Effect of reservoir releases on tailwater ecology: A literature review

Publication Date



Prepared by the U.S. Army Engineer Waterways Experiment Station


ecology, releases, impoundments, streams, design, structures, life history, history, physiology

Report number

Technical Report No. E-81-12

Publication place

Vicksburg, MS


U.S. Army Engineer Waterways Experiment Station


This document presents a review of the often contradictory literature describing the effects of release waters on the tailwater environment and biota. The physical and chemical conditions found in tailwaters downstream from warmwater and coldwater discharge impoundments are compared and contrasted to those found in natural streams. Reservoir discharges modify the physical, chemical, and biological characteristics of the stream ecosystem.Physical and chemical characteristics in tailwaters are primarily determined by the depth, volume,and schedule of water releases. The magnitude of change is related to the type of reservoir and to the design and operation of outlet structures. The structure of the biotic community reflects the physical and chemical conditions existing in a particular tailwater. The community is composed of organisms, including nonnative species, that are adapted to this environment. The effects of the tailwater environment on the life history, physiology, and abundance of selected species are described. This information will aid in the development of reservoir discharge guidelines that will enhance the quality of the tailwater environment to increase project benefits.

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