Study on the Desalinization Process of Residual Saltwater in Heterogeneous Aquifer Upstream of Subsurface Dam

Widespread use of subsurface dams as an effective control mechanism may lead to residual saltwater in landward directions and limit the exploitation of groundwater. However, most of the current studies neglect the influence of heterogeneity, or are limited to laboratory scale. In this paper, the seawater intrusion process before and after the construction of subsurface dams under different layered heterogeneous conditions was simulated by a site-scale numerical model. The effects of different layered heterogeneous conditions on the desalination process of residual saltwater and groundwater discharge process are discussed by taking the wedge regression rate of residual saltwater, the removal rate of residual total salt and the percentage of groundwater discharge as indexes. The results show that the change of hydraulic conductivity of the lower aquifer has a significant influence on the regression effect of residual saltwater. The larger the value of low permeability layer, the faster the regression rate. However, the thickness of low permeability layer has little influence on the desalination process of residual saltwater.