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1 the Jensen Bridge in order to represent a cover composed of thermally grown sheet ice and juxtaposed frazil pans. From the Jensen Bridge up to the leading edge of the ice cover near Razor Island, an ice thickness of 0.8 ft with a roughness of 0.03 was used, representing an ice cover composed mainly of juxtaposed and slightly shoved frazil pans and floes. Table S lists bed roughness, ice thickness, and ice roughness used in the calibrated ice model. Simulated water surface elevations for a steady dischazge of 2440 cfs are also listed. The final column indicates the source of the cross-sectional geometry (S indicates surveyed and E indicates estimated from topographic mapping). Cross-section location and type are also shown graphically in Figure 21, along with ice cover extent. The UNET model was calibrated to observed stage hydrographs at the seven locations listed in Table 6 and indicated in Figure 21. Simulated and observed stage hydrographs are compared in Figures 22 through 28. Calibration results were generally quite good with a few exceptions. The measured stage hydrograph at the Chew Bridge (RM 316.3) is more peaked than the simulated stage hydrograph for the Jensen gage (RM 316.6) (Figure 22}, possibly because the channel is more narrow at the bridge than at the gage location upstream. Similarly, the observed hydrograph at the Jensen Bridge (RM 302.3) is more peaked than the simulated result (Figure 24). The simulated and observed hydrographs agree quite well in terms of total wave height and timing of the peak at Dinosaur Bend (RM 307.1; Figure 23), Bonanza Bridge (RM 294.0; Figure 25}, and Horseshoe Bend (RM 279.4; Figure 26). At Ouray Refuge (RM 254.6; Figure 27) and Ouray Bridge (RM 248.0; Figure 28), the timing of the first hydrograph peak and the total wave height are simulated fairly well. The simulated falling limbs of these hydrographs are less steep than the observed falling limbs, however. Resolution may be a problem in this part of the river because observed wave height is small, on the order of 0.3-0.4 ft. Also, these downstream sites are more than 60 miles from the location of the observed inflow hydrograph at the Jensen gage (RM 316.6), the upstream boundary of the model. River Hydraulic Conditions: Comparison of Steady and Unsteady Flows Two alternate release schedules were modeled. Under the first schedule, the releases were held constant for a number of days. In the second schedule, the releases were varied using a pattern typical of hydropower generation at Flaming Gorge Dam. Using the unsteady flow model described above, the hydraulic parameters of flow depth, flow velocity and Froude number were estimated throughout the Green River study reach. The results for the steady flow are listed in Table 7. At the end of the steady flow period the releases from Flaming Gorge Dam were fluctuated in a typical peaking hydropower pattern. The resulting flows passed through the study reach in a series of peaks and troughs. Hydraulic parameters were estimated for the first peak (Table 8), the first trough (Table 9), the lowest recorded trough (Table 10), and the highest recorded peak (Table 11). Figures were prepared to compare the hydraulic parameters of flow depth (Figure 29), velocity (Figure 30), and Froude number (Figure 31). It can be seen that the variation in depth between the steady and the fluctuating flows was minimal downstream of River Mile 280 (+/- 0.1 foot), moderate between River Mile 280 and 300 (+/- 0.25 foot), and lazge between River Mile 300 and 316 (+!- 1.0 foot). The variation in flow velocity between the steady and the fluctuating flows is minimal downstream of River Mile 302 (+/- 5°Io), and 16 1 ii i~