Portage Lake
St. Joseph County, MichiganView mapDirections
Nutrients and algae sit mid-range for this region.
↑ up from D at the last regrade
- Oligotrophic
- #7 of 8 in the county
- Public access
- Limited data
Portage Lake in St. Joseph County, Michigan has a water quality grade of C (Fair). Water clarity: 5.5 ft visibility. Phosphorus: 31 µg/L. Chlorophyll-a (algae): 1.6 µg/L.
- Clarity
- 5.5 ft
- Typical in September
- 64°F
- Type
- Oligotrophic
- Trend
- ↓ Declining
- Public access
- Yes
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Watch Portage Lake’s letter
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Portage Lake is a cold, clear oligotrophic lake in St. Joseph County, Michigan. Water quality is graded C based on 2 sampling years through 2023. Overall water quality is declining over recent sampling years. The lake supports 3 documented fish species including Chestnut lamprey, Common shiner, and Rainbow darter. Public access is available. Compared to the 7 other monitored lakes in St. Joseph County, Portage Lake ranks #7 for water quality.
Source: EPA Water Quality Portal sampling records, EGLE, last sampled 2023-09-23. Grade methodology: LakeQuality methodology.
What Portage Lake is good for
From access and monitoring records, not editorial picks.
- Fishing3 species recorded
Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
The C is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
Water Quality Grade: C (Fair)
Murky, only visible to about 5.5 ft. Phosphorus 31 µg/L. Chlorophyll-a 1.6 µg/L. TSI 47. The letter is not a swimming clearance.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.5 ft | Not graded |
| Phosphorus | 31 µg/L | Fair |
| Chlorophyll-a (Algae) | 1.6 µg/L | Good |
| Trophic State Index (TSI) | 47 | Oligotrophic |
Low nutrients, clear water. The letter is not a swimming clearance.
Water Temperature
Portage Lake typically sits around 64°F at the surface in September. Summer average is about 64°F. Usually warmest in Jul (about 65°F) and coldest in May (about 58°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 277 field readings (2016–2019) via the EPA Water Quality Portal. See the full Portage Lake water temperature breakdown →
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Portage Lake
Water Quality Trend: ↓ Declining
Based on 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.012 m/yr | 7 |
| Phosphorus | → Stable | -0.01 µg/L/yr | 6 |
| Chlorophyll-a | ↓ Declining | +0.21 µg/L/yr | 4 |
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Portage Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Th Plastics IncMendon · 4.4 mi away · NPDES MIG250278Recent violation
- Parkville Prairie FarmsThree Rivers · 1.6 mi away · NPDES MIG440036
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
County Ranking
Ranked #7 of 8 lakes in St. Joseph County
Nearby Lakes With Higher Grades
Portage Lake holds Grade C. 3 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
Nearby Lakes in St. Joseph County
Frequently asked questions about Portage Lake
Where is Portage Lake?
- Portage Lake is a lake in St. Joseph County, Michigan. LakeQuality grades it C for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Portage Lake?
- Portage Lake in St. Joseph County, Michigan has a water quality grade of C (Fair). Water clarity: 5.5 ft visibility. Phosphorus: 31 µg/L. Chlorophyll-a (algae): 1.6 µg/L.
Is Portage Lake safe to swim in?
- The C is nutrients and algae, not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Portage Lake?
- Portage Lake typically sits around 64°F at the surface in September, from 277 EPA Water Quality Portal field readings (2016–2019). That is a typical value for the month, not a live reading.
What fish are in Portage Lake?
- Fish species found in Portage Lake include Chestnut lamprey, Common shiner, Rainbow darter. Portage Lake is located in St. Joseph County, Michigan.
Explore Portage Lake across LakeQuality
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Fish species and best lakes in St. Joseph County
Species activity outlook by water temperature and season
Where to stay at Michigan's top lakes, each with its grade
Low nutrients, clear water. The letter is not a swimming clearance.
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Where this data comes from
145 measurements from 1 monitoring station, 2016–2023. Retrieved from the EPA Water Quality Portal on 2026-08-26.
Collected and reported by
- Michigan EGLE - MiCorps
21MICH_MICORPS145 samples · 2016–2023
Analytical methods
- Phosphorus by Colorimetry
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Regulated discharger data from EPA ECHO (ICIS-NPDES)