Is Otter Lake Safe for Swimming?
Otter Lake in Macoupin County, Illinois has nutrient and algae measurements on record from state and federal monitoring. Chlorophyll-a in the monitoring record runs high enough that algae is a factor. A water-quality reading is not a swimming clearance. The state water agency and county health departments post current advisories; check them before you swim.. 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 |
|---|---|
| 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?
On nutrient and algae readings, Otter Lake runs above the Illinois state average. It ranks #2 of 3 lakes in Macoupin County on nutrient and algae readings.
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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