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<br />, , <br />\ <br />, <br /> <br />Salt loading OCCurs as a result of weathering and the dissolution <br /> <br />of soluble salts in soil and substrata. In addition, salt concentration <br /> <br />occurs due to consumptive use, such as agricultural or industrial appli- <br /> <br />cations of water in the basin. Generally, the application of irrigation \: <br /> <br />water results in increased salt_concentrations because of both salt 10ad- 1 <br /> <br />ing and salt concentration. The salt load fluctuates annually with the r <br /> <br />overall basin water supply. Without control measures and as the States <br /> <br />continue to develop their compact-apportioned waters, the salinity <br /> <br />at Imperial Dam is projected to increase, possibly reaching a level of <br /> <br />1,140 mg/L at the dam by the year 2000. <br /> <br />In response to the Federal Water Pollution Control Act Amendments of <br /> <br />1972 (P.L. 92-500), the Colorado River Basin States adopted salinity <br /> <br />control standards for the Colorado River. These standards, shown below <br /> <br />for three stations on the Lower Colorado River, have been approved by <br /> <br />the Environmental Protection Agency: <br /> <br />Station <br /> <br />Annual Flow-Weighted <br />Average Concentration (mg/L) <br /> <br />Below Hoover Dam <br />Below Parker Dam <br />At Imperial Dam <br /> <br />723 <br />747 <br />879 <br /> <br />The CRWQIP goal is to maintain Lower Colorado River salinity levels <br /> <br />at or below 1972 historical levels while the Basin States continue to <br /> <br />develop their compact-apportioned waters. To attain this goal, an estimated <br /> <br />2.8 million tons of salt annually must be intercepted before entering <br /> <br />the river system by the year 2000. The following illustration shows <br /> <br />historical salinity levels and projected levels with and without the <br /> <br />CRWQIP. <br /> <br />~ .. ('; '." r). <br />\.' 'Ji. Uv ,} <br /> <br />15 <br />