Sub-theme
4. Supporting Aquatic Ecosystem Health and Functions
Topic
4-1. The ecological health of rivers and lakes
Body
Globally, large shallow lakes are challenged by eutrophication and water quality deterioration problems caused by climate change and increasing human activities. The consequential algal bloom events threaten the environmental functions of shallow lakes and the drinking water security around them, posing a great health risk to both human and aqua lives. Accordingly, risk assessment of algae accumulation and identification of the hotspots prone to the accumulation show the importance on a better lake littoral zone management practice. Previous studies have shown the contribution of wind condition, hydrodynamics, phytoplankton biomass, and complex geometry of large shallow lakes on algae transportation and bloom formation, however, less attention was paid to the relation of algal accumulation and the influencing factors. In this study, Taihu Lake, the 3rd largest shallow lake in China with a complex geometry of eight subbasins, is chosen as an example to reveal the algae accumulation under multi influencing factors. Firstly, a 3-dimensional Delft3D Taihu Lake model is setup and calibrated to study the wind induced hydrodynamics. Secondly, the representing phytoplankton biomass is achieved via satellite images. Thirdly, an index representing the risk of algae accumulation is established for the lake’s littoral zone, with the consideration of wind induced hydrodynamics, the algae biomass and lake geometry. The distribution of the algae accumulation index shows that the northwestern littoral region of Taihu Lake is more prone to the threat of algae accumulation, including the northwestern zone of Zhushan Bay and Meiliang Bay, littoral zone between the entrance of the two subbasins and the west coast of Taihu Lake. The algae accumulation risk presents a generally decreasing trend from the northwest to the southeast of Taihu Lake, where the most severe risk zone was on the northwest subbasins. The algae accumulation index proposed in this study shows the capability as an effective indicator of algae bloom risks in large shallow lakes, providing support for lakes’ decision-makers all over the world.