长江口2013年和2014年枯季盐水入侵分析

Analysis of saltwater intrusion into Yangtze estuary during dry seasons of 2013 and 2014

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 ol saltwater intrusion into the Yangtze （Changjiang） estuary and thesaltwater spilling over from the north branch ol the Yangtze estuary in dry seasons, two tidal synchronous hydrologicsurveys were carried out in the bifurcation ol the north branch and the south branch in December 2013 and February2014. Analyses of the data have given several conclusions. Under the impacts of geomorphology, the salinity in theentrance of the north branch is an order of magnitude higher than that of water in the Baimao shoal. The salinity ofwater is negatively correlated to the runoff volume, while tidal range is positively related. The saltwater will spillover from the north branch while the runoff volume is relatively small and the tidal range is relatively large. Due tothe backwater effects of the runoff, the spilling saltwater is forced to head for the north, so the salinity of the northchannel of Baimao shoal is larger than that of the south channel. The wind stress has a significant effect on thesalinity intrusion and the continuous south wind can decrease the intensity of the salinity intrusion in the northbranch. The saltwater spilling over from the north branch flows on the south side of Baimao shoal,s north channel,and stays in Baimao shoal for several days during spring tide and the salinity in water around Baimao shoal reachesa maximum value in the moderate tide after the spring tidal.