Simulation Analysis Of Jiyun Water Environment And Restoration Measures

Jiyun River located north of Haihe River Basin, and its basic function is discharging floods. Owning to continued drought in recent years, there is almost no upstream flow discharging. And untreated state-owned and urban waste water were discharged combined with river bed contaminated for years because of seawater flow backward caused by disrepair gates, which lead to water salinization and deterioration. Along with the economic and social development, environment, ecology and landscape needs, the current water quality conditions can’t meet local demand. So this paper studied changes in water quality of Jiyun River, and conducted a pollution survey to find the major pollution factors, then established a water quantity and quality coupled mathematical model to simulate the swage interception measures according to plans made by Tianjin government, calculating, analyzing and comparing the effects of three pollution reduction measures to provide a basis for making the final plans and reasonable prediction.Tianjin Water Environment Monitoring Center has six monitoring sections, which are Jiuwangzhuang, Xin’anzhen, Zhuangtouwo, Jiangwakou, Lutai Bridge ,Jiyun Gates and monitors four times a year. Based on the analysis of monitoring results, we defined the major pollution factor in Jiyun River are chloride, sulfate, COD, total phosphorus (TP) and total nitrogen (TN).Establishing a hydrodynamic model based on one-dimensional Saint-Venant equations and validating it by water level and flow data of Jiuwangzhuang, Zhangtouwo and Jiyun Gates, and we found that simulation values and measured values matched each other well, the model meeting the requirements. Establishing a water quality model based on convection-diffusion equation and coupled with hydrodynamic model by flow. Than validating the hydrodynamic and water quality coupling model by water quality data monitored by Water Environment Monitor Center which has satisfactory results.After learning the theory of ecological water demand, we computed it with Tennant, monthly guarantee rate and the monthly minimum method and ultimately determined the ecological water demand in Jiyun River is 263 million m3. According to the plan that Jiyun will reach theⅤclass of surface water standards, COD, TP and TN’s environmental capacity of 2008-2010 were calculated. After that, pollution load reductions which should be undertaken by every outfall can be obstained by calculating their contribution rate. The more the outfall loads, the more the outfall discharge. Thus we can guess the river nearby them has poor water environment and should be protected immediately.In order to improve the water environment in Jiyun River, project measures (to built constructions of sewage treatments), scheduling measures (to water pollution) and ecological measures (to built artificial wetlands) were planned. Then analyzing and comparing the effects of three pollution reduction measures to provide a basis for making the final plans.