The Nandu River Estuary is a relatively short estuary with a standing wave system. The saltwater intrusion in recent years witnesses a trend of exacerbation. Based on the observation data collected in February of 2009 and a medium-term observation of surface salinity from November to December of 2009, combined with model results of velocity by EFDC, this study focused on the spatial variations of salinity, stratification in the timescales of the intratidal to the intertidal. The results showed that from the estuary's mouth towards upstream, the tidal current and the salinity both decreased, while the stratification increased. The stratification was increased at ebb tides and reduced at flood tides. The mixing was obviously increased from neap to spring tides. The deep holes formed by sand mining acted as trappers for high salinity water, which increased the severity of saltwater intrusion in the dry season. The data clearly indicated that the saltwater intrusion was stronger during neap tides than that during spring tides.%南渡江河口长度较短,河口内驻波发育.河口内盐水入侵近年来呈加剧之势.根据2009年2月大小潮多站同步的周日水流、盐度观测以及2009年11-12月连续38天的表层盐度观测资料,结合EFDC数值模拟结果,分析了南渡江河口枯季大小潮期的盐度与水体分层的时空变化规律.结果表明,枯季时南渡江河口干流自口门向陆,潮流流速递减,盐度减小,水体分层增强.水体分层在落潮时增大,涨潮时减小.大潮期的混合作用强于小潮期.河道内采砂形成的深坑对高盐水起到捕集作用,涨潮时输入的高盐水在落潮时无法向海输出,对南渡江的盐水入侵起到加剧作用.实测资料显示,小潮期的盐水入侵长度要大于大潮期.
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