The State of Wisconsin's Lakes 2026

Cleanest lakes in Wisconsin

Highest combined water-quality score, 2026.

1. 1.ABig Cedar Lake-North Site-Near West Bend — Washington County11.8 ft clarity · 18 µg/L P · 4 µg/L chl-a
2. 2.AGreen Lake — Green Lake County13.5 ft clarity · 38 µg/L P · 4 µg/L chl-a
3. 3.ALake Beulah — Walworth County10.0 ft clarity · 13 µg/L P · 3 µg/L chl-a
4. 4.AGeneva Lake — Walworth County21.0 ft clarity · 13 µg/L P · 2 µg/L chl-a
5. 5.APowers Lake — Kenosha County10.0 ft clarity · 17 µg/L P · 3 µg/L chl-a
6. 6.ALac Courte Oreilles Lake — Sawyer County12.2 ft clarity · 15 µg/L P · 2 µg/L chl-a
7. 7.AWhitefish Lake — Sawyer County13.5 ft clarity · 14 µg/L P · 2 µg/L chl-a
8. 8.ARound Lake — Sawyer County21.1 ft clarity · 14 µg/L P · 1 µg/L chl-a
9. 9.AIndian Lake — Sawyer County6.5 ft clarity · 23 µg/L P · 4 µg/L chl-a
10. 10.ABig Lake — Shawano County8.0 ft clarity · 15 µg/L P · 3 µg/L chl-a

Most-polluted lakes

Lowest combined water-quality score among monitored lakes.

1. 1.DLake Montanis — Barron County2.0 ft clarity · 49 µg/L P
2. 2.DLake Redstone — Sauk County2.0 ft clarity · 89 µg/L P
3. 3.DBeaver Dam Lake — Dodge County1.0 ft clarity · 231 µg/L P
4. 4.DRound Lake — Burnett County5.2 ft clarity · 41 µg/L P
5. 5.DCedar Lake — Polk County6.1 ft clarity · 42 µg/L P
6. 6.DMirror Lake — Sauk County4.6 ft clarity · 65 µg/L P
7. 7.DTainter Lake — Dunn County3.7 ft clarity · 122 µg/L P
8. 8.DRice Lake — Dane County1.5 ft clarity · 217 µg/L P
9. 9.DRice Lake — Walworth County1.7 ft clarity · 60 µg/L P
10. 10.DLong Trade Lake — Polk County3.0 ft clarity · 85 µg/L P

Worst algae hotspots

Highest measured chlorophyll-a (algae) concentration.

No qualifying lakes with sufficient data.

Trending lakes

Improving

1. 1.AGreen Lake — Green Lake County
2. 2.ALake Beulah — Walworth County
3. 3.APowers Lake — Kenosha County
4. 4.ALac Courte Oreilles Lake — Sawyer County
5. 5.AWhitefish Lake — Sawyer County
6. 6.ARound Lake — Sawyer County
7. 7.ABig Lake — Shawano County
8. 8.AAshegon Lake — Sawyer County

Declining

1. 1.DLake Redstone — Sauk County
2. 2.DBeaver Dam Lake — Dodge County
3. 3.DRice Lake — Dane County
4. 4.DRice Lake — Walworth County
5. 5.DHidden Valley Lake — Lafayette County
6. 6.DBear Lake — Bayfield County
7. 7.DButternut Lake — Barron County
8. 8.DAltoona Lake — Eau Claire County