Design And Control For The Limited Water Level Of Reservoirs In The Flood Season Based On Flood Prevention Forecast Operation

Not only do severe flood disasters happen frequently, but also shortage of water resources and deterioration of water environment have been becoming worse in china. Faced with a series of water problems, many methods have been studied to make safely use of flood resources. One of them is to design and control scientifically the limited water level of reservoirs in the flood season. In the dissertation, as for some problems of reservoir operation for flood resources, the research has been done on design and control the limited water level in the flood season using optimal reservoir operation method, fuzzy optimizing theory, information entropy theory and genetic algorithms etc. The aspects focus on flood prevention forecast operation manner for both single reservoir and cascade reservoirs, risk analysis for flood prevention forecast operation manner, controlling dynamically the limited water level of reservoirs in the flood season and multi-objective decision making for reservoir operation. The research mainly includes the following parts:(1) Flood prevention risk adopting flood control forecast operation manner at various limited water level of reservoirs in the flood season is studied. Firstly, flood forecast error scope is divided into several intervals. And the definition and the calculation method of every forecast error interval are presented on the basis of analyzing the influence of flood forecast error on flood control operation. Contrasting the difference of the risk between flood prevention forecast operation manners and planning, the definition of overdesign risk rate of flood prevention forecast operation manner is given and the corresponding calculation method is established. Taken Baiguishan reservoir as an example, the feasibility and practicability of the proposed method is testified.(2) As for the randomicity of flood forecast error ignored in determining flood prevention forecast operation manner, risk analysis is applied to drawing up flood control forecast operation rule. Moreover, a method of selecting a satisfied flood control forecast operation rule from several feasible flood control forecast operation rules is proposed. Subsequently, the method is used to determining the flood prevention forecast operation rules of Yuqiao reservoir and Zhaopingtai reservoir. And the key conditions of elevating the limited water level of reservoirs in the flood season by flood control forecast operation manner are discussed. (3) An optimization method has been studied to design flood prevention forecast operation manner for cascade reservoirs by combining optimal operation method and planning operation manner. Firstly, to meet the given operational objective, optimization method is be taken to search the optimal discharge manner for different frequency design floods of cascade reservoirs and the characteristic of the optimal discharge flow been concluded. Second, the potential capacity of each reservoir and the optimal discharge process are considered to choose forecast assessment indexes, and the ideal joint forecast operation rule is made without taking into account flood forecast errors. Finally, based on this ideal joint flood prevention forecast operation rule, a practical flood prevention joint forecast operation rule is further made with forecast errors being considered.(4) An approach is proposed to controlling dynamically the limited water level of reservoirs in the flood season. The amount of inflow is estimated by flow forecast in flood recession stage. And different factors are taken into account to foresee the pre-storage and pre-discharge capacity, such as construction condition, precipitation and flood disaster etc. The subsequent starting operation level can be determined with short rain forecast information to make sure the safety of the dam and downstream. Based on the above, a model is designed for controlling dynamically the limited water level of reservoirs in the flood season. And the risk analysis method is given by using probabilistic combination.(5) Aim at the difficulty combining experience weight with mathematic weight, entropy weight method is introduced to determine mathematic weight. And the multi-objective fuzzy comprehensive judging method is presented, in which mathematic weight is linear combined with experience weight. Furthermore, an improvement is made to solve the problem exist in the current entropy weight calculation, which is inconsistent between entropy value and entropy weight. Finally, a sensitivity analysis method of experience weight is discussed to determine the scope of experience weight, in which experience weight can influence the schemes sorting.Finally, the conclusions are draw and the problems to be further studied are discussed.