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PART IV COLORADO RIVER WATER QUALITY ASSESSMENT e result of additional treatment at the point of use and damage to plumb- ing. Nevada is doing its part in maintaining present levels by applying the salinity control policy of the Forum to control the industrial and municipal sources. F. Cali fornia The salinity of the Colorado River is a matter of great concern to California. Southern California receives about 65 percent of its total water supply from the Colorado River, which provides a full water supply to about 800,000 irrigated acres and a full or supplemental supply to about 12 million people. Because California is located at the lower end of the Colorado River Basin, the water that it diverts contains all of the dissolved salts that have entered the river upstream. e Colorado River water is used in California to grow many specialized high value crops such as avocados, dates, citrus, grapes, and winter vegetables, as well as basic crops such as cotton, alfalfa, wheat, and sugar beets. Because of its high salinity, Colorado River water re- quires special management so that crop yields may be maintained and low- salt-tolerant plants will not be damaged or killed.. Agricultural areas of California are already suffering significant economic detriments in their utilization of Colorado River water. Those detriments will in- crease if Colorado River salinity levels are allowed to increase with development of the Colorado River Basin. The heavily urbanized areas of southern California receive Colorado River water distributed by the Metropolitan Water District. Urban water users of Colorado River water have been experiencing economic detriments due to both its high salinity and its high hardness. Several hundred thousand water users have installed individual water softeners on their plumbing facilities, but this process aggravates the already existing salt balance problems in ground water basins of southern California. Blending with other imported supplies of lower salinity is practiced; however, increased demand on those other supplies for additional blending to offset Colorado River water salinity increases would have serious adverse effects. Further, as the salinity of the Colorado River water for urban use increases, the potential for water reuse decreases, thus increasing the demand for additional water sup- plies. e Most of the. salinity in the Colorado River derives from sources upstream from California, but there are local contributions in the Palo Verde Region. The Bureau of Reclamation, in cooperation with the U.S. Department of Agriculture and the Palo Verde Irrigation District, has initiated a detailed study of the sources of salinity and possible control schemes for the Palo Verde Valley. The Colorado River Basin Salinity Control Forum has developed a plan for salinity control of the Colorado River. The California Regional Water Quality Control Board 21