May 18, 2021
Neighborhoods in New York City receive their drinking water from reservoirs of the Catskill System, Croton System, Delaware System, or a combination of the three systems. The source of drinking water in your neighborhood can change on a day-by-day or hour-by-hour basis depending on patterns of demand, pressure, and other factors. DEP scientists perform thousands of tests on your drinking water each week, and we know that water coming from all our reservoirs is extremely high-quality. Still, the underlying chemistry of each water source is different because of the underlying geology that surrounds our reservoirs in the Catskills and the Hudson Valley. Differences in bedrock and soil can naturally affect pH, alkalinity, calcium content and other commonly measured characteristics of our drinking water.
Water consumers will generally not notice these small differences. However, those who use New York City water to operate industrial equipment and mechanical systems might notice that changes in water chemistry require adjustments to their treatment systems, maintenance regimens and other upkeep routines.
To help with this, DEP regularly updates a map on its website to show the distribution of different water sources throughout the five boroughs. From the end of May until October, DEP expects the reservoir and distribution systems to be in their normal operation condition. That includes water from our Croton System being delivered by gravity, through the New Croton Aqueduct, to low-elevation areas of the Bronx and Manhattan. The remaining parts of the city will receive water from the Catskill and Delaware systems. That configuration will likely change in October when we shut down the Catskill Aqueduct for the final year of a rehabilitation project that will keep the century-old aqueduct in good working order for the next 100 years. We will continue to update our water distribution maps found at the following site: