The
Minnehaha Creek Watershed District’s water quality lake grading method
was developed in 1989. The lake grade shows how one lake measures up
compared to other area lakes and indicates the perceived condition of
the open water. Three water quality measurements are combined to create
each lake grade.
However, there are also other factors that contribute to lake
condition, including precipitation. aquatic plants, fisheries, harmful
chemicals, and over-use.
Understanding Lake Water Quality Grades
The
grades consider what is average or normal for lakes in a given area.
What is a “C” in one part of the country might not be a “C” elsewhere. However, within the seven-county metro area, grades can be compared.
| Lake Grade | Relative Ranking | Description |
| A | 90% and up | Crystal clear, beautiful. These lakes are exceptional and can be enjoyed by recreation users without question or hesitation. |
| B | 70 - 90% | Generally good water quality but algae may limit swimming, particularly toward the end of the summer.
|
| C | 30 - 70% | Average quality. Swimming, boating, and fishing may be undesirable relatively early in the season. Algae blooms occasionally.
|
| D | 10 - 30% | Severe algae problems. People are generally not interested in recreation on these lakes.
|
| F | Lowest 10% | Not enjoyable. The lake would have severe limitations to recreational use.
|
