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. . l\) o ,.j::o CD . . . . . . . . . During the first period, the United States shall discharge to the Colorado River downstream from Morelos Dam Well ton-Mohawk drainage waters at the annual rate of 118,000 acre-feet and substitute therefor an equal volume of other water to be discharged to the Colorado River above Morelos Dam. In addition, the remaining drainage waters will be discharged downstream from Morelos Dam in accordance with Mexico's request. The United states will not replace these waters. During the second period, the United States has agreed to bypass all of the Wellton-Mohawk drainage and to replace it with water of Imperial Dam quality. To make up a large portion of that loss, studies have demonstrated that approximately 132,000 acre-feet of water can be saved by the replacement of a 49-mile reach of the Coachella Canal with a new concrete-lined canal adjacent to the existing canal. The water saved can be used as replacement water for the bypassed water until needed by other priority users in the Lower Colorado River Basin. T:'{ . DESALTING COMPLEX The Desalting Complex consists of those facilities and measures required to treat Wellton-Mohawk drainage waters to assure that waters delivered to Mexico upstream ot Morelos Dam will have an average annual salinity of no more than 115 ppn :!. 30 ppn TDS more than the average annual salinity of Colorado River waters arriving at Imperial Dam. These measures would consist of those necessary to treat the water and to provide drainage waters for treatment of the quantity and quality necessary to minimize the costs of the treatment works. The total estimated installation cost of the Desalting Complex is $98,050,000. A detailed account of installation and annual operating costs is provided in the Cost SUIIIJII8.I'y at the end of thi s Executive Summary. A. Desalting Plant The plant will be designed to accept the drainage waters from the Well ton-Mohawk District for desalting. Product water from the plant will be blended with remaining drainage to produce water with the same or lesser salinity than that arriving at Imperial Dam. For purposes of cost estimating, certain assumptions were made, including: 1. The salinity of the water at Imperial Dam will be 910 ppm TDS during the first f'ull year of plant operation. 2. The quantity of drainage water from the Wellton-Mohawk District will not exceed 175,000 acre-feet per year. 3. The salinity of the drainage waters from the Well ton-Mohawk District will be 3,100 ppm TDS at the time the plant goes into operation. 10