Prediction of the saturated hydraulic conductivity from Brooks and Corey's water retention parameters.

Prediction of flow through variably saturated porous media requires accurate knowledge of the soil hydraulic properties, namely the water retention function (WRF) and the hydraulic conductivity function (HCF). Unfortunately, direct measurement of the HCF is time-consuming and expensive. In this study we derive a simple closed-form equation that predicts the saturated hydraulic conductivity, Ks from the WRF parameters of Brooks and Corey (1964). This physically based analytical expression uses an empirical tortuosity parameter () and exploits the information embedded in the measured pore-size distribution. Our proposed model is compared against the current state of the art using more than 250 soil samples from the GRIZZLY and HYPRES databases. Results demonstrate that the proposed model provides better predictions of the saturated hydraulic conductivity values with reduced size of the 90 % confidence intervals of about three orders of magnitude.