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<br />20 <br /> <br /> <br />Lower Colorado Region Comprehensive Framework Study (WRC) <br /> <br />~ <br />~ <br />~ The report by the Water Resources Council dated June 1971 states <br />(,,1 <br />that high levels of dissolved mineral salts in surface and ground <br /> <br />waters are the major water quality problem in the region. With <br /> <br />few exceptions, most s\lrface and ground-water supplies have mineral <br /> <br />concentrations exceeding 500 mg/l, and many exceed 1,000 mg/l. The <br /> <br />salinity of the supplies affects domestic, industrial, and agricul- <br /> <br />tural uses. <br /> <br />The Colorado River enters the region at concentrations exceeding <br /> <br />500 rng/l, varies between 500 and 900 mg/l at most diversion points, <br /> <br />'and increases to as high as l,lOO to 1,150 mg/l for short periods <br /> <br />of time at Imperial Dam. Salinity increases in the Colorado River <br /> <br /> <br />from Lees Ferry, Arizona, to Imperial Dam are due principally to <br /> <br />inputs from saline springs and the concentrating effects of con- <br /> <br />sumptive use and reservoir evaporation. <br /> <br />Dissolved solids concentrations in the Colorado River are estimated <br /> <br />to increase about 55 to 75 percent between 1965 and 2020, with the <br /> <br />exception of Imperial Dam where the concentration is estimated to <br /> <br />double. These results are based on the assumptions that the Central <br /> <br />Arizona Project is in operation and no salinity controls are incor- <br /> <br />porated in future developments, <br />