This research uses weather radar to approximate the accumulation of snow over the winter season as input to hydrologic watershed modelling for estimation of hydrographs. The hydrologic modelling is accomplished using a coupling of WATFLOOD, a distributed hydrologic model developed at the University of Waterloo, and CLASS, the Canadian Land Surface Scheme developed by Environment Canada. Both models use the Grouped Response Unit or mosaic approach, that considers land cover heterogeneity within computational units. Two important components of the winter hydrologic budget are redistribution and sublimation of snow. In some areas, a large portion of the snow being redistributed is lost to the vapour phase during the suspension of particles, whereas in other areas most of the sublimation occurs directly from the snow cover.

The objectives of this paper are to simulate the spring hydrograph for four central southern Ontario watersheds using continuous modelling and to assess the importance of sublimation in southern Ontario. The total simulated volume of runoff is very close to the observed volume, and the simulated hydrographs match the peaks of the observed streamflow well. The second objective was achieved through modelling of the snowpack and field measurement of the snowpack over the winter season. Along with traditional meteorological and snowpack measurements, a class A evaporation pan mounted on a load cell was used to continuously measure the mass changes in the snowpack. The measurements compare well with the computed sublimation, illustrating an average sublimation loss for southern Ontario of approximately 15% of the total snow accumulation.