Spatial Heterogeneity in Drought Propagation from Meteorological to Hydrological Drought in Southern China and Its Influencing Factors

Southern China, despite its humid climate, has increasingly faced severe hydrological droughts (HDs) in recent decades, highlighting the complexity of drought propagation. Most existing studies primarily examined the relationship between drought propagation and climatic factors, whereas quantitative analyses of interactive effects of underlying surface characteristics on drought propagation remain insufficient. This study introduces an integrated framework combining GRACE satellite-derived terrestrial water storage anomalies with topography, land use, geology, and climate data to examine HD formation and its drivers. The results show a clear divergence between meteorological drought (MD) and HD patterns, revealing that underlying surface characteristics, rather than precipitation deficits alone, drive HD spatial patterns. Among drought propagation indicators, intensity has the strongest link to environmental factors, positively correlating with elevation and slope, and negatively with mean annual precipitation and temperature. Forest coverage helps mitigate drought intensification, while karst geology and land use influence propagation timing. HD intensity follows an elevational gradient, with severe droughts in high-altitude areas and mild, frequent droughts in low-lying basins. These insights provide a mechanistic basis for developing early-warning systems and spatially adaptive water management strategies, thereby supporting sustainable drought resilience and promoting long-term water resource sustainability in Southern China.