TEMPERATURE-VARIATIONS EFFECT ON FIELD-MEASURED INFILTRATION

The infiltration rate varied during a 24-h period, with a maximum of approximately 1700 h and a minimum of about 0700 h every day. Variations in infiltration rate approached ± 30% of the mean rate (14.5-26.9 mm/h) and followed the variations of temperature at the soil surface. Temperatures at the water-soil interface varied from 14.9 to 31.5°C, with a maximum change during a 24-h period of 15.7°C. A conceptual model proposed a hydraulically restricting surface layer, overlying an unsaturated subsoil of greater permeability. Changes in the hydraulic conductivity of the surface layer, reflecting changes in the water viscosity in response to diurnal temperature changes, caused the infiltration rate to vary throughout the day. A numerical model was constructed and used to demonstrate that the conceptual model could explain most of the observed behavior at this site. -from Author