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为研究长江口枯季盐水入侵及北支盐水倒灌特性,于2013年12月及2014年2月两次对长江口南北支分汊口处进行全潮同步水文测验,分析结果表明:受地形地貌因素影响,北支进口盐度比同期南支白茆沙水域的高出一个数量级。水域盐度与径流量大小呈负相关关系,与潮差大小呈正相关关系。径流较小、潮差较大时,北支盐水会发生倒灌。由于下泄径流的顶托,迫使倒灌盐水北偏,使得白茆沙北水道盐度大于南水道。风应力对盐水入侵的影响不可忽视,持续的南风会减弱长江口北支的盐水入侵。在枯季条件下,北支倒灌盐水一般沿白茆沙北水道南侧下泄。大潮时倒灌进入南支的盐水在白茆沙水域有一定时间的滞留,使得白茆沙水域盐度往往会在大潮后的中潮期达到最大。
In order to study the characteristics of saltwater intrusion in the Yangtze River estuary in the dry season and the characteristics of salt water intrusion in the northern branch, a full tide synchronized hydrological test was carried out on the northern and southern branches of the Yangtze Estuary in December 2013 and February 2014 respectively. The results showed that: As a result, the salinity of the northern branch was one order of magnitude higher than that of the southern branch of the Baijisha Sea. There is a negative correlation between salinity and runoff, and a positive correlation with tidal range. Small runoff, large tidal range, the North Branch of salt water will occur intrusion. Due to the release of runoff from the top, forcing the backwater brine northward, making the Baisha sand North Saline salinity greater than the South. The influence of wind stress on saltwater intrusion can not be neglected. The continuous south wind will weaken the salt water invasion in the north branch of the Yangtze Estuary. Under the dry season conditions, the North Branch backfill brine generally flows along the south side of the Baisha sand north channel. During the tide, the salt water intruded into the south branch has a certain period of stay in the Baizhaisha waters, making the salinity of the Baizhaisha reach the maximum in the tidal period after the tide.