River water quality share in China 2018-2023, by level

According to Surface Water Environment Quality Standards of China, the water quality is categorized as follows:

Grade I: Source water and national nature reserve; Grade II: Drinking water and surface water source primary protection zone; Grade III: Drinking water and surface water source secondary protection zone; Grad IV: Industrial water use and recreational water use; Grade V: Agricultural water use and General landscape requirements.

Low quality surface water refers to surface water worse than Grade V.

The surveyed rivers include: overall water quality of major rivers in the seven major river basins, rivers in Zhejiang and Fujian, rivers in the northwest, and rivers in the southwest.