WSP07589

• 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 2 of 2 -- Page 169 - End
• Water Supply Pro - Doc Type: Report/Study

Table 8-76. Yields of 'fTI4J'or C1'OP' in the Yuma Valley area, 1966-1978 (tons/acre).

196~ 1967 1968 1969 1970 95 Percen t
1971 1972 1973 Confidence
l\.) In terval
o:J Cotton 3.32 2.11 3.12 2.49 1.90 2.16 2.09 2.31 2.44 t 0.43a
'f Alfalfa 6.00 6.30 5.90 6.80 6.30 6.90 7.30 7.70 6.65 t 0.53
Lettuce 12.67 12.64 7.11 7.63 12.53 9.00 11.04 10.81 10.43 t 1.89
~.J Cantaloupe 5.32 4.75 4.94 570 5.70 8.50 8.10 6.40 6.18 t 1.18
Wheat 1.62 2.04 2.10 2.01 2.13 1.83 2.19 2.49 2.05 t 0.21
Sorghum 1.71 2.46 1.5.1 1.26 2.10 1.76 2.13 2.18 1.89 t 0.33
Grass Seed 9.00 7.30 8.20 6.50 4.80 5.80 5.90 7.80 6.91 t 1.18
Grapefrui t 1O.26b 16.88b .4.72 7.22b 11.91b 4.94 3.66 2.70 11.57 t 6.43
Oranges/Tangerines 7.87 6.67 N/A 11.51 10.64 6.84 5.78 6.31 7.95 t 2.07
Lemons 10.66 t2.83 6.11 5.57 5.26 8.90 t 4.27
a4SD-pound bales per acre.
bYie1ds considered to be representative of mature trees.
Source. U.S-. Bureau of Reclamation, Water and ,Lan.d Resourc_es Accomplishments, 1966-1973.

being profitable management alternatives. Partial
sprinkler, full sprinkler, and tiling were not selected.

Changes in the amounts of production and land
use are shown in Table 3.76. Alfalfa, grapefruit, and
lemons Jl,re the crops which have both a constant level
of production and a constant amount of acres used.

Lettuce, wheat, and sorghum have con~tant
levels of production throughout the TDS range. But as
yields decline. more land is required when the TDS
level increases. The most significant increase occurs in
lettuce at the 1300 and 1400 mg/l TDS levels.

An interesting trend develops in the case of
cotton, . grass seed, and oranges/tangerines. Both
production and land area decline. In the initial run,
cotton and oranges/tangerilles are produced at the
upper level while grass seed is a slack activity
(produced neither at the upper level nor the lower
level but somewhere in between). Grass seed
production and occupied land area decline until 1300
mg/I TDS is reached. At this level, grass seed has
declined to the lower level of the model and so
oranges/tangerines decrease in production and land
area. However, at 1400 mg/I TDS, the lower limit is
reached for oranges/tangerines and cotton incurs a
loss in production and land area. Redistribution of
these crops occurs due to declining yields of the
remaining crops and consequently, more land of better
drainage characteristics is required in order to meet
their production needs according to the model.

Cantaloupe demonstrates the same kind of
allocation pattern as in the previous analysis of the
Gila area. In maintaining a constant level of
production throughout the TDS range, first, land area
increases and then it decreases. For 900 to 1200 mg/I
TDS, increased land area is required to maintain a
constant level of production. At 1300 mg/l TDS,
relative economic trade oils between cantaloupe and
the other crops cause more cantaloupe production to
be allocated to better land classes. Previously,
production was placed on class 1, 2, and 3 lands. Now
the model assigned production to class 1 and 2 lands

reaching 1400 mg/I TDS, the model places most of the
production on class 1 land. Since a larger share of total
production is produced on higher yielding land at 1300
and 1400 mg/l TDS, less land is required, and thus a
constant production level can be maintained with
lower land use. For more details concerning the
interactions of the different crops at the various levels
of TDS refer to sub-Appendix H.

Table 3-77 contains the shadow prices of the
various land classes. In all land classes, the trend is
. toward higher relative values. Evidently demand for
the various land classes increased throughout the
range causing the values to increase. A significant
jump occurs between 1300 and 1400 mg/I TDS where,
for. example, the value of class 1 land increases from
$190 io $323. Similar jumps occur in the remaining
land classes. Double cropped land classes behave
somewhat differently and the reader is referred to
sub-Appendix H for a more detailed explanation.

The total water constraint established in the
model was 270,900 ac ft. This amount is the total
av~ilable for agricultural purposes. In Table 8.78, total
water consumption appears to be declining in a normal
trend until at 1300 and 1400 mg/I TDS sharp
decreases are. detected. This is explained by examin-
ing the trade offs occurring in cotton, grass seed, and
oranges/tangerines. At 1300 mg/I TDS, both land
area and production declined for the latter two crops.
Since these crops consume water almost year around,
large amounts are required as compared to a crop with
a shorter season. Due to the fact that less water is
needed for these two crops because of less production
and smaller occupied land area, overall total consump.
tion of water also declines. The same reasoning is
applied at the 1400 mg/I TDS level, but instead of
grass seed declining, cotton is the. crop which
undergoes a loss in production and land area. Along
with cotton, oranges/tangerines also decline which
precipitates another sharp decrease in the demand for
water.

Net profit as estimated by the ",odel objective
function coresponding to the different TDS levels, are

174