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Agenda Item 12f Attachment November 19-20,2001 Board Meeting Page 5 of9 MEMORANDUM TO: Colorado Water Conservation Board Members FROM: Randy Seaholm Chief, Water Supply Protection DATE: September 14,2001 SUBJECT: Agenda Item 8g, September 24-25, 2001, Board Meeting - Colorado River Basin Issues - Discussion on Future Policy Regarding the Yuma Desalter Plant Backl!round The 1944 Treaty that guaranteed MexiCo 1.5 MAF of Colorado River water annually "from any and all sources" did not set any water quality or salinity standard. Irrigation water with high concentrations of salinity is an economic problem because it reduces crop yields and even precludes the growing of certain salt-sensitive crops, particularly vegetables like lettuce and tomatoes. : Between 1960 and 1961, the salinity ofwllter delivered to Mexico increased from 800 ppm to in excess of 1300 ppm. There wef(~ two primary reasons for this increase. First, the Wellton-Mohawk Irrigation and Drain~ge District near Yuma, Arizona began operation of a pumped drainage system that retutned drain water of about 6,000 ppm to the river. Second, the filling of the Colorado River Storage Project, in particular Glen Canyon Dam, reduced the flows in the lower Colorado River. As a result, in November 1961, Mexico filed a formal diplomatic protest, charging the U.S. with violating intemationa1law. In 1965, the U.S. and Mexico agreed to several temporary measures for reducing the jsalinity of Colorado River water under Minute 218. The search for a "permanent, defihitive and just solution" ended with the signing of Minute 242 on August 30, 1973. Minute 242 guarantees Mexico that the average annual salinity of its treaty deliveries will be no more than 115 ppm higher than the salinity of water behind hnperial Dam, plus or minus 30 ppm. Subsequently, the Colorado River Salinity Control Program that! grew out of PL 93-320 established a salinity standard of 879 ppm for the water arriving at hnperia1 Dam. To implement Minute 242, the U.S. Co*gress passed the Colorado River Basin Salinity Control Act (CRBSCA or PL 93-320) 0* June 24, 1974. The CRBSCA has two parts, Title I-Programs Downstream from hnpeIial Dam and Title II-Programs Upstream of hnperial Dam. Title I of the CRBSCA authorized the Secretary of Interior to, among other things, construct, operate and maintain the Yuma Desalting plant to reduce the salinity of drain water from the Wellton-Mohawk division of the Gila Project, extend the e e ..