Spatiotemporal Characteristics and Drivers of Groundwater Change in North China Revealed by GRACE Time-Variable Gravity

Groundwater overdraft in North China (NC) has posed adverse threats to sustainable development due to the reduction of freshwater availability. To comprehensively clarify the groundwater change and formulate reasonable control strategies, groundwater storage anomaly (GWSA) is investigated using the high-resolution time-variable gravity field model Tongji-RegGrace2019 together with the hydrological model. The results show that GWS presents a downward trend of -0.87±0.04 cm/yr from January 2004 to December 2015 and the trend aggravates to -3.71±0.49 cm/yr from January 2014 to December 2015, which is basically consistent with those detected by monitoring well. Moreover, by analyzing the spatiotemporal characteristics of GWSA with the independent component analysis (ICA) approach, the driving factors and corresponding mechanisms of groundwater changes are determined. Among the four independent components (ICs) of GWSA, the first two ICs (IC1 and IC2) cooperatively reflect the long-term and intra-annual groundwater changes caused by water consumption of coal mining and agricultural irrigation in Shanxi province, with the correlation coefficients of -0.91 and -0.85, respectively. IC3 indicates a semi-annual groundwater signal related to agricultural irrigation water consumption in southern Hebei province, with a correlation coefficient of -0.85. Besides, IC4 suggests the effect of monsoon precipitation and evaporation in front of Taihang Mountain. Hence, multiple driving sources, including unevenly distributed precipitation, intense seasonal evaporation, and devastating coal mining, coupled with extensive agricultural irrigation, jointly restrict the GWSA rise and fall at different time nodes.