Delaware Aqueduct

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Coordinates: 41°16′56″N 73°40′04″W / 41.282317°N 73.667908°W / 41.282317; -73.667908

Building in Yonkers

The Delaware Aqueduct is an aqueduct in the New York City water supply system. It takes water from the Rondout, Cannonsville, Neversink, and Pepacton reservoirs on the west bank of the Hudson River through the Chelsea Pump Station, then into the West Branch, Kensico, and Hillview reservoirs on the east bank, ending in at Hillview in Yonkers, New York.

The aqueduct was constructed between 1939 and 1945, and carries approximately half of New York City's water supply of 1.3 billion US gallons (4,900,000 m3) per day. At 13.5 feet (4.1 m) wide and 85 miles (137 km) long, the Delaware Aqueduct is the world's longest tunnel.[1]

Reservoirs and watersheds[edit]

The Delaware Aqueduct carries the water from the 95-square-mile (250 km2), 49.6-billion-US-gallon (188-million-cubic-metre) watershed[2] Rondout Reservoir and the Cannonsville, Neversink, and Pepacton reservoirs via the Delaware and Neversink tunnels. (Since those three are in the Delaware River watershed, Rondout is considered by New York City's Department of Environmental Protection to be part of the Delaware system despite being firmly within the Hudson River watershed itself.)

Combined, the four reservoirs account for 1,012 square miles (2,620 km2) of watershed and 320.4 billion US gallons (1.2 billion cubic metres) of capacity, 890 million US gallons (3.4 million cubic metres) of which goes to the city daily — 50% of the entire system's. All this water is fed from the Rondout to West Branch Reservoir in Putnam County (part of the Croton River watershed, which includes the flow of the upstream Boyds Corner Reservoir), then to the Kensico, and Hillview reservoirs in southern Westchester County, before continuing on to distribution within New York City.

Leak problems[edit]

The Delaware Aqueduct leaks up to 36 million US gallons (140,000 m3) per day.[3] A $1 billion project to repair the leaking was scheduled to begin in January 2013.[4]

Since the late 1970s, the New York City Department of Environmental Protection (NYCDEP) has been monitoring two leaks that collectively release between 10 and 36 million US gallons (38,000 and 136,000 m3) of water per day.[5] These leaks have caused many problems with flooding and drinking water contamination, particularly for residents of Wawarsing, New York.

In the town of Newburgh, 35 miles (56 km) southeast, residents thought that a stream bubbling out of a wetlands was a natural artesian well; in reality, the water was coming out of a 36-square-foot (3.3 m2) tunnel carved out by the force of water blasting from a crack in the aqueduct buried 650 feet (300m) underground. Combined with the leak in Wawarsing, the NYCDEP admitted in the early 1990s that the aqueduct was leaking at a rate of up to 35 million US gallons (130,000 m3) a day, enough water to supply nearly half a million people.

New York Bypass[edit]

The NYCDEP is building a 2.5-mile (4.0 km) Rondout-West Branch Bypass Tunnel beneath the Hudson, which will allow it to bypass the leak. Construction began in November 2013 and is expected to be finished sometime in 2021. "The number's going to be $1.5 billion to do the entire program to make the fix," said Paul Rush, Deputy Commissioner of the NYCDEP. "About two-thirds of it, $1 billion, will actually go into constructing a bypass tunnel around the location with the most significant leakage in Roseton, and to do additional concrete grouting in the Wawarsing section."[6]

The new bypass tunnel will be one of the most complicated undertakings in the NYCDEP's history. Near the end of construction, the entire Delaware Aqueduct will be shut down to allow the bypass to be connected. It will be dewatered so that the leaks in Wawarsing, and Newburgh, can be fixed. Shutting the aqueduct will deprive New York City of nearly half its water supply. To compensate, the NYCDEP is making improvements to other parts of the system.[citation needed]

Construction on the portion of the bypass tunnel that crosses under the Hudson River from Newburgh to Wappinger began on January 8, 2018 in Newburgh. The tunnel boring machine, named NORA after Nora Stanton Blatch Deforest Barney, reached Wappinger on August 13, 2019, after drilling through of 12,448 feet of bedrock located 700 to 800 feet below ground level.[7]

See also[edit]


  1. ^ List of longest tunnels#World's longest tunnels (in use)
  2. ^ Rondout Reservoir at NYCDEP site; retrieved November 17, 2006.
  3. ^ "Bypass Planned for Leaky New York Aqueduct". The New York Times. November 19, 2010. Retrieved 2010-11-20. The tunnel, to be built under the Hudson River and parts of Dutchess and Orange Counties, will address a problem that has daunted the city since leaks were first discovered in the Delaware Aqueduct in 1988: some 15 to 35 million US gallons (57,000 to 132,000 m3) of water, coming down from the Catskills, have been escaping daily through cracks.
  4. ^ "Work to Begin on $1B Repair of NYC Aqueduct Tunnel". NBC New York. January 2013. Retrieved 18 November 2014.
  5. ^ "Preparation Underway to Fix Leak in Delaware Aqueduct" (Press release). NYC Department of Environmental Protection. March 6, 2008. Retrieved February 20, 2010.
  6. ^ "Why New Yorkers should be worried about their water supply". August 6, 2014. Retrieved August 6, 2014.
  7. ^ Cordero, Katelyn (August 22, 2019). "'NORA' reaches Wappinger as Delaware Aqueduct repair project hits milestone". Retrieved August 23, 2019.

Further reading[edit]

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