Optimization Study On Planning Of Regional Water Distribution System

With the development of social and economic, upgrading of urbanization level and the formation of regional economic, water supply system, as an important infrastructure, must be carried out with reformation for the service of high-speed economic development and providing safe potable water. Regional water supply management pattern is the trend in the process of the reformation.Based on analyzing the domestic and foreign research results, a complete optimization scheme for the planning of regional water distribution system was presented in this paper. It has significant economic and social benefits for exploring the method of unified planning, rational layout and searching for economic diameter in the purpose of cost saving, energy conservation, ground water protecting and water quality securing.Firstly, a preliminary research was carried out for reliability of water distribution systems, and then the paper proposed the concept of hydraulic reliability and entropy reliability of water distribution systems. The hydraulic reliability was defined as the ratio of the available flow to the demand flow. With introducing of information entropy theory, the network entropy was chosen as a surrogate measurement of reliability of water distribution systems to indicate the degree of uniformity of water flow in the pipe networks. The model of hydraulic and entropy reliability, as well as the computer program, were presented in the paper.Secondly, the problem of layout for the transmission and connecting mains in regional water distribution systems was transformed to the problem of shortest path with empowered value in Graph Theory. Dijkstra algorithm was adopted for solving the model. Limits of flow method was used to determine the economic diameters.Thirdly, a model for diameter optimization of regional water distribution systems was presented with the objectives of minimal investment and operation costs, and maximum hydraulic and entropy reliability of water distribution systems. The shuffled frog-leap algorithm (SFLA) was applied to solve the model. Based on the characteristics of the model, the method of encoding and decoding of decision variable was proposed, also two improvement measures was applied to SFLA for improving efficiency. Finally, the optimization planning theory proposed in the paper was applied on the planning of regional water distribution systems in Tianjin City. Hydraulics simulation and economic calculation were carried out for the optimized planning scheme, also water supply guarantee rate and security level of potable water were assessed according to a failure scenario. The result showed that the optimized planning scheme has a high reliability level of ensuring water quantity and pressure for the clients.