How DEP Forecasts and Maintains Reservoir Levels

Reservoir Operations and Watershed Monitoring

The Catskill/Delaware system supplies the vast majority of New York City's water. Forecasting reservoir levels in this system is one of the most important and most difficult  tasks DEP faces in the operation of the water supply. Reservoir levels are primarily determined by the balance between streamflow into the reservoirs, diversions (withdrawals) for water supply, and releases to maintain appropriate flows in the rivers below the dams. Streamflow is affected by rain and snowmelt, both of which are hard to predict accurately.  DEP is harnessing new technology and a variety of resources to better predict and manage our water supply.

Water in the Delaware River Basin is jointly managed pursuant to a 1954 Supreme Court decree that governs water allocations for New York City and the states of New York, Pennsylvania, New Jersey, and Delaware. The Flexible Flow Management Plan (FFMP) is intended to provide a more adaptive means for managing releases from the Cannonsville, Pepacton, and Neversink reservoirs by providing for releases based solely on the time of year and reservoir storage conditions.