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<br />. <br /> <br />. <br /> <br />CHAPTER IV <br />PROBLEMS AND NEEDS <br /> <br />Salinity <br />The Colorado River at its headwaters in the mountains of north <br /> <br />central Colorado has a salinity (dissolved mineral concentration) level <br /> <br />of only about 50 mg/L. The salinity progressively increases downstream <br /> <br />as a result of diversions and salt contributions from a variety of <br /> <br />sources. In 1979, the salinity level averaged about 820 mg/L at Imperial <br /> <br />Dam, the last major diversion point on the Colorado River in the United <br /> <br />States. Without control measures, the concentration is projected to <br /> <br />increase, possibly reaching a level of 1,140 mg/L at Imperial Dam by the <br /> <br />year 2000. <br />The high salt load of 10 million tons of salt annually 1n the Lower <br /> <br />Colorado River Basin adversely affects more than 17 million people and <br /> <br />about 1 million acres of irrigated farmland in the United States. <br /> <br />Municipal and industrial water users and irri~ators experience estimated <br /> <br />direct and indirect annual economic losses of $450,000 (January 1980 <br /> <br /> <br />prices) for each increase of I mg/L in salinity at Imperial Dam. <br /> <br /> <br />The losses associated with municipal and industrial use occur <br /> <br /> <br />primarily from increased water treatment costs, accelerated pipe corrosion <br /> <br />and appliance wear, increased soap and detergent needs, and decreased <br /> <br />drinking water palatability. The Public Health Service recommends that <br /> <br />drinking water contain no more than 500 mg/L of total dissolved solids <br /> <br />(TDS). For irrigators, the higher concentrations cause decreased crop <br /> <br />yields, altered crop patterns, increased leaching requirernentseid!487 <br /> <br />13 <br />