Review of the New York City Department of Environmental Protection Operations Support Tool for Water Supply

The drinking water supply is managed by the Bureau of Water Supply within the New York City Department of Environmental Protection (NYC DEP). To continue to avoid filtration of the Catskill/Delaware portion of the water supply, in 2007, NYC DEP reexamined its control of turbidity in the Catskill portion of the water supply, including both structural improvements to the system and operational changes. The Operations Support Tool (OST) was developed as part of these efforts. OST couples models of reservoir operations and water quality; it uses real-time data on streamflow, snow pack, water quality, reservoir levels, diversions, and releases; and it incorporates streamflow forecastsâ€"all in order to predict future reservoir levels, water delivery to customers, and water quality within the system. These predictions inform the system operators, who then make decisions based on the most current data and forecasts.

This report reviews the use of OST in current and future reservoir operations. It considers potential ways in which the City can more effectively use OST, makes recommendations for additional performance measures, and reviews the potential effects of climate change on the City's water supply to help identify and enhance understanding of areas of potential future concern with regard to the use of OST.