Infiltration and Unsaturated Flow under the Influence of Surface Microtopography: Model Simulations and Experimental Observations

Abstract

Surface microtopography affects fundamental hydrologic processes including infiltration and soil-water percolation at different scales. By means of studying the unsaturated flow, this thesis research is aimed to evaluate the effects of surface microtopography on wetting front moving patterns for rough soil surfaces through both experimental study and HYDRUS modeling. Additional influential factors such as rainfall intensity and soil type are also considered. Laboratory-scale infiltration and unsaturated flow experiments were conducted for different microtopographic surfaces, rainfall intensities, and types of soil; and two- and three-dimensional numerical modeling was conducted under the same conditions. The simulated and observed wetting front distributions were compared in this combined experimental and modeling study. It was found that a uniformly distributed wetting front was eventually achieved although soil surfaces had dissimilar topographic characteristics. However, the timing to reach the uniform flat wetting front varied, depending on surface microtopography, soil hydraulic properties, and boundary conditions.