梯级水库调度对长江上游水文干旱影响机制研究

在高强度人类活动影响下，干旱已不再是严格意义上的自然灾害，而成为自然-人为复合灾害。作为长江上游最重要的人类活动，梯级水库调度改变了河流蓄存状态与水力联系，但进而如何影响气象干旱向水文干旱的传播过程以及水文干旱的发展过程，目前尚缺乏相关的机理研究。项目以长江上游为研究区域，首先利用实测降水径流资料构建标准化干旱指数系列，辨识导致干旱非一致性的驱动因子，推求能够响应长江上游环境变化的非一致性气象水文干旱指数模型；其次，采用非线性函数模型确立非一致性气象水文干旱特征定量传播关系，对比分析水库修建前后传播关系变化，阐明水库影响下气象干旱向水文干旱的传播规律；最后，耦合水文模型和非一致性水文干旱指数，对比评估有无水库影响的长江上游水文干旱演变特征，定量识别水库对长江上游水文干旱的影响。项目研究成果可为制定缓解长江上游水文干旱的水库调度方案提供理论基础和科学依据。

Drought has become a natural and artificial composite hazard rather than a purely natural hazard under the impacts of strong anthropogenic activities. As one of the most important anthropogenic activities in the Upper Yangtze River Basin (UYRB), how the cascade reservoirs in the basin affect the propagation from meteorological drought to hydrological drought and the evolution of hydrological drought through changing the river storage-discharge relationships and hydraulic connections, relevant mechanism of which is still unclear at the present. In this proposal, based on the observed precipitation and runoff data over the UYRB, the standardized precipitation index (SPI) and standardized streamflow index (SSI) will be firstly calculated to characterize the meteorological drought and hydrological drought in the UYRB, and the driving force inducing nonstationary of meteorological and hydrological drought series will be identified to develop the nonstationary standardized precipitation index (NSPI) and nonstationary standardized streamflow index (NSSI) responding to environmental changes in the UYRB; secondly, the quantitative relationships between the hydrological and meteorological drought characteristics (duration and magnitude) under nonstationary conditions will be established by a non-linear function model, and changes in the function relationships before and after the construction of cascade reservoirs will be compared to expound the propagation law from meteorological drought to hydrological drought under the impacts of cascade reservoirs; based on coupling or not coupling of reservoir operation module to the GR4J model and the developed NSSI, the contribution of reservoir operation to the intensification or mitigation of hydrological drought in the UYRB will be finally quantified by the comparative analysis of evolution characteristics of hydrological drought in the UYRB with and without consideration of the impact of reservoir operation. The research results will certainly provide an important theoretical and scientific basis for the formulation of reservoir scheduling schemes to alleviate hydrological drought in the UYRB.