NY City water priorities map

Title Info
Conservation Ecosystem services
Lessons Ecosystem services
New York City watershed priorities map
Related materials: NY City Water
Where does your drinking water come from? Click the Related materials link to learn how -- and from where -- New York City gets its water supply.

This map, produced by New York City's Department of Environmental Projection, shows the reservoirs and aqueducts that have been developed over the past two centuries to supply the city's residents with clean water. In addition, the different colors signify different types of land ownership and the degree of priority in the DEP's land acquisition program: the green areas are either state- or city-owned land, and the top priority areas are red and purple. Note that the highest priority areas tend to be closest to the reservoirs, where land protection will have the greatest impact on protecting water quality. Map courtesy of: NYC DEP ? 1997.

New York City Water Supply History

New York City is one of the world's twenty largest cities, yet the city's eight million residents receive some of the safest, best-tasting water of any urban area in the world. Most of the city's population lives on the islands of Manhattan, Long Island, and Staten Island -- none of which have large freshwaterwater resources -- so how is it possible that all these people receive such superb water every day? The short answer is: excellent planning and excellent use of ecosystem services.

In the early 1800s it became clear that the springs and wells that had supplied the city's residents no longer supplied enough water and were also becoming polluted. Although the nearby Hudson River was originally considered as a water source, because the river is an estuary its waters proved to be too brackish (that is, saltier than freshwater). In a prescient move, the city developed a system to bring water in from the Croton River, about 40 miles away. Engineers dammed the river, and created a reservoir and associated aqueduct to carry water to the city; the system became functional in 1842. In the 1880s and 1890s the city added further reservoir capacity in the Croton watershed and built a second aqueduct that began operation in 1890.

By 1900, the city had a population of about 3.5 million, and the search for further sources of water led to the Catskill Mountain region, almost 100 miles to the north. By 1915, the Ashokan Reservoir and the associated Catskill Aqueduct had been completed and were supplying water to the city, and by 1928 the Schoharie Reservoir and the 18 mile long Shandaken Tunnel had been added to the system. After a series of legal delays that went all the way to the United States Supreme Court, the city began expanding the upstate water system further west into the Delaware River watershed in 1937. Over the next 27 years the Delaware Aqueduct (1944) and the following reservoirs were added to the system: Rondout (1950), Neversink (1954), Pepacton (1955), and Cannonsville (1964). All of these efforts were made looking 25-50 years ahead, in an attempt to provide good water for the future population of the city.

Today, New York City's drinking water is supplied by a total network of 3 controlled lakes and 19 reservoirs in a 1,972 square mile (5,100 sq km) watershed that extends 125 miles (200 km) to the north and west of the city of New York. The current system of reservoirs can hold a total of 580 billion gallons (over 2 trillion liters) and daily delivers about 1.3 billion gallons (almost 5 billion liters) to the 8 million people of New York City plus another million in the upstate region (click to see a map of New York City's water supply system ).

Ecosystem Services

One of the most amazing aspects of the present-day New York City water system is that none of the system's water passes through complex and expensive water treatment facilities. In 1989 the US Environmental Protection Agency created a rule that all surface water supplies either had to go through water filtration plants or the relevant agencies had to demonstrate control of the watersheds being used. At that time it was estimated that filtration facilities for New York City would cost between $4 and $6 billion to build. The irony of the situation was that due to excellent planning and maintenance the city?s water supply was already good enough that it met Federal water quality standards even without filtration.

After a lengthy period of negotiation, New York City, New York State, the US Environmental Protection Agency, and about sixty local communities signed a Memorandum of Understanding that described a series of specific steps to be taken that would protect and improve the quality of the water system -- demonstrating control of the watershed -- at a cost of over $1 billion. Since then, the funding allocated to the project has more than doubled. The project focused on the watersheds of the upstate reservoirs through a series of programs: purchasing land or conservation easements on land that might otherwise be developed, and implementing conservation programs instead; identifying communities whose sewage and septic systems could be significantly upgraded; and working with farmers to improve their land management practices to safeguard the water system. In the first decade of the program, from 1997 to 2007, the city purchased (or bought conservation easements on) nearly 84,000 acres (34,000 ha) of land. The original land acquisition budget of approximately $300 million has since expanded to $580 million.

While there is potential for significant friction between the city and the upstate communities surrounding the water system, the city has put a great deal of effort into keeping friction to a minimum. Residents may hike, cross-country ski, hunt, and fish on some of the watershed protection land. As another way of avoiding tension with local up-state communities, as part of the Memorandum of Understanding, New York City committed to pay local real estate taxes on the lands and easements it has purchased.

The City's program for protecting the watershed depends on basic ecological and public health knowledge, along with a great deal of applied research. For instance, scientists have discovered that the disease-causing organisms Giardia and Cryptosporidium can survive as long as 60 days between the time they are shed into the environment and the time they reach a human host. However, some parts of the upstate watersheds have a "travel time" as short as three days or even less (in other words, water from those areas can reach taps in New York City in three days or less). As a result, those areas with travel times of less than 60 days became top priority areas for protection (see priorities map; Priority Areas 1A and 1B are within the 60-day travel time).

The City's Department of Environmental Protection actively manages the region's forests with a number of goals in mind: forest stands are managed and cut so that large areas of same aged trees do not cover the landscape (these forests would be especially vulnerable in a hurricane or major wind storm). In addition, specific measures are being taken to prevent invasive, exotic species from becoming established. To prevent the Asian long-horned beetle (Anoplophora glabripennis) from spreading to the area (it is currently killing trees in New York City), the movement of firewood across the Catskill and Delaware watersheds is restricted. And, to keep zebra mussels (Dreissena polymorpha) from infesting the reservoirs, boat-owners may only use their boats in a single reservoir -- before they bring a new boat to a reservoir it must be steam-cleaned. By protecting forested land (and allowing forests to regrow on some of the purchased lands), the watershed's human residents receive protection for their local aquifers while forest species gain additional habitat and new corridors between existing blocks of publicly-owned land. Finally, scenic views are protected or enhanced by the land acquisition efforts.

By paying careful attention to the interactions among natural ecosystems, humans, and water supplies, the city has been able to benefit from the services provided by healthy ecosystems. The arrangement benefits native ecosystems and species in the upstate region, human health in the city and upstate, and the budgets of all the parties.

Further Resources:

New York City Water Supply Watersheds: http://home2.nyc.gov/html/dep/html/watershed_protection/home.html

New York City Department of Environmental Protection: http://www.nyc.gov/html/dep/html/home/home.shtml

Committee to Review the New York City Watershed Management Strategy. (2000). Watershed Management for Potable Water Supply: Assessing the New York City Strategy. National Academy Press, Washington, D.C. This book can be read online at: http://www.nap.edu/catalog.php?record_id=9677  

A report from the US Environmental Protection Agency: A Landscape Analysis of New York City's Water Supply: http://www.epa.gov/nerlesd1/land-sci/ny.htm