Trend Analysis of the Variation of Total Phosphorus and Total Nitrogen of Nanpan River, Yunnan

Based on the water quality monitoring data from 2014 to 2021, this paper selected 13 monitoring sections with complete data to analyze and evaluate the water quality status and change trend of Nanpan River in Yunnan Province. The results showed that the water quality of the monitoring section was mainly class I ～ III water quality specified in the environmental quality standard for surface water(GB3838-2002). Among them, Gongjiaba section was the most polluted in the whole year. From 2020 to 2021, the pollution of Goujie section was mainly class V and inferior to class V. The water quality of the entrance section of Huashan reservoir from 2015 to 2017 was classified as class II, which failed to meet the target water quality. The water quality of other sections met the target water quality standard.Total phosphorus was the main item exceeding the standard in the basin, followed by ammonia nitrogen. Domestic sewage and agricultural production pollution were the main factors causing water pollution in the Nanpan River Basin.