An impending water crisis in Canada's western prairie provinces

Abstract

Canada is usually considered to be a country with abundant freshwater, but in its western prairie provinces (WPP), an area 1/5 the size of Europe, freshwater is scarce. European settlement of the WPP did not begin until the late 19th and early 20th centuries. Fortuitously, the period since European settlement appears to have been the wettest century of the past two millennia. The frequent, long periods of drought that characterized earlier centuries of the past two millennia were largely absent in the 20th century. Here, we show that climate warming and human modifications to catchments have already significantly reduced the flows of major rivers of the WPP during the summer months, when human demand and in-stream flow needs are greatest. We predict that in the near future climate warming, via its effects on glaciers, snowpacks, and evaporation, will combine with cyclic drought and rapidly increasing human activity in the WPP to cause a crisis in water quantity and quality with far-reaching implications.

Fig. 1.

The WPP and their major rivers. The sites where long-term temperature and precipitation measurements were analyzed are shown.

Fig. 2.

Long-term relative change in summer flow (May–August) in major rivers of the WPP. (a) The Athabasca River downstream of Fort McMurray, Alberta (−19.8% from 1958–2003; −33.3% since 1970; P < 0.05). (b) Represented by the black line is the Peace River at the town of Peace River, Alberta (−42.1% from 1915–2003; P < 0.0001), and represented by the gray line is the Oldman River at Lethbridge, Alberta (−57.1% from 1912–2003; P < 0.0005). (c) The South Saskatchewan River at Saskatoon, Saskatchewan (−83.6% from 1912–2003; P < 0.0001). The smooth lines are regressions representing the best fit to the data for the entire period. The percentage reduction in flow is the change in regressed flow during the period of record.

Fig. 3.

Temperature increases (°C) predicted by 10 regional general circulation models (mean ΔT = +6.5°C increase from 1961–1990 average; CGCM-2A, Canadian Institute for Climate Studies Project, University of Victoria). The heavy line is a regression of all model data. Points and vertical lines are means and standard deviations among all 10 WPP regional centroids.

Fig. 4.

Historical (a, 1897) and recent (b, 2002) photographs of the Bow Glacier, one of the major sources of the Bow River. The photograph in a was taken by John Norman Collie, Professor of Chemistry at University College London (London). [Reproduced with permission from the Whyte Museum of the Canadian Rockies, Banff, AB, Canada, where its call number is V14/AC-OP/772 (Copyright 1999, Whyte Museum of the Canadian Rockies.] The photograph in b is by Graeme Pole. [Reproduced with permission from Mountain Vision Publishing, Banff, AB, Canada (Copyright 2003, Mountain Vision Publishing).]