A flux-controlled steady-state evaporation method for determining unsaturated hydraulic conductivity at low matric pressure head values

摘要

We present a simple method for measuring unsaturated hydraulic conductivities at low matric pressure head under a drying process. This method determines hydraulic conductivities from a water content profile under a steady-state upward flow. A steady state was induced by setting both constant meteorological conditions and a constant inflow rate from the bottom. Under our experimental conditions, steady states were attained within a week for two disturbed soils (a loamy sand and a loam). Isothermal water vapor flux was taken into account in the data analysis. Measured hydraulic conductivities agreed well with those obtained from an instantaneous profile method. The simulated time evolution of the evaporation amounts and final water content profiles using the hydraulic conductivity function determined with the present method were also in good agreement with measured values. These results confirm the reliability and applicability of the present method.