Review of the New York City
Department of Environmental Protection
Operations Support Tool
for Water Supply
Committee to Review the
New York City Department of Environmental Protection
Operations Support Tool for Water Supply
Water Science and Technology Board
Division on Earth and Life Studies
A Consensus Study Report of
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This activity was supported by the New York City Department of Environmental Protection under Contract No. CAT-447. Any opinions, findings, conclusions, or recommendations expressed in this publication do not necessarily reflect the views of any organization or agency that provided support for the project.
International Standard Book Number-13: 978-0-309-48279-0
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Digital Object Identifier: https://doi.org/10.17226/25218
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Suggested citation: National Academies of Sciences, Engineering, and Medicine. 2018. Review of the New York City Department of Environmental Protection Operations Support Tool for Water Supply. Washington, DC: The National Academies Press. doi: https://doi.org/10.17226/25218.
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COMMITTEE TO REVIEW THE NEW YORK CITY DEPARTMENT OF ENVIRONMENTAL PROTECTION OPERATIONS SUPPORT TOOL FOR WATER SUPPLY
DEBRA S. KNOPMAN, Chair, RAND Corporation, Arlington, Virginia
MONICA B. EMELKO, University of Waterloo, Waterloo, Canada
PAUL L. FREEDMAN, LimnoTech, Ann Arbor, Michigan
JEROME B. GILBERT, NAE, Consulting Engineer, Orinda, California
ROBERT M. HIRSCH, U.S. Geological Survey, Reston, Virginia
KIMBERLY L. JONES, Howard University, Washington, DC
CYNTHIA E. ROSENZWEIG, Goddard Institute for Space Studies, New York, New York
KAREN S. SKLENAR, The Cadmus Group, Inc., West Chester, Pennsylvania
JOHN E. TOBIASON, University of Massachusetts, Amherst
JAMES G. UBER, University of Cincinnati, Cincinnati, Ohio
ERIC F. WOOD, NAE, Princeton University, Princeton, New Jersey
National Academies Staff
LAURA J. EHLERS, Study Director, Water Science and Technology Board
BRENDAN McGOVERN, Senior Program/Research Assistant, Water Science and Technology Board
ERIN M. MARKOVICH, Senior Program/Research Assistant, Board on Atmospheric Sciences and Climate
WATER SCIENCE AND TECHNOLOGY BOARD
CATHERINE L. KLING, NAS, Chair, Cornell University, Ithaca, New York
DAVID A. DZOMBAK, NAE, Carnegie Mellon University, Pittsburgh, Pennsylvania
WENDY D. GRAHAM, University of Florida, Gainesville
ARTURO A. KELLER, University of California, Santa Barbara
MARK W. LeCHEVALLIER, Dr. Water Consulting, LLC, Morrison, Colorado
DINAH LOUDA, Veolia Institute, Paris, France
MARGARET A. PALMER, University of Maryland, Annapolis
STEPHEN POLASKY, NAS, University of Minnesota, St. Paul
DAVID L. SEDLAK, NAE, University of California, Berkeley
DAVID WEGNER, Retired, Water, Energy and Transportation Committee, Tucson, Arizona
P. KAY WHITLOCK, Christopher B. Burke Engineering, Ltd., Rosemont, Illinois
JAMES W. ZIGLAR, SR., Van Ness Feldman, Potomac, Maryland
ELIZABETH EIDE, Acting Director
LAURA J. EHLERS, Senior Staff Officer
STEPHANIE E. JOHNSON, Senior Staff Officer
M. JEANNE AQUILINO, Financial/Administrative Associate
COURTNEY DeVANE, Administrative Coordinator
BRENDAN R. McGOVERN, Senior Project Assistant/Research Assistant
CARLY BRODY, Senior Project Assistant
New York City’s water system reliably delivers 1.1 billion gallons of water per day to more than eight million residents, about half of the population of New York State. To meet its mission, the New York City Department of Environmental Protection’s (NYC DEP’s) Bureau of Water Supply operates a system of 19 reservoirs and three controlled lakes that drain a nearly 2,000-square-mile watershed that extends 125 miles north and west of New York City.
To reliably manage an engineered system of this geographic extent and complexity, the NYC DEP depends on a constant influx of timely and accurate data to guide its operations, along with mathematical modeling tools to support its decision making. To this end, NYC DEP embarked on the development of the Operations Support Tool (OST) to not only enhance operational decisions but specifically to help better address operations under conditions of high turbidity from the Catskill system. OST is a combined water quantity and water quality mathematical simulation model that probabilistically predicts future storage and water quality in the City’s reservoir system by accounting for dozens of variables such as weather forecasts, current demand for water, and myriad changes to the operation of the water supply system.
One of the goals of OST is to provide a technical basis for allowing NYC DEP to divert or release water from the Schoharie and Ashokan reservoirs in the Catskill system at the most opportune times to moderate the use of alum, a chemical additive widely used to reduce the turbidity of delivered water. Thus, NYC DEP’s use of OST can help ensure delivery
of the lowest-turbidity water, while also benefiting downstream communities by managing water releases and enhancing the health of local streams and reducing the risk of flooding. NYC DEP anticipates that OST could have uses throughout the water supply system that go well beyond turbidity control to address both water quality and water quantity concerns.
To further develop and plan for improvements of OST, the NYC DEP asked the National Academies of Sciences, Engineering, and Medicine to:
- Review the City’s use of OST for water supply operations, including managing elevated turbidity, and consider potential ways in which the City can more effectively use OST.
- Evaluate the performance measures the City uses to assess the efficacy of the Catskill Turbidity Control Program and make recommendations for additional performance measures, if necessary.
- Review the City’s plan for use of OST in evaluating proposed modifications to the Catalum State Pollutant Discharge Elimination System permit, as well as alternatives to be considered in the associated environmental review.
- Review NYC DEP’s existing studies of 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.
The Committee focused its efforts on addressing these four tasks, and by extension made several decisions about issues that it would not address. First, the Committee considered OST’s performance in the context of the geographic boundaries and physical processes of the model as currently configured. As a consequence, this report does not consider ecological impacts along the Lower Esopus Creek or the health of the aquatic and benthic communities of the Kensico Reservoir. Similarly, because this report evaluates OST and its performance based on the model’s current configuration, the Committee did not evaluate the efficacy of any possible plans for model enhancements. Second, the Committee took no position on the relative draws from the Delaware and Catskill systems and associated downstream impacts. Although these issues were considered to be outside the scope of this study, they are important as NYC DEP continues to build better relationships with communities affected by how it operates the water supply.
Although a number of activities and programs make up the Catskill Turbidity Control Program, evaluation of NYC DEP’s Stream Management Program fell outside the scope of this study. It will, however, be considered during the National Academies’ more comprehensive review of the City’s Water Protection Program that will commence in 2018. Finally, reviewing
past decisions made by NYC DEP, with or without the benefit of insight from OST, is also outside of the scope of this report.
This Consensus Study Report was reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise. The purpose of this independent review is to provide candid and critical comments that will assist the National Academies of Sciences, Engineering, and Medicine in making the published report as sound as possible and to ensure that it meets the institutional standards for quality, objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process.
We thank the following individuals for their review of this report: Peter M. Huck, University of Waterloo; Eugene J. LeBoeuf, Vanderbilt University; Jay R. Lund, University of California, Davis; David R. Maidment, University of Texas, Austin; Richard N. Palmer, University of Massachusetts, Amherst; Adam Parris, Brooklyn College, City University of New York; Cherie Schultz, Interstate Commission on the Potomac River Basin; and Jery R. Stedinger, Cornell University.
Although the reviewers provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations of this report nor did they see the final draft before its release. The review of this report was overseen by John J. Boland, Johns Hopkins University, and Philip C. Singer, University of North Carolina, Chapel Hill. They were responsible for making certain that an independent examination of this report was carried out in accordance with the standards of the National Academies and that all review comments were carefully considered. Responsibility for the final content rests entirely with the authoring committee and the National Academies.
Debra Knopman, Chair
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