Improved characterization of frozen soil processes in the Versatile Soil Moisture Budget model

Abstract

Mohammed, G. A., Hayashi, M., Farrow, C. R. and Takano, Y. 2013. Improved characterization of frozen soil processes in the Versatile Soil Moisture Budget model. Can. J. Soil Sci. 93: 511–531. Soil freezing and thawing influence the infiltration of rain and snow melt water and subsequent redistribution, runoff generation, and a host of other processes. Accurate characterization of frozen soil processes in hydrological models is important for their use in managing agricultural activities and water resources. The Versatile Soil Moisture Budget (VSMB) is a relatively simple soil water balance model, which has been widely used in Canada for several decades, but its application has primarily been for crop-growing seasons. We have modified the VSMB to include new algorithms for snow accumulation and melt, soil freezing and thawing, and snowmelt infiltration and runoff; and evaluated its performance using field data from a grassland site in Alberta. The new VSMB model simulates snow processes with reasonable accuracy and predicts the day of thawing within several days of observation. It also estimates the amount of runoff and its inter-annual variability reasonably well, although the model still has limitations in accurately predicting the vertical distribution of water content. Despite these limitations, the model will be useful for estimating the amount of snowmelt runoff that provides the critical water inputs to wetlands and dugouts, and for understanding the effects of landuse variability on these processes.