基于实测资料的长江河口南支河段盐水入侵规律分析

RESEARCH ON SALTWATER INTRUSION OF THE SOUTH BRANCH OF THE CHANGJIANG ESTUARY BASED ON MEASURED DATA

为对长江口南支河段盐水入侵规律有清晰的认识,在梳理、总结以往研究成果的基础上,通过对历年咸潮及氯度实测资料的分析,对长江口南支河段盐水入侵的规律进行了较为全面系统的分析研究。研究表明:北支盐水倒灌是长江口南支河段盐水入侵的主要来源;在研究水域,枯季大潮期氯度的沿程分布表现为两头高、中间低的"马鞍形"形式,枯季中潮期则为"高-低-高-低-高"的复杂的"W"形的分布形式;受外海潮汐和上游径流的综合作用,由大潮到中潮,倒灌盐水团在下移过程中,氯度的沿程分布形式发生了变异;近期盐水入侵的程度有加剧的趋势;研究水域2～3月盐水入侵最严重,在这段时间内盐水入侵超标次数多、历时长;当大通流量小于20 000m3/s时,就可能发生明显的北支盐水倒灌南支现象;盐水入侵程度跟大通流量和潮汐强度密切相关;大通流量越大,盐水入侵程度越低;潮差越大,盐水入侵程度越高。

Based on previous studies,the characteristics of saltwater intrusion of the South Branch of the Changjiang Estuary were studied systematically by the analysis of measured saltwater intrusion and chlorinity data.Results indicate that the saltwater which spills over from the North Branch is the main source of the salt intrusion of the South Branch.In the study area,the distribution of chlorinity during dry season＇s spring tide appears as a two-side-high and middle-low＇s saddle shape,while the distribution of chlorinity during dry season＇s middle tide appears as a high-low-high-low-high＇s ＇W＇ shape.Because of the effects of tide and up-stream＇s discharge,the distribution shape of chlorinity has varied from spring tide to middle tide.The intensity of the salt intrusion of the South Branch tends to be much more serious since 1998;the salt intrusion of the South Branch is much more serious during February and March than other months;the salt intrusion of the South Branch may take place when the discharge from Datong station is less then 20 000 m3/s.There are close relationships between discharge from Datong station and tidal strength;larger the discharge,lower level of the salt intrusion;greater the tidal range,higher level of the salt intrusion.