Investigation of numerical and analytical solutions of 1D steady and transient flow in unsaturated layered soils

This study presents a comprehensive numerical simulation and analytical modeling of steady and transient flow in heterogeneously saturated soils. Solving the Richards equation involves challenges due to the nonlinearity between the pressure and the water content. Two constitutive models are used to describe the complex relationships between moisture content, hydraulic head, and hydraulic conductivity namely, Gardner model and Van Genuchten-Mualem model. Through detailed simulations, four configurations are investigated, including the capillary barrier effect, bi-layered soil dynamics in paddy fields, and infiltration in multi-layered soil in both saturated and unsaturated steady-state regimes. The comparison between numerical results and the established analytical model shows a good agreement. It underscores the usefulness of the model to reproduce saturated and unsaturated seepage flow in bi-layered and multi-layered soils. Moreover, it captures the dynamic interactions between infiltration and evaporation during the transient phase. These findings offer insights for water resource management, land subsidence mitigation, and environmental sustainability.