ABSTRACT: Quantification of historical and projected trends in freshwater availability in the Canadian Prairie region.

CGRG Bibliography of Canadian Geomorphology
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Abstract

Recent studies have suggested decreases in both the climate water balance (precipitation - evapotranspiration) and low flows in the Canadian Prairie provinces. Generally, numerical models based on relatively simple formulations for actual evapotranspiration (or even simply potential evapotranspiration) have been applied to determine trends in the climate water balance which are then used to project low flows assuming baseflow drops accordingly. We present work using a coupled carbon-water-energy cycle model, EALCO, parameterzied using detailed remote sensing inputs to test the hypothesis that climate water availability is decreasing in the prairies and that it will continue to decrease under climate change scenarios. Our findings suggest that there is little current evidence in support of the hypothesis that water availability is decreasing substantially over the prairies, with the possible exception of decreased glacier melt input. Essentially, the prairies are already water limited so increasing temperatures have not increased actual evaporation significantly. Our findngs are also supported by water budget analysis of trends over selected Prairie basins. Significantly we also find that, when forcing the model with IPCC AR4 GCM model scenarios, any potential trends in ET due to future climate changes are substantially smaller in magnitude that the differences induced by using different GCM model runs for a given scenario. This suggests that projections of future low flow regimes need to carefully factor in the uncertainty in our ability to quantify climate trends under warming scenarios.

Bibliography of Canadian Geomorphology