Influence factors on hydrodynamics field in Xiangxi Bay of Three Gorges Reservoir, China

Hydrodynamic play an important role in eutrophication and algae bloom in Xiangxi Bay (XXB), which was the former Xiangxi River prior to the construction of the Three Gorges Reservoir (TGR). Field surveys show that the dominant species of rotifers in XXB changed considerably at the onset of the reservoir impoundment. Because of the change of hydrodynamic in XXB, a phytoplankton bloom was observed during the spring after TGR was impounded. Hydrodynamic distribution become very important in the phytoplankton bloom study and control in XXB. As it is difficult to obtain sufficient hydrodynamic information by field monitoring, a three-dimensional hydrodynamic model is developed in this paper to study the hydrodynamics distribution of XXB during spring. The study shows that water level of Three Gorges Dam(TGD) is the key factor to hydrodynamic distribution in XXB. The current situation of XXB only slight influence the upstream of XXB. The change of water level at TGD has little impact on the whole bay. Specifically, the influence of thermal density currents play an important role of the hydrodynamic distribution in XXB mouth. The study of influence factors on hydrodynamics field will help to clearly understand of algae bloom phenomenon in XXB, and also could provide technical support to the control of eutrophication and algae bloom in XXB and other bays of TGR.