Key Laboratory of the Ministry of Education Land Subsidence Mechanism and Prevention, Capital Normal University, Beijing 100048, China; College of Geospatial Information Science and Technology, Capital Normal University, Beijing 100048, China; College of Resources Environment and Tourism, Capital Normal University, Beijing 100048, China.
Key Laboratory of the Ministry of Education Land Subsidence Mechanism and Prevention, Capital Normal University, Beijing 100048, China; College of Geospatial Information Science and Technology, Capital Normal University, Beijing 100048, China; College of Resources Environment and Tourism, Capital Normal University, Beijing 100048, China.
Sci Total Environ. 2020 Sep 15;735:139111. doi: 10.1016/j.scitotenv.2020.139111. Epub 2020 May 4.
Beijing is a major metropolis with significant land subsidence because of long-term overexploitation of groundwater. While the South-to-North Water Diversion Project (SWDP) has provided new water sources Beijing; it has changed the pattern of land subsidence evolution in Beijing since 2015. Here we address how land subsidence evolution before and after SWDP, and we quantify also the impact of groundwater level changes in different aquifers on land subsidence at spatial scale. Subsidence evolution before and after SWDP were compared by adopting Persistent Scatterer Inteferomotry (PSI) with Radarsat-2 and Sentinel-1 data. Spatial correlation between Interferometric Synthetic Aperture Radar (InSAR) derived subsidence and groundwater levels in four aquifers was investigated using the Random Forest (RF) machine learning algorithm and Geographical Detectors (GD) technique. Extensometer deformation data and corresponding variation in groundwater level observations at three monitoring stations were used for validations. The study reveals that: firstly, both InSAR-derived subsidence area and maximum annual deformation rate decreased from 79.2% and 141 mm/yr before SWDP, to 60.1% and 135 mm/yr after SWDP. A reduction of time series deformation at four subsidence centers started about two years after the commence of SWDP in 2015. Secondly, the variation of groundwater level in the second confined aquifer has the strongest spatial correlation with subsidence in all the aquifers, but its impact on this aquifer has decreased after SWDP. These findings have an important scientific significance for the rational allocation of water resources and management strategy for mitigating hazards associated with subsidence against the background of SWDP.
北京是一个主要的大都市，由于长期过度开采地下水，存在严重的地面沉降问题。南水北调工程（SWDP）为北京提供了新的水源，但自 2015 年以来，改变了北京地面沉降演化的格局。在这里，我们研究了 SWDP 前后地面沉降的演化，并定量评估了不同含水层地下水位变化对空间尺度地面沉降的影响。采用 Radarsat-2 和 Sentinel-1 数据的永久散射体干涉测量法（PSI）对 SWDP 前后的地面沉降演化进行了比较。利用随机森林（RF）机器学习算法和地理探测器（GD）技术，研究了干涉合成孔径雷达（InSAR）衍生沉降与四个含水层地下水位之间的空间相关性。利用三个监测站的伸缩仪变形数据和相应的地下水位观测值进行验证。研究结果表明：首先，SWDP 前，InSAR 反演的沉降面积和最大年沉降速率分别为 79.2%和 141mm/yr，SWDP 后分别降至 60.1%和 135mm/yr。四个沉降中心的时间序列变形在 2015 年 SWDP 开始约两年后开始减少。其次，第二承压含水层地下水位的变化与所有含水层中的沉降具有最强的空间相关性，但 SWDP 后其对该含水层的影响有所减弱。这些发现对于 SWDP 背景下，合理配置水资源和管理策略以减轻沉降灾害具有重要的科学意义。
