Rank

Category

Explanation

95 - 100

Excellent

water quality is protected with a virtual absence of threat or impairment; conditions very close to natural or pristine levels

80 - 94

Good

water quality is protected with only a minor degree of threat or impairment; conditions rarely depart from natural or desirable levels

65 - 79

Fair

water quality is usually protected but occasionally threatened or impaired; conditions sometimes depart from natural or desirable levels

45 - 64

Marginal

water quality is frequently threatened or impaired; conditions often depart from natural or desirable levels

0 - 44

Poor

water quality is almost always threatened or impaired; conditions usually depart from natural or desirable levels