How Clean Is Colby Lake?
Colby 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): 3.5 ft. Phosphorus: 22 µg/L. Trophic State Index: 54.
Cleanliness Snapshot
| Metric | Colby Lake | Minnesota avg |
|---|---|---|
| Overall Grade | C | C |
| Water Clarity (Secchi) | 3.5 ft | — |
| Phosphorus | 22 µg/L | <30 = clean |
| Trophic State Index | 54 | <50 = clean |
How does Colby Lake compare?
Colby Lake's grade of C matches or beats the Minnesota state average of C. It ranks #95 of 187 lakes in St. Louis County by water quality score. Multi-year monitoring data shows water quality is declining based on 5 years of records.