Habitat Suitability Criteria for Assessment of Instream Flow Needs for Fish
Crance, Johnie H.
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In the western portion of the United States, competition for stream water has often been fierce. Water resource management agencies in the southeastern United States, where water has been relatively abundant, are now being faced with similar competing demands for water, and with increasing pressures to develop and defend recommendations for protecting fish and invertebrates in streams. Streamflow depletion at any time can result in severe long-term effects on fish populations (Peters, 1982). The allocation of stream water to any of numerous instream or offstream uses is tied to the issues of water quantity, quality, and timing, which center on two critical questions: (1) when and how much water of an acceptable quality should be left in a stream, and (2) what happens if flow regimes are changed? Answers to these questions will probably be complex, but reliable answers are needed to protect instream and offstream values. If instream flow interests expect to compete with offstream uses for limited water supp1ies, they must be ab1e to establish reliable and defensible methods for determining instream flow needs and demonstrate the environmental consequences of altered flow regimes. My objectives in this paper are: (a) to present an overview of the need, deve1opment, and use of stream habitat suitability criteria, and the use of these criteria for the assessment of instream flow needs; (b) to give a status report on the plan of the National Ecology Research Center (NERC) for expansion of instream flow research in the Southeast; and (c) to discuss the relevancy of the research to river corridor management.