WSP06476

• File Number: 8271.300
• Description: Colorado River Basin Salinity Control Program - General Information and Publications-Reports
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 6/1/1978
• Title: Salinity Management Options for the Colorado River -- Part 1 of 2 -- Title Page - Page 168
• Water Supply Pro - Doc Type: Report/Study

0 Table ~8. Comparison of TIT IIaz and finoJ salt concentration for corn, aI,fa//a, and oats at various levels of water
C.;> appUctJtion and ini Balt concentration.
~
.....y Irrigation T/Tp Initial Final Salt Concentration
N and Salt meq/liter
<Xl Rain Concentration
em Corn Alfalfa Oats meq/liter Corn Alfalfa Oats
5.6 0.81 0.52 0.29 20 62 43 33
5.6 0.77 0.50 0.28 50 127 97 78
5.6 0.48 0.33 0.18 200 305 277 248
10.3 0.89 0.61 0.37 20 60 42 33
10.3 0.86 0.58 0.36 50 120 94 76
10.3 0.55 0.42 0.24 200 296 269 242
15.0 0.97 0.68 0.46 20 56 43 33
15.0 0.93 0.66 0.44 50 116 94 76
15.0 0.64 0.49 .0.32 200 296 268 242
22.0 0.98 0.80 0.59 20 40 41 43
22.0 0.98 0.78 0.58 50 95 92 76
22.0 0.78 0.63 0.46 200 291 263 240
40.8 0.99 1.00 0.89 20 27 30 26
40.8 0.98 1.00 0.88 50 64 64 58
40.8 0.97 0.93 0.80 200 227 228 208
56.4 1.00 1.00 0.97 20 23 24 24
56.4 1.00 1.00 0.93 50 50 52 52
56.4 1.00 1.00 0.93 200 189 195 185
66.7 1.00 1.00 0.99 20 20 20 22
66.7 1.00 1.00 0.99 50 42 44 43
66.7 1.00 1.00 0.99 200 153 158 157

levels, but there was a marked difference when the
concentration was 200 meq/l.

The results showing final salt concentration levels
indicate a buildup of salts in the soil proffie for each
crop until the water application roaches a high level.
This buildup could have serious effects on yields if it
were maintained over a long period of time. However,
at the 56.4 and 66.7 centimeter levels, salt is leached
from tbe soil and the buildup ceases.

The data in Table 29 also demonstrate the buildup
of salts that occurs in the lower four annual water
application rates. The drainage figures show an
upward flow of water until irrigation roaches 56.4
centimeters, especially for the longer. rooted corn and
alfalfa. The salt flow to groundwater figures show the
amount of salts in millequivalents that transfer from
tbe soil to the irrigation return flow. The negative
values in the lower water application rates indicate a
buildup of salts whicb occurs because of tbe
evapotranspiration process. At the two highest water
application levels, the values are positive 8Ild indicate
some transfer of salts from tbe soil into the roturn
flow.

The single point values relating water added to
the T /T are somewhat unrealistic in a real field
situation'b;,;use water is not distributed uniformly.
Even with the host irrigation system there are. parts

of the field that receive more water than others. To
account for this, a uniformity coefficient Cu has been
defined as follows:

Cu = 1.~
M

in which M is the average irrigation rate and D is tbe
average deviation (sign ignorod) about the average
irrigation rate. When Cu = 1, water application is
completely uniform. For the sprinkler irrigation
simulation the coefficient used in the model was equal
to 0.66. The value was 0.42 for flood irrigation. Tbe
values of T /~p and final salt concentration were
adjusted'for tnese variations in Cu to incroase the
accuracy of the model. The data showing the variation
of TITR will not be presented in this work but are
includell as part of the economic model.

The ~nomle Model

The economic model is designed to suggest ways
to maximize profits at various levels of salt outflow
from the farm operation. This is done through the use
of a linear programming procedure designed to
minimize the income 10S80S imposed by restraints on
the salt outflow from tbe irrigation roturn flow. It is
based on the physical model and on a set of coet and

28