New York City, USA

The City of New York has in effect one of the largest unfiltered surface water supplies in the world, which currently uses three major catchment areas, known as the Croton, Catskills and Delaware systems, each with a long history of watershed development and protection.

New York City © Mat Rick Photography/

As the largest city in North America, New York City has long been famed for the quality of its drinking water.

The city's water supply is stored in 19 upstream reservoirs which are fed by a 2,000-square mile watershed that remains approximately 96% forested. Every day more than 1 billion gallons of freshwater are moved as much as 125 miles to reach the city's taps. The story of New York City's drinking water is a classic example of how using nature to filter and treat water can be more efficient and cost effective than the most sophisticated water treatment plant.

Pepacton Reservoir © Josh Marinelli

In the 1990s, New York City needed to demonstrate to state and federal regulators that they could comply with the Safe Drinking Water Act. In evaluating their options, the city discovered two potential pathways:

  • Option 1. Build a new water treatment plant for ~$8-10 billion dollars

    It was estimated that a filtration plant large enough to clean the City’s water supply would cost between $8-$10 billion in today’s dollars, approximately $6 billion to build and another $250 million annually to maintain.

  • Option 2. Protect water at its source for a fraction of the cost

    Preserving the watershed was estimated at $1.5 billion, just over a dime invested on ecological preservation for every dollar that would have been spent on a filtration plant.

Today, New York City is investing $1.5 billion over 10 years to preserve its forested watershed, acquire new land, and restore critical habitats; a fraction of the original estimate for $8-10 billion.

These investments have and continue to help keep the city's water supply among the cleanest in the world.