数值分析海平面上升对磨刀门水道咸潮上溯的影响

Modeling Approach to Assess the Effects of Sea Level Rise on Saltwater Intrusion In Modaomen Estuary

磨刀门咸潮上溯有逐年增强的趋势,其发生的频率也越来越高。采用非结构有限体积近岸海洋模型FVCOM建立了磨刀门水道三维咸潮水动力数学模型,并采用实测潮位和盐度对模型进行了率定和验证,表明该模型能够较好地反映磨刀门咸潮上溯的水动力情况。采用已率定的模型,对外海海平面上升15 mm的工况进行数值模拟,研究了海平面上升对咸潮上溯的影响。结果表明,海平面每升高1 cm,磨刀门水道平均水位将升高0~1.67cm;磨刀门水道内表层和底层盐度均随着海平面的上升而增大,咸潮上溯的规律不随海平面的上升而改变;磨刀门水道河口处表、底层盐度增幅相差不大且均不随潮差的大小而变化;河道上游段,海平面上升对底层的影响明显大于对表层的影响,而且表、底层盐度均随着潮差的减小而增大;海平面平均每升高1 cm,磨刀门水道咸潮入侵平均上移距离为0.85 km。该研究对压咸措施有一定的指导意义。

The saltwater intrusion was becoming a serious problem year by year in Modaomen watercourse of Pearl River Estuary, this study applied a three - dimensional finite - volume coastal ocean model （FVCOM） to simulate the tidal levels and salinity field and it was successful in Modaomen estuary. The calibrated model was then applied to simulate the salinity and flow velocity field after rising 15 mm of the sea level. The results showed the increase of the sea level by 1 cm would raise the average tidal levels by 0 to 1.67 cm in Modaomen estuary . The surface and bottom salinity increased with the rising sea levels in modaomen estuary, but the law of saltwater intrusion would not be changed by sea level rising. The difference of salinity increase of surface and bottom in Modaomen estuary was not significant and it remained unchanged with the size of the tidal range. The impact of sea level rising on the bottom layer was more significant than the surface layer in the upstream of water channel. In addition, salinity of both surface and bottom layer increased with the tidal range decreased. On average, with the sea level increased by 1 cm, the shift distance of saltwater invasion in Modaomen estu- ary was 0. 85 km. This research would provide some references for assessing the effects of controlling engineering measures on saltwater intrusion.