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Table 4. - Green River reach 2 channel morphology comparisons <br />for predam (1952), and postdam (1974, 1981, and 1987) <br />periods. <br />Site 1952 1974 1981 1987 <br />465 km - 509 km <br />area (ha) 629.37 630.99 601.83 610.34 <br />width (m) 144 145 138 140 <br />Note: Site descriptions are distances downstream from <br />Flaming Gorge Dam. <br />Mean Annual Bed-Material Load <br />The bed-material load discharge rating curves were used with the mean daily flow data for <br />gauges 09261000 and 09315000 for 1965-87 to compute estimates of mean annual bed-material <br />at sites A, B, C, and the downstream gauge. At sites A and B, the mean annual bed-material <br />load for this period was 1343 000 tonnes/year. These estimates are based upon the mean daily <br />flow data collected at gauge 09261000 and the suspended sand load rating curve developed for <br />the entire gauge history. <br />At site C, the mean annual bed-material load was 2 640 000 tonnes/year. The adjusted mean <br />daily flows from gauge 09315000 were used in this estimate. The suspended sand load rating <br />curve for gauge 09307000 was used with the adjusted discharges. <br />At gauge 09315000, the mean annual bed material load was 2 803 000 tonnes/year. This <br />estimate was based upon the mean daily flow record and the suspended sand load rating curve <br />for the gauge. For the Duchesne River, the suspended sediment rating curve for gauge <br />09302000 was used with the mean daily flow record for this gauge from 1965 to 1987 to <br />compute the estimate of mean annual suspended load. Assuming about 27 percent (based upon <br />six measurements from 1980 to 1986) of the suspended load was sand, the annual sand load <br />estimate for the Duchesne River was 42 000 tonnes/year. For the White River, the <br />flow-duration data for the gauge near the confluence from 1974 to 1986 were used to derive an <br />estimate for suspended sand load discharge of 925 000 tonnes/year. <br />Bed-Material Load Mass Balance <br />Table 5 presents the bed-material load mass balance for the reach of the Green River from 164 <br />to 468 kilometers downstream from Flaming Gorge Dam. In reach 1, sites A and B showed <br />equal sand loads because both were developed from similar gauge records. Between 150 and <br />175 kilometers below the dam, the Green River gained 129 7000 tonnes per year of <br />bed-material load. The White and Duchesne Rivers contribute 967 000 tonnes/year to this <br />reach. The difference, 330 000 tonnes per year, represented about 12 percent of the mean <br />annual sand load at site C. Although no bedload information was available for the White River, <br />streams of similar characteristics often have a significant bedload component ranging from 10 <br />to 35 percent of the total suspended sediment load (Strand and Pemberton, 1982). Assuming a <br />10-percent bedload correction factor for the mean annual suspended sediment load of the White <br />9