Multi-scale deformation monitoring with Sentinel-1 InSAR analyses along the Middle Route of the South-North Water Diversion Project in China

As the longest water transfer route in the world, the South-North Water Diversion Project (SNWDP) plays a key role in mitigating the serious water shortage problem in the arid north China, and thus the routine stability monitoring of this mega infrastructure becomes a critical issue to ensure continuous fresh water supply. Compared with traditional geodetic tools such as leveling and GNSS that can only measure deformation at discrete points along the canal, modern satellite Synthetic Aperture Radar Interferometry (InSAR) that can capture subtle ground deformation over wide areas is much more suitable to accomplish this challenging task. In this study, we carried out multi-scale InSAR analyses with multi-track Sentinel-1 data stacks to monitor deformation along the Middle Route canal of SNWDP. A coarse-resolution InSAR analysis was first carried out to map regional land subsidence in north China, and the result suggested that the Middle Route canal bypassed the huge subsidence funnel in the southeast part of Hebei province and exhibited overall stability. Afterwards, the results of relatively high-resolution InSAR analyses performed within the 5 km buffering zones along the entire canal revealed that a few sections were affected by significant embankment deformation or land subsidence. In particular, the high-filled canal sections are more prone to deform, such as the cases in Ye County and Jiaozuo City in Henan province. The validation of InSAR deformation measurements with synchronous leveling in Jiaozuo City indicated that a measurement accuracy of 6 mm was achieved. Another big problem identified is the severe uneven land subsidence along the Tianjin Branch Route, which may pose great threats upon the long-term safety of local water transfer operation, and must be handled properly to avoid further degradation.