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
Fond du Lac River (Saskatchewan) The river leaves the lake on the northwest side near the community of Black Lake, travels over the Elizabeth Falls and the Woodcock Rapids, flows past the community of Stony Rapids, and reaches its mouth at Lake Athabasca. The river also supports a number of fish species. These include walleye, yellow perch, northern pike, lake trout, Arctic grayling, lake whitefish, cisco, white sucker, longnose sucker and burbot. Fond du Lac River (Saskatchewan) The Fond du Lac River is one of the upper branches of the Mackenzie River system, draining into the Arctic Ocean, located in northern Saskatchewan, Canada. The river