Spatio-temporal evolution characteristics of drought in Changjiang River Basin based on 3D perspective

In order to overcome the limitation of analyzing drought evolution characteristics from a single perspective with separated temporal and spatial dimensions, this study adopted a 3D spatio-temporal perspective. Based on the Standardized Precipitation Evapotranspiration Index (SPEI), a 3D identification method was applied to systematically analyze the spatio-temporal patterns, migration characteristics, and evolution of droughts in the Yangtze River Basin from 1960 to 2022. Six spatio-temporal characteristic variables of drought development and evolution were established. The results showed that 76 drought events were identified during 1960~2022, with a drought occurrence rate of 68. 0%. Summer droughts occurred most frequently, followed by spring and autumn droughts. A distinct drought-flood alternation pattern persisted from 1978 to 2003, and the trend of drought intensification has increased since 2003. Persistent drought conditions prevailed in the southwestern regions, particularly in Qinghai, southern Sichuan, Jiangxi, and Shaanxi. Both drought intensity and affected area have shown an increasing trend, while drought duration has remained relatively stable. The migration rate of droughts slowed down, with an overall southeastward expansion. The main cycles of drought intensity, affected area, and migration rate were 17 years, 17 years, and 19 years, respectively. The 3D identification method and characteristic variables provide new tools for drought monitoring and early warning systems, offering scientific support for drought prevention and water resource optimization in the Changjiang River Basin.