Hydrological decoupling of groundwater from natural climatic forcing in a heavily managed megacity

Introduction Groundwater recharge is traditionally understood to be primarily controlled by precipitation and other climatic processes. However, intensive anthropogenic water management and urbanization may weaken this relationship in megacities. This study investigates hydrological decoupling at the municipal scale in Beijing, China, and quantifies the relative contributions of anthropogenic and climatic drivers to groundwater dynamics. Methods We analyzed 19 years of multisource hydroclimatic data using nonparametric trend analyses, antecedent-window correlation analyses, and hierarchical multiple regression. Spatial analyses were conducted to examine the potential effects of impervious surfaces and managed vegetation on natural groundwater recharge. Future drought risks and groundwater trends were also assessed under the SSP2-4.5 and SSP5-8.5 climate scenarios for 2024–2100. Results Annual precipitation showed no statistically significant correlation with groundwater depth (Spearman’s ρ = 0.04, p = 0.624), and no significant delayed associations were identified across antecedent climatic windows of 1–12 months. Hierarchical regression attributed 60.0% of the variance in groundwater depth to anthropogenic drivers, represented by total water supply, compared with 35.6% attributed to natural climatic forcing. Spatial analyses further indicated that dense impervious surfaces and managed vegetation may constrain natural recharge and weaken the influence of meteorological variability on groundwater dynamics. Both future climate scenarios indicated substantial drought risk, while historical evidence suggested that groundwater trajectories would remain strongly influenced by active water management. Discussion The findings indicate that anthropogenic water management can become a dominant control on urban groundwater dynamics, potentially outweighing the influence of climatic variability. This hydrological decoupling challenges conventional assumptions about precipitation-driven groundwater responses and highlights the importance of integrating water governance, urban land-surface characteristics, and climate adaptation into groundwater management strategies for heavily urbanized basins.