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, .. . APPENDIX f -''': IMPACTS OF THE 3-5 NOVEMBER 1997 31,000 cfs TEST FLOW Introduction The Bureau of Reclamation and the Grand Canyon Monitoring and Research Center conducted ,a test of a "Habitat Maintenance" style flow from Glen Canyon Dam on 3-5 November 1997. The flow peak reached approximately 30,600 cfs for this 2-day test. This memo outlines the impacts of that flow event on resources through Grand Canyon. Phvsical Resource ImDacts GCMRC coordinated pre- and post-event videography of the river corridor, and those images are being examined for backwater habitat changes. Using the methods of Pam ell et al. (1996), detailed topographic surveys of35 sand bar monitoring sites were conducted immediately following the November 1997 test flow by members of the Northern Arizona University Depamnent of Geology sand bar studies office. Information gathered from these surveys is compared to previous surveys conducted in August 1997 in order to quantify sand bar change. Based on this preliminary date, the November test flow benefitted the sediment resources by depositing sediment at higher elevations. The higher elevation areas of sand bars contain critical riparian habitats that Ar.. of particular interest to management .agencies. following the 199645,000 ft'/s test flow, erosion has steadily decreased the volume of sediment .:-) contained in the upper elevations of sand bars. Preliminary results show that the November 1997 test flow '." slightly increased the volume of sand bars (above the 20,000 ft'/s stage elevation), calculated as a percentage of the pre-1996 test flow, from 87% to 91 %. High flows above powerplant capacity are the only means by which the volume of the upper levels of sand bars can be maintained. The U.S. Geological Survey (G. Fisk, D. Topping, D. Rubin and S. Wiele) monitored mainstream streamflow and suspended sediment at the Lee Ferry, Above Little Colorado River, Grand Canyon and Diamond Creek gauges one/day before, during and after the flow event. Bedload sampling was conducted int he mainstream and in eddies at selected sites following the high flow. Bar sedimentology, grain size, deposit thickness was conducted with the NAU effon immediately following the high flow. Biolo~ical Resource Impacts On November 6,1997, the Arizona Game and fish Depanment (AFFD) surveyed cobble bars in the Lee Ferry reach to access rainbow trout stranding post downramp. AGfD evaluated stranding by dividing each cobble bar examined into quadrants and obtaining a total count of stranded fish by examining total area of the bars. AGFD also noted stranding ofmacroinvenebrates. Cobble bars selected for evaluation were representative of this habitat type in the Lee Ferry reach and were in areas which receive preferential use by fishing guides and trout (6Omm) was observed to have been stranded and low concentrations of Gammarus were observed stranded in a few shallow pools, no other stranded macroinvenebrates noted. At RM-8, two live rainbow trout (9Omm and .400-500mm) were observed stranded in a large pool, Gammarus (~I,OOO) of diverse size range were observed tranded in one small pool, and several thousand snails (Physidae) were observed stranded on two small sand ~ habitats associated with sedges nearshore. At RM-2.5, one dead adult flanneimouth sucker (catostomus latipinnis) was observed in approximately 3 ft. Of water just inside mouth of backwater. This was judged not to be a stranding-related monality.