As one of the largest unfiltered surface water supplies in the world, the NYC Water Supply system delivers over one billion gallons of water to more than 9.8 million New Yorkers every single day!
This includes 100 million gallons per day to 70 communities and institutions outside of New York City. Overall, providing nearly half the population of New York State with the highest quality drinking water right from our Catskill Mountains!
This world class drinking water comes from a network of 19 reservoirs and three controlled lakes spanning across nearly 2,000-square-miles in the Hudson Valley and Catskill Mountains. Two primary surface water supplies make up the system and are known as the Catskill/Delaware Watershed (or West of Hudson Watershed) and the Croton Watershed (or East of Hudson Watershed).
The West of Hudson Watershed (WHO) comprises six enormous reservoirs that stretch across the five counties of Delaware, Greene, Schoharie, Sullivan, and Ulster. In 2021 this system alone provided 88% of the drinking water to New York City. The remaining 12 percent of water was supplied by the East of Hudson (EOH) watershed which is located within parts of Westchester, Putnam and Dutchess counties and Fairfield County, CT.
The sources of this massive watershed system include rivers, lakes, streams, ponds, reservoirs, springs, and wells. These water bodies are seasonally recharged from precipitation and subsequent runoff from rain, snow, and sleet events that occur throughout the watershed.
As the water travels from higher to lower elevations it is transported by streams and rivers directly to the numerous reservoirs in the watersheds. From there, a system of gravity fed underground aqueducts and tunnels moves the water to terminal reservoirs before reaching New York City’s distribution system.
As the surface water travels throughout the region, contaminants and substances from animals, human activities or naturally occurring minerals and materials can accumulate in the water. Contaminants that may be detected include sediments, metals, oils, nutrients, pesticides, herbicides, bacteria and viruses.
To ensure the water is safe to consume the New York State Department of Health (NYSDOH) and the United States Environmental Protection Agency (EPA) impose regulations that limit the amount of certain contaminants in water provided by public water systems. These regulations also establish the minimum amount of testing and monitoring that must take place to ensure the water is safe to consume.
New York City is one of only five large cities in the country with a surface drinking water supply that does not utilize filtration as a form of treatment.
This high quality Catskill/ Delaware supply operates under a filtration waiver, referred to as the “Filtration Avoidance Determination” (FAD), and the water from this supply is treated using chlorine and ultraviolet light, two forms of disinfection to reduce microbial risk. NYC DEP continually monitors the sources of water supply in the distribution system, upstate reservoirs, and feeder streams.
They perform routine samples and testing for numerous water quality parameters, including microbiological, chemical, and physical measures, throughout the watershed and as the water enters the distribution system.
In 2017, NYSDOH issued the current FAD that allows DEP to continue operating the Catskill/Delaware supply without filtration through at least 2027. An estimated $1 billion has been committed by DEP to comply with the requirements of the FAD.
This funding is designated towards programs throughout the watershed to help conserve watershed lands, upgrade wastewater infrastructure, implement clean water strategies, and manage streams, forests, and other natural resources that affect the quality of water.
Located in Ulster County, about 13 miles west of Kingston and 73 miles north of New York City, Ashokan Reservoir is formed by the damming of the Esopus Creek, which eventually flows northeast and drains into the Hudson River. Consisting of two basins separated by a concrete dividing weir and roadway, the reservoir holds 122.9 billion gallons at full capacity and was placed into service in 1915.
Located at the intersection of Schoharie, Delaware and Greene Counties, about 36 miles southwest of Albany and roughly 110 miles from New York City, Schoharie Reservoir is formed by the damming of the Schoharie Creek. Schoharie Creek continues north and eventually drains into the Mohawk River, which flows into the Hudson north of Albany. Schoharie Reservoir consists of one basin, almost 6 miles in length and holds 17.6 billion gallons at full capacity. It was placed into service in 1926.
Neversink Reservoir is located in Sullivan County, approximately five miles northeast of the Village of Liberty and more than 75 miles from New York City. It is formed by the damming of the Neversink River, which continues south and eventually drains into the lower Delaware River. It holds 34.9 billion gallons at full capacity and was placed into service in 1954.
Rondout Reservoir straddles the Ulster/Sullivan County border along the southern edge of the Catskill Park, approximately 6 miles northwest of the Village of Ellenville and more than 65 miles northwest of New York City. It is formed by the damming of Rondout Creek, which continues northeastward and eventually drains into the Hudson River at Kingston. It consists of one basin, almost 6.5 miles long and holds 49.6 billion gallons at full capacity. It was placed into service in 1950.
Pepacton Reservoir is located in Delaware County along the southern edge of the State’s forever wild Catskill Park, 12 miles south of the Village of Delhi, and more than 100 miles northwest of New York City. It is formed by the damming of the East Branch of the Delaware River, which continues west and joins the lower Delaware River. It consists of one basin, approximately 15 miles in length and holds 140.2 billion gallons at full capacity, making it the largest reservoir in the City system by volume. It was placed into service in 1955.
Located at the western edge of Delaware County, southwest of the Village of Walton and about 120 miles northwest of New York City, Cannonsville Reservoir is formed by damming the West Branch of the Delaware River, which continues south and becomes part of the lower Delaware River, the border between New York and Pennsylvania. It was placed into service in 1964 and holds 95.7 billion gallons at full capacity.