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. . PROBLEMS AND NEEDS The Colorado River at its headwaters in the mountains of north-central Colorado has a salinity (dissolved mineral concentration) of only about 50 mg/L. The salinity progressively increases downstream as a result of water diversions and salt contributions from a variety of sources. In 1979, it averaged about 810 mg/L at Imperial Dam, the last major diversion point on the Colorado River in the United States. Without control measures, the concentration is projected to increase, possibly reaching a level of 1140 mg/L at Imperial Dam, by the year 2000, The high salt load of 10 million tons of salt annually in the Lower Colorado River Basin adversely affect more than 17 million people and about 1 million acres of irrigated farmland in the United States. --------'-~-'----'------ , Municipal and industrial water users and irrigators experience estimated direct and indirect annual economic losses of $450,000 (January 1980 prices) for each increase of 1 mg/L in salinity at Imperial Dam. The losses associated with municipal and industrial use occur primarily from increased water treatment costs, accelerated pipe corrosion and appliance wear, increased soap and detergent needs, and decreased drinking water palatability. The Public Health Service recommends drinking water contain no more than 500 mg/L of total dissolved solids (TDS). For irrigators, the higher concentrations cause decreased crop yields, altered crop patterns, increased leaching and drainage require- ments, and increased management costs. Agricultural losses begin when salinity levels reach 700-850 mg/L depending upon the soil condition and type of crops grown, ntll) oj 1.......' L" ~ \J 4 8