Submitted to: Snowmelt Erosion and Related Problems International Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 11/15/2000
Publication Date: 2/1/2001
Citation: Mccool, D.K., Lin, C. 2001. Evaluating and modifying the winter routines in wepp. Snowmelt Erosion and Related Problems International Symposium.
Technical Abstract: Evaluation of WEPP (Water Erosion Prediction Project) of USDA-ARS indicated that the winter subroutines in this model predict longer soil freezing periods and deeper frost depths but less runoff than actually observed in many areas. An energy budget approach was selected and tested for its potential in replacing the current winter subroutines in WEPP. This approach has been used to model snow pack development and snow melting in many studies. It has also been used to predict the occurrence of soil freezing. This project further develops the energy concept to quantify temporal depth variation of soil frost. The concept is based on an energy balance relationship composed of four components, net radiation, latent heat, sensible heat and the heat flow through the soil surface. Hourly and daily calculation schemes for snow accumulation and melt, and frost penetration and thaw, were developed and tested independent of the WEPP model. Both schemes performed adequately, but the hourly version was chosen because of the observed rapid change in soil freezing conditions in the field. Preliminary results of testing the modified WEPP model with observed data from Minnesota and Washington show this approach to be a significant improvement over the current winter routines, although predicted runoff is still less than observed.