MODELLING ALPINE SNOW HYDROLOGY IN THE CANADIAN ROCKY MOUNTAINS

directed to advance the understanding of snow processes and to improve hydrometeorological models of snowpack, streamflow and related atmospheric variables. Modelling studies of blowing snow over alpine terrain are showing promise in the prediction of the spatial distributions of snow water equivalent in complex environments. The model includes a complex terrain wind flow algorithm coupled to a two-phase flow snow transport and sublimation algorithm. It calculates snow accumulation as a residual of the snow redistribution and sublimation processes. An important new feature is the application of the model to aggregated landscape units (Hydrological Response Units or HRU) having common physiographic and aerodynamic characteristics; these landscape units require much less physiographic information than do fully spatially distributed blowing snow models and are suitable to application in remote alpine regions with sparse data. Comparisons of model outputs to snow surveys suggest that this level of spatial resolution and physically based simulation can produce reliable snow accumulation estimates in Canadian Rocky Mountain alpine catchments. Snow ablation studies have focussed on application of the energy balance to estimate snowmelt over landscape units with consideration of sub-unit depletion of snow covered area. In this case hydrological response units are segregated based on snow accumulation characteristics and applied melt energy fluxes. The calculated melt rates agree well with observations snow surveys. Improved algorithms resulting from this application of field technology are being used to update a modular, object-oriented computer simulation of the cold regions hydrological cycle, the Cold Regions Hydrological Model, CRHM. CRHM can be easily and frequently updated as improved algorithms become available and used to predict both snow dynamics and streamflow from high mountain areas. (Keywords: blowing snow, snowmelt, snow covered area depletion, hydrological modelling