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
Mackenzie River is scant, despite the efforts of many researchers. Many archaeological sites have probably been destroyed by flooding, freeze-thaw and erosion. The Inuvialuit, Gwich'in and other indigenous peoples have lived along the river for thousands of years; however, the oldest evidence of continuous occupation stretches back only about 1300–1400 years, at the Gwich'in community of Tsiigehtchic. The Mackenzie provided the major route into Canada's northern interior for European explorers as early as the late 18th century. Scottish explorer Alexander Mackenzie travelled the river in the hope it would lead to the Pacific Ocean, but instead reached its mouth on the Arctic