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Ecological Analysis of Hydrologic Disturbance Regimes in Streams of North and South Dakota

Valerie J. Kelly, Oregon State University, 200 SW 35th Street, Corvallis OR 97331

Streamflow variability is an important component of physical disturbance in streams, and is likely to be a major organizing feature of habitat for stream fishes. The disturbance regime in streams is frequently described by the variability in streamflow from both floods and prolonged low-flow periods. Streamflow disturbance is generally measured by the intensity, frequency, and predictability of timing for these extreme streamflow patterns. These ecologically-relevant streamflow metrics facilitate understanding the response of fish assemblages to physical habitat conditions. This study evaluates the utility of metrics derived from flood- and low-flow frequency distributions to describe the characteristics of fish assemblages in Dakota streams of the upper Missouri Basin. Data are provided from the USEPA's Environmental Monitoring and Assessment Program (EMAP) in the West. Flood- and low-flow frequency distributions are determined for EMAP sites from regional streamflow analysis of data from the U.S. Geological Survey. The preliminary analysis of streamflow patterns and fish assemblage structure is focused on identifying distinct stream and community types, and determining the association between patterns of streamflow variation and those of habitat and biota.

Keywords: streamflow regime, variability, floods, low flow, disturbance, EMAP

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