WSP06362

• File Number: 8210.470
• Description: Pacific Southwest Interagency Committee
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 11/1/1971
• Author: PSIAC
• Title: Pacific Southwest Analytical Summary Report on Water and Land Resources based on Framework Studies of Four Regions - November 1971
• Water Supply Pro - Doc Type: Report/Study

Water Quality

been shown to be feasible. Treatment of irrigation
drainage to remove nutrients is part of the California
Region base plan.
Two projects in the Lower Colorado Region and
about 10 projects in the Upper Colorado Region have
been identified and included in the plan as potential
means for salinity management. A variety of control
methods would be utilized, the most feasible .of
which would include impoundment and evaporation
of point source discharges, diversion of streams
a(ound areas of high salt pickup, irrigation practices
and facilities that would reduce return flow volumes,
desalting of saline discharges from natural and
manmade sources, and desalting of water supplies at
the point of use. The measures included, if placed in
operation in accordance with the framework plan,
would result in reductions in projected increase in
salinity at Lee Ferry and at Imperial Dam as shown
on figure 25.
Control of water quality in the major terminal
lakes within the Pacific Southwest has received some
attention in this study, but with one exception, the
maintenance of these terminal lakes or sinks is listed
under ''unmet needs," Pyramid and Walker Lakes in
Nevada will become more saline and will continue to
recede unless measures are developed to halt or
reverse the historic trend. Without costly protective
measures, degradation of the Salton Sea in California
will continue. The Great Salt Lake in Utah,
approximately six times the salinity of sea water, will
continue to recede.

Costs

The installation and annual operation and
maintenance costs of all programs for municipal
waste treatment and disposal facilities and the
Colorado River Basin salinity improvement program
are shown in figures 26, 27, 28,and 29.
The Federal contribution to the cost of
constructing eligible municipal waste treatment and
disposal facilities is assumed to be 55 percent. In the
absence of specific legislation, the costs of the
Colorado River Basin salinity improvement program
were assumed to be wholly a Federal obligation. This
assumption is advocated strongly by the State
participants. Many Federal participants were not
opposed in view of the lack of positive guides to this
involved problem, Other Federal participants, led by
the Envlronmenial Protection Agency, were opposed
to the assumption on the basis that it implied a
commitment on the part of the Federal Government
to bear the full program cost.

Conclusions

Conclusions concerning water quality problems of

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1965 1980 2000

Figure 26.-Munlcipal waste treatment facility installa.
tion costs.

the Pacific Southwest are that:
1. The most difficult and widespread water
quality problem of the Pacific Southwest is the
increasing salinity of the Colorado River.
Methods of treating irrigation drainage water to
control salinity have not yet been shown to be
feasible. Irrigation improvement projects may
reduce the discharges of salts into the Colorado
River system. However, it is projected that
timely installation of salinity control projects
can hold down the salinity at Imperial Dam to
1,030 mg/I in 2020. (In 1965 it was 840 mg/I;
without reduction measures it could rise to
1,350 mg/I by 2020 in the absense of aug-
mentation.)
2. To hold the salinity at Imperial Dam to 1,030
mgfl by 2020 will require salinity reducti?n
rile~sures be applied throughout the entire
Colorado River Basin.
3. Streamflow regulation for water quality control
could contribute significantly to maintaining