Abstract:

Changjiang Estuary is abundant in natual resource and has an obvious locational advantage,which make Changjiang Estuary an economic development frontier of Changjiang basin and even of the whole nation.The development of the city needs a lot of high quality raw water.Nowadays,70% of the water supply in Shanghai is from Changjiang Estuary.Changjiang Estuary is leading waterway of Changjiang basin,which is developed in shipping and convenient in transportation.With the increase of ships and boats in the sea area,it also results in an increase of collision incident and oil spill.Once the oil spill occurs,it will seriously affect the environment of Changjiang Estuary,the ecological environment and biodiversity of the sea area,as well as the water supply safety of Shanghai.So it is quite important to react at the very moment and take action properly as soon as the the oil spill occurs.First of all,based on the flexible mesh,a vertical 2D numerical model for average tidal flow of Changjiang Estuary and Hangzhou Bay was proposed in the paper.With a huge amount of validation of hydrodynamic force in Changjiang Estuary,the model was also vertified by the lastest observation data mainly conducted in the South Branch area.The data mainly included flow velocity,flow direction and water level.Secondly,the Spill Analysis（SA）Model of MIKE21 was provided with basic hydrodynamic data after the reliability of tidal flow model proved.Based on an oil spill particle trajectory with the system of EulerianLagrangian,a prediction model was established,which took the oil spill behavior including spread,transport and weathering as well as the endresult of oil spill in Changjiang Estuary into consideration.Finally,the model was used to simulate and predict the change of oil slick thickness and its spread path near the water intakings after the oil spill accidents of both the summer and winter spring tide in Changjiang estuary.The results shows that, affected by the alternative flood tide and ebb tide in Changjiang estuary,the oil slick moved downstream along the deep channel in terms of drift oscillation.In vetical,the thickness of oil slick became thin,also the oil slick was stretched gradually and formed a narrow oil belt,which resulted in an expansion of cover area of the oil slick.The spread path of oil slick was influenced mostly by the flood and ebb tide,on the other hand,wind force as well as the topography of Changjiang Estuary also played roles in the spread path.The summer oil spill had different influence on all the three reservoirs,while the oil spill in winter only posed a threat to the water intaking of Changjiang Estuary reservoir,and had no influence on the other two reserviors.The oil slick evaporation in summer was larger than that in winter,and evaporation of oil slick mainly happened in the first 16 hours after the oil spilling.The evaporation rate of oil slick was 34% in summer,larger than 31% in winter