Assessment and attribution of China’s droughts using an integrated drought index derived from GRACE and GRACE-FO data

Different definitions of drought from multiple perspectives complicate drought studies. Studying droughts from an integrated perspective helps to better understand their evolutions and driving factors, but few studies have taken such a comprehensive approach in China. This study conducted an assessment and attribution analysis of droughts across China from 2002 to 2020 based on an integrated drought index derived from observed terrestrial water storage (TWS) data. First, the latest solution of satellite gravimetry data was employed to analyze spatiotemporal changes in TWS deficits. Second, droughts associated with TWS deficits were detected using the Water Storage Deficit Index (WSDI). Third, an attribution analysis was conducted using the stepwise regression method to determine the driving factors of droughts. The results show that China’s TWS decreases at a significant rate (−1.79 ± 0.43 mm/yr, P < 0.05) from 2002 to 2020. The droughts detected by WSDI can generally combine the durations and intensities of the meteorological, hydrological, agricultural, and socioeconomic drought indices, which provides a comprehensive perspective. The severity and intensity of countrywide drought have been at least doubled, especially in the northern regions (including the Northern Arid and Semiarid region, the Huang-Huai-Hai Plain, and the Loess Plateau). The attribution analysis revealed that both climate change and anthropogenic impacts played a dominant role in driving intensified droughts. Decreasing precipitation explains 20% to nearly 100% of TWS deficits across the Huang-Huai-Hai Plain. Human water use, especially for agriculture, has also exacerbated droughts in the water-scarce northern regions of China. The WSDI was highly correlated with the water supply for human activities in the Northern Arid and Semiarid region and the Loess Plateau. This study shows the need to adopt measures to limit human water use beyond the regional capacity.