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Duration-of-flow plots (fig. 6) for the photographic intervals for mean daily flow data from gauge <br />09261000 in reach 1 illustrate a different pattern for mean daily flows exceeding 310 cubic <br />meters per second. Flows less than 310 cubic meters per second occurred at the same frequency <br />during 1964-78 as the other periods. The curve for the 1952-64 data differs from curves for the <br />later periods below 140 cubic meters per second, yielding a lower flow for a given percent of <br />time. A flow of 310 cubic meters per second was exceeded about 9 percent of the time during <br />1964-78. <br />Analysis of mean daily flow data for gauge 09315000 in reach 2 indicates that flows were <br />greater for a given percent of time during 1982-87 than during the earlier portion of the <br />postreservoir period (1963-81). The duration-of-flow curve representing 1982-87 resembles <br />those curves from the prereservoir era (1942-52 and 1953-62) for infrequent flows which <br />occurred less than 2 percent of the time (fig. 7). <br />Effective Flow <br />For his post-impoundment period,. 1966-81, Andrews (1986) defined the effective flow at gauge <br />09261000 to be 326 cubic meters per second and the effective flow at gauge 09315000 to be 581 <br />cubic meters per second. Our effective flow estimates for 1965-87 are: 337 cubic meters per <br />second for sites A and B, 544 cubic meters per second at site C, and 569 cubic meters per second <br />at gauge 09315000, which are comparable to Andrews' estimates. <br />For the Green River, the effective flow is an index of a broad range of discharge that carries <br />significant amounts of bed-material-sized sediment. Approximately 80 percent of the <br />bed-material load is transported over the discharge ranges at each site shown in table 6. These <br />ranges cover about 90 percent of the flows measured at the two gauges during the <br />post-reservoir period. <br />Table 6. - Effective flow ranges for <br />the Green River, 1965--87. <br />Site Flow range, m°/s <br />A 48.1 to 560.7 <br />B 48.1 to 560.7 <br />C 60.9 to 826.9 <br />Gauge 09315000 59.5 to 845.3 <br />DISCUSSION <br />Channel Width <br />The installation of Flaming Gorge Dam has measurably narrowed the Green River channel. <br />Before installation of the dam, the river was said to be in quasi-equilibrium with respect to <br />sediment load (Andrews, 1986). Our comparison of channel areas and widths between 1952 and <br />1964 confirms this statement (table 2). In study reach 1, channel adjustment was generally <br />11