Boulder South Lake
Perry County, WisconsinMesotrophic
Boulder South Lake is a mesotrophic lake in Perry County, IL. Water quality is graded B based on 2 sampling years through 2021. Compared to the 1 other monitored lakes in Perry County, Boulder South Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2021-10-12. Grade methodology: LakeGrade methodology.
Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Moderate clarity, visible to about 8.8 ft. Phosphorus level: 14.5 µg/L. Trophic State Index: 44.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 8.8 ft | C |
| Phosphorus | 14.5 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 44 | Mesotrophic |
Moderate nutrients, good water quality
Location
County Ranking
Ranked #1 of 2 lakes in Perry County
Nearby Lakes in Perry County
More Wisconsin Lake Rankings
Other Grade B Lakes in Wisconsin
Mesotrophic Lakes in Wisconsin
EPA Impairment Status
Boulder South 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_RNZK · 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: 2021-10-12
Monitoring stations: 3