Is Otter Lake Safe for Swimming?
Otter Lake in Macoupin 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: 1.8 ft visibility. Phosphorus: 81 µg/L. Chlorophyll-a (algae): 33.1 µg/L. Always check local health department advisories before swimming.
Key Metrics
| Metric | Value |
|---|---|
| Overall Grade | F (Algae-prone) |
| Water Clarity (Secchi Depth) | 1.8 ft |
| Phosphorus | 81 μg/L |
| Chlorophyll-a (Algae) | 33.1 μg/L |
| Location | Macoupin County, Illinois |
How does Otter Lake compare?
With an overall water quality grade of F, Otter Lake falls below the Illinois state average of Grade D. It ranks #2 of 3 lakes in Macoupin County by water quality score.
Water clarity (Secchi depth) sits at 1.8 feet. That signals heavy algae or sediment, often tied to high phosphorus from runoff. Algae levels (chlorophyll-a) measure 33.1 µg/L — elevated; risk of harmful algal bloom advisories increases at this concentration.
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