Exploration of the Relationship between Ground Subsidence Evolution and Groundwater Variation in the Middle Route of South-to-North Water Diversion Project

Abstract

The South-to-North Water Diversion Middle Route Project (SNWD-MRP), traversing two major crop-producing areas and population centers from Henan to the Beijing-Tianjin-Hebei (BTH) region in northern China, holds profound significance in alleviating the scarcity of land water resources and improving the local ecological environment. This contribution focuses on the development and evolution of ground subsidence funnels along the MRP since its implementation. Therefore, we introduce a wide-area subsidence monitoring method that combines the FS-InSAR subsidence extraction with ground-based calibration among different frames to acquire the time-series observation values of subsidence funnels along the MRP. Then, SAR image data acquired by the Sentinel-1A satellite from June 2017 to December 2021 are utilized. On this basis, correlation analysis is conducted based on measured groundwater level data along the route, aiming to explore the relationship between groundwater level variability and the dynamic evolution of uneven subsidence. The results reveal a high degree of spatial coincidence between regions of groundwater over-exploitation and major subsidence funnels in areas such as east Beijing, Baoding to Handan, and north Henan. Furthermore, the inter-annual dynamic evolution of InSAR subsidence is found to be highly correlated with groundwater level variability (R: 0.6 ~ 0.9), identifying groundwater deficit as the primary controlling factor of ground subsidence in the North China Plain. Notably, ground subsidence in areas encompassing the Beijing and Tianjin branches of the MRP exhibits a gradual slowdown and stabilization trend, while the subsidence rate in the Baoding to Handan segment along the MRP has significantly decelerated compared to surrounding regions. In general, the SNWD Project has made significant strides in alleviating water scarcity in northern China and has effectively mitigated uneven subsidence, underscoring its pivotal role in regional water resource management.

Keywords: SNWD, subsidence funnels, time-series InSAR, groundwater level variability, dynamic subsidence evolution