Mackenzie River east into the Churchill River. The eastern portion of the Mackenzie basin is dominated by vast reaches of lake-studded boreal forest and includes many of the largest lakes in North America. By both volume and surface area, Great Bear Lake is the biggest in the watershed and third largest on the continent, with a surface area of and a volume of . Great Slave Lake is slightly smaller, with an area of and containing of water, although it is significantly deeper than Great Bear. The third major lake, Athabasca, is less than a third that size with an area of
Whitesand River (Lake Nipigon) and then another southeast to its mouth at Lake Nipigon, for a total distance from Selassie Lake of . Whitesand River (Lake Nipigon) The Whitesand River is a river in Thunder Bay District, Ontario, Canada, that flows south into the northwest side of Lake Nipigon. Another river in Thunder Bay District with the same name, Whitesand River (Hewitson River), lies further southeast and flows into Lake Superior via the Hewitson River. The river begins at Selassie Lake at an elevation of . Selassie Lake is adjacent to Haile Lake, which also flows into Lake Nipigon, but via the Pikitigushi River