Understanding drought propagation through coupling spatiotemporal features using vine copulas: A compound drought perspective

Inter-basin water transfer will face greater drought risk in the future

Inter-basin water transfers (IBWT) are vital for regional and basin water security. However, climate change, characterized by reduced runoff and frequent extreme droughts, poses significant challenges to these projects. This study aims to explore the compound drought risks of past and future IBWT Projects (IBWTP) in Yellow River Basin(YeRB), Huai River Basin(HuRB), Hai River Basin(HaRB), and Yangtze River Basin(YaRB) from 1965 to 2100. Using the latest CMIP6 data and hydrological models, we predicted future runoff changes and calculated the standardized runoff index (SRI). We then evaluated the compound drought risks using two-dimensional and three-dimensional copula methods. This study assesses the compound hydrological drought risks of IBWTPs under different climate scenarios (SSP1-2.6, SSP3-7.0, SSP5-8.5) using CMIP6 projections. Historical drought risks ranged from 5.29 % to 25.64 %, with YeRB and HaRB facing the highest frequency and intensity. Future projections show significant increases in drought intensity, especially in HuRB and YaRB under SSP1-2.6, with a rise of up to 28.42 %. Under SSP3-7.0 and SSP5-8.5, drought intensity continues to increase, with the Far-Future showing up to a 26.4 % increase.For constructed IBWTPs, compound drought risks increase across all scenarios. In SSP1-2.6, risks range from 7.46 % to 29.75 %, decreasing in the Far-Future (4.43 %-26.31 %). In SSP3-7.0 and SSP5-8.5, risks increase, with SSP5-8.5 reaching 6.17 %-25.34 % in the Far-Future. Planned IBWTPs show moderate increases, highlighting the need for projects to be designed with higher baseline risks for resilience. These findings emphasize the importance of adaptive water resource management and IBWTP design to address future drought risks under climate change.