干旱遭遇会严重影响跨流域调水工程的效益发挥，为科学评估引江济淮工程水源区和受水区的干旱遭遇风 险，采用标准化降水蒸散指数（standardized?precipitation?evapotranspiration?index，SPEI）和 Copula 理论构建水源区和 受水区干旱指数的联合分布，分析历史和未来两个区域干旱演变规律以及干旱遭遇风险变化。结果表明： 1960—2020 年水源区和受水区发生干旱的频率分别为 27.32% 和 29.78%；未来情景下两个区域干旱发生频率均 有明显增加，尤其高排放情景下特旱发生频率增加超过 10%；非汛期水源区和受水区同时发生干旱的概率比汛期 高 5.49%；未来汛期和全年干旱遭遇频率预计有明显增加，非汛期干旱遭遇频率略有降低；在中高排放情景下 （SSP2-4.5 和 SSP5-8.5），远期干旱遭遇频率相对更高。干旱遭遇风险增加对跨流域调水工程效益发挥带来了巨大 挑战，因此迫切需要制定适应性策略，为调水工程正常运行管理和水资源可持续利用提供保障。

The inter-basin water diversion projects transfer the water resources from basins with abundant water to that with scarce water, which aims to address the problem of uneven spatial and temporal distribution of water resources. The Yangtze-to-Huaihe River Water Diversion Project is a major strategic water resource allocation project across Yangtze River and Huaihe River basins. The middle and lower reaches of the Yangtze River and the Huaihe River basin are located in the eastern monsoon region of China. The drought disasters occur frequently in these regions with the influence of monsoon climate. Due to the temporal fluctuation and spatial variability of regional water supply, the water source and the water destination regions of the project are prone to the risk of concurrent droughts. The simultaneous occurrence of drought events across the water source and the water destination regions or other conditions that are not conducive to water transfer would have a significant impact on the normal scheduling operation and efficiency of the project. In addition, with the effects of climate change and human activities, the global water cycle will be further intensified. Compound extreme events such as drought, high temperature and heat waves on a global scale will be increasing, which have a serious impact on regional water resources management, ecosystem and sustainable socio-economic development. Therefore, it is of great significance to explore the risk of concurrent drought in the water source and the water destination regions of the Yangtze-to-Huaihe River Water Diversion Project under climate change to provide scientific support for the operation of project scheduling and sustainable utilization of water resources.The risk of concurrent drought probability between the water source and destination regions of Yangtze-to-Huaihe River Water Diversion Project was investigated. The meteorological observation and the Coupled Model Intercomparison Project Phase 6 (CMIP6) climate model dataset of precipitation were integrated for both historical and future assessment. Precipitation from nine CMIP6 dataset with three scenarios was first bias-corrected using a quantile mapping approach. The Standardized Precipitation Evapotranspiration Index (SPEI) with a time scale of 6 and 12 months was calculated by monthly precipitation and temperature to describe drought condition. The appropriate marginal distribution was selected to fit the SPEI sequence. The Copula theory was then applied to construct the joint distribution of drought index in the water source and destination regions. The drought evolution patterns and drought encounter risks from 1960 to 2020 were evaluated. And further analysis of the future changes in drought encounter risks under different scenarios based on CMIP6 data was carried out.The results showed that the frequency of drought occurrence in the water source and destination regions from 1960 to 2020 was 27.32% and 29.78% respectively. In the future scenarios, there would be a significant increase in the frequency of drought occurrence in both regions, especially in the high emission scenario where the frequency of severe drought occurrence increases by more than 10%. The probability of simultaneous drought occurrence in the non-flood season of the water source and destination regions was 5.49% higher compared to the flood season. The frequency of drought encounters during the flood season and throughout the year was expected to significantly increase, while the frequency of non-flood season drought encounters was slightly reduced. In the medium to high emission scenarios (SSP2-4.5 and SSP5-8.5), the frequency of long-term drought encounters was relatively higher.The SPEI could well capture the regional drought conditions in both the water source and destination regions. The joint distribution of SPEI by the Clayton Copula function was capable to characterize the concurrent drought between the water source and destination regions. The probability of concurrent drought in the two regions during the non-flood season was relatively higher than that in the flood season. In the future scenarios, there would be a significant increase in the frequency of drought occurrence in both regions. And the frequency of drought encounters was also projected to increase in the future. Therefore, it is urgent to formulate adaptive strategies to ensure the normal operation management of water transfer projects and the sustainable utilization of water resources.