南水北调中线水源区和受水区干旱遭遇风险评估

基于 1961—2019 年气象观测数据和 CMIP6 模式数据，利用标准化降水蒸散指数（standardized?precipitation evapotranspiration?index，SPEI）计算南水北调中线水源区和受水区的干旱指数，并利用经验正交分析法、主成分分 析法和 Copula 函数法，对水源区与受水区的干旱演变规律进行分析，揭示干旱遭遇的联合概率分布，并对未来干 旱遭遇进行预估。研究结果表明：水源区和受水区干旱事件遭遇频繁，1965—1971 年和 1987—2005 年均出现较 为严重的干旱遭遇事件，同时在 1970 年代中后期至 1985 年前后，出现了长期明显的区域差异性；水源区和受水区 中旱和重旱的联合重现期分别约为 18 年一遇（5.51%）和 123 年一遇（0.81%），两地同时出现极端干旱的重现期约 为 323 年一遇（0.31%）；不同气候情景下以年尺度 SPEI 指数，对南水北调中线水源区和受水区的未来干旱事件预 估表明，未来水源区和受水区在 SSP1-2.6 情景下干旱遭遇次数相对较少，而在 SSP2-4.5 情景下的 2034—2036 年、 2044—2045 年以及在 SSP5-8.5 情景下的 2032—2033 年、2068—2070 年，将有可能发生较严重的干旱遭遇事 件。

Risk assessment of drought in the source and receiving areas of the middle route of South-to-North Water Transfer Project

The South-to-North Water Transfer Project is of great strategic significance for improving the national water network and optimizing the overall pattern of water resource allocation. The drought situation and water quantity changes in the source area of the South-to-North Water Transfer Project affect the stability of the water transfer project and are of great significance to the industrial, agricultural, and residential water use and other aspects of the cities along the route. In recent years, there has been more research on extreme drought monitoring, and a variety of meteorological hydrological drought index models have been widely used, such as the standardized precipitation evapotranspiration index, palmer drought index, standardized precipitation index, and so on. The standardized precipitation evapotranspiration index model is superior to the other two drought index models because it takes into account the evapotranspiration factor. Although some research has been conducted in recent years on climate change in the water source or water-receiving areas of the South-to-North Water Transfer Project, few studies have explored the drought encounters in water source and water-receiving areas in the context of future climate change.By integrating a large number of meteorological observation data and the latest Coupled model Intercomparison Project Phase 6 (CMIP6) climate model data, using standardized precipitation evapotranspiration index, empirical orthogonal function analysis, Copula function, and other methods, the spatial and temporal distribution of drought in the water source area and the water receiving area of the South-to-North Water Transfer Project in the historical period was calculated. The drought encounter problem in the water source area under different climate scenarios in the future was estimated using the CMIP6 meteorological dataset as the driving data and then provided a theoretical basis for water resources planning and management. The empirical orthogonal function was performed using the calculation results of the SPEI and the copula function for the joint probability distribution of drought between the water source and the water receiving area. The mean CMIP6 multi-mode data is used as the input data for future SPEI calculations, and the drought comprehensive evaluation is carried out on the water source area of the South-to-North Water Transfer Project.Results showed that drought events in water-source areas and water-receiving areas were frequent, with more serious drought encounters in 1965-1971 and 1987-2005, and long-term obvious regional differences from the mid-to-late 1970s to around 1985. The combined recurrence periods of drought and severe drought in water-source areas and water-receiving areas were about once in 18 years (5.51%) and once in 123 years (0.81%), respectively, and the recurrence period of extreme drought in both places was about once in 323 years (0.31%).The annual SPEI estimates of future drought events in different climatic scenarios indicate that the number of future drought occurrences under the SSP1-2.6 scenario is relatively small, while the more severe drought encounters in the water source and water-receiving areas may occur in 2034-2036 and 2044-2045 under the SSP2-4.5 scenario and in 2032-2033 and 2068-2070 under the SSP5-8.5 scenario. Multi-modality and multi-scenarios indicate that the risk of drought in the water source area and the water-receiving area of the South-to-North Water Transfer Project may increase in the future. To better play the benefits of the project, it is necessary to strengthen the research on the drought encounter problem in the water source area and the water-receiving area of the middle line of the South-to-North Water Transfer Project.