2014年2月持续强北风下长江口发生了极端严重的盐水入侵事件, 影响水源地取水安全. 流域上游水库增加径流量是遏制严重盐水入侵的一种方法, 本文应用UnFECOM (unstructured quadrilateral grid, finite-differencing, estuarine and coastal three-dimensional ocean numerical model) 模式模拟和分析该次盐水入侵对增加不同径流量的响应. 考虑实际径流量和风况, 模式再现了该次极端严重盐水入侵事件. 数值试验结果表明, 随着径流量的增加, 在2014年2月10—13日盐水入侵最严重时段北港上段的净水体输运仍然向陆, 但量值随径流量增加趋于减小; 北港上段的净分流比、净水通量和盐通量随着径流量增加而增加; 在实际径流量试验中, 北港上段分流比为 –29% (负号表示净水通量向陆) , 净水通量为 –2300 m³/s, 净盐通量为 –68 t/s, 表明受到持续强北风产生的向陆艾克曼输运作用, 北港净水通量和盐通量向陆. 当径流量增加3000 m³/s时, 北港净分流比和水通量接近零, 净盐通量为 –34 t/s. 当径流量增加8000 m³/s时, 北港分流比为21.5%, 净水通量为3550 m³/s, 净水通量向海输运; 净盐通量为 –6 t/s, 仍向陆输运. 在青草沙水库取水口, 当径流量增加小于4000 m³/s时, 最长连续不宜取水时间下降不明显; 当径流量增加值达到5000 m³/s时, 最长不宜取水时间下降显著, 达到了10.5 d. 5000 m³/s的径流量的增加量值和适当的持续时间, 对三峡水库的实际调度是较难做到的. 预警和预报盐水入侵, 在严重盐水入侵来临之前将上游水库蓄至高水位, 保证有充足的库容进行水资源调度, 是保障水库取水安全的一种有效方法.

In February 2014, a persistent and strong northerly wind caused an extremely severe saltwater intrusion event in the Changjiang Estuary, which posed a threat to the safety of water intake from this source. Increasing river discharge from upstream reservoirs in the river basin is a method to combat severe saltwater intrusion. To simulate and analyze the effects of various river discharges on saltwater intrusion, we used the Unstructured quadrilateral grid, Finite-differencing, Estuarine and Coastal three-dimensional Ocean numerical Model (UnFECOM). By taking into account realistic river discharge and wind conditions, the model accurately reproduced the extremely severe saltwater intrusion process that occurred in February 2014. Our findings indicated that the net water flux (NWF) across the section at the upper reaches of the North Channel (NC) remained landward during the most critical period of saltwater intrusion from February 10 to 13, 2014, despite the increase in river discharge. However, the magnitude of NWF tended to decrease with increasing river discharge. The net water diversion ratio (WDR), NWF (Net Water Flux), and salt flux increased with the increase in river discharge. Under realistic river discharge conditions, WDR was –29% (the negative sign indicates that the NWF is landward), NWF was –2300 m ³/s, and the net salt flux (NSF) was –68 t/s, indicating that the NWF and NSF were landward due to the landward Ekman transport effect induced by the persistent severe northly wind. When the river discharge increased by 3000 m ³/s, WDR and NWF across the section were nearly zero, and NSF was –34 t/s. When the river discharge increased by 8000 m ³/s, WDR was 21.5% and NWF was seaward, at 3550 m³/s. NSF was –6 t/s and landward. At the water intake of Qingcaosha Reservoir, the longest continuous unsuitable water intake time decreased slightly when the river discharge increased by less than 4000 m ³/s. When the river discharge increased to 5000 m³/s, the longest continuous unsuitable water intake time decreased significantly to 10.5 days. It may be challenging to achieve the necessary value and duration of river discharge increase required for the actual operation of the Three Gorges Reservoir. To ensure the safety of water intake, implementing an early warning and forecasting system for saltwater intrusion and storing water into the reservoir at a high level before the intrusion occurs are recommended as effective methods.