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<br />o <br />W <br />I-' <br />tv <br /> <br />INTRODUCTION <br /> <br />water-quality situation below Imperial Dam is covered in the February <br />1963 report titled, "Special Studies--Delivery of Water to Mexico," pre- <br />pared by the Department of the Interior, Bureau of Reclamation, Region 3. <br />A description of the existing projects below Hoover Dam is also included <br />in that report. <br /> <br />The authorized water-use projects and those currently proposed that <br />are included in this report bring the Upper Basin depletions to the level <br />estimated to be in effect by 1990. <br /> <br />Information on sediment loads at several key stations is included <br />to show the effect the storage reservoirs have had in decreasing sediment <br />in the Colorado River. <br /> <br />In addition to the 17 stations shown on the map as key stations, <br />quality of water, sediment, and flow data are obtained by the Geological <br />Survey at a number of other locations in the basin and published annually. <br />Quality data are also collected by the Bureau of Reclamation and other <br />agencies at additional locations for specific project purposes. <br /> <br />E. Increasing Importance of Water Quality <br /> <br />Nationwide attention has been focused on water quality in recent <br />years, particularly in the eastern states where a combination of low <br />runoff and increased pollution has emphasized the problem. The Colo-. <br />rado River thus far has not been polluted by industries to the extent <br />some of the eastern rivers have been, however, the limited supply in the <br />Colorado River necessitated that careful attention be given to quality <br />because of extensive uses by agriculture and municipalities. <br /> <br />Since each use entails some alteration of the water, close surveil- <br />lance of the quality is becoming a necessity. Most quality problems are <br />linked directly with quantity--when the quantity increases the quality <br />improves. With the increased use of water this situation is reversed and <br />the problem of maintaining the proper quality becomes critical. <br /> <br />At present none of the Colorado River water is wasted directly into <br />the ocean and the management afforded by the present system of storage <br />reservoirs permits delivery of the highest quality water possible con- <br />sidering that the supply is fully utilized. <br /> <br />Further consideration should be given to the natural sources of <br />salinity to assess the effect they have on the overall water quality <br />and quantity. For example, mineral springs along the Little Colorado <br />River contribute about 161,000 acre-feet of water and 547,000 tons of <br />salt to the Colorado River annually. <br /> <br />4 <br /> <br />