Detailed Water Allocation Of Urban Complex Water Utilization System

As the center of human activities, cities are not only the high-concentrated area of population and productivity, but also the place where water demand is biggest, water problem are centralized and water management is most complex. With the rapid development of urbanization and industrialization, the water supply sources increased, water cycle routes spread, water cycle structure became more complex and finally form a new and much more complex water system. The diversification of water supply sources, water use structure and the complexity of water supply of water plants make the harmonizing of water supply sources, the guaranteeing of water use, the connection between water plants and water suppliers becoming the outstanding issues which badly and urgently need new solutions. Traditional urban water resource allocation does not consider the water plant in the artificial water cycle, which is the key link of delivering water resource to water users, and finally results in "spatial water distribution" or so called "virtual water distribution". Besides, it does not realize the characteristics of features like water supply sources and water users that always change under the rapid urbanization.Therefore, based on the water cycle theory and optional allocation theories, the water use, an artificial part of the complex city water resources system were analyzed by building a water source-water plant-water users integrated subtle water allocation model, which focus on the changes of water supply sources, water use structure and water plant supplying characteristics in the city water resources system, to research the problems in the procedure of water optional allocation under the background of numerous water sources and considering the connection of water plants, water resource and users. This article selects the Tianjin New Coastal District (NCD), located in the center of Beijing-Tianjin-Hebei urban agglomeration and Bohai economic zone and in the intersection of "One Belt and One Road", as the research area and NCD, in a large urban agglomerations, also has a typical conflict between water demand and supply. And the following results are obtained in this study:(1) The complex urban water resources systems was analyzed. Based on the artificial water cycle in urban water systems, it analyzed the change of water supply and water use structure and water plant types under the development of urbanization. Furthermore, the water supply system, water users and water plants were refined, and the function and running characteristic of water plants were explored to lay the foundation for urban water resource fine allocation.(2)A urban water resources fine allocation model was established. The concept and principle and the approach of urban water resources allocation was arose, and the hierarchical structure of urban water source-water plant-water users allocation system were analyzed, so that the water cycle paths and the relationship between water supply and demand were interpreted. Then the urban water resource fine allocation model was established, with the largest comprehensive benefit of the society, economic and hydraulic engineering considered as the objective function. To solve a multi-objective problem, the model used a multi-objective genetic algorithm, so that the process of artificial water cycle could be reflected through the model of optimal allocation.(3)Tianjin New Coastal District is chosen as the research object. According to the distribution pattern in different levels of water supply sources and water users in NCD, the network chart generalization was painted accordingly. After the calculation based on water supply balance equation, minimum of water shortage, the maximum of economic benefits were figured out, with the project optimal as the objective function, and the recommendation plan of the period from 2020 to 2030 were gained by the multi-objective genetic algorithm.(4) The future allocation pattern of Water resource in New Coastal District was worked out. According to recommended allocation plan, in the future, the transferred water will be the main and first-chosen water source, followed by the desalination and reclaimed water, and the groundwater decreases its supply amount gradually. The transferred water is also the main source of domestic and industrial water use, while the desalination seawater mainly supply to industries and part of domestic users, and the reclaimed water only used as ecologically water.(5)The precise connection plan within sources, plants and users was proposed. By calculating the remaining supply capacity of water plants, this article presents suggestions: ①in 2020, the water plants supply scale could meet the demand, but several small waterworks need to adjust supply amount to ensure the safety, such as Nangang Water Transport And Distribution Centre, Yixi Water Plant, and the surplus waterworks, like Dagang Water Plant, can be replaced. ②in the 2030, for the existing water plants’ supply capacity cannot satisfied the increasing demand, it is necessary to expand the old waterworks or build new waterworks to guarantee the safety of urban water supply.