Saltwater Intrusion in the Changjiang Estuary

Jianrong Zhu, Hui Wu, Lu Li, Cheng Qiu
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引用次数: 39

Abstract

Saltwater intrusion in the Changjiang Estuary and the impacts of river discharge, tide, wind, sea level rise, river basin, and major estuary projects on saltwater intrusion are studied in this chapter. There is a net landward flow in the NB (North Branch) when river discharge is low during spring tide, resulting in a type of saltwater intrusion known as the SSO (saltwater-spilling-over from the NB into the SB (South Branch)), which is the most striking characteristic of saltwater intrusion in the estuary. A three-dimension numerical model with HSIMT-TVD advection scheme was developed to study the hydrodynamic processes and saltwater intrusion in the Changjiang Estuary. Saltwater intrusion in the estuary is controlled mainly by river discharge and tide, but is also influenced by wind, sea level rise, river basin, and estuary projects. Saltwater intrusion is enhanced when river discharge decreases. There is more time for the reservoir to take freshwater from the river when river discharge is larger. The fortnightly spring tide generates greater saltwater intrusion than the neap tide. The saltwater intrusion in the SP (South Passage) is stronger than that in the NP (North Passage), and the intrusion in the NP is stronger than that in the NC (North Channel). The northerly wind produces southward currents along the Subei coast as well as the landward Ekman transport, which enhances the saltwater intrusion in the NC and NB and weakens the saltwater intrusion in the NP and SP. Saltwater intrusion becomes stronger as the sea level rises and is much stronger when river discharge is much small. The DWP (Deep Waterway Project) alleviates the saltwater intrusion in the NC and the lower reaches of the NP and enhances the saltwater intrusion in the SP and in the upper reaches of the NP. The Three Gorges Dam (TGD) increases river discharge in winter, which weakens saltwater intrusion, and is favorable for reducing the burden of freshwater supplement in the highly populated estuarine region. The Water Diversion South to the North Project (WDP) decreases river discharge, enhances saltwater intrusion, and is unfavorable for freshwater supply in the estuary.
长江口咸水入侵
本章主要研究了长江口的咸水入侵,以及河流流量、潮汐、风、海平面上升、流域和主要河口工程对咸水入侵的影响。在春潮期间,当河水流量较低时,北支有向陆地的净流,形成了一种称为SSO (salt -spill -over of NB - into SB (South Branch))的盐水入侵,这是河口最显著的盐水入侵特征。采用HSIMT-TVD平流格式建立了长江口水动力过程和海水入侵的三维数值模型。入海口海水入侵主要受河流流量和潮汐控制,同时还受风、海平面上升、流域和入海口工程的影响。当河流流量减少时,盐水入侵增强。当河流流量较大时,水库从河流中吸取淡水的时间更长。每两周的大潮比小潮产生更大的盐水入侵。SP(南通道)的盐水入侵强度大于NP(北通道),NP(北通道)的盐水入侵强度大于NC(北通道)。北风在苏北沿岸产生南向气流和向陆地的Ekman输运,增强了北、南海区的咸水入侵,减弱了北、南海区的咸水入侵。咸水入侵随着海平面上升而增强,当河流流量较小时,咸水入侵更强。深水航道工程缓解了长江上游和长江下游的咸水入侵,增强了长江上游和长江上游的咸水入侵。三峡大坝在冬季增加了河流流量,减弱了咸水入侵,有利于减轻人口密集的河口地区的淡水补充负担。南水北调工程减少了河流流量,增加了咸水入侵,不利于河口的淡水供应。
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