The use of habitat structure preferenda for establishing flow regimes necessary for maintenance of fish habitat

The pursuit of simplicity in the complex management of instream and out-of-stream water uses very early led to the minimum, or “base,” flow concept and the myth that a consistent methodology could be used to establish the desired minimum flow. Such a single flow value has not proven to be practical. As water becomes fully appropriated to upstream use and storage, the minimum flow, if not violated, tends to become the average condition. This situation is manifest in a flat or stepped but fixed hydrograph throughout the stream reach of concern for much of the year.