| 摘要: |
| 径流是影响河口水沙输运的关键动力之一。以长江口为例,历史最大洪水为1954年的92 600m3/s,但以往洪枯季水沙观测期间的大通流量多数小于60 000m3/s,对于特大流量情况下的河口水沙输移特征还缺少观测资料和相关研究报道。2020年长江发生了流域性大洪水,大通洪峰流量高达84 500m3/s。为认识特大流量情况下的河口水沙输移格局特征,文章基于2020年7月78 300m3/s流量期间南槽中下段大小潮水沙盐定点观测资料,分析认识到大洪水期间南槽下段水体垂向混合良好,层化发生位置向海外移,表明大流量抑制了盐水入侵。对比分析历史不同流量情况下的南槽区域水沙资料,表明在特大径流作用下,南槽中下段区域盐度和悬沙浓度整体减小,相比在9 900m3/s (2014年)、17 637m3/s(2003年2月)和41 450m3/s(2013)流量下,南槽下段大潮平均盐度分别减小75%、82%和82%,小潮分别减小80%、89%和91%;全潮悬沙浓度分别比9 345m3/s(2004)、17 637m3/s(2003)、41 450m3/s(2013)、60 877m3/s(2003)情况下减少63%、62%、70%、73%。悬沙浓度减小的原因可能包括河流减沙的长期影响以及大流量情况下的水体稀释作用。这一研究丰富了特大径流情况下的河口水沙输移特征的认识,可为航道和河口治理提供认知基础。 |
| 关键词: 特大径流 长江口 南槽 水沙输运 |
| DOI：10.11693/hyhz20210800194 |
| 分类号:TV148 |
| 基金项目:国家自然科学基金,51739005号;长江水科学研究联合基金,U2040216号;上海市科委社发研究项目,20DZ1204700号,19QA1402900号;科技部中荷战略合作,2016YFE0133700号。 |
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| A FIELD STUDY OF HYDRODYNAMICS AND SEDIMENT TRANSPORT IN THE SOUTH PASSAGE OF THE CHANGJIANG RIVER ESTUARY DURING BIG RIVER FLOOD IN JULY 2020 |
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WU Zeng-Bin, GUO Lei-Cheng, WU Xue-Feng, HE Qing
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State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200241, China
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| Abstract: |
| River discharge is one of the key factors affecting hydrodynamics and sediment transport in estuary. Previous field surveys and studies in the Changjiang (Yangtze) River estuary were mainly conducted for river discharge, and the discharge recorded at Datong Station is often <60 000 m3/s. However, estuarine dynamics under higher river discharge conditions remains poorly studied. In 2020, a large flood took place in the river basin and the peak volume at Datong reached 84 500 m3/s. We conducted a field survey in the South Passage of the river mouth in July 2020 when river discharge at Datong was 78 300 m3/s. The results show that the seaward water mass of the South Passage is well-mixed and stratified beyond the channel, which implies that high river discharge could mitigate salt intrusion. Historical data show that the average salinity was 75%, 82%, and 82% lower in 2020 than those under different river discharges of 9 900 m3/s (2013), 17 637 m3/s (February 2003), and 41 450 m3/s (2014), respectively, during spring tide; and 80%, 89%, and 91% lower, respectively, during neap tide. In addition, under river discharge of 9 345 m3/s (2004), 17 637 m3/s (February 2003), 41 450 m3/s (2013), and 60 877 m3/s (July 2003), the average concentration of suspended particles decreased by 63%, 62%, 70%, and 73%, respectively, due to long-term decline in riverine sediment carriage and dilution of larger river flow. This study enriches the understanding of estuarine hydrodynamics and sediment transport under extremely large river discharge, and provides basic knowledge for waterway and estuarine management. |
| Key words: extreme flood Changjiang River estuary the South Passage sediment transport |
