Otter Lake
Macoupin County, Illinois419 acresView mapDirections
No nutrient or algae sampling on record from Illinois EPA for this lake.
- Impaired · Mercury
- 50 ft max depth
Otter Lake in Macoupin County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Maximum depth: 50 ft. Surface area: 419 acres.
Otter Lake is a 419-acre lake in Macoupin County, Illinois with a maximum depth of 50 feet (20-foot average).
Source: EPA Water Quality Portal sampling records, Illinois EPA. Methodology: how these readings are compared.
What Otter Lake is good for
From access and monitoring records, not editorial picks.
- Deep water50 ft surveyed max depth
Swimming conditions
No readingNot rated
Nutrient and algae readings are not a swimming clearance. Otter Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Otter 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 Otter Lake
These are the measurements Illinois EPA publishes for Otter 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 Otter Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
50 ft
Average depth
19.7 ft
Surface area
419 acres
Shoreline
18.4 mi
Stays via Stay22
Stays near Otter Lake
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Fishing Otter Lake
EPA Impairment Status
Otter 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.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IL_RDF · Official waterbody report
Nearby Lakes in Macoupin County
Frequently asked questions about Otter Lake
Where is Otter Lake?
- Otter Lake is a lake in Macoupin County, Illinois. Its water-quality measurements are published by Illinois EPA and shown on this page as reported.
What is the water quality of Otter Lake?
- Otter Lake in Macoupin County, Illinois has water-quality measurements published by Illinois EPA, shown here as reported. Maximum depth: 50 ft. Surface area: 419 acres.
Is Otter Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Otter Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
How deep is Otter Lake?
- Otter Lake has a maximum depth of 50 feet and an average depth of 19.7 feet. The lake covers 419 acres.
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Where this data comes from
Measurements for Otter 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