Boundary and initial conditions
As is illustrated in Fig. 1, the top of the model is the ground surface, so the upper boundary of the model is set with constant pressure (1.0 bar). The lateral boundaries are regarded as non-flow since they are vertical and hence parallel to the flow direction of the infiltrated water in vadose zone, which is well known to be predominately vertical. The initial water table is located at the depth of 2 m in our simulations, since the actual water tables in the test site were observed to be mostly in the range of 1.6~2.3 m below the surface (Wang, 2013). The lower boundary is defined as a non-flow boundary, allowing for elevation in the phreatic surface in case percolation occurs from the unsaturated zone.
To simulate a fairly dry condition, the initialSW is set to be 0.2 for all the model grid cells for C0. The temperature is simply taken to be 23 °C throughout the model domain and isothermal processes are modeled for all the cases. The initial pore pressure is set as 0.91 bar.