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<br />W <br />-..:! <br />W <br />CD <br /> <br />IV. PROBLEMS AND NEEDS <br /> <br />Many impac~s result from the increasing salinity of the water of the <br />Colorado River. By far, the most significant impacts are economic. <br /> <br />A. Colorado River Salinity <br /> <br />The Colora~o River, at its headwaters in the mountains of north-central <br />Colorado, has a salinity (dissolved mineral concentration) of only about <br />50 mg/L. The principal dissolved constituents in the river water are <br />the cations: calcium, magnesium, and sodium; and the anions: sulfate, <br />chloride, ~nd bicarbonate. The salinity concentrations progressively <br />increase downstream as a result of water diversions and salt contributions <br />from a variety of sources. In 1979, the salinity concentration averaged <br />about 810 !TIg!L at Imperial Dam, the last major diversion point on the <br />Colorado River in the United States. Without control measures, the ,concen- <br />tration is, projected to increase, possibly reaching a level of 1140 mg/L at <br />Imperi al Dam by the year 2000 [2J. <br /> <br />As the fol~owing graph illustrates, since 1949 the general trend in salin- <br />ity concentrations at Imperial Dam has been upward, although since 1970 <br />these conc~ntrations have actually decreased. This recent downward trend <br />is conjectured to be the result of the construction of Colorado River <br />Storage PrOject reservoirs in the Upper Basin and the increased releases of <br /> <br />RECORDED SALINITY LEVELS AT IMPERIAL DAM <br />WITH PROJECTIONS THROUGH THE YEAR 2010 <br /> <br /> 120,0 <br />~ 1100 <br />-.! <br />...... <br />C9 <br />::;: <br />~ 1000 <br />(f) <br />Cl <br />-.! <br />a 90b 879 mg/L <br />(f) <br />Cl <br />W <br />::J 800 <br />a <br />(f) <br />(f) <br />Cl 700 <br />-.! <br /><>: <br />f- <br />a 600 <br />f- <br /> 500 <br /> 1940 1950 1960 1970 <br /> <br /> <br />/-- <br />,/ <br />/ <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />-- <br />-- <br /> <br /> <br />Historical <br />____ Pl"ojectedJl <br /> <br /> <br />1980 <br /> <br />1990 <br /> <br />2000 <br /> <br />2010 <br /> <br />.u Without Water Quality Improvement Program, <br /> <br />IV-1 <br />