Background
The author notes that the study of Burn (1994) suggested that a doubling of the air's CO2 content could increase the severity and frequency of droughts in the prairie provinces of Canada (Alberta, Saskatchewan, Manitoba), but that results from an ensemble of climate models suggest that runoff in the Winnipeg River region of southern Manitoba, as well as runoff in central and northern Manitoba, could increase 20-30% by the middle of the 21st century (Milly et al., 2005). So what has actually been happening in this regard in this part of the world? Has it been getting drier or wetter?

What was done
St. George obtained daily and monthly streamflow data from nine gauge stations within the Winnipeg River watershed from the Water Survey of Canada's HYDAT data archive, plus precipitation and temperature data from Environment Canada's Adjusted Historical Canadian Climate Data archive, and analyzed them for trends over the period 1924-2003.

What was learned
It was determined, in the words of the author, that "mean annual flows have increased by 58% since 1924 ... with winter streamflow going up by 60-110%," primarily because of "increases in precipitation during summer and autumn." In addition, he notes that similar "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." Countering these positive findings, however, St. George says there are "reports of declining flow for many rivers in the adjacent Canadian prairies," citing the studies of Westmacott and Burn (1997), Yulianti and Burn (1998), Dery and Wood (2005) and Rood et al. (2005).

What it means
Just as there are conflicting predictions about the future water status of portions of the Prairie Provinces of Canada, especially in Manitoba, so too are there conflicting reports about past streamflow trends in this region. Hence, it's anybody's guess as to what will actually occur in the years and decades ahead, although based on the observed trends he discovered, St. George believes "the potential threats to water supply faced by the Canadian Prairie Provinces over the next few decades will not include decreasing streamflow in the Winnipeg River basin."

References
Burn, D.H. 1994. Hydrologic effects of climate change in western Canada. Journal of Hydrology 160: 53-70.

Dery, S.J. and Wood, E.F. 2005. Decreasing river discharge in northern Canada. Geophysical Research Letters 32: 10.1029/2005GL022845.

Milly, P.C.D., Dunne, K.A. and Vecchia, A.V. 2005. Global patterns of trends in streamflow and water availability in a changing climate. Nature 438: 347-350.

Rood, S.B., Samuelson, G.M., Weber, J.K. and Wywrot, K.A. 2005. Twentieth-century decline in streamflows from the hydrological apex of North America. Journal of Hydrology 306: 215-233.

Westmacott, J.R. and Burn, D.H. 1997. Climate change effects on the hydrologic regime within the Churchill-Nelson River Basin. Journal of Hydrology 202: 263-279.

Yulianti, J. and Burn, D.H. 1998. Investigating links between climatic warming and low streamflow in the Prairies region of Canada. Canadian Water Resources Journal 23: 45-60.