ESTIMATION OF SNOWMELT RUNOFF IN THE PEACE RIVER REGION USING A SOIL-MOISTURE BUDGET

Rainfall and snowmelt runoff on soil frozen below the surface are reco gnized as important factors contributing to soil loss in Canada. The r isk of rain on frozen soil has been quantified, and the amount of snow melt on frozen soil has been estimated. This study extends such resear ch to derive a climate-based model to estimate winter and spring runof f. This could result in a more accurate erosion prediction for areas w here snowmelt is a major source for runoff. Selected components of the Water Erosion Prediction Project (WEPP) model and the versatile soil moisture budget (VB) were tested on observed data for two study sites in the Peace River region. The version of the WEPP model available to us estimated snow depth, soil frost depth and frequency of freeze-thaw cycles. However, the results did not adequately match observed data. The VB was modified in this study to improve the estimate of potential winter and spring runoff, and it was shown that incorporating observa tions of snow depth improved the estimate of the time and amount of sn owmelt runoff. The modified runoff model was validated with data colle cted in the Peace River area of northern Alberta and British Columbia and with published data from the Prairies.