| Plateau shallow lake as a pearl on the plateau, the people on the plateau is pregnanted by her, and she plays a vital role in the plateau's ecological environment. With the accelerated process of urbanization, discharge of large quantities of domestic sewage and industrial waste water, the ecological environment of shallow lake is worsening, governing the lake water environment is pressing. To carry out plateau lake water environment improvement plan is the guiding premise of the water environment governance and key, and the lakes of Water Environment Simulation is an important technical tool in the planning.In this paper, basing on the National Natural Science Foundation Project (50769001) called Plateau lake plants in wetland-water-sediment-the pollutant interaction mechanism and Public project of Ministry of Water Resources (201101042) named Protection and restoration to the water resources in city in plateau basin, exacerbating the current situation for the shallow lake pollution in the highland city, considering the wetland plants, sediments pollutants (nitrogen, phosphorus) and water conditions change, according to the hydrodynamic principle, the two-dimensional eco-hydrodynamic model of vertical average is established. The composite roughness of the wetlands is determined by the ecological river flume experiment in laboratory, and the rate of removal of pollutants (nitrogen and phosphorus), nitrogen and phosphorus sedimentation coefficient, sediment nitrogen and phosphorus release coefficient are gained by field wetlands experiment. Step-by-step hybrid method is adopted to solve the model equations, time is divided into the two half step. The former is used a modified method of characteristics, and the latter is applied the lumped mass finite element method to solve.Dianchi Lake is the object of the study in the paper. The artificial wetlands are built according to the Planning Framwork around Dianchi Lake, and the water in wetland is brung into Dianchi Lake water. The flow field and the pollutant(nitrogen and phosphorus) field ridden by wind are simulated under a number of siruatons, which stimulated for flow field and concentration field of existed water, expanding water and the total water after cropped plants in wetland, and the concentration field of water discharge within controlling index of national standard was also simulated by the model. The effects of wetland plant and expanding water on Dianchi lake's flow field and water quality are both analysed, and the effect water-up-to-standard release on water quality is analysed too. Analysis of contrast in each case, simulation results are obtained as follows. The local region of the flow field changed, when the original boundary conditions and wind students flow the local flow of Dianchi Lake are changed. The effect of ecological wetland construction on the Dianchi flow field occurs mainly in wetland areas, and which of other regions is less. Waters extended helps to increase the purification capacity of water-self. Eco-wetland can reduce lake pollution effectively. The inflow water-up-to-standard release into the Dianchi Lake and the construction of wetlands in the merger process will greatly reduce the pollution of lakes, and they play a significant role in water purification. The simulation result is a supporting role for the ecological construction of the Dianchi Lake. |
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