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Hydroelectricity

Although there are no dams along the main stem of the Mackenzie, many of its tributaries and headwaters have been developed for hydroelectricity production, flood control and irrigation. The W.A.C. Bennett and Peace Canyon hydroelectric dams on the upper Peace River were completed in 1968 and 1980 by BC Hydro. They have a combined capacity of more than 3,600 megawatts (MW). The reservoir of W.A.C. Bennett, Williston Lake, is the largest body of fresh water in BC and the ninth largest man-made lake in the world, with a volume of 70.3 km (57,000,000 acre⋅ft). Other smaller hydroelectric plants are located along the Snare and Taltson River tributaries, providing power to mines in the Great Slave Lake region.

By acting as a massive stabilizer on the water flow of the Peace River, Williston Lake reduces flood crests on the Peace, Slave and Mackenzie rivers as far downstream as Fort Good Hope. This has made the Peace Valley more suitable for farming, but has had significant impacts on downstream wildlife and riparian communities. The more stable annual flow slows down the spread of essential nutrients which builds up in the form of sediments, thus causing the river to become more polluted.

There have been many proposals to dam the tributaries of the Mackenzie River which would lead to further impacts on water quality and seasonal flow patterns. A potential US$ 1 billion, 1350 MW hydro plant on the Slave River was canceled in 2010 after an agreement could not be reached with First Nations people in the area to be flooded by the reservoir. The Site C Dam on the Peace River, which would generate enough power for about 460,000 households, has been controversial since the 1970s. As of April 2019, despite multiple legal challenges by First Nations and environmental groups the dam was under construction, with a completion date scheduled for 2024.