Surface response and subsurface features during the restriction of groundwater exploitation in Suzhou (China) inferred from decadal SAR interferometry

Abstract

Groundwater overexploitation has caused dramatic land subsidence over the metropolitan areas in the Yangtze River Delta (YRD) and many other economic centers worldwide. Suzhou (China) is such a sinking city and faces enhanced flood risks. Restrictions on groundwater exploitation (RGE) have been imposed by the government since 1997 to prevent further elevation loss. However, knowledge on the spatiotemporal evolution of the urban land deformation during the RGE is limited by sparse and infrequent field measurements, which may bias the evaluation of the RGE policy and the strategy formulation of water management. Interferometric synthetic aperture radar (InSAR) provides regional surface deformation at a regular temporal interval of dozens of days. Here we present the decadal evolution of ground deformation in Suzhou using multiple InSAR datasets from ERS1/2, ENVISAT-ASAR, and ALOS-1 PALSAR-1 during 1993–2010, spanning the entire RGE period. An elongated zone from southern to northwestern Suzhou is highlighted by a drastic cumulative land subsidence exceeding 0.9 m due to inelastic aquifer compaction. We characterize the spatiotemporal ground deformation response to the RGE policy using an exponential decay function, from which we also infer the subsurface boundaries with sharp bedrock gradients. We identify a corridor connecting the Yangcheng and Taihu lakes, which is highly sensitive to RGE during the decelerated subsidence. Our analysis also suggests that urban subsidence in Suzhou was under control by 2006−0.4+1.4.