Gratiot Lake
Keweenaw County, WisconsinLimited DataOligotrophic
Gratiot Lake is a cold, clear oligotrophic lake in Keweenaw County, MI. Water quality is graded A based on 1 sampling years through 2023. The lake supports 1 documented fish species including Ninespine stickleback. Compared to the 18 other monitored lakes in Keweenaw County, Gratiot Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2023-09-14. Grade methodology: LakeGrade methodology.
Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Crystal clear, you can see 19 ft down. Trophic State Index: 35.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 19 ft | A |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 35 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Fish Species
Click a species to see all Wisconsin and Minnesota lakes where it is found.
→ Best fishing times for Gratiot Lake (14-day solunar calendar)
→ Is it safe to eat fish from Gratiot Lake? (mercury & PFAS guide)
→ Gratiot Lake fishing regulations (limits, seasons, special rules)
Location
County Ranking
Ranked #3 of 19 lakes in Keweenaw County
Nearby Lakes in Keweenaw County
More Wisconsin Lake Rankings
Other Grade A Lakes in Wisconsin
Mecosta County · Clarity: 12.8 ft
Benzie County · Clarity: 13.5 ft
Clare County · Clarity: 15 ft
Kalkaska County · Clarity: 16 ft
Gogebic County · Clarity: 18 ft
Iron County · Clarity: 16 ft
Oligotrophic Lakes in Wisconsin
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Most recent sample: 2023-09-14
Monitoring stations: 1