Modeling CO2 migration in a site-specific shallow subsurface under complex hydrodynamics

•CO2 migration in complex shallow subsurface groundwater is analyzed by parameter study.•Leakage rate is a dominant factor that determines the spatial pattern of CO2 plume.•A large groundwater velocity may completely inhibit the upward migration of CO2 and transport it laterally so that the leakage to the surface will not occur.•Rainfall and pumping wells give the groundwater flow field regional characteristics, well location and extraction have a strong influence on the fate of CO2 plume.