Determination of unsaturated hydraulic conductivity at low pressure head from a water content profile under steady-state evaporation

摘要

Unsaturated hydraulic conductivity(K(#theta#)) of disturbed sandy loam at low pressure head was determined in a steady evaporation experiment which uses a soil column under constant meteorological condition and a constant pressure head at the lower boundary. Two procedures, "water content gradient method(WGM)" and "inverse method", were proposed to calculate K(#theta#) using steady water content profile obtained from sampling. Water vapor flux is taken into account in both methods. Steady-state was established about 24 hours after beginning of evaporation under our experimental condition. Unsteady simulation of water flow and evaporation rate for the experiment from the beginning of the evaporation till steady state was carried out using K(#theta#) obtained from the experiment. Simulated evaporation and inflow rates from the bottom agreed well with the observed values, indicating reliability of the K(#theta#) values. Numerical experiments were performed for a sand, a sandy loam, and a loam to evaluate a criterion of judgement of steady state and proper pressure head at the bottom.