How Clean Is Marion Lake?
Marion Lake is among the cleanest lakes in Minnesota. It received a water quality grade of A (Excellent) based on EPA monitoring data. Water clarity (Secchi depth): 7 ft. Phosphorus: 20 µg/L. Chlorophyll-a (algae): 4.6 µg/L. Trophic State Index: 47.
Cleanliness Snapshot
| Metric | Marion Lake | Minnesota avg |
|---|---|---|
| Overall Grade | A | C |
| Water Clarity (Secchi) | 7 ft | — |
| Phosphorus | 20 µg/L | <30 = clean |
| Chlorophyll-a (Algae) | 4.6 µg/L | <10 = clean |
| Trophic State Index | 47 | <50 = clean |
How does Marion Lake compare?
Marion Lake's grade of A matches or beats the Minnesota state average of C. It ranks #1 of 45 lakes in Dakota County by water quality score. Multi-year monitoring data shows water quality is stable based on 4 years of records.