Portage Lake Central Basin; Onekama Township is a cold, clear oligotrophic lake in Manistee County, Michigan. Water quality is graded B based on 1 sampling years through 2023. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. 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, Michigan DNR, last sampled 2023-09-10. Grade methodology: LakeGrade methodology.
Watch Portage Lake Central Basin; Onekama Township water quality
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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
Where to stay near Portage Lake Central Basin; Onekama Township
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Fishing Portage Lake Central Basin; Onekama Township
Water Quality Trend: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +8.9 m/yr | 2 |
Recreation & Access
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.
Nearby Lakes in Manistee County
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Low nutrients, clear water, excellent for swimming
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More records, surveys & data sources
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)
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2023-09-10
Monitoring stations: 1