WATER IN CANADA: RESOURCES AND ISSUES

THIS ARTICLE CONSIDERS CANADIAN water resource issues. It is written from a UK perspective but has necessarily drawn on the work of North American authors. On occasions, when there are few current researchers working on some aspects discussed, we have drawn heavily from these results and in addition to the direct referencing of material, we wish to acknowledge the significance of the source material. This article considers the status of water resources in Canada together with the associated threats and issues to the effective management of the resource. Despite being defined internationally as a water-rich country, climatic, topographic and demographic diversity ensures that most water-related issues and problems are encountered in at least some of Canada's territories and provinces. Included in this article is an introduction to Canada's freshwater resource and water uses that exert a demand on that resource together with a summary of the water management structure. The hazards associated with water in Canada will then be discussed, those being flooding, drought and water quality. Finally two key exemplars of issues affecting the resource will be highlighted, those being the threat of exotic species and water transfers. The resource Canada has approximately 20 per cent of the total freshwater in the world and 9 per cent of the world's total freshwater runoff or water supply (Goodman and Thompson 2002) - the difference in these two figures relating to the exceptional water storage in Canada's Lakes. This water is located in a country covering almost 10 million km2 or 7.9 per cent of the land surface of the world (Gleick 2000). Although Canada has apparently a generous supply of freshwater, it is not evenly distributed throughout the country nor is it available throughout the year as significant parts of the theoretical resource are only seasonally available being frozen for part of the year. As a result of Canada's diverse climatic zones, some parts of the country, such as the semi-arid Prairies, experience prolonged periods of drought (at the time of writing, in January 2003, very severe [pers. comm. Alberta farmers]) while others, such as Canada's east and west coasts, are moderated by maritime influences and have a plentiful supply of water year round. Canada's annual precipitation ranges from 50mm in the far north to as much as 4000mm in the temperate rain forest regions of the Pacific Coast (Environment Canada 2002a). The diversity of Canada's hydrology is a reflection of its biophysical complexity but the diversity of its water resource management is, in addition, a reflection of its demographic and settlement diversity. Some of the wettest parts of Canada are found in the mountainous Montane and Boreal Cordillera and Pacific Maritime ecozones covering British Columbia, southwestern Alberta and much of the Yukon Territory. The annual precipitation exceeds 3000mm along the Pacific Coast, and the steep terrain and relatively shallow soils can in some areas, shed almost 90 per cent of precipitation as runoff to the Pacific (Woo 2001). Many of the valleys in British Columbia are underlain by gravel aquifers that are valuable reservoirs for groundwater. Some 12 per cent of all the water used in British Columbia is groundwater derived (Martin et al. 2000). In contrast, the annual precipitation of the semi-arid Prairies varies between 300 to 500mm (Woo 2001). Runoff on the Plains averages well under 200mm per year, especially in the south where it can average less than 50mm, the majority is lost to evaporation (Environment Canada 2002a). The sources of most of the major rivers in the Prairies, such as the Saskatchewan, are located in the Rockies. Their streamflow is supplied by the extended melt of the mountain snowpack, and runoff is sustained through the summer and autumn by glacial melting. These rivers are supplemented by a few small rivers draining prairie land, which are subject to large fluctuations ranging from none to ten times the average (Martin et al. …

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