Study On Setting-up And Simulation Of Urban Water System Model Based On Risk Transmission

Water resource is a kind of indispensable strategic resources and natural resources for city development, and water environment is the base of ecological system. Under the circumstance of accelerating urbanization, the balance between water resources, society and economy becomes more and more important. In this paper, Tianjin was chosen as the representative of coastal cities in North China. Considering the risk in Urban Water System(UWS), system dynamic(SD) was applied to research UWS simulation and risk transmission.Firstly, UWS was defined. According to the statistical data, the conditions of social and economic developments were analyzed, as well as the development and utilization of water resource. And then, the idea of risk and risk transmission were brought into this paper. After the summary of the present problems of Tianjin UWS, the composition and hierarchical structure of Tianjin UWS were analyzed and confirmed from a macroscopic view.Secondly, UWS inner risks, water yield risk and water quality risk were defined. According to the structure and function relationships among different UWS subsystems, the transmission condition and structure of UWS inner risks were analyzed, as well as the transmission mechanism.Thirdly, according to risk and water flow direction, variables in each subsystem were determined. Also, the transmission and feedbacks of UWS inner risks in each subsystem were analyzed. By using Vensim, the SD flow diagram was established. And the model equations were compiled in DYNAMO programming language. Thus, the risk transmission and function mode among different subsystems were analyzed, and the dynamic relationships among different variables were specified. After three kinds of model tests, SD model of Tianjin UWS which is based on risk transmission was finally established. And this SD model was proved to be reflecting the process of risk transmission and the operation law of UWS.Fourthly, the routine situation of Tianjin UWS was simulated by using the SD model established in this paper. And the effects of inner risks on the development of UWS were analyzed. According to the parameter sensitivity analysis, the parameters which have important effects on UWS were found out, as well as the parameters on UWS inner risks.Finally, the suggestions of improving the structure and function of the present Tianjin UWS were summed up based on controlling the risk transmission chain. This paper can provide some scientific reference for the sustainable development of UWS and the secure design of water environment.