This paper presents the results of computational fluid dynamics (CFD) modeling that were used to evaluate the water circulation patterns of the Pulgas Balancing Reservoir, located in San Francisco, California. CFD modeling was used to develop and evaluate reservoir inlet/outlet modifications and to optimize flow patterns by reducing undesirable flow features such as short circuiting and recirculation in dead spots within the reservoir. First, a general discussion of CFD modeling and water quality issues in water distribution storage reservoirs is presented. Then background and basic information on the reservoir is given. After that, the flow patterns for various scenarios are evaluated using CFD modeling and results are given. Includes figures.