Experimental and numerical study of a transient, two‐dimensional unsaturated‐saturated water table recharge problem

Transient two‐dimensional water flow is studied in relation to the recharge of a water table aquifer. The approach is based on the physics of water transfer in the complete domain defined by both the saturated and unsaturated zones of soil. Experimental data were first obtained in a slab of soil (3 m in length, 2 m in height, and 5 cm in thickness) in which the changes of water content and water pressure occurring in the flow domain were measured throughout an artificial recharge event. These were compared with the predictions of a numerical model based on the continuity of transfer between the unsaturated and saturated zones. The validity of the model is proved by the excellent agreement between simulated and experimental results. Furthermore, comparison with the results obtained by a viscous flow analog reveals the errors associated with the traditional free surface approach, which neglects transfer in the unsaturated zone.