New York City's Operations Support Tool (OST)—An Application of Forecast-Based Water Supply Operations

New York City Department of Environmental Protection (NYC DEP) uses its Operations Support Tool (OST) to inform NYC Water Supply (NYCWS) short-term operations and long-term planning. OST is a state-of-the-art decision support system software that simulates and optimizes the routing of water throughout the NYCWS system while accounting for the current system objectives, infrastructure capacity and constraints. OST generates probabilistic output information to support decision making to supply 1.1 billion gallons high quality drinking water per day to approximately 9 million people in NYC and upstate communities. OST is a sophisticated simulation framework that integrates a water supply system operation model, mechanistic reservoir water quality models, statistical and climatological hydrologic forecasts, and various near-real-time data sources. A recent review by the National Academy of Sciences Engineering and Medicine describes OST as “one of the most advanced and complex support tools for water supply operations of its kind in the world.”

DEP relies on OST simulations in a wide variety of near-term, operational, and long-term planning applications. For operational support, OST is driven by and relies on an ensemble forecast provided on a daily-basis by the National Weather Service (NWS) Hydrologic Ensemble Forecast Service (HEFS). The use of an ensemble forecast has shifted NYCDEP’s operations from a deterministic to a probabilistic, risk-based approach.

In this presentation, we will describe OST components and present examples of how DEP uses this tool to support short-term operations including, during planed infrastructure shutdown. Finally, we will share our experiences and discuss challenges in implementing ensemble forecast-based operations.