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
Lake Winnipesaukee called Acquadocton. Today, the site is called The Weirs, named for the weirs colonists discovered when first exploring the region. Winnipesaukee is a glacial lake but an unusual one, since the last glaciation actually reversed the flow of its waters. Draining the central portion of New Hampshire, it once flowed southeast, leaving via what is now Alton Bay toward the Atlantic Ocean. When glacial debris blocked this path, flow was redirected westward through Paugus Bay into the Winnipesaukee River. The latter flows west from the lake and joins the Pemigewasset River in Franklin to form the Merrimack River, which flows