WSP04851

• File Number: 8282.600.10
• Description: Colorado River Operating Annual Reports
• Basin: Colorado Mainstem
• Date: 1/1/1988
• Author: USDOI/BOR
• Title: Operation of the Colorado River Basin 1988 Projected Operations 1989
• Water Supply Pro - Doc Type: Publication

Water Quality Operation

In 'recognizing the need to maDage the water quality of the
Colorado River, it was recommended that long-term salinity
increases in the river be controlled through a water quality
improvement program as described in the report
"Colorado River Water Quality Improvement Program'
dated February 1972. The program called for a basin-wide'
approach to salinity control while the Upper Basin continues
to develop its compact-apportioned waters. '

The initial step toward improvement of the future water
quality in the. basin was the passage by Congress in the
Colorado River Basin Salinity Control Act of 1974 (Act)
(Public Law 93-320) on June 24, 1974, authorizing the
construction of various features for the enhancement and
protection of the quality of water available' in the
Colorado River for use in the United States and the Republic
of Mexico.

Title I of the Act enables the United' States to comply with its
obligation under the agreement with Mexico of August 30,
1973 (Minute No. 242 of the International Boundary and
Water Commission, United States and Mexico), which was
concluded pursuant to the Treaty of February 3, 1944
(TS994). . TItle I authorized the construction of the Yuma
Desalting Plant and a bypass drain to ultimately discharge the
plant's brine. These facilities, and others, will enable tne
delivery of water at Morelos Dam, for subsequent use in
Mexico, having an average annual salinity no greater than
115 parts per million (ppm) plus or minus 30 ppm (United
States count) higher than the annual average salinity of the
Colorado River water at Imperial Dam.

Title n of the Act authorized the Secretary to construct a
number of wllts in the basin above Imperial Dam, as well as
the investigation of several other potential salinity control
units.

The Act, and its amendment by Public Law 98-569 of
October 30, 1985, directs the Secretary to submit a biennial
report to the President, the Congress, and the Colorado River
Basin Salinity Control Advisory Council. The water quality
aspects of Colorado River operations are extensively
described in that biennial series, the latest of which is Report
No. 13 entitled, "Quality of Water, Colorado River Basin,"
dated January 1987, only minimal discussion of this aspect of
the operation below Imperial Dam is presented in this report.

During all of water year 1988, the United States bypassed a
total of 97,000 acre-feet through the bypass drain near Yuma.
There were excess water conditions through February, 1988,
and during that time replacement of bypass waters was not
required. During March through September of water year
1988, the United States bypassed a total of 75,000 acre-feet
through the bypass drain. This water was replaced with a like
amount of other water, pursuant to Minute No. 242 of the
International Boundary and Water Commission.

During water year 1988, the average annual salinity of the
Colorado River water arriving at Imperial Dam was 650 ppm.
During this same period, the salinity of the waters arriving at
Morelos Dam was 723 ppm, resulting in an annual average
salinity differential of only 73 ppm, well within the
requirement of Minute 242 of the International Boundary and
Water Commission.

While no flows are scheduled in the bypass drain during water
year 1989, it is possible that about 100,000 acre-feet of such
discharges could occur, as in previous years. A minor amount
of drainage water also could be returned to the
Colorado River below Morelos Dam during 1989. Since
excess flow conditions are not expected, it will be necessary to
provide replacement water to Mexico for any bypassed flows.

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