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<br />key sites in the Grand Valley and measurement of water level elevation <br />at permanent transects within the eight sites, Stream-bed cross <br />sections at these transects were measured in late fall of 1990, 1991, <br />1992 and 1993, <br /> <br />Initial findings indicate that the magnitude of spring flows in the <br />Colorado River have significantly decreased since historic times; <br />summer flows have also decreased while winter flows have increased. <br />Changes in summer and winter flows have probably not been a major <br />factor in the decline of adult squawfish and razorback sucker in the <br />upper Colorado River, However, summer flows do drop below optimum <br />levels during low-water years and instream flow rights need to be <br />secured, Changes in spring flow, on the other hand, are believed to <br />have created major changes in year-round riverine habitat for the <br />native fishes. Bottomlands no longer routinely flood and chute-channel <br />backwaters are being filled by sediment, resulting in the loss of <br />important adult spring and wintering habitat as well as nursery <br />habitat. Reproductive success of Colorado squawfish appears to be <br />correlated with magnitude of spring discharge with years of low runoff <br />resulting in poor reproductive success. The proliferation of several <br />nonnative fish species also appears to be related to low spring flows. <br />Loss of channel complexity and habitat diversity also appears to be <br />occurring through sedimentation and vegetation encroachment, Our <br />preliminary recommendations are that the frequency of spring flows of <br />high magnitude must be increased to provide a healthy ecosystem for the <br />native fish of the Colorado River. <br /> <br />Results from radiotelemetry studies and more recent habitat-mapping <br />studies indicate that pools, backwaters and especially eddies are the <br />preferred habitats of adult squawfish in the IS-mile reach during <br />summer when flows are at moderate levels, When summer flows become <br />relatively low, slow and fast runs are preferred. During winter, <br />backwaters, eddies and especially pools are preferred. Flows between <br />1,240 and 2,870 cfs provided relatively constant amounts of the <br />preferred habitat types during summer and thus 1,240 cfs is recommended <br />as a summer flow level for the IS-mile reach. During winter, 1,630 cfs <br />was found to provide the maximum combination of preferred winter <br />habitats, Depth of the preferred habitats changed with flow and <br />appeared to be limiting at the recommended flow levels only in <br />backwaters, Time series of bed cross sections in the backwaters <br />indicated that this shortfall can largely be alleviated by spring flows <br />of sufficient magnitude: high flows scour fine sediments from the bed <br />thereby increasing backwater depth. In addition, results from the <br />cross sections at channel sites provided insight on spring flow levels <br />necessary to move coarse bed material thereby cleaning gravel and <br />cobble of fine sediments. Presumably, cleaner substrate provides <br />greater invertebrate production and squawfish egg-hatching success, <br />This information allowed us to refine the earlier spring flow <br />recommendations, <br /> <br />Final reports were due in 1993. No funding was available for 1994 <br />work. Tasks for 1994 were to complete reports not finished in 1993. A <br />draft report for the IS-mile reach portion of the videography study was <br />completed in October 1994 and the final report will be completed by <br />December 31, 1994. A report on the 18-mile reach portion of the <br /> <br />2 <br />