Transition Between Constitutive Equations and the Mechanics of Water Flow in Unsaturated Soil: Numerical Simulations

Abstract

Richards’ partial differential equation normally governs water flows in soil. It can be utilized to investigate water infiltration in the soil. A case study of the Haverkamp’s water infiltration simulation into Yolo Light Clay was carried out. A common practice to change between the hydraulic functions (from Haverkamp to van Genuchten) could cause a discrepancy in the simulation results. Hence, the first objective is to modify van Genuchten’s equations to reproduce the water infiltration result that was obtained using the Haverkamp constitutive functions. The method used was able to recreate water infiltration by increasing the fitting parameters of the van Genuchten constitutive functions. The second objective is to identify the mechanism governing the flow of water. The soil water diffusivity and the hydraulic conductivity were responsible for the flux of water in the soil. The Richards’ equation was discretized using a finite difference method, and the algebraic solution was coded into Simply Fortran 2008.