Updated August 2026 · Top 25 of 1,091 lakes with a Secchi reading
Clearest Lake in Wisconsin: Top 25 by Secchi Depth
Adams Lake in Vilas County is the clearest lake in Wisconsin by Secchi depth, at 100 ft. Mapped and ranked below: the 25 clearest of 1,091 Wisconsin lakes with a Secchi reading. Secchi depth is shown, not scored: the letter grades nutrients and algae, so a clear lake can be unrated or carry a lower grade than a murkier one.
How clear are Wisconsin's clearest lakes?
From 100 ft at Adams Lake to 21 ft at #25, Geneva Lake; the median of the 25 is 23 ft.
| # | Lake | County | Secchi depth | Grade | Max depth | Area |
|---|---|---|---|---|---|---|
| 1 | Adams Lake | Vilas | 100 ft | NR | 14 ft | 9 acres |
| 2 | Wazee Lake | Jackson | 30 ft | NR | 350 ft | 146 acres |
| 3 | Black Oak Lake | Vilas | 29 ft | B | 85 ft | 564 acres |
| 4 | Bardon Lake | Douglas | 27 ft | C | 102 ft | 848 acres |
| 5 | Saxon Fall Flowage Lake | Iron | 26.2 ft | NR | 12 ft | 68 acres |
| 6 | Wheeler Lake | Oconto | 26 ft | B | 35 ft | 281 acres |
| 7 | Sealion Lake | Florence | 25.6 ft | NR | — | — |
| 8 | Pine Lake | Waukesha | 25 ft | B | 85 ft | 711 acres |
| 9 | Lake Owen | Bayfield | 24.6 ft | B | 95 ft | 1,250 acres |
| 10 | Roach Lake | Vilas | 24 ft | NR | 48 ft | 48 acres |
| 11 | Big Hurst Lake | Vilas | 24 ft | NR | 44 ft | 47 acres |
| 12 | Clara Lake-Deep Hole | Lincoln | 23.8 ft | NR | 50 ft | 21 acres |
| 13 | Stone Lake | Washburn | 23 ft | B | 49 ft | 490 acres |
| 14 | Millicent Lake | Bayfield | 23 ft | NR | — | — |
| 15 | Blue Lake | Oneida | 23 ft | B | 49 ft | 441 acres |
| 16 | Maiden Lake | Oconto | 23 ft | B | 52 ft | 269 acres |
| 17 | Lee Lake | Oneida | 22.5 ft | B | 44 ft | 65 acres |
| 18 | Forest Lake | Vilas | 22.2 ft | B | 60 ft | 468 acres |
| 19 | Lake Metonga | Forest | 22 ft | B | 79 ft | 2,038 acres |
| 20 | Buskey Bay Lake | Bayfield | 21.9 ft | NR | 51 ft | 88 acres |
| 21 | Long Lake | Burnett | 21.5 ft | B | 41 ft | 222 acres |
| 22 | Boot Lake | Oconto | 21.5 ft | B | 38 ft | 230 acres |
| 23 | Hart Lake | Bayfield | 21.5 ft | NR | 54 ft | 257 acres |
| 24 | Round Lake | Sawyer | 21.1 ft | A | 74 ft | 3,294 acres |
| 25 | Geneva Lake | Walworth | 21 ft | A | 135 ft | 5,401 acres |
Sources and method
- Secchi depth: Median of each lake's EPA Water Quality Portal readings, sampled April 2020 to July 2026, in feet. Every reading in this table was submitted by Wisconsin Department of Natural Resources. Portal: EPA Water Quality Portal.
- Grade: A–F water-quality grade from nutrient and algae sampling (total phosphorus and chlorophyll-a) against the lake's EPA ecoregion classes, where enough recent samples exist to support one; the dashed NR mark otherwise. Clarity is not part of the grade, which is why a clear lake here can be unrated or carry a lower letter than a murkier one.
- Max depth: Wisconsin DNR lake surveys. Surveyed depths only; a dash means no survey recorded one.
- Area: state agency lake surveys and, for reservoirs, US Army Corps of Engineers National Inventory of Dams records, in acres at normal pool. A dash means no record carries one.
- Map pins: all 25 table rows, colored by grade. No other lakes are plotted.
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Frequently Asked Questions
What is the clearest lake in Wisconsin?
Adams Lake in Vilas County is the clearest lake in Wisconsin by Secchi depth, at 100 ft. Secchi depth is measured by lowering a black-and-white disk until it disappears from view; a deeper reading means clearer water. Adams Lake is not rated: no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
How clear are Wisconsin's 25 clearest lakes?
They span 21 ft to 100 ft of Secchi depth, with a median of 23 ft. Adams Lake leads by 70 ft. Vilas County has 5 of the 25; the rest are spread across 14 other counties. 15 of the 25 carry an A–F grade; the other 10 are not rated because their recent sampling does not support a letter.
How is water clarity measured?
Water clarity is measured by Secchi depth, named after the 19th-century Italian astronomer Pietro Angelo Secchi who developed the method. A standardized black-and-white disk is lowered into the water on a rope; the depth (in feet or meters) at which the disk disappears from view is recorded. Greater Secchi depth means clearer water, usually a sign of low sediment, low phosphorus, and limited algae growth. The figure for each lake here is the median of its readings.
What makes a lake clear?
Lake clarity is driven by three factors: low suspended sediment (clay, silt), low nutrient load (especially phosphorus, which fuels algae), and low chlorophyll-a (active algae biomass). Deep lakes with rocky basins and forested watersheds tend to be clearest because they take in little soil runoff and few nutrients. Shallow lakes in farmed watersheds are typically less clear because they receive more sediment and fertilizer runoff.
Is the clearest lake the cleanest?
Not always. Clarity (Secchi depth) is measured and shown; the letter grades nutrients and algae (total phosphorus and chlorophyll-a) against that lake’s EPA ecoregion classes. A lake can be very clear but still have elevated phosphorus that just hasn't bloomed yet. See our companion cleanest-lakes ranking for Wisconsin for the nutrient-and-algae list.
Where to stay near Wisconsin's clearest lakes
Planning a trip? Jump to live cabin, resort, and hotel availability near Wisconsin's clearest lakes.
- Adams Lake · Vilas CountyCabins & hotels near Adams Lake →
- Wazee Lake · Jackson CountyCabins & hotels near Wazee Lake →
- Black Oak Lake · Vilas CountyCabins & hotels near Black Oak Lake →
- Bardon Lake · Douglas CountyCabins & hotels near Bardon Lake →
- Saxon Fall Flowage Lake · Iron CountyCabins & hotels near Saxon Fall Flowage Lake →
More on water clarity
The clearest lakes in America, ranked by measured Secchi depth in feet from EPA monitoring data — and why the famously clear lakes are missing.
What a Secchi depth reading measures, how many feet counts as good clarity, and why clear water is not always clean — with readings from graded lakes.
County-by-county Secchi champions: the clearest measured lake in each county, the murkiest county winners, and why a county title is not a national one.
Surveyed maximum depth against A–F nutrient-and-algae grades: the pattern, the shallow lakes that still grade an A, and why land use beats bathymetry.