Spatial patterns of groundwater storage trends in decreasing and increasing over China

Groundwater depletion has been widely noted and discussed within the GRACE era, but few attempts have been made on the spatial patterns of groundwater storage (GWS) changes at continental or global scale. Here, we collected data from GRACE satellites, land surface and hydrology models, and in situ measurements on groundwater level, soil moisture, and reservoir storages, to identify and interpret the GWS trends in decreasing and increasing over China. First, the gridded GWS rates derived from GRACE with both iterative forward modeling and Mascon methods were compared and validated with 1582 observation wells. Then, the spatial patterns of GWS were classified into decreasing, increasing and no significant change with the Mann-Kendall test at 95% confidence. Finally, the controlling factors for increasing and deceasing were discussed through water balance analysis with a focus on climate, hydrogeology, topography, land use/cover and water usage, and the overall groundwater balance was also provided for various spatial patterns. This study highlights the complexity of GWS change at continental scale, as well as its importance for a better understanding of global water cycle.