Chapel Brook of Franklin County, Massachusetts is the name of a tributary of the South River (of the Deerfield River watershed) and the name of a 173-acre (70 ha) open space preserve located along the brook. The brook, est. 3.79 mi (6 km) long, is located in southeast Ashfield and southwest Conway. It drains into Poland Brook, thence into the South River, the Deerfield River, the Connecticut River, and Long Island Sound. The Chapel Brook reservation, managed by the non-profit conservation organization The Trustees of Reservations, is located in Ashfield and contains Chapel Falls, a series of three waterfalls on Chapel Brook, measuring 10 feet (3.0 m), 15 feet (4.6 m) and 20 feet (6.1 m) high; and Pony Mountain (also called Chapel Ledge) est.