How Clean Is Mary Lake?
Mary Lake is among the cleanest lakes in Minnesota. Its nutrient and algae readings come from EPA monitoring data. Water clarity (Secchi depth): 10.5 ft. Phosphorus: 20 µg/L. Chlorophyll-a (algae): 5.5 µg/L. Trophic State Index: 46.
Cleanliness Snapshot
| Metric | Mary Lake | Minnesota avg |
|---|---|---|
| Water Clarity (Secchi) | 10.5 ft | — |
| Phosphorus | 20 µg/L | <30 = clean |
| Chlorophyll-a (Algae) | 5.5 µg/L | <10 = clean |
| Trophic State Index | 46 | <50 = clean |
How does Mary Lake compare?
Mary Lake's readings match or beat the Minnesota state average. It ranks #11 of 37 lakes in Douglas County on nutrient and algae readings. Multi-year monitoring data shows water quality is improving based on 6 years of records.
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