Is Portage Lake Safe for Swimming?
Portage Lake in Cass County, Minnesota has a water quality grade of C (Fair). Generally safe for swimming, moderate water quality. Water clarity: 7.5 ft visibility. Phosphorus: 22 µg/L. Chlorophyll-a (algae): 7.1 µg/L. Always check local health department advisories before swimming.
Key Metrics
| Metric | Value |
|---|---|
| Overall Grade | C (Fair) |
| Water Clarity (Secchi Depth) | 7.5 ft |
| Phosphorus | 22 μg/L |
| Chlorophyll-a (Algae) | 7.1 μg/L |
| Maximum Depth | 55 ft |
| Location | Cass County, Minnesota |
How does Portage Lake compare?
With an overall water quality grade of C, Portage Lake matches or beats the Minnesota state average of Grade C. It ranks #88 of 104 lakes in Cass County by water quality score.
Water clarity (Secchi depth) sits at 7.5 feet. That puts the lake in good clarity range, with limited algae interference. Algae levels (chlorophyll-a) measure 7.1 µg/L — moderate; acceptable for swimming on most days, but worth checking advisories.