Evaluating Long-Term Effectiveness of Managed Aquifer Recharge for Groundwater Recovery and Nitrate Mitigation in an Overexploited Aquifer System

Abstract. Managed aquifer recharge (MAR) has been widely recognized as an effective strategy for groundwater restoration and has been implemented globally. In the North China Plain, over-extraction of groundwater has led to a continuous decline in water levels, forming one of the world's most significant groundwater depressions. Recent riverine MAR operations have shown significant local groundwater recovery, yet the regional-scale hydrological and geochemical impacts of sustained MAR remain insufficiently understood. Most existing studies rely on short-term field monitoring and emphasize localized responses. This study, focusing on Xiong’an depression area, develops a coupled flow and multi-component reactive transport model to evaluate the long-term impacts of MAR on groundwater recovery and the spatiotemporal evolution of water quality. The results indicate that MAR substantially accelerates groundwater recovery and mitigates the regional depression, though the central funnel exhibits a delayed response due to its distance from recharge sources. Nitrate reduction is dominated by dilution effects from recharge water rather than denitrification, with heterogeneity exerting strong control on the spatial pattern but limited influence on overall concentration levels. These findings highlight the dual hydrological and geochemical benefits of sustained MAR and provide quantitative insights for optimizing large-scale recharge strategies in overexploited aquifer systems.