自然科学版学报

跨流域调水深刻改变了白洋淀淀区下垫面的供水条件，揭示淀区下垫面供水量与实际蒸散发量(ET_a)的关系对于淀区用水安全和水资源管理具有重要意义。采用基于Budyko理论的傅抱璞经验公式对白洋淀淀区的ET_a进行计算，然后运用Archimedean Copula函数对淀区不同供水组合与ET_a的联合分布进行研究。结果表明：跨流域调水前后白洋淀淀区多年平均ET_a分别为547.24、583.96 mm,且ET_a变化趋势与下垫面的供水变化趋势相同；不同Archimedean Copula函数均可较好地描述下垫面供水量与ET_a的相依关系和联合概率分布特性；同时段“P+R+Q与ET_a”与“P+R与ET_a”的联合概率相比下降了0.06,条件概率下降了0.04,条件重现期增加了6.67年，在二者均值所构建的联合分布中，联合概率下降了0.10,条件概率下降了0.26。以上结果表明，实施跨流域调水工程以来，白洋淀淀区水资源短缺风险有所降低。

Cross-basin water transfer has profoundly changed the water supply conditions of the underlying surface in Baiyangdian District, and studying the relationship between the water supply amount and actual evapotranspiration(ET_a) in the Dian District is of great significance for water safety and scientific management in the Dian District. In this study, the empirical formula of Fu Baopu based on Budyko theory was used to calculate the ET_a in Baiyangdian Lake, and then the Archimedean Copula function was used to study the joint distribution of different water supply combinations and ET_a in the area. The results showed that the average annual actual evapotranspiration in Baiyangdian District before and after cross-basin water transfer was 547.24 mm and 583.96 mm, respectively, and the ET_a trend was the same as that of the underlying water supply. Different Archimedean Copula functions can better describe the dependence relationship and joint probability distribution characteristics of the underlying water supply and ET_a. Compared with “P+R+Q and ET_a” and “P+R and ET_a”, the joint probability decreases by 0.06, the conditional probability decreases by 0.04, and the conditional recurrence period increases by 6.67 years. In the joint distribution constructed by the mean of the two, the joint probability decreases by 0.10. The conditional probability decreased by 0.26; It shows that the risk of water shortage in Baiyangdian District has been reduced since the implementation of inter-basin water transfer project.