Keyes Lake
Florence County, WisconsinOligotrophic
On the LakeGrade rubric, Keyes Lake pulls an A: clarity at 21.0 ft and 11 µg/L of phosphorus put it in the top bracket for Wisconsin. Sub-grades cluster within a single letter of each other, which usually means the lake is in stable trophic balance rather than fighting one specific stressor.
A TSI value of 36 puts Keyes Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. 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. Within Florence County's 39 graded waters, Keyes Lake sits at rank 4, near the top of the local distribution.
No invasive species are currently listed at Keyes Lake — the lake remains off the Wisconsin infested-waters roster. The state fisheries records do not list documented species for Keyes Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-05-05. Grade methodology: LakeGrade methodology.
Watch Keyes Lake water quality
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Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Crystal clear, you can see 21 ft down. Phosphorus level: 11.1 µg/L. Trophic State Index: 36.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 21 ft | A |
| Phosphorus | 11.1 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 36 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.038 m/yr | 6 |
| Phosphorus | ↑ Improving | -1.5 µg/L/yr | 4 |
Recreation & Access
Location
County Ranking
Ranked #4 of 39 lakes in Florence County
Nearby Lakes in Florence County
More Wisconsin Lake Rankings
Other Grade A Lakes in Wisconsin
Washington County · Clarity: 11.8 ft
Washington County · Clarity: 12.6 ft
Walworth County · Clarity: 11 ft
Waukesha County · Clarity: 11.3 ft
Walworth County · Clarity: 20.2 ft
Kenosha County · Clarity: 10 ft
Oligotrophic Lakes in Wisconsin
DNR Reports & Resources
Wisconsin DNR Fisheries scientists publish multi-year survey reports for Keyes Lake covering fish populations, stocking, water quality, and management. 1 report on file.
- 2016Keyes Lake fisheries summary report, 2016Fisheries Survey · WI DNR · 2016 (PDF)
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2026-05-05
Monitoring stations: 2
Where to stay near Keyes Lake
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