Long-Term Time Series InSAR deformation monitoring study of the Jiaozuo section of the Middle Route of the South-to-North Water Diversion Project in Henan Province

The Middle Route Project of the South-to-North Water Diversion is an important linear water conveyance project. To ensure the safe operation of the project, it is crucial to fully understand the spatiotemporal evolution characteristics of deformation in the canal and its surrounding areas and to avoid errors caused by a short monitoring period. Taking the Jiaozuo section in Henan Province as an example, the paper acquires 151 Sentinel-1A images collected over nearly six years from October 2016 to November 2021 and utilizes long-term InSAR techniques to monitor deformation of the canal foundation and adjacent regions. GACOS products are used to correct atmospheric delays, thus reducing the influence of atmospheric effects in long-distance linear engineering monitoring by InSAR. The results show that there is significant deformation at the levee near the canal bend in Xincheng Subdistrict, Shanyang District of Jiaozuo section; four subsidence zones are detected near the main canal in Macun District, with the nearest subsidence area being less than 200 m from the canal. Surface subsidence in the Jiaozuo section of the Middle Route exhibits obvious spatial heterogeneity, with varying degrees of subsidence throughout the entire region. The maximum annual average subsidence rate is 81.49 mm/a, which occurs in the northern part of Yanma Subdistrict, Macun District, and the largest subsidence funnel is at the junction of Shanyang District and Wuzhi County. Comparison and validation with second-order leveling measurements during the same period show a mean error of 1.83 mm and a correlation coefficient (R²) of 0.92 between the two. The study shows that the long-term InSAR method can effectively avoid misjudgments caused by seasonal fluctuations in the subsidence field and abnormal rainfall in certain years, enabling comprehensive investigation and detailed monitoring of large-scale water conservancy projects.