The county takes the lead in protecting its watershed areas. Watershed protection is by necessity a major concern in the county. The large number of reservoirs provide drinking water for residents living in Westchester, New York City and several cities in Connecticut. Two estuaries, Long Island Sound and lower Hudson River, provide numerous recreational and economic development opportunities to the entire metropolitan area, making their preservation all the more critical.

Westchester has six major drainage basins. View watersheds map.

Westchester's major watershed areas are:

  • Peekskill & Haverstraw Bay
  • Croton River
  • Pocantico & Saw Mill River
  • Inland Long Island Sound
  • Bronx River
  • Coastal Long Island Sound

The largest reservoir system in the county is part of the New York City water supply system which has three components, the

  • Croton Reservoir Source System, which covers 18,000 acres of land and water surface in Westchester plus additional areas of Putnam County
  • Catskill system
  • Delaware system

Water from the two upstate systems passes through Westchester via aqueducts and the Kensico Reservoir on the way to New York City. The city’s system provides water to 85% of Westchester’s residents.
The Planning Department played a lead role in the Croton/Kensico watershed negotions between the 12 Westchester County municipalities and New York City, which resulted in the historic NYC Watershed Memorandum of Agreement of 1997. Westchester County continues to provide leadership for its 12 watershed municipalities. 

The Bronx River Watershed Coalition, formerly known as Watershed Advisory Committee 7 of the Long Island Sound Watershed, was formed in 2003 as a partnership among Westchester County municipalities and agencies and not-for-profit organizations seeking the same goal: to improve water quality in the Bronx River. Over time, state and New York City agencies joined the effort, too. The coalition sought to achieve its goal by developing a comprehensive management plan, available on this website, which lays out a strategy for limiting the amount of pollution entering the river and its tributaries via stormwater runoff.

Planning Department staff continues to provide administrative and technical support to 19 Westchester County municipalities in the Long Island Sound watershed, promoting water quality and fish and wildlife habitat efforts. The county's nonpoint source pollution control efforts, which dovetail with the Long Island Sound Study, have focused on intermunicipal watershed planning and public outreach/education since 1995. More recent efforts have implemented the watershed management plans, including aquatic restoration. For more information, read about the Long Island Sound Watershed and the Aquatic Restoration programs.

The Indian Brook-Croton Gorge Watershed Conservation Action Plan is a comprehensive watershed plan developed for the Croton Bay Watershed, which consists of the Croton Gorge and Indian Brook subwatersheds. The county produced the report in close collaboration with the towns of Cortlandt, New Castle, Ossining and the villages of Croton-on-Hudson and Ossining.