Thermal, Moisture, and Solute Transport Responses Effects on Unsaturated Soil Hydraulic Parameters Estimation

This paper studies the estimation of unsaturated soil parameters based on thermal, moisture, and solute characteristics, which are important factors that affect productivity and the environment. The objective of this investigation was to determine optimal hydraulic parameters in unsaturated soil. The soil thermal, moisture, and solute transport processes are approached using one-dimensional isothermal models characterized with nonlinear permeability effects, sorption, and reaction that generally cause considerable experimental and numerical difficulties. The spectral element method is presented for space discretization while the time scheme is constructed along the fully implicit approach with the modified Picard iterative procedure. The iterative Levenberg-Marquardt optimization algorithm is adopted for the inverse process. The reliability and performance of the studied model is conducted using refinement indicators based on error, residual, and variance analyses, which allow drawing more representative uncertainty of model parameters estimation. Good agreement with the nonlinear optimization of soil hydraulic parameters estimated and true values is obtained. The estimated responses from respective shape curves show relatively small variability. A consideration of ionic diffusional and average temperature effects was revealed, indicating that the change of one of these factors might not necessarily improve parameter identification responses. For soil moisture content ranges between 0.04 and 0.5 cm³ cm^-3, average temperature input from 20 to 40 ° C as well as when the ionic molecular diffusion coefficient is greater than 10 cm² hr^-1, a rough representation of moisture, thermal, and hydrochemical characteristics might be sufficient to estimate soil hydraulic parameters.