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. PART V COLORADO RIVER WATER QUALITY ASSESSMENT ~ The Colorado River area contiguous to California serves a large influx of recreationists almost year round. but many of these people camp indiscriminately on public lands along the river' 5 edge. Sanitary facilities, though previously limited, are n01,1 improving, an important factor for the protection of public health. ,.. .... ,.... The Colorado River is highly regulated and its waters are intensively used and reused. Water in the California reach of the Colorado River is sodium-calcium sulfate in character and is very hard. The threshold value of chlorides, reported by the University of California Agriculture Extension Service in Guidelines for the Inter- pretation of ~'ater Quality for Agriculture, February 8, 1974,18] is 142 mg/L. Prior to 1971, the average chloride concentration at Topock was about 90 mg/L, and just north of the International Boundary it was 240 mg/L. This increasing downstream salinity can be attributed pri- marily to irrigation return flows coupled with the reduced flow in the Colorado River resulting from diversions bet\o'een Parker and Imperial Dams. _." . Although chlorides are a definite water quality problem, the specific conductance data for the past decade have shown a minor but steady improvement. During water year 1980, a slight improvement in electrical conductivity was rpcorded at both stations. While conduc- tivity increased again in water ypar 1981, the mean values are gf'nerally below those of the laRt decade. Turbidity at the International Boundary station increased markedly in March 1980 but declined later in the year. Minimum dissolved oxygen values at this station violated the minimum standard (6.0 mg/L) in slJIlmer 1980, and equalled the standard in 1981. In \,later year 1980, DOT was detected at 0.02 ug/L (micrograms per liter), violating the EPA standard of 0.001 mg/L. found at standard During water year 1980, a concentration of 0.05 of 0.001 mg/L. PCB's (polychlorinated byphenyls) ~re mg/L, a value in excess of the EPA (J 10-) 75 In 1981 amounts Fish tissue analyses have disclosed repeated moderate levels ppb) of DOT in fish from the Colorado River frem 1978 to 1980. the DOT level dropped to 22 ppb (parts per billion). Trace of Dacthal were detected in 1979. The IDS concentration of the Salton Sea is currently about 38,000 mg/L and is rising at a rate of about 400 mg/L per year. When the salinity reaches 40,000 mg/L, it is expected that this concentration will be unsuitable for the important sport fisher~' as ~ll as water-oriented recreation and wildlife habitation. . There has been a lack of suitable sites within the basin for disposal of large volumes of waste materials generated by geothermal and agricultural pesticide operations. Because the geothermal industry in the Imperial Valley is developing rapidly, disposal of the brim' wastes is creating growing problems; however, a major disposal site 'oo'aS opened in 1981 in the Imperial Valley. 19