Abstract
The Karapinar basin, located in the Central Anatolian part of Turkey, is subjected to land subsidence and sinkhole activity due to extensive groundwater withdrawal that began in the early 2000s. In this study, we use Interferometric Synthetic Aperture Radar (InSAR), Global Navigation Satellite System (GNSS), and groundwater level data to monitor and better understand the relations between groundwater extraction, land subsidence, and sinkhole formation in the Karapinar basin. The main observations used in the study are InSAR-derived subsidence velocity maps calculated from both Sentinel-1 (2014–2018) and COSMO-SkyMed (2016–2017) SAR data. Our analysis reveals broad areas of subsidence with rates exceeding 70 mm/yr. The InSAR-derived subsidence was compared with GNSS data acquired by a continuously operating GNSS station located in the study area, which show a similar rate of subsidence. The temporal characteristic of both InSAR and GNSS time series indicate a long-term subsidence signal superimposed by seasonal variability, which follows the overall groundwater level changes, with over 80% cross-correlation consistency. Our results also indicate that sinkhole activity is limited to slow subsidence areas, reflecting strong cohesion of near-surface rock layers that resist subsidence but yield to collapse in response to aquifer system deformation induced by groundwater extraction.
Highlights
The main reason for the increasing occurrence of non-tectonic geological hazards is anthropogenic usage of water resources due to rapid increase of the world population and the corresponding need to accommodate and meet daily needs [1,2]
The slightly higher rate measured by COSMO-SkyMed detected deformation between February 2016 and September 2017, whereas the slightly slower rate measured by Sentinel-1 detected subsidence during a longer period of 2014–2018
We adopted multi-sensor and multi-temporal Interferometric Synthetic Aperture Radar (InSAR) observations combined with Global Navigation Satellite System (GNSS) and groundwater level records to investigate land subsidence and its relations to sinkhole activity and groundwater depletion in the Karapınar basin, Turkey
Summary
The main reason for the increasing occurrence of non-tectonic geological hazards (subsidence and sinkholes) is anthropogenic usage of water resources due to rapid increase of the world population and the corresponding need to accommodate and meet daily needs [1,2]. Increased land subsidence and sinkhole occurrence, which previously were not perceived as a threat in areas of low population density, limited agricultural activities, and restricted industrial areas, have posed a greater danger and risk to human life [5]. Sinkholes can cause severe financial losses, especially in built environments, and may result in human loss. Monitoring the spatial and temporal distribution of land subsidence and the sinkhole activity is needed for disaster prevention and sustainable development of agriculture and urban areas
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