Several state-of-the art models are available for analyzing water quality conditions in complex reservoir systems for a given set of operational conditions. Some of these models can even make operational decisions regarding proper gate regulations to obtain a desirable water quality condition at a dam site for a given set of flow conditions. HEC-5Q, Simulation of Flood Control and Conservation Systems (Including Water Quality Analysis) computer model, has the unique capabilities to accept user-specified water quantity and quality needs system-wide and to decide how to regulate the network of reservoirs. The decision criteria are programmed to consider flood control, hydropower, instream flow (municipal, industrial, irrigation, water supply, fish habitat) and water quality requirements. The HEC-5Q program was first applied to the Sacramento River System in California and a report was published in July 1985. Two other applications are in progress the Kanawha and Monongahela River systems, and are expected to be completed by September 1986. Keywords: Reservoir System Analysis, Water Quality, Case Study, Stream System Analysis, Computer Model.