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4 recorded in 1984, 40,000 ft3/s, is the largest reported for the entire gauge history, These data were separated into three time periods, 1953-1964; 1965-1978: and 1979-1986 corresponding to the photographic intervals. An ana- lysis of covariance showed no statistically significant difference (at the 0.05 level of significance) in the means of the annual peak flows for these intervals. A similar analysis for the annual peak flow data for the Geological Survey gauge at Green River, Utah, (see figure 4) indicated no sta- tistically significant difference in the means of these data. The peaks at Green River, Utah, were separated into three periods: 1953-1974, 1975-1981, and 1982-1987. Figure 5 is a plotting of the flow-duration curves for the Green near Jensen gauge data for the photographic intervals. The 1964-1974 and 1974-1978 interv- als were combined since the flow-duration curves for these intervals are nearly identical. The flow-duration curve for the 1964-1978 period differs from those for the other two time periods for discharges exceeding 11,000 ft3/s was yielding a lower flow for a given probability of occurrence. The curve for the 1952-1964 data differs from those for the later time periods below 5,000 ft3/s; yielding a lower flow for a given probability of occurrence. A flow of 11,000 ft3/s was exceeded about 9 percent of the time during 1964-1978. Flow-duration analysis at the Green River, Utah, gauge (see figure 1 for gauge location) indicates that flows were greater for a given probability of occurrence during 1982-1987 than during the earlier portion of the post- reservoir period (1963-1981). The flow-duration curve representing 1982-1987 is very similar to those curves from the prereservoir era (1942-1952, 1953-1962) for very infrequent flows which occur less than 2 percent of the time (see figure 6). Thus, the increase in channel width between 1978 and 1986 in the upper study reach is a response to the increased occurrence of flows greater than 11,000 ft3/s experienced during that interval relative to the flow history immediately following regulation. A similar response is apparent in the chan- nel widths measured for the lower study reach. There, the increase in channel width occurs between 1981 and 1987, suggesting the majority of channel widening in both reaches occurred during the high flow years of the mid-1980's. Again, the flow conditions of the 1980's are more similar to pre-reservoir conditions than the earlier postreservoir period. SEDIMENT TRANSPORT ANALYSIS Sediment Data Collection Sediment data collection for this study began in 1986 at three locations within the study reach. At the upstream end of the each near the Dinosaur Quarry at river mile 308 15 samples were collected t discharges ranging from 1,081 ft3/s to 10,328 fti/s. At the Ouray National Wildlife Refuge (river mile 255, 18 samples were collected over a range ofddischarge from 1,107 ft /s to 10,787 ft3/s. Below the confluences Of the White and Duchesne Rivers with the Green, a third location at river mill 239 was sampled 16 times over the 2,649 ft3/s to 13,892 ft3/s range.