Long-term spatiotemporal evolution of land subsidence in konya metropolitan area (Turkey) based on multisensor sar data

We have studied the spatiotemporal evolution of surface deformation in Konya city and its vicinity using advanced multitemporal synthetic aperture radar techniques with SAR data acquired by Envisat, ALOS-1, and Sentinel-1 A/B satellites between 2004 and 2020. Velocity maps and time series show that the city has been subsiding with varying rates in space and time since 2004. The pattern of deformation shows two main lobes of subsidence centered in the western and eastern sides of the city with a nondeforming north-south trending narrow zone in between. Subsidence rate increases from a few cm/yr to 11 cm/yr between 2014 and 2019. As of 2019, subsidence has slowed down dramatically, giving rise to uplift in some places. Spatiotemporal variation of subsidence and its strong correlation with change in water table level confirm the inferences that subsidence in the metropolitan area of Konya is due to over drafting of the ground water for urban needs. The decrease in subsidence rate over the last two years appears to be due to the city’s residents supplying their water from recently built dams instead of aquifers beneath the city. Initial excessive groundwater extraction in agricultural areas caused ~4 m drops every year in the water table level, which, in turn, gave rise to 8 cm subsidence every year. Modeling of the subsidence shows 7.7 x 10⁶ m³/yr volume loss due to compaction of the aquifer in the Konya metropolitan area and its vicinity between 2014 and 2018.