Snowmelt contribution to discharge from a large mountainous catchment in subarctic Canada

Abstract Snowmelt is responsible for much of the annual runoff and most of the peak discharges in subarctic mountainous regions. It also provides a significant amount of freshwater inflow to the polar seas, which has implications for Arctic Ocean circulation. Owing to considerable topographic contrasts in large mountainous basins, snow accumulation and melt patterns are highly variable in time and space, but the scarcity of data in these regions prevents the patterns from being discerned. Application of a macro‐scale hydrological model (using reanalysis data from the European Centre for Medium‐Range Weather Forecasts, the National Centers for Environmental Prediction and the North American Regional Reanalysis) offers one suitable approach to estimate the magnitude and timing of snowmelt contribution to discharge from large mountainous catchments. The Liard basin, subarctic Canada, is used as an example and the SLURP (Semi‐distributed Land‐use‐based Runoff Processes) model allows hydrograph simulation for the Liard and its sub‐basins. Three sets of reanalysis temperature and precipitation data provide inputs to assess the sensitivity of model simulation. The spatial patterns of snowmelt, runoff and stream discharge for four water years were simulated. The SLURP model was found to be sensitive to a plausible range of input conditions as depicted by the three sets of reanalysis data. Despite differences in detail among the three sets of simulation results, several generalities emerged. A comparison of simulated snow cover with satellite data confirms that there are altitudinal delays in spring flow generation though latitude has no apparent influence. Runoff lags snowmelt while the catchment integrates flows of its tributaries, yet different combinations of winter snowfall and spring melt rates cause large interannual variations in snowmelt discharge. Streamflow measured and simulated at four stations along the main river permits an evaluation of runoff contribution from various sectors of the basin. The overall pattern of melt runoff generation and the modelling approach used in this investigation are applicable to other large mountainous basins in high latitudes. Copyright © 2006 John Wiley & Sons, Ltd.