Estimating groundwater volume loss using GRACE(FO) and InSAR observations for the subsiding area of Bandung Basin, Indonesia

This study explores satellite-based observations, specifically Gravity Recovery and Climate Experiment and its Follow-On missions, or GRACE(FO), and Interferometric Synthetic Aperture Radar (InSAR) observations to estimate volumetric groundwater loss in Bandung, Indonesia, where profound subsidence is found. GRACE(FO) estimates indicate groundwater loss of $$-$$ 0.10 to $$-$$ 0.16 km $$^3$$ /yr, while GRACE(FO) corrected for possible bias between mission estimates to $$-$$ 0.56 to $$-$$ 0.63 km $$^3$$ /yr. At the same time, InSAR combined with 1D poroelastic modeling estimates $$-$$ 0.592 to $$-$$ 1.38 km $$^3$$ /yr. These methods show a general agreement in declining groundwater trends, though the magnitude varies. GRACE(FO)’s regional-scale sensitivity and potential errors, such as north–south striping and reliance on global hydrological models, affect its accuracy. InSAR’s estimates are influenced by hydrogeological parameters, such as geological assumptions, bulk modulus, and aquifer thickness, highlighting the need for more comprehensive data collection and model refinement. The study further highlights the limitations of current methods and underscores the need for improved hydrogeological surveys, as well as the consideration of both confined and unconfined aquifers in the Bandung Basin. To validate our satellite-based estimates, we compared them with reported groundwater withdrawals from a recent hydro-geomechanical model, which estimated up to 1.1 km $$^3$$ /yr. The upper range of our estimates aligns well with this, supporting their reliability and highlighting ongoing pressure on Bandung’s groundwater resources. Furthermore, the variabilities in available groundwater levels were compared with InSAR-derived subsidence rates, revealing a general consistency between groundwater decline and land subsidence. Finally, future work should incorporate robust hydrological monitoring and independent analyses using physically based hydrological models. Despite data constraints, the study corroborates previous findings of groundwater depletion in Bandung, emphasizing the potential of satellite-based approaches in monitoring and managing subsidence-related groundwater loss.