NYC Considers Expanding Cannonsville Reservoir in Upstate New York

By Y.M. Lowy

Most New Yorkers probably have never heard of the Cannonsville Reservoir, but the massive body of water in Delaware County plays an important role in keeping the city’s taps running.

Cannonsville is New York City’s third-largest source of drinking water and holds about 96 billion gallons. Along with the Pepacton and Neversink reservoirs, it is part of the city’s Delaware water system, which supplies about half of the city’s drinking water.

The Delaware River Basin Commission is now conducting an 18-month feasibility study looking at whether Cannonsville could be expanded to store more water. The study will examine how much additional water could be stored, the cost of the project, permitting requirements and the area’s geology and water patterns.

The idea comes after a serious drought in 2024, when New York City issued its first drought warning in more than 20 years. The city’s reservoir system dropped to around 60% capacity, compared with the normal range of roughly the mid-70s to low 80s.

That drought also delayed a major project to repair the Delaware Aqueduct, the system that carries water from the Delaware reservoirs toward New York City. The aqueduct loses about 35 million gallons of water every day through leaks.

Cannonsville has faced severe dry conditions before. More than 20 years ago, the reservoir dropped to just 3.4% of its capacity.

The Delaware River Basin Commission has been studying ways to increase water storage since 2020. Its earlier work looked at more than 2,500 possible options, including expanding existing reservoirs, building new ones and even using former quarries for water storage.

The Cannonsville expansion is now among the options being studied more closely. Any expansion would be a major undertaking involving engineering, environmental reviews, safety considerations and permitting. Officials expect to have the findings by mid-2028.