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Evolution Process and influence Factors of Dianchi Lake Water Pollution

Dianchi Lake, located in Yunnan Province, China, has encountered eutrophication since the 1970s. This study mainly discusses the evolution process and reasons for Dianchi lake pollution in the 21st century. In the long-term treatment, the water quality of Dianchi Lake gets worse. The comprehensive pollution index of Caohai in the north of Dianchi Lake reached its peak in 2009 and then declined rapidly. The gap between Caohai and the south offshore sea gradually narrowed. Later, the phenomenon of water quality in the north of Dianchi Lake was better than that in the south. On the whole, however, the water quality of the Waihai is still better than that of the Caohai. The factors of Dianchi lake water pollution are mainly divided into internal and external factors. The internal factors are the semi-enclosed lake and the increase in temperature. The main external factors are precipitation and urbanization. With the development of urbanization and industrialization, more and more surface pollutants flow into Dianchi Lake along with surface runoff formed by precipitation. Due to the influence of internal factors, the existing pollutants in Dianchi Lake are difficult to discharge and release more toxic substances and nutrients. Under the dual action of internal and external factors, the pollutants in Dianchi Lake water continuously accumulate, resulting in serious pollution of Dianchi Lake water.