Potomac Reservoir and River Simulation Model (PRRISM)

The Potomac Reservoir and River Simulation Model (PRRISM) was originally developed using Fortran by a research team at Johns Hopkins University in 1982. In the late 1990’s, the CO-OP section of the Interstate Commission on the Potomac River Basin (ICPRB) converted the model to an ExtendSim model. PRRISM simulates the physical processes and operations of four reservoirs and the allocation of water within the Washington Metropolitan Area (WMA) at daily time scale. It determines the amount of water available to each of the several jurisdictions, for given streamflows, demands, and weather allocation and reservoir operation rules. When operating in batch mode, PRRISM performs the functions of a regional water supply manager in strict accordance with rules specified by the model user. This interactive model allows participants to engage in a dialogue with the model as it is being executed, changing model parameters and overriding prespecified decision rules. Today PRRISM is a deterministic continuous simulation model that is regularly updated to reflect system changes. This model continues to serve as a long-term planning tool with which water supply management decisions are made.