A WSDI framework describing GRACE terrestrial water storage deficit for monitoring and tracking the drought process and spatial pattern in the Loess Plateau, China

Hao, Shuai , Zhang, Hongbo , Liu, Fang , Li, Yihang , Ning, Zhiyuan

2026-06-01 INTERNATIONAL JOURNAL OF APPLIED EARTH OBSERVATION AND GEOINFORMATION 2026   150(卷), null(期), (null页)

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Drought is a complex phenomenon characterized by the spatiotemporal propagation of water deficits. Conventional surface-based drought indices often fail to fully capture the intricate feedback mechanisms within terrestrial water storage components. This study develops a multidimensional standardized Water Storage Deficit Index framework (WSDIs, including WSDI-TWSA, WSDI-GWSA, WSDI-SMSA, WSDI-CWSA, and WSDI-SWEA) based on GRACE satellite data, using the Wei River Basin on the Chinese Loess Plateau as a representative study area. The synchronicity between WSDIs and the traditional surface drought index (e.g., scPDSI, SPEI, SRI) is investigated to track the evolutionary trajectories of major historical drought events. The results indicate that (1) the WSDI comprehensive index WSDI-TWSA exhibits the highest gray relational grade with scPDSI, demonstrating its superiority in characterizing integrated drought conditions; (2) the WSDI component indexes effectively reveal the cascade propagation from meteorological-* agricultural-* surface hydrological-* groundwater drought; and (3) a significant lag and "decoupling" phenomenon between GWSA and meteorological drivers are identified, exacerbated by anthropogenic interventions (e.g., irrigation). The WSDIs framework provides a robust tool for capturing the spatiotemporal patterns and internal mechanisms of drought, offering critical data support for risk mitigation and water resource allocation in water-scarce regions.