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4 1 i SUMMARY A total sediment budget was constructed for the Deerlodge Park to Mathers Hole reach of the Yampa River to investigate hydrographs necessary to maintain an equilibrium condition in the reach and the load delivered to the Green River, given various hydrographs at Deerlodge Park. The Deerlodge Park reach may be used as a 'barometer' in gaging changes in water and sediment distribution. Minimizing channel adjustments in the Deerlodge Park area compared to historical conditions should minimize changes elsewhere in the Yampa Canyon, which are generally considered adverse from an endangered species viewpoint. Rating curves corrected for bias at Deerlodge Park combined with the 'historic' II streamflow record estimated mean annual total sediment load as 2.60 million tons. Previous estimates using curves uncorrected for bias included 2.04 million tons (Elliott, 1984) and 2.0 million tons (Andrews, 1978). These previous estimates used different periods of record, and Andrews had to estimate bedload transport since measured values are unavailable at the Lily -and Maybell stations. The running balance of the sediment budget program can be used to quantify surplus and deficits in localized sediment deposition in Yampa Canyon as a result of changing streamflow frequencies, durations, and sediment loads. The budget uses daily flow data and sediment rating curves for this purpose. Total sediment rating curves were used in the program, bedload or other curves may be substituted. Mean monthly flow data may be used to synthesize daily flow records to quantify project impacts using the program. The program has applicability in evaluating specific water resource development projects and their effects upon sediment transport and localized deposition within the Yampa Canyon. Analysis of annual streamflow volumes revealed the 1941-1986 water year period had approximately the same number of high, low and average years as the 1921- 1986 water year period. The 1941-1986 water year period was used within the budget program because it is probably more representative of the current morphology than earlier periods (Elliott, 1984). Seasonal transport of total sediment was observed using the running balance of the reach for the historical record, a baseline record, and for the Juniper Project record. Peak flows were then reduced to find the 'break points' at which an equilibrium in total sediment transport was not obtained for the historical 1941-1986 water year period. Peak flows were reduced using two representative worst case water development scenarios; 1) reduction of peak flows and redistributing the volume to peak power generation months, and 2) reduction of peak flows, additional depletions for consumptive use, followed by redistribution of flows for peak power generation. A third method reduced the peak flow periods without redistributing the flow volume, this maintained the historical baseflow levels.