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. . Attachment to Proposal Aspinall-C: Aspinall Studies -- Evaluation of Gunnison River flow manipulation upon availability and quality of nursery habitat for Colorado squawfish in the Colorado River. Lead Agency: U. S. Fish and Wildlife Service (USFWS) Submitted by: Frank Pfiefer U.S. Fish and Wildlife Service 529 25 1/2 Rd. Suite B 110 Grand Junction, CO 81505 John Pitlick and Mark Van Steeter Department of Geography, Box 260 University of Colorado Boulder, CO 80309-0260 Date: April 29, 1993 I. Title of Proposal Changes in channel morphology of the upper Colorado River II. Relationship to Recovery program/Ranking Factors The loss or alteration of backwater habitat appears to have contributed significantly to the decline of native fishes in the upper Colorado River basin. Results from our recent analysis of aerial photographs taken between 1937 and 1986 indicate that there has been some reduction in the overall width and complexity of the Colorado River within the l5-mile and l8-mile reaches. Presumably these changes are associated with reductions in peak flows due to water-resource development in the upper basin, and with bank stabilizing activities (levees). Areas of channel complexity and backwater habitat are, however, still found within these reaches, and within the Ruby-Horsethief Canyon reaches, but efforts to recover these fish will require more detailed information on how backwater areas change in response to seasonally varying flow and sediment transport patterns. Recent recommendations for flows in the IS-mile reach of the Colorado River are based on the assumption that higher flows are needed to maintain backwater areas. It is not clear exactly how high these flows need to be or how long they should last. Insight into this problem can be gained by monitoring changes in channel morphology at specific sites over the entire period of spring and summer runoff, and by systematically measuring rates of sediment transport and deposition. It is known from field surveys by FWS biologists that backwater sites change from year to year, but it is not clear how these changes are related to specific flow and sediment transport regimes. In spring 1993, we selected 4 field sites and set up a surveyed network of channel cross sections to detect changes in side channels. We expect there will be changes at these sites, particularly if runoff in 1993 is above average. We propose to continue monitoring these sites through FY-94 to determine how side channels develop over time. In addition, we propose to expand the scope of work begun in FY-93 to 1