考虑设计洪水不确定性的梯级水库防洪调度风险评估与应对

Design flood provides primary basis for designing reservoir flood control operations and ensuring safety of dam and protection objects. Worthy of note is that multiple uncertainties due to natural randomness and human cognition exist in design flood estimation. These uncertainties are often overlooked during traditional design flood estimation, thus reducing applicability of reservoir flood control operations and increasing the risk of dam and protection objects safety. This study selects the cascade reservoirs in the upstream of the Yellow River as research object. Focusing on the multiple uncertainties existed in design flood estimation, we propose one gradual and deep-going three-step research system, i.e. risk recognition, assessment and adaptation of flood control operations of cascade reservoirs. The so-called risk recognition is basis, aiming to disclosing multiple uncertainties in the design flood estimation model based on the multivariate joint distributions (such as the Copula function) within the context of cascade reservoirs; risk assessment provides direction for identifying the major and minor risk source affecting the flood control of cascade reservoirs through the probabilistic (stochastic collocation method et al.) and non-probabilistic (Dempster-Shafer evidence theory et al.) methods; risk adaptation is the target, focusing on extracting reservoir operations to response risk of flood control on the basis of risk-based flood control programming under major risk source through the stochastic planning method, interval planning method et al. Obtained results are of great theoretical and practical significance for risk management of flood disaster at basin scale.

设计洪水是制定水库防洪调度规则、确保大坝与防护对象安全的主要依据。在水库群设计洪水计算中存在随机与认知多重不确定性因素，传统设计洪水计算对此考虑不足，使得水库防洪调度规则的适用性降低，水库自身安全、下游防洪对象安全等面临极大风险。本次研究以黄河上游梯级水库为研究对象，面向设计洪水计算中的多重不确定性因素，提出了梯级水库防洪调度风险“识别—评估—应对”三层次逐步递进研究体系。“识别”是基础，采用多维Copula函数等方法建立梯级水库设计洪水计算模型，识别影响设计洪水计算的多重不确定性因素；“评估”是方向，应用随机配置法、证据理论等概率与非概率方法，评估设计洪水不确定性下水库防洪调度风险，指明主要与次要风险来源；“应对”是目标，面向主要风险来源，基于随机规划、区间规划等理论，建立梯级水库防洪调度风险规划模型，推求相应风险应对规则。研究成果对流域洪水灾害风险管理具有重要的理论价值与现实意义。

本研究以建立考虑设计洪水不确定性的梯级水库防洪调度风险应对理论、模型与方法体系为目标，开展了考虑不确定性的多元设计洪水计算研究，量化了不同重现期下的设计洪水不确定性，发现随着重现期的增加，设计洪水不确定性快速增加；基于极限风险率概念，推求了设计洪水量级、峰现时间与水库防洪极限风险率间的响应关系；开发了基于信息熵的不确定性传播量化框架，揭示了设计洪水不确定性在水库防洪调度系统中的传播过程，发现了水库优化调度系统对设计洪水不确定性的削弱现象；引入经济学指标条件风险值CVaR来衡量水库防洪调度过程中超过调洪最高洪水位的风险，建立了考虑CVaR 的水库防洪调度模型，揭示了风险偏好系数与水库控制水位间的响应关系，获得了不同风险系数下的水库防洪调度规则；构建了基于随机动态规划算法的水库防洪调度模型，提出了设计洪水不确定性下的水库防洪调度规则，并将该算法进行改进、完善，形成了考虑多维过程关联性与随机性的随机动态规划算法，扩展性的应用于水库供水优化调度中。