基于观测的磨刀门咸界影响因素相关性探究

Study on correlation of factors affecting saline intrusion length in Modaomen estuary based on field observations

为进一步了解磨刀门枯季咸水上溯特性,2017—2018年枯季在磨刀门水道进行三次半月周期的咸界走航观测,同时收集该时段磨刀门水道的水文气象资料,结合不同河段的纵向和平面地形特征,对逐日咸水最大上溯距离与上游流量、外海潮差、海面高程及北向风速进行相关分析。结果表明,河道地形对这些因素的相关系数和相关显著性有明显影响。在下游洲岛分汊河段,由于分汊河道的调节作用,咸界与各因素相关不显著,相关系数比全河段的分析结果小;在上游窄深单槽河段,咸界与流量和潮差的相关性达到显著水平,相关系数明显增大,并且咸水易于加速进侵。通过分析还发现,尽管流量是相关性最高的主导性因素,但当其他因素如潮汐、风和地形等的作用突出时,流量对咸水运动的影响减弱而失去主导地位。

To better understand the characteristics of saltwater intrusion in the Modaomen estuary in dry season, fortnight ship-mounted observations of the waterway were carried out three times in the dry season of 2017-2018, and hydrological and meteorological data of the waterway were collected for this period. This paper presents an analysis of the correlations between the saline intrusion length with inflow discharge, tidal range, sea level, and north wind speed, in combination with analysis of the features of longitudinal and plane topographies for different waterway sections. The results show changes in channel topography impose a significant impact on these correlations. Due to the modulation of the bifurcating reaches, correlation coefficients for the downstream section featured with central bars are smaller than those for the whole section observed. In the upstream section with a narrow, deep single main channel, the location of saltwater upper boundary has higher correlation with runoff discharge and tidal range;and it tends to accelerate saltwater intruding. We also find the influence of runoff on saltwater movement may be weakened and lose its dominating role when the combined action of other factors–such as tide, wind and topography–becomes prominent, although it is usually the most relevant dominant factor.