海南岛南渡江河口的盐水入侵

南渡江是海南岛最大的河流,河口长度较短(约25 km),口外濒临琼州海峡。南渡江的盐水入侵近年来呈加剧趋势,急需对其过程与机理进行研究。本研究运用FVCOM模型,采用2009年枯季的实测数据对模型进行了验证。根据模型计算结果分析了枯季和洪季南渡江河口的流速和盐度的时空分布及盐水入侵的变化,探讨了河口不同位置驱动盐分向陆输运的机制。研究结果表明:枯季小潮时的河口环流强度大于大潮时,而洪季河口环流在大潮时更加发育,洪枯季都表现出大潮期的盐度分层(表底层盐度差)大于小潮期;口门附近,潮汐振荡输运在总的向陆盐分输运通量中占主导,而向上游方向,稳定剪切输运则表现得更重要。主河道内损失的盐分主要通过海甸溪的盐分输入进行补充。

Saline intrusion in the Nandu River Estuary, Hainan Island

Nandu River is the largest river in Hainan Island. The Nandu River Estuary is a short one, with a length of approximately 25 km and faces the Qiongzhou Strait in the north. The saline intrusion in the estuary demonstrates a trend of exacerbation in recent decades and requires a detailed study for its mechanism. In this study, the FVCOM model is utilized, which is calibrated by the observation data in February, 2009. Simulations for the dry and wet seasons are then conducted, respectively. The model results are used to study the temporal and spatial variations of flow, salinity and saline intrusion in the estuary during the two seasons. The mechanisms driving the landward salt flux at different positions of the estuary are investigated. The results indicate that the circulation is stronger during the neap tide in the dry season, while the situation becomes opposite in the wet season. The salinity stratification is weaker during the neap tide in both seasons. The saline intrusion distance is much longer in the dry season. The oscillatory tidal dispersion is the dominant agent driving the landward salt flux at the river mouth, while the steady shear becomes more important toward upstream. The deficit of salt in the main stream is balanced mainly by the salt input through the Haidianxi branch.