Armour Lake
Vilas County, WisconsinMesotrophic
On the LakeGrade rubric, Armour Lake pulls an A: clarity at 10.5 ft and 12 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 near 41 places Armour Lake in the mesotrophic band — moderate productivity, with seasonal swings between clearer spring water and richer late-summer conditions. Armour Lake is unusually deep for Wisconsin at 56 ft, which buffers the lake against summer warming and helps the deep water stay oxygenated. At 328 acres, Armour Lake fits the Wisconsin median for monitored lakes, with partial shoreline records. Among the 191 graded lakes in Vilas County, Armour Lake sits at rank 60, above the county median.
Armour Lake has no invasive species recorded in Wisconsin state databases as of 2025, though prevention practices still apply at all access points. Walleye are documented at Armour Lake, one of 6 fish species on record for the 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 2025-10-27. Grade methodology: LakeGrade methodology.
Watch Armour Lake water quality
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Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Good clarity, visible to about 10.5 ft. Phosphorus level: 11.7 µg/L. Trophic State Index: 41.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 10.5 ft | B |
| Phosphorus | 11.7 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 41 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 56 ft |
| Surface Area | 328 acres |
Fish Species
Click a species to see every graded lake where it is documented.
→ Best fishing times for Armour Lake (14-day solunar calendar)
→ Is it safe to eat fish from Armour Lake? (mercury & PFAS guide)
→ Armour Lake fishing regulations (limits, seasons, special rules)
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.086 m/yr | 6 |
| Phosphorus | ↑ Improving | -0.68 µg/L/yr | 5 |
Location
County Ranking
Ranked #60 of 191 lakes in Vilas County
Nearby Lakes in Vilas 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
Mesotrophic Lakes in Wisconsin
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. Monitored by volunteers since 1998. 1 station on file (most recent sample 2025).
Fish Species (DNR-rated)
EPA Impairment Status
Armour 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 WI10007528 · Official waterbody report · Matched by proximity (2.38 km)
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
Fish and recreation data from Wisconsin DNR Lakes
Most recent sample: 2025-10-27
Monitoring stations: 2
Where to stay near Armour Lake
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