Is Green Castle Lake Safe for Swimming?
Green Castle Lake in Marshall County, Wisconsin has a water quality grade of C (Fair). Generally safe for swimming, moderate water quality. Water clarity: 4.6 ft visibility. Chlorophyll-a (algae): 6.9 µg/L. Always check local health department advisories before swimming.
Key Metrics
| Metric | Value |
|---|---|
| Overall Grade | C (Fair) |
| Water Clarity (Secchi Depth) | 4.6 ft |
| Chlorophyll-a (Algae) | 6.9 μg/L |
| Location | Marshall County, Wisconsin |
How does Green Castle Lake compare?
With an overall water quality grade of C, Green Castle Lake matches or beats the Wisconsin state average of Grade D. It ranks #2 of 2 lakes in Marshall County by water quality score.
Water clarity (Secchi depth) sits at 4.6 feet. That falls into moderate clarity — typical for lakes with some nutrient enrichment. Algae levels (chlorophyll-a) measure 6.9 µg/L — low and well within safe swimming guidelines.