New York City’s Operations Support Tool (OST): Implications for Water Supply Management


  • W. Joshua Weiss, Ph.D., P.E.; Grantley W. Pyke, P.E. - Hazen and Sawyer
  • Daniel P. Sheer, Ph.D., P.E.; Anthony P. Pulokas, P.E. - Hydrologics
  • James H. Porter, Ph.D. - NYCDEP

The New York City Department of Environmental Protection (DEP) has initiated design of an Operations Support Tool (OST), a state-of-the-art decision support system to provide computational and predictive support for water supply operations and planning. This paper describes the technical structure of OST, including the underlying water supply and water quality models, data sources and database management, reservoir inflow forecasts, and the functionalities required to meet the needs of a diverse group of end users.

The OST represents a major upgrade of DEP’s current linked water supply – water quality model, developed to evaluate alternatives for controlling turbidity in NYC’s Catskill reservoirs. While the current linked model relies on historical hydrologic and meteorological data, the OST can be driven by forecasted future conditions. It will receive a variety of near-real-time data from DEP sources (SCADA, keypoint monitoring, in-reservoir robotic monitoring), and outside sources (USGS gauges, NWS forecasts).

The OST will support two major types of simulations: long-term, for evaluating policy or infrastructure changes over an extended period of time; and short-term “position analysis” (PA) simulations, consisting of multiple short simulations, all starting from the same initial storage, hydrologic, and water quality conditions. Typically, the starting conditions for a PA run will represent those for the current day and traces of forecasted hydrology will drive the model for the duration of the simulation period. Results can be post-processed within the OST interface and used to compare, for example, the results of alternative operating decisions.

OST functionalities will support a wide range of DEP uses, including short term operational projections, outage planning and emergency management, operating rule development, and water supply planning. The primary use of OST will be management of turbidity in water diverted from terminal reservoirs via the application of linked water quantity-water quality models coupled to inflow forecasts. This will allow DEP to continue providing an adequate supply of high quality water for the nine million customers it serves. Secondary operational uses of OST include maintaining ecological flows in tailwaters and creating reservoir voids linked to snowpack to enhance the protective effect the dams provide to downstream communities.

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