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diversion dams near Palisade, Colorado, thus management and monitoring of conditions within <br />the 15-mile reach is an important priority. <br />Streamflows into the 15-mile and 18-mile reaches are regulated by a series of reservoirs <br />and diversions. At present there are 25 reservoirs with a storage capacity greater than 5,000 <br />acre-feet (6.2 x 106 m3) upstream of the Colorado-Utah state line [Liebermann et al., 1989]. <br />These reservoirs are distributed throughout the upper basin; individually, they are not large in <br />comparison to some other dams in the Colorado-Green River system (e.g. Flaming Gorge or <br />Glen Canyon), but collectively they have the capacity to store the equivalent of about half the <br />annual flow volume of the Colorado River at the Colorado-Utah state line [Pitlick et al., 1999]. <br />Reservoir construction and operations have altered the timing and magnitude of peak flows in the <br />15- and 18-mile reaches significantly. Since 1950, annual peak discharges of the Colorado <br />River, and its major tributary the Gunnison River, have decreased by 30-40% [Pitlick et al., <br />1999]. In addition to altering peak flows, upper basin reservoirs store spring runoff which is <br />diverted later in the year to municipalities and projects east of the continental divide. Diversions <br />remove an average of about 14% of the native flow of the Colorado River annually, although in <br />some years as much as 30% of the flow is taken out of the basin [Osmundson et al., 2002]. <br />The primary geomorphic effect of water-management activity in the Colorado River <br />basin has been to reduce the sediment-transport capacity of the river. Analysis of suspended <br />sediment data from gauging stations operated by the U.S. Geological Survey (USGS) indicates <br />that surface erosion of sedimentary rocks in areas immediately upstream of the key reaches <br />contributes a large proportion of the sediment carried by the Colorado River [Iorns et al., 1965; <br />Liebermann et al., 1989; Pitlick and Cress, 2000]. Most of the reservoirs in the upper Colorado <br />River basin are well above these areas, and therefore have little effect on the amount of sediment <br />2