Dominant Drivers for Terrestrial Water Storage Changes Are Different in Northern and Southern China

Subsurface water storage is a key component in the water cycle, and China is facing severe issues with water resource shortage. This study estimates the terrestrial water storage (TWS) changes from 2003 to 2017 using a water balance approach over seven large basins in China. The estimated inter-annual variations and trends in TWS correspond well with those obtained from the Gravity Recovery and Climate Experiment observation. Variance analysis shows that annual precipitation in northern China plays a more important role in controlling annual TWS variability than that in southern China. This increased sensitivity is primarily attributed to the limited availability of water resources and the arid climate conditions prevalent in northern China. Interestingly, actual evapotranspiration is the dominant driver, contributing more than 55% to the declining trend in TWS in two northern basins: Hai River and Yellow River basins, where the leaf area index has strongly increased. Precipitation and evapotranspiration account for over 89% of the TWS trend over basins in northeastern China. Meanwhile, the dominant drivers for TWS in southern China are precipitation (50%-54%) and runoff (33%-41%). Our results suggest that it requires strong ecological conservation actions in order to keep water resources sustainable in northern China.