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12 <br />Also, the bed topography that causes areas of slack water is constructed by <br />the few largest discharge-days of each year. Adjustment of the channel at <br />lower discharges, in the range of 2,000 ft3/ to 6,000 ft /s, does not appre- <br />ciably affect bed topography of the slack water areas associated with midchan- <br />nel sand bars (Andrews, pers. comm., 1989). <br />The results of this model study along with the trends noted for channel width <br />since regulation and the sand-load mass balance of the Green indicate a system <br />whose bed forms adjusts rapidly to changes in discharge and has reached an <br />equilibrium in long-term sediment transport. The potential for future channel <br />changes still exists within the realm of this "new" equilibrium as evidenced <br />by the channel widening that was experienced during the high flow years of the <br />early 1980's. Such changes are short-term (occurring and persisting on the <br />order of 1-10 years) adjustments in the equilibrium of the river. They are <br />responses in the channel to changes in the discharge regime that alter the <br />average form for a period of years but help define the equilibrium conditions <br />found over a longer (10-100+ years) time period [171. <br />The channel conditions presently found in the Green from near Green River, <br />Utah, upstream to near Jensen, Utah, should remain relatively unchanged in the <br />future barring changes in either sediment or water supply in the basin. Any <br />changes in the amount of bed material load or change in water discharge pat- <br />tern through the study reach could evoke channel changes according to Schumm's <br />relationships described earlier. At present, these channel changes can only <br />be described qualitatively along with the effects upon fish habitat. <br />SUMMARY <br />The response of the Green River channel to hydrologic changes induced by the <br />presence of Flaming Gorge Dam was studied using comparative analysis of the <br />channel from historical aerial photography, published sediment and flow <br />records, and sediment data collected during 1986-1988. The emphasis of this <br />study was the present-day sediment transport regime of the Green and the <br />potential for future channel changes. <br />The Green in the upper study reach from river mile 237 to river mile 310 <br />apparently reached a new equilibrium in terms of channel width between 1964 <br />and 1974. The downstream reach, from river mile 94 to river mile 121 reached <br />a new equilibrium between 1964 and 1981. Subsequent high flows have resulted <br />in an increase-in average channel width at both locations as measured in 1986 <br />and 1987. <br />' Bed-material sediment transport in the Green has attained a quasi-equilibrium <br />at the present time with th ransporting just the load supplied to it <br />X from the basin. This was( etermined or the reac from Green River, Utah, at <br />p ???l5 diver mile 120 to river mile 310 near Jensgn. Utah. Data from 12 Geological <br />t?t1? _u ?d, urvey gauges on t e Green and its primary tributaries as well as data <br />COQ. collected for this study were used in this determination. <br />7 <br />At the former Geological Survey gauge near Ouray, Utah, both width and depth <br />changed following dam closure. These changes indicate a complex channel