Presenter
Dr. Xin He
Co-author(s)
Ms. Rong Liu, Prof. Yong Zhao
Organisation
China Institute of Water Resources and Hydropower Research
Sub-theme
4. Supporting Aquatic Ecosystem Health and Functions
Topic
4-7. Groundwater and ecosystem
Body
The North China Plain has experienced long-term overdraft of groundwater resources in the past few decades, which has resulted in one of the largest groundwater depression cones in the world, as well as severe and complicated land subsidence problems. It is known that land subsidence not only threatens the safety of buildings on the land surface, but also causes irrecoverable loss of deep groundwater reserves, which will pose a serious threat to regional water security in the future. The study first uses ground based leveling observation data and remote sensing based Interferometric Synthetic Aperture Radar (InSAR) data to estimate the cumulative land subsidence volume in the North China Plain. The results show that the cumulative subsided volume is over 75.6 billion m3 as of 2019. It is also calculated that the cumulative subsided depth at the center of the subsiding area has exceeded 2500 mm as of 2019. Although multiple measures have been taken by both the central and local government in the groundwater overdraft provinces in the past few years in order to limit the amount groundwater abstraction, cities like Hengshui and Xingtai continue to experience land subsidence at a rate over 130 mm/year. Furthermore, the study established a one-dimensional nonlinear numerical model for water compaction and release in deep confined aquifer systems. Using such model, it is simulated that there is substantial amount of irrecoverable groundwater storage in the North China Plain due to clayey material compaction and therefore causing permanent loss of groundwater reserves at 55.8 billion m3. In addition, based on the land subsidence rate obtained from time-series InSAR data in the past five years, the study shows strong correlation between land subsidence, groundwater level changes and the amount of groundwater abstraction. Subsequently, risk zones are delineated and critical water levels for controlling land subsidence, namely thresholds for low-risk deep groundwater abstraction amount, are discussed.