Water quality classification	Water quality	Characterization of color	Functions
I-Type and II-Type water	Superior	Blue	Grade I relate to source water and national nature reserves. Grade II includes primary protection areas for centralized drinking water sources, precious fish sanctuaries, fish and shrimp spawning grounds, etc.
III-Type	Good	Green	Grade III relates to secondary protection areas for centralized drinking water sources and general fish protection and swimming areas.
IV-Type	Mild pollution	Yellow	Grade IV applies to general industrial and recreational water areas where there is direct human contact.
V-Type	Moderate pollution	Orange	Grade V refers to agricultural water use areas and waters with general landscape requirements.
Inferior V-Type	Severe pollution	Red	Apart from adjusting to the local climate, the inferior V-Type is poorly functional.