Numerical Study On The Character Of Ecological Dynamics Of Large Shallow Lakes

Lake Taihu, which is the third largest lake in China, belonging to shallow lake. Because of its small flow, small velocity, closeness, long periodical time of water replacement and serious contamination, the self-purification capacity of Taihu is so weak. In recent years, Taihu confront a serious problem of eutrophication. According to the existing research, the excessive growth of phytoplankton is the straight source of eutrophication, and that nitrogen and phosphorus are main nutrients of phytoplankton. As for shallow lake, sediment release is also a important influencing factor not allow to ignore. Based on the previous studies, the following researches were carried out in this paper.According to the nitrogen cycle, phosphorus cycle, dissolved oxygen balance and phytoplankton kinetics theory in WASP5 model, a two-dimensional flow-pollutants coupled model of shallow lakes was developed on the basis of RBFVM-2D model in this paper, and finite volume method and Riemann approximate solver were used to solve the model equation.Use the model to simulate the current field and the concentration field of TN,TP, DO,PHYT of Taihu. In order to analyse the influences of wind and sediment on current field and pollutant concentration field, four different modes were considered, including considering no wind and no sediment, considering wind only, considering sediment only, and considering both wind and sediment. Based on the simulation result, the relationship of current field and pollutant concentration field with algae bloom in Taihu was analysed. Through the verification of the model, we can see that the two-dimensional flow-pollutants coupled model developed in this paper has high simulation precision, it can well simulate the current field and the pollutant concentration field of Taihu.