Stillwater Lake's dam is an earthfill structure, 1,700 feet long and rises 75 feet above the streambed, with a spillway and gate controlled outlet. The reservoir has a storage capacity of 11,600 acre feet at spillway crest, and controls a drainage area of 36.8 square miles. The project reduces flood heights on the Lackawanna River, downstream of the dam and on the Susquehanna River, downstream from its confluence with the Lackawanna River.