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complete within 12 years of dam installation and little narrowing was noted after 1974. Channel width for reach 1 decreased about 6 percent between 1964 and 1974 from 217 to 204 meters. Andrews (1986) reported a much larger decrease of 13 percent, from 214 to 186 meters, for a shorter reach of the river downstream from gauge 09261000 between 1964 and 1978. Our study found a decrease similar to that reported by Andrews only for a portion of reach 1 from 238 kilometers to 256 kilometers downstream from Flaming Gorge Dam. Andrews' measurements were based on only 15 cross sections in a reach about 100 kilometers long, which probably accounts for the discrepancy. Andrews (1986) predicted a new quasi-equilibrium channel width of about 160 meters for the reach downstream from gauge 09261000. He projected that complete channel width adjustment would take about 30 years at the postreservoir effective discharge. Our results indicate that the majority of channel narrowing was complete by 1974 in the upper reach because average channel width did not change appreciably between 1974 and 1978 (table 2). No discernible difference existed in the magnitude of channel narrowing between alluvial and confined reaches. The best fit of the data in table 3 was found to be a power function model equation (y = axb) in which a = 208.5 and b = -0.0132. A moderate correlation coefficient of -0.66 was calculated for these data. Using this model can account for about 45 percent of the variation in measured channel width. The predicted channel width (201 meters) at 15 years after reservoir completion does not differ appreciably from the predicted width of 199 meters after 30 years. A slight increase in average channel width occurred in study reach 1 between 1978 and 1986. The duration-of-flow analysis for gauge 09261000 shows a corresponding increase in the duration of flows greater than 310 cubic meters per second during the same period. A similar response is apparent in the channel widths reported for reach 2 between 1981 and 1987. This evidence indicates that the-majority of channel widening in both reaches occurred during the high flow years of 1983, 1984, and 1986, when flows in the Green River resembled prereservoir conditions. Andrews (1986) reported the most significant channel narrowing in this study reach of the Green River occurred where a side channel had filled with bed material and the mid-channel bar had become attached to the bank We estimate that 46 percent of the channel area lost between 1964 and 1974 was related to increases in the number of islands and island size and the loss of side channels that filled with bed material. The island area decreased slightly from 1974 to 1986, which accounts for the slight increase in channel area during this period. The loss of side channels from 1964 to 1974 may represent a significant loss in potential backwater habitat associated with these areas. Reduction in the frequency of flood discharges may encourage vegetation encroachment which stabilizes deposits, traps sediment, and reduces active channel erosion (Petts, 1984). Our data shows a decreasing rate of channel narrowing following dam closure. A subsequent survey by Lyons (1990) of the reach of the Green River studied by Andrews and Nelson (1989) revealed channel shape changes since 1986. However, 12