Spatiotemporal Groundwater Responses to Peatland Restoration: A Fully Integrated Surface–Subsurface Modelling Study on a Boreal Fen

Peatland restoration, through drainage suppression, is widely implemented to recover ecological function, yet the driving hydrological mechanisms controlling groundwater responses across spatial and temporal scales remain poorly quantified. Here, we use calibrated, fully integrated 3D physics-based modeling to explicitly resolve how rewetting interventions, including ditch infilling and damming, restructure catchment-scale groundwater dynamics across a boreal fen. Simulated restoration actions elevated water tables by ~23 cm, with comparable gains in nominally undisturbed areas, demonstrating far-field impacts of drainage legacy and the re-establishment of lateral hydrological connectivity. Variogram analysis revealed that hundreds of meters of previously fragmented, drainage-controlled peatlands were transformed into hydraulically coherent systems, enhancing spatial correlation and damping extreme drawdowns. Additionally, findings revealed that lateral propagation of groundwater recovery depended on structure type and hydraulic properties, with low-permeability peat infillings produced strong local responses with steep exponential decay (~70% within ~40 m), whereas dams generated broader plateauing effects (~100 m radius). Geomorphic context further modulated outcomes, where groundwater recovery also followed exponential growth away from peat–mineral margins, with intermediate-thickness peatlands defining a tipping-point regime that maximizes recovery magnitude and variability. Seasonal dynamics amplified restoration efficiency, with wet periods nearly doubling groundwater rise relative to dry winters, yet elevated efficiency persisted during dry intervals between spring melts and autumn rains. Collectively, these findings reveal how restoration effects propagate laterally, interact with seasonal hydroclimatic forcing, and are shaped by geomorphic context, providing a transferable, mechanistic framework for prioritizing and designing restoration plans that maximize peatland hydrological recovery.