Is Island Lake Safe for Swimming?
Island Lake in Mahnomen County, Minnesota has a water quality grade of F (Very Poor). Avoid swimming, very poor water quality, potential algae toxins. Water clarity: 4.5 ft visibility. Phosphorus: 30 µg/L. Chlorophyll-a (algae): 34.3 µg/L. Always check local health department advisories before swimming.
Key Metrics
| Metric | Value |
|---|---|
| Overall Grade | F (Very Poor) |
| Water Clarity (Secchi Depth) | 4.5 ft |
| Phosphorus | 30 μg/L |
| Chlorophyll-a (Algae) | 34.3 μg/L |
| Maximum Depth | 43 ft |
| Location | Mahnomen County, Minnesota |
How does Island Lake compare?
With an overall water quality grade of F, Island Lake falls below the Minnesota state average of Grade C. It ranks #12 of 12 lakes in Mahnomen County by water quality score.
Water clarity (Secchi depth) sits at 4.5 feet. That falls into moderate clarity — typical for lakes with some nutrient enrichment. Algae levels (chlorophyll-a) measure 34.3 µg/L — elevated; risk of harmful algal bloom advisories increases at this concentration.