Analysis of Spatial and Temporal Patterns and Main Controlling Factors for Algal Growth in the Pengxi River of the Three Gorges Reservoir, China

Since the first water impoundment of the Three Gorges Project (TGP) in June 2003, the Three Gorges Reservoir has suffered from eutrophication risks. To enhance water environment management in the Three Gorges Reservoir Area (TGRA), it is urgent to develop a basin-scale three-dimensional (3D) eutrophication model to accurately simulate the dynamic processes of phytoplankton growth and identify the main controlling factors that influence algal blooms in tributary bays. The model is distinguished from the current models by taking complicated and remarkable interactions between upstream and downstream into account and including non point source pollution loading of river basins in view of basin scale. The model was calibrated and validated by TN, TP and chlorophyll-a (Chia), and the simulation results showed that the simulation values basically correlated with the measured data with a relative error within 30%. The three-dimensional disfribution of algae at different times of one day and the spatial algal disfribution in the Pengxi River were simulated. The potential factors that influence algal growth and losses such as water temperature, light and hydrodynamic conditions were identified. The results will be beneficial for water environment management, and the model may be used for algal bloom forecasts as well as water quality protection and management in the TGRA.