Suncook River Reservoir is fed by the Suncook River, a 35.7-mile-long tributary of the Merrimack River. The reservoir is located near the towns of Center Barnstead and Pittsfield, where the river passes through a 19th-century dam. The Suncook River is known for its dramatic channel change in 2006, when a flood caused it to cut a new shorter course in Epsom, leaving two previous channels dry.