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<br />o <br />l\;) <br />w <br />OJ <br /> <br />CHAPTER III <br /> <br />" <br /> <br />NEED FOR ACTION <br /> <br />Colorado River Salinity <br /> <br />The Colorado River at its headwaters in the mountains of north- <br />central Colorado has a salinity concentration of about 50 milligrams per <br />liter (mg/L). The concentration progressively increases downstream as a <br />result of depletions and salt contributions from a variety of sources <br />and in 1982 averaged about 825 mg/L at Imperial Dam, the last major <br />diversion point of the Colorado River in the United States. Unless <br />c.ontrol m.e.asurea aye undertaken, the concentrations are expected to <br />increase. <br /> <br />Affected most severely by the salinity are municipal and industrial <br />water users in the Las Vegas, Los Angeles. and San Diego areas and irri- <br />gators in the Imperial Valley of southern California and Arizona who <br />experience economic losses. Based on January 1983 prices, quantified <br />damages in the Lower Colorado River Basin attributable to salinity are <br />estimated at $540,000 annually for each mg/L increase at Imperial Dam <br />when concentrations reach the range of 875 to 1,225 mg/L. The losses <br />consist of $405,000 in direct impacts and $135,000 in indirect impacts <br />and are associated ",ith increased water treatment costs, accelerated <br />pipe corrosion and appliance "'ear, increased soap and detergent needs, <br />and decreased drinking water palatability. For irrigators the higher <br />concentrations cause decreased crop yields, altered crop patterns, in- <br />creased leaching and drainage requirements, and increased management <br />costs. <br /> <br />In response to the Federal Water Pollution Control Act as amended <br />(Public Law 92-500), the seven Colorado River Basin States adopted, and <br />the Environmental Protection Agency approved, 1972 concentrations at <br />three points on the Lower Colorado River as salinity control standards. <br /> <br />Station <br />Belo", Hoover Dam <br />Below Parker Dam <br />At Imperial Dam <br /> <br />Annual <br />flo",-weighted <br />concentration <br />(mg/L) <br />723 <br />747 <br />879 <br /> <br />.' <br /> <br />The goal of the Colorado River Water Quality Improvement Program is <br />to maintain concentrations at or below these levels while the Basin <br />States continue to develop their compact-apportioned ",aters. To attain <br />this goal, about 2.8 million tons of salt per year must be intercepted <br />before entering the river system. <br /> <br />5 <br />