Modeling Ponded Infiltration in Fine Textured Soils with Coarse Interlayer

To understand the mechanism of infiltration into fine textured soil with a coarse interlayer and to justify the capability of Richards equation-based models, ponded infiltration experiments were conducted in homogenous (loam and three types of sand) and layered soil (loam with sand interlayer) columns. The HYDRUS-1D numerical software based on the Richards equation was used to simulate the above processes where soil hydraulic parameters of the two kinds of soil were calibrated from infiltration experiments in correspondent homogenous soil columns and were used directly to simulate the infiltration process in layered soil columns. Comparison between the model simulations and the experiments shows that the HYDRUS-1D model was able to predict the infiltration rate and wetting front advancement correctly. Simulation results show abrupt variation of the soil water profile along the interface in layered soil columns. It also demonstrates that the matric suction immediately under the interface was the controlling factor for the stable infiltration rate where a coarse interlayer with higher matric suction tended to facilitate infiltration instead of inhibiting it, contrary to the previous research.