Abstract

Knowledge of the dynamic of water in the soil is essential to estimate both the movement of nutrients from the unsaturated to the saturated zone and groundwater contamination. The objective of this study was to compare drained water data from a Gee Passive Capillary Lysimeter (GPCL; Decagon Devices Inc, Pullman, USA) with model simulations in a soil column. Two experiments were set with the GPCL with different sensor settings and initial moisture content. Preliminary evaluation of the measured data was compared with data simulated by a soil-water model (CRITERIA BdP). The first experiment (GPCL1, soil column with disturbed soil and dry soil as initial condition) generated reliable data. The second experiment (GPCL2, soil column with disturbed soil with wet soil as initial condition and different water application rates) showed variations in the moisture content at all depths for an application rate of 5 mm d-1 due to the propagation pressure waves. This result poses warning for the calibration of infiltration models since neither the Darcian flow theory nor the simplified theories, such as the GreenAmpt method, do not include the effects of pressure waves. Monitoring moisture by capacitance sensors (ECH020, Decagon Devices Inc, Pullman, USA) in both experiments determined the soil water storage, and allowed completing the water balance equation by providing information on the variations of the soil water content. Both moisture content and drainage were adequately simulated by water balance model as compared against measured data.