Land subsidence due to deep groundwater withdrawal in northern yangtze river delta area

Abstract

Long term excessive deep groundwater withdrawal from third confined aquifer (CA3) has led to progressive drawdown of groundwater in the Northern Yangtze River Delta area. The CA3 is the main aquifer of groundwater pumping and utilization in the research area due to its abundant groundwater and good quality. Several cones of depression have formed with the maximum groundwater level depth of 47Â m in the cone center. The land subsidence occurred in later 1970s in the Nantong city. Since then, the land has subsided progressively, now expanded across the research area, and formed several land subsidence troughs with a maximum subsidence of more than 300Â mm. Extensive attention has being given to the regional land subsidence in due to deep groundwater withdrawal. Therefore the characteristics of the land subsidence in the research area have been investigated by evidence survey, bedrock extensometers and soil strata extensometers monitoring, leveling, and InSAR (interferometric synthetic aperture radar) measuring. Consequently, the land subsidence mechanism has been analyzed in this paper, and some potential hazard due to land subsidence has been discussed. .