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Communication at the NABS Annual meeting, Keystone, 2000
(508) RESPONSE OF TAILWATER BENTHOS TO ABOVE AVERAGE SPRING FLOWS.
D. Axford, D. Barnes, and M.R. Vinson. Department of Fisheries and Wildlife, Utah State University, Logan, Utah, USA 84322-5210
Since 1963, Flaming Gorge Dam on the Green River in northeastern Utah, USA has reduced annual flood flows by a factor of 2.4. In 1997 and 1999, springtime flows 1.8 and 2.2 times greater than the mean post-dam annual flood occurred. Periphyton and invertebrate data collected after the floods (1998 and 1999) were compared to pre-flood data (1993-97). Mean periphyton biomass was 54% lower following the 1997 flood and 72% lower following the 1999 flood, and has not yet recovered to pre-flood levels. Benthic invertebrate abundance and biomass decreased by more than 50% immediately following the floods, however within a few months differences in total invertebrate abundance among flood periods were slight (<20%) and post-flood invertebrate biomass was 46% higher in 1997 and 58% higher in 1999. Ephemeroptera abundance in 1988 and 1999 was 70 and 61% greater, respectively, than pre-flood abundance. Mean taxa richness was similar among flood periods (7.8 before, 8.8 after), but the occurrence of rare insect taxa increased following the high flows. The changes we observed in the insect assemblage following these two high flow events were greater than what we attributed to 20 years of partial thermal restoration.
Presented at 1:00 PM on Wednesday, May 31, 2000 in Disturbance - Abiotic Factors
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