The São Francisco River Basin (SFRB) is a vital hydrological system in Brazil, providing essential water resources for human consumption, agriculture, and hydroelectric power. However, the region is highly susceptible to climate variability, experiencing recurrent droughts and substantial fluctuations in water storage. This study examines the relationship between Vertical Crustal Deformation (VCD) and hydrological processes in the SFRB from 2014 to 2024 by integrating GNSS-derived VCD, GRACE-based Terrestrial Water Storage Anomalies (TWSA), and in situ hydrological measurements. Our findings reveal a strong anti-correlation between VCD and TWSA, with correlation coefficients ranging from \( -0.4 \) to \( -0.8 \) , and indicating that variations in water mass directly influence the elastic response of the lithosphere. The analysis identifies two main phases of crustal deformation: (i) a period of uplift from 2014 to 2017, associated with substantial water loss during an extreme drought, and (ii) progressive subsidence from 2017 to 2024, coinciding with the gradual recovery of water storage. The Middle São Francisco region exhibited the most pronounced deformation trends, aligning with significant groundwater level fluctuations and the presence of large reservoirs. The Sobradinho Reservoir appears to play a crucial role in stabilizing crustal deformation within its vicinity, potentially mitigating seasonal hydrological loading effects. Furthermore, correlation analysis between precipitation and groundwater levels showed moderate to strong relationships, with time lags ranging from 1 to 3 months. Notably, the MGBH station, located over a fractured aquifer, exhibited a significantly higher correlation (0.8) compared to sites over porous aquifers. Additionally, the correlation between VCD/TWSA and ENSO was found to be low, suggesting that large-scale climate variability has a limited direct impact on the observed hydrological and deformation patterns in the SFRB. This study underscores the potential of geodetic techniques for water resource monitoring, demonstrating that crustal deformation can serve as a reliable indicator of water redistribution in large river basins. The integration of GNSS, GRACE, and hydrological data provides a robust framework for enhancing water management strategies and improving climate adaptation efforts in high vulnerable regions.
