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<br />. <br /> <br />. <br /> <br />. <br /> <br />o <br />c.c <br />N <br />0) <br /> <br />OTHER WATER QUALITY ASPECTS (Continued) <br /> <br />For example, in 1957 the suspended sediment load of the Colorado <br />River at Lees Ferry, Arizona, gaging station was recorded at 143 million <br />tons (130 million tonnes). This sediment was detrimental to water <br />diverters for consumptive use as well as to high-type fishery and other <br />recreational uses. The construction of Fontenelle, Flaming Gorge, <br />Curecanti Unit, Navajo, and Glen Canyon Dams has produced dramatic <br />changes in the sediment load transported by these streams. For example, <br />the relationship between the water and sediment flows at Lees Ferry <br />during the 1948-66 period is illustrated in Figure 5. In 1959 the <br />cofferdam utilized in the construction of Glen Canyon Dam was finished <br />and diversions began through the tunnels. Sediment was deposited behind <br />the cofferdam in 1959 and 1960 at a sufficient rate to gradually fill <br />the cofferdam lake with the result that by 1962 the annual sediment load <br />at Lees Ferry had increased to 67 million tons (61 million tonnes). <br />This load dropped to 2.2 million tons (2.0 million tonnes) in calendar <br />year 1963 with the closure of Glen Canyon Dam and initial storage in <br />Lake Powell. Lake Powell and other Colorado River Storage Project <br />reservoirs are now effectively trapping and storing almost all of the <br />sediment originating in the Upper Colorado River Basin. Lake Powell and <br />the other Upper Basin Reservoirs trap approximately 75 to 80 percent of <br />the sediment that normally would flow into Lake Mead. By storing the <br />sediment in the Colorado River Storage Project reservoirs, the streams <br />immediately below the dams have been changed to relatively clear trout <br />water fisheries as well as desirable boating and recreational areas. <br />Daily sampling at Lees Ferry was discontinued beginning in water year <br />1966 because of the lack of sediment. <br /> <br />A comparison of the major portion of the in flowing sediment and <br />flow into Lake Powell with the outflow was made by plotting for a number <br />of years the sum of the sediment loads and flows of the Colorado River <br />near Cisco, San Juan River near Bluff, and Green River at Green River, <br />Utah, stations. This is shown in Figure 6 as compared to'the outflow as <br />shown by the Lees Ferry record in Figure 5. <br /> <br />107 <br />