How Clean Is Thunder Lake?
Thunder Lake is among the cleanest lakes in Minnesota. It received a water quality grade of A (Excellent) based on EPA monitoring data. Water clarity (Secchi depth): 16.4 ft. Phosphorus: 10 µg/L. Trophic State Index: 37.
Cleanliness Snapshot
| Metric | Thunder Lake | Minnesota avg |
|---|---|---|
| Overall Grade | A | C |
| Water Clarity (Secchi) | 16.4 ft | — |
| Phosphorus | 10 µg/L | <30 = clean |
| Trophic State Index | 37 | <50 = clean |
How does Thunder Lake compare?
Thunder Lake's grade of A matches or beats the Minnesota state average of C. It ranks #17 of 133 lakes in Cass County by water quality score. Multi-year monitoring data shows water quality is improving based on 5 years of records.