|LI Yunliang,YAO Jing,LI Mengfan,ZHANG Qi.Numerical simulations of residence time and tracer travel time in Lake Poyang. J. Lake Sci.2017,29(1):32-42. DOI:10.18307/2017.0104
|在复杂湖泊水动力环境作用下，换水周期和传输时间变化直接影响着污染物的迁移和转化.本文运用数值模拟方法，定量研究了季节水情动态下鄱阳湖换水周期和示踪剂传输时间的空间分布.结果表明，不同季节下鄱阳湖换水周期均具有较高的空间异质性，贯穿整个湖区的主河道换水周期约<10 d，大多湖湾区的换水周期则长达300多天.尽管不同季节下换水周期空间分布格局几乎相似，但受鄱阳湖水动力场的季节变化影响，夏、秋季的换水周期要明显大于春、冬季.基于换水周期频率分布曲线的统计表明，80%的鄱阳湖区的换水周期约<30 d，其余湖区换水周期为几十天至几百天，表明鄱阳湖应该更加确切地描述为一个快速换水和慢速换水同时共存的湖泊系统.鄱阳湖示踪剂传输时间介于4~32 d，夏、秋季的传输时间（11~32 d）约为春、冬季（4~8 d）的4倍，主要与鄱阳湖季节性水情特征及示踪剂的迁移路径有关.本文所获取的换水周期和示踪剂传输时间的时空分布信息可为今后鄱阳湖水质、水环境和生态系统管理和维护等方面提供重要科学参考.
|关键词: 换水周期 传输时间 空间异质性 染色示踪剂 水动力模型 鄱阳湖
|Numerical simulations of residence time and tracer travel time in Lake Poyang
LI Yunliang1, YAO Jing1, LI Mengfan1,2, ZHANG Qi1,3
1.Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, P. R. China;2.University of Chinese Academy of Sciences, Beijing 100049, P. R. China;3.Key Laboratory of Poyang Lake Wetland and Watershed Research, Ministry of Education, Jiangxi Normal University, Nanchang 330022, P. R. China
|Many physical, chemical and biological processes that occur within particular environments, including the transport of pollutants, sediments and other materials, are influenced by lake hydrodynamics. The residence time and travel time of these materials are most commonly used to represent the time scale of the physical transport processes and to elucidate associated water quality problems in lakes. The main objective of this study was to investigate the residence time and tracer travel time in Lake Poyang. A 2D hydrodynamic model (MIKE 21) was combined with dye tracer simulations (advection-dispersion equation) to determine the residence and travel time of the lake for various seasons. The results indicate that Lake Poyang exhibits strong but spatially heterogeneous residence time that varies with the different seasons. Generally, the average residence time is shorter than 10 days along the lake's main flow channels due to the prevailing northward flow pattern. Whereas the local topographically controlled flow patterns substantially increase, the residence time in most bays is approximately longer than 300 days with high spatial values. Flushing homogeneity curves show that approximately 80% of the lake area has the residence time varied between a few days and approximately 1 month, and around 20% of the area has the values in the range from several months to several hundred days. The results demonstrate that Lake Poyang is a mixing water system, which can be divided into fast and slow flushing systems in different seasons. Model simulations also reveal that the tracer travel time of Lake Poyang is in the range of 4-32 days across the lake. Depending on the seasonal water level regimes and associated pollutant transport pathways, the travel time from the released sources to the lake outlet Hukou during the summer and autumn (varies between 11-32 days) is four times greater than that under the spring and winter (i.e., 4-8 days). The outcomes of this study provide important information regarding the sustainable management of water quality, water environment and ecosystem for Lake Poyang.
|Key words: Residence time travel time spatial heterogeneous dye tracer hydrodynamic model Lake Poyang