Mackenzie River Mackenzie River The Mackenzie River (Slavey language: Deh-Cho , "big river" or Inuvialuktun: Kuukpak , "great river"; ) is the longest river system in Canada, and has the second largest drainage basin of any North American river after the Mississippi River. The Mackenzie River flows through a vast, thinly populated region of forest and tundra entirely within the Canadian Northwest Territories, although its many tributaries reach into four other Canadian provinces and territories. The river's main stem is long, flowing north-northwest from Great Slave Lake into the Arctic Ocean, where it forms a large delta at its mouth. Its extensive
Mackenzie River Arctic Red confluence it is . Mackenzie monthly mean discharge at Arctic Red River (m/s)<br> As recently as the last glacial maximum about 30,000 years ago, the majority of northern Canada was buried under the enormous continental Laurentide ice sheet. The tremendous erosive powers of the Laurentide and its predecessors, at maximum extent, completely buried what is now the Mackenzie watershed under thousands of metres of ice and flattened the eastern portions of the watershed. When the ice sheet receded for the last time, it left a long postglacial lake, Lake McConnell, of which Great Bear, Great Slave and Athabasca