Welcome to Fresh Pond! Fresh Pond Reservation consists of 162 acres of open space surrounding and protecting the 155 acre Fresh Pond Reservoir. Fresh Pond Reservoir is a vital part of the drinking water supply system for the City of Cambridge. Fresh Pond is fed by the water supply's important upland reservoirs: Hobbs Brook Reservoir in Lincoln, Lexington, and Waltham, and Stony Brook Reservoir in Weston and Waltham. Raw water from Fresh Pond is purified at the adjacent Walter J. Sullivan Water Treatment Facility and pumped to Payson Park Reservoir in Belmont. From there it flows back to the city by gravity, providing drinking water to the residents and businesses of Cambridge.