Cedar Lake
Manitowoc County, WisconsinOligotrophic
Cedar Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Manitowoc County. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.
The lake's low TSI puts it in oligotrophic territory — the cleanest of the four trophic classes, but also the most vulnerable to nutrient-driven shifts. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake's surface area is not consistently recorded across state datasets — physical context remains partial. Cedar Lake ranks 2 of 18 in Manitowoc County, putting it in the upper tier of locally monitored lakes.
No invasive species are currently listed at Cedar Lake — the lake remains off the Wisconsin infested-waters roster. The state fisheries records do not list documented species for Cedar Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2025-08-11. Grade methodology: LakeGrade methodology.
Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Crystal clear, you can see 34.5 ft down. Phosphorus level: 17.3 µg/L. Trophic State Index: 36.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 34.5 ft | A |
| Phosphorus | 17.3 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 36 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Water Quality Trend: → Stable
Based on 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.243 m/yr | 7 |
| Phosphorus | ↑ Improving | -1.15 µg/L/yr | 6 |
Location
County Ranking
Ranked #2 of 18 lakes in Manitowoc County
Nearby Lakes in Manitowoc County
More Wisconsin Lake Rankings
State Parks Near Cedar Lake
Other Grade A Lakes in Wisconsin
Waukesha County · Clarity: 14.6 ft
Waukesha County · Clarity: 13.8 ft
Walworth County · Clarity: 19 ft
Washington County · Clarity: 12 ft
Kenosha County · Clarity: 10.1 ft
Washington County · Clarity: 12.5 ft
Oligotrophic Lakes in Wisconsin
DNR Reports & Resources
Wisconsin DNR Fisheries scientists publish multi-year survey reports for Cedar Lake covering fish populations, stocking, water quality, and management. 2 reports on file.
- 2022Cedar Lake comprehensive survey, 2022Comprehensive Survey · WI DNR · 2022 (PDF)
- 2016Cedar Lake comprehensive survey 2016Comprehensive Survey · WI DNR · 2016 (PDF)
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Most recent sample: 2025-08-11
Monitoring stations: 2