Cooper Lake, located near Lake Hill in the Town of Woodstock, Ulster County, New York, is the largest natural lake in the Catskill Mountains. However, it has been expanded somewhat over the years since it serves as the main reservoir for the nearby City of Kingston and Town of Ulster, which stores water there that it pipes from Mink Hollow Stream in addition to the water that reaches the lake from its 8.6-square mile (22.4 km2) drainage basin. It holds roughly 1.2 e9USgal to the city a year; providing an average of 4.6 e6USgal a day to Kingston and Ulster. Operational since 1899, the Edmund T. Cloonan Water Treatment Plant treats Cooper Lake water with chlorine, alum filtration, and lime corrosion control. Its laboratory conducts bacteriological examinations and offers public access for water testing, aiding community monitoring efforts. Since it is a water supply, boating, swimming and fishing in Cooper Lake are prohibited. The area of Cooper Lake and the surrounding grounds is owned by City of Kingston Water Department.