An approach to optimizing reservoir operation for downstream aquatic resources

The issue of instream flow maintenance for downstream aquatic resources is a relatively new environmental quality consideration required in planning water resources projects. A mathematical programing methodology is proposed to examine the relationship between biological instream flow needs (IFN) and more traditional water project objectives, such as water yield, flood control, reservoir recreation, or economic efficiency. This optimization approach combines the linear decision rule (LDR) modeling technique with an objective function representing the value of reservoir releases to downstream fisheries. The IFN performance objective is based on an index of physical habitat conditions called weighted usable area (WUA) which has been developed by the U.S. Fish and Wildlife Service. Data from a multipurpose reservoir in central Illinois have been used to demonstrate the application of the nonlinear programing model and a heuristic solution algorithm employing piecewise linearization of the habitat objective functions and linear programing.