Analysis of the factors resulting in the acceleration of land subsidence in the central area of Dezhou city, China.

The groundwater system in the strata within 800 m of Dezhou city, which is located in the North China Plain (NCP), China, includes four aquifer groups (labeled AgI to AgIV from top to bottom). The exploitation of deep groundwater from AgIII and AgIV is generally considered the primary reason for land subsidence in Dezhou. Although the deep groundwater exploitation volume has decreased significantly, the annual land subsidence has been accelerating in the central area of Dezhou since 2012. The factors resulting in the acceleration of land subsidence are discussed. Presently, AgII and AgIII between 60 and 500 m below the ground surface are the two main layers contributing to land subsidence, the settlement of which accounted for 74% of the total subsidence value. The increasing settlement of AgIII may be due to the soil creep caused by the continuous release of groundwater from AgIII. AgII is characterized by high compressibility, the deformation of which is susceptible to a decrease in the groundwater level. Since AgII is not the historical groundwater exploitation layer, the decrease in the groundwater level of AgII may be caused by the downward leaking recharge to AgIII and lateral recharge to the surrounding cities in the NCP. The study of the deformation mechanism of AgII is essential for subsidence control in Dezhou. Geological investigation and groundwater-level monitoring of AgII and joint control of regional groundwater overexploitation in the NCP should be strengthened. [ABSTRACT FROM AUTHOR]