Risk Evaluation Methodology Study Of River Diversion Under Impact Of Upstream Impoudment And Regulation

River diversion is the key process throughout the construction of hydropower engineerings, and risk evaluation and standard decision of the diversion system are core of the planning and design. However, when hydropower stations are constructed in cascade, the effect of impoundment and regulation (EIR) of the upstream power station changes the nature of the construction flood, furthermore perplexes risk elements and the process of coupling. In addition, in such condition the upstream power station is involved in the diversion system of the downstream power station, thus the decision scope is extended from the interior of the downstream to the alliance of the upstream and the downstream. Such changes bring about the huge challenges to the risk management of diversion system. Hence combining different methods and theories, such as risk analysis, system simulation, Copula function, multi-attribute group decision, cooperative game, and interactive negotiation, this paper systematically studies characteristics of the risk elements and the process of the coupling, and explores the negotiation decision of the diversion standard under the environment of multi-attribute, multi-agent, and multi-level. The study provides new ideas and methods for risk analysis and risk control of the diversion system under cascade development. The main contents are studied as follows:(1) Firstly, in allusion to the impoundment effect of normal operation of the upstream power station on the construction flood, on the basis of exploring the characteristics of the diversion risk factors and the coupling mechanism, the joint distribution of flood peak and discharge is built with Copula function. According to the module of the upstream impoundment, the module of flood routing in channels and the module of regional flood merging, the construction flood under the influence of impoundment is ascertained, and furthermore the flood risk of diversion system is calculated.Secondly, introducing the flood forecasting technique into the river diversion, the construction flood is controlled with temporary forecasting predischarge regulation (TFPR) of the upstream power station. Based on the analysis of the feasibility of the FFPR, the lognormal and triangular distribution are introduced to respectively describe the uncertainty of flood forecasting errors and the uncertainty of the FFPR lag, and the diversion risk estimation models under FFPR is established in which the risk factors of diversion system are coupled with simulation technology.Furthermore, expanding the upstream impoundment or regulation effect to the construction period in which the diversion is conducted synchronously, in allusion to the long, wide and gentle waterway, the risk estimation model of the downstream diversion system is established in which the cofferdam breach flood and its uncertainty are considered. Moreover, considering the inter-relationship of the upstream and the downstream diversion system in such condition, two diversion systems are considered as a whole on the assumption that both stations belong to the same owner. Orienting the economy and security of the whole, a coordinated setting model of diversion standard for adjacent power stations is established.(2) In allusion to the diversity and conflict of the diversion decision makers, by defining the conflicting group and conflicting preference, interactive coordination model of diversion schemes is established with considering the mutual communication and feedback between the decision makers. Through the adaptive iteration algorithm, the negotiation process between decision makers is simulated. And by excavating the optimal information of the decision makers, the optimum diversion schemes is selected with consistet satisfactory.Furthermore, when the upstream power station is involved in the downstream river diversion with FFPR, the decision scope is extended from the the interior of the downstream to the alliance of the upstream and the downstream. Hence based on the method of multi-level game, the two-staged negotiation-game model of diversion standard is established. On the basis of calculating regulation benefit, the sharing strategy for regulation benefit is proposed. By expressing the risk preferences of decision makers with attribute weight, and by adopting the negotiation aggregation theory, the optimal combination of regulation pattern and diversion standard is given under consistent preference of the group.Engineering cases verified that the methods and models are feasible and applicable. On one hand, the study can offer technique supports for the estimation, transfer, and allocation of diversion risk under different effects of the upstream power station. On the other hand, the study also can offer method references for selecting diversion schemes under complex decision environment with multi-attribute, multi-agent and multi-level.