Ministry of Ecology and Environment Announces National Surface Water Environmental Quality Conditions for the Second Quarter and January-June 2024

　　In the second quarter, among the 3641 national surface water assessment sections, the proportion of sections with good water quality (Class I-III) was 84.8%, up 0.8 percentage points year-on-year; the proportion of sections with poor Class V was 0.9%, down 0.2 percentage points year-on-year. The main pollution indicators are chemical oxygen demand, permanganate index and total phosphorus.

　　From January to June, 3641 national surface water assessment section, water quality is good (Ⅰ - Ⅲ) section proportion of 88.8%, up 1.0 percentage points; the proportion of inferior V section is 0.8%, down 0.2 percentage points year-on-year. The main pollution indicators are chemical oxygen demand, permanganate index and total phosphorus.

Figure 1 Proportion of surface water quality categories nationwide, January-June

　　In the second quarter, the Yangtze River, the Yellow River, the Pearl River, the Songhua River, the Huaihe River, the Haihe River, the Liaohe River and other seven major watersheds and the Northwest rivers, the Southwest rivers and rivers in Zhejiang and Fujian piece of good water quality (Ⅰ - Ⅲ) section proportion of 86.0%, up 0.7 percentage points; the proportion of poor V section of 0.7%, a year-on-year decline of 0.1 percentage points. The main pollution indicators for chemical oxygen demand, permanganate index and five-day biochemical oxygen demand. Among them, the northwestern rivers, southwestern rivers, the Yangtze River Basin and Zhejiang and Fujian piece of river water quality is excellent; Pearl River, Yellow River and Liaohe River Basin water quality is good; Huaihe River, Haihe River and Songhua River Basin is mildly polluted.

　　January to June, the Yangtze River, the Yellow River, the Pearl River, the Songhua River, the Huaihe River, the Haihe River, the Liaohe River and other seven major watersheds and the Northwest rivers, the Southwest rivers and the Zhejiang and Fujian piece of the river with excellent water quality (Ⅰ - Ⅲ) section proportion of 90.3%, up 1.2 percentage points; the proportion of poor V section of 0.5%, a decline of 0.2 percentage points. The main pollution indicators for chemical oxygen demand, permanganate index and five-day biochemical oxygen demand. Among them, Zhejiang and Fujian rivers, the northwest rivers, the Yangtze River Basin, the Pearl River Basin and the southwest rivers water quality is excellent; the Yellow River, Liaohe, Huaihe and Haihe River Basin water quality is good; Songhua River Basin is mildly polluted.

Figure 2 Proportion of water quality categories in the seven major basins and rivers in the southwest and northwest of the country and rivers in the Zhejiang and Fujian slices from January to June

　　In the second quarter, 210 key lakes (reservoirs) monitored, the number of lakes and reservoirs with good water quality (Ⅰ - Ⅲ) accounted for 78.1%, a year-on-year decline of 1.2 percentage points; the number of lakes and reservoirs with poor V water quality accounted for 4.3%, a year-on-year decline of 0.5 percentage points. The main pollution indicators for total phosphorus, chemical oxygen demand and permanganate index. 198 monitoring nutrient status of the lake (library), heavy eutrophic 1, accounting for 0.5%; moderate eutrophic 6, accounting for 3.0%; mildly eutrophic 36, accounting for 18.2%; the rest of the lake (library) for the middle nutrient or anaerobic state. Among them, the water quality of Taihu Lake is good and mildly eutrophic; Chaohu Lake is mildly polluted and mildly eutrophic, and the main pollution indicator is total phosphorus; Dianchi Lake is moderately polluted and moderately eutrophic, and the main pollution indicators are COD, total phosphorus and permanganate index; the water quality of Erhai Sea and Baiyangdian is good and moderately eutrophic; and the water quality of Danjiangkou Reservoir is excellent and moderately eutrophic.

　　From January to June, the monitoring of 210 key lakes (reservoirs), water quality excellent (Ⅰ - Ⅲ) lakes and reservoirs accounted for 79.5%, down 0.8 percentage points; inferior V water quality lakes and reservoirs accounted for 4.3%, down 1.0 percentage points. The main pollution indicators for total phosphorus, chemical oxygen demand and permanganate index. 201 monitoring nutrient status of the lake (library), heavy eutrophic 1, accounting for 0.5%; moderate eutrophic 7, accounting for 3.5%; mildly eutrophic 37, accounting for 18.4%; the rest of the lake (library) for the middle nutrient or anaerobic state. Among them, the water quality of Taihu Lake is good and mildly eutrophic; Chaohu Lake is mildly polluted and mildly eutrophic, and the main pollution indicator is total phosphorus; Dianchi Lake is moderately polluted and moderately eutrophic, and the main pollution indicators are COD, total phosphorus and permanganate index; the water quality of Erhai Sea and Baiyangdian is good and moderately eutrophic; and the water quality of Danjiangkou Reservoir is excellent and moderately eutrophic.

Table 1 Water quality and trophic status of six lakes (reservoirs) from January to June

Figure 3 Water quality and trophic status of six lakes (reservoirs) from January to June