A physically based soil frost depth model usable with air temperature data and precipitation data, is presented. Snow depth is calculated from precipitation data using a physical snow cover model. The soil frost depth model is tested in one small basin, with a five-year calibration and verification period. Results from snow depth and soil frost depth simulation were satisfactory also in the verification period.
In the second stage simulated frost depth information was used to develop an HBV-runoff model version, attempting to simulate the possible effect of soil frost on runoff. The simulation results are presented. These results suggest that soil frost does not have a very important effect on runoff in this forested basin.