中文摘要：

为探讨磨刀门水道潮流和盐度的三维分布特性,本文建立了磨刀门水道的三维潮流和盐度数值模型,采用2009年枯季磨刀门水道实测潮流和盐度资料对模型参数进行率定和验证。结果显示,枯季由于上游径流量小,磨刀门水道总体涨、落潮流速都不大,表层总体涨潮平均流速都在0.5 m/s以内,总体落潮平均流速在0.8 m/s以内;底层总体涨落潮平均流速都在0.5 m/s以内;从盐度的平面分布来看,磨刀门水道近口门河段总体呈现涨潮时水道东侧盐度高于西侧,落潮时东侧盐度小于西侧的趋势。大潮和中潮期间,落潮时盐水向上游的入侵距离反而较涨潮时更远,主要原因是,落潮时的底层盐水向上游的补偿流动以及地形阻拦形成更为强烈的紊动扩散。潮汐动力弱（小潮）时,整个水道内水流流速很小,流态平缓,紊动较弱,总体仍呈现涨潮时入侵距离大于落潮,显示枯季磨刀门水道盐水入侵的主要影响因素取决于地形和潮动力。

英文摘要：

To investigate the characteristics of tidal flowing and salinity in Modaomen waterway, three dimensional hydrodynamic and salinity mathematical models were established and verified by using field data during dry season in 2009. It is shown that the total flowing velocities in Modaomen waterway were rather small during dry season. The average velocities at water surface varied within less than 0.5 m/s during flood and 0.8 m/s during ebb with velocities at bottom within 0.5 m/s. According to plane distribution of salinity in the reach close to the estuary, salinities close to east bank were less than those close to west during flood, while vice versa during ebb. Saline water intruded farther upstream during ebb than during flood under stronger tidal power （in spring and middle） because of emergence of more intensive compensation flow upstream at bottom, while saline water was diffused upstream severely during ebb for stronger turbulence and reflection by topography. However, intrusion distances of saline water during ebb were still less than that during flood in neap for weaker tidal power and turbulence with smaller velocities and gentler tidal flowing in the waterway. So the characteristics of saline water intrusion in dry season depend on tidal power and topography in Modaomen waterway.