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3/z<.o1 FI i- W o -.J SYNOPOSIS OF TITLE I OF THE COLORADO RIVER BASIN SALINITY CONTROL ACT Title I of the Colorado River Basin Salinity Control Act was designed to include the necessary features for compliance with the United States ohligation to Mexico under Minute No. 2~2 of the International Boundary and Water Commission. The main features authorized under Title I include a 129 million gallon per day (mgd) desalting plant near Yuma, Arizona, a brine dis- charge canal, lining of the Coachella Canal, acreage retirement and irrigation efficiency improvement programs in the Wellton- Mohawk Irrigation and Drainage District, and development of a well field along the international boundary. A map showing the relative locations of the major features is shown on Figure I. In addition to the main features above, Title I authorized a feasibility study for replacement water from the desalting plant's reject stream and the acquisition of additional lands above Painted Rock Reservoir to permit operatIon of the dam and reservoir in times of serious flooding in accordance with the obligations of the United States under MInute No. 2~2. Subsequent to the enactment of this Act, a sIzing study for the Yuma Desalting Plant was undertaken. ThIs study was com- pleted in 1977 and recommended that the plant size be revised from the 129 mgd to 96 mgd. This lower capacity would comply 85 percent of the time with the salinity requirements spelied out In Minute No. 242. This requirement states that the water delIvered to Mexico above Morelas Dam must not have an annual average salinity concentration of no more than 115 parts per mIllion (ppm) + 30ppm over the annual average salinIty of Colorado River waters-which arrive at Imperial Dam. The compliance rate varies not only with the salinity levels at Imperial Dam, but also with the quantity of return flow from the Wellton-Mohawk District. The flow at the time of the study was 173,000 acre-feet, but was projected to decrease to 167,000 acre-feet by 1981, with further decreases expected. The plant was sized based on the lower value with a return flow salinity concentration of about 3200 ppm. With all of the above factors taken into account, it was esti- mated that the amount of reject water would average about 46,000 acre-feet on an annual basis. Some of the initial work has been awarded, but the plant is not expected to be operational until 1986. In order to handie the above-mentioned reject and excess drainage waters, a bypass drain was authorized from Morclas Dam to the Santa Clara Slough In the Gulf of California. The canal is approximateiy 51 mIles in length and has a capacity of about 350 cubic feet per second (cfs). The canal was completed in July of 1977.