Most of New York’s water comes from the Catskill/Delaware watershed (more than a million acres of land) 40% of which is owned by the state, the city or non-profit organisations. A lot of effort is directed at ensuring the source supply itself is protected – front of pipe rather than end of pipe solutions – and development is regulated to prevent pollutants from getting into the water supply. It can take up to a year for water to get to the city from the Catskills watershed and all of New York’s water is supplied to the city by gravity – pretty impressive. More information and diagrams here.
How New York gets its water – USA – ech2o newsletter snippet