Numerical Simulation Of The Effects Of The Reclamation In Hengsha Shoal On Hydrodynamic Environment

In order to accelerate the construction of Shanghai international shipping center,and to adapt to the trend of more large-scale ships and more deep-water berths in the world shipping industry,it is necessary for Shanghai to continue to develop the Yangshan port,and to open up the new deep-water channel and port in Yangtze Estuary at the same time.By a series of deep-going studies,Hengsha Shoal was proposed to be the best place to open a new port.In order to meet the land demand of port construction,the reclamation is the most effective way.However,the implementation of project can change the hydrodynamic conditions locally,and may cause a series of ecological problems,like the channel siltation,increased saltwater intrusion and deterioration of water quality.Thus,before the implementation of the reclamation.Studying its effects on the surrounding hydrodynamic environment has the highly important practical significances.Based on the DHI MIKE3 model,this paper establishes a large-scale three-dimensional baroclinic numerical model in Yangtze Estuary,Hangzhou Bay and surrounding water area which includes the HD?Hydrodynamic Module?and TS?Temperature and Salinity Module?.With the measurements of 10 stations for tidal level,6 stations for tidal flow,2 stations for temperature and 6 stations for salinity,the parameters of hydrodynamics,temperature and salinity are calibrated.Based on the large-scale numerical model,a small-scale three-dimensional baroclinic numerical model in Yangtze Estuary,including HD,TS and Ecolab Module,is established.By comparing the simulated distributions with observed distributions of Chl-a,DIN and PO₄^3-respectively,the parameters of water quality are determined.Based on the small-scale three-dimensional baroclinic numerical model in Yangtze Estuary,this paper analyzes the effects of the Hengsha reclamation on surrounding water area from five perspectives,namely tidal level,tidal flow,salinity,water quality and particle transport.By the comparisons before and after the project,the conclusions are listed as follows: ? The tidal level changes little,and tidal range generally decreases;? Regarding to peak velocity during flood tide,it increases in the lower reach of Northern Area,South Channel,North Passage,the upper and middle reaches of South Passage,but declines in the North Channel,upper and middle reaches of Northern Area,lower reach of South Passage and Eastern Area.The largest increasing extent,up to more than 20%,occurs in the downstream of Northern Area,and the largest decreasing extent,up to more than 45%,occurs in the southern part of Eastern Area.? Regarding to peak velocity during ebb tide,it increases in the North Channel,Northern Area,North Passage and South Passage,but declines in the South Channel and Eastern Area.The largest increasing extent,up to more than 20%,occurs in the downstream of North Passage,and the largest decreasing extent,up to more than 60%,occurs in the southern part of Eastern Area.? Regarding to maximum salinity during flood tide,it increases slightly in the downstream of South Passage,but decreases in other waters,especially in the upper and middle reaches of the North Passage.? Regarding to minimum salinity during ebb tide,it rises in the North Channel,South Channel,especially in their upper reaches,but falls in other waters,especially in the middle reach of the North Passage.? Regarding to Chl-a,the concentration generally increases in surrounding waters,and from the project the closer the distance is,the greater the increase is,especially in the Eastern Area.? Regarding to DIN and PO₄^3-,their concentrations decline slightly in the North Channel,upper and middle reaches of South Channel and South Passage,but increase greatly in the Northern Area,lower reach of South Channel,North Passage and Eastern Area,and from the project the closer the distance is,the greater the increase is.The largest increasing extents of the concentration of DIN and PO₄^3-occur in the Eastern Area and middle reach of the North Passage respectively.