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 |