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01;2"183 River's general salinity problem by passing the Colorado River Bas ii, Salinity Control Act of 1974 (Public Law 93-320). The Act provided for controlling the salinity of Colorado River water through specific actions authorized under Ti=les I and II of the Act. Title I of the Act was designed to enable the United States to comply with the water quality agreement negotiated with Mexico (Minute No. 242 of the International Boundary and Water Commission, United States and Mexico) . This agreement called for Mexico's allocated water to have a salt content no higher than 145 parts per million4 more than the water arriving at Imperial Dam (near Yuma. Arizona). The agreement was negotiated by a United States Presidential representative. who considered several permanent methods to achieve this goal. These methods inc luded programs to (1) desalt the irrigation drainage from the Wellton-Mohawk Irrigation District. (2) stop all We 11 ton-Mohawk irrigation drainage by retiring those farmlands from production, and (3) divert all Well ton-Mohawk irrigation drainage into the Santa Clara Slough in Mexico and replace the diverted water with state allocable water from upstream reservoirs. In the end, the desalting plan was selected because it was thought to be a "permanent and definitive" solution which would provide quality water to Mexico without reducing the basin. states' water allocations or current water usage. As part of the Title I program, Congress authorized the Bureau to construct, operate, and maintain a desalting complex near Yuma, Arizona. As detailed in Appendix 2. the Bureau was originally given authorization to expend $155.5 million (at April 1973 prices) to complete the complex and other defined measures. Some of the key features provided for were (1) the construction of a desalting plant designed to enable the Bureau to recover 132,000 acre-feet of the estimated 175,000 acre-feet of irrigation drainage expected to flow from Wellton-Mohawk farmlands, (2) the extension of an existing drainage canal to allow wastewater from the plant (approximately 43,000 acre- feet) and other drainage waters to be diverted .directly to the Santa Clara Slough in Mexico, (3) a program of acreage reduction and on-farm irrigation systems improvement to lessen the amount of Well ton-Mohawk irrigation. drainage, (4) the development of protective wells along the international border to help control Mexico's pumping of water from underground sources that straddle the border, and (5) the lining of the Coachella Canal in California to save water ordinarily lost. to ground seepage as a temporary source of water to replace diverted I;ellton-Mohawk irrigation drainage until the desalting plant was operable, Additionally, since the desalting plant would be unable to recover all Wellton-Mohawk irrigation drainage. the Bureau was authorized to find a replacement source for all irrigation drainage which could not be saved by the desalting process to preclude using 'Jater 4The United States commitment specifically called for the water delivered to Mexico to have an average salinity of not more than 115 parts per million, plus or minus 30 parts per million. over the average salinity at the Imperial Dam, 2 _.~,~... - ..=;