DeclineUpdated April 2026
Most Polluted Lakes
Lakes with the worst water quality grades
Silent Street Pond in Dane, WI has the worst water quality with a TSI of 94 and an F grade.
| # | Name | Metric | Grade |
|---|---|---|---|
| 1 | Silent Street Pond Grade F, TSI 94 (hypereutrophic), Dane, WI | 94 | F |
| 2 | String Lake Grade F, TSI 93 (hypereutrophic), Cottonwood, MN | 93 | F |
| 3 | Outlet To Lake Geneva Grade F, TSI 93 (hypereutrophic), Walworth, WI | 93 | F |
| 4 | Olson Lake Grade F, TSI 92 (hypereutrophic), Big Stone, MN | 92 | F |
| 5 | Investment Court Pond Grade F, TSI 92 (hypereutrophic), Dane, WI | 92 | F |
| 6 | Northwood Lake Grade F, TSI 90 (hypereutrophic), Hennepin, MN | 90 | F |
| 7 | Cowley Lake Grade F, TSI 90 (hypereutrophic), Hennepin, MN | 90 | F |
| 8 | Prairie Oaks Pond Grade F, TSI 89 (hypereutrophic), Dane, WI | 89 | F |
| 9 | Gonz Lake Grade F, TSI 88 (hypereutrophic), Wright, MN | 88 | F |
| 10 | Wakanda Lake Grade F, TSI 87 (hypereutrophic), Kandiyohi, MN | 87 | F |
Silent Street Pond in Dane, WI has the worst water quality with a TSI of 94 and an F grade.
Frequently Asked Questions
This report is auto-generated from real public data sources. Entities are ranked by their key metrics and the most notable changes and extremes are highlighted.
The underlying data is refreshed on a regular schedule. This report was generated from the most recent available data (last updated April 2026).
The primary metric varies by report type. It may represent a score, dollar amount, rate, or count depending on what the report is measuring.