Reframing Managed Aquifer Recharge for Conjunctive Flood-Groundwater Resilience

Groundwater depletion and Flooding are increasingly co-located problems: flood risks rise with more frequent and intense rainfall extremes, while underlying aquifers decline due to persistent abstraction. Managed Aquifer Recharge (MAR) offers a pathway to improve groundwater sustainability, yet site selection is commonly guided by recharge volume and subsurface feasibility, with limited quantification of how recharge operations influence surface inundation during flood events. This separation constrains conjunctive strategies that can simultaneously relieve flood impacts and support aquifer recovery. 

This study explores a conjunctive planning approach that redesigns MAR from a basin-centric focus on recharge maximisation to an inundation-centric focus on minimising flood impact. We employ the integrated MIKE SHE modeling system to simulate rainfall-runoff, overland flow routing, unsaturated-zone processes, and groundwater flow in a single dynamical representation. The proposed framework systematically searches where recharge structures could be placed to intercept floodwater and reduce overall flood damages in high-impact locations, while remaining consistent with hydrogeological feasibility and operational constraints. Historical flood events are used as scenario datasets for representative Indian basins, allowing event-based stress testing of candidate locations under realistic forcing.

The simulations show that MAR benefits are highly site- and event-dependent: some locations yield meaningful reductions in local inundation while contributing to groundwater replenishment, whereas others primarily increase subsurface storage with limited flood response. Strategically identified recharge zones produce measurable reductions in peak flood depths in localized high-risk areas, while simultaneously yielding substantial increases in groundwater recharge relative to baseline conditions. The findings underscore the value of reframing MAR to evaluate recharge interventions in support of flood resilience and long-term water security.