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<p>Coastal aquifers worldwide are increasingly vulnerable to seawater intrusion driven by intensive groundwater extraction and climate change, posing significant risks to freshwater availability and regional water security. Despite its promise as a climate-adaptive strategy, the efficacy of the managed aquifer recharge (MAR) system under future climate scenarios remains inadequately quantified. This study aims to assess the potential of MAR to mitigate seawater intrusion and reduce groundwater salinity in a coastal aquifer system using a coupled flow and transport model. A three-dimensional transient MODFLOW–SEAWAT framework was developed for the Plana de Castellón aquifer (Spain), an unconfined system covering approximately 65&#xa0;km² and discretized into six layers with a 100&#xa0;m cell size (13,806 active cells). The model was calibrated against observed hydraulic heads and total dissolved solids (TDS), achieving an RMSE of 6.5% for heads (<i>R</i> = 0.97) and 10% for TDS (<i>R</i> = 0.96). The model simulates density-dependent flow, solute transport, and recharge plume dynamics. Multiple MAR configurations were evaluated under baseline conditions and two contrasting climate scenarios (SSP1-2.6 and SSP5-8.5), focusing on trends in total dissolved solids (TDS), the spatial extent of saline intrusion, and recovery timeframes. Results indicate that without MAR, natural salinity attenuation is slow under both climate futures, prolonging freshwater scarcity. In contrast, MAR substantially enhances groundwater quality recovery and limits the inland encroachment of saline water. The best-performing MAR scenario, MAR_3, comprising four strategically located recharge wells, reduced the saline-affected aquifer area by ~ 52% and accelerated TDS decline below 2000&#xa0;mg/L by up to 11 years relative to no-MAR conditions. While climate change influences recovery trajectories, MAR benefits persisted across scenarios, highlighting its role in climate resilience. These findings underscore the importance of integrating MAR into sustainable groundwater management frameworks to safeguard coastal aquifers against climate and anthropogenic pressures. The study provides a transferable modelling approach and decision-support insights for planners and policymakers addressing groundwater sustainability in the face of environmental change.</p> Graphical Abstract <p></p> <p>The graphic abstract illustrates the research workflow, progressing from left to right, with arrows indicating the direction. This study aims to assess the potential of managed aquifer recharge (MAR) systems to mitigate seawater intrusion and enhance recovery of groundwater salinity in a coastal aquifer using a groundwater flow and solute transport model (MODFLOW–SEAWAT). The model was used to simulate an actual MAR and the effects of other MAR systems on the aquifer (i.e., groundwater levels and salinity). The aquifer was modelled until 2050 to evaluate the impacts of climate change. Based on the results, it was possible to model the pilot test and identify which proposed MAR system would achieve groundwater total dissolved solids concentrations below 2000&#xa0;mg/L in the shortest time. If no MAR systems are used and climate change follows the SSP1-2.6 scenario, this goal would be achieved in 2045. Based on this reference scenario, which represents baseline system conditions, alternate MAR systems were modelled with varying numbers of wells and recharge water sources (e.g., runoff and treated wastewater) to achieve the target TDS concentration. For the SSP5-8.5 climate change scenario, the target concentration would be achieved in 2046 without an MAR system and in 2035 with one. This model provides a robust tool to promote sustainable aquifer management and mitigate seawater intrusion under different climate change scenarios by testing control and mitigation solutions based on MAR systems. This modeling approach enables efficient management of recharge systems by facilitating planning and verification of their technical feasibility under different climate conditions.</p>

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Managed Aquifer Recharge as a Climate-Adaptive Strategy to Mitigate Seawater Intrusion: Insights from Coupled Flow and Transport Modelling

  • 期刊论文

  • 发表日期：

    2026年7月6日

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  • Bárbara del R. Almazán-Benítez,
  • María V. Esteller-Alberich,
  • Arianna Renau-Pruñonosa,
  • José L. Expósito-Castillo

摘要

Coastal aquifers worldwide are increasingly vulnerable to seawater intrusion driven by intensive groundwater extraction and climate change, posing significant risks to freshwater availability and regional water security. Despite its promise as a climate-adaptive strategy, the efficacy of the managed aquifer recharge (MAR) system under future climate scenarios remains inadequately quantified. This study aims to assess the potential of MAR to mitigate seawater intrusion and reduce groundwater salinity in a coastal aquifer system using a coupled flow and transport model. A three-dimensional transient MODFLOW–SEAWAT framework was developed for the Plana de Castellón aquifer (Spain), an unconfined system covering approximately 65 km² and discretized into six layers with a 100 m cell size (13,806 active cells). The model was calibrated against observed hydraulic heads and total dissolved solids (TDS), achieving an RMSE of 6.5% for heads (R = 0.97) and 10% for TDS (R = 0.96). The model simulates density-dependent flow, solute transport, and recharge plume dynamics. Multiple MAR configurations were evaluated under baseline conditions and two contrasting climate scenarios (SSP1-2.6 and SSP5-8.5), focusing on trends in total dissolved solids (TDS), the spatial extent of saline intrusion, and recovery timeframes. Results indicate that without MAR, natural salinity attenuation is slow under both climate futures, prolonging freshwater scarcity. In contrast, MAR substantially enhances groundwater quality recovery and limits the inland encroachment of saline water. The best-performing MAR scenario, MAR_3, comprising four strategically located recharge wells, reduced the saline-affected aquifer area by ~ 52% and accelerated TDS decline below 2000 mg/L by up to 11 years relative to no-MAR conditions. While climate change influences recovery trajectories, MAR benefits persisted across scenarios, highlighting its role in climate resilience. These findings underscore the importance of integrating MAR into sustainable groundwater management frameworks to safeguard coastal aquifers against climate and anthropogenic pressures. The study provides a transferable modelling approach and decision-support insights for planners and policymakers addressing groundwater sustainability in the face of environmental change.

Graphical Abstract

The graphic abstract illustrates the research workflow, progressing from left to right, with arrows indicating the direction. This study aims to assess the potential of managed aquifer recharge (MAR) systems to mitigate seawater intrusion and enhance recovery of groundwater salinity in a coastal aquifer using a groundwater flow and solute transport model (MODFLOW–SEAWAT). The model was used to simulate an actual MAR and the effects of other MAR systems on the aquifer (i.e., groundwater levels and salinity). The aquifer was modelled until 2050 to evaluate the impacts of climate change. Based on the results, it was possible to model the pilot test and identify which proposed MAR system would achieve groundwater total dissolved solids concentrations below 2000 mg/L in the shortest time. If no MAR systems are used and climate change follows the SSP1-2.6 scenario, this goal would be achieved in 2045. Based on this reference scenario, which represents baseline system conditions, alternate MAR systems were modelled with varying numbers of wells and recharge water sources (e.g., runoff and treated wastewater) to achieve the target TDS concentration. For the SSP5-8.5 climate change scenario, the target concentration would be achieved in 2046 without an MAR system and in 2035 with one. This model provides a robust tool to promote sustainable aquifer management and mitigate seawater intrusion under different climate change scenarios by testing control and mitigation solutions based on MAR systems. This modeling approach enables efficient management of recharge systems by facilitating planning and verification of their technical feasibility under different climate conditions.