Johnson Lake
Henry County, Illinois56 acresView mapDirections
No nutrient or algae sampling on record from Illinois EPA for this lake.
- Impaired · Mercury
- 23 ft max depth
Johnson Lake in Henry County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Maximum depth: 23 ft. Surface area: 56 acres.
Johnson Lake is a 56-acre lake in Henry County, Illinois with a maximum depth of 23 feet (8-foot average).
Source: EPA Water Quality Portal sampling records, Illinois EPA. Methodology: how these readings are compared.
Swimming conditions
No readingNot rated
Nutrient and algae readings are not a swimming clearance. Johnson Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen), turbidity. Check local advisories before you swim.
Whether Johnson Lake is safe to swim in today is a call for the Illinois Environmental Protection Agency and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Johnson Lake
These are the measurements Illinois EPA publishes for Johnson Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. TSI undefined.
Ask about Johnson Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
23 ft
Average depth
8.2 ft
Surface area
56 acres
Shoreline
2 mi
Stays via Stay22
Stays near Johnson Lake
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Fishing Johnson Lake
EPA Impairment Status
Johnson Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Fish consumption, Other.
Source: EPA ATTAINS assessment unit IL_RPD · Official waterbody report
Nearby Lakes in Henry County
Frequently asked questions about Johnson Lake
Where is Johnson Lake?
- Johnson Lake is a lake in Henry County, Illinois. Its water-quality measurements are published by Illinois EPA and shown on this page as reported.
What is the water quality of Johnson Lake?
- Johnson Lake in Henry County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Maximum depth: 23 ft. Surface area: 56 acres.
Is Johnson Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Johnson Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen), turbidity. Check local advisories before you swim.
How deep is Johnson Lake?
- Johnson Lake has a maximum depth of 23 feet and an average depth of 8.2 feet. The lake covers 56 acres.
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Where this data comes from
Measurements for Johnson Lake come from the EPA Water Quality Portal. Per-sample source details are not recorded for this lake.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database