Numerical Analysis of Water Movement in Agricultural Fields with Heterogeneous Unsaturated Soils

The natural variability exhibited by soil hydraulic properties poses severe challenges to model water movement through porous formations in agricultural fields. In this study, a 3D numerical approach coupled with the turning bands method to generate realizations of soil formation properties with different heterogeneity levels to solve the governing partial differential equation in variably saturated soils was used to simulate field scale water flow to investigate the impact of soil heterogeneity and root water uptake on subsurface flow dynamics in cropped fields. Soil moisture, suction head and hydraulic conductivity were observed to be significantly affected by heterogeneity of the media and root water uptake. Soil heterogeneity was found to increase soil water content while root water uptake was decreasing it. The effect of root water uptake on soil moisture distribution was more pronounced under homogenous soils than in heterogeneous soils. Soil suction head decreases with increasing soil heterogeneity whether root water uptake was considered or not. Hydraulic conductivity increases with increasing soil heterogeneity when root water uptake was ignored, and it depends on the heterogeneity level when root water uptake was accounted.