Two Models to Describe the Entire Soil Water Retention Curve

Two models are proposed to describe the entire soil water retention curve from saturation to zero water content. Each model has only three parameters, thus being simple and easy to apply. The first model takes pF (pF is a logarithm of matric suction measured in cm) and the second model takes the matric suction (h) as the independent variable. The SWRCs fitted by the two models are in good agreement with measured retention data. The fitting results of the SWRCs of the two models for clay soils are better than those for sandy soils. This may be because the pore-size distribution of clay soil is more consistent with the lognormal distribution law than that of sandy soil in this study. Further, the first model is better than the second model for representing the entire SWRC because the first model describes the logarithmal rule of the soil pore-size distribution better than the second model.