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以长江口徐六泾断面2009年实测水沙数据为基础,分析了其水沙特征,重点研究了三峡蓄水及长江流域旱情对徐六泾节点径流、潮位和泥沙过程的影响。结果表明:观测期间寸滩站以上流域来水减少、三峡蓄水和中下游干旱共同导致进入河口的径流量减少,各自造成的影响权重分别为38%、13%和49%。与蓄水前相比,蓄水期间徐六泾涨潮历时增加0.5h,落潮历时减少0.5h,潮差增大约0.4m;涨潮平均流速增加35%~126%,落潮平均流速浅滩处基本不变,而深槽处减幅约为22%;蓄水期间涨落潮历时、流速流向等特征由不对称趋于较对称,说明徐六泾的水动力特征对径流减少的响应敏感。伴随径流减少,徐六泾含沙量由蓄水前的0.129kg/m3大幅下降至蓄水期间的0.052 3kg/m3,悬沙中值粒径则由3μm增大到5μm。综合得知进入河口徐六泾断面的水沙过程受到流域人类活动和自然条件改变的双重影响。
Based on the measured data of water and sediment in 2009 in Xujiajing section of the Changjiang Estuary, the characteristics of water and sediment were analyzed. The effects of the Three Gorges impoundment and the drought in the Yangtze River on the runoff, tide and sediment process of Xuliujiao node were studied emphatically. The results show that during the observation period, there is a decrease in incoming water from the catchment above the Cuntan station, and the runoff from the Three Gorges reservoir and the middle and lower reaches of the river led to a decrease of runoff into the estuaries with the respective weights of 38%, 13% and 49% respectively. Compared with that before water storage, Xu Liujing tidal current lasted 0.5 h, tide lasted 0.5 h, tidal range increased about 0.4 m, tidal average flow increased 35% -126% , While the decrease of deep groove was about 22%. During the tide of tidal current, the features of tidal current and flow velocity during the water storage period tended to be more symmetrical by asymmetry, indicating that the hydrodynamic characteristics of Xuliujing is sensitive to the decrease of runoff. With the decrease of runoff, the sediment concentration of Xuliujing dropped from 0.129kg / m3 before storage to 0.052 3kg / m3 during storage, while the suspended sediment median diameter increased from 3μm to 5μm. It is concluded that the process of water and sediment entering the section of Xuli Liujing section of estuary is affected by both human activities and changes of natural conditions in the basin.