How does rewetting propagate through restored peatlands? An integrated surface–subsurface modelling analysis of water–table dynamics

Abstract Peatland restoration, through drainage suppression, is widely implemented to recover hydrological and ecological functions; however, the groundwater system responses governing rewetting efficiency remain insufficiently quantified across spatiotemporal scales. Here, a boreal fen is used as a process-representative system to resolve how restoration interventions, including ditch infilling and damming, reorganise catchment-scale water-table dynamics, drawing on calibrated, fully integrated three-dimensional physics-based modelling (HydroGeoSphere). Simulated restoration elevated domain-scale median water table by ~ 23 cm, with comparable gains (~ 22 cm) in nominally undisturbed areas, revealing that drainage legacy extends well beyond visibly ditched zones. Variogram analysis confirmed a shift from fragmented, drainage-controlled conditions to hydraulically connected systems with increased spatial correlation lengths. Water-table recovery propagated according to distinct hydrogeologic response regimes depending on restoration structure and subsurface properties. Low-permeability peat infillings generated strong localised responses with rapid exponential attenuation of water-table recovery (~ 70% decline within ~ 40 m), whereas dams produced broader, plateau-like responses extending up to ~ 100 m. Geomorphic setting further modulated recovery, with peat thickness and proximity to peat–mineral margins acting as primary controls through a threshold-like response regime. Seasonal hydroclimatic forcing modulated recovery, with wet-season response nearly doubling water-table rise relative to dry subarctic winters. These results demonstrate that drainage suppression reorganises peatland groundwater systems by enhancing lateral connectivity and controlling how hydraulic responses propagate across space. While the absolute magnitudes are site-specific, the identified controls and response patterns provide a mechanistic, transferable basis for guiding restoration in comparable boreal fens.