Research On The Application Of 2D Hydrodynamic-water Quality Couple Model Of Shallow Lake In The City

Urban shallow lake as an important part of urban construction, occupies an indispensable position in urban development.Because of its unique geographical environment and poor self-repair ability, the water environment of the urban shallow lake is very easy to be destroyed, and the water environment is deteriorating. Governance of urban shallow lake water environment and restore the ecological balance of the urban shallow lake is the important and difficult contents of 21 st century Lake Management and protection. Enhancing urban shallow lake water circulation, and improving urban water environment in shallow lakes can come true through leading clean water into the lake, and connecting rivers with lakes. In order to improve the water environment of urban shallow lakes and ensure the effectiveness of leading clean water into Lake, it takes to design different water diversion scheme. Through the establishment of reasonable two-dimensional hydrodynamic coupled water quality model of shallow lake in the city and accurately simulating the environment characteristics of lake water environment under different water transfer schemes.In order to in-depth study the process of urban shallow lake water movement and the diffusion of the pollutants, the complexity unstructured triangular grid was used when considering the shallow lake in the city boundary, then the programmes of “leading clean water into the lake” and connected water diversion scheme were designed combined with the actual situation of shallow lake in the city. through constructing reasonable two-dimensional hydrodynamic water quality coupling model of shallow lake in the city, the numerical simulation of the scheduling process of the water transfer project was realized.Then a comprehensive evaluation system was established, and the simulation results of different water transfer schemes were evaluated and analyzed to choose the optimal water transfer scheme.As an example, the paper takes the typical urban shallow lake East Lake in Wuhan, and the two-dimensional hydrodynamic water quality coupling model of urban shallow lake was built based on MIKE21 FM, combining with lacustrine landform condition, using unstructured grids which can be applied to complex boundaries. Themodel parameters were calibrated and verificated according to using the measured data of July 2006 and July 2007.And then,this paper designs three kinds of diversion programs on the background of Great East Lake Ecological Water Network, selects COD, TN, TP, the three major pollutant that affected the east lake as water quality indicators,simulates and analyzes the change of flow field and concentration field of water quality index with 31 days continuous water diversion in different schemes.Finally, this paper selects the comprehensive nutrition state index method and improved fuzzy comprehensive evaluation method to evaluate the simulation results,which is combined the qualitative analysis and the quantitative analysis, so as to obtain the advantages and disadvantages of three schemes.