Integrating hydrogeological and earth observation data for the assessment of aquifers compaction and storage dynamics under groundwater abstraction

Rising rates of groundwater abstraction and associated aquifer depletion are a major global concern, threatening environmental integrity, water availability, and food security for future generations. Overexploitation reduces pore water pressure, increasing effective stress in aquifers. The extracted water coming from the compression of adjacent and intervening clay beds results in aquifer compaction and land subsidence, one of the most severe geotechnical consequences of groundwater withdrawal. This issue is prevalent in densely populated and developed areas, often located in unconsolidated Quaternary basins of alluvial, lacustrine, or shallow marine origin. Despite extensive research on land subsidence from groundwater overexploitation, the combined effects of intensified drought and anthropic pressure on aquifer deformation are still unclear. In Italy, land subsidence due to groundwater abstraction is observed particularly in agricultural areas. Increasing demand for irrigation and uncertain surface water supplies exacerbated by climate change, suggests the issue will persist.

Satellite Earth Observation data can enhance understanding of groundwater dynamics: phenological metrics from time series of biophysical parameters and vegetation indices can be used for crop mapping and irrigation needs, while differential SAR interferometry offers accurate quantitative measurements of surface deformation and land subsidence at high spatial and temporal resolution, serving as a proxy for evaluating groundwater abstraction effects. An ongoing research is here presented, with the aim to investigate the physical mechanism beneath the land subsidence, to identify key hydrologic and geotechnical principles driving land subsidence in target areas, in order to develop a predictive framework to estimate the irreversible volume loss of economically extractable groundwater.  The workflow comprises a preliminary phase involving data collection and storage in a dedicated WebGIS platform, followed by the assessment of geological setting, a land use analysis, the analysis of dinSAR data and the trend analysis of groundwater head and withdrawals. The study was approached in two areas (Po Plain and Pontine Plain, Italy), sensibly differing among each other for both the density of available head and withdrawal data and the geological setting, to preliminary assess the relationship between land subsidence and groundwater withdrawal. The perspective of this research is to provide a scientific basis for authorities to plan effective mitigation and ensure sustainable groundwater management.