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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
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Summary

For almost 180 years, New York City (NYC) has shown a great deal of foresight to supply safe drinking water to its large population. Today’s municipal supply comes from the nearby Croton watershed (which began operations in 1842) and the larger and more distant Catskill and Delaware watersheds, put into service during the early 20th century. The current system provides about 1 billion gallons of drinking water a day to over 8.5 million people in NYC and about 1 million people living in nearby Westchester, Putnam, Ulster, and Orange counties. The combined water supply system includes 19 reservoirs and three controlled lakes with a total storage capacity of approximately 580 billion gallons. Approximately 10 percent of NYC’s average daily water demand is supplied by the Croton system, which is now filtered, with the Catskill/Delaware system supplying the remaining 90 percent.

The combined Catskill/Delaware portion of the water supply is the largest unfiltered water supply in the United States, with chlorine and ultraviolet disinfection being the primary means of treatment. This unusual status is made possible by the largely undeveloped, forested condition of the systems’ upstate watersheds and by implementation of NYC’s extensive Watershed Protection Program intended to maintain and enhance the high quality of these surface water sources. The Watershed Protection Program has allowed the New York City Department of Environmental Protection (NYC DEP), which runs the water supply system, to secure a series of waivers from the filtration requirements of the U.S. Environmental Protection Agency’s Surface Water Treatment Rule.

The Watershed Protection Program has a variety of technical elements to control potential sources of pollution to the water supply, such as wastewater and stormwater, streambank erosion, and agricultural and forest management activities. A major element is a Land Acquisition Program through which the City has purchased land in the watershed. In addition, NYC DEP has provided funding for economic and environmental partnership programs with watershed communities. These elements were comprehensively reviewed by the National Academies of Sciences, Engineering, and Medicine in 1999, whose report found the entire program to be “an ambitious and path-breaking program of source water protection.” Eighteen years later, a second National Academies’ review was requested by NYC DEP, which has culminated in this report. The Statement of Task for the National Academies’ study is found in Box S-1. The overall Watershed Protection Program has evolved considerably since its inception, and there are now almost two decades of water quality data with which to evaluate the program’s progress.

This report assesses the efficacy and future of NYC’s extensive watershed management activities. Since 1997, $2.5 billion have been spent on various subprograms of the Watershed Protection Program, averaging $100 million annually. Although the subprograms have different structure and administration, pollutant mitigation goals, and operational objectives, all derive from the 1997 Memorandum of Agreement (MOA) and subsequent filtration avoidance determinations that outline the suite of actions that NYC DEP must take to

Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
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comply with the Surface Water Treatment Rule. The MOA has two overarching goals: protecting the water quality in the reservoirs and ultimately in NYC drinking water and enhancing the vitality of communities in the upstream watersheds.

Chapters 1 to 4 discuss the ecological, historical, and cultural antecedents of the watershed; the massive and complex NYC water supply system; and the water quality issues of primary concern. Chapters 5 to 11 cover different subprograms within the Watershed Protection Program, describing the specific programs’ objectives, evaluations of program effectiveness, and opportunities for improvement. Chapter 12 reviews NYC DEP’s monitoring and modeling programs, while Chapter 13 discusses measures of community vitality. Chapter 14 addresses the balance among subprograms and future directions for the Watershed Protection Program. The most important conclusions and recommendations are compiled in this summary.

ECOLOGICAL, HISTORICAL, AND CULTURAL ANTECEDENTS

Although the Watershed Protection Program is frequently cited as a success story, it is not immune to controversies, many of which date back to the 1997 MOA or even to the initial development of the Catskill and Delaware systems. The good-faith efforts of watershed communities and NYC DEP to resolve long-standing differences and obstacles to cooperation have strengthened the Watershed Protection Program and the economic viability of the Catskills. Nonetheless, future success can be fostered, and unintended conflicts and controversies minimized, with a shared understanding of ecological, historical, and cultural antecedents.

Chapter 2 shows that most of the watershed conditions, suite of pollutants, and other water quality challenges faced by the Watershed Protection Program originate from historical land and resource uses and development patterns in the Catskills since the 1700s. Even after a long period of widespread, intensive, and unregulated land and resource use, the forests, streams, and aquatic ecosystems of the Catskills have largely recovered and support very high ambient water quality. Thus, a “pristine wilderness” with no people and no human activities is not a necessary precondition for the production of clean water.

Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
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NEW YORK CITY’S WATER SUPPLY SYSTEM

Chapter 3 describes NYC’s water supply system, which collects and transports surface water, by gravity, from 2,000 square miles of land in three upstate watersheds to approximately 9.5 million people every day (see Figure S-1). NYC has high-quality water sources and several layers of treatment, including settling in reservoirs, introduced alum under some conditions, and sequential ultraviolet and chlorine disinfection that, so far, has precluded the need for filtration of the west-of-Hudson system. NYC DEP operates its diverse reservoirs, sources, and aqueduct connections to minimize the risk of poor-quality water entering the distribution system. Chapter 3 also describes the regulatory framework by which NYC DEP is able to avoid filtration of the Catskill/Delaware supply.

Looking to the future, covering Hillview Reservoir, which is downstream of the ultraviolet disinfection facility and the last stop prior to distribution, should be a top infrastructure priority. Storage of finished water is essential for ensuring flexibility of system operations to respond or adapt to stressors and to protect public health. Furthermore, given the potential loss of highly experienced operators and managers, the NYC DEP should invest in succession planning and operator professional development.

CURRENT CONDITIONS, TRENDS, AND FUTURE STRESSORS

The Catskill/Delaware watersheds are a humid, temperate, mountainous landscape with a large proportion of forestland (72 to 93 percent across the six reservoir watersheds) and smaller proportions of other land uses, primarily agriculture and developed areas. All land covers and land uses have potential to shed pollutants into NYC’s water supply reservoirs. Chapter 4 describes the hydrologic regime of the Catskills region, land cover and land use trends in the watershed over the last 20 years, the pollutants of concerns, and some of the ways that climate change may alter these stressors.

Land cover and land use changes from forest and farm land to developed areas in the West-of-Hudson watershed have been minimal, a barely detectable fraction of the average change for New York State, from 2001 to 2016. This stability can be attributed to the MOA, Watershed Protection Program, forest and agricultural land conservation efforts, and recent market trends for agricultural and forest products.

Turbidity is a top priority for the foreseeable future because of the low turbidity target for regulatory compliance, the nature of turbidity in the Catskill system, and the uncertainty about how restored stream corridors will perform in extreme events. Nutrients (specifically phosphorus) are the second priority, given the associated risks of hazardous algal blooms contributing to direct toxicity, turbidity problems, and anoxic conditions in the reservoirs. Natural organic matter is the third priority due to the creation of disinfection by-products. Finally, because of ultraviolet disinfection, microbial pathogens are a lesser, but still important, concern. For the highest priority pollutants, adopting a mass-balance modeling approach is crucial to understanding their future role as system stressors under changing conditions (e.g., climate, land use, and implementation of mitigation measures).

The Committee’s mass balance analysis of phosphorus data shows that total phosphorus flux trends for the West Branch of the Delaware River above Cannonsville Reservoir are moving in the right direction since 2010, but the rate of improvement is very slow. Understanding the reasons for temporal patterns of phosphorus inputs to Cannonsville Reservoir and phosphorus concentrations in the reservoir is crucial to preventing eutrophic conditions and harmful algal blooms.

Predicted climate changes in the NYC watershed region are likely to have several undesirable effects on reservoir water quality from increased nonpoint source pollution. Climate change will likely lead to more intense storms that exacerbate turbidity loading problems. The concentration and characteristics

Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
×
Image
FIGURE S-1 New York City’s surface water supply system. Figure in color at https://www.nap.edu/catalog/25851.
Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
×

of natural organic matter in the reservoirs may change, increasing concentrations of disinfection byproducts or extending periods when the highest disinfection byproduct concentrations are formed. NYC DEP should regularly analyze their monitoring data for trends that would identify such changes and indicate whether water quality parameters could be altered by climate change.

NYC’s system operations appear able to more than adequately protect the quality of the City’s drinking water source, even under extraordinary storm conditions. Modeling studies show that even when subjected to events much greater than historical extremes, water quality failures defined by exceedance of the 5 nephelometric turbidity units turbidity standard at Kensico would be rare and small (less than 6 nephelometric turbidity units) if properly managed. Retrospective performance analyses should follow major potential contamination events and rigorous, systematic assessments (“stress tests”) should occur at least every five years.

WATERSHED AGRICULTURAL PROGRAM

The Watershed Agricultural Program, reviewed in Chapter 5, works with farm and forest landowners in the Croton and Catskill/Delaware watersheds. The program’s goals are to protect water quality (focusing on nutrients, microbial pathogens, sediment, and pesticides) and to ensure the economic vitality of watershed agriculture. Farms voluntarily enrolled in the program must have Whole Farms Plans that specify the best management practices that will be implemented on an individual farm to prevent pollutants (e.g., animal waste) from entering nearby waterbodies. The Watershed Agricultural Program is run by the Watershed Agricultural Council.

Typical of most subprograms of the Watershed Protection Program, the Watershed Agricultural Council uses a variety of metrics to understand the effectiveness of the program, but employs no direct and regular measurements of water quality or community vitality. Rather, the program tracks the number of participants, plans, and best management practices, along with annual status reviews of Whole Farm Plans that track changes in farm operation. Based on these metrics, the Watershed Agricultural Program has had great success, with a high percentage of farms participating. To improve the Watershed Agricultural Program’s ability to reach the goals of the MOA, the following conclusions and recommendations are made.

The Committee’s analysis of soil phosphorus data collected from agricultural lands in the Cannonsville watershed shows that concentrations have fallen slowly over the last decade. Although the soil phosphorus data were collected by the Watershed Agricultural Council to guide individual farmers, they also are useful in understanding the overall progress of the Watershed Agricultural Program in reducing phosphorus in soils. Furthermore, the Committee’s analysis suggests that best management practice installation should be focused on areas of the landscape expected to produce the largest runoff and pollutant flux. NYC DEP and the Watershed Agricultural Council should regularly analyze soil phosphorus and similar data to guide and improve phosphorus management.

To combat phosphorus mass balance problems, the Watershed Agricultural Council should develop a public-private partnership to turn manure into energy and/or other useful byproducts. New businesses could collect all available farm manure for significant resource recovery (e.g., phosphorus, nitrogen, carbon, and energy) for use inside or outside the watershed. Encouragement from NYC DEP for manure collection and processing, along with priority cost share for exclusionary fencing of riparian zones and watercourses, will be vital to reducing nutrients and pathogens in a manner consistent with enhancing economic vitality of farming in the watershed.

The Watershed Agricultural Council and the New York City Department of Environmental Protection should jointly develop a climate action plan for agriculture that clearly defines potential impacts, proposes actions to mitigate those impacts, and devises an adaptation strategy that ensures that agriculture

Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
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does not contribute disproportionally to water quality degradation. Such an approach should include accounting for expected increases in precipitation intensity and temperature, overland flow, and pollutant transport expected from climate change in future best management practice designs to ensure their correct functioning under changing conditions.

STREAM MANAGEMENT PROGRAM

Established in the mid-1990s and now one of the largest subprograms, the Stream Management Program aims to reduce suspended sediment transport that leads to high turbidity in west-of-Hudson streams and reservoirs. In addition to minimizing erosion and sediment transport that can lower water quality, the projects of the Stream Management Program benefit watershed communities by providing flood hazard mitigation; protection of roads, bridges, and other public infrastructure; protection of private property; and improvement of aquatic habitat. The Stream Management Program prioritizes stream reaches for management based on water quality data, geologic setting, and potential for high erosion rates and sediment loads. As discussed in Chapter 6, management strategies span a range of activities from preservation and passive monitoring to full channel restoration.

The Stream Management Program stands out among stream restoration efforts nationwide in that its approach focuses on whole watersheds, and substantial attention is given to scientific investigation, stream corridor mapping, and long-term water quality monitoring. The program staff have actively and consistently used scientific and engineering research, performance monitoring, and operational experience to understand how Catskill streams function, identify causes of stream degradation and instability, identify and prioritize the best locations for intervention, select the most effective restoration approaches, monitor the response of restored reaches, and adapt their management approach as a result of prior project experience.

The Stream Management Program, in collaboration with others, should move into vigorous data-analysis even as new data are collected. Scientists with a combination of training and experience in geomorphology, climate science, and statistics such as those at the U.S. Geological Survey and university researchers should engage deeply in the data analysis. Conclusive answers about the effectiveness of the Stream Management Program will require long-term monitoring of future large storm events as well as innovative and comprehensive analyses of current data.

The New York City Department of Environmental Protection should more routinely incorporate hydrologic/hydraulic modeling into the stream restoration design process. The use of hydrologic/hydraulic models will allow NYC DEP to design projects for determining channel dimensions and flow capacity to improve functionality during scenarios of greater future flooding due to climate change.

LAND ACQUISITION PROGRAM

The Land Acquisition Program, through which NYC DEP purchases land in the Catskill/Delaware watershed from willing sellers, has been critical in complying with the Surface Water Treatment Rule. Reviewed in Chapter 7, land acquisition is meant to prevent activities or development that may harm water quality, generally keeping lands in an undeveloped state or redirecting development to less-sensitive lands. The program’s large budget and the necessary interactions between NYC DEP and stakeholders have created tension regarding local communities’ objectives for continued economic vitality.

Given the substantial progress made in the Land Acquisition Program since the signing of the MOA, the Committee reviewed the objectives and structure of the now mature program, focusing its review on water quality improvement. Several recommendations to refocus the program are made.

Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
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The metrics of the Land Acquisition Program should focus on acquisition of the most valuable lands for water quality protection. Current metrics that focus on acres of land solicited for purchase, but do not directly contribute to any water quality objective, should be eliminated. Metrics of the Land Acquisition Program should be the amount of land valuable for water quality protection actually preserved, current deleterious activities eliminated, or future potential ones prevented from occurring. NYC DEP’s watershed models should be harnessed to assess which lands are more likely to be sources of pollutant loading.

The New York City Department of Environmental Protection (NYC DEP) should work with watershed communities to identify parcels now owned by NYC DEP with lower protection value that offer development or relocation potential. These parcels could be sold or swapped for higher-protection-value lands, serving both watershed protection and community vitality objectives. While such “swaps” are only allowed when it results in more rather than less watershed protection, a collaborative program could meet critical needs while fostering better community relations and more successful implementation of the Flood Buy-Out programs.

The New York City Department of Environmental Protection should shift funding and emphasis to the Flood Buy-Out and Streamside Acquisition programs, which aim to acquire riparian lands on critical areas of tributary streams. This flexibility to move funds appears to be permitted in the filtration avoidance determination, and the reduction of program funding “silos” would allow program managers to respond more quickly to land acquisition opportunities and changing circumstances.

WASTEWATER PROGRAMS

Wastewater treatment in the Croton, Catskill, and Delaware watersheds with centralized wastewater treatment plants or septic systems has a direct impact on water quality in the watersheds and ultimately in NYC’s drinking water (Chapter 8). The wastewater programs also support community vitality by providing a valuable public service provided at low cost to watershed residents and businesses.

All 42 wastewater treatment plants in the west-of-Hudson region have been upgraded to state-of-the-art, tertiary-equivalent treatment, including seven new wastewater treatment plants constructed as part of the New Sewage Treatment Infrastructure Program. The phosphorus loadings from these sources to streams in the watershed have declined by more than 90 percent and suspended solids and pathogens loads have also declined. The voluntary Septic System Program has not had the same success. This is noteworthy because most watershed residents have septic systems. The following recommendations focus on improved treatment of human wastes by the Watershed Protection Program.

Protecting the Kensico Reservoir from wastewater treatment plant effluent and failed septic systems should be a top priority for the Watershed Protection Program. Given the proximity of hundreds of septic systems to the Kensico Reservoir, NYC DEP should focus on removing conventional septic systems from this watershed and replacing them with either best available control technology or centralized wastewater treatment.

The Septic System Program should be better funded to accelerate its implementation, eliminate the backlog of septic system repairs and replacements, and train contractors on the installation and maintenance of best available control technologies. Contracts between NYC DEP and the Catskill Watershed Corporation should allow time extensions so that there is always a contract in place for critical septic system repairs and replacements. The Septic System Program provides significant community vitality benefits that are currently unrealized because implementation has been relatively slow and enrollment by residents has been limited.

Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
×

The New York City Department of Environmental Protection is encouraged to require the use of aerobic treatment units for new and replacement septic tanks. Further, given the topography and soil characteristics of the Catskill region, alternative soil adsorption systems (shallow adsorption, mound, or drip systems) should be required to ensure more complete wastewater treatment. Aerobic treatment units and alternative soil adsorption systems could be investigated via a pilot study, which could also serve as training sites for installation and maintenance contractors. Use of aerobic treatment units and alternative soil adsorption systems will require a workforce to install and maintain these systems.

STORMWATER PROGRAM

The Stormwater Program (Chapter 9) manages activities that potentially discharge polluted runoff from developed/urban areas into the water supply. Pollutants of concern in stormwater are primarily fine sediment, nutrients, microbial pathogens, oil and grease, floatables, dissolved metals, and toxic organics. A combination of federal, state and local regulations require treatment of stormwater runoff from new urban development as well as sediment-laden runoff from construction sites. There is also the Stormwater Retrofit Program specifically targeting NYC’s water supply watershed as obligated by the filtration avoidance determination. NYC DEP’s Stormwater Program relies on standard design criteria used nationally by municipalities and acceptable to federal and state environmental protection agencies.

The following recommendations are aimed at helping NYC DEP better evaluate the Stormwater Program to more directly assess program impacts on water quality.

Performance-based monitoring of some of the most commonly installed stormwater control measures would allow the New York City Department of Environmental Protection to evaluate whether installed stormwater control measures meet the pollutant reductions stated in the design guidance. Stormwater control measures selected for study should be those used most often by developers and consulting design engineers. The study design consists of flow-weighted measurements of influent and effluent pollutants (e.g., phosphorus, nitrate, total suspended solids, and pathogens) for selected stormwater control measures.

Current design standards for stormwater control measures should be evaluated for treatment efficiencies and structural stability based on projected changes in climate, particularly precipitation intensity and duration. Hydraulic design of stormwater control measures can be evaluated using models to assess whether the inlet structures can accommodate the discharge from more frequent extreme precipitation events and whether treatment targets can be met.

ECOSYSTEM PROTECTION AND MANAGEMENT PROGRAMS

Chapter 10 reviews three forest conservation programs in the west-of-Hudson watershed: the Wetlands Program, the terrestrial and aquatic Invasive Species Program, and the Aquatic Ecology Program. Protecting terrestrial and aquatic ecosystems is central to maintaining NYC DEP’s filtration avoidance status and supplying high-quality water to its consumers.

Forests cover 70 to 90 percent of land in the six west-of-Hudson reservoir watersheds and have a major effect on natural organic matter, pH, and nutrient cycling. Additionally, timber harvesting on private forestland contributes to economic viability of the region. Yet, the forestry programs are small in staffing and budgetary terms, which is not commensurate with their key role across most of the watershed. The Committee’s review of the forestry, wetlands, and invasive species programs leads to several conclusions and recommendations.

The Watershed Forestry Program should grow to increase the proportion of private forestland that it influences. Private forestland occupies a key landscape position in the west-of-Hudson watershed, between Catskill Forest Preserve lands at high elevations and the NYC DEP land surrounding reservoirs. The

Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
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Watershed Forestry Program has active connections to about 40 percent of the private forestland base. Given increasing rates and volumes of timber harvesting, this would be a timely investment in watershed protection and community vitality. Increasing Watershed Forestry Program staffing (by one or two full-time employees) and the operating budget could double the amount of private forestland managed.

A working group of Watershed Agricultural Council and their partners could evaluate prospects for small- and intermediate-scale wood chip gasification in the Catskills. Reliable local and regional markets for low value trees are urgently needed to improve standards of silviculture in the Catskills, specifically, to provide ecologically sound and financially viable alternatives to selectively removing only the best quality trees.

The New York City Department of Environmental Protection should clarify the terrestrial and aquatic invasive species programs’ responsibilities within the regional invasive species collaborative network and support these responsibilities adequately. Given the potential environmental, economic, and water quality impacts of invasive species, responding to important outbreaks should be prioritized.

Changes in species composition, land cover, and climate will affect the composition of both native and non-native species throughout the New York City watersheds. Such changes may affect economic viability (e.g., forest and agricultural products), water availability (including during droughts and floods), and water quality (including changes in loadings of water, sediments, and solutes).

PUBLIC HEALTH PROGRAMS

Several subprograms of the Watershed Protection Program focus on threats to NYC’s drinking water from waterborne microbial pathogens (Chapter 11). To maintain its filtration avoidance determination, the NYC DEP must ensure that there are low levels of fecal indicator bacteria in both the source water and the distribution system. Along with enteric viruses, the protozoan pathogens Giardia and Cryptosporidium must be inactivated by disinfection. Finally, the drinking water cannot be a source of waterborne disease outbreaks. The following conclusions and recommendations are made about the three subprograms that focus on these goals: the Waterborne Disease Risk Assessment Program, microbial monitoring in the Catskill/Delaware system, and the Waterfowl Management Program.

The Waterborne Disease Risk Assessment Program should determine whether the recent increase in protozoan parasitic infections observed via the disease surveillance system is from increased use of culture-independent diagnostic tests. A survey of the laboratories included in the surveillance system and an analysis of the proportion of tests that are culture-independent diagnostic tests are essential to understanding this apparent increase.

Although the microbial monitoring program is well structured and meets all regulatory requirements, the data it collects could be better analyzed and used to inform the Watershed Protection Program. For example, if reservoirs or tributaries exceed regulatory limits for fecal or total coliforms, or are designated as coliform-restricted, NYC DEP should use Microbial Source Tracking studies to identify sources, determine the relative importance of anthropogenic versus animal sources, and inform control strategies within the Watershed Agricultural Program, the Septic System Program, and the Stormwater Program.

The Waterfowl Management Program has demonstrated effectiveness at reducing fecal coliform bacteria loads to reservoirs from waterbirds and other wildlife. Although the program is important to meet the water quality regulations and should be continued, the future covering of Hillview Reservoir will still provide better long-term protection of that waterbody from fecal indicator bacteria than the Hillview Waterfowl Management Program.

Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
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WATER QUALITY MONITORING, ASSESSMENT, AND MODELING

NYC DEP monitors a very large set of parameters within their watersheds, reservoirs, conveyances, and related facilities with real-time and near real-time sensor arrays as well as grab samples and laboratory analyses. These data help to guide operations, assess management actions, and fulfill regulatory requirements. Monitoring data related to water quality and streamflow, along with watershed and reservoir models, are used to varying degrees in evaluations of engineering, water supply operation and design, and program assessments. The most relevant example is the Operations Support Tool, a combined water quantity/water quality model that simulates water availability and quality throughout the NYC water supply system and is used to inform decisions about system operation and planning. Although not officially a part of the Watershed Protection Program, these programs were extensively reviewed by the Committee because of their significant role in ongoing evaluation of the entire Watershed Protection Program. Chapter 12 reviews the monitoring and modeling programs and recommends improving these critical support efforts.

Reporting on water quality should always include some formal statistical testing for trends. NYC DEP should apply Weighted Regressions on Time, Discharge, and Season or other statistical modeling analyses to the many types of data they collect, with a focus on trends in flow-normalized flux of pollutants. These analyses have potential to provide a common basis to show the relevant trends for any given analyte across monitoring sites. Sharing NYC DEP’s data through a system like the National Water Quality Portal will make it possible for other researchers to enhance the understanding of watershed water quality.

The New York City Department of Environmental Protection is urged to shift its modeling and reporting of progress in the Watershed Protection Program evaluation to a mass balance approach. This requires a fundamental accounting strategy that estimates sources and downstream disposition of constituents of concern. These strategies should have the geographic specificity to account for waters flowing to the major reservoirs and be divided by source types, such as manure or fertilizer application, septic tanks, urban stormwater, or other categories of point and nonpoint sources. A mass balance approach is exemplified by the statistically based watershed model SPARROW.

Watershed modeling should become a more integral part of the Watershed Protection Program. Watershed modeling can inform the Land Acquisition Program, agricultural best management practice implementation, and the Stormwater Program. NYC DEP should aim to have a modeling and data analysis team evenly balanced between deterministic and statistical models and approaches, who actively engage with the program areas. NYC DEP has fully and effectively integrated the use of models for short-term decision support (e.g., the Operations Support Tool and reservoir water quality models); it is urged to similarly embrace watershed models for long-term decision support for the Watershed Protection Program.

The Watershed Protection Program would benefit from additional and substantial monitoring and analyses of community vitality. Although community vitality is a key element of the 1997 MOA, there is no monitoring effort to determine the well-being of watershed communities. Studies of economic vitality and social well-being could include assessing the causes and consequences of (1) change over time, (2) differences between communities, and (3) variation within communities to inform the refinement and implementation of the Watershed Protection Program. Comprehensive social and economic analyses are needed to update earlier work, test working hypotheses, fill critical gaps in knowledge, and establish baseline conditions to provide a foundation for understanding future programmatic effects.

Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
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CONCLUDING THOUGHTS

The 1997 MOA and Watershed Protection Program have largely succeeded in maintaining or enhancing water quality for the NYC water supply system and providing sustained investments to enhance the economic vitality of watershed communities. Active and evolving partnerships with the Catskill Watershed Corporation, Watershed Agricultural Council, and many other organizations and agencies show the potential—and tradeoffs—of balancing water quality protection with community vitality. The following conclusions and recommendations are made to improve the overall effectiveness and direction of the Watershed Protection Program.

The Watershed Protection Program overall appears to have admirably supported watershed water quality sufficient for compliance with the Surface Water Treatment Rule, with strong indications that it will remain effective into the future. However, in the last 25 years many of the most effective watershed management actions have already been implemented. Additional efforts will likely be more costly and less effective per incremental investment for achieving water quality objectives. Hence, many near-optimal combinations of program activities could provide similar overall performance. This means that there is increased flexibility to select watershed management actions that also support community vitality with little or no adverse influence on water quality.

Component programs within the Watershed Protection Program are generally well-balanced, with a few exceptions. The New York City Department of Environmental Protection should reduce expenditures in the Land Acquisition Program to fund other programs that will lead to more direct improvements in water quality. Programs with greater incremental value include an improved Watershed Agricultural Program, an improved Septic System Program, and the Watershed Forestry Program. This reallocation of funds is based on the seemingly small incremental contributions of the Land Acquisition Program to drinking water quality and its negative effects on community vitality, compared with the likely improvements to water quality from additional resources provided to these other programs.

Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2020. Review of the New York City Watershed Protection Program. Washington, DC: The National Academies Press. doi: 10.17226/25851.
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New York City's municipal water supply system provides about 1 billion gallons of drinking water a day to over 8.5 million people in New York City and about 1 million people living in nearby Westchester, Putnam, Ulster, and Orange counties. The combined water supply system includes 19 reservoirs and three controlled lakes with a total storage capacity of approximately 580 billion gallons. The city's Watershed Protection Program is intended to maintain and enhance the high quality of these surface water sources.

Review of the New York City Watershed Protection Program assesses the efficacy and future of New York City's watershed management activities. The report identifies program areas that may require future change or action, including continued efforts to address turbidity and responding to changes in reservoir water quality as a result of climate change.

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