Review of Ecological Effects of Rapidly Varying Flows Downstream from Hydroelectric Facilities.


R M. Cushman

Publication Date



day/night samples, downstream fish passage, hydroelectric, Hydropower, instream flow, mitigation, night, productivity, reservoirs, turbines, water depth

Journal or Book Title

North American Journal of Fisheries Management


Rapid changes in flow below hydroelectric facilities result from peaking operations, where water is typically stored in a reservoir at night and released through turbines to satisfy increased electrical demand during the day. Potential impacts of these short-term, recurring disturbances of aquatic systems below dams are important considerations in hydropower development. Reduced biotic productivity in tailwaters may be due directly to flow variations or indirectly to a variety of factors related to flow variations, such as changes in water depth or temperature, or scouring of sediments. Many riverine fish and invertebrate species have a limited range of conditions to which they are adapted; thus, such conditions can reduce the abundance, diversity, and productivity of these riverine organisms. Information needs for site-specific evaluations of potential impacts at hydroelectric peaking projects are outlined, along with management and mitigation options to reduce anticipated adverse effects.





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