2004 Assessment. Generalized description of macroinvertebrate communities associated with health tiers. These are not criteria, but rather descriptions based on averages calculated from many samples. Characteristics of individual samples can vary.

Very good	Approaching natural conditions. The macroinvertebrate community is robust and diverse, and includes many organisms intolerant of stresses caused by human activity.
Fair	Somewhat degraded. The macroinvertebrate community is fairly healthy, but, relative to “very good”, the variety of sensitive organisms is reduced, and the population proportion of organisms tolerant of human-caused stresses has increased.
Poor	Significantly degraded. The macroinvertebrate community is obviously impacted. The population proportion of stress-tolerant organisms has increased a great deal. Sensitive organisms may be present, but in much smaller numbers.
Very poor	Severely degraded. The macroinvertebrate community contains very few types of organisms, virtually all of which are tolerant of human-caused stresses.