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High Bridge in 1849, part of the Croton Aqueduct, the city's first water supply system

New York City's water supply system is one of the most extensive municipal water systems in the world. This complex system relies on a combination of aqueducts, reservoirs, and tunnels to meet the daily needs of New York City's more than eight million residents and its many visitors.

Thanks to well-protected wilderness watersheds, New York's water treatment process is simpler than in other American cities. One advantage of the system is that 95% of the total water supply is supplied by gravity. The other 5% needs to be pumped to maintain pressure, but this is sometimes increased in times of drought when the reservoirs are at lower than normal levels.[1]

The city has sought to restrict development throughout its watershed. One of its largest watershed protection programs is the Land Acquisition Program, under which the New York City Department of Environmental Protection (DEP) has purchased or protected, through conservation easement, over 130,000 acres (53,000 ha) since 1997.[2]


Responsible agenciesEdit

Responsibility for the city water supply is shared among three institutions: the New York City Department of Environmental Protection ("DEP"), which operates and maintains the system and is responsible for investment planning; the New York City Municipal Water Finance Authority ("NYW"), which raises debt financing in the market to underwrite the system's costs; and the Water Board, which sets rates and collects user payments.

New York City Department of Environmental ProtectionEdit

The DEP has a workforce of over 6,000 employees. It includes three bureaus in charge of, respectively, the upstate water supply system, New York City's water and sewer operations, and wastewater treatment:

  • The Bureau of Water Supply manages, operates and protects New York City's upstate water supply system to ensure the delivery of a sufficient quantity of high quality drinking water. The Bureau is also responsible for the overall management and implementation of the provisions of the city's $1.5 billion Watershed Protection Program.
  • In addition to operating and maintaining the water supply and sewerage system, the Bureau of Water and Sewer Operations is also responsible for the operation of the Staten Island Bluebelt, an ecologically sound, cost-effective natural alternative to storm sewers, which occupies approximately 15 square miles (39 km2) of land in the South Richmond area of Staten Island. This project preserves streams, ponds and other wetland ("bluebelt") areas, allowing them to perform their natural function of conveying, storing and filtering storm water.
  • The Bureau of Wastewater Treatment operates 14 water pollution control plants treating an average of 1.5 billion US gallons (5,700,000 m3) of wastewater a day; 95 wastewater pump stations; eight dewatering facilities; 490 sewer regulators; and 7,000 miles (11,000 km) of intercepting sewers.[3]

New York City Municipal Water Finance AuthorityEdit

The NYW finances the capital needs of the water and sewer system of the city through the issuance of bonds, commercial paper, and other debt instruments. It is a public-benefit corporation created in 1985 pursuant to the New York City Municipal Water Finance Authority Act. The Authority is administered by a seven-member Board of Directors. Four of the members are ex officio members: the Commissioner of Environmental Protection of the City, the Director of Management and Budget of the City, the Commissioner of Finance of the City, and the Commissioner of Environmental Conservation of the State. The remaining three members are public appointments: two by the Mayor, and one by the Governor.[4]

New York City Water BoardEdit

The New York City Water Board sets water and sewer rates for New York City sufficient to pay the costs of operating and financing the system, and collects user payments from customers for services provided by the water and wastewater utility systems of the City of New York. The five Board members are appointed to two-year terms by the Mayor.[5]


New York City's water system consists of aqueducts, distribution pipes, reservoirs, and water tunnels that channel drinking water to residents and visitors. A comprehensive raised-relief map of the system is on display at the Queens Museum of Art. Until the early 21st century, some places in southeastern Queens received their water from local wells of the former Jamaica Water Supply Company.[6]

Reservoirs and aqueductsEdit

The water system has a storage capacity of 550 billion US gallons (2.1×109 m3) and provides over 1.2 billion US gallons (4,500,000 m3) per day of drinking water to more than eight million city residents, and another one million users in four upstate counties bordering on the system. Three separate sub-systems, each consisting of aqueducts and reservoirs, bring water from Upstate New York to New York City:

The latter two aqueducts provide 90% of New York City's drinking water, and the watershed for these aqueducts extends a combined 1,000,000 acres (400,000 ha). Two-fifths of the watershed is owned by the New York City, state, or local governments, or by private conservancies. The rest of the watershed is private property that is closely monitored for pollutants; development upon this land is restricted.[7] The DEP has purchased or protected over 130,000 acres (53,000 ha) of private land since 1997 through its Land Acquisition Program.[2] Water from both aqueducts is stored first in the large Kensico Reservoir and subsequently in the much smaller Hillview Reservoir closer to the city.[7]

The water is monitored by robotic buoys that measure temperature as well as pH, nutrient, and microbial levels in the reservoirs. A computer system then analyzes the measurements and makes predictions for the water quality. In 2015, the buoys took 1.9 million measurements of the water in the reservoirs.[7]


The water from the reservoirs flows down to the Catskill-Delaware Water Ultraviolet Disinfection Facility, located in Westchester.[9][7] The facility was built because chlorinated water might have unintended side effects when mixed with certain organic compounds, and ultraviolet was seen as the least risky way to clean the water of any microorganisms.[7] The UV facility opened on October 8, 2013, and was built at a cost of $1.6 billion.[10] The compound is the largest ultraviolet germicidal irradiation plant in the world; it contains 56 UV reactors that could treat 2,200,000,000 US gal (8.3×109 L) per day.[11][12]

The Croton Filtration Plant, which was completed in 2015 at a cost of over $3 billion,[13][14] was built 160 feet (49 m) under Van Cortlandt Park in the Bronx and filters water from the Croton River.[15] The 830 by 550 feet (250 by 170 m) plant, which is bigger than Yankee Stadium,[13] is New York City's first water filtration plant.[14] It was built after a 1998 lawsuit by the presidential administration of Bill Clinton, which Mayor Rudy Giuliani settled under the condition that the city of New York would build the plant by 2006. The city had been studying possible sites for such a plant for more than 20 years in both the Bronx and Westchester.[16]

Tunnels and distribution systemEdit


From the Hillview reservoir water flows by gravity to three tunnels under New York City. Water rises again to the surface under natural pressure, through a number of shafts.[7] The three tunnels are:

  1. New York City Water Tunnel No. 1, completed in 1917.[7] It runs from the Hillview Reservoir under the central Bronx, Harlem River, West Side, Midtown,[7] and Lower East Side of Manhattan, and under the East River to Brooklyn where it connects to Tunnel 2. It is expected to undergo extensive repairs upon completion of Tunnel No. 3, in 2020.
  2. New York City Water Tunnel No. 2, completed in 1935. It runs from the Hillview Reservoir under the central Bronx, East River, and western Queens to Brooklyn, where it connects to Tunnel 1 and the Richmond Tunnel to Staten Island. When completed, it was the longest large diameter water tunnel in the world.[17]
  3. The uncompleted New York City Water Tunnel No. 3, the largest capital construction project in New York City's history (see below).[18] It starts at Hillview Reservoir in Yonkers, New York then crosses under Central Park in Manhattan, to reach Fifth Avenue at 78th Street. From there it runs under the East River and Roosevelt Island into Astoria, Queens. From there it will continue on to Brooklyn.


The distribution system is made up of an extensive grid of water mains stretching approximately 6,800 miles (10,900 km). As of 2015, it costs the city $140 million to maintain these mains.[7]

There are 965 water sampling stations in New York City. The water-sampling system has been in use since 1997. They consist of small cast-iron boxes with spigots inside them, raised 4.5 feet (1.4 m) above the ground.[19] Scientists from the city measure water from 50 stations every day. The samples are then tested for microorganisms, toxic chemicals, and other contaminants that could potentially harm users of the water supply system. In 2015, the DEP performed 383,000 tests on 31,700 water samples.[7]

Ongoing repairs and upgradesEdit

In order to comply with federal and state laws regarding the filtration and disinfection of drinking water, the U.S. Environmental Protection Agency (EPA) and the New York State Department of Health called on the city to create a treatment plan to serve the Croton System. The underground filtration plant is under construction in Van Cortlandt Park. While the Bloomberg administration originally budgeted the project at $992 million in 2003, an audit by the city's comptroller placed the actual costs at $2.1 billion in August 2009.[20]

The New York City water supply system leaks at a rate of up to 36 million US gallons (140,000 m3) per day.[21] A complex five-year project with an estimated $240 million construction cost was initiated in November 2008, to correct some of this leakage.

The construction of Water tunnel No. 3 is intended to provide the city with a critical third connection to its Upstate New York water supply system, allowing the city to close tunnels No. 1 and No. 2 for repair for the first time of their history. The tunnel will eventually be more than 60 miles (97 km) long. Construction on the tunnel began in 1970, and its first and second phases are completed. The latter opened with a ceremony under Central Park, in 2013. Completion of all phases is not expected until at least 2020.[22]

In 2018, New York City announced a US$1 billion investment to protect the integrity of its municipal water system and to maintain the purity of its unfiltered water supply.[23]

See alsoEdit


  1. ^ "History of New York City's Water Supply System". New York City Department of Environmental Protection. Retrieved December 8, 2009.
  2. ^ a b DePalma, Anthony (July 20, 2006). "New York's Water Supply May Need Filtering". The New York Times. Retrieved February 20, 2010.
  3. ^ "Bureaus and Offices". New York City Department of Environmental Protection. Retrieved July 10, 2010.
  4. ^ "About NYW". New York City Municipal Water Finance Authority. Retrieved February 20, 2010.
  5. ^ "Welcome to the NYC Water Board Web Site". New York City Water Board. Retrieved July 10, 2010.
  6. ^ "Groundwater Supply System". Retrieved April 19, 2017.
  7. ^ a b c d e f g h i j k Rueb, Emily S. (March 24, 2016). "How New York Gets Its Water". The New York Times. Retrieved August 30, 2018.
  8. ^ "New York City's Water Supply System Map". New York City Department of Environmental Protection. Retrieved September 3, 2009.
  9. ^ "Catskill-Delaware Water Ultraviolet Disinfection Facility". New York City. Retrieved September 1, 2012.
  10. ^ "NYC Catskill-Delaware UV Facility Opening Ceremony". TROJANUV. Retrieved November 12, 2013.
  11. ^ "Catskill-Delaware Water Ultraviolet Disinfection Facility". New York City. Retrieved September 1, 2012.
  12. ^ "TROJAN TECHNOLOGIES WINS NEW YORK CITY DRINKING WATER UV PROJECT" (PDF). TROJANUV. November 2, 2005. Retrieved September 1, 2012.
  13. ^ a b Dunlap, David W. (May 8, 2015). "As a Plant Nears Completion, Croton Water Flows Again to New York City". The New York Times. ISSN 0362-4331. Retrieved January 9, 2017.
  14. ^ a b Nessen, Stephen (June 17, 2015), Nearly 30 Years and $3.5 Billion Later, NYC Gets Its First Filtration Plant, WNYC, retrieved January 9, 2017
  15. ^ Depalma, Anthony (March 25, 2004). "Water Hazard?; Plan to Put Filtration Plant Under Park Angers the Bronx". The New York Times. ISSN 0362-4331. Retrieved January 9, 2017.
  16. ^ Rohde, David (May 20, 1998). "Pressed by U.S., City Hall Agrees To Build a Plant to Filter Water". The New York Times. ISSN 0362-4331. Retrieved January 9, 2017.
  17. ^ "World's Longest Water Tunnel". Popular Science: 35. December 1932. Retrieved September 27, 2011.
  18. ^ Chan, Sewel. "Tunnelers Hit Something Big: A Milestone". The New York Times. Retrieved April 7, 2016.
  19. ^ "Drinking Water Sampling Stations". Welcome to Retrieved August 30, 2018.
  20. ^ Robbins, Tom (September 1, 2009). "Water, Water, Everywhere in Mayoral Race". The Village Voice. Archived from the original on February 13, 2010. Retrieved February 20, 2010.
  21. ^ Belson, Ken (November 22, 2008). "Plumber's Job on a Giant's Scale: Fixing New York's Drinking Straw". The New York Times. Retrieved June 17, 2013.
  22. ^ Royte, Elizabeth (2008). Bottlemania: How Water Went on Sale and Why We Bought It. New York: Bloomsbury USA. p. 132. ISBN 978-1-59691-371-4.
  23. ^ Winnie Hu (January 18, 2018). "A Billion-Dollar Investment in New York's Water". The New York Times. Retrieved January 18, 2018.

Further readingEdit

  • Galusha, Diane (1999). Liquid Assets: A History of New York City's Water System. Fleischmanns, NY: Purple Mountain Press. ISBN 0-916346-73-0.
  • Koeppel, Gerard T. (2000). Water for Gotham: A History. Princeton, NJ: Princeton University Press. ISBN 0-691-01139-7.

External linksEdit