The key technologies for eutrophication simulation and algal bloom prediction in Lake Taihu, China

An integrated system including eutrophication simulation and algal bloom predication was established and applied in Lake Taihu. The mechanic models, which are based on a three-dimensional numerical model coupling hydrodynamic module, pollutant transport module, suspended sediment resuspension module, wind wave module and algal bloom predication module, can simulate not only the single function such as current pattern, nutrient distribution, sediment concentration and wave height field, but also the interaction among them. Using these models, some complex phenomenon such as endogenous pollution can be simulated. In the study, some key technologies are introduced to make the simulation reasonable and feasible. First, a new method for predicting algal bloom is introduced. Differing from the traditional phytoplankton dynamic model, judging the algal bloom through biomass or chlorophyll concentration, the method quantitatively estimates algal growth state switching among bloom, collapse and steady based on algal stability criterion in water column. Second, the sediment resuspension is estimated using calibrated critical shear stresses derived from remote sensing data and the wave-enhanced bottom stress during the windy days. Third, a user-friendly operation environment based on plug-in development and geographic information system is developed. The tests demonstrated that the system could both simulate the reactive solutes such as BOD and DO and the suspended sediment correctly under interaction of gravity and turbulent diffusion. The simulation results demonstrated that the system could obtain reasonable and reliable simulated results in Lake Taihu.