The Eutrophication Process in a Plateau Deepwater Lake: Response to the Changes of Anthropogenic Disturbances in the Watershed

Lake eutrophication, a serious environmental issue in the world, especially in recent years. In Lake Yangzonghai, a plateau deepwater lake in China, the anthropogenic disturbances have increased the eutropication, while people has not as yet known the effects and the main contributors of this increase. Data about the eutrophication development of the lake in the past 6 years were presented in this paper. Temperature, phosphorus, pH, dissolved oxygen, nitrogen and chlorophyll-a in collected water samples were analyzed during the period of 2005-2010. Results indicate that the livestock and poultry raising instead of the agricultural fertilizer used in the watershed is the main factors to result in lake eutrophication. When the total phosphorus concentration reach to 0.027ml/l, the chlorophyll-a increase rate appears a peak, which is even more evident in drought season, when the concentration of total phosphorus is over the value, the effect of phosphorus on the lake eutrophication may become smaller and smaller. This study put forward the relationship between the anthropogenic disturbances and the eutrophication in plateau deepwater lakes, which also provided basic data for organic pollution control and ecological risk assessment of the lake.