Abstract: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.