Great Bear

Excerpt from Mackenzie River Basin: State of the Aquatic Ecosystem Report 2003 by the Mackenzie River Basin Board (p. 169-194). Full report available at


The Mackenzie-Great Bear sub-basin is the largest of the six sub-basins, covering 475,000 square kilometres, or 26% of the entire Mackenzie River Basin. It contains the Mackenzie River, which at 1.800 kilometers in length, is Canada’s longest river. This sub-basin includes the largest lake entirely within Canada, Great Bear Lake, Canada’s largest delta and second largest wetland, the Mackenzie Delta, covering 13,500 square kilometers. The Mackenzie River transports 60% of Canada’s freshwater that drains to the North. Another name for the Mackenzie River is ‘Deh Cho,’ which means ‘Great River’ in the Dene language.

People first settled the Mackenzie River valley more than 5,000 years ago. It has always been important to the Dene and Inuvialuit First Nations of the Present-day Deh Cho, Tlicho, Sahtu, Gwich’in and Inuvialuit Land Claim areas. The Mackenzie-Great Bear sub-basin has an approximate population of 7,800 people, and includes thirteen communities. Inuvik with a population of 2,900 is the largest. Nearly 70% of the residents are Aboriginal.

The western and northern portions of the Mackenzie-Great Bear sub-basin are underlain by a vast reserve of oil and gas that was first commercially exploited at Norman Wells. Vast reserves of petroleum were discovered in the Mackenzie Delta-Beaufort Sea area in the 1970s. The sub-basin holds 15% of Canada’s natural gas reserves. A consortium, consisting of oil companies and a First Nation corporation, is currently advocating development of the Mackenzie Valley Pipeline.

Barges operate each summer between Hay River on Great Slave Lake and Inuvik in the Mackenzie Delta. They serve communities and exploration camps along the Mackenzie River.

Uranium became the mine’s most important product during World War II. The US government used the uranium to test and build atomic bombs. Eventually, six uranium, silver, and base metal mines operated along the eastern shores of Great Bear Lake. Little was known at the time of the lethal and chronic effects of even minor exposure to uranium. There is now concern that such exposure may have harmed the health of people who lived and worked near the mines and along the transport route.

There is no evidence that water quality has deteriorated in the Mackenzie and Great Bear rivers over the past four decades. Turbidity and metal concentrations are naturally elevated in the Mackenzie River and have likely been so for thousands of years. The plants and animals that live in that river have evolved mechanisms over the centuries that enable them to tolerate the high turbidity and metal concentrations.

There are relatively few point sources of pollution on the Mackenzie River compared to other rivers in Canada. Moreover, existing regulations, wastewater treatment systems, and monitoring efforts are adequate to ensure that point sources do not harm water quality.

Aboriginal residents of the Mackenzie Delta have raised concerns about low water levels and the associated effects on their lifestyles. Additional information would be useful in determining whether these changes are due to natural annual fluctuations of if they indicate long-term trends over time.

Flow in the Mackenzie River and its tributaries naturally fluctuates from season to season and from year to year. However, monitoring programs have not found any measurable changes in river flow over time. These monitoring programs will be important in detecting any future changes to river flow due to climate change. A better understanding of how regional climatic conditions influence flow in rivers of the Mackenzie-Great Bear sub-basin is needed.

Ferries and ice bridges are important to the ground transportation network in the sub-basin. Ferry and ice bridge services continue to operate efficiently despite a recent warming trend. Climate is one of the important determinants of how long these operations remain open each year. Climate change may make the season lengths of these operations less predictable in the future.

The population of the Mackenzie-Great Bear sub-basin is very small and there is only one major industry. The demand for water relative to its supply is negligible; clean water is very plentiful.

Subsistence, sport, and commercial fishing are important activities, both culturally and economically. Fish are especially abundant in the Mackenzie Delta. Great Bear Lake is the site of a world-class trophy lake trout fishery. Assessment of key fish stocks are the basis for management strategies, the aim of which is to ensure the sustainable harvest of fish stocks. The involvement of key stakeholders in fish management bodes well for conservation efforts.

Traditional knowledge has raised concerns about the populations or health of some wildlife species such as Dolly Varden, beaver, and muskrat. Other species such as swans, and others may have increased in numbers. Much of the traditional knowledge of aquatic species and habitat is based on information collected before 1997. It would be useful to update this information in order to determine whether the health, abundance, and diversity of aquatic species and habitats have changed since then.

There are intensive efforts by American and Canadian government agencies to monitor changes in population sizes of species of waterfowl in the Northwest Territories. Government agencies in Canada and the United States, together with Duck Unlimited, implement programs intended to conserve waterfowl populations. Populations of some species in the Northwest Territories have declined while others have increased. The causes of these changes are not known.

Floods are a natural occurrence on the Mackenzie River and its tributaries and can be caused by ice jams or intense rainstorms. An intense rainstorm in the southern and western NWT caused a flood in the Mackenzie-Great Bear sub-basin in July 1988, that destroyed or damaged a significant portion of the transportation infrastructure in the upper Mackenzie River and became the benchmark for designing roads and bridges in the region. Although people were unprepared for the 1988 flood, knowledge and infrastructure have improved greatly since then. Nevertheless, further work is required it accurately predict or evaluate trends in the timing and magnitude of flooding in the sub-basin.

The existence of fish consumption advisories for lakes in the Mackenzie-Great Bear sub-basin is a cause for concern. Mercury is naturally elevated in some areas, so the presence of this contaminant may not be due to human activities. Additional monitoring at more lakes is required to determine whether further advisories are required.