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
Oil sands sands and merge at Lake Athabasca to form the Slave River, which flows into the MacKenzie River, one of the largest rivers in the world. All of the water from these rivers flow into the Arctic Ocean. The Peace River oil sands probably contain over 30 billion cubic metres (200 billion barrels) of oil-in-place. The thickness of the deposit ranges from and it is buried about deep. Whereas the Athabasca oil sands lie close enough to the surface that the bitumen can be excavated in open-pit mines, the smaller Peace River deposits are too deep, and must be exploited using