Analytical Method for Estimating Soil Hydraulic Parameters from Horizontal Absorption

Soil hydraulic properties are required to quantitatively simulate water and chemical transport processes in the vadose zone and groundwater with various numerical models. Most methods for determination of soil hydraulic properties are time consuming and expensive, which limits the application of the methods. The objective of this study was to develop an analytical method based on an assumption of exponential flux distribution to determine soil hydraulic parameters. Using this method, parameters of the Brooks-Corey model and exponential water diffusivity can be easily estimated from cumulative infiltration and wetting length vs. time in horizontal absorption experiments. The analytical method was tested and improved using 19 numerical soils in a wide range of textures. The results indicated that all the Brooks-Corey model parameters estimated by the improved method were very close to the simulated values. In addition, the water content, soil tension, and water flux distributions of three typical soils (clay, loam, and sand soils) estimated by the approximate solution of the improved method agreed well with those calculated by the HYDRUS-1D software as well as cumulative infiltration data. Therefore, although a large number of experiments are still required to test the method, it provides a simple approach to determine the hydraulic parameters of soils in a wide range of textures, providing a very good approximate solution to the problem of horizontal absorption.