Predicting the soil water characteristic curve from the particle size distribution based on a pore space geometry containing slit-shaped spaces

Abstract

Abstract. Traditional models employed to predict the soil water characteristic curve (SWC) from the particle size distribution (PSD) always underestimate the water content in the dry range of the SWC. Using the measured physical 10 parameters of 48 soil samples from the UNSODA unsaturated soil hydraulic property database, these errors were proven to originate from the underestimation of the pore volume fraction of the minimum pore diameter range. A method was therefore proposed to improve the estimation of the water content in the high suction range using a pore model comprising a circle-shaped central pore connected to slit-shaped spaces; in this model, the pore volume fraction of the minimum pore diameter range and the corresponding water content were accordingly increased. The SWCs predicted using the improved 15 method reasonably approximated the measured SWCs, and which were more accurate than those obtained using traditional method in the dry range of the SWC.