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<br />. <br /> <br />. <br /> <br />. <br /> <br />o <br />~ <br />l\;. <br />l",) <br /> <br />CHAPTER II <br /> <br />NEED FOR ACTION <br /> <br />costs, accelerated pipe corrosion and appliance wear, increased soap and <br /> <br />detergent needs, and decreased drinking water palatability. For irriga- <br /> <br />tors, the higher concentrations cause decreased crop yields, altered <br /> <br />crop patterns, increased leaching and drainage requirements, and <br /> <br />increased management costs. The damages attributable to salinity were <br /> <br />estimated at $96 million in 1981 in the Lower Basin States and, without <br /> <br />salinity control measures, will likely increase with further development <br /> <br />of water resources. Unquantified and indirect damages also occur in the <br /> <br />Upper Basin. <br /> <br />The historical salt load fluctuates annually with the overall basin <br /> <br />water supply. Without control measures, the salinity at Imperial Dam is <br /> <br />expected to increase as the Upper Basin States continue to develop their <br /> <br />compact-apportioned water. Since 1949 the general trend of the concen- <br /> <br />tration at the dam has been upward although since 1970 it has decreased, <br /> <br />possibly as a result of the long-term effect of filling such Colorado <br /> <br />Ri ver Storage froject reservoirs as Lake fowell. <br /> <br />This downtrend is <br /> <br />believed to be a temporary phenomenon and is within the natural <br /> <br />variation expected after accounting for the 4-year reservoir storage of <br /> <br />total annual river flow below Hoover Dam. The projected concentration <br /> <br />at Imperial Dam through the year 2010 is expected to follow the overall <br /> <br />rising trend if water quality improvement programs are not implemented <br /> <br />and depletions continue to increase. <br /> <br />In response to the Federal Water Pollution Control Act as amended <br /> <br />(Public Law 92-500), the seven Colorado River Basin States adopted and <br /> <br />25 <br />