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<br />. <br /> <br />. <br /> <br />In order to understand how the river responds to seasonal variations in discharge and <br />sediment load, we have established a number of study sites in the reaches described above. Three <br />of our study sites are 'backwaters' formed where flow splits around a bar or island into a side <br />channel. Compared to the main channel, backwaters are characterized by lower flow velocities, <br />lower depths and higher water temperatures, and thus, they are considered to be important habitat <br />for the endangered fishes (Stanford, 1994). The backwater study sites consist of a series of <br />surveyed cross sections running from the upstream entrance of the side channel to the downstream <br />exit where the flow rejoins or backs up from the main channel. These cross sections are arrayed <br />such that we can observe whether there is scour or fill at the entrance and exit, which are the two <br />key points governing fish access and the flow of water and sediment through the side channel. <br />These sites have been surveyed repeatedly over the past 3 years. <br />To place these site-specific observations into a somewhat broader context we separately <br />measured a series of main channel cross sections, proceeding at I-mile intervals from Palisade to <br />the Westwater boat launch, river miles (RM) 185 to 128. Cross sections in the 15- and 18-mile <br />reaches (RM 185 to RM 153) were surveyed in 1993; cross sections in the Ruby and Horsethief <br />Canyon reaches (RM 152 to RM 128) were surveyed in 1994. Results of this and related work are <br />described in two previous reports (Van Steeter and Pitlick, 1994; Van Steeter et al., 1995). <br />The present report updates this work using data obtained in late summer of 1995 following <br />a period of high snowmelt runoff. Above-average precipitation and cool weather in the spring of <br />1995 increased snowpacks in the upper Colorado River basin dramatically- up to 300% of normal <br />in some areas- and the ensuing runoff was characterized by relatively high flows of long duration. <br />At the request of the U.S. Fish and Wildlife Service (USFWS) and the Bureau of Reclamation <br />(USBR), we re-surveyed some of our field sites to assess the geomorphic effects of these high <br />flows. Cross sections at the 3 backwater study sites were surveyed in their entirety. In addition, <br />we re-surveyed 12 main channel cross sections. The following discussion provides further details <br />of the 1995 hydrograph and a summary of our observations of channel changes at selected sites. <br />Additional cross section data not discussed below are presented in an appendix. <br /> <br />3 <br />