How Clean Is Mary Lake?
Mary Lake is a clean lake by Minnesota standards. It received a water quality grade of B (Good) based on EPA monitoring data. Water clarity (Secchi depth): 9.8 ft. Phosphorus: 19 µg/L. Trophic State Index: 45.
Cleanliness Snapshot
| Metric | Mary Lake | Minnesota avg |
|---|---|---|
| Overall Grade | B | C |
| Water Clarity (Secchi) | 9.8 ft | — |
| Phosphorus | 19 µg/L | <30 = clean |
| Trophic State Index | 45 | <50 = clean |
How does Mary Lake compare?
Mary Lake's grade of B matches or beats the Minnesota state average of C. It ranks #28 of 51 lakes in Douglas County by water quality score. Multi-year monitoring data shows water quality is improving based on 5 years of records.