Respond to urban floods and groundwater depletion: A managed aquifer recharge approach to alleviate urban water challenges.

Climate change, rapid urbanization and increasing impervious surfaces influence urban flooding and groundwater depletion in developing cities, leading to chronic water scarcity and posing a severe threat to urban water security. These challenges can be addressed through integrated water management strategies that enhance infiltration and aquifer recharge. This study evaluates the application of Aquifer Storage Transfer and Recovery (ASTR) as a Managed Aquifer Recharge (MAR) approach by repurposing 23 abandoned wells to inject stormwater during peak rainfall events. A 5-year, 6-h design storm, along with 14 years of historical data (2009-2023), including groundwater levels, well discharge, rainfall, and evaporation, was used to evaluate the performance of the ASTR system through SWMM and MODFLOW models. The results indicate that the ASTR system can reduce flood volume by up to 5% during a single storm event, and the water table rises by 0.5 m to 12 m over 14 years of historical stress periods on groundwater, depending on the availability of flow and soil conditions at the abandoned well locations. Additionally, the annual groundwater recharge potential is estimated to be up to 1 million m3yearfor Chattogram, Bangladesh. The study highlights the dual benefits of MAR through ASTR: mitigating urban flooding while replenishing aquifers. It demonstrates that abandoned wells can be effectively repurposed for sustainable stormwater management, offering a cost-effective and scalable solution for water-scarce, flood-prone urban environments. This study emphasizes the importance of integrating surface and subsurface hydrologic models in urban planning to improve climate resilience and ensure long-term water security.