Numerical Simulation On Hydrodynamic And Water Quality Effects Of Reclamation In Bohai Bay And Pearl River Estuary

Bohai Bay is located in the western part of the Bohai Sea,near the city of Tianjin and the provinces of Hebei and Shandong in China.Thus,it is an important political,economic,and cultural centre in the northern coastal area of the country.In recent years,with rapid economic development,the rise of reclamation activities has resulted in significant changes in the Bohai Bay shoreline.The Pearl River estuary area is the leading of economic and social development in Guangdong Province,and is the most densely populated and most economically developed urban agglomeration area in Guangdong Province.Since the reform and opening up,the Pearl River Delta region has witnessed rapid economic development and frequent human activities.In particular,activities such as the coastal reclamation,bridge,port construction have caused the Pearl River estuary coastline to continuously advance to the sea,and the type and length of the coastline have undergone great changes.However,while bringing great economic benefits,the problems that arise are gradually emerging.A series of problems are urgently needed for us to solve,such as the sharp decline of the bay area,the weakening of the properties of the Gulf,the destruction of the natural landscape of the coast,the degradation of the ecosystem functions,the resource use conflicts caused by reclamation of land,and the intensification of conflicts between industries.This study simulates the hydrodynamics and water quality of Bohai Bay and Pearl River Estuary by using MIKE and FVCOM models.And uses a well-validated model to systematically analyze the influence of shoreline topography change and coastline variations of the reclamation project on the hydrodynamics and water quality in Bohai Bay and Pearl River Estuary.The results of this study can contribute to a decision basis for engineering design,environmental protection,and pollutant emission control.The Bohai Bay hydrodynamic and water quality model is established using the MIKE and FVCOM numerical models,respectively,and the results are well fitted with the measured data.The study shows that reclamation projects weaken the residual current and generate a counter-clockwise circulation south of Huanghua Port,thereby resulting in weak water exchange capacity and low pollutant-diffusing capacity.Reclamation projects reduce the area of Bohai Bay,resulting in a smaller tidal prism and further weakening the water exchange capacity.This situation is not conducive to the diffusion of pollutants,and may lead to increased water pollution in the bay.Reclamation projects hinder the spread of runoff,weaken the dilution effect of the river on seawater,and block the spread of coastal residual current,thereby resulting in increased salinity near the reclamation area.Reclamation projects lead to an increase in PO4-P concentration and decrease in DIN concentration.The value of N/P near the project decreases,thereby weakening the phosphorus-limited effect.But the scope of impact is small and there is almost no change away from the reclamation area.The Pearl River Estuary hydrodynamic and storm surge model is established using the MIKE and FVCOM numerical models,respectively,and the results are well fitted with the measured data.The study shows that the reclamation projects have a great influence on the tidal velocity and direction,especially in some areas where narrow waterways formed.The reclamation projects impeded the spread of runoff,resulting in increased salinity.It is necessary to increase the prevention of saline intrusion in this area.The reclamation projects also have reduced the significant wave height in the nearby sea area.It has a positive effect on reducing storm surge disasters.But the scope of impact is small and there is almost no change away from the reclamation area.