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The hydrological sensitivity of a northern Canadian mountain basin to change in temperature and precipitation was examined. A physically based hydrological model was created and included important snow and frozen soil infiltration processes. The model was discretized into hydrological response units in order to simulate snow accumulation and melt regimes and basin discharge. Model parameters were drawn from scientific studies in the basin except for calibration of routing and drainage. The model was able to simulate snow surveys and discharge measurements with very good accuracy. The forcing inputs of the hourly air temperatures and daily precipitation were scaled linearly to examine the model sensitivity to conditions included in a range of climate change scenarios: warming of up to 5 °C and change in precipitation of +/− 20%. The results show that peak seasonal snow accumulation, snow season length, evapotranspiration, runoff, peak runoff, and the timing of peak runoff have a pronounced sensitivity to both warming and precipitation change, where the impact of warming is partly compensated for by increased precipitation and dramatically enhanced by decreased precipitation. The snow regime, including peak snow accumulation, snow-free period, intercepted snow sublimation, and blowing snow transport, was most sensitive to temperature, and the impact of a warming of 5 °C could not be compensated for by a precipitation increase of 20%. However, basin discharge was more sensitive to precipitation, and the impact of warming could be compensated for by a slight increase in precipitation. The impacts of 5 °C warming with a +/−20% change in precipitation resulted in snow accumulation, runoff, and peak streamflow decreasing by from one half to one fifth and the snow-free period lengthening by from 46 to 60 days; in both cases, the smaller change is associated with increased precipitation and the larger change with decreased precipitation. These results show that mountain hydrology in Northern Canada is extremely sensitive to warming, that snow regime is more sensitive to warming than streamflow and that changes in precipitation can partly modulate this response. Copyright © 2014 John Wiley & Sons, Ltd.

Yukon air temperature trends have been observed to change over the last several decades with an increase in annual, summer and winter air temperatures, while changes in precipitation have not been consistent. An assessment of freeze-up and break-up dates indicates that the ice cover season is becoming shorter with delays in freeze-up and advances in break-up timing. Mid-winter break-up events and associated flooding have been observed for the first time. Break-up water level trends suggest that break-up severity is increasing. These changes cannot be definitely attributed to climate change as there is some evidence suggesting that teleconnections may be a factor. The observed changes have significant implications pertaining to public safety, and economic impacts on property and infrastructure, transportation networks and hydroelectric operations. Ice jams and associated backwater and surges also affect aquatic ecosystems through impacts on biological and chemical processes.