Water Systems Overview

NYC receives 90% of its water from the Delaware and Catskill Watershed. These are two watersheds that are next to each other. This combined watershed is 1,600 square miles, which is larger than the state of Rhode Island! Take a look at the watershed on the map. What colors do you see and what do you think they represent?   

These watersheds are 75% forested. The remaining 25% is occupied by small and mid-sized farms, private homes and small towns.

These watersheds are about 100 miles away from the city, which is more than 2 hour drive by car! The water travels a long way to arrive at the houses of New Yorkers. Therefore, the water makes stops in several reservoirs until it arrives in the city.

• The water travels through aqueducts. Aqueduct in Latin means roots of water. Aqueducts are a series of tunnels, pipes, channels and canals that transport water from one location to another. 

• In New York, the aqueducts consist of hundreds of miles of pipes and tunnels.

Let’s explore some of the important reservoirs that are within the Delaware and Catskill Watersheds.

The Pepacton Reservoir is in the Delaware Watershed. It is a man-made reservoir that was created by damming the Delaware River.

• A dam is a barrier that restricts the flow of water.  

The Pepacton Reservoir was built in 1955. It is almost 15 miles long and delivers 25% of NYC’s water flow everyday. It can hold up to 140 billion gallons! On the map, you will see a red line that goes from the Pepacton Reservoir to the Rondout Reservoir.

Take a look at the picture of the Ashokan Reservoir.

The Ashokan Reservoir is in the Catskill Watershed. If you look closely on the map, you will see a dark blue line that separates the reservoir into 2 parts. These 2 parts are called basins. Basins are gigantic containers of water. These two basins hold up to 120 billion gallons of water!

Zoom out to find the Catskill Aqueduct on the map. What color is it? Follow this aqueduct by dragging the map. This aqueduct travels down all the way to the next green area, which is the Croton Watershed. 

The Croton Watershed is located about 30 miles north of Lower Manhattan and spans over 375 square miles. New York City struggled with unhealthy and unreliable water for 50 years before the Croton Aqueduct was built. In 1832, a deadly disease called Cholera spread through the city’s polluted water system. Three years later, the City government looked north to what is today Westchester County for a fresh source of water. Back then, the Croton Watershed was mostly forests, some farmland, and small towns which meant the water was kept free of pollution from the growing population of the City.

Today, the Croton Watershed provides 10% of the City's daily water needs. The Croton Water Filtration plant, completed in 2015, keeps this water clean and healthy. The Croton Watershed remains an important part of our water system and can be used to supply up to 30% of the City’s daily use in an emergency, such as a drought.

Use the Zoom button to help you. We’ll explore two of them below.

In 1898, New York City had grown to include Brooklyn and Staten Island as boroughs. Since the city now had more people, it needed to continue enhancing its water system. Another dam would be built at the Cross River, thus creating the Cross River Reservoir in 1908.

The construction of this dam caused tension between the city and the residents who were displaced, "(forced to leave their homes)", by the building of the dam. This conflict between NYC and residents living upstate would repeat with the building of many other reservoirs. 

Today, the Cross River Reservoir has one basin, which holds 10.3 billion gallons of water at capacity.

This NYC Reservoir is about 3.4 square miles and sits within the Croton Watershed but is actually a part of the Delaware/Catskills Watershed System. It is the last stop before the water goes down to NYC. Two Aqueduct pipes flow from here into the much smaller Hillview Reservoir in Yonkers for distribution throughout New York City.

Here we can revisit Delaware/Catskill Watershed’s Reservoirs. All together the reservoirs can hold over 550 Billion gallons of water. The vast majority of our water comes from the Delaware/Catskill System.

Take a minute to revisit these upstate reservoirs with the buttons below.

Catskill:

Delaware:

Largest: Pepacton @ 140.2B Gallons 

Newest: Cannonsville finished in 1964 (ALSO Furthest at 125 miles away)

This system has taken over 100 years to build! To make sure this system works for the next 100 years, we need to be able to maintain it.

The Delaware Aqueduct transports about 50% of New York City’s drinking water from reservoirs in the Delaware Watershed. This aqueduct drops deep underground and at 85-miles long is the longest tunnel in the world. The Delaware Aqueduct was built during World War II and has since formed some cracks that need to be repaired.

Today, this aqueduct leaks about 20 million gallons of water daily! The good news is we know how to fix this. The challenge is building a new piece of the tunnel 600-800 feet below the Hudson River. This is the largest and most complex repair in the history of our water supply. When complete in 2023, the Delaware Aqueduct will be shut down for months, a new section of the aqueduct will be put in place, and you won’t even notice.

"The TBM was named in honor of Nora Stanton Barney, a noted suffragist and the first woman in the United States to earn a college degree in civil engineering."