| Eastern Hengsha shoal which lies in the east of Hengsha Island in Yangtze River Estuary covers an area of 460km2. And it’s important mud flat resource. Nowadays, since land shortage restricts the development of Shanghai city, reclamation in Yangtze River Estuary is very necessary. Reclamation of Eastern Hengsha shoal, constructed since 2003, will form land of about 2 million mu. What’s more, it will ease the land burden of Shanghai and benefits the economic and society. However, it will have profund influence on nearby water environment. So it is of great significance in theory and reality to research the influence of reclamation of Eastern Hengsha shoal on nearby water environment. Based on MIKE, numerical simulation which includes tide level, current, temperature, salinity and water quality will be applied to Yangtze River Estuary. Research on the factors of diffusion and transportation of pollutants will be carried out based on this model. At last, further research will be applied to the water environment influence of reclamation of Eastern Hengsha shoal. Main contents of this paper are as follows:(1) Research progress on offshore tide,salinity and water quality is stated in detail, and hydrologic conditions in Yangtze River Estuary are introduced systematically.(2) Model equations, time integration and spatial dissociation are introduced in detail.(3) On the research background of Yangtze River Estuary, Hangzhou Bay and nearby water area, three dimensional baroclinic math model is established to make numerical simulation on tide level, current, temperature, salinity and water quality.(4) Focusing on sewage discharged by one of the main drain outlets(shidongkou) in Shanghai, Lagrange tracing particle method will be used to research the influence factors of diffusion and transportation of discharged pollutants particles. The research indicates that: with respect to wind, it will amplify the area polluted by pollutants particles in Yangtze River Estuary and impair pollutants on pollutanting south shoreline of Yangtze river Estuary and Hangzhou Bay. With respect to heat flux, it weakens the diffusion of surface pollutants particles in Yangtze River Estuary and strengthens the transportation of middle and bottom pollutants particles in Hangzhou Bay. In contrast with other factors, heat flux has relatively little influence on the diffusion and transportation of pollutants particles. With respect to temperature and salinity, their baroclinic effects will make the diffusion area polluted by pollutants particles smaller and make the particles transport further towards Hangzhou Bay. As a result, it will worsen the pollution of Hangzhou Bay. With respect to tide, M2 tide will impair the transportation and diffusion of pollutants particles towards Hangzhou Bay, and it has greater influence on surface and middle layer.(5) Analysis on the influence of reclamation of Eastern Hengsha shoal in water environment is carried out. It includes tide level, current speed, salinity, water quality. The research shows that:after the reclamation, current speed in nearby water changes obviously, current speed in Northern Channel and North Harbor increase, as a result, their river beds are scoured, while current speed in Southern Channel decreases and bottom beds are deposited; at the same time, salinity in nearby water except South Harbor reduces generally, which indicates that reclamation projects impair the salinity intrusion;based on the water quality index which including NH3-N and DO to make water quality evaluation on the reclamation project, the results indicate that water quality deterioration in South Harobor and north water area of Eastern Hengsha shoal gets bad because of reclamation, especially the bottom area, besides, the reclamation project will worsen the pollution caused by pollutants particles in drain outlet to south shoreline and Hangzhou Bay... |
PDF Full Text Request