A review on land subsidence caused by groundwater withdrawal in Xi’an, China

This paper presents a review on the land subsidence caused by groundwater withdrawal in Xi’an, China. With the increasing demands of people’s livelihood and economy during the urbanization process, Xi’an has suffered severe hazards due to land subsidence caused by the excessive exploitation of groundwater since the 1960s. According to past records, the development of land subsidence in Xi’an can be divided into three stages; i) preliminary stage (1959 to 1971), ii) rapid development stage (1972 to 1990), and iii) slow development stage (1991 to present). In the 1990s, the annual groundwater withdrawal volume reached the maximum value of about 1388 × 106 m3/year, and the annual land subsidence also reached the maximum value (about 130 mm/year). The policy for controlling groundwater withdrawal was announced by the Xi’an Municipal Government in 1996, and then the land subsidence rate showed a significant descending tendency. Many researchers developed a series of approaches to yield the prediction of land subsidence caused by groundwater withdrawal, which can be divided into three categories: i) mathematical statistics approaches; ii) numerical approaches; iii) artificial intelligence approaches. Not only are the approaches’ advantages and disadvantages analyzed in this paper, but three emerging investigations on land subsidence in Xi’an are also discussed. The three emerging investigations aim to: i) analyze the relationship between land subsidence and ground fissures, ii) search the monitoring techniques available for obtaining more accurate data, and iii) investigate the effect of sand particle crushing under high stress level on the development of land subsidence.