Numerical simulation of coupling surface water and groundwater based on GSFLOW for the Jinghu Wetland

Surface runoff in wetland includes various forms such as open channel flow and sheet flow, and wetland exists the spongy soil layer. Therefore, it is difficult to carry out coupling simulation of wetland surface water and groundwater. In view of the shortcomings of the coupling numerical simulation of the current wetland surface water and groundwater, researches are conducted to solve the problem of accurate simulation of wetland sheet flow and sponge layer. The Shaoxing Jinghu National Urban Wetland Park is taken as the research object, and the unique sponge layer formed by the growth and deposition of wetland plants for many years is considered. A coupling numerical model for surface water and groundwater in wetland is constructed based on the GSFLOW model. The wetland sheet flow is simulated by the 2D diffusion equation and the wetland open channel flow is simulated by the 1D Saint Venant equation. The coefficient of permeability of the wetland spongy layer is measured by using the straight standpipes. The model parameters are calibrated and the model simulation results are verified by using the monitoring data of the hydrological station in the simulation area. The calibrated model was used to simulate the interaction process of wetland surface water and groundwater, and the water balance analysis is carried out in the study area. The results show that the coupling model of wetland surface water and groundwater considering the wetland sponge layer can reflect the hydrological characteristics of wetlands more realistically. The groundwater in wetland is mainly recharged from surface water, and the recharge varies with rainfall. The coupling model of wetland surface water and groundwater established in this paper is reasonable and reliable, and is of important application value for wetland hydrological analysis.