MA Wei, SU Jianguang, YANG Yang, JIANG Rucheng, WU Jinhai

Abstract: Erhai Lake is the main drinking water source of Bai people in Dali. As a result,  the lake is characterized by relatively good water quality in dry season and serious pollution problem during the rainy season, evident interannual fluctuation of water quality, and gradually increasing trend of eutrophication. Among those factors,  the agricultural non-point source pollution is the key factor that results in the water quality exceeding the limit during the rainy seasons, rainfall runoff is the main carrier of pollutants into the lake, the hydrological regime is the key driving factor affecting the annual variation of water quality in Erhai Lake, the natural restoration of submerged vegetation in lakeside zone is restricted by the water level of scheduling control,  and the decaying aquatic vegetation is an important factor affecting sudden changes of water quality in May and June. Therefore, measures, such as carrying water from other basin to Erhai lake, controlling the agricultural non-point source pollution, strengthening the end interception of pollutants by the ecological storage zones and the scientific level of aquatic plant harvesting management, and optimizing the water level scheduling, are the keys ways to achieve the sustainable improvement of the water quality and water ecosystem of Erhai Lake.

Keywords: evolution characteristics of water quality, environmental impact factors  lake inflow, water level regulation, non-point pollutant, ecological storage zones, Erhai Lake