象山港水交换能力研究

为深入研究象山港水交换现状,并为港区生态模型等后续研究提供数据,运用Delft3D软件运行了一个已校准的水动力模型,用模型输出的水位和流速数据分析象山港纳潮量和水流特征,并用模型输出的盐度和示踪剂数据求得基于箱式模型的水更新时间和基于Delft3D示踪剂模型的水更新时间.结果表明:港区平均纳潮量为1.32×109 m3,大潮纳潮量为1.82×109 m3,小潮纳潮量为0.82×109 m3.箱式模型得出滞留系数为0.9,水更新时间约13~21 d.Delft3D示踪剂对流-扩散模型得出水更新时间约4个月,置换35%的水体需5d,置换65%的水体需125d,置换90%的水体需305 d;示踪剂垂直混合充分,水平差异显著,口门区示踪剂平均滞留时间少于10 d,港中区约170d,港顶区超过250d.因此象山港是口门水交换强烈,但中顶部水交换很弱的港湾,其排污口应设在西泽码头以东,港顶应养殖大型海藻,并控制鱼虾养殖规模以减轻富营养化.

Study on the Features of Water Exchange in Xiangshan Bay

In order to study the ability of the water exchange in Xiangshan Bay and yield the source data for the eco-modeI in the future, a calculated Delfl3D hydrodynamic model is built. The data of water level and flow velocity produced by the model is used to analyze the tidal prism and flow characteristic of Xiangshan Bay. The data of salinity and tracer material produced by the model is used to investigate the flushing time of prism-model and that of tracer-model. The results show that the average tidal prism is 1.32×10^9m^3, while the tidal prism is 1.82×10^9m^3 during flood tide period and 0.82×10^9m^3 during ebb tide one. In prism model, the coefficient of retention is 0.9 and it takes about 13 to 21 days to refresh the whole water of the bay. In Delfi3D tracer-model, it uses about 4 months to refresh the whole water of the bay; and exchanging 35% of the water needs 5days, while 65% needs 125 days and 90% needs more than 305 days. Conservative tracer is mixed well in vertical direction, so there is no obvious stratification. The average residence time of bay-mouth is less than 10 days, while it is about 170 days at the bay-middle （15km from the west of Xize wharf） and is above 250 days at the bay-head including Huangdun Bay and Tie Bay. Hence, the ability of water exchange in Xiangshan Bay is very strong at bay-mouth but weak at bay-head. The drainage outlets should be set at the east of Xize wharf, seaweeds should be cultivated and fish cages should be controlled to decrease the risk of eutrophication.