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>Cxecutive Summary Tl~e Green River Discharge Monitoring Program was established in support of the Habitat Restoration and Channel Monitoring Programs for the Recovery Implementation Program for Endangered Fishes of the Upper Colorado River. The program that started in 1995 with the Mineral Bottom Gage project was extended in 1996 1 to include four addition gaging sites in the Green River. Originally, the level logger and staff gages in Canyonlands were installed in conjunction with the Flooded Bottomlands project to support field research on razorback sucker larval fish nursery habitat. In 1996, additional level loggers and strip chart recorders were installed in Mitten Park, downstream of the Yampa River confluence; at 4uray Wildlife Refuge, downstream of the White River confluence and at McPherson's Ranch in Desolation Canyon. Combined with the USGS Jensen gage, Green River USGS gage and the Canyonlands level logger, the Green River discharge was monitored approximately every 75 miles from the confluence of the Yampa River to the confluence with the Colorado River. The purpose of the program was to monitor the downstream progression of the seasonal high flow discharge hydrographs. The data base includes river stage, temperature and discharge estimates on 15 minute, 30 minute or one hour intervals. To determine the discharge, a rating curve must be established at each gaging site. The rating curve is a power fi-nction regression relationship between the river discharge and the water surface elevation. This requires a minimum of three discharge measurements and corresponding surveyed water surface elevations. At least five discharge measurements have been made at each level logger site. When the level logger is installed, a reference elevation must be established for succeeding water surface elevation surveys. Preferably, the discharge measurements are collected over a wide range of flow levels to establish a rating curve. The level loggers were located at relatively stable channel cross sections so that a shift in the rating curve was not experienced. Two of the level loggers experienced difficulties, the recorder at Mitten Park was removed by agency personnel to avoid inundation of the recorder and the level logger pipe at Canyonlands shifted. The Canyonlands data was recovered by applying a shift to the reference elevation. A Fortran computer program called Logger was written to extract the pressure head data from the level logger data base to compute instantaneous discharge from the incremental timestep water surface levels. The discharges were then average to determine a daily discharge. The daily discharges from the five gaging sites were plotted on a hydrograph together with the USGS Jensen and Green River discharges. The discharge release from Flaming Gorge Dam was plotted with the hydrographs for comparison. The 1996 Flaming Gorge Dam flow was a consistent block release for the duration of the spring runoff whose May 1 initial release coincided with ' approximate sta--t of the spring runoff as measured at Jensen. The results showed that the rising limb of the hydrograph has some floodwave attenuation due to channel and bank storage. Peak lag times are shown on both the rising and falling limbs of the hydrographs. The three level loggers produced consistent results. The recorders at Mitten Park and Ouray performed poorly. Some inconsistency is observed near the peak discharge for the Green River USGS gage. This information will be vital to predict the timing and duration of flows that open backwater fish habitat, flood larval fish bottomlands nursery habitat and maintain channel morphology. This discharge data will enhance our ability to understand water and sediment movement throughout the Green River system. The discharge data will be applied to calibrate the FLO-2D to route flows through the Green River system from Flaming Gorge Dam. The effect on discharge from flow releases from Flaming Gorge will be predicted by the model in terms of timing, duration and magnitude.