Evaluation of Terrestrial Water Storage and Flux in North China by Using GRACE Combined Gravity Field Solutions and Hydrometeorological Models

To enrich the understanding of the dynamic evolution of the water resources in North China, terrestrial water storage anomalies (TWSA) from January 2003 to June 2017 are derived using the new GRACE time-variable gravity field model Tongji-GraceCom. Additionally, the spatiotemporal characteristics of terrestrial water fluxes (TWF) at multiple time scales are analyzed based on the water budget theory in conjunction with hydrometeorological and statistical data. The results show that the quality of the Tongji-GraceCom model is superior to the state-of-art spherical harmonic models (CSR RL06 and JPL RL06), with the signal-to-noise ratio improving by 10-16%. After correcting the leakage errors with a reliable correction method, the inferred TWSA in North China presents a significant downward trend, amounting to -1.61 +/- 0.05 cm/yr, with the most serious TWSA depletion mainly clustering in the south-central area. The TWFs derived from GRACE and from hydrometeorological elements are in good agreement and both exhibit significant seasonal fluctuations induced by tracking the periodic movements of meteorological factors. However, unlike precipitation which manifests in an increasing trend, both TWFs reflect the obvious decreasing trends, indicating that North China is suffering from severe water deficits, which are mainly attributed to the enhanced evaporation and extensive groundwater pumping for agricultural irrigation.