Round Lake
Sawyer County, WisconsinOligotrophic
Round Lake earns an A — every scored parameter (clarity, phosphorus, and chlorophyll-a) rates among the best monitored waters in Sawyer County. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.
A TSI value of 35 puts Round Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. At 74 ft of maximum depth, Round Lake stratifies reliably through the summer — the hypolimnion stays cooler and clearer than the surface layer suggests. At 3,294 acres, Round Lake is one of the larger lakes in Sawyer County, with partial shoreline records supporting multiple distinct use patterns. Within Sawyer County's 50 graded waters, Round Lake sits at rank 1, near the top of the local distribution.
Eurasian watermilfoil has been documented at Round Lake, requiring shoreline management to keep dense mats from crowding native vegetation. Walleye are documented at Round Lake, one of 6 fish species on record for the lake. The grade is supported by multiple sampling years from the Wisconsin DNR Citizen Lake Monitoring Network, giving the letter a reasonably stable foundation.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2025-09-11. Grade methodology: LakeGrade methodology.
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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 21.1 ft down. Phosphorus level: 14.4 µg/L. Chlorophyll-a: 1 µg/L. Trophic State Index: 35.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 21.1 ft | A |
| Phosphorus | 14.4 µg/L | A |
| Chlorophyll-a (Algae) | 1 µg/L | A |
| Trophic State Index (TSI) | 35 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 74 ft |
| Surface Area | 3.3K acres |
Fish Species
Click a species to see all Wisconsin and Minnesota lakes where it is found.
→ Best fishing times for Round Lake (14-day solunar calendar)
→ Is it safe to eat fish from Round Lake? (mercury & PFAS guide)
→ Round 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 | → Stable | +0.39 m/yr | 6 |
| Phosphorus | → Stable | +0.14 µg/L/yr | 3 |
| Chlorophyll-a | ↑ Improving | -0.13 µg/L/yr | 2 |
Location
County Ranking
Ranked #1 of 50 lakes in Sawyer County
Nearby Lakes in Sawyer 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
Compare Round Lake With Nearby Lakes
Sawyer County · Grade B
Sawyer County · Grade C
Sawyer County · Grade C
Sawyer County · Grade C
Sawyer County · Grade C
Sawyer County · Grade A
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. Monitored by volunteers since 1995. 11 stations on file (most recent sample 2025).
Fish Species (DNR-rated)
DNR Reports & Resources
Wisconsin DNR Fisheries scientists publish multi-year survey reports for Round Lake covering fish populations, stocking, water quality, and management. 2 reports on file.
- 2025Round Lake spring survey, 2025Fisheries Survey · WI DNR · 2025 (PDF)
- 2023Round Lake spring shocking and netting survey, 2023Spring Shocking Survey · WI DNR · 2023 (PDF)
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Most recent sample: 2025-09-11
Monitoring stations: 7