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2 essentially sediment-free, the majority of the seiment load in this reach is obtained -from the bed resulting in a lowering of the streambed. Downstreams of the am to the confluence with the_Duchesne River, drews_noted Anew uasi-e uilibrium con ion exist with in transport t the sediment supp ied to it as shown by his sediment budget computations for the Geological Survey gauge near Jensen. Below the Duchesne confluence, Andrews described the Green as actively radin with the supply of sediment from tributary streams exceeding the ability of the Green to transport it. This information provided the starting point for the current investigations of the channel morphology history of the Green and its present-day sediment transport regime. HISTORICAL TRENDS IN CHANNEL CHARACTERISTICS Channel Width Studies of channel width of the Green were conducted for two reaches of the river by Pucherelli ([4] and [5]). These studies are included in the appendix of this report. Aerial photography covering a 73-mile reach of the Green from river mile 237 to river mile 310 (upper study reach) was obtained for the following years: 1952, 1963, 1964, 1974, 1978, and 1986. The photography was analyzed as five data sets with the photography from 1963 and 1964 comprising one set designated 1964 and presumed to reflect preregulation channel con- ditions. All photographs are black and white and of various scale: 1952-1:20,000; 1964-1:24,000; 1974-1:31,680; 1978-1:33,000; and 1986-1:24,000. A 27-mile reach of the Green in the vicinity of Green River, Utah, from river mile 94 to river mile 121 (lower study reach) was examined on photography obtained in 1952, 1974, 1981, and 1987. The 1952, 1974, and 1987 photographs are black and white, and the 1981 photos are color-infrared. The scale varied as followed: 1952-1:20,000; 1974-1:34,500; 1981-1:38,500; and 1987-1:26,000. Each photograph was fitted with a mylar overlay on which the river channel was delineated by drawing the high-water embankment lines and vegetated islands. Following photointerpretation, the delineated polygons were transferred to a 1:24,000 map base and the length of each map reach of river was determined. The data was then digitized into a Geographic Information System using Geographic Entry System software. Channel area for each data set was tabulated and an average channel width computed using the measured channel length for each data set. This channel width data is presumed accurate to within 20 feet. Average channel width for the upper study reach was estimated to be 700 feet in 1952, 710 feet in 1964, 667 feet in 1974, 669 feet in 1978, and 683 feet in 1986. Average channel width for the lower study reach was estimated to be 473 feet in 1952, 475 feet in 1974, 453 feet in 1981, and 459 feet in 1987. About 40 percent of the channel narrrowing was attributed to island attachment to the banks. These average channel width data are comparable to the average channel widths reported by Andrews. For the upper study reach, Andrews measured channel