Cooperative Fish and Wildlife Research Units Program: Georgia
Education, Research and Technical Assistance for Managing Our Natural Resources

Sustaining the ecological integrity of aquatic ecosystems while meeting human needs for water resources is a major challenge facing today's society. In many regions, including much of the eastern US, the growing demand for water supply and changing land use in urbanizing areas are altering hydrologic regimes in streams and rivers that society depends upon for ecosystem services, including support of native biodiversity. Meeting the challenge of balancing human needs for water resources with protecting aquatic ecosystems will require science-based information to answer the question: "What aspects of natural, or unaltered, hydrologic conditions are essential for the long-term maintenance of healthy aquatic ecosystems?" Aquatic resource managers have repeatedly expressed the need for science-based answers to the questions such as (1) how much can hydrologic conditions be altered in streams and rivers without impairing ecological function? and (2) what are the consequences of altering flows beyond those limits? River scientists around the world are currently engaged in developing methods to prescribe flow regimes that will protect ecological integrity of managed rivers (Postel and Richter 2003, Richter et al. 2003, Tharme 2003). This study provides an opportunity for USGS scientists to build on current concepts and, working with others, advance the science needed to understand linkages between hydrologic alteration and ecological integrity (See Box). In the case of the upper Flint River system, the Georgia Department of Natural Resources (GDNR) issues permits for water withdrawals and stipulates minimum instream flow requirements. The State currently is operating under an interim instream flow policy; GDNR has explicitly requested an objective effort to define the range of hydrologic regimes that should be protected in streams and rivers used for water supply. The purpose of this project is to advance the science needed to specify the hydrologic conditions necessary to support flowing water ecosystems in the context of municipal water-supply management. Specific objectives are to: 1) Develop conceptual economic models that relate hydrologic conditions, by way of hydraulic, geomorphic and water-quality change, to biological management objectives in a Piedmont river system. 2) Evaluate and determine the major driving factors (i.e., parameterize) in the conceptual ecological models using available data, and determine additional data needs. 3) Use the Upper Flint River system to demonstrate the potential for developing a decision-support system for use in evaluating options for water-supply development, incorporating ecological models developed and parameterized in Steps 1 and 2 to link hydrologic conditions to biological management objectives in an explicit landscape context. 4) Develop a long-term monitoring plan to allow model refinement and guide adaptive management relative to water supply in the Upper Flint River system.