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Colorado River Basin Salinity Control Program Currently, 21 of the planned full complement of 35 wells and associated conveyance and energy facilities have been constructed. The wells are connected by a 15.3-milepipeline and open concrete-lined canal that carries water by gravity across the Southerly International Boundary. With 35 wells, the PRPU would be capable of producing about 125,000 acre-feet of water per year. Ultimately, 125,000 acre-feet of water from the PRPU, combined with 15,000 acre-feet of water from wasteways and drains in the Yuma Valley, would furnish 140,000 acre-feet of Mexico's 1.5-million-acre-foot annual entitlement. The water would be delivered at the Southerly International Boundary near San Luis, Arizona. In addition, 35,000 acre-feet could be withdrawn by private wells and/or 242 wells for use on private land to equal the 160,000 acre-foot limit for pumping in the 5-mile zone. Currently, water from wasteways and drains in the Yuma Valley exceeds 15,000 acre-feet per year. Should these wasteway and drain flows diminish in the future, wells will be added to the PRPU, as needed, to ensure that approximately 140,000 acre-feet can be delivered at the Southerly International Boundary at all times. Additionally, as authorized by Title I, approximately 23,500 acres of private, State, and State- leased lands have been acquired within the 5-mile zone. The purpose of these acquisitions is to limit development and thus limit United States ground-water pumping to 160,000 acre-feet per year, as required by Minute No. 242. The acquisitions were completed in 1984. Yuma Desalting Plant The Yuma Desalting Plant is built on a 60-acre tract of land 6 miles west of Yuma, Arizona. The purpose of the plant is to upgrade the quality of irrigation drainage water from the Wellton- Mohawk Irrigation and Drainage District (WMIDD) so that it can be returned to the Colorado River and delivered to Mexico. The operational design parameters set up for the plant determined that a membrane desalting process was technically feasible and is suitable for the Yuma Desalting Plant operation. The factors included in this formula are the volume of water delivered to Mexico, the salinity differential required by Minute No. 242, the salinity of the Colorado River at Imperial Dam, the volume of drain water treated, the salinity of the drain water, a number of other factors related to the diffuse return flows below Imperial Dam, and plant operational factors. A study done in 1978 by the Advisory Committee on Irrigation Efficiency, WMIDD, recom- mended expansion of onfarm irrigation improvement measures. These improvements were expected to reduce irrigation drain flow to about 108,000 acre-feet per year. In addition, the Colorado River Basin States have established a salinity standard at Imperial Dam of 879 mg/L. Using a salt balance formula and assuming an irrigation drain flow of 108,000 acre-feet and salinity at Imperial Dam of 838 mg/L, a plant size of 73 million gallons per day would be required to treat the irrigation return flow portion of the total drainage flow. The plant was constructed to produce about 72.4 million gallons of desalinated (product) water per day when operated at full capacity. This would result in a delivery of about 68,500 acre-feet ofn 41