Portage Lake Central Basin; Onekama Township
Manistee County, WisconsinLimited DataOligotrophic
Portage Lake Central Basin; Onekama Township is a cold, clear oligotrophic lake in Manistee County, MI. Water quality is graded B based on 1 sampling years through 2023. Compared to the 11 other monitored lakes in Manistee County, Portage Lake Central Basin; Onekama Township ranks #10 for water quality.
Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2023-09-10. Grade methodology: LakeGrade methodology.
Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Good clarity, visible to about 13.8 ft. Trophic State Index: 39.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 13.8 ft | B |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 39 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Location
County Ranking
Ranked #10 of 12 lakes in Manistee County
Cleaner Lakes Within 30 Miles
Portage Lake Central Basin; Onekama Township holds Grade B. One nearby lake has a higher grade.
See full comparison →Nearby Lakes in Manistee County
More Wisconsin Lake Rankings
Other Grade B Lakes in Wisconsin
Lapeer County · Clarity: 9.5 ft
Livingston County · Clarity: 13 ft
Lake County · Clarity: 14 ft
Cass County · Clarity: 10.5 ft
Genesee County · Clarity: 10 ft
Lake County · Clarity: 8 ft
Oligotrophic Lakes in Wisconsin
EPA Impairment Status
Portage Lake Central Basin; Onekama Township is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MI040601040405-02 · Official waterbody report · Matched by proximity (0.27 km)
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Grading methodology based on Metropolitan Council standards
Most recent sample: 2023-09-10
Monitoring stations: 1