淡澳河口—大亚湾三维潮流及海水入侵模拟

3D tidal flow and seawater intrusion simulation in Dan’ao Estuary-Daya Bay

淡澳河是大亚湾入海河流中流量最大且水质最差的河流,探究淡澳河口流域水动力水质变化对沿海环境风险管控和海岸带整治修复具有重要意义。基于环境流体动力学(EFDC)模型建立淡澳河感潮河段及整个河口区水动力水质模型,重点研究径潮流作用下淡澳河下游及河口区水动力过程,定量估算不同水期下盐水入侵及河流水质的响应关系。结果表明:1)大亚湾潮流以不规则半日混合潮型为主,每月约8~10 d为日潮,20~22 d为半日潮,日潮和半日潮下,表层水体不能到达虎爪断面(国控点位),底层水体可入侵到虎爪断面上游约700~1100 m处;2)不同水期下的盐水入侵表明,淡澳河水体枯水期含盐量最高,达16‰,研究基于2019年水文资料初步划分了河海水团交界线,可为河口海岸带淡水和海水分类整治提供依据;3)由咸淡水交互与水质响应关系可知,丰水期污染物浓度相较于平水期增加明显,约为10%,上游流量变化直接影响水质,小潮期间尤为明显,建议进行工程优化调度减小小潮期间的下泄流量。

The Dan’ao River is the one with the largest flow and the worst water quality in Daya Bay’s rivers flowing into the Southern Ocean.Exploring the hydrodynamic water quality changes of the Dan’ao River is of great significance for coastal environmental risk control and coastal zone remediation.The hydrodynamic water quality model of the tidal reach and the whole estuary area of the Dan’ao River were established based on the EFDC model.The hydrodynamic process in the downstream and estuarine area under the action of runoff and current was mainly researched,and the response relationship between saltwater intrusion and water quality in different water periods was estimated quantitatively.The results showed that the tidal characteristics of Daya Bay were mainly irregular semi-diurnal mixed tide,which was diurnal tide about 8-10 days a month,and semi-diurnal tide about 20-22 days a month.Under the diurnal tide and semi-diurnal tide,the bottom water could invade the upstream of Huzhao section(the national section)about 700-1100 m,but the surface water could not reach the section.The salt water intrusion in different water periods showed that the salt content was the highest in the low water period,up to 16‰.Based on the hydrologic data of 2019,the boundary of river and sea water mass was preliminarily divided,which could provide the basis for the classification and regulation of fresh water and sea water in the estuary and coastal zone.According to the interaction between salt water and fresh water,the concentration of pollutants in the high water period increased significantly,about 10%higher compared with that in the average water period,and the change of upstream flow directly affected the water quality,especially during the neap tide.It was suggested to optimize the project scheduling to reduce the discharge during the neap tide.