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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Hyporheic Processes
FLOODPLAIN CONNECTION AND INTERSTITIAL FAUNAL DISTRIBUTION IN THE YAKIMA RIVER, WASHINGTON, USA.
J.L. Chaffin1, E.B. Snyder2, and J.A. Stanford2. 1Department of Biology, Virginia Polytechnic Institute, Blacksburg, VA, USA, 2Department of Biology, Flathead Lake Biological Station, University of Montana, Missoula, MT, USA
The distribution of interstitial fauna was investigated in hyporheic zones of six alluvial floodplains in the Yakima River Basin, Central Washington. The longitudinal and lateral distribution of the amphibitic Plecoptera (Kathroperla and Paraperla spp.) was used to indicate floodplain hydrological connection with the main channel. Shallow aquifer monitoring indicated that the ratio of all study wells to wells with stoneflies decreased from upstream to downstream, as expected due to increasing water quality degradation caused by an array of anthropogenic impacts. For example, the thermal regime of the main channel has been altered and our data suggests that there was a slight increase in groundwater temperature upstream to downstream. Also a severely altered flow regime has altered the exchange of surface, hyporheic, and groundwater flow and decreased the rate and extent of cut and fill alluviation. Three upstream reaches and a tributary reach have significantly higher species richness in comparison with two lower reaches, while abundance does not differ significantly. Proximity of monitoring wells to the main channel does not appear to be correlated to hyporheic stonefly or crustacean abundance and richness.
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