Ellwood Lake
Florence County, WisconsinMesotrophic
Ellwood Lake sits at the top of the Wisconsin DNR grading rubric with an A, a mark reached by the cleanest lakes in Wisconsin. The two scored sub-grades — clarity and phosphorus — track close together, so neither one is dragging the average down.
Mesotrophic conditions dominate at Ellwood Lake: enough nutrients for a healthy fishery, not so much that algal blooms become a chronic problem. A maximum depth of 25 ft puts Ellwood Lake in the middle of Wisconsin's depth distribution. At 130 acres, Ellwood Lake fits the Wisconsin median for monitored lakes, with partial shoreline records. Among the 39 graded lakes in Florence County, Ellwood Lake ranks 9 — in the top quartile locally.
Zebra mussels have been documented at Ellwood Lake, which alters the filter-feeding balance and can paradoxically increase water clarity while disrupting the food web. Bass fishing is part of the appeal: the species list runs to 4, anchored by largemouth and/or smallmouth bass. 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 2025-08-25. 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 13 ft. Phosphorus level: 12 µg/L. Trophic State Index: 40.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 13 ft | B |
| Phosphorus | 12 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 40 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 25 ft |
| Surface Area | 130 acres |
Fish Species
Click a species to see all Wisconsin and Minnesota lakes where it is found.
→ Best fishing times for Ellwood Lake (14-day solunar calendar)
→ Is it safe to eat fish from Ellwood Lake? (mercury & PFAS guide)
→ Ellwood 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 | +0.357 m/yr | 6 |
| Phosphorus | → Stable | +0.08 µg/L/yr | 6 |
Location
County Ranking
Ranked #9 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
Mesotrophic Lakes in Wisconsin
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. Monitored by volunteers since 1994. 4 stations on file (most recent sample 2025).
Fish Species (DNR-rated)
DNR Reports & Resources
Wisconsin DNR Fisheries scientists publish multi-year survey reports for Ellwood Lake covering fish populations, stocking, water quality, and management. 1 report on file.
- 2022Ellwood Lake shocking and netting survey, 2022Netting Survey · WI DNR · 2022 (PDF)
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Most recent sample: 2025-08-25
Monitoring stations: 2