Is Lake Marseilles-Terre du Lac Lakes Safe for Swimming?
Lake Marseilles-Terre du Lac Lakes in St. Francois County, Wisconsin has a water quality grade of A (Excellent). Excellent for swimming, crystal clear water with minimal algae. Water clarity: 14.1 ft visibility. Phosphorus: 7.4 µg/L. Chlorophyll-a (algae): 2.4 µg/L. Always check local health department advisories before swimming.
Key Metrics
| Metric | Value |
|---|---|
| Overall Grade | A (Excellent) |
| Water Clarity (Secchi Depth) | 14.1 ft |
| Phosphorus | 7.4 μg/L |
| Chlorophyll-a (Algae) | 2.4 μg/L |
| Location | St. Francois County, Wisconsin |
How does Lake Marseilles-Terre du Lac Lakes compare?
With an overall water quality grade of A, Lake Marseilles-Terre du Lac Lakes matches or beats the Wisconsin state average of Grade C. It ranks #2 of 4 lakes in St. Francois County by water quality score.
Water clarity (Secchi depth) sits at 14.1 feet. That counts as exceptional clarity — sunlight penetrates deep, supporting submerged plants and limiting algae. Algae levels (chlorophyll-a) measure 2.4 µg/L — low and well within safe swimming guidelines.