Hydrodynamics And Water Quality Modeling At The Great Donghu Lake

With rapid urbanization process and economic development, lakes around the cities are seriously polluted. As a typical large shallow lake at the center of city, the water pollution issue of the Donghu Lake has exacerbated, and becomes extremely urgent to be controled. For pollution control, all lakes are connented together to form a lake network(the Great Donghu Lake Network) to facilitate its hydrodynamics. In order to improve water quality conditions, water from the Yangtze River can be drained into the lake through the engineering program of the Great Donghu Lake network.The Great Donghu Lake network is an open and complex system, therefore, it is significant to undertake approaches on two-dimension shallow water modeling and water quality modeling to analyze the characteristics of hydrodynamic movements and pollutant distributions. In this thesis, an integrated conceptual water network model is built for the Great Donghu Lake network as a whole by using GIS technology. The corresponding two-dimensional numerical model for simulating hydrodynamics and water qualities is established. Then the model parameters are calibrated by using literature data and observation data. The verification results indicated that the developed model can be well used for futher hydrodynamics and water quality simulation at the Great Donghu Lake.Based on the modeling simulation, scenarios under different conditions(such as drainage schemes and operation modes for canals and water gates, point source and non-point source pollution loadings, and wind conditions) are designed and simulated. Compared with simulation results of different scenarios, the variation of hydrodynamic characteristics and pollution distrubutions can be analyzed. The results indicate that measures of draining water from the Yangtze River and controlling pollution source discharge can effectively improve the water quality conditions in lake areas. And reasonable operation schemes and optimized operation modes for canals and water gates can improve water environment and control point and non-point sources pollution effectively. However, the hydrodynamic improvement for the lake areas where are far away from intakes is not obvious, and the pollutions of TN and TP are still serious. Therefore, it should be considered that the water inflow operation scenarios and pollution reduction targets so as to further improve the partial hydrodynamic conditions in lake areas.