Managed Aquifer Recharge in Confined Multi-Layer Aquifers: A Scalable Framework for Drought Resilience in Central Europe

Abstract. Managed Aquifer Recharge (MAR), particularly Aquifer Storage, Transfer and Recovery (ASTR), can enhance groundwater resilience in confined multi-layer aquifers under drought stress. We develop an integrated and scalable framework to assess ASTR feasibility by combining (i) meteorological and groundwater drought analysis using the Standardized Precipitation Evapotranspiration Index (SPEI-12) and Standardized Groundwater Index (SGI), (ii) GIS-based multi-criteria decision analysis (MCDA) for recharge site suitability, and (iii) dynamic assessment of surface-water availability using ecological flow thresholds. Applied to the water-stressed Berlin-Brandenburg region, one of Germany’s driest areas, where water supply relies heavily on induced bank filtration and faces emerging deficits. Results show that groundwater levels closely follow climatic conditions, indicating that climate-based drought indices can guide timely ASTR operations. The MCDA identified 62.5 % of the area (2,154 km²) as viable for ASTR. Flow-threshold analysis at 27 gauges showed that high-potential downstream sites could provide mean annual recharge volumes of 1.6–4.3 Mm³, offsetting 6–79 % of local extractions. At the catchment scale, total mean annual available recharge is 18.2–23.0 Mm³. Literature-based cost estimates (€0.37–0.51 m^-³) are substantially lower than regional drinking-water production costs (€1.80 m^-³), suggesting potential annual savings of €23–41 million.