Transition and Drivers of Elastic to Inelastic Deformation in the Abarkuh Plain From InSAR Multi-Sensor Time Series and Hydrogeological Data

Tracking the inelastic deformation of an aquifer is important to quantify the stress experienced by the aquifer system, so that the effects of the current extraction practices are put in the context of the hydrogeological settings of a region. However, transition of elastic to inelastic deformation is hard to be monitored, particularly in the Abarkuh Plain (AP) with a dry climate. In this study, we define the confined extent of aquifer system and track the spatial evolution of inelastic deformation based on the multi-sensor Interferometric Synthetic Aperture Radar time series in the AP in central Iran from 2003 to 2020. Our results demonstrate that many locations with experiencing no significant inelastic deformation a few years ago are now deforming inelastically, leading to partially irreversible lowering of ground surface and loss of aquifer storage. Lithological data shows that total thickness of compacted clay units controls the extent and timing of observed inelastic deformation, while joint geodetic-well data confirms that multi-decadal dropping of head in the confined extents of aquifer system is driving the long-term compaction. These results show that we are possibly near a tipping point between the sustainable conditions and permanent damage to underground water resources and the current decisions have the potential to permanently change the natural resources landscape.

Automated summary

Tracking the inelastic deformation of an aquifer is crucial for understanding the stress it experiences and evaluating the impact of extraction practices in a region's hydrogeological setting. However, monitoring the transition from elastic to inelastic deformation is challenging, especially in a dry climate like the Abarkuh Plain (AP). In this study, we used multi-sensor Interferometric Synthetic Aperture Radar data from 2003 to 2020 to define the confined extent of the aquifer system and track the spatial evolution of inelastic deformation in central Iran. Our findings indicate that previously unaffected areas are now experiencing inelastic deformation, resulting in irreversible subsidence and aquifer storage loss. The thickness of compacted clay units and declining water heads within the confined extents of the aquifer system play significant roles in controlling and driving long-term compaction.