Sebec Lake extends westward from its overflow into Sebec River in the northern part of Sebec. The lake extends through the northeast corner of Dover-Foxcroft and covers the southwest corner of Bowerbank Township and the southeast corner of Willimantic. Minor south shore tributaries include Bog Brook and Cotton Brook in Dover-Foxcroft, and Smith Brook, Bennett Brook, Ayer Brook, and Badger Brook in Sebec. Minor north shore tributaries include Mill Brook and Grapevine Stream in Bowerbank Township and the larger Bear Brook flowing 6 miles (9.7 km) from Barnard Township. The largest tributaries are Wilson Stream and Ship Pond Stream flowing into the northwest corner of the lake in Willimantic.[2]
Wilson Stream originates in Upper Wilson Pond on the western edge of Bowdoin College Grant West. Tributaries North Brook and South Brook flow into the eastern end of Upper Wilson Pond from Mountain Pond and Horseshoe Pond, respectively. The western end of Upper Wilson Pond overflows into the eastern end of Lower Wilson Pond. Lower Wilson Pond is in the eastern part of Greenville. The southern end of Lower Wilson Pond overflows into Wilson Stream. Wilson Stream flows 17 miles (27 km) south into Sebec Lake. The Appalachian Trail crosses Wilson Stream approximately 6 miles (9.7 km) south of Lower Wilson Pond. Little Wilson Stream flows 8.6 miles east from Shirley to join Wilson Stream approximately 2.5 miles (4.0 km) downstream of the Appalachian Trail crossing. Big Wilson Cliffs and Little Wilson Falls and Gorge are scenic highlights along the Appalachian Trail.[2]
Lake Onawa (or Ship Pond) is in the southeastern corner of Elliotville Township. Long Pond Stream flows 7 miles (11 km) south from the west end of Long Pond to reach the north end of Lake Onawa. The south end of Lake Onawa overflows into Ship Pond Stream which flows 5 miles (8.0 km) south into Sebec Lake. The International Railway of Maine was built along the south shore of Lake Onawa in 1887. One of the highest bridges on the railroad was Ship Pond Viaduct across Ship Pond Stream. The viaduct is 1,230 feet (370 m) long and passes 130 feet (40 m) above Ship Pond Stream.[4]
