Autumn creek (Photo by Karol Dabbs)

Autumn creek (Photo by Karol Dabbs)

Freshwater 101

Vista from Flathead River Ranch, British Columbia (Photo by NCC)

Vista from Flathead River Ranch, British Columbia (Photo by NCC)

"Water. Canada. The words are as inextricably linked in our Canadian culture as maple and syrup, or Stanley and Cup. And despite our reverence for the liquid of life, the evidence is compelling that we are over-using and abusing water, to our collective environmental and economic detriment…’’  ~ David Boyd (2004) in the foreword to The Future in Every Drop.

Classification of freshwater ecosystems

While much is known about Canada’s terrestrial ecosystems, and a well-established land-based classification system exists, surprisingly little is known about aquatic ecosystems. However, just as a coastal western hemlock forest is different from a spruce-willow-birch forest, not all rivers, and all lakes, are alike in their physical habitat, hydrologic regime, water chemistry and temperature, connectivity or biotic interactions.  

The diversity of freshwater organisms across Canada is a testament to the diversity of the river and lake ecosystems that are found across the country. Yet surprisingly, there exists no established freshwater ecosystem classification.

For proper freshwater resource management, it is essential to characterize these river and lake ecosystem types based on their dominant environmental processes, physical habitat and what is known of their biological communities.

Canada's Freshwater Geography Map

Canada's Freshwater Geography Map

Did you know…

  • About 70 per cent of the Earth is covered in water. 
  • The major source of freshwater is evaporation off the surface of the oceans; approximately 505,000 km3/year. 
  • Canada is the country with the third most renewable freshwater, after Brazil and Russia. 
  • If all the Earth's water were stored in a five-litre container, the available freshwater would not quite fill a teaspoon.
  • Annually, Canada's rivers discharge seven per cent of the world's renewable water supply.
  • Almost nine per cent, or 891,163 square kilometres of Canada's total area, is covered by freshwater.
  • The Canadian portion of the Great Lakes occupies nearly 10 per cent of the freshwater area in Canada. 
  • The Great Lakes Basin (shared with the United States) is the world's largest freshwater lake system. 
  • Approximately 60 per cent of Canada's fresh water drains to the north, while 85 per cent of the population lives along the southern border with the United States. 
  • The largest river basin in Canada is the Mackenzie Basin, based on drainage area, discharge and length.
  • There are an estimated two million lakes in Canada, covering approximately eight per cent of Canada's land area — more than any other country in the world.

(source: Environment Canada Freshwater Website, visited March 5, 2008)

An ecosystem at risk

Since 1970, the health of the world’s freshwater ecosystems has declined by 50 per cent.1 More than one-half of the world’s major rivers have been seriously depleted and polluted and over half of all of the world’s wetlands have been eliminated.2 This has resulted in an extinction rate of freshwater biodiversity that is five times faster than all other groups of species.3

Figure1: Per cent of native freshwater-dependent Species at Risk (S1-S3) in BC (Ciruna et al. 2007).

Figure1: Per cent of native freshwater-dependent Species at Risk (S1-S3) in BC (Ciruna et al. 2007).

In British Columbia alone (which contains 25 per cent of Canada’s freshwater supply and 5 per cent of the world’s supply), it is estimated that an astounding number of species that depend on freshwater for their survival are at risk (Figure 1).

Reasons for this deterioration are easily understood - the world’s growing human population uses freshwater for a vast range of services, including electricity, drinking water, waste removal, crop irrigation and landscaping, transportation, manufacturing, fishing, flood control, and recreation. In doing so, freshwater ecosystems are disrupted, starved, contaminated and sometimes completely eliminated.

What is NCC doing to protect freshwater ecosystems?

The Nature Conservancy of Canada (NCC) has been leading the way in the development of ecosystem classifications for rivers and lakes throughout the entire province of British Columbia as well as the Ontario portion of the Great Lakes basin.

  • In 2006, NCC and The Nature Conservancy (TNC) announced the release of the first Binational Conservation Blueprint for the Great Lakes — a plan that reveals areas in critical need of conservation in both Canada and the United States. Developed with leading scientific expertise from within the region, the blueprint provides government agencies, businesses and concerned residents on both sides of the border with a roadmap to preserve the Great Lakes ecosystem. It is the first effort to map and analyze data on the variety of ecosystems and special biodiversity features across the entire Great Lakes basin.
  • In BC, NCC, in partnership with the provincial government, has developed a hierarchical freshwater ecosystem classification for BC, entitled Ecological Aquatic Units of British Columbia4 (EAU BC). The EAU BC classification is an essential component to the freshwater analysis of the Central Interior Ecoregional Assessment currently underway in the BC Region.
  • Four binational Aquatic Conservation Blueprints have also been completed in BC, in the Canadian Rocky Mountains, Okanagan, North Cascades and Coastal Forests and Mountains ecoregions. These Conservation Blueprints highlight priority watersheds for conservation; watersheds being increasingly recognized as the appropriate scale at which to address aquatic species and ecosystems.


  1. Loh, J. 2000. Living Planet Report 2000. UNEP-WCMC. World Wide Fund for Nature, Gland, Switzerland.
  2. Millennium Ecosystem Assessment. 2005. Ecosystems and Human Well-Being: Wetlands and Water Synthesis. World Resources Institute, Washington, DC.
  3. Ricciardi, A. and J.B. Rasmussen. 1999. Extinction Rates of North American Freshwater Fauna. Conservation Biology 13(5): 1220-1222.
  4. Ciruna, K. Butterfield, J.D. McPhail, and BC Ministry of Environment. 2007. EAU BC: Ecological Aquatic Units of British Columbia. Nature Conservancy of Canada, Toronto, Ontario. 200 pp. plus DVD-ROM.

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