Is Johnson Lake Safe for Swimming?
Johnson Lake in St. Louis County, Minnesota has nutrient and algae measurements on record from state and federal monitoring. 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: 3 ft visibility. Phosphorus: 33 µg/L. Chlorophyll-a (algae): 9.8 µg/L. Always check local health department advisories before swimming.
Key Metrics
| Metric | Value |
|---|---|
| Water Clarity (Secchi Depth) | 3 ft |
| Phosphorus | 33 μg/L |
| Chlorophyll-a (Algae) | 9.8 μg/L |
| Maximum Depth | 18 ft |
| Location | St. Louis County, Minnesota |
How does Johnson Lake compare?
With an overall water-quality readings of —, Johnson Lake matches or beats the Minnesota state average. It ranks #50 of 68 lakes in St. Louis County by water quality score.
Water clarity (Secchi depth) sits at 3 feet. That falls into moderate clarity — typical for lakes with some nutrient enrichment. Algae levels (chlorophyll-a) measure 9.8 µg/L — moderate; acceptable for swimming on most days, but worth checking advisories.
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