Numerical Simulation On The Influence Of The Reclamation Project At Qiantang Estuary On The Hydrodynamics And Water Environment Of Hangzhou Bay

Based on MIKE software platform, a large-scale three-dimensional hydrodynamic model of East China Sea was constructed. It covered the Hangzhou Bay, the Yangtze River estuary and adjacent waters. Depending on the large-scale model of East China Sea, a small-scale coupling model of hydrodynamic and water quality for Hangzhou Bay was built. Based on the numerical simulation of Hangzhou Bay, the influence on flow field, salinity field and water quality of Hangzhou Bay has been studied. Main contents of this paper are as follows:(1) Firstly, the domestic and foreign research progress of hydrodynamics, water quality model are introduced, as well as the research of the reclamation projects.(2) The basic equations and numerical methods of MIKE model are introduced in detail.(3) A large-scale three-dimensional hydrodynamic model of East China Sea was constructed. It was verified with the tide, current, temperature and salinity. The results indicate that the calculated values fit well with the actual values. The model can simulate the hydrodynamic, temperature and salinity of Hangzhou Bay and its adjacent waters accurately.(4) Draw flow field pattern and the Plane distribution of salinity by the large-scale three-dimensional model of East China Sea for analysis. The results show that the trend of Hangzhou Bay is reversing current. Ebb current flows from west to east, the flow rate increases from the top to bay. The flow of flood current is from east to west, the flow rate on the top is greater than the flow rate in the mouth of the bay. The distribution of salinity increases from the top of the bay to the mouth of the bay. And influenced by the freshwater from the Yangtze River, the salinity on the north is lower than the salinity on the south. Affected by the tidal mixing, the salinity of Hangzhou Bay is uniform on the longitudinal distribution. There is no significant difference of salinity between surface and bottom. Affected by flood and dry seasons of the runoff, the salinity in winter is higher than that in summer,(4) Depending on the large-scale model of East China Sea, a small-scale coupling model of hydrodynamic and water quality for Hangzhou Bay was built. The model was validated by the actual measured concentration of DIN, DIP and Chl. Based on the numerical simulation of Hangzhou Bay, the influence of the reclamation project on flow field, salinity field and water quality of Hangzhou Bay has been studied. The study shows that the project did not change the flow field. The project only affects its adjoining waters, it increase the speed of water flow in the estuary. The project can also reduce the salinity of Hangzhou Bay, it retreated the salinity contour, and decreased the intensity of saltwater intrusion. After the project, the concentration of DIN and Chl has a certain increase. And after the reclamation project the contamination from Qiantang River will transport farther, it will exacerbate water pollution in the Hangzhou Bay.