Strong groundwater extraction has led to subsidence of some areas in many cities of the world, and this phenomenon has been becoming more and more serious in recent 30 years in China. Ground subsidence at the rate of few centimetres per year can be measured using methods of precise leveling, and more recently the GPS. Recent advances in the SAR interferometry, especially with the Permanent Scatterer InSAR (PS InSAR) is an appropriate remote sensing technique for measuring ground subsidence in urban areas at high accuracy and lowcosts. In this work two time-series of 29 JERS and 41 ENVISATASAR acquisitions of Suzhou-Wuxi Jiangsu Province, covering the period from October 1992 to October 2008 (JERS 1992–1998, ASAR 2004–2008), were analyzed. We validate the results by comparing subsidence measurements collected in some points of this area with precise leveling, which are in agreement with each other (relative error within 3 mm/a for JERS). The maps of ground subsidence velocity in Suzhou-Wuxi areas is also obtained with JERS and ASAR images respectively, in which several subsidence centers are discovered. In addition, by comparing the results of PS InSAR with the history of groundwater exploitation, it indicates that ground subsidence in Suzhou-Wuxi areas is induced by groundwater over-extracted.
Groundwater over-pumping has led to serious ground subsidence in many cities of the world, and this phenomenon has been becoming more and more serious in recent 30 years in China. Rapid increase of groundwater use started since 1980's when Suzhou-Wuxi areas were urbanized, people and the industries used groundwater as the main water resource. The more groundwater use the more ground subsidence will happen and ground deformation at the rate of few centimetres per year can be measured at the heavy groundwater pumping stations.