长江口北支近期水流泥沙输移及含盐度的变化特性

Variation characteristics of sediment transport and salinity in north branch channel of Yangtze River estuary in recent years

为了保障长江口北支的航运功能,满足沿江两岸引排水需求,对20世纪70年代以来长江口水文观测资料进行分析。结果表明:近期北支分流比持续减少,涨潮分流比大于落潮;洪、枯季涨落潮分沙比呈减小之势,且均大于相应的分流比。近年来,泥沙倒灌南支现象有所减弱;北支河段受径流影响逐渐减小,主要受潮流作用影响,但随着下段喇叭口逐渐收缩,涨潮量有减小之势;北支涨潮含沙量大于落潮,在涨落潮流流路分离段含沙量明显大于其他位置。北支含盐度枯季显著大于洪季,且含盐度沿程的差异洪季明显大于枯季,近年来河段含盐度有所减小。人工缩窄工程对北支近期水流泥沙输移及其含盐度有明显的影响。

In order to ensure the navigation functions of the north branch channel of the Yangtze River estuary and to meet the demand of water diversion and drainage in the region along the Yangtze River,the observed hydrology data of the Yangtze River Estuary since the 1970s, was analyzed.The results show that the flow diversion ratio of the north branch channel of the Yangtze River has been decreased continually in recent years,and its value at flood tide is greater than that at ebb tide.The sediment diversion ratios at flood and ebb tides tend to decrease in flood and dry seasons,and they are greater than the corresponding flow split ratios.The phenomenon that sediment flows backward into the south branch of Yangtze River estuary has been weakened in recent years.The influence of runoff on the north branch channel is decreasing gradually,and the tidal current has a dominant influence on the north branch channel.With the gradual narrowing of the bell-mouth in the downstream reach,the flood tidal volume tends to decrease.The sediment concentration at flood tide is greater than that at ebb tide.The sediment concentration at the reach where the flow paths of flood current and ebb current separate is greater than that at other sites.The salinity of the north branch channel in dry season is significantly greater than that in flood season.The salinity variation along the north branch in flood season is greater than that in dry season.The salinity has been decreased in recent years.The artificial narrowing projects have a significant effect on the recent variation of sediment transport and salinity of the north branch channel.