Ground deformation associated with exploitation of deep groundwater in Cangzhou City measured by multi-sensor synthetic aperture radar images

The magnitude and severity of ground deformation over time were investigated in Cangzhou City, Hebei Province, China. A total of 17 descending orbit C-band Envisat and 22 ascending orbit L-band Advanced Land Observing Satellite synthetic aperture radar (SAR) images covering the study area between the beginning of 2007 and the end of 2010 were integrated using an enhanced small baseline subset algorithm. The annual rates of ground deformation were retrieved from combined ASAR and PALSAR interferograms in our study area where the average subsidence reached 19 mm/a and subsidence rates up to 51 mm/a were observed. Subsidence in Cangzhou is mainly caused by the excessive abstraction of groundwater from a confined aquifer and consequently the ground subsides evenly over time. A multi-sensor SAR imaging technique was used to survey the extent and severity of ground deformation associated with the exploitation of deep groundwater in Cangzhou City. With abundant observations from different wavebands, the highly accurate ground subsidence result is not only sensitive to minor ground displacement but maintains fine coherence. Additionally, the temporal resolution is improved, and the sampling period is decreased to 5 days.