Tracking Shallow Aquifer Storage Variability Using Time-Lapse Microgravity Measurements in an Arid Environment: Evidence from Al-Ain, UAE

Understanding groundwater dynamics in arid environments is challenging due to sparse monitoring networks and strong anthropogenic influences. This study explores the potential of time-lapse microgravity observations to characterize shallow aquifer storage variability in Al-Ain City, United Arab Emirates. Repeated microgravity measurements were conducted at four monitoring wells over a one-year period between 2018 and 2019, alongside continuous groundwater-level observations, to investigate temporal changes in subsurface water mass. Observed gravity variations exhibit pronounced spatial and temporal contrasts across the study area, reflecting heterogeneity in aquifer response. Groundwater-level fluctuations over the monitoring period indicate notable seasonal and inter-annual variability, which is consistently mirrored in the gravity signal. By jointly analyzing gravity anomalies and water-level changes, variations in groundwater storage were quantified under a range of plausible specific yield values representative of shallow arid aquifers. Estimated storage changes indicate substantial redistribution of groundwater mass over the monitoring period, with corresponding volumetric changes on the order of several tenths to more than one million cubic meters, depending on local aquifer properties. The results demonstrate that microgravity monitoring provides an independent and spatially sensitive means of assessing groundwater storage dynamics, particularly in settings where conventional piezometric coverage is limited. This approach offers valuable insights into aquifer behavior under arid climatic conditions and highlights the broader potential of gravity-based methods for groundwater assessment, resource management, and hydrological characterization in data-scarce regions.