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20th-Century Streamflow in Canada's Winnipeg River Basin
St. George, S. 2007. Streamflow in the Winnipeg River basin, Canada: Trends, extremes and climate linkages. Journal of Hydrology 332: 396-411.

The author says "a substantial body of evidence suggests that river flow in Canada declined significantly during the 20th century," and that "decreasing river flows are a particular concern because Canada is the world's foremost producer of hydroelectric power, accounting for roughly 13% of global output." In addition, he notes that "the Winnipeg River influences the production of over 4600 MW of hydroelectricity, and is the most important component of the hydrological system used to generate power in Manitoba."

What was done
Using daily and monthly streamflow data from the Water Survey of Canada's HYDAT data archive for nine gauge stations that had more than 50 years of record and were still operating at the end of 2003, plus precipitation and temperature data for selected stations within the Winnipeg River region, St. George assessed "how river flow in the Winnipeg River basin has behaved during the last one hundred years."

What was learned
St. George found that streamflow in the Winnipeg River basin increased significantly during the last 80 years, with winter streamflow rising by 60-110%, while mean annual flow rose by 58%. He also found that "changes in annual and winter streamflow are observed in records from both regulated and unregulated portions of the watershed, which point to an underlying cause related to climate." Lastly, he reports that "comparisons with long-term meteorological records suggest that the basin hydrology has served to amplify coincident, but smaller, increases in precipitation during summer and autumn."

What it means
Noting that concerns about decreasing river flows in the Canadian prairies "have been exacerbated by suggestions that a doubling of atmospheric CO2 could increase the severity and frequency of droughts in the region," St. George says the results of his study show that "hydrological trends in the Winnipeg River basin during the 20th century are different from those observed on other Canadian rivers," and that "it seems likely that the potential threats to water supply faced by the Canadian Prairie provinces over the next few decades will not include [our italics] decreasing streamflow in the Winnipeg River basin," which is good news indeed for Canada's hydroelectric power industry.

Reviewed 5 December 2007