Permanent aquifer storage loss from long-term groundwater withdrawal: a case study of subsidence in Bandung (Indonesia)

Study Region: In this study, the focus is on the Bandung groundwater basin in Indonesia, where industrial groundwater exploitation has led to declining groundwater levels and consequent land subsidence. Study Focus: A highly parameterized three-dimensional hydro-geomechanical model was developed for the Bandung groundwater basin. The region faces challenges due to scarce hydrogeological data, necessitating the use of satellite-based Interferometric Synthetic Aperture Radar (InSAR) techniques to supplement the parameterization of numerical groundwater models. By calibrating the model against InSAR-derived land displacement measurements, the study addressed the lack of detailed historical pumping data and estimated past groundwater extraction volumes. The model was also used to forecast future subsidence and evaluate aquifer storage changes until 2050 under various pumping scenarios. Our study is one of the first examples of using satellite data with geomechanical models to constrain groundwater extraction rates and emphasises the importance of remote sensing data in groundwater resource management, and the irreversible impact of unsustainable groundwater extraction, which has implications for long term water security. New Hydrological Insights for the Region: The study found that continued industrial groundwater extraction has resulted in permanent aquifer storage loss, with significant implications for longterm water security. Our simulated subsidence rates peaked at 16.4 cm/yr over the 1950–2020 period, with a maximum cumulative subsidence of 6.9 m. Continued industrial groundwater extraction, primarily from the deeper, confined aquifer, has resulted in permanent aquifer storage loss totalling 7.2 km3. Our model projections indicate that subsidence will persist, with continued industrial extraction potentially leading to up to 5.6 m of additional subsidence and 11.1 km3 of aquifer storage loss by 2050. Reducing industrial groundwater use by 30 % could slightly reduce further subsidence (5.0 m) and aquifer storage loss (9.2 km3) by 2050.