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

7'able 8.J!4. Effective ValueB of Boil Baturation
ell:tract conductivitieB (Eee in mmhoB/
em) in tllree Boil drw.'Mge clasBeB, Beven
TDS levels, and five irrigation manage-
ment treatmentB.

1'\.")
CO
(f',)
00

TDS
(mg/I)

Irrigation
Number

860

16
22
29
35
Sprinkler

16
22
29
35
Sprinkler

16
22
29
35
Sprinkler

16
22
29
35
Sprinkler

16
22
29
35
Sprinkler

16
22
29
35
Sprinkler

16
22
29
35
Sprinkler

910

950

980

1020

1060

1100

Drainage Classification
Well Moderate Poor

0.3
0.3
0.3
0.3
0.0

0.4
0.4
0.4
0.4
0.0

0.6
0.6
0.6
0.6
0.0

0.6
0.6
0.6
0.6
0.0

0.7
0.7
0.7
0.7
0.0

0.8
0.8
0.8
0.8
0.0

0.9
0.9
0.9
0.9
0.0

1.8
1.2
1.0
0.6
0.0

2.0
1.4
1.4
0.7
0.0

2.2
1.6
1.3
0.9
0.1

2.3
1.6
1.4
0.9
0.1

2.5
1.9
1.6
1.1
0.3

2.7
1.9
1.7
1.2
0.4

2.9
2.1
1.8
1.3
0.5

4.1
3.5
3.2
2.8
1.7

4.4
3.8
3.5
3.1
2.2

4.7
4.0
3.7
3.3
2.4.

4.9
4.2
3.9
3.4
2.6

5.1
4.4
4.1
3.6
2.8

5.4
4.7
4.4
3.8
3.1

5.7
4.9
4.6
4.0
3.3

Base yields were derived from historical data
preaented in Table 8-181. These figures were used to
establish yield declination functions aceording to the
procedure described in preceding areas.

Once again, a computer run was made to
asslmulate conditiona of 775 mg/I as well as for the
higher mg/lsituations. Table 8-182 sh9wS the results.
^ slight variation is noted in production and land uae
of barley and maize but this movement is so small that
it can be safely assumed that these figures are
constant. Sub-Appendix N provides additionalinfor-
mation concerning allocation variationain technologies
and land classes which adequately explain the
occurrence in the table.

The relative marginal value products of the
varioua land classes are I!resented in Table 8-188. No
trenda are evident except for land class 8 under the

double cropping alternative. The values decline as
TDS rises indicating that crops grown under these
conditions suffer decreaseain yield due to unfavorable
economic trade offs for available yield maintaining
technologies.

An estimated 90,000 ac it of water will be
available to irrigators upon delivery of CAP water
under the assumptions outlined earlier. This amount
would provide a little more than 4 ac it per acre of
cropland. Table 8-134 shows the amount of water
allocated for agricultural purposes. Almost 100
percent of the total available supply is used.

It appears that within the TDS interval of 775 to
1400 mg/l additional increments of water will not be
required in the face of rising sa1inity in order to
maintain yields. In Table 8.185, net profits do decline
over the interval in question, however, the magnitude
is only a total of $224 which cannot be effectively
attributed to any single source. Model biases or errors
could well account for such a small amount of damage.
Consequently, within the limits of the TDS interval
for the present study, it was considered that
increasing salinity contributed no appreciable
amounts to costs in agriculture. Moreover, sizable
damages are not anticipated to be incurred until TDS
levels above 1400 mg/I are encountered. Therefore, as
was the case in the non-Indian portion ofthe district, a
damage function was not constructed for this area and
losses due to .alinity are considered as not to be
measurable within the confines of the analysis.

The summary statistics in Table 8-185 indicate
just how small of an effect on net profits would be
realized if a damage function had been construed.
Annual damages per mg/l per acre of $0.0000167
represent a cost of only $0.86 to the whole area of
21,170 acres for a 1 mg/l increase in the salinity
content of the irrigation water. Even a rise of 10 mg/I
would be very insignificant as far as increasing costs
to agriculture are concerned. Quite appropriately
then, it is assumed that damages due to poor quality
water within the TDS interval considered in the
present study are virtuaily nonexistent in this area.

.. REFERENCES

Adams, E.D. 1972. General.soil map Pinal County, Arizona.
USDA Soil Conservation Service in coope:ratlon with the Soll
Conservation Districts in Pinal County, 1971. (Revised AprD
19'/2)

Annual Crop, Production Reports, Roosevelt Water Conservation
Distriet.

Annual Crop Production Reports. g'alt River Project.

Babcock. H.M. 1973. ~nnual report on groundwa~r in Arizona.
Spring 11172 to Spring 11l78.Ar1zona Water Commis.loner
Bulletin 7 (Prepared by tbe USDI Geological Survey).

Bern.tein, L. 1962. Salt-affectod ..u. and plants. tD UNESCO
Paris SymPosium on the Problema of the Arid Zone. p.
189-174.

200