Major lake water quality in China 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.