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<br /> 0 CHAPTER II <br />. w::. <br />N <br /> ~ the river from such sources as erosion and leaching of saline sol1 <br /> msterials, irrigation return flows, and saline springs and wells . The <br /> <br /> <br />annual salt load of the river under present conditions is estimated at <br /> <br />about~~ion tons as measured just below Hoover Dam, about 260 miles <br /> <br />uPs~from Imperial Dam. <br /> <br />The salt concentrating effect occurs from consumptive use, which <br /> <br />reduces the volume of water in the river without reducing the total <br /> <br />amount of salt it carries. Examples include irrigation, M&I use, trans- <br /> <br />basin diversions, transpiration from vegetation, and evaporation. As <br /> <br />the water is used and reused several times along the length of the <br /> <br />river, both increased concentration and salt loading cause greater <br /> <br />. <br /> <br />salinity. <br /> <br />The process is likely to continue, since the potential <br /> <br />demands on the river exceed its dependable supply. <br /> <br />The high salt concentration in the Lower Colorado River Basin <br /> <br />adversely affects more than 17 million people and about 1 million acres <br /> <br />of irrigated farmland in the United States. Affected most severely are <br /> <br />M&I and water users in the Las Vegas, Los Angeles, and San Diego areas <br /> <br />and irrigators in the Imperial Valley of southern California and in <br /> <br />Arizona. According to recent studies by Reclamation, quantified econo- <br /> <br />mic <br /> <br />losses <br /> <br />in <br /> <br />the <br /> <br />Lower <br /> <br />Basin <br /> <br />average <br /> <br />$540,000 <br />,--~ <br /> <br />annually <br /> <br />for <br /> <br />each <br /> <br />increase of 1 mg/L of salinity at Imperial Dam in the range of 875 to <br /> <br />1,225 rog/L, based on January 1983 pricea. <br /> <br />The losaes consist of <br /> <br />$405,000 in direct impacts and $135,000 in indirect impacts. The losses <br /> <br />associated with M&I use occur primarily from increased water treatment <br /> <br />. <br /> <br />24 <br />