Estimating relative hydraulic conductivity from lognormally distributed particle-size data

We present a simple model to estimate relative hydraulic conductivity (RHC) of unsaturated soils directly from lognormally distributed particle-size data. It is based on the model that estimates the water retention characteristic (WRC) from lognormally distributed particle-size data. The proposed model allows us to estimate the RHC from the particle-size distribution (PSD) data alone, providing a physically based link among the PSD, the WRC, and the RHC. We tested the proposed model against different soil types and found, for soils with a strong lognormal PSD or for well-graded soils, that its performance is generally similar to that of the traditional Mualem-based models that estimate the RHC from the WRC.