Time‐Varying Gravity Constraints on Groundwater Recharge and Managed Aquifer Strategies in Southern Taiwan

Abstract Understanding groundwater recharge pathways is essential for designing effective managed aquifer strategies, yet in heterogeneous alluvial aquifers, these pathways are often uncertain and difficult to resolve with sparse well networks. We apply gravity as an independent constraint to quantify groundwater storage dynamics and evaluate recharge strategies in the Ailiao River basin of southern Taiwan. Seven super‐hybrid gravity surveys, integrating absolute, relative, and superconducting gravimeters, were conducted between November 2023 and July 2025 under contrasting hydrological conditions. The surveys revealed distinct seasonal and spatial variability, with recharge driven primarily by rainfall and locally enhanced by river infiltration during wet periods. Stations within 1 km of the river recorded gravity increases up to 100 μGal, while sites beyond 3 km showed minimal (<10 μGal) or delayed responses, delineating a recharge front that attenuates with distance. Comparisons with groundwater levels demonstrated that thick unsaturated zones filter and delay recharge, complicating direct estimation of specific yield. In‐channel modifications provided localized, short‐term recharge but were constrained by unsaturated sediments, whereas stations near proposed recharge‐lake sites recorded stronger and more sustained wet‐season gains, suggesting that recharge lakes offer greater potential for long‐term aquifer replenishment. The super‐hybrid framework maintained referencing continuity despite instrument downtime and typhoon‐related damage, achieving precisions of 3–8 μGal. Beyond operational robustness, our results underscore the value of gravimetry as a non‐invasive complement to well monitoring, capable of constraining recharge fronts, aquifer heterogeneity, and the performance of managed aquifer strategies. These findings provide practical guidance for groundwater management in Taiwan and other alluvial plains worldwide.