Infiltration into a Frozen Heavy Clay Soil

The infiltration of snow melt water on arable land influences both the water storage and the nutrient budget. The infiltration rate during thawing was assumed to depend on the ice content of the soil. Field measurements of soil temperature, water content and infiltration rate were made and used to test a numerical model. Efforts were made to create different ice contents in three plots by adding different amounts of water before freezing as well as during winter. The total water content in spring was not influenced by the pre-freezing addition of water, but slightly increased by water added during the winter. The simulated total water content was constant throughout the winter. The measured infiltration rates were high, at maximum 8 mm/min, and the differences between the plots were small, although lower infiltration rates were found in plots with higher amounts of added water. Simulated infiltration rates never exceeded 0.1 mm/min. The discrepancy was probably due to water flow in the partially unfrozen crack system, which the model was not capable to simulate, and to a time lag in the simulated soil temperature during thawing. Low infiltration rates were probably caused by high ice content in the cracks, originating from the added water. It should be possible to predict the infiltration capacity during thawing using a simple model which treats the crack system, the water content before freezing, and the number and intensity of warm spells during the winter.