Objectives As an important grain-producing area and the most populous plain area in China, the groundwater resources in the North China Plain are seriously exploited for agricultural irrigation and domestic water use, and it is of great ecological significance and socio-economic value to accurately monitor the changes of groundwater storage in the region and continuously recharge and restore the groundwater.
Methods The gravity satellite data were used to invert the groundwater storage changes in the North China Plain, and compared and analyzed with the hydrological model, precipitation information, South-North water transfer project and groundwater well information, and proposed a method to integrate shallow groundwater storage changes and deep groundwater changes to obtain the contribution of total groundwater.
Results The results show that: (1) Both gravity satellite and global land data assimilation system model estimated water storage changes in the North China Plain exhibit obvious seasonal characteristics. (2) The correlation coefficients between the gravity satellite inversions and the shallow groundwater well estimations are consistent in terms of interannual variability, multi-year trend variability and seasonal variability, with correlation coefficient greater than 0.8. (3) Considering the contribution of deep groundwater, the estimated results of integrating shallow and deep groundwater well information and the gravity satellite inversions are in better agreement than those using only shallow groundwater, and indicate that shallow groundwater is the main variation of groundwater storage change. (4) From 2003 to 2017, groundwater in the North China Plain is in a long-term deficit state, with a gravity satellite estimated groundwater deficit rate of -1.3±0.6 cm/a. From 2018 to 2020, the gravity satellite estimated groundwater deficit rate is -1.9±0.7 cm/a, which is almost consistent with the total groundwater deficit rate of -1.8±0.8 cm/a during the same period taking into account the deep groundwater; the groundwater trend in 2021 is increasing, and the growth rate of gravity satellite inversion is 12.7±1.8 cm/a, which is more consistent with the total groundwater well estimation in the same period. The correlation coefficient is 0.98, and the weighted fused total groundwater storage change is more consistent than that estimated by using only shallow groundwater. (5) Precipitation and North-South water transfer project have a direct impact on water storage changes in the North China Plain, making a significant contribution to the mitigation of groundwater storage deficits and groundwater restoration.
Conclusions The research method in this paper provides a new way to accurately observe groundwater storage changes in the North China Plain, and provides reliable verification of gravity satellite monitoring results.
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