Soil moisture redistribution and infiltration in frozen sandy soils

Infiltration into frozen soil is a result of the whole climate dynamics of the preceding winter with all its importance for the freezing of the soil. Therefore a predictive infiltration model needs to include a proper descrip tion of the main processes of soil water and heat transfer during season-lo ng periods. Such a model may assume two water-conducting flow domains. A ly simeter experiment was set up with the aim of studying these processes in t wo different sandy soils. Frequent measurements of total and liquid soil wa ter content, soil temperature, and groundwater level were made during two w inters with contrasting meteorological conditions. The main problems in the simulation of the two winters were (1) frost-induced upward water redistri bution, (2) rate of infiltration in the initially air-filled pores, and (3) heat transfer caused by snowmelt refreezing in the frozen soil. An extensi ve calibration of the model suggested that some key empirical parameters we re not constant for the two soils and the two seasons. Complementary method s for determining the hydraulic conductivity of frozen unsaturated field so ils are necessary to further improve the model.