Research on drought driving factors in karst regions of Southwest China based on multisource remote sensing data

Due to the complexity of drought causation and the unique characteristics of karst regions, drought occurrences in such areas are often influenced by multiple variables. Relying solely on single or bivariable indices is insufficient for comprehensive monitoring of the intricate drought phenomena in karst regions. To comprehensively analyses the drought driving factors in Southwest China, this study leverages the dense vegetation, significant evapotranspiration, and uneven precipitation typical of such regions. Using the Vegetation Water Supply Index (VSWI), Crop Water Stress Index (CWSI), and Vapour Pressure Deficit (VPD), this study identifies the dominant drought drivers in the region. The results show that bedrock exposure, closely related to karst development, is a key factor influencing CWSI and VSWI, while VPD is primarily controlled by atmospheric processes. Spatial analysis confirms a strong correlation between bedrock exposure and karst landforms (0.410), highlighting the role of natural karst processes such as chemical weathering and dissolution. In contrast, the weaker correlation with land use types (0.165) suggests minimal influence from human activities. These findings underscore the critical importance of geological factors, particularly bedrock exposure, in shaping regional drought conditions.