Field simulation of in situ water content and temperature changes due to ground–atmospheric interactions

A site in Boissy-le-Chatel, France, has been instrumented with a meteorological station, piezometers, thermocouples and time domain reflectometry equipment, in order to monitor solar radiation energy, precipitation, runoff, wind speed, air temperature, air humidity, soil temperature, soil volumetric water content, and underground water table levels. Data recorded in April 1999 were used to validate predictions of soil water content changes based on the works of Blight and Wilson et al. In the elaborated approach, Penman's equation is employed to evaluate the potential evapotranspiration, and Darcy and Fick's laws are used to describe the flows of liquid and vapour water respectively. The soil water content and hydraulic conductivity are presumed to be functions of soil suction, and the coefficient of latent heat of vaporisation of water is assumed to be a linear function of temperature. The formula proposed by De Vries is used for calculation of the thermal conductivity coefficient. The results of Wilson et al. for laboratory conditions were used to validate the model used. To simulate field conditions, climatic data were used to calculate the volumetric water content and temperature profiles in the soil, and the calculated values were compared with direct measurements. Satisfactory results were obtained.