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The Washington, D.C., Metropolitan Area (WMA) relies on the Potomac River for over 75% of its water supply. During droughts, the combination of low river flows and high water demands can affect water resources availability in the nation’s capital, and environmental flows in the basin’s streams.  Many decisions made during droughts rely heavily on forecasts of future Potomac River flows and WMA water demand. Specifically, nine-day, one-day, and current day flow forecasts are needed to determine release rates from upstream reservoirs and the need for changes in water suppliers’ operations.  Additionally, during emergency spill events, trajectories, concentrations, and time-of-travel estimates of contaminants are needed to manage source water operations. This presentation discusses a suite of modeling tools currently used by the Interstate Commission on the Potomac River Basin for long-term water supply planning, short-term drought management and emergency spill response. The tools presented include (1) a water supply planning model (the Potomac Reservoir and River Simulation Model), (2) an operational river flow and water demand forecast system for the Potomac River Basin, composed of a DELFT-FEWS (Flood Early Warning System) based Low Flow Forecast system (LFFS), a data portal, and an interactive web application, and (3) a high resolution two-dimensional hydrodynamic and oil transport model.