WSP05341

• File Number: 8278.100
• Description: Title I - Yuma Desalting Plant
• Basin: Colorado Mainstem
• Date: 12/23/1992
• Author: USDOI/BOR
• Title: Yuma Desalting Plant - Alternatives for the Interim Period
• Water Supply Pro - Doc Type: Publication

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Full-scale operation, maintenance, and replacement (OM&R) expenses of
the Desalting Plant are expected to be $33.7 million per year,
recovering about 78,500 af of irrigation drainage. If the capital costs
foregone are not considered, the Desalting Plant recovers drainage water
at a unit cost of $429 per acre-foot. The operation of the Desalting
Plant is intended to allow poor quality drainage water from the WMIDD to
be conserved, returned to the river, and used to meet the United States
1944 Treaty commitments for the delivery of water to Mexico. Without
operation of the Desalting Plant, the poor quality irrigation drainage
would not be useable for meeting deliveries to Mexico under the 1944
Treaty and would have to be bypassed to the Slough, lost from use, and
would require additional releases from upstream reservoir storage.

The 1974 Act also authorized concrete lining of the first 49 miles of
the Coachella Canal to assist the Secretary in meeting salinity control
objectives. The conserved water made available by lining the canal
(about 132,000 af per year) is available to the United States to offset
the impact on reservoir storage of providing additional releases, in
lieu of using WMIDD drainage return flow, to meet the 1944 Treaty with
Mexico during the interim period. At the time of authorization, the
conserved water was intended by Congress to be used as a temporary
supply of water to be available as a replacement water supply while the
Desalting Plant was under construction and while water use in the Lower
Basin continued to be less than apportioned supplies.

The interim period of use of the conserved water began when canal lining
was completed in 1982 and shall end the first year that the Secretary
delivers mainstream Colorado River water to California water users in an
amount less than the sum of the quantities requested and the water is
thereby needed by California. Since water utilization by the Central
Arizona Project has not developed as projected, and reservoir storage
conditions are such that the reservoir system is likely to refill in the
near-term, the United States continues to be able to meet California
water requests. It appears, therefore, that the interim period will
continue for the next few years and possibly longer. As a result, the
United States continues to have temporary use of conserved water
supplies developed by lining the Coachella Canal for meeting the
1944 Treaty deliveries to Mexico.

Following a brief review of the history and a description of the works
authorized by the 1974 Act's Title I program, this report will present
five basic alternatives and several variations of these alternatives for
implementation during the interim period. Within the alternatives
section, the legal, institutional, and technical issues related to each
alternative will be developed and discussed. Measures that were
considered, but eliminated, are also presented.

HISTORY

In 1944, the United States and Mexico signed a Treaty requiring the
United States to deliver 1.5 million af of Colorado River water to
Mexico annually. The 1944 Treaty did not address water quality.
In 1961, the salinity of the delivered water increased sharply from a

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