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Using Stream Discharge as a Predictor of Biotic Health in the Upper Oconee Watershed
Citation:
Sterling, J. L., B. RASHLEIGH, B. L. Nuse, AND R. Katz. Using Stream Discharge as a Predictor of Biotic Health in the Upper Oconee Watershed. In Proceedings, Georgia Water Resources Conference, Athens, GA, April 27 - 29, 2009. Georgia Institute of Technology, Atlanta, GA, 1-5, (2009).
Impact/Purpose:
see description
Description:
Drought is viewed typically as an issue of water quantity, but drought also likely has strong effects on water quality in streams. These effects may occur via increased pollutant and nutrient concentrations and stream water temperature, as well as reductions in instream habitat. Many aquatic macroinvertebrate taxa are sensitive to changes in water chemistry, and streams with degraded water quality are often characterized by low macroinvertebrate diversity. A previous study by the Upper Oconee Watershed Network related the Georgia Adopt-A-Stream biotic index for macroinvertebrates to water chemistry (Kominoski et al. 2007), but did not consider the effects of stream discharge, which also potentially influences index scores. We used long-term datasets on biotic indices of water quality in the upper Oconee River watershed to determine whether variation in biotic indices is associated with periods of extreme low flow. We used multiple measures of flow (including seasonal means, minima, maxima, and variability in discharge) from USGS gauge data to examine patterns in the Georgia Adopt-A-Stream macroinvertebrate index for seven tributaries of the North and Middle Oconee Rivers in Clarke County, Georgia. We found that the inclusion of flow variables improved the prediction of macroinvertebrate index scores, compared to a model including only chemical variables, and that a positive response occurred to mean flow in the preceding season. We infer from our results that site-specific flow variability may be structuring benthic macroinvertebrate communities in urban streams in the upper Oconee River basin, and may be important to consider when using indices for bioassessment throughout the state of Georgia.
