How Clean Is Portage Lake?
Portage Lake has fair water quality — typical of lakes with moderate nutrient enrichment. It received a water quality grade of C (Fair) based on EPA monitoring data. Water clarity (Secchi depth): 7.5 ft. Phosphorus: 22 µg/L. Chlorophyll-a (algae): 7.1 µg/L. Trophic State Index: 49.
Cleanliness Snapshot
| Metric | Portage Lake | Minnesota avg |
|---|---|---|
| Overall Grade | C | C |
| Water Clarity (Secchi) | 7.5 ft | — |
| Phosphorus | 22 µg/L | <30 = clean |
| Chlorophyll-a (Algae) | 7.1 µg/L | <10 = clean |
| Trophic State Index | 49 | <50 = clean |
How does Portage Lake compare?
Portage Lake's grade of C matches or beats the Minnesota state average of C. It ranks #88 of 104 lakes in Cass County by water quality score. Multi-year monitoring data shows water quality is improving based on 2 years of records.