WSP12324

• File Number: 8281.960
• Description: Colorado River Studies and Investigations -- Lower Colorado Comprehensive Framework Study
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 6/1/1971
• Title: Lower Colorado Region Comprehensive Framework Study -- Appendix XV - Water Quality - Pollution Control and Health Factors
• Water Supply Pro - Doc Type: Report/Study

o

!'.~' )

,
SUMMARY OF FINDINGS

'"'"
t-"
(.,)
00

Salini ty

High levels of dissolved mineral salts in surface and ground
waters is a major water quality problem in the Region. With
few exceptions, most surface and ground water supplies have
mineral concentrations exceeding 500 mg/l, and many exceed
1,000 mg/l. The salinity of the supplies affects domestic,
industrial and agricultural uses.

The Colorado River enters the Region at concentrations
exceeding 500 mg/l, varies between 500 and 900 mg/l at most
diversion points and increases to as high as 1150 mg/l for short
periods of, time at Imperial Dam. Nearly 8.7 million tons of
dissolved solids are transported into the Region from the Upper
Colorado Region annually. Increased salinity concentrations in
the Colorado River from Lee Ferry, Arizona to Imperial Dam are
due principally to inputs from saline springs and the concentrat-
ing effects of consumptive use, reservoir evaporation and diversions
out of the Region.

In the headwaters of the Gila River, dissolved solids
concentrations are generally less than 500 mg/l. In the middle
reaches below points of major diversions the dissolved solids
content usually range from about 500 to 1,000 mg/l. Although
there are some salt springs discharging to the Gila River, most
of the increase in dissolved solids result from the concentrat-
ing effects of consumptive uses.

I
I
,

Mineral quality is generally good in most of the headwaters
of the Little Colorado River. The middle reaches of the Little
Colorado vary considerably in salt content. The Little Colorado
River near its mouth is very high in dissolved solids as most of
the flow originates from saline springs.

Future dissolved solids concentrations in the lower Colorado
River were estimated for 1980, 2000, and 2020. Dissolved solids
concentrations in the Colorado River, assuming no salinity
improvement ,program are projected to increase 40 to 60 percent
by 2020. The major cause of the projected salinity increases
is due to increased development which includes the additional
stream depletions for municipal and industrial use, irrigation,
thermal-power production, exports, reservoir evaporation, and
the additional salts leached from newly irrigated lands.

State and federal representatives in both the Upper and Lower
Colorado Regions agreed that the salinity improvement programs
outlined in the Upper and Lower Colorado Framework Study documents
would be part of a basinwide approach to salinity management.
The program outlined in this appendix, therefore, is for that

i