Portage Lake
Aitkin County, Minnesota372 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Portage Lake. Here is what has been measured.
- Impaired · Nutrients (phosphorus, nitrogen)
- 18 ft max depth
- Public access
- Limited data
Portage Lake in Aitkin County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 4.5 ft visibility. Maximum depth: 18 ft. Surface area: 372.44 acres.
Minnesota DNR's Targeted Survey on August 10, 2022 caught 1.42 largemouth bass per hour of electrofishing at Portage Lake. DNR survey details →
Portage Lake is a 372-acre lake in Aitkin County, Minnesota with a maximum depth of 18 feet (8-foot average). Overall water quality is declining over recent sampling years. The lake supports 11 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2022-08-07. Methodology: how these readings are compared.
What Portage Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
- Fishing11 species recorded
Swimming conditions
No readingRecreation use not supported
Nutrient and algae readings are not a swimming clearance. Portage Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). 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.
Murky, only visible to about 4.5 ft. TSI 55.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 4.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 55 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Portage Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Portage Lake typically sits around 65°F at the surface in September. Summer average is about 71°F. Usually warmest in Jul (about 73°F) and coldest in May (about 58°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (58°F) to its warmest (73°F).
Typical surface water temperature by month, from 43 field readings (2016–2017) via the EPA Water Quality Portal. See the full Portage Lake water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Portage Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was high (293,765 cells/mL) on May 23, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Minnesota DNR's Targeted Survey on August 10, 2022 caught 1.42 largemouth bass per hour of electrofishing at Portage Lake.
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 3 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
10 surveys on file from MN DNR Fisheries. Most recent: 2025-05-14 (Targeted Survey).
10 surveys on file · most recent 2025-05-14 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluegill | 24.14 | 3–9 in 2025-05-14 | 0.22 lb |
| Black Bullhead | 22.38 | 4–10 in 2022-06-27 | 0.43 lb |
| Yellow Perch | 11.00 | 5 in 2025-05-14 | 0.1 lb |
| Black Crappie | 9.91 | 7–14 in 2025-05-14 | 0.17 lb |
| Golden Shiner | 7.71 | 5–6 in 2022-06-27 | 0.12 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.
Bluegill
Black Bullhead
Yellow Perch
Black Crappie
From the 2025-05-14 survey
Portage Lake is 372 acres with an average depth of 8 feet and a maximum depth of 18 feet. A targeted panfish assessment was conducted on 5/14/2025. A total of 34 Bluegill were captured for a trap net catch rate of 5.7 per net. Bluegill averaged 6.7 inches with fish up to 9.3 inches observed. Fish ranged from 2 to 8…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Portage Lake. 3 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
- —Aquatic Plant Report — Portage (0077)Aquatic Plant Report · MN DNR LakeFinder
- —Public Water Access Sites — PortagePublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
18 ft
Average depth
8 ft
Surface area
372 acres
Shoreline
5.1 mi
Littoral zone
84%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
4 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,214 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Portage LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Portage Lake
Compare lakeside cabins, hotels, and vacation rentals near Portage Lake in Aitkin 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 readings over time
3 seasons of samples on record (2020–2022). Calling a direction takes at least 4 years of the same measurement.
Water clarity
Worsening3 years
EPA Impairment Status
Portage Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Recreation.
Source: EPA ATTAINS assessment unit MN01-0069-00 · Official waterbody report
Nearby Lakes in Aitkin County
Frequently asked questions about Portage Lake
Where is Portage Lake?
- Portage Lake is a lake in Aitkin 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 Aitkin County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 4.5 ft visibility. Maximum depth: 18 ft. Surface area: 372.44 acres.
Is Portage Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Portage Lake is listed impaired under Clean Water Act §303(d) (IR 5) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Portage Lake?
- Portage Lake typically sits around 65°F at the surface in September, from 43 EPA Water Quality Portal field readings (2016–2017). That is a typical value for the month, not a live reading.
How deep is Portage Lake?
- Portage Lake has a maximum depth of 18 feet and an average depth of 8 feet. The lake covers 372.44 acres.
What fish are in Portage Lake?
- Fish species found in Portage Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, yellow bullhead, yellow perch. Portage Lake is located in Aitkin County, Minnesota.
What did the DNR fisheries survey find at Portage Lake?
- Minnesota DNR's Targeted Survey on August 10, 2022 caught 1.42 largemouth bass per hour of electrofishing at Portage Lake. 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 3 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
Does Portage Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Portage Lake (clouds, ice, or an off-season gap). The most recent reading was high (293,765 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
Are there boat ramps on Portage Lake?
- Portage Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Portage Lake. Public access is listed as yes.
Can I fish at Portage Lake?
- Portage Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. 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
35 measurements from 1 monitoring station, 2020–2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA35 samples · 2020–2022
Analytical methods
- Field measurement/observation, generic method
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
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory