中文摘要：

基于大量现场水沙观测及海图资料，首先分析总结了南、北槽分流口历史演变规律；其次，对长江口深水航道治理工程建设以来南、北槽分流口河段水流动力特征，近期分流口演变规律及分流潜堤工程建设对分流口河段河道演变和水动力条件的影响进行了研究6结果显示：南港下游至南、北槽分流口河段深泓线位置经历了南一北一南的换位过程；南、北槽分流沙洲的方位角受外海上溯潮波控制，基本保持在305°，但由于分流口上提至江亚南沙及分流潜堤的建设，分流沙洲洲头逐渐北偏，目前分流沙洲方位角在314°左右，伸入到分流潜堤北侧河道，与此同时，南、北槽进口过水断面（0m以下）总面积维持稳定的前提下，北槽过水断面持续减小，南槽相应增加；目前，南港下游水流流向出现南偏，落潮主流偏向南槽，南槽进口断面平均潮流速大于北槽。

英文摘要：

In this paper, the evolution law of the Diffluence Pass of the South Passage and the North Passage in past years, the characteristics of the current in this area and the morphological changes since the commissioning of the Yangtze Estuary Deepwater Channel Regulation Project are studied. The effects of the di- version works on its recent evolution and hydrodynamic conditions are also discussed. The study is based on field observation data and sea chart data. The results reveal that the thalweg of the lower reach of the South Channel swung from south to north, then back to south again. Under natural state controlled by the external o- cean tide, the azimuth of the sandbar head kept stable, which was 305 degrees. After the incorporation of Jiangya Nansha shoal into the Jiuduansha shoal and the construction of diversion works, the head of the difflu- ence shoal experienced a gradual northern shift and its azimuth at present is around 314 degree, stretching to the deep waterway. At the entrance to the South Passage and the North Passage, the total area of the cross sec- tion （below 0m） keeps stable. Meanwhile, the cross section area of the North Passage reduces, and the cross section area of the South Passage increases. At present, the current direction in the South Channel turns to south, and the ebb current at the entrance flows to the South Passage, the averaged cross-sectional current speed of the South Passage is bigger than that of the North Passage.