In this study, a 2D finite-element analysis, using the SEEP/W program, was carried out to estimate the amount of groundwater flowing into a tunnel, as well as the groundwater tables around wetland areas during and after tunnel excavation through rock mass. Four sites along the Wonhyo-tunnel in Cheonseong Mountain (Gyeongsangnam-do, Korea) were analysed, where the model domain of the tunnel included both wetland and fault zones. The anisotropy of the hydraulic conductivities of the rock mass was calculated using the DFN model, which was then used as an input parameter into the continuum model. Parametric studies were performed on the influencing factors to minimize uncertainties in the hydraulic properties. Moreover, the volumetric water content and hydraulic conductivity functions were applied to the model to reflect the ability of a medium to store and transport water under both saturated and unsaturated conditions.