North Twin Lake
Calhoun County, WisconsinHypereutrophic
North Twin Lake is a highly nutrient-loaded hypereutrophic lake in Calhoun County, IA. Water quality is graded F based on 2 sampling years through 2024.
Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2024-09-04. Grade methodology: LakeGrade methodology.
Swimming Safety
Avoid swimming, very poor water quality, potential algae toxins
Water Quality Grade: F, Very Poor
Very murky, less than 1.1 ft of visibility. Chlorophyll-a: 31.4 µg/L. Trophic State Index: 70.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.1 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | 31.4 µg/L | F |
| Trophic State Index (TSI) | 70 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Location
County Ranking
Ranked #1 of 1 lakes in Calhoun County
Cleaner Lakes Within 30 Miles
North Twin Lake holds Grade F. 2 nearby lakes hold higher grades.
- CArrowhead LakeSac County · 24.5 mi · Two grade letters higher (F → C)
- CNewell Pit LakeBuena Vista County · 22.7 mi · Two grade letters higher (F → C)
Nearby Lakes in Calhoun County
More Wisconsin Lake Rankings
Other Grade F Lakes in Wisconsin
Hypereutrophic Lakes in Wisconsin
EPA Impairment Status
North Twin Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit IA 04-RAC-1167 · 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: 2024-09-04
Monitoring stations: 1