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VI. Division of Water Resources Administration The State of Colorado Division 5 Water Resources 1999 Annual Report is not yet available. When it is finalized, the report can be found on the State Engineer's Web Site at: http://water.state.co.us/default.htm VII. Fish & Wildlife Service Monitoring Recent biological and geomorphology studies have documented changes in physical processes and native fish populations related to the modification of the natural snowmelt hydrograph due to the construction of reservoirs upstream of the Colorado-Utah State line. These changes have reduced the ability of the Colorado River to move sediment and rework the river channel (Pitlick 1999). It is generally accepted that these reservoirs have altered stream flows of the Colorado River and have caused changes in the amount, diversity and quantity of habitat used by the endangered Colorado River fish. In compliance with the Recovery Program RIPRAP, monitoring of embeddedness of gravel and cobble substrates in the upper Colorado River was initiated. Twelve measurements were taken at each of 15 sites (eight in the 15-mile reach; seven in the 18-mile reach) on seven dates in 1996 (three during runoff; four during baseflow) and five dates in 1997 (three during runoff, two during baseflow). Rock sizes were generally larger lower in the channel at base flow elevations than higher in the channel margin inundated during runoff. Additionally, average rock size was slightly larger in the 18-mile reach than in the 15-mile reach, but only at base flow locations. Spring runoff flows in both the 15- and 18-mile reaches were sufficient in both years to mobilize the bed in many areas. In addition, runoff flows during 1995 (prior to sampling) produced widespread mobilization of the bed. Average rock sizes changed significantly between 1996 and 1997 at several of the sampling sites. Mean depth to embeddedness (distance from the top of rocks in the surface layer down to the point where rocks are embedded in fine sediment) ranged from 80 to 171 mm; the adjusted mean of the samples was 125 mm in 1996 and 123 mm in 1997. The mean number of `free rocks' (those making up the layer above the level of embeddedness) ranged from 1.1 to 4.3; the adjusted mean was 1.9 rocks in both years. Riffles had slightly greater depths to embeddedness than did runs. For other comparisons, depths to embeddedness were found to be similar between the15- and 18- mile reaches, between 1996 and 1997, and between runoff and baseflow periods. Rates of sedimentation were low during summer and fall following runoff and depth to-embeddedness remained fairly constant through the base flow period. The two years of initial sampling represents a period of time when both reaches were freshly cleaned of fine sediment and the data should provide a good baseline for future monitoring. In addition, the USFWS also conducted its Standardized Monitoring Program. Benefits of coordinated operations are discussed in the standardized monitoring efforts. In addition, on February 13, 1999, the FWS provided a report on releases from Ruedi Reservoir, which included discussion of the benefits of peak flows. 12