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to 65 percent. A flow-duration curve expresses the probability that a given daily discharge will be equaled or exceeded over a period of years. Shape of the flow-duration curve is dependent on the frequency distribution of daily discharges. Rivers with equal volumes of annual streamflow, but different di stributions of daily di scharges, wi 11 have different flow-duration curves. Each flow-duration curve in figure 9 represents only one of numerous possible discharge distributions for a given annual streamflow. Annual total sediment loads transported in scenarios of reduced stream- flow (fig. 9) were computed by the flow-duration, sediment-transport-equation method described previously.' These annual sediment loads are presented in the rows of table 6. The columns represent assumed annual sediment supplies. Streamflow scenario A and sediment supply scenario 1 summarize prevailing conditions in the Oee,rlodge Park reach. Annual streamflow of 1.47 million acre-ft/yr, with a streamflow frequency distribution represented by the flow-duration curve in figure 6, transports a total sediment load of 2.0 million ton/yr, of which 0.8 million ton/yr is sand-size or larger (table 5). Equil ibrium conditions in the Vampa River at Oeerlodge Park indicate no surplus or deficit of sediment over a period of years. Therefore, the prevailing supply to Oeerlodge has been estimated to be 2.0 million ton/yr. Combinations of annual streamflow and annual sediment supply in scenarios AI, 82, C3, 05, E6, and G7 of table 6 result in little or no sediment surplus or deficit. The river, in these scenarios, attains an equilibrium in sediment supply and transport on an average annual basis, but in all scenarios except AI, the occurrence of high streamflows is reduced (fig. 9). The scenarios presented in this analysis assume a constant relation between sediment dis- charge and water discharge; however, if large changes occur in the flow regime, the sediment diSCharge-water diSCharge relation also could change. -* Reductions in peak streamflow will be accompanied by changes in channel form at Deerlodge Park (Mackin, 1948; and Leopold and Maddock, 1953) and riparian vegetat ion tl1roughout Di nosaur Nat i ana 1 Monument (Potter and others, 1983), even though the sediment budget may remain in equilibrium. Other possible combinations of annual streamflow and annual sediment supply are sl10wn in table 6. Annual total sediment loads were computed using the flow-duration curves in figure 9. In several instances, the annual surplus or deficit of sediment in Deerlodge Park is significantly greater than zero. Under these scenarios, problems with channel aggradation or degradation are more severe and occur over a short period of time. Annual sediment transport exceeds annual sediment supply in the scenarios in the upper right part of table 6. Varying degrees of sediment budget deficits result from these scenarios. Sediment budget surpluses result from supply-transport scenarios shown in the lower left part of table 6. As an example, scenarip B-1 represents a situation that could exist if the prevailing annual sediment supp ly and annual streamflow were unchanged, but the durati on of Yamlla River flows was altered to the degree that has occurred at the Jensen gage located leG mi dC\v'nstrea:n fr~0m FL1ming Gorge Reservoir on the Green River (fig. 8). Annual sediment supply remains 2.0 million ton/yr, but annual sediment trans- port has been reduced to 1.9 million ton/yr, resulting in a D.l million tcn/yr surplus of sediment at Deerlodge Park. 28