Spatial and temporal analysis of water quality conditions in low-latitude plateau lakes

As a typical low-latitude plateau lake, the water quality category of Dianchi lake is Ⅳ in 2023, the water quality category of the Waihai is Ⅴ, and the water quality category of the Caohai is Ⅳ, and the nutrient status is moderately eutrophic. From the main indicators of monthly concentration change analysis, the Waihai, the Caohai in January-April, November-December water quality status is relatively stable, into the rainy season (May-October) after the water quality status has declined, Dianchi lake overall from the integrated trophic state index presents the north is the highest. From the comprehensive pollution index, it can be seen that the Caohai is significantly lower than the Waihai, showing that the pollution in the north is lower than that in the center and south. Since the new era (2013-2023), Dianchi lake-wide water quality has generally improved, since 2016 from 2015 inferior class V improved to class V, in 2018 the water quality category rose to class Ⅳ. 2013-2023, Dianchi lake-wide chemical oxygen demand, ammonia nitrogen, total phosphorus, integrated trophic state index, integrated pollution index showed a significant decreasing trend, total nitrogen showed a decreasing trend. We comprehensively analyzed the characteristics and reasons for the monthly, annual, and spatial and temporal changes in water quality of Dianchi lake in the past ten years, and finally put forward suggestions for the management of Dianchi lake in the light of the existing water quality, so as to provide scientific theoretical basis for the protection of typical low-latitude plateau lakes and the prevention of lake pollution.