Satellite-based Estimates of Ground Subsidence in Ordos Basin, China

Abstract

Abstract This paper reports the findings based on ALOS-1 and GRACE satellite data for the purpose of monitoring land surface subsidence due to groundwater extraction and underground mining activities in the Ordos Basin, China. 42 ALOS-1 PALSAR data (22 images from Frame 790 while 20 scenes from Frame 780) acquired between 8 January 2007 and 19 January 2011 are utilized in the time-series InSAR (TS-InSAR) analysis while the total water storage observations derived from the Gravity Recovery and Climate Experiment (GRACE) satellite data are integrated with hydrological modeling results (for soil moisture modelling) to estimate the groundwater depletion rate. Since the results have vast difference in spatial resolution between GRACE (~300 km) and InSAR (~10’s of meters), the two measurements are not comparable over the same region. Instead, we applied them to Haolebaoji surrounding region and ALOS covered area, respectively. The groundwater change series of about –7.3 mm yr–1 between December 2006 and June 2012 is detected, which is then being exploited to explain the groundwater induced subsidence in Haolebaoji, Inner Mongolia. Within ALOS covered region, time-series analysis was carried out to explain the local subsidence. Then the total area size of underground mining sites is estimated, and we concluded that human involved activities contribute a lot to the total velocity and this part of subsidence should be excluded before estimating the final mean velocity (–4.9 mm yr–1 in vertical direction) when comparing with GRACE-based groundwater depletion series. Last but not least, some suggestions are given on how to make a rational comparison between the InSAR derived mean velocity with GRACE-based groundwater depletion trend together. This study could help the local government and associated geotechnical engineers to have a better understanding of the groundwater induced subsidence in this region.