Reliability-based Optimization Of Water Distribution Systems

Along with the social economic development and the people living standard improvement, reliability analysis and reasonable design of the municipal water distribution systems is becoming more and more important.In this paper, based on the summary of research results of the previous study, the indicators of hydraulic reliability and the water quality reliability of municipal water distribution systems has been chosen and the corresponding computational model has also been set up. And then, according to the characteristics of the water distribution systems, a multi-objective optimization model, which is based on the hydraulic and water quality information entropy, has been established. Finally, the optimization model has been successfully applied into the optimization of practical large-scale municipal water distribution systems.First of all, the definition, establishment and solution of the hydraulic model and water quality model of municipal water distribution systems have been analyzed. The function and the secondary development of hydraulic analysis software EPANET are introduced. Also, based on the water quality monitoring data of a water distribution systems in one campus, the partial least squares method has been used to establish the total iron and turbidity prediction model. The comparation of the monitoring data and the predicting results shows that the partial least squares water quality prediction model has good predictive effect, and it is more adaptable in solving the multiple regression problems which is always ill-solved by the ordinary regression method.Secondly, after the analysis and synthesis of the previous reliability research of municipal water distribution systems, in this paper, the hydraulic and water quality reliability model as well as the hydraulic and water quality information entropy model are established. In the hydraulic and water quality reliability model, the ratio of available water supply quantity and the normal water demand of nodes is used to calculate the hydraulic reliability, and the standard-reaching rate of water quality of nodes is used to calculate the water quality reliability. Also, based on the information entropy principle which was introduced by Shannon, the hydraulic and water quality information entropy models are established. According to the entropy models, the reliability of the municipal water distribution systems can be indicated by the uniformity of the water supply and the water quality distribution.Thirdly, a small municipal water distribution system has been taken as the example to simulate the reliability models which has been established in this study. The results of the analysis indicate that the reliability models not only can be well used in calculating the reliability of municipal water distribution system, but also it can be proved that the hydraulic and water quality information entropy model can be used as the alternative model of the hydraulic and water quality simulation model, and it can be better applied to the optimization design study of the complex municipal water distribution systems.Finally, based on the economic optimization and the maximum information entropy, the multi-objective optimization model of municipal water distribution systems is established. Then a practical large scale municipal water distribution systems in the administrative region of northern China is taken as the object, the MATLAB GATools is chosen to solve the multi-objective model, and the MATLAB external program interface function is used to call the EPANET dynamic link library. Also, according to the characteristics of the water distribution systems, the constraints have been well transferred to be more adaptable to the GATools. The optimization results indicate that the multi-objective model can be well used in the optimization of the municipal water distribution systems, it can not only reduce the investment but also increase the reliability of the municipal water distribution systems.