There are few river basins in North America where natural flow regimens have not been altered. Dams built by public and private agencies regulate impounded water supplies by storing and releasing water for power, flood control, irrigation, navigation, municipal and industrial uses, and others. Water diversions further reduce the amount of water available to stream resources, and also return the remainder to a point distant to the intake. Diversions may degrade water quality parameters such as sediment load, temperature, pesticides, herbicides, and others. Conversely, instream flow use of water for fishes is not universally recognized.
Most agencies accept fishery protection as conditional to awarding water rights.
However, quantification of stream flow needs of fishes, and operational and legal protection are not presently adequate. The importance of protecting stream fishery resources from a water rights perspective is little understood by the public at large, and fishing as a recreational use of larger streams and rivers has been increasingly de-emphasized by agencies in deference to reservoirs. The AFS believes that governmental and private sectors do not place sufficient emphasis on protection of instream water for management of stream fisheries resources. In this statement, we stress a need for more careful consideration in planning future stream alterations, discuss potential impacts of alterations, and provide guidelines for future management of stream fisheries. B. Impacts of Altered Stream Flows Changes in stream flow can affect fishes directly and indirectly.