Future propagation characteristics of meteorological drought to hydrological drought in the Yellow River basin

An in-depth understanding of drought evolution in the Yellow River Basin (YRB) is essential for effective drought prevention and water resource management. This study coupled the model data released by CMIP6 and the PCRGLOBWB model to simulate the hydrological processes in the YRB, and characterize the spatial and temporal distributions of meteorological and hydrological droughts in the period of 2021-2050 (T1 period) and 2051-2080 (T2 period). Furthermore, this study explored the propagation characteristics from meteorological droughts to hydrological droughts. The results indicate that future climate change significantly impacts meteorological-hydrological droughts and their propagation characteristics in the YRB. In T1, overall meteorological drought tends to alleviate with increasing emission scenarios. However, in T2, meteorological drought duration and severity worsen, with fewer but more severe drought events compared to T1. Hydrological drought worsens in the future and exceeds past severity, with minor differences between emissions scenarios. Additionally, the study reveals the correlation between meteorological and hydrological droughts in the basin, with an enhanced correlation in upstream regions as emission scenarios intensify, indicating a rapid hydrological response to climate change. Notably, there are significant differences in drought propagation timescales across the basin, primarily concentrated at 2-10 month scales. The effective propagation rate ranges from 37 % to 50 % in T1 for low emission scenarios, but significantly decreases across the entire basin in T2, with decreasing trends in propagation rates for all sub-basins with increasing emission scenarios. These findings enhance understanding of future drought risks in the YRB and inform relevant policy development.