Model Based On Efdc Shenzhen Bay Water Environment Simulation And Prediction

As the final destination of the surface water pollutants, water pollution of rivers and bays are difficult to be controlled. Because Shenzhen bay belongs to Shenzhen and Hong Kong, the water environment pollution increasing in the bay brings serious adverse environmental impact to the two cities. It has been concerned widely about water pollution, water quality improvement and ecological protection of Shenzhen bay by Shenzhen and Hong Kong administrations. Therefore, the numerical model of water environment in Shenzhen bay would play an important role in the water environment management, water quality assessment, the water pollution control measures and sudden water pollution accidents of emergency countermeasures of Shenzhen and Hong Kong.According to the particular situation of Shenzhen bay, based on EFDC (Environmental Fluid Dynamics Code) model, which has been recommended by USEPA, and the research results of the pollutant loads of Shenzhen bay, the numerical model of water environment in Shenzhen bay had been established in this thesis. Specifically speaking, the studies on the water environment in Shenzhen bay are carried out as follows:Firstly, according to the many pollution sources and complex boundary conditions in Shenzhen bay basin, the Shenzhen bay water environment information management system has been established, which based on EFDC model. The simulation results of hydrodynamic process and water quality indexes have been certified to be consistent with the observation data. So the model can be used for the analysis and prediction of the water environmental change in Shenzhen bay. This system can not only be used to simulate and analyze the hydrodynamic process and migration and distribution characteristics of main pollutants in Shenzhen bay basin, but also be used in water environment management, such as visualizing for pollution distribution (there are 52 point pollution sources in Shenzhen bay basin) and the characteristics of pollutants concentration, etc. Secondly, the water quality in Shenzhen bay in future has been predicted by the model, including normal condition and sudden pollution incident condition.According to the forecast outcome of pollution load in Shenzhen bay in future, the results of simulation and prediction about the water quality in normal condition show that the water quality of inner Shenzhen bay will be gradually improved, when the pollution control measures and reduction plans would been taken. Especially in 2005 to 2010, the average concentration of BOD5 and NH4-N will reduce 37.53%～41.82% and 37.94%～45.44%. At the same time, the water quality of outer Shenzhen bay will be inconspicuously improved.The results of simulation and prediction about the water quality under sudden pollution accident condition, and analysis about the impact of the accident and effect of emergency measures show that the model could provide effective scientific support for decision makers making the optimum emergency measures for social economic. It could be to avoid the subjective factors of decision makers in those accidents, so that the ability of response to sudden pollution incident in Shenzhen bay could be improved.Thirdly, based on the Maximum Daily Total method, the TMDL plan specific route of water quality improvement in the Shenzhen bay has been designed. It has calculated out the values of total maximum daily load of BOD5(18 t/d),TP(1.3 t/d) and TN(0.15 t/d) when it meets up with the III standard of sea water quality standards (GB3097-1997), and determined the reduce rate of pollution load of rivers basins in Shenzhen bay basin.Compared to the current pollution loads of water quality indexes in the Shenzhen bay, whether in the rainy season or dry season, nonpoint source or point source, the average of reduction rate of pollution load could come up to 70%. It shows that the task of pollution loads reduction is very difficult.