Mackenzie River
At , the Mackenzie River drainage basin encompasses nearly 20 percent of Canada. About , or 54 percent of the basin, lies above Great Slave Lake. Permafrost underlies about three-quarters of the watershed, reaching up to deep in the Mackenzie Delta. As a whole, the Mackenzie basin receives only meager to moderate rainfall, averaging over the entire basin, though mountain areas experience much higher precipitation, and areas near and north of the Arctic Circle receive much lower precipitation.
Mackenzie River
The Mackenzie drainage basin is bordered by multiple major North American watersheds. Much of the western edge of the Mackenzie basin runs along the Continental Divide. The divide separates the Mackenzie watershed from that of the Yukon River, which flows to the Bering Strait; and the Fraser River and Columbia River systems, both of which empty into the Pacific Ocean. Lowland divides in the north separate the Mackenzie basin from the Arctic Ocean watersheds of the Anderson, Horton, Coppermine and Back Rivers. In the east, the Mackenzie borders on the Hudson Bay watersheds of the Thelon and Churchill Rivers, and to the south it is bordered by the Saskatchewan–Nelson River system, which also empties into Hudson Bay. The Mackenzie system is hydrologically connected to the Hudson Bay watershed via Wollaston Lake, which is not only the source of the Fond du Lac tributary of Lake Athabasca, but also of the Cochrane River, which flows east into the Churchill River.