Big Dummy Lake
Barron County, WisconsinMesotrophic
On the LakeGrade rubric, Big Dummy Lake pulls an A: clarity at 12.0 ft and 16 µg/L of phosphorus put it in the top bracket for Wisconsin. clarity and phosphorus rate similarly, so there is no obvious single lever to pull on watershed management.
Mesotrophic conditions dominate at Big Dummy Lake: enough nutrients for a healthy fishery, not so much that algal blooms become a chronic problem. Big Dummy Lake is unusually deep for Wisconsin at 54 ft, which buffers the lake against summer warming and helps the deep water stay oxygenated. Big Dummy Lake covers 114 acres alongside partial shoreline records — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Among the 37 graded lakes in Barron County, Big Dummy Lake ranks 4 — in the top quartile locally.
An invasive species record — Chinese Mystery Snail — has been logged at Big Dummy Lake; Wisconsin DNR maintains the official infested-waters list. Walleye are documented at Big Dummy Lake, one of 4 fish species on record for the 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 2025-08-27. Grade methodology: LakeGrade methodology.
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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 12 ft. Phosphorus level: 16.4 µg/L. Trophic State Index: 43.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 12 ft | B |
| Phosphorus | 16.4 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 43 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 54 ft |
| Surface Area | 114 acres |
Fish Species
Click a species to see all Wisconsin and Minnesota lakes where it is found.
→ Best fishing times for Big Dummy Lake (14-day solunar calendar)
→ Is it safe to eat fish from Big Dummy Lake? (mercury & PFAS guide)
→ Big Dummy Lake fishing regulations (limits, seasons, special rules)
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +1 m/yr | 6 |
| Phosphorus | ↑ Improving | -0.97 µg/L/yr | 6 |
Location
County Ranking
Ranked #4 of 37 lakes in Barron County
Nearby Lakes in Barron County
More Wisconsin Lake Rankings
State Parks Near Big Dummy Lake
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 1988. 1 station on file (most recent sample 2025).
Fish Species (DNR-rated)
EPA Impairment Status
Big Dummy Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5R).
Causes of impairment
Source: EPA ATTAINS assessment unit WI10004446 · 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: 2025-08-27
Monitoring stations: 1