Quantifying vertical deformation in the Tigris-Euphrates basin due to the groundwater abstraction: Insights from GRACE and Sentinel-1 satellites

This study explores the occurrences of land subsidence in response to dropping groundwater levels in the central part of the Tigris-Euphrates basin. We estimated the groundwater depletion related to human and climate drivers between 2003 and 2017 based on estimates from the Gravity Recovery and Climate Experiment (GRACE) and two global hydrological models (NOAH-3.3 and WGHM-2.2d). The cumulative displacement was calculated using Small Baseline Subset Interferometric Synthetic Aperture Radar (SBAS-InSAR) for 96 interferograms, which were generated by 31 images acquired by the Sentinel-1 satellite. The results show that the basin is experiencing a decline in groundwater storage at a rate of -7.56 km³/year with a total loss of 106.81 km³. This depletion rate has led to inelastic compaction and has resulted in subsidence near the city of Baghdad at a rate of -10 mm/year. The measured coherence phase between the two signals is ~0.67, and the depletion precedes the subsidence by ~1.5 months. The new data from GRACE-Follow on, Sentinel-1, and the piezometric water level could help to constrain the rate of depletion and displacements in the basin. Combining these remote sensing techniques provides an independent tool for water management in areas where in-situ data are scarce.