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OOJ059 A PRELIMINARY EVALUATION OF THE ONGOING SALINITY CONTROL AND RELATED PROGRAMS IN THE COLORADO RIVER BASIN I NTRODUCTI ON . This study is considered a preparatory step to an MBO (management by objective) evaluation scheduled for September 1984. The Colorado River Water Quality Office was also requested to evaluate the ongoing salinity control and related programs in the Colorado River Basin prior to including certain preconstruct ion (advance planning) activities in the fiscal year 1985 budget request. The Colorado River provides water for life to over 17 million people in parts of seven states and Mex i co. The river, however, carri es about 9 mill i on tons of salt annually past Hoover Dam. This salt load causes millions of dollars in damages to agriculture and cities in the Lower Basin States. Damages in 1982 are estimated at about $120 million annually for United States water users with a salinity concentration level of approximately 825 mg/L. Damages are projected to be $238 million annually by the year 2010, without salinity control, if salinity reach es 1090 mg/L. Figure 1* shows the historical salinity levels at Imperial Dam from 1940 to 1982 and the CRSS (Colorado River Simulation System) projections through the year 2010 without salinity control. While historical trends vary and the historical trace reflects impacts of filling Lakes Mead and Powell, it should be noted that the salinity level trend is again rising. The projections throughout this report were derived from the CRSS model except where noted. In 1974, Public Law 93-320 directed the Secretary of the Interior , "to proceed wi th a program of works of improvement for the enhancement and protection of the quality of water available in the Colorado River for use in the United States and the Republic of Mexico, and to enable the United States to comply with its obligations under the agreement with Mexico of August 30, 1973 (Minute No. 242 of the International Boundary and Water Commi ss i on, Un ited States and Mex i co) * * *" This evaluation includes the CRWQIP (Colorado River Water Quality Improvement Program) above Imperial Dam, USDA and BLM's assistance in this effort, how the CREST program and an operational cloud seeding program could benefit salinity control, and whether the program is, in fact, necessary for the enhancement and protection of the quality of water available in the Colorado River, as described in Public Law 92-500 as amended and Public Law 93-320. This report, in order to maintain brevity, will provide only a programmatic overview. Details of the various components of the CRWQIP are described in the January 1983 Status Report on the CRWQIP. Before examining CRWQIP, a brief review is needed of the relationship of salinity control and related program objectives to the TDS (total dissolved solids) numeric criteria standards and the Mexican salinity agreement (Minute 242). * Figures are at the end of the text.