WQI

Class

Uses

>92.7

Class I

Conservation of natural environment Water supply I―practically no treatment necessary

Fishery I―very sensitive aquatic species

76.5 - 92.7

Class IIA

Water supply II―conventional treatment required

Fishery II―sensitive aquatic species

Class IIB

Recreational use with body contact

51.9 - 76.5

Class III

Water supply III―extensive treatment required

Fishery III―common economic value and species tolerant: livestock drinking

31.0 - 51.9

Class IV

Irrigation

<31.0

Class V

None of the above