| As an economic developed city with high population, Shanghai requires lots of high-quality raw water. The main source of water supplied to Shanghai is from Huangpu river before2010. Due to the low quantity and poor quality raw water, Shanghai has been a water quality-induced water shortage city. It is necessary to fetch water from Changjiang river estuary to solve water problem of Shanghai radically. Water in Changjiang river estuary has a large volume and high quantity. Now Chenhang Reservoir and Qingcaosha Reservoir, located on the South Banch and Changxing island, have already relieved the water shortage situation in Shanghai. Coupled with Dongfengxisha Reservoir being built, the structure of water source in Shanghai has been greatly changes, and the heart of supplying raw water has been transferred from Huangpu river to the Changjiang river estuary. Because the water source regions are located in the main waterway, the traffic is heavy and associates oil spill emergencies. To ensure the safety of water quality near the water source regions, it is very important to analyze the influence of accident-induced oil film on the water source regions in Shanghai.Based on the improved ECOM-si3-D numerical model, we considered the stochastic diffusion, evaporation and water entry of oil particles by particle-tracing technique, and set a3-D oil spill transport and diffusion model. After the model being built, we simulated the oil film influenced on the starting influence time and duration time of Songpu water intake in Huangpu river, Chenhang Reservoir, Qingcaosha Reservoir and Dongfengxisha Reservoir respectively, and analyzed the thickness, trace and concentration of each layer underwater of the oil film by different river discharge, tide, wind and temperature. The conclusions are as follows:The quality of oil spill that happened at the pier of the Fengpu Bridge in Huangpu river was set to100ton. The arrival time that oil film get to Songpu water intake upstream was calculated to be about4hours. Due to the influence of wind effect, the thickness and influencing duration of oil film near water intake was far greater in summer than that in winter. Under the larger river discharge, the main part of oil film was transported downstream after a whole tidal period, and the distance was farther in winter than that in summer. The percentage of evaporation in winter was less because of the lower temperature.After the oil spill happened at the pier of Sutong Bridge in the Changjiang river estuary, the cost time that oil film reached the water intake downstream was least in the spring tide in summer, while it cost most in the neap tide in winter. Compared with the river discharge in winter, it is more abundant in summer. The river discharge is the determinant factor of the difference between summer and winter. On the effect of wind, the oil film was thicker near Dongfengxisha reservoir in summer and Chenhang reservoir in winter. Due to the larger net unit residual flux during the neap tide, the oil film was transported farther downstream in the neap tide through a whole tidal period. The percentage of water entry was higher in winter than that in summer, and most oil particles were concentrated in the surface layer. The concentration contours of oil particles were evenly distributed because of the strong vertical mixing during the spring tide, and the contours was concentrated near the surface layer during the neap tide due to the weak mixing.The results of model can reflect the impact of transport, diffusion, evaporation and water entry of oil film on river discharge, tide, wind and temperature dramatically. The explanation in hydrodynamics has well done about this study. It has scientific and technical guidance effects on the security of reservoirs in Huangpu river and Changjiang river estuary. |
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