-1
1-2
2-3
3-4
4-5
5-6
August 3
Block 3 0-1
1-2
2-3
3-4
4-5
EC
e
(mmho/cm)
2.18
2.07
2.28
2.78
2.73
2.86
1.47
1.56
1.78
1.75
1.66
1.80
2.31
4.07
4.82
3.96
3.41
2.80
3.15
3.69
2.91
2.74
2.79
1.78
2.17
1.96
2.64
2.36
2.90
W
e
38.9
37.8
37.6
37.1
41.1
54.0
38.5
29.9
25.8
32.5
39.8
38.3
37.0
41.8
42.5
35.6
33.4
36.5
34.3
35.7
44.0
34.6
30.3
36.5
35.3
36.5
35.3
34.0
36.0
e
.224
.265
.281
.325
.345
.409
.187
.235
.244
.275
.327
.379
.203
.279
.303
.363
.405
.411
.212
.246
.292
.360
.409
.409
.303
.308
.305
.328
.401
W
.157
.185
.197
.227
.241
.286
.120
.151
.156
.176
.210
.243
.130
.179
.194
.233
.260
.264
.137
.159
.189
.232
.264
.264
.212
.216
.213
.229
.280
EC
s
(mmho/cm)
5.40
4.23
4.35
4.55
4.65
5.40
4.71
3.09
2.94
3.23
3.14
2.84
6.57
9.50
10.57
6.02
4.38
3.87
7.88
8.28
6.78
4.09
3.20
2.46
3.62
3.31
4.37
3.50
3.73
259
-------
Table 44. Continued
Block 5
Block 6
Block 7
September 9
Block 3
Block 5
Block 6
Block 7
Soil Depth
Increment (ft)
0-1
1-2
2-3
3-4
4-5
0-1
1-2
2-3
3-4
4-5
0-1
1-2
2-3
3-4
4-5
0-1
1-2
2-3
3-4
4-5
0-1
1-2
2-3
3-4
4-5
0-1
1-2
2-3
3-4
4-5
0-1
1-2
2-3
3-4
4-5
EC
e
(mmho/cm)
2.06
2.10
4.15
3.02
2.98
2.49
3.60
4.86
3.51
3.61
4.25
3.29
3.26
3.10
2.81
1.62
1.48
2.26
2.74
2.60
1.38
1.19
1.65
2.22
2.31
3.09
4.10
5.36
5.22
3.70
3.15
3.35
3.12
3.18
2.24
W
e
32.5
33.9
30.0
29.1
29.4
34.7
39.3
41.3
30.8
30.9
34.8
32.5
42.5
35.6
26.5
43.8
41.0
42.8
36.4
42.1
44.6
33.4
35.9
34.5
36.6
43.7
51.5
44.2
38.6
37.8
45.1
51.0
46.0
37.8
30.1
e
.248
.269
.269
.301
.377
.278
.319
.350
.399
.411
.204
.260
.346
.392
.410
.331
.325
.327
.355
.414
.273
.284
.283
.318
.382
.268
.334
.386
.400
.411
.256
.297
.356
.383
.406
W
.159
.172
.172
.193
.242
.178
.204
.224
.256
.264
.132
.168
.223
.253
.265
.232
.228
.229
.248
.289
.176
.182
.182
.204
.245
.172
.214
.248
.256
.264
.165
.192
.230
.247
.262
EC
s
(mmho/cm)
4.21
4.14
7.24
4.55
3.62
4.85
6.94
8.95
4.22
4.23
11.20
6.36
6.21
4.36
2.81
3.06
2.66
4.22
4.02
3.79
3.50
2.18
3.26
3.76
3.45
7.85
9.86
9.55
7.87
5.30
8.61
8.90
6.25
4.87
2.57
260
-------
Table 45. Typical composition of salts in Hullinger farm soils.
Depth (in)
0-6
6-12
12-18
18-24
24-30
30-36
36-42
42-48
48-54
54-60
PH
7.5
7.5
7.6
7.7
7.7
7.7
7.8
7.6
7.4
7.4
mmhos
EC
e
1.7
2.0
3.0
3.3
3.2
3.2
3.4
3.2
3.4
2.8
Water-Soluble meq/1
Ca
12.5
20.5
27.5
27.5
28.0
27.5
28.0
28.0
32.0
30.0
Mg
5.7
6.3
16.9
23.3
22.2
22.3
24.7
21.6
19.5
12.6
Na
1.4
1.6
1.6
3.5
3.7
3.7
3.7
3.7
3.8
2.7
K
.56
.32
.28
.16
.13
.14
.16
.16
.22
.20
meq/lOOg
SO
Cl b 4
<.01 .45
<. 01 1 . 11
<. 01 1 . 32
<.01 3.74
.04 2.12
.02 4.11
<.01 2.23
<.01 2.30
<.01 1.34
<.01 1.22
Sat. %
SP
38.2
31.1
48.7
36.3
31.8
41.2
36.1
30.6
29.5
32.5
-------
Table 46. Typical composition of groundwater samples from observation
holes.
Location
2W99-19
tt
u
ii
it
1E358-400
u
u
u
1E54-728
u
u
u
4W10-745
u
it
ti
it
6W121-738
u
u
n
6W147-331
it
ii
tt
n
it
5W102-19
u
tt
n
it
it
Depth
(ft)
10
15
20
25
30
15
20
25
30
10
15
20
25
10
15
20
25
30
15
20
25
30
10
15
20
25
30
34
10
15
20
25
30
35
Ca
meq/1
9.5
9.7
9.5
9.5
10.2
11.3
10.2
10.8
11.4
16.0
15.3
16.2
15.9
9.2
9.9
9.9
9.8
8.7
9.9
9.3
9.8
10.1
8.1
9.5
9.9
9.8
9.2
10.2
11.0
11.2
10.6
10.6
11.2
12.4
Mg
meq/1
6.4
6.4
6.4
6.5
6.5
8.0
8.1
8.0
8.1
12.0
12.1
12.4
12.5
8.9
9.0
8.9
8.8
11.0
7.8
7.5
7.6
7.7
8.9
8.7
8.6
8.4
8.4
8.4
7.0
7.4
7.3
7.2
7.1
7.0
Na Cl
meq/1 meq/1
.9 .23
.9
• 9 .23
.9
.9
1.2
1.1
1.2
1.1
2.5
2.6
2.5
2.5
1.2 .23
1.2
1.2 .23
1.2
2.3
.9
.9
1.0
1.0
.9
.8
.8
.8
.8
.8
1.0
.9
.9
1.1
1.1
.9
S°4
meq/1
12.3
____
10.3
____
____
____
____
_
____
13.8
____
12.8
_
____
— __
N03
ppm
.31
—
.34
___
___
___
___
.47
.53
EC
mmho/cm
1248
1265
1248
1241
1328
1525
1462
1482
1462
2135
1977
1977
2068
1450
1368
1450
1442
1570
1404
1318
1375
1404
1235
1397
1375
1334
1334
1351
1435
1435
1361
1361
1375
1474
262
-------
Table 47. Field measurements of EC (ymhos/cm) of groundwater samples
from observation holes.
Date 5
5W102-19
May 19 1280(7)
June 5 1440(6)
June 18 1270(6)
July 13 1350(7)
Aug. 24 1200(6)
Sept. 1 1370(7)
Sept. 9 1340(7)
Sept. 16 1230(7)
2W99-19
May 18
June 3 1340(6)
June 17 1290(6)
July 12 1250(6)
Aug. 24 1250(7)
Aug. 31 1370(6)
Sept. 9 1110(7)
Sept. 16 1220(8)
1E358-400
May 18
June 5
June 18
July 12
Aug. 24
Sept. 1
Sept. 9
Sept. 16
Co. "B"
May 18
June 5
June 18 1470(7)
July 12
Aug. 21
Aug. 24
Sept. 1
Sept. 9
Sept. 16
Depth
10 15
1260 1250
1370 1350
1220 1290
1370 1330
1210 1170
1340 1320
1320 1250
1240 1210
1280 1250
1300 1300
1260 1260
1200 1240
1180 1230
1410 1350
1170 1180
1190 1180
1490(11) 1580
1440(11) 1610
1580(11) 1590
1150(11) 1110
1330(12) 1370
1430(12) 1410
1630(12) 1660
1350(12) 1300
1650(11) 1680
1860 1890
2020 1910
1830 1710
1720(12) 1690
1640 1640
1640(11) 1600
1530(11) 1530
of Sample*
20
1260
1320
1370
1280
1180
1240
1210
1200
1310
1290
1320
1240
1160
1280
1180
1170
1600
1610
1550
1490
1410
1400
1560
1320
1490
1850
1830
1670
1690
1580
1550
1460
(ft)
25
1220
1310
1290
1300
1170
1230
1200
1160
1300
1300
1300
1220
1210
1230
1170
1150
1600
1610
1580
1490
1470
1390
1590
1310
1650
1860
1870
1680
1510
1590
1540
1440
30 35
1230 1660(33)
1390 1360(33)
1280 1320(33)
1300 1290(33)
1140 1170(34)
1220 1210(34)
1190 1240(34)
1160 1190(34)
1260 1260(31)
1300
1290 1280(31)
1240 1210(31)
1140 1170(31)
1240 1230(32)
1150 1170(32)
1170 1160(32)
1600
1630(28)
1570(28)
1480(28)
1410(29)
1450(29)
1700(29)
1460(29)
1960
2160
1960
2000
1870
1930
1940
1500
263
-------
Table 47- Continued
Depth of Sample* (ft)
Date
5
10
15
20
25
30
35
1E54-728
May 18
June 5
June 18
July 12
Aug. 24
Sept. 1
Sept. 9
Sept. 16
2430(7)
2240(7)
2210(8)
2100(7)
1850(7)
1750(8)
1760(8)
2250
2310
2270
2160
1970
1790
1760
1760
2250
2280
2230
2250
1970
1800
1740
1760
2340
2290
2240
2140
2020
1840
1750
1800
2430
2350
2270
2270
2100
1900
1840 '
1850
4W10-745
May 19
June 4
June 18
July 12
Aug. 24
Sept. 1
Sept. 9
Sept. 16
1570(7)
1530(8)
1400(8)
1490(8)
1410(8)
1370(8)
1670
1860
1580
1510
1410
1400
1380
1360
1600
1760
1570
1500
1380
1420
1370
1360
1600
1720
1540
1530
1300
1450
1390
1350
1500
1610
1460
1470
1370
1400
1320
1360
1630
1640
1600
1620
1480
1560
1370
1370
6W121-738
May 19
June 4
June 18
July 12
Aug. 17
Aug. 25
Sept. 1
Sept. 9
Sept. 16
1550
1600
1440
1430
1360
1405
1370
1350
1260
1540
1520
1430
1370
1340
1340
1330
1250
1550
1530
1410
1380
1350
1310
1330
1250
1560
1520
1440
1360
1370
1370
1330
1240
1610
1560
1420
1370
1370
1380
1320
1260
1490(31)
1440(31)
1370(31)
1350(31)
6W14 7-331
May 19
June 4
June 18
July 13
Aug. 19
Sept. 1
Sept. 9
1520(7)
1390(7)
1460(7)
1410(7)
1350(8)
1440
1460
1350
1450
1430
1350
1310
1400
1450
1360
1430
1360
1340
1290
1410
1450
1370
1440
1350
1320
1320
1420
1460
1350
1440
1370
1360
1350
1410
1440
1350
1430
1350
1370
1420
1440(33)
1360(33)
1440(33)
1350(34)
1340(34)
*Numbers in parentheses indicate actual depth at which sample was taken
if different from nominal depth indicated in column heading.
264
-------
Table 48. Field measurements of EC (ymhos/cm) of groundwater samples
from selected piezometers.
Piezometer Depth (ft)
Date
6E5-400
Aug. 20
Aug. 23
Aug. 25
Aug. 30
Sept. 8
Sept. 15
Sept. 28
6E20-400
Aug. 20
Aug. 23
Aug. 25
Aug. 30
Sept. 8
Sept. 15
Sept. 28
6E50-400
Aug. 20
Aug. 23
Aug. 25
Aug. 30
Sept. 8
Sept. 15
Sept. 28
6E100-400
Aug. 20
Aug. 23
Aug. 25
Aug. 30
Sept. 8
Sept. 15
Sept. 28
12
450
960
1360
1300
1230
1160
1120
650
1270
1410
1350
1260
1240
1200
260
1140
1110
1180
1190
1100
1040
1020
1330
1230
1420
1360
1350
1260
9
400
1670
1780
1660
1650
1630
1450
990
1630
1780
1810
1780
1690
1610
970
1500
1550
1560
1470
1500
1310
1020
1570
1590
1500
1440
1450
1330
6
1460
1640
1660
1600
1290
1400
1460
1320
1670
1730
1760
1650
1700
1380
1220
1640
1630
1560
1270
1540
1730
1350
1680
1750
1680
1690
1590
1500
Date
5W175-400
Aug. 20
Aug. 23
Aug. 25
Aug. 30
Sept. 8
Sept. 15
Sept. 28
5W100-400
Aug. 20
Aug. 23
Aug. 25
Aug. 30
Sept. 8
Sept. 15
Sept. 28
5W20-400
Aug. 20
Aug. 23
Aug. 25
Aug. 30
Sept. 8
Sept. 15
Sept. 28
5W5-400
Aug. 20
Aug. 23
Aug. 25
Aug. 30
Sept. 8
Sept. 15
Sept. 28
Piezometer Depth (ft)
12
120
1200
1220
1140
1300
1110
1090
880
1280
1320
1370
1230
1320
1220
680
1170
1220
1380
1320
1230
1140
290
860
1270
1160
1100
1100
1020
Q
160
1170
1350
1220
1210
1160
1060
580
1310
1480
1390
1310
1300
1270
630
1430
1530
1470
1440
1390
1290
960
1460
1520
1500
1400
1400
1360
6
1280
1500
1590
1580
1470
1420
1660
1210
1570
1650
1570
1560
1470
1390
1200
1500
1670
1640
1590
1500
1420
1240
1610
1700
1630
1540
1500
1370
265
-------
Table 48. Continued
Piezometer Depth (ft)
Date
5E5 -400
Aug. 18
Aug. 23
Aug. 25
Aug. 30
Sept. 8
Sept. 15
Sept. 28
5E20-400
Aug. 18
Aug. 23
Aug. 25
Aug. 30
Sept. 8
Sept. 15
Sept. 28
4W100-400
Aug. 18
Aug. 23
Aug. 25
Aug. 30
Sept. 8
Sept. 15
Sept. 28
4W20-400
Aug. 18
Aug. 23
Aug. 25
Aug. 30
Sept. 8
Sept. 15
Sept. 28
12
850
660
1040
1180
1110
1140
1060
700
1113
1300
1230
1230
1210
1080
380
1140
1320
1160
1150
1110
980
800
1280
1300
1320
1160
1250
1060
y
1110
1240
1430
1450
1350
1320
1180
750
1340
1400
1360
1400
1310
1230
970
1430
1440
1440
1380
1350
1270
890
1310
1350
1440
1260
1360
1100
6
1260
1460
1470
1470
1430
1350
1300
1160
1450
1550
1470
1480
1410
1280
1220
1390
1470
1470
1330
1370
1290
1190
1470
1490
1490
1450
1390
1480
Date
4W5-400
Aug. 18
Aug. 23
Aug. 25
Aug. 30
Sept. 8
Sept. 15
Sept. 28
4E5-400
Aug. 18
Aug. 23
Aug. 25
Aug. 30
Sept. 8
Sept. 15
Sept. 28
4E20-400
Aug. 18
Aug. 23
Aug. 25
Aug. 30
Sept. 8
Sept. 15
Sept. 28
3W100-400
Aug. 18
3W20-400
Aug. 18
3W5-400
Aug . 18
Piezometer Depth (ft)
12
930
1330
1320
1340
1340
1250
1100
970
1280
1280
1340
1390
1220
1060
930
1240
1100
1260
1120
950
990
440
1030
1530
9
1060
1340
1340
1370
1440
1340
1180
370
1240
1350
1420
1440
1190
1040
690
1390
1390
1640
1440
1250
1100
1240
1830
470
6
1150
1520
1500
1540
1530
1390
1400
1060
1370
1430
1440
1360
1140
1140
1280
1460
1410
1470
1440
1320
1440
1650
870
1490
266
-------
Table 48. Continued
Piezometer Depth ift) Piezometer Depth (ft)
Date 12 9 6 Date 12 9 6
3E5-400
Aug. 18 860 1680
3E20-400
Aug. 18 1060 620 1830
3E50-400
Aug. 18 1290 1270 2070
267
-------
Table 49. Average values of transmissability, T, hydraulic conductivity,
K, specific yield, V, and a from constant discharge test.
a = T/V.
Depth of
Piezometer
in ft.
6
9
12
T
(ft /sec)
9. 48 (lO"3)
9.53(10"3)
10.65(10"3)
K
(in/hr)
13.20
13.30
15.10
a
(ft2/sec)
4.6 (10~2)
4.05(10"2)
3.88(10~2)
V
(%)
20.1
23.5
27.4
Table 50. Values of hydraulic conductivity, K, by auger-hole method and
corresponding specific yield, V, from Figure 7 of Dumm (1968),
Location
6E40-150
6E50-270
6W50-410
6E40-500
6W50-660
1st stage
K(in/hr)
3.42
6.35
10.05
4.17
3.12
test
V (%)
16.0
19.0
22.0
17.0
15.6
2nd stage
K (in/hr)
6.70
5.00
4.95
3.35
7.90
test
V (%)
20.0
18.0
18.0
16.0
20.0
268
-------
Table 51. Soil properties used for computations made. Mesa sandy clay
loam soil.
Water Content
e
.00
.01
'• .02
.03 ,
.04
.05
.06
.07
.08
.09
.10
.11
.12
.13
.14
.15
.16
.17
.18
.19
.20
Hydraulic
Conductivity,
K (cm/hr)
1.0
2.0
3.4
1.0
1.7
3.0
5.4
9.2
1.6
2.7
• 4.8
7.5
1.5
2.5
4.5
8.7
1.4
2.5
4.5
7.5
1.1
do'9)
(10~9)
do"9)
do"8)
do"8)
do"8)
(10 )
(10 )
(10 )
do"7)
do"7)
do"7)
do"7)
do"6)
do"6)
(10 )
(10 )
do"5)
do"5)
do"5)
do"4)
Pressure Head,
h (cm)
-2
-1.3
-8.5
-4.2
-2.2
-1.15
-5.8
-3.0
-1.5
-1.1
-8.0
-6.2
-4.9
-4.0
-3.0
-2.35
-1.85
-1.45
-1.12
-8.7
-6.7
do6)
do6)
do5)
do5)
do5)
do5)
do4)
do4)
do4)
do4)
do3)
do3)
do3)
do3)
do3)
do3)
do3)
do3)
do3)
do3)
do2)
269
-------
Table 51. Continued
Water Content
e
.21
.22
.23
.24
.25
.26
.27
.28
.29
.30
.31
.32
.33
.34
.35
.36
.37
.38
.39
.40
.41
.42
Hydraulic
Conductivity,
K (cm/hr)
1.7 (10~4)
2.7 (10~4)
4.0 (10~4)
6.1 (10~4)
9.5 (10~4)
1.5 (10"3)
2.4 (10~3)
3.5 (10~3)
5.5 (10~3)
9.0 (10~3)
1.4 (10~2)
2.1 (10~2)
2.8 (10~2)
3.5 (10~2)
4.6 (10"2)
6.0 (10~2)
7.9 (10~2)
1.0 (10"1)
1.3 (10"1)
1.7 (10"1)
2.3 (10"1)
3.1 (10"1)
Pressure Head,
h (cm)
-5.3 (102)
-4.1 (102)
-3.2 (102)
-2.5 (102)
-2.0 (102)
-1.65 (102)
-1.35 (102)
-1.15 (102)
-9.9 (10)
-8.5 (10)
-7.4 (10)
-5.5 (10)
-5.6 (10)
-4.8 (10)
-4.5 (10)
-4.1 (10)
-3.8 (10)
-3.4 (10)
-3.112(10)
-2.731(10)
-2.413(10)
-2.096(10)
270
-------
Table 51. Continued
Hydraulic
Water Content Conductivity, Pressure Head,
8 K (cra/hr) h (cm)
.43 4.1 (10'1) -1.715(10)
.44 5.4 (ICf1) -1.335(10)
.45 6.9 (lO"1) -1.016(10)
.46 8.8 (lO"1) -6.985
.47 1.03 -3.175
.48 1.30 - .0000
271
-------
Table 52. Root distribution (RDF), salt content (SE) for alfalfa in 1971
and initial water content for alfalfa crop 1 (6-), crop 2 (0 ),
crop 3 (0_) versus depth used for the computations made.
Depth
(cm)
0
1
3
5
8
12
16
20
25
30
35
40
45
55
70
85
100
115
135
155
165
RDF
.0000
.0280
.0560
.0560
.0840
.1118
.1042
.0766
.0967
.0967
.0637
.0633
.0633
.0666
.0344
.0000
.0000
.0000
.0000
.0000
.0000
SE
(mmho/cm)
.000
.475
.505
.5113
.5200
.5325
1.0000
1.3500
1.7750
2.2000
2.6250
3.0250
3.4620
3.1750
2.7250
2.4000
2.1000
1.8000
1.4120
1.0500
.6250
•x
.080
.085
.090
.095
.100
.110
.120
.130
.144
.155
.195
.225
.265
.267
.268
.273
.275
.285
.305
.365
.400
92
.180
.180
.181
.183
\185
.189
.1915
.195
.198
.202
.215
.230
.245
.244
.240
.265
.285
.301
.326
.370
.400
63
.242
.2425
.2435
.2445
.2455
.2465
.2475
.2485
.2500
.2520
.2600
.2680
.2760
.2740
.2675
.2740
.2870
.3175
.3780
.4035
.4140
272
-------
Table 53. Root distribution (RDF), assumed for oats in 1970 with initial
electrical conductivity (SE), and initial water content (6 )
versus depth.
Soil Depth
(cm)
0
1
3
5
8
12
16
20
25
30
35
40
45
55
70
85
100
115
135
155
165
RDF
.000
.036
.073
.073
.109
.145
.145
.146
.182
.091
.000
.000
.000
.000
.000
.000
.000
.000
.000
.000
.000
SE
(mmho/cm)
.0
.5
.5
.5
.5
.5
1.0
1.4
1.8
2.2
2.6
3.0
3.5
3.1
2.7
2.4
2.1
1.8
1.4
1.0
.6
0
0
.040
.041
.045
.050
.055
.064
.072
.080
.090
.100
.143
.190
.238
.245
.256
.270
.285
.315
.370
.433
.463
273
-------
Table 54. Flux at the surface for alfalfa in 1971, evapotranspiration
(ET) , soil surface flux (W) , positive values are precipita-
tion, negative values are evaporation, and salt concentration
(SF) versus time.
Time Interval
hours
0 -
25 -
52 -
55 -
74 -
75 -
98 -
122 -
169 -
193 -
196 -
220 -
223 -
242 -
290 -
313 -
337 -
414 -
457 -
482 -
25
52
55
74
75
98
122
169
193
196
220
223
242
290
313
337
414
457
482
487
ET
cm/hr
Crop 1
-.336 (10"1)
-.25 (10~2)
-.000
-.41 (10~2)
-.000
-.43 (10~2)
-.20 (10"1)
-.175 (10""1)
-.30 (lO""1)
-.000
-.40 (10"~4)
.000
-.50 (10~3)
-.254 (10"1)
-.139 (10"1)
.000
-.2766(10"1)
-.145 (10"1)
-.96 (10~2)
.000
WF
cm/hr
-.336 (10~2)
-.25 (10~3)
.5433
-.41 (10~3)
.20
-.43 (10~3)
-.20 (10~2)
-.175 (10~2)
-.30 (10~2)
.59
-.40 (10"4)
.5233
-.50 (10~4)
-.254 (10~2)
-.139 (10~2)
.1162
-.2766(10"2)
-.145 (10~2)
-.96 (10~3)
.598
SF
mmho/cm
.000
.000
.635
.000
.000
.000
.000
.000
.000
.635
.000
.635
.000
.000
.000
.000
.000
.000
.000
.635
274
-------
Table 54. Continued
Time Interval
hours
487
530
626
648
657
672
698
722
793
868
919
920
0
22
48
73
96
120
157
169
187
- 530
- 626
- 648
- 657
- 672
- 698
- 722
- 793
- 868
- 919
- 920
- 938
- 22
- 48
- 73
- 96
- 120
- 157
- 169
- 187
- 216
ET
cm/hr
-.375
-.192
-.72
.000
-.193
-.326
-.154
-.241
-.224
-.320
.000
-.30
-.246
-.181
-.146
.000
-.134
-.141
.000
.000
-.177
(10 2)
do'1)
CIO'2)
CIO'1)
CIO'1)
Cio"1)
Cio-2)
do"1)
CIO'2)
Cio-1)
Crop 2
do'1)
do"1)
do"1)
do"1)
do"1)
do"1)
WF
cm/hr
-.375
-.192
-.72
.5366
-.193
-.326
-.154
-.241
-.224
-.320
.030
-.30
-.246
-.181
-.146
.565
-.134
-.141
.5041
.015
-.177
do'3)
do'2)
(10~3)
CIO'2)
CIO'2)
CIO'2)
do"2)
do'2)
do'2)
CIO"2)
do"2)
do"2)
do"2)
do"2)
do"2)
do"2)
do"2)
SF
mmho/cm
.000
.000
.000
.635
.000
.000
.000
.000
.000
.000
.000
.000
.000
.000
.000
.000
.000
.000
.635
.000
.000
275
-------
Table 54. Continued
Time Interval
hours
216
241
288
408
417
429
456
504
528
576
626
648
671
683
719
769
816
817
865
889
893
912
- 241
- 288
- 408
- 417
- 429
- 456
- 504
- 528
- 576
- 626
- 648
- 671
- 683
- 719
- 769
- 816
- 817
- 865
- 889
- 893
- 912
- 963
ET
cm/hr
-.249
-.30
-.275
-.749
.000
-.281
-.383
-.289
-.241
-.251
.000
.000
.000
.000
-.234
-.259
.000
-.264
-.323
.000
-.456
-.277
ao-1)
ao-1)
ao-1)
ao-1)
ao-1)
ao-1)
ao-1)
ao-1)
ao-1)
ao-1)
ao-1)
ao-1)
ao-1)
ao-1)
ao"1)
WF
cm/hr
-.249
-.30
-.275
-.749
.5608
-.281
-.383
-.289
-.241
-.251
.363
.435
.6033
.000
-.234
-.259
.03
-.264
-.323
.6425
-.456
-.277
ao-2)
ao-2)
ao-2)
ao-2)
-
ao-2)
ao-2)
ao-2)
ao-2)
ao-2)
ao"2)
ao-2)
ao-2)
ao-2)
ao-2)
(io~2)
do"2)
do'2)
SF
mmho/cm
.000
.000
.000
.000
.635
.000
.000
.000
.000
.000
.000
.000
1.775
.000
.000
.000
.000
.000
.000
.635
.000
.000
276
-------
Table 54. Continued
Time Interval
hours
963
0
24
48
144
240
312
328
336
360
480
552
612
627
696
698
768
792
816
840
864
888
- 1005
- 24
- 48
- 144
- 240
- 312
- 328
- 336
- 360
- 480
- 552
- 612
- 627
- 696
- 698
- 768
- 792
- 816
- 840
- 864
- 888
- 915
ET
cm/hr
-.226 (10"1)
Crop 3
-.625 (10~2)
-.127 (10"1)
-.142 (10"1)
-.243 (10"1)
-.30 (10"1)
.000
.000
-.211 (10"1)
-.187 (10"1)
-.135 (10"1)
-.219 (10"1)
.000
-.224 (10"1)
.000
-.190 (10"1)
.000
-226 (10"1)
.000
-.227 (10"1)
-.198 (10"1)
-.191 (10"1)
WF
cm/hr
-.226 (10~2)
-.625 (10~3)
-.127 (10~2)
-.142 (10~2)
-.243 (10~2)
-.30 (10~2)
.6362
.000
-.211 (10~2)
-.187 (10~2)
-.135 (10~2)
-.219 (10~2)
.6166
-.224 (10~2)
.37
-.190 (10~2)
.0021
-.226 (10~2)
.0504
-.227 (10~2)
-.198 (10~2)
-.191 (lO'1)
SF
mmho/cm
.000
.000
.000
.000
.000
.000
1.0920
.000
.000
.000
.000
.000
.839
.000
.000
.000
.000
.000
.000
.000
.000
.000
277
-------
Table 55. Measured bulk density, water content, electrical conductivity, and ion concentration
profiles for conditions of Case #1.
00
Depth
(cm)
0 -
5.1 -
10.2 -
15.2 -
20.3 -
25.4 -
30.5 -
35.6 -
40.6 -
45.7 -
50.8 -
55.9 -
Bulk
Density
5.1
10.2
15.2
20.3
25.4
30.5
35.6
40.6
45.7
50.8
55.9
61.0
1.15
1.16
1.20
1.19
1.19
1.21
1.17
1.14
1.17
1.14
1.15
1.15
Water
Content
(6)
0.346
0.353
0.353
0.350
0.348
0.340
0.331
0.332
0.326
0.322
0.300
0.281
Total
EC Salts
(ymho/cm) (meq/1)
866
744
852
1100
2410
3162
3448
5440
6000
7190
6524
13840
9.3
8.5
11.9
12.4
24.4
29.8
38.8
58.8
79.1
94.2
90.2
167.3
Calcium
(meq/1)
4.4
4.3
4.4
4.6
9.0
10.9
14.1
21.0
27.5
31.5
30.6
41.9
Magnesium
(meq/1)
2.9
2.6
4.4
6.0
13.1
16.5
21.8
34.4
46.9
56.3
53.8
114.9
Sodium
(meq/1)
2.0
1.7
3.2
1.7
2.3
2.5
2.9
3.4
4.7
6.5
5.8
10.5
Chloride
(meq/1)
0.6
0.3
0.3
1.5
16.1
23.6
24.6
46.7
52.9
64.3
52.6
144.0
-------
Table 56. Measured bulk density, water content, electrical conductivity, and ion concentration
profiles for conditions of Case #2.
Depth
(cm)
0
5.1
10,2
15.2
20.3
25.4
30.5
35.6
40.6
45.7
50.8
55.9
- 5.1
- 10.2
- 15.2
- 20.3
- 25.4
- 30.5
- 35.6
- 40.6
- 45.7
- 50.8
- 55.9
- 61.0
Bulk
Density
1.10
1.12
1.15
1.15
1.15
1.10
1.22
1.18
1.15
1.12
1.13
1.13
Water
Content
(6)
0.397
0.386
0.405
0.40
0.377
0.267
0.396
0.397
0.385
0.370
0.359
0.324
Total
EC Salts
(Vimho/cm) (meq/1)
379
552
1894
6612
8064
6480
4836
12031
8252
10186
9590
9230
4.4
6.4
26.2
84.3
98.2
61.2
43.6
142.2
75.9
125.0
90.1
115.3
Calcium
(meq/1)
1.6
2.6
12.3
36.3
45.0
29.4
20.6
61.9
39.4
62.5
47.4
59.1
Magnesium
(meq/1)
0.6
1.1
8.9
26.7
38.3
23.5
16.4
52.1
26.7
54.2
35.4
49.6
Sodium
(meq/1)
2.2
2.7
5.0
11.4
14.9
8.3
6.6
28.3
9.9
8.3
7.3
6.6
Chloride
(meq/1)
0.2
0.3
7.3
54.3
82.5
47.5
22.0
87.8
68.0
104.0
86.5
81.8
-------
Table 57. Measured bulk density, water content, electrical conductivity, and ion concentration
profiles for conditions of Case #3.
Depth
(cm)
0 -
5.1 -
10.2 -
15.2 -
20-3 -
00
0 25.4 -
30.5 -
35.6 -
40.6 -
45.7 -
50.8 -
55.9 -
Bulk
Density
5.1
10.2
15.2
20.3
25.4
30.5
35.6
40.6
45.7
50.8
55.9
61.0
1.11
1.13
1.12
1.16
1.16
1.16
1.18
1.16
1.14
1.17
1.17
1.16
Water
Content
(6)
0.376
0.388
0.376
0.394
0.412
0.404
0.416
0.419
0.418
0.419
0.451
0.473
Total
EC Salts
(ymho/cm) (meq/1)
1408
6090
11040
7372
6532
5745
5320
6128
7380
10653
11610
9379
20.8
77.0
128.2
76.5
78.0
63.2
61.4
70.9
83.0
121.9
126.4
111.4
Calcium
-------
Table 58. Chemical analyses of saturation extract for field experiment.
00
Depth
(cm)
0 -
30 -
60 -
90 -
0 -
30 -
60 -
90 -
0 -
30 -
60 -
90 -
30
60
90
120
30
60
90
120
30
60
90
120
EC
(ymho/cm)
3281
6952
2941
3178
4571
6996
4562
3670
6468
8981
7260
4462
Total
Salts
(meq/1)
42.9
72.9
41.4
46.0
59.1
70.6
48.1
47.9
73.0
88.6
73.6
52.8
Calcium
(meq/1)
(a) 324 hours
18.5
32.4
12.8
16.3
(b) 329 hours
12.3
22.5
14.9
14.3
(c) 627 hours
21.1
46.7
34.1
30.6
Magnesium
(meq/1)
11.3
41.1
22.4
23.9
6.9
41.7
26.5
27.2
6.7
33.2
34.8
17.7
Sodium
(meq/1)
13.1
8.4
6.3
5.9
40.0
6.4
6.6
6.4
45.2
8.7
4.8
4.6
Chloride
(meq/1)
16.2
57.6
3.7
0.4
14.1
51.9
13.8
2.5
40.2
78.1
53.3
16.4
-------
Table 59. Water content (9) profiles for salt flow field experiment,
Depth
(cm)
30
45
75
105
135
165
Table 60.
Depth
(cm)
15
45
75
105
135
165
24 hrs
0.20
0.24
0.25
0.29
0.38
0.41
40
0.
0.
0.
0.
0.
0.
Time
hrs 324 hrs
32 0.24
32 0.28
32 0.27
33 0.31
40 0.39
42 0.42
339 hrs
0.32
0.33
0.33
0.34
0.40
0:42
Electrical conductivity (ymho/cm) profiles at the
content for the salt flow field experiment.
24 hrs
—
3369
4068
3111
3426
2671
48 hrs
4082
33657
4252
6686
3279
2820
Time
76 hrs 324 hrs 327 hrs
3740 6915
32422 15070
13877 7032
6382 3930
3012 3372
2765 2654
8747
14745
7175
4410
3594
2700
627 hrs
0.28
0.29
0.28
0.31
0.39
0.41
field water
627 hrs
8883
14350
9285
4756
4373
2622
282
-------
Figure 56. Hydrograph of discharge from drain 4 during 1971,
283
-------
<*>
««—•
u
CD
O>
at
5
Figure 57. Hydrograph of discharge from drain 5 during 1971.
284
-------
.05
o>
u.
o
-—,r-
-t-
1O 13 ^i ^ 2 r>
JUNE.
Figure 58. Hydrograph of discharge from drain 3 during 1971,
Figure 59. Hydrograph of discharge from drain 6 during 1971,
285
-------
water applied
,40
tVJ
oo
^'
UI
o
c/> 5
cO
CC
£
o
z
I
o
-------
-.60
oo
-J
u
o
V)
-------
4)
b
water applied
40
30
ts)
oo
oo
io
OB 8
in
4)
O
1
I4
UJ
0
salt existing
20 1
a
UJ
_j
a.
a.
ac
UJ
10
leaching water
.salt leaving
10
INTERVAL BETWEEN IRRIGATIONS (days)
Figure 62. Season total results for problem ACH.
15
20
-------
oo
25
u
s
§20
b
CD
u
(E
UJ
I
10
o
z
. salt leaving
5 10 15
INTERVAL BETWEEN IRRIGATIONS Idays)
20
60
50
40 £
-C
o
C
O
UJ
30
20
10
or
UJ
0
Figure 63. Season total results for problem BCH.
-------
15
(A
I
"0
cO
U
c
tr
UJ
I
•
o
<
UJ
water applied
salt existing
leaching water
•salt leaving
INTERVAL
10
BETWEEN
J_
IRRIGATIONS
15
(days)
Figure 64. Season total results for problem ACL
60
50
40-
30 S
a.
a.
20
UJ
10
20
-------
60
vO
50
in
o40
oo
OL
Lu)
10
3 10 15
INTERVAL BETWEEN IRRIGATIONS (days)
90
80
70
60
50 2
u
40 §
a.
a.
a:
UJ
30
20
20
Figure 65. Season total results for problem BCI.
-------
water applied-
40
vO
u
o
b
<
V)
t
oo
in
-------
water applied-
50
40
IN)
vO
U)
-520
b
o
l5
"u!
I '°
-------
water applied
6
u
o
\
1 5
(0 4
o>
-C
o
tr 3
UJ
•salt existing
leaching water
salt leaving
5 10
INTERVAL BETWEEN IRRIGATIONS (days)
15
Figure 68. Season total results for problem ADG.
30
M
a>
o
20
o
UJ
a!
-------
20
cD
0>
O
- 10
a:
LU
I
Z e
I °
•salt leaving
n60
50
o
c
30 Q
UJ
20
a:
UJ
10
0
10
INTERVAL BETWEEN IRRIGATIONS (days)
15
20
Figure 69. Season total results for problem BDG.
-------
T40
water applied
IN)
vD
Q)
JU
c
o
CO
IS
o
c
cr
ui
|
o
<
UJ
0
salt existing
salt leaving
5 10 15
INTERVAL BETWEEN IRRIGATIONS Idays)
Figure 70. Season total results for problem ADH.
20
30
o
20 S.
Q
UJ
_J
Q.
Q.
o:
UJ
g
10
-------
tV)
b
CD
10
o
ffi
I
tu
-I 5
salt existing
leaching water
salt leaving
JL
J.
60
50
U
O
UJ
(E
UJ
20 I
5
INTERVAL
BETWEEN
Figure 71. Season total results for problem BDH.
10
IRRIGATIONS
15
(days)
20
-------
sD
00
INTERVAL BETWEEN IRRIGATIONS (days)
Figure 72. Season total results for problem ADI.
-------
60 r
£50
40
<0
UJ
I
o
z
i
o
<
Ul
30
10 -
10
10
INTERVAL BETWEEN IRRIGATIONS(days)
Figure 73. Season total results for problem BDL
80
70
60
50 -3
0)
40 §
a.
a.
30
-------
-.40
U)
o
o
I 6
o
<
V)
-------
25
•20
o
§
15
CO
o
— 10
IT
UJ
I
CJ
I5
UJ
salt existing
5 10
INTERVAL BETWEEN IRRIGATIONS (days)
15
20
n60
50
40,
£
JZ
u
30
a
UJ
_i
a.
a.
20
tr
UJ
10
Figure 75. Season total results for problem BEF.
-------
water applied
oo
o
"5 6
u
(A
I 5
-a 4
-C
u
ffi
I3
O
UI
0
salt leaving
5 10
INTERVAL BETWEEN IRRIGATIONS (days)
Figure 76. Season total results for problem AEG.
15
30
CO
20
o
UJ
a!
0.
a:
UJ
I
10
20
-------
CO
O
CO
2or
o
o
cD
10
o
s.
oc.
UJ
s.
water applied
leaching water
salt existing
salt leaving
5 10
INTERVAL BETWEEN IRRIGATIONS (days)
15
20
60
50
40
I
•30
o
UJ
_j
a.
a.
20
cr
LU
I
O
Figure 77. Season total results for problem BEG.
-------
OO
o
-> 6
-------
25r
OJ
o
on
b
05
tr
ui
I
15
10
o
z
5
a
salt leaving
5 10
INTERVAL BETWEEN IRRIGATIONS
Figure 79. Season total results for problem BEH.
Ways)
15
160
50
40
M
«
a
UJ
cr
UJ
20
-------
OJ
o
16
I4L
I*12
o
!
~io
b
a
05
8
(t
LU
I
salt leaving
5 10
INTERVAL BETWEEN IRRIGATIONS (days)
15
20
|60
50
V)
d>
40-=
o
UJ
20
10
Figure 80. Season total results for problem AEI.
-------
.-•-91.27
6Or
O
s
OJ
o
90
10 15
INTERVAL BETWE1N IRRIGATIONS (days)
20
Figure 81. Season total results for problem BEL
-------
SELECTED WATER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
W
IRRIGATION MANAGEMENT FOR CONTROL OF QUALITY
OF IRRIGATION RETURN FLOW,
King. L.G. and Hanks, R.J.
Utah State University, Logan, Department of
Agricultural and Irrig .tion Engineering
EPA 13030 FDJ
EPA 13030 FDJ
Environmental Protection Agency report number,
EPA-R2-73-265, June 1973.
Field studies tested the possibilities for using the unsaturated soil profile
including the crop root zone as a temporary salt reservoir and providing excess water for
leaching and salt discharge when desired. Two models were developed for describing flow
of water and salt through the soil with extraction of water by evapotranspiration. One
model was designed for use as an irrigation management tool while the other model was
initially intended to provide a detailed understanding of the water and salt flow through
the soil. The best management model will probably result from a combination of the two
models described in this report. Timing of irrigation was tested as a management vari-
able. With all other conditions the same, the model predicts that as the time interval
between irrigations increases, the season totals of salt removed from the root zone,
salt remaining in the profile, and water required for leaching tend to level off. How-
ever, the irrigation frequency has a significant effect upon when the salt is discharged
during the season. Results indicate that managing irrigation for control of return flow
quality requires good control of depth and timing of irrigation. Some needs for further
research are given in the report. (King-Utah State)
*Retum flow, *Leaching, *Salinity, *Irrigation practices, Colorado River Basin,
Environmental effects, Water quality, Irrigation, Drainage, Soil water, Management,
Drainage effects, Computer models
*Return flow quality, *0n-farm water management, *Salt storage, *Irrigation scheduling,
Salt movement, Irrigation frequency, Irrigation management, Field irrigation studies,
Ashley Valley, Vernal
02G, 05G
Send To:
WATER RESOURCES SCIENTIFIC INFORMATION CENTER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON, D.C." 2024O
Larrv G. King
Utah State University
------- |