Otter Lake
Macoupin County, WisconsinEutrophic
Otter Lake is a 760-acre productive, nutrient-rich eutrophic lake in Macoupin County, IL. Water quality is graded D based on 2 sampling years through 2022. Compared to the 2 other monitored lakes in Macoupin County, Otter Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2022-11-02. Grade methodology: LakeGrade methodology.
Swimming Safety
Swimming not recommended, poor water quality with high algae risk
Water Quality Grade: D, Poor
Very murky, less than 1.8 ft of visibility. Phosphorus level: 37 µg/L. Trophic State Index: 62.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.8 ft | F |
| Phosphorus | 37 µg/L | C |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 62 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 760 acres |
Location
County Ranking
Ranked #2 of 3 lakes in Macoupin County
Nearby Lakes in Macoupin County
More Wisconsin Lake Rankings
Other Grade D Lakes in Wisconsin
Eutrophic Lakes in Wisconsin
Reservoir Info (USACE NID)
Otter Lake is a man-made reservoir impounded by the Otter Lake Dam (completed 1969), built primarily for recreation on the WEST FORK OTTER CREEK; earth-type dam, 71 ft tall and 1,010 ft long.
- Surface area
- 760 ac
- Normal storage
- 15,563 ac-ft
- Max storage
- 24,708 ac-ft
- Drainage area
- 20.2 sq mi
- Hazard class
- Significant
- Owner
- OTTER LAKE WATER COMMISSION
All listed purposes: Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID IL00133 · Operator website
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
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IL_RDF · Official waterbody report
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Grading methodology based on Metropolitan Council standards
Most recent sample: 2022-11-02
Monitoring stations: 4