Time and Spatial Changes of Water Quality in Wushan Area of Three Gorges Reservoir before and after 170 Meters Pilot Impounding

The investigation is determined in two tributaries of Three Gorges Reservoir in three seasons from 2006 to 2009.The results showed that the variation of the hydrological elements results in eutrophication of water in the reservoir.However,Impacts of hydrological elements on the eutrophication of different water bodies are different.The mainstream of the Yangtze River is oligotrophic and mesotrophic,while backwater of some tributaries is tutrophic and algal bloom exists potentially.