Spatiotemporal Differences of Groundwater Recovery in North China Plain Using GRACE and Well Data

The long-term depletion of groundwater storage (GWS) in the North China Plain (NCP) has recovered recently, but the spatiotemporal characteristics of this recovery and its driving factors are still unclear. For this study, we estimated the GWS in the NCP using data from the Gravity Recovery and Climate Experiment (GRACE) and its Follow-On mission (GRACE-FO) and in situ well measurements. We quantified the spatiotemporal characteristics and the drivers for the transition from long-term GWS depletion to its rapid recovery in the NCP. To identify the turning point of the GWS recovery time, we used the Improved Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (ICEEMDAN) method combined with the Bayesian Estimator of Abrupt Change, Seasonality, and Trend (BEAST) algorithm. The result shows that the GWS recovery in the southern NCP (February 2020 to October 2020) occurred earlier than in the northern NCP (November 2020 to August 2021). The GWS recovery was detected 7 months earlier in in situ wells compared with satellite data. This discrepancy is attributable to the differences in the data resolution between the spatial and in situ well measurements, as well as the more drastic response of in situ wells to groundwater changes. Both precipitation and the South-to-North Water Diversion (SNWD) project affected GWS recovery, leading to the observed spatiotemporal differences. The contributions to annual GWS changes (i.e., annual ΔGWS) from climatic and human factors were further quantified. Our results indicate that climate was the dominant driver, accounting for 87.63% of the annual ΔGWS in the NCP, while human activities contributed 12.37%.