Land elevation change from subsidence to uplift due to groundwater decline and rebound in Taiyuan City, Northern China, analyzed with a long-term measurement from leveling and multi-sensor InSAR

In recent years, a comprehensive groundwater management program was adopted in Taiyuan City, Northern China, to prevent the lowering of groundwater levels and manage land subsidence due to excessive groundwater pumping in the past decades. Groundwater level from drawdown to rebound has been observed in this city following the termination of groundwater pumping. While the link between land subsidence and groundwater pumping is well documented, how the land surface responds to the recovery of groundwater after the cessation of pumping has not been studied in detail. Our study is therefore to examine the spatial and temporal evolution of land surface elevation in response to the historical groundwater drawdown and the recent groundwater recovery in more detail.We analyzed the leveling data from 1956 to 2000 to investigate changes in ground elevation in response to groundwater depletion before the termination of groundwater pumping and combined them with InSAR (Interferometric Synthetic Aperture Radar) displacement data from 2003 to 2020 to evaluate the effect of groundwater recharge after the termination of groundwater pumping. A method was proposed to merge the InSAR time series of displacement derived from multiple satellites (ENVISAT, COSMO-SkyMed, TerraSAR-X, and Sentinel-1) to achieve a consistent, long-term continuous deformation. Previous groundwater depression cones in Taiyuan (Xizhang, Wanbailin, Wujiabao, and Xiayuan) have turned into groundwater recovery and the corresponding subsidence centers have switched to land uplift. The subsidence center of Xizhang, north of Taiyuan City, experienced a total subsidence of 749 mm by Aug 2003; it then turned into an uplift with an amount rebound of 9.2% of previous subsidence by the end of 2020. In the central area of Taiyuan, the cumulated subsidence is 1127 mm in Wanbailin, 1817 mm in Xiayuan, and 3343 mm in Wujiabao. Beginning in Aug 2010, they all turned into land uplift, with a rebound of 7.9%, 4.8%, and 3.6% of the previous subsidence in each center, respectively. An analysis of the correlation between groundwater level and ground displacement suggests that the ground uplift is related to the poroelastic rebound mechanism in the porous aquifer system, which is caused by the rise in pore pressure with groundwater recovery, and the stratigraphic properties control the amount of subsidence/uplift. The findings improve our understanding of anthropogenic land subsidence and uplift in complex urban aquifers influenced by groundwater depletion and recharge and provide essential information that can contribute to future groundwater management and groundwater-related hazard mitigation in Taiyuan City.