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I I I I I I I I I I I 002027 (2) Salinity Concerns The high levels of salinity in the water delivered to Mexico began causing serious problems between the United States and Mexico in the 1960s. When the concentration of salts in the water delivered to Mexico increased radically, crop production -- particularly vegetable production -- diminished and the irrigated-land in the Mexicali Valley became significandy more saline. TIlls led to protests by Mexico and a series of interim agreements to control the salinity of Colorado River water delivered to Mexico under the Treaty. In 1965, Minute 218 (effectively an amendment) to the United States Mexico Treaty) was approved. It required the United States to bypass around Morelos Dam part of the extremely saline (6,000 mg/I1DS) agricultural drainage from the Wellton-Mohawk district in Arizona. Negotiations for a pennanent resolution of the salinity issue continued between 1965 and 1972. In 1973, an agreement was reached restricting the allowable increase in salinity between Imperial Dam and the Northerly Int~mational Boundary to 115 ppm + 30 ppm. The agreement was embodied in Minute 242 to the Treaty. To achieve the standards of Minute 242, all of the agricultural drainage from the Wellton-Mohawk area would have to be desalted or else bypassed around Morelos Dam without being credited against the Treaty delivery obligation. Bypassing flows without charge against the 1.5 million acre-feet per year Treaty delivery obligation resulted in additional water being released from Hoover Dam to meet the increased total delivery to Mexico. This additional Hoover Dam release could decrease the amount of water available to US water users in a serious drought. (3) Yuma Desalting Plant I I I I I I I I The Yuma Desalting Plant was constructed to enable the United States to comply with Minute 242. The plant was completed in 1992 and operated during most of 1993. However~ because surplus river flows allowed enough good quality water. to reach Mexico and because of the high cost of operation, the plant was shut down in the early 19905 and remains idle. A decision to operate the plant could be made by the Secretary of the Interior as a part of the Annual Operating Plan after consultation with interested and affected parties. That decision also would be subject to congressional appropriation of operating funds. The Colorado River Basin states (particularly the State of Arizona, which has the lowest priority for river water) continue to urge the Secretary to operate the plant and thereby reduce the likelihood of future water shortages in the Umted States. (4) The Bypass Drain and the Cienaga The Bypass Drain was constructed pursuant to Minute 242 to carry any untreated and bypassed Wellton-Mohawk drainage water and the salt-water waste stream from the Yuma Desalting Plant to an acceptable tenninallocation. It has a conveyance capacity of 300 cubic feet per second (210,000 acre-feet per year). When the Bypass Drain was originally designed, its tenninus at the Cienaga was largely a sand and mud flat lU:ea that was occasionally washed with seawater during high tides. Flows were expected to reach the Gulf, but in fact were blocked by a rise in the land that created a self-contained basin. The Bypass Drain began operating in 1977, and has carried the untreated brackish agricultural drainage water since then. 1his delivery of brackish agricultural drain waters to the Cienaga supports many species of birds and fish, including the endangered Yuma clapper rail, desert pup fish, and a variety of ducks and other birds. 12