Testing the Pore‐Solid Fractal Model for the Soil Water Retention Function

The soil water retention curve is an important hydraulic function for the study of flow transport processes in unsaturated soils. To accurately describe and interpret the hydraulic property, a general soil water retention function was developed based on the pore‐solid fractal (PSF) model. The objective of this study was to evaluate the general soil water retention function using data of 65 soils and to compare the PSF function with its special cases, that is, three other soil water retention functions. Defined from the parameters of the PSF, an index of β/θ s was used to quantify the relationship between the PSF and the other soil water retention functions. The PSF function fit all the data sets well, whereas the other retention functions only matched the retention data for some soils, ranging from 11 to 72% of the tested soils. Directly fitting these functions with the data sets showed that for 30 to 40% of the tested soils, these functions gave poorer results than the PSF.