Ember Lake
Polk County, WisconsinOligotrophic
Ember Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Polk County. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.
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. Ember Lake sits at rank 41 of 77 in Polk County, in the lower half of the local distribution.
Ember Lake has no invasive species recorded in Wisconsin state databases as of 2024, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Ember 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 2024-09-09. 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 27.1 ft down. Phosphorus level: 20.2 µg/L. Trophic State Index: 39.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 27.1 ft | A |
| Phosphorus | 20.2 µg/L | B |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 39 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Water Quality Trend: ↓ Declining
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.5 m/yr | 2 |
| Phosphorus | → Stable | -0.4 µg/L/yr | 2 |
Location
County Ranking
Ranked #41 of 77 lakes in Polk County
Nearby Lakes in Polk County
More Wisconsin Lake Rankings
State Parks Near Ember 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
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Most recent sample: 2024-09-09
Monitoring stations: 2