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<br />e <br /> <br />e <br /> <br />e <br /> <br />Using the regression model and an annual stream discharge of 4,000,000 <br />acre-feet, annual sus~nded-sediment load is Iredicted to be about 7,860,000 <br />tons and could range from 3,400,000 tons to 12,100,000 tons at a 9O-percent <br />confidence level. It is possible. therefore. that any estimate USing this <br />model could have about a SO-percent error at a 9O-percent confidence level. <br /> <br />The variability of the annual suspended-sediment loads at station <br />093lS000 is obvious. '!he localized nature of precipitation and the variations <br />in geology in the basin upstream from the gaging station contribute to this <br />variability. Numerous tributaries enter the Green River upstream from the <br />station. and many of these tributaries. carry large amounts of sediment during <br />~riods of high runoff, especially rainstorm runoff. In general, runoff from <br />these tributaries may substantially increase the annual suspended-sediment <br />load of the Green River but may have only a small effect on the annual <br />streamflow. For example. the 1975-79 mean annual sus~nded-sediment load for <br />the White River at its mouth was 1,759,000 tons (Seiler and Tooley, 1982, p. <br />1), and the mean annual streamflow was 466,420 acre-feet. For the same <br />period, the mean annual suspended-sediment load at station 09315000 was <br />6,784,000 tons, and the mean annual streamflow was 3,ro5,000 acre-feet. '!he <br />White River contributed about 26 percent of the annual suspended load but only <br />about 12 percent of the annual streamflow of the Green River during this <br />period. Neff (1967, P. 236) reports that in arid regions more than 60 percent <br />of the long-term sediment yield is associated with runoff having recurrence <br />intervals exceeding 10 years. <br /> <br />SUMMARY <br /> <br />During 1930-82, the mean annual suspended-sediment load at gaging station <br />09315000, Green River at Green River, Utah, was about 15,630,000 tons, ranging <br />from 1,780,000 tons during 1934 to 43,400.000 tons during 1937. The daily <br />load ranged from 54 to 2,230,000 tons. <br /> <br />Analysis of the suspended-sediment records indicates the aco..tracy of the <br />records is fair prior to 1945 and good for the remaining period of record. <br />'!he records after 1945 reflect the use of improved sampling equi~ent. <br /> <br />A double-mass curve showed changes in relationship between annual <br />suspended-sediment load and annual stream discharge. The first change <br />occurred approximately between water years 1944-46 and coincides with a change <br />in sampling equipment. The U.S. D-43 suspended-sediment sampler was first <br />used at this site during October 1945 (1946 water year). The second change, <br />which occurred approximately between water years 1963-65, coincides with the <br />completion of Flaming Gorge Darn during November 1962 (1963 water year) <br />upstream from the gaging station. The mean annual suspmded-sediment loads <br />were reduced by about 35 percent at station 09315000 after the completion of <br />the dam. <br /> <br />14 <br />