Is Mattoon Lake Safe for Swimming?
Mattoon Lake in Cumberland County, Illinois has a water quality grade of F (Algae-prone). Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom. Water clarity: 1.3 ft visibility. Phosphorus: 294 µg/L. Chlorophyll-a (algae): 87.1 µg/L. Always check local health department advisories before swimming.
Key Metrics
| Metric | Value |
|---|---|
| Overall Grade | F (Algae-prone) |
| Water Clarity (Secchi Depth) | 1.3 ft |
| Phosphorus | 294 μg/L |
| Chlorophyll-a (Algae) | 87.1 μg/L |
| Location | Cumberland County, Illinois |
How does Mattoon Lake compare?
With an overall water quality grade of F, Mattoon Lake falls below the Illinois state average of Grade D. It ranks #1 of 1 lakes in Cumberland County by water quality score.
Water clarity (Secchi depth) sits at 1.3 feet. That signals heavy algae or sediment, often tied to high phosphorus from runoff. Algae levels (chlorophyll-a) measure 87.1 µg/L — elevated; risk of harmful algal bloom advisories increases at this concentration.
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