Large-scale distributed watershed modelling for reservoir operations in cold boreal regions

The macroscale deterministic hydrologic model, SLURP, was modified and tested on two large watersheds in northern Manitoba, the Taylor River watershed (899 km2) and the upper Burntwood River watershed (6959 km2). Calibration and validation of the model on both watersheds between 1985 and 2000 identified a number of model deficiencies and recommendations for improvement. Date-dependent snowmelt rates were replaced with a single constant snowmelt rate, helping to decrease the parameterization of the model. A snowpack temperature deficit model was also incorporated to simulate the effects of snow ripening. These two modifications provided the modelling flexibility needed to control the timing of initial snowmelt and the rate of snowmelt. Annual spring freshet lasts roughly 2 weeks in this region; however, improved model performance was observed well beyond the spring freshet period. These modifications also provided a better representation of the physical processes that delay snowmelt once the air temperature exceeds 0 °C.Key words: frozen ground, boreal forest, hydrological modelling, snow ripening, snowmelt.