Analysis and Simulation of Land Subsidence Caused by Groundwater Exploitation in the Hangzhou-Jiaxiang-Huzhou Plain, Southern China

The Hangzhou-Jiaxing-Huzhou (Hang-Jia-Hu) Plain in Zhejiang Province, located between the Yangtze and Qiantang Rivers, is one of the fastest economic growing regions in China. The Hang-Jia-Hu region has experienced severe land subsidence since 1960. The maximum accumulated subsidence is approximately 1,100 mm and the total affected area with accumulated subsidence over 50 mm is 4,200 km². Geological and hydrogeologic surveys reveal a multi-layered aquifer system beneath the plain, which is composed of Quaternary deposits. Based on the historical records of groundwater extraction, groundwater levels, and land subsidence from 1964 to 2006, it is shown that ground subsidence has resulted from the continuously excessive extraction of ground water from deep confined aquifers. The characteristics of aquifer system compaction and land subsidence are complex because of different soil types and compositions as well as a long history of pumping activities. MODLFOW-2000 with the subsidence and aquifer-system compaction (SUB) package was used to simulate the areal distribution of individual layer compaction and the dynamic process of groundwater flow and land subsidence. By calibrating the model with the measured groundwater levels, areal distribution of land subsidence, and compaction of individual hydrostratigraphic units at an extensometer group located in Jiaxing City, we estimated the hydrogeologic parameters of aquifers and the aquitards interbeded between aquifers. The model results fit reasonably well with the observed ground water levels and land subsidence development and show that the land subsidence centers generally match the ground water depression cones. The calibrated model provides a scientific basis for managing the beneficial use of groundwater resources in the Hang-Jia-Hu region while minimizing negative environmental impacts.