IN-SITU METHOD FOR ESTIMATING SUBSURFACE UNSATURATED HYDRAULIC CONDUCTIVITY

A method for the estimation of subsurface unsaturated hydraulic conductivity in situ was developed and field tested. The new method is based on Philip's (1992) approximation of water flow from a small subsurface cavity. Measurements of water pressure within the cavity (P) and associated discharge (Q) are used to infer the soil's saturated hydraulic conductivity (K-s) and capillary length (alpha). A probe for conducting the measurements was designed and field tested, and a measurement protocol was established. Comparisons were made with existing surface-based methods by exposing the soil surface at the depth of the subsurface measurement. The method provided estimates of the soil parameters that were in close agreement with those obtained using surface-based in situ methods.