Simulation of snowmelt runoff pathways on the Lac Laflamme watershed

The contributions of subsurface and surface runoff to streamflow during snowmelt in a balsam fir forest located on a laurentidian upland watershed (Lac Laflamme) of Québec (47°N, 71°W) were determined with a hydrological model (HYFOR). Lysimeter and calculated snowmelt runoff at the base of the snowpack were used as an input to the model during the snowmelt periods of 1985, 1986, and 1987. The calculated values were obtained from a temperature index snow cover model. The initial simulations showed a poor ability to predict runoff. The soil porosity and hydraulic conductivity were modified to account for the ground frost effect. Simulations were substantially improved by reducing soil porosities by 31% and hydraulic conductivities by 53% of their original values measured under the frost free conditions. Surface flow volume, which lumps rapid through-flow and overland flow, computed with the calibrated model varied between 32 and 47% of the total volume for the three snowmelt periods. Because of the significant modifications of soil parameters necessary to obtain reasonable model performance, it is concluded that better field observations on soil hydrologic properties are needed to improve snowmelt runoff simulations.