Determination of drought limit water level of importing reservoir in inter-basin water transfer project under changing environment

Drought occurrence and its related impacts are a major concern in many basins throughout the world. Reservoirs play a very important role in drought resistance. Compared with the reservoir flood limit water level, the drought limit water level belongs to a new concept. This paper took the Yuqiao reservoir as the study area and proposed a new method to determine the drought limit water level under changing environment. Firstly, the Mann-Kendall (M-K) method and cluster analysis method were employed to test the trend and change point of the series based on the runoff series of Yuqiao reservoir. On this basis, the runoff frequency curve and design runoff process under current condition were obtained by Pearson-III frequency analysis. Secondly, copula function was used to analyze the synchronous-asynchronous encounter probability of rich-poor runoff of Yuqiao reservoir and Panjiakou reservoir. The available transferred volume of Yuqiao reservoir in dry year was analyzed. Finally, according to the runoff and available transferred volume, the total inflow of Yuqiao reservoir in dry season was calculated. Combining water demand and total inflow of Yuqiao reservoir, the drought limit water level was calculated by month to month. The study results can provide necessary technique support for reservoir drought emergency management.