Turtlehead Lake
Cook County, WisconsinEutrophic
Turtlehead Lake is a productive, nutrient-rich eutrophic lake in Cook County, IL. Water quality is graded C based on 2 sampling years through 2021. Compared to the 67 other monitored lakes in Cook County, Turtlehead Lake ranks #13 for water quality.
Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2021-09-21. Grade methodology: LakeGrade methodology.
Swimming Safety
Generally safe for swimming, moderate water quality
Water Quality Grade: C, Fair
Very murky, less than 2.8 ft of visibility. Phosphorus level: 20.5 µg/L. Trophic State Index: 55.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.8 ft | F |
| Phosphorus | 20.5 µg/L | B |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 55 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Location
County Ranking
Ranked #13 of 68 lakes in Cook County
Nearby Lakes in Cook County
More Wisconsin Lake Rankings
Other Grade C Lakes in Wisconsin
Eutrophic Lakes in Wisconsin
EPA Impairment Status
Turtlehead Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit IL_RHZE · Official waterbody report · Matched by proximity (1.32 km)
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: 2021-09-21
Monitoring stations: 2