The Water Circulation System Of Large Slow Urban Landscape Water And Water Quality Simulation

Along with the development of economy and the acceleration of urbanization, for the urban landscape water quality, people requestsed more and more strictly. At present, the biggest problem of the landscape water quality was the water eutrophication, especially the urban landscape lake. At first, the land had no water to import and export, most of the lake was the closed water. The water had poor liquidity, which was bad for the dilution and spread of the pollutant, and the self-purification ability was bad. And then, the landscape lake was in the downtown, which was severely affected by the human activities. For the landscape lake human destructive force was more than the water self-purification.In this paper, we analyzed one of the landscape lake in TianJin. Through the sampling points, monitoring the landscape water quality, and comprehensively considering the lake structure characteristics, we mastered the possibility of eutrophication occuring of the landscape lake. And we evaluated the eutrophication level using Comprehensive Nutrition State Index Method, the lake in the mesotropher state, especially the COD in the highest state and the TP was lowest. The content of phosphorus was the limiting factors of algal growing. At last we analyzed the experimental results of the circulatory demonstrationproject in the landscape lake, and we knew the operation of circulation system could effectively improve the water quality.And then, in this artice we analyzed the influence of the hydrodynamic conditions to the transformation and attenuation of the pollutants in the water. And we established the hydraulic mathematical model to corresponding the landscape lake and choiced the proper solving way. In order to improve the hydrodynamic conditions in the landscape lake, we designed to build circulatory river along the lake and drive the water to flow, so we could change the closed water to flowing. And we also programed the simulation program, which integrated the computational fluid dynamics analysis. We operated the program and got the best combination of inlet and outlet and the inlet velocity under certain cycle period. Then we simulated the flow characteristics of different cycle period and different inflow pattern. The result showed that if the water inleted the lake from different direction the cost might be high but the mean velocity was higher, the area of the stagnation zone was smaller and the velocity distribution was more equably. At last, the mike21 water quality simulation software was used to simulate the content of COD/NH₃-N/TN/TP in the lake. We analyzed the error between the simulation values and the actual monitoring values, it illustrated the mike21 was vaible and effective. On the base of flow simulation results, the water quality in July was simulated, different conditions was simulated inculding remain state, water circulation, adding reclaimed water and so on. The content of COD/NH₃-N/TN/TP in the lake was showed, and according to the simulated result the measures to improve and keep the water quality was suggested.