Figure 2. Generalized schematic diagram of the simulation area

The actual area on which this quasi-ideal model relies is the plain area of the Baiyangdian Basin in the North China Plain, wetland degradation refers to the degradation of the Baiyangdian wetland, and the lake set up is Baiyangdian Lake. The aquifer in this study area is a phreatic aquifer, which is divided into one layer in the vertical direction with a thickness of 60 m. In this model, precipitation infiltration recharge is the main source of groundwater recharge in the North China Plain. The coefficient of precipitation infiltration recharge α is approximately 0.17–0.35, which is taken as 0.2; the lateral recharge in the study area is 25% of the rainfall infiltration recharge. The average depth of Baiyangdian Lake is 3.5 m, the elevation of the lake surface is 10.5 m, and the elevation of the lake bottom is 7 m. The water-bearing medium is a sand layer, the hydraulic conductivity is set as 25 m/d, the specific yield μ=0.20, and the bottom of the phreatic aquifer is a clay layer, taken as the confining bed.

According to the above hydrogeological conceptual model, the groundwater flow in the study area is generalized to a homogeneous isotropic submerged two-dimensional transient flow model, and the corresponding mathematical model is as follows: