Portage Lake
Cook County, Minnesota128 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Portage Lake. Here is what has been measured.
- Mesotrophic
- 55 ft max depth
- Limited data
Portage Lake in Cook County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 8.5 ft visibility. Phosphorus: 9.5 µg/L. Chlorophyll-a (algae): 3.3 µg/L. Maximum depth: 55 ft. Surface area: 128.12 acres.
Minnesota DNR's Standard Survey on June 8, 2022 caught 13.33 white sucker per gill net at Portage Lake. Length samples in the latest survey that recorded them ran 6–15 inches. DNR survey details →
Portage Lake is a 128-acre mesotrophic lake in Cook County, Minnesota with a maximum depth of 55 feet (18-foot average). Overall water quality is declining over recent sampling years. The lake supports 3 documented fish species including green sunfish, splake, and white sucker. No public access — the lake is private or restricted. Compared to the 43 other monitored lakes in Cook County, Portage Lake ranks #7 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2020-09-15. Methodology: how these readings are compared.
What Portage Lake is good for
From access and monitoring records, not editorial picks.
- Fishing3 species recorded
- Deep water55 ft surveyed max depth
Swimming conditions
Readings onlyLimited data
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Portage Lake is safe to swim in today is a call for the Minnesota Pollution Control Agency and the Minnesota DNR and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Portage Lake
These are the measurements Minnesota PCA publishes for Portage Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Moderate clarity, visible to about 8.5 ft. Phosphorus 9.5 µg/L. Chlorophyll-a 3.3 µg/L. TSI 42.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 8.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 9.5µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 3.3µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 42 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Portage Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Portage Lake typically sits around 53°F at the surface in September. Summer average is about 57°F. Usually warmest in Jun (about 59°F) and coldest in Sep (about 53°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (53°F) to its warmest (59°F).
Typical surface water temperature by month, from 95 field readings (2018–2019) via the EPA Water Quality Portal. See the full Portage Lake water temperature breakdown →
Minnesota DNR's Standard Survey on June 8, 2022 caught 13.33 white sucker per gill net at Portage Lake. Length samples in the latest survey that recorded them ran 6–15 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Portage Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
9 surveys on file from MN DNR Fisheries. Most recent: 2022-06-08 (Standard Survey).
9 surveys on file · most recent 2022-06-08 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| White Sucker | 16.44 | 6–15 in 2022-06-08 | 0.71 lb |
| Fathead Minnow | 3.50 | ||
| Green Sunfish | 2.83 | 6 in 2022-06-08 | 0.08 lb |
| Golden Shiner | 0.67 | 5 in 2002-06-12 | 0.08 lb |
CPUE = catch per unit effort, fish caught per net per set in a standardised survey. It measures abundance, not size, and is not a weekly bite report.
Length Distributions
Number of fish caught at each inch class in the most recent survey that recorded lengths. Red dashed line marks an approximate trophy threshold for that species.
White Sucker
Green Sunfish
Golden Shiner
From the 2022-06-08 survey
Portage Lake is a designated stream trout lake that has been managed for Splake since 1982. The lake is located near the mid-Gunflint Trail area, about 35 miles from the City of Grand Marais. The most direct public access to the lake is from a 0.10-mile portage trail from the east end of Iron Lake which connects with…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Portage Lake. 2 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — PortageFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — PortageFish Stocking History · MN DNR LakeFinder
Lake Details
Max depth
55 ft
Average depth
17.8 ft
Surface area
128 acres
Shoreline
6.3 mi
Littoral zone
60%
Share shallower than 15 ft
Public access
No
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
2 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,873 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Stays via Stay22
Stays near Portage Lake
Compare lakeside cabins, hotels, and vacation rentals near Portage Lake in Cook County, Minnesota — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Portage Lake
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Follow Portage Lake’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing Portage Lake
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Phosphorus
Worsening+1.71 µg/L/yr6 years
Chlorophyll-a
Worsening+0.56 µg/L/yr6 years
Nearby Lakes in Cook County
Frequently asked questions about Portage Lake
Where is Portage Lake?
- Portage Lake is a lake in Cook County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Portage Lake?
- Portage Lake in Cook County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 8.5 ft visibility. Phosphorus: 9.5 µg/L. Chlorophyll-a (algae): 3.3 µg/L. Maximum depth: 55 ft. Surface area: 128.12 acres.
Is Portage Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Portage Lake?
- Portage Lake typically sits around 53°F at the surface in September, from 95 EPA Water Quality Portal field readings (2018–2019). That is a typical value for the month, not a live reading.
How deep is Portage Lake?
- Portage Lake has a maximum depth of 55 feet and an average depth of 17.8 feet. The lake covers 128.12 acres.
What fish are in Portage Lake?
- Fish species found in Portage Lake include green sunfish, splake, white sucker. Portage Lake is located in Cook County, Minnesota.
What did the DNR fisheries survey find at Portage Lake?
- Minnesota DNR's Standard Survey on June 8, 2022 caught 13.33 white sucker per gill net at Portage Lake. Length samples in the latest survey that recorded them ran 6–15 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Portage Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
Can I fish at Portage Lake?
- Public access to Portage Lake is listed as no on the lake record, so confirm before you make the trip. Seasons, size and bag limits, and whether you need a license are set by Minnesota's fish and wildlife agency, so check its current regulations before you go.
Explore Portage Lake across LakeQuality
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Where this data comes from
12 measurements from 1 monitoring station, 2020. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA12 samples · 2020
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder