1. First of all, with the increase of rainfall in Yunnan in rainy season, a large amount of rainwater will flow into Erhai Lake, which will bring a lot of sediment, nutrients and organic matter at the same time. These substances accumulate in water, forming a large number of growth and reproduction of plankton, algae and other algae, resulting in poor water quality.
2. Secondly, in the rainy season, the temperature and humidity gradually increase, the biological metabolism in water is accelerated, and the solubility and oxygen content of nutrients will also change. These factors will make the organic matter and nutrients in water more easily oxidized and decomposed, resulting in poor water quality.
Thirdly, in the rainy season, the degree of agriculture and urbanization around Erhai Lake gradually increased, leading to sewage and agricultural pollutants entering Erhai Lake. These organic substances and nutrients will provide more conditions for the growth and reproduction of organisms in water, resulting in the deterioration of water quality.