Mackenzie River from the Peace-Athabasca system are significantly slowed by the delta area at the western end of Lake Athabasca causing the lake to rise, and the excess water can only flow out after the rivers have receded. The same phenomenon occurs at Great Slave Lake, which naturally regulates the flow from the Slave River into the Mackenzie. There are river gages at several upstream points along the Mackenzie River. The average flow rate at the outlet of Great Slave Lake is . At Fort Simpson, below the Liard River, it is . At Norman Wells it is , and at the
Rapid River (Cree River tributary) flow via the Cree River, the Fond du Lac River and the Mackenzie River to the Arctic Ocean. Rapid River (Cree River tributary) The Rapid River is a river in northern Saskatchewan, Canada. It is part of the Mackenzie River drainage basin. The Rapid River begins at an unnamed lake at an elevation of . It travels north to Kirsch Lake at an elevation of , where it takes in several unnamed tributaries, including one from the left arriving from Halliday Lake. The river continues to Parker Lake at an elevation of where it takes in the left tributary Arnold