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<br />control measures, however, the salinity level is <br />projected to increase, possibly reaching a level of 1005 <br />mg/L at Imperial Dam by about 2010. <br />Average salinity levels fail to give an accurate <br />picture or salinity levels prior to development in the <br />basin. Before the construction of Hoover Dam, salinity <br />levels in the Lower Basin fluctuated wildly during a <br />given year in inverse relation to the flow: during <br />periods of high runoff, the salinity level was extremely <br />low: when the flow diminished, the salinity level <br />increased dramatically. construction of Hoover Dam, in <br />addition to preventing destructive flooding and providing <br />a reliable, year-round source of supply, provided the <br />Lower Basin with water supply relatively uniform in <br />salinity content. As a result, California and Arizona <br />were able to develop a year-round agricultural base, the <br />principal crops of which were dependent upon water fairly <br />low in salinity. As significant development in the Upper <br />Basin began in the 1950s and 1960s, the average salinity <br />level of the Colorado River began to rise. In the late <br />1960s and early 1970s leaders at the regional and <br />national levels began to recognize the problem and to <br />seek solutions. <br /> <br />-27- <br />