An instantaneous profile method for determining the hydraulic conductivity of unsaturated porous materials

The hydraulic conductivity‐water content relationship, as used in the differential equation describing unsteady flow in unsaturated porous materials, is determined from measurements obtained during the drainage of an initially saturated sand column. The approach utilizes instantaneous profiles of the macroscopic flow velocity, the potential gradient, and the water content. The derived relationship exhibits a direct proportionality between the instantaneous velocity and the corresponding potential gradient, thus lending strong support to the contention that Darcy's Law is applicable to flow in unsaturated porous materials of the size range considered in this study.