The Catskill Aqueduct is an aqueduct in the New York City water supply system which brings water from the Catskill Mountains to Kensico Dam in Westchester County, New York. There it joins with waters from the Kensico watershed and the Delaware Aqueduct. After mixing and settling, the flow from Kensico continues in the aqueduct to the Hillview Reservoir in Yonkers for distribution in New York City.
The aqueduct is fed by the waters of the Schoharie and Ashokan reservoirs located in Ulster County.
History Construction began in 1907. Numerous test shafts were dug to determine the stability of the area's sub-surface geology to ensure both the impermeability of the completed reservoirs and holding strength of their various levees, tunnels, dikes, and dams, and the integrity of the structures of the aqueduct.The Catskill Aqueduct, Cassier's Magazine - An Engineering Monthly, Volume XL, May-October 1911, pp. 252-272, 323-344, 437-461 The aqueduct proper was completed in 1916 and the entire Catskill Aqueduct system including three dams and 67 shafts was completed in 1924.A history of the NYC water supply system - Merguerian, 2000c The total cost of constructing the system, less interest on the bonds to finance it, was $177 million ($ in ).Catskill Water Supply: A General Description and Brief History
Specifications The aqueduct consists of of cut and cover aqueduct, over of grade tunnel, of pressure tunnel, and of steel siphon.Kevin Bone, ed. Water-Works: The Architecture and Engineering of the New York City Water Supply (New York: Monacelli, 2006), 258. The 67 shafts sunk for various purposes on the aqueduct and City Tunnel vary in depth from . Water flows by gravity through the aqueduct at a rate of about .Water Supply and Distribution Timeline – Greatest Engineering Achievements of the Twentieth Century
The Catskill Aqueduct has an operational capacity of about per day north of the Kensico Reservoir in Valhalla, New York. Capacity in the section of the aqueduct south of Kensico Reservoir to the Hillview Reservoir in Yonkers, New York is per day.New York City water supply system The aqueduct normally operates well below capacity with daily averages around of water per day. About 40% of New York City's water supply flows through the Catskill Aqueduct.
Geography The Catskill Aqueduct begins at the Ashokan Reservoir in Olivebridge, New York, located in Ulster County, which is fed by its own watershed and flow from the upstream Schoharie Reservoir. The aqueduct traverses in a southeasterly direction, first tunneling beneath the Rondout Valley and Rondout Creek in the town of Marbletown, then beneath the Wallkill River in the town of Gardiner in Ulster County before flowing toward Orange County. At Storm King Mountain it crosses below the Hudson River to Breakneck Mountain in Putnam County on the east side of the river.The Hudson River Guidebook By Arthur G. Adams
The aqueduct then enters Westchester County, and flows to the Kensico Reservoir, where it joins with waters of the Kensico drainage basin and the city's Delaware Aqueduct. It continues from Kensico and terminates at the Hillview Reservoir in Yonkers. The Hillview Reservoir then feeds City Tunnels 1 and 2, which bring water to New York City. If necessary, water can be made to bypass both reservoirs.
References
See also Delaware Aqueduct New York City water supply system Frank E. Winsor the engineer in charge of construction of of the Aqueduct.