The source of New York City’s drinking water is generally not well understood by the people it supplies. Yet it is imperative that people understand where their water comes from so that they are motivated to monitor and protect their cherished resources. Below are key facts about the New York City drinking water supply.

Water Capacity

The NYC Watershed supplies up to 1.5 billion gallons of unfiltered drinking water per day to more than 9 million people – approximately half the population of the State. In addition to serving New York City, there are more than 60 connections and provide an average of 120 million gallons per days to approximately 1 million people in parts of Westchester, Putnam, Orange and Ulster Counties. The system's total storage capacity is 580 billion gallons.

The NYC Watershed

The NYC Watershed covers approximately 2,000 square miles of land in the Hudson Valley and Catskill Mountains, both east and west of the Hudson River. The NYC Watershed contains 19 reservoirs and 3 controlled lakes that sit in 3 sub-watersheds: the Croton, the Catskill, and the Delaware.

The Croton System

The oldest system, the Croton Watershed, covers approximately 360 square miles and is located east of the Hudson River. It was first formed by damming the Croton River in 1842, and later enlarged when the New Croton Dam was built in 1905. The Croton system is comprised of 10 reservoirs (Amawalk, Bog Brook, Cross River, Croton Falls, Diverting, East Branch, Middle Branch, New Croton, Muscoot, and Titicus) and 3 controlled lakes (Kirk Lake, Lake Gilead, Lake Gleneida). The Croton system can store 87 billion gallons and typically provides approximately 10 % of the City’s supply, and up to 30% in times of drought.

The Catskill System

The Catskill system was created in the early 1900s and covers approximately 600 square miles. The Catskill system is comprised of Ashokan and Schoharie Reservoirs, which sit west of the Hudson River. After traveling through aqueducts under the Hudson River, water from this system combines with that from the Delaware system in 3 additional reservoirs (Boyds Corners, Kensico, West Branch), which sit east of the Hudson River. The Catskill system can store 124 billion gallons and typically provides approximately 40% of the City’s supply.

The Delaware System

Construction of the Delaware system took place between 1937 and 1964. It covers approximately 1,000 square miles, and is comprised of 4 reservoirs (Cannonsville, Neversink, Pepacton, and Roundout) that sit west of the Hudson River, and like the Catskill system, this supply feeds into the 3 additional Cat/Del reservoirs that sit east of the Hudson River. The Delaware system can store 320 billion gallons and typically provides approximately 50% of the City’s supply.

Interconnections

Although the NYC Watershed is comprised of 3 sub-watersheds, the system was designed with various interconnections that can transfer water from one system to another and allow the City to have some flexibility in controlling flows and distribution. Although these systems are geographically distinct, they are interrelated, and contaminants that threaten one system can, at times, make their way into another. Thus, strong watershed protection programs must be in place to protect the entire NYC Watershed.

Drought Management

The City Department of Environmental Protection monitors daily reservoir storage levels, inflows, and releases to assure a steady supply of water from the system. In times of drought, the City will implement conservation measures and also modify operations to supplement supplies. The City’s Drought Management Plan has 3 phases: Drought Watch, Drought Warning and Drought Emergency.