Propagation characteristics of meteorological drought to hydrological drought considering nonlinear correlations - A case study of the Hanjiang River Basin, China

Meteorological drought serves as the precursor to hydrological drought. Clarifying the propagation characteristics from meteorological drought to hydrological drought is crucial for predicting and mitigating this severe natural disaster. In this study, we proposed an assessment framework that integrates both linear and nonlinear methods to characterize the transition from meteorological to hydrological drought in terms of drought response time, effective drought transformation rate, and drought propagation threshold. Utilizing ERA5 land reanalysis data (1951-2022) and focusing on the Hanjiang River Basin in China, we analyzed drought propagation features with and without inter-basin water diversion. Extracted drought event pairs indicate that a more significant meteorological drought does not necessarily result in a more severe hydrological drought, and vice versa, which confirms the nonlinear propagation from meteorological to hydrological drought. The drought response times derived using the linear method are, on average, two months shorter than those derived using the nonlinear method. Inter-basin water diversion will weaken the drought linear correlation while strengthening the nonlinear correlation. When the annual water diversion exceeds 12.0 billion m3, the drought response time will experience a sudden reduction. This research provides a scientific method and reference for basin-scale water resource management and drought mitigation practice.