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Predicting and generalizing the refuge function of intermittent and ephemeral streams
Citation:
EBERSOLE, J. L., P. J. WIGINGTON JR, S. G. LEIBOWITZ, AND R. COMELEO. Predicting and generalizing the refuge function of intermittent and ephemeral streams. Presented at Oregon Chapter, American Fisheries Society Annual Meeting, Bend, OR, February 25 - 27, 2009.
Impact/Purpose:
Intermittent and ephemeral streams can provide important functions within stream networks.
Description:
Intermittent and ephemeral streams can provide important functions within stream networks. For fish, intermittent and ephemeral streams can contribute energy and materials to downstream perennial waters, serve as seasonal habitats, and/or provide refuge functions. Understanding the relative functions of intermittent and ephemeral streams and the relative benefit provided to downstream waters is needed to better inform watershed management and meet federal obligations under the Clean Water Act. Although the potential functions of intermittent and ephemeral streams are relatively well known, predicting and generalizing the relative contributions of these streams remains a challenge. To begin to address this need, we explored the potential for intermittent and ephemeral streams to provide summer thermal refuge functions for coldwater fish in the John Day and Grande Ronde River basins in northeast Oregon. We surveyed intermittent and ephemeral streams at their confluence with warm (>18oC) perennial streams in both basins in late July 2008 to identify potential thermal refuge areas defined as patches >3oC colder than the surrounding waters. The occurrence of potential thermal refuges and the characteristics of intermittent and ephemeral /perennial confluence zones differed markedly between basins. Differences in streamflow characteristics, water temperature, and geomorphology among sites were associated with geologic and climatic setting. We propose that Hydrologic Landscape Regions (Wigington et al, this session), designed to capture variation in geologic and climatic factors influencing stream hydrology, may provide a useful template for both predicting and generalizing the potential refuge functions of intermittent and ephemeral streams.