WSP00585

• File Number: 8282.600.10
• Description: Colorado River Operating Annual Reports
• Basin: Colorado Mainstem
• Date: 1/1/1986
• Author: USDOI/BOR
• Title: Operation of the Colorado River Basin 1986 Projected Operations 1987
• Water Supply Pro - Doc Type: Publication

Water Quality Operations

In recognizing the need to manage 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 of the Colorado River Basin Salinity
Control Act of 1974 (Act) (Public Law 93-320) on June 24,
1974, authorizing the construction ofvarious 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 ofthe Act enables the United States to comply with its
obligation under the agreement with Mexico of August 30,
1973 (Minute 242 of the International Boundary and Water
Commission, United States and Mexico), which was
concluded pursuant to the Treaty ofFebruary3, 1944 (TS994).
Title I authorized the construction of the Yuma Oesalting
Plant and a bypass drain to ultimately discharge the plant's
brine. These facilities, and others, will enable the delivery of
water at Morelos Oam, for subsequent use in Mexico, having
an average 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 Oam.

Title II of the Act authorized the Secretary to construct a
number of units in the basin above Imperial Oam, 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 biemiial
report to the President, the Congress, and the Colorado River
Basin Salinity Control Advisory Council. Since the water
quality aspects of Colorado River operations are extensively
described in that biennial series, the latest of which is Report
_ No. 12 entitled, 'Quality of Water, Colorado River Basin,"
dated January 1985, only min;mal discussion of this aspect of
the water quality below Imperial Dam is presented in this
report.

Ouring water year 1986, the United States bypassed a total of
105,500 acre-feet through the Bypass Orain. As the river was
in an excess flow condition during 1986 due to the high runoff
in the basin, no specific releases from the upstream reservoirs
were necessary to replace this water to meet the quantity
requirements of the Mexican Treaty of 1944.

During water year 1986, the average annual salinity of the
Colorado River water arriving at Imperial Dam was 584 ppm.
During this same period, the salinity of the waters arriving at
Morelos Oam was 605 ppm, resulting in an annual average
salinity differential of only 21 ppm, well within the
requirement of Minute 242 of the International Boundary and
Water Commission.

The total flows in the bypass drain during water year 1987 are
projected to be 105,000 acre-feet. A minor amount of drainage
water could be returned to the Colorado River below More\os
Oam during 1987. Oue to the excess flow conditions that are
expected, it will not be necessary to provide replacement
water to Mexico for the bypassed flows.

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