A study on time lags between groundwater changes and land subsidence based on GRACE and InSAR data

The increasing dependence on groundwater in the Hexi region has led to a significant drop in the groundwater table, which has induced land subsidence in some areas. Studying the relationship between groundwater changes and land subsidence hysteresis in the Hexi region holds great significance for local water resource management, land use planning, and agricultural development. This study determined the changing rate of groundwater in the study area from 2010 to 2017 using the GRACE and GLDAS data and verified the reliability of the inverted groundwater changes by combining measured data from monitoring wells. Then, this study derived the surface deformation rate of the local subsidence areas from October 2014 to June 2017 using the small baseline subset interferometric synthetic aperture radar (SBAS-InSAR) technique, as well as comparing and validating the results using the persistent scatterer interferometric synthetic aperture radar (PS-InSAR) technique. Finally, this study analyzed the relationship between groundwater changes and surface subsidence data using fast Fourier transform and time-delay correlation analysis. The results indicate that the time lags between land subsidence and groundwater changes were 74~86 d, 61~80 d, 80~99 d, and 74~99 d, respectively in the Linze, Ganzhou, Liangzhou, and Jinchuan subsidence areas, with respective correlation coefficients ranging from 0.541 to 0.593, from 0.589 to 0.689, from 0.600 to 0.750, and 0.543 to 0.630, respectively. The results of this study will provide a scientific basis for water resource management, land use planning, and agricultural development in the Hexi region.