Is Colby Lake Safe for Swimming?
Colby Lake in St. Louis County, Minnesota has a water quality grade of A (Excellent). Excellent for swimming, crystal clear water with minimal algae. Water clarity: 3 ft visibility. Phosphorus: 22 µg/L. Chlorophyll-a (algae): 3.2 µg/L. Always check local health department advisories before swimming.
Key Metrics
| Metric | Value |
|---|---|
| Overall Grade | A (Excellent) |
| Water Clarity (Secchi Depth) | 3 ft |
| Phosphorus | 22 μg/L |
| Chlorophyll-a (Algae) | 3.2 μg/L |
| Maximum Depth | 30 ft |
| Location | St. Louis County, Minnesota |
How does Colby Lake compare?
With an overall water quality grade of A, Colby Lake matches or beats the Minnesota state average of Grade C. It ranks #3 of 68 lakes in St. Louis County by water quality score.
Water clarity (Secchi depth) sits at 3 feet. That falls into moderate clarity — typical for lakes with some nutrient enrichment. Algae levels (chlorophyll-a) measure 3.2 µg/L — low and well within safe swimming guidelines.