Wind effects on hydrodynamics and implications for ecology in a hydraulically dominated river-lake floodplain system: Poyang Lake

Abstract

The wind forcing effects on mixing dynamics and circulation can drive important bio-hydrodynamic interactions in certain regions of a hydraulically dominated river-lake floodplain system. Poyang Lake, connected with the Yangtze River, is an example of such a system. The wind forcing effects on Poyang Lake have not been assessed in detail. In this study, a hydrodynamic model and a current energy method were used to investigate the hydrodynamic pattern forced by the combination of hydraulic and wind drivers and to distinguish both forcings. Two prevailing wind directions (NNE and SSW) with 3 wind-speed (3 m/s, 5 m/s and 10 m/s) scenarios, including tracer transport and residence time, were further simulated to determine the wind effects. The results showed that there are distinct hydraulic-dominated and wind-dominated regions. In the three wind-dominated zones, various circulation patterns were determined by the wind direction and complex geometry, and current speeds were positively correlated with the wind speed magnitude, regardless of wind direction. However, residence times responded differently to wind forcings. The low-speed NNE wind forcing was found to be the most disadvantageous for mixing and dispersion and was prone to allowing material enrichment in the eastern sub-lakes. An improved understanding of ecological behaviour in local zones of Poyang Lake is provided to guide future water management.