Dams in Canada

There are over 15,000 dams in Canada of which 933 are categorised as “large” dams under the ICOLD definition. These dams are owned by the federal and provincial governments, electric utilities, industrial and mining companies, irrigation districts, municipalities and private individuals.

Some of the largest dams in the world are associated with Canadian hydroelectric and mine tailings developments. Other dam structures in Canada include small and medium embankments for agricultural and water supply usage. In all cases the dams must be designed, operated and maintained so that they do not pose an unacceptable risk to the downstream populations.

The great majority of large dams in Canada were built as components of large hydroelectric projects. With its great wealth of rivers and hydraulic resources, it is no wonder that Canada is now the world’s biggest producer of hydro power, generating 350 TWh/year. That output represents 62 percent of the country’s total electricity production, and more than 13 percent of the global output of hydro power. This electricity is produced from 450 hydroelectric stations and more than 200 small hydro plants (less than 10 MW). Over the years, Canada has developed a world-renowned expertise in hydropower and in dam projects design, construction and management.

Canada is a country rich in water resources, and it is not surprising that only a small number of the large dams in the country have been built strictly for irrigation, water supply or flood control purposes. Hundreds of small dams, however, have been constructed for individual water supply or irrigation purposes. Most of the dams in Canada are multi-purpose, to a degree, and many hydroelectric dams can claim some degree of water supply or flood control benefits.

Irrigation and the construction of dams to support irrigation has developed in primarily Western Canada due to a wealth of suitable land for irrigation, a lack of available moisture during the growing season, and the availability of runoff water due to snow melt. Consequently, the most significant irrigation dams are located in southern Alberta, the B.C. interior and on the Saskatchewan River system. Smaller developments have been constructed in Saskatchewan and Manitoba to capture local snowmelt runoff not directly connected to the mountains.

Water supply dams are used to provide water for urban and rural domestic water supply, recreation, navigation, industry, waste assimilation, and cooling for thermal power plants. Large dams developed strictly for the supply of water are not that common in Canada due to the general abundance of water resources in most regions. In many regions, however, smaller dams have been constructed to serve a variety of water supply needs. Many other dams, developed primarily for hydro-electricity, irrigation, or flood control have secondary water supply benefits.

Flood control measures in Canada include dams, dykes or levees, and flood ways. Several regions of Canada are prone to flooding, due in large part, to the abundance of water resources and the extremes in seasonal temperatures. Rapid snowmelt is the chief cause of flooding, but rainfall can often increase the effects of snowmelt runoff. Some regions, especially the western prairies, can experience violent summer rainstorms that result in severe local flooding. In Canada, the areas most susceptible to flooding are also the areas first settled and farmed. Topography of the river systems is also a significant factor in the potential flooding. Many rivers in British Columbia occupy steep V-shape valleys and the rivers have relatively steep gradients which can lead to rapid increases in river flows due to rapid snow melt. In the prairie region, most rivers and creeks are underfit systems in large glacial outflow channels. Once the channel capacity is exceeded, widespread flooding can occur because of the surrounding low flat terrain.

For more information about dams in Canada, the 2003 Dams in Canada database isavailable from the Executive Director, executive.director@cda.ca.