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.
The Delaware Aqueduct carries the water from the 95-square-mile (250 km2), 49.6-billion-US-gallon (188-million-cubic-metre) watershed Rondout Reservoir and the Cannonsville, Neversink, and Pepacton reservoirs via the Delaware and Neversink tunnels.
According to en.wikipedia