What is the Hudson Bay drainage basin?

The Hudson Bay drainage basin is the largest drainage basin in Canada, covering about 3.86 million square kilometres or about 39 per cent of Canada's land area. The basin includes most of Manitoba, Ontario, and Quebec, plus parts of Saskatchewan, Alberta, the Northwest Territories, Nunavut, North Dakota, and Minnesota. All rivers in the basin ultimately drain to Hudson Bay and James Bay (and thence to the Atlantic via Hudson Strait).

Major rivers in the basin include the Nelson River system (draining Lake Winnipeg, which itself receives the Red, Saskatchewan, and Winnipeg Rivers); the Albany, Severn, and Winisk Rivers (draining northern Ontario into Hudson Bay and James Bay); the Moose, Abitibi, Kapiskau, and Mattagami Rivers (also draining northern Ontario); the Eastmain, La Grande, Great Whale, and Whale Rivers (draining northern Quebec); the Churchill River (Manitoba-Saskatchewan); and the Rupert River (whose flow was diverted into the Eastmain-La Grande system in 2009 as part of the Eastmain-1-A and Rupert diversion project of the James Bay hydroelectric system).

The Hudson Bay drainage basin is the largest hydroelectric production region in Canada. Manitoba Hydro's Nelson River system (Limestone, Long Spruce, Kettle, Wuskwatim, and Keeyask generating stations) produces about 75 per cent of Manitoba's electricity. Hydro-Quebec's La Grande complex and Robert-Bourassa generating station (the latter at 5,616 megawatts, one of the largest underground power stations in the world) produce a substantial fraction of Quebec's electricity. Ontario Power Generation's Mattagami and Abitibi Rivers generating stations contribute to northern Ontario's electricity supply. Combined hydroelectric capacity in the Hudson Bay basin exceeds 20,000 megawatts.

Indigenous peoples have lived in the Hudson Bay drainage for thousands of years. The Cree of Eeyou Istchee (James Bay), the Mushkegowuk Cree of northern Ontario, the Anishinabeg of southern Manitoba and northern Ontario, and the Innu and Inuit of northern Quebec all hold treaty and Aboriginal title to portions of the basin. Modern agreements include the James Bay and Northern Quebec Agreement (1975), the Treaty 5 (1875 to 1908), the Treaty 9 (1905 to 1906), the Eeyou Marine Region Land Claims Agreement (2010), and the Cree Nation Government Cree Constitution. The basin is part of the Hudson Bay-James Bay Aboriginal Marine Region negotiated with Inuit and Cree, and the federal Tallurutiup Imanga National Marine Conservation Area (2019) protects the eastern entrance to the basin.