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Uncertainty of the impact of climate change on the hydrology of a nordic watershed

Minville, Marie, Brissette, François, Leconte, Robert
Journal of hydrology 2008 v.358 no.1-2 pp. 70-83
watersheds, watershed hydrology, stream flow, hydrologic models, climate models, General Circulation Models, gas emissions, greenhouse gases, climate change, global warming, rain, precipitation, Quebec
The impact of climate change on the hydrology of the Chute-du-Diable watershed (Quebec, Canada) is studied by comparing statistics on current and projected future discharge resulting from a wide range of climate change scenarios. The use of 10 equally weighted climate projections from a combination of 5 general circulation models (GCMs) and 2 greenhouse gas emission scenarios (GHGES) allows for the definition of an uncertainty envelope of future hydrologic variables. GCM data is downscaled using the change factor approach for 30-year time slices centered around years 2020, 2050 and 2080. To estimate natural variability, synthetic time series are then computed for each horizon and for each climate change scenario, using a stochastic weather generator (30 series of 30 years), and are entered into a hydrology model. Future hydrological regimes are then compared to the control period (1961-1990) using the annual and seasonal mean discharge, peak discharge and timing of peak discharge criteria. Results indicate a 1-14°C increase in seasonal temperature and a -9 to +55% change in seasonal precipitation. The largest increases in both temperature and precipitation are observed in the winter and spring seasons. The main hydrologic impact observed is a spring flood appearing 1-5 weeks earlier than usual and a modification of its amplitude from -40 to +25%. Most scenarios suggest increases in the winter, spring and fall discharge, whereas summer is expected to see a decrease in discharge. While there is still a large scatter in projected values, the uncertainty analysis projects a better view of the most probable future hydrologic behaviour of the watershed. Of all sources of uncertainty considered in this study, the largest comes from the choice of a GCM. Accordingly, all impact studies based on results from only one GCM should be interpreted with caution.