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Water Quality Operations In recognizing the need to manage the water quality ot the Colorado River, it was recommended that long-term salinity increases in Ihe 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 lor a basin.wide apprORch to salinity conlrol v/hile the Upper Basin continues to develop its compact.apportloned walers. The initial step toward improvement 01 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, authonzing the construction 01 various features for the enhancement and protecllon 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 Sta',es to comp'y with its obiigation under the agreement with Mexico of Augusl 30, 1973 (Minute 242 of the International Boundary and Water Commission, United States and Mexico). which was con. cluded pursuanl 10 Ihe Treaty of February 3, 1944 (TS994). Title I authorized the construction of Ihe Yuma Desalting Plant and a bypass drain to ultimately discharge the plant"s brine. These faCili- ties, and others, Will enable the delivery of waler at Morelos Dam, for subsequent use <n Mexico, having an average salinity no greater than 115 parts per million (ppm) :t 30 ppm (United Stales count) higher than the annual average salinity 0\ the Colorado River water at Imperial Dam. Title II of the Act authorized the Secretary to construCI a number of units In the basin above Imperial Darn, as well as the investigation of several other potential salinity control units. 26 Irrigation Managemenl Requires Soil MOlslure Measurements 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. Since the water quality aspecls 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 minimal discussion of this aspect of the operation below Imperial Dam is presented in this report. During water year 1985, the United States bypassed a Iota I of 130,800 acre. feet through the Bypass Drain. As the river was in an excess flow condition during 1985, 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 Treafy of 1944. During water year 1985, the average annual salinity of the Colorado River water arriving at Imperial Dam was 613 ppm. During this same period, the salinity of the waters arriving at Morelos Dam was 641 ppm, resulting in an annual average salinily ditferential oj only 28 ppm, well within the requirement 01 Minute 242 of the International Boundary and Water Commission. The tOlal flows in tile bypass drain during water year 1986 are projected to be 130,000 acre-feet. A minor amount of drainage waler could be returned to the Colorado River below Moretos Dam during 1986. Due to the excess flow conditions that are expected, it will not be necessary to provide replacement water to Mexico for fhe bypassed flows.