Impact of Rainfall Infiltration on Groundwater Seepage under the Effect of Urban Construction in Shanghai

Abstract Groundwater seepage is influenced by various anthropogenic factors during urban construction, among which subsurface structures and surface hardening are two key factors. This study employed numerical simulations to investigate the impacts of rainfall infiltration on groundwater seepage under the effect of urban construction. A numerical model was established to predict groundwater level (GWL) in the phreatic aquifer (Aq0), incorporating the actual distribution of impervious surfaces and subsurface structures for a representative urban area in Shanghai. The model accounted for land surface conditions through rainfall infiltration coefficients, while subsurface structures were parameterized using equivalent hydraulic conductivity ( K eq ) derived from effective medium theory. Validation results show that the model achieved a maximum error of only 1.7%, demonstrating reliable performance in predicting groundwater seepage. There is 23.23% area with GWL declining more than 0.4 m in the actual scenario with 93% impervious surface hardening comparing without surface hardening. Prediction scenarios with varying reduction rates of impervious surface compared with the actual scenario ( R a ) were conducted to investigate the impact of surface hardening on GWL. The results indicate average GWL of the study area presents exponential decay with the impervious surface ratio. Further, the variations in GWL of Aq0 were investigated by reducing hardened surfaces in different locations with the same R a . As the proportion of underground structures in the reduced impervious surface increases, the area with the same increment of GWL decreases. Prioritizing low impact development in areas with lower subsurface structure density can significantly enhance the efficiency of groundwater recharge by rainfall infiltration.