Experimental Evaluation and Numerical Simulation of the Soil Wetting Front in a Double‐Layer Subsurface Irrigation System With a Permeable Polymer Membrane

ABSTRACT Because of water shortages, improving irrigation efficiency is critical, particularly in agriculture. For this purpose, subsurface irrigation is developing as a promising solution. This study estimates the wetting front distribution of a double‐layer system with a permeable polymer membrane via both laboratory data and HYDRUS‐2D numerical simulations. For this purpose, the distribution of moisture in the wetting pattern was measured with 100%, 50% and 25% membrane cover. The experiments were performed on a 50‐cm cubic physical model and a Mariotte bottle for leakage control. The results revealed that the porosity of the membrane increased the wetting width; for example, the membrane with 100% coverage presented the widest wetting front distribution. After 2 h, the moisture levels across different membrane coverages were comparable, although the 100% membrane system achieved the greatest horizontal and vertical spread. Additionally, the model accuracy was validated by comparing the simulated wetting front distribution with the HYDRUS‐2D and experiential distributions, which achieved an NRMSE of approximately 10% for both width and depth estimates. These findings support full membrane coverage as an effective strategy to increase subsurface irrigation efficiency and suggest that HYDRUS‐2D reliably simulates moisture dynamics under various soil and irrigation conditions.