Portage Lake
Portage Lake in Cass County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 12 ft visibility. Maximum depth: 65 ft. Surface area: 360.65 acres.
- Clarity
- 12 ft
- Max depth
- 65 ft
- Area
- 361 acres
- Trend
- → Stable
- Public access
- Yes
- Ice-out
- Apr 20
Next lake in Cass County
Why Portage Lake has no grade
We grade a lake only when its monitoring record clears the evidence bar: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Portage Lake, the only measurement available is water clarity, which is not a water-quality indicator on its own — EPA's National Lakes Assessment does not grade clarity. Sampling here has recorded water clarity, but not phosphorus and algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by MPCA and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Portage Lake is a 361-acre lake in Cass County, Minnesota with a maximum depth of 65 feet. The lake supports 13 documented fish species including black crappie, bluegill, and bowfin (dogfish). Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2021-09-21. Grade methodology: LakeGrade methodology.
Watch Portage Lake water quality
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Portage Lake
These readings exist but do not meet the evidence bar for an A–F grade — see why.
Good clarity, visible to about 12 ft. Trophic State Index: 41.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 12 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 41 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Portage Lake
Compare lakeside cabins, hotels, and vacation rentals near Portage Lake in Cass 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
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Minnesota’s top lakes →
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 moderate (23,768 cells/mL) on November 22, 2025.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 65 ft |
| Surface Area | 361 acres |
| Shoreline Length | 3.6 mi |
| Littoral Zone | 47% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Steamboat LakePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Portage Lake
DNR Fisheries Survey Summary
6 surveys on file from MN DNR Fisheries. Most recent: 1998-08-18 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Yellow Perch | 35.22 | 0.15 lb |
| Pumpkinseed | 5.77 | 0.23 lb |
| Bluegill | 4.13 | 0.41 lb |
| Northern Pike | 3.88 | 1.7 lb |
| Tullibee (Cisco) | 3.39 | 1.28 lb |
| Walleye | 3.18 | 1.94 lb |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
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.
Yellow Perch
Pumpkinseed
Bluegill
Northern Pike
From the 1998-08-18 survey
Portage Lake is a 356-acre lake with a maximum depth of 65 feet. The lake is located six miles south of Cass Lake in northern Cass County. The Minnesota Department of Natural Resources has classified Minnesota's lakes into 43 different lake classes based on physical and chemical characteristics. Portage Lake is in…
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 (1631)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — PortageFish Stocking History · MN DNR LakeFinder
Water Quality Trend: → Stable
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | 0 m/yr | 2 |
Ice Season
Historical ice data from Minnesota DNR (5 observations).
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2015-04-12 (2015) | 2008-04-21 (2008) |
| Ice-In | 2008-11-25 (2008) | 2005-11-30 (2005) |
Most recent ice-out: 2015-04-12
Graded lakes near Portage Lake
Portage Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Cass County
Frequently asked questions about Portage Lake
What is the water quality grade for Portage Lake?
- Portage Lake in Cass County, Minnesota is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 12 ft visibility. Maximum depth: 65 ft. Surface area: 360.65 acres.
Is Portage Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Portage Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
How deep is Portage Lake?
- Portage Lake has a maximum depth of 65 feet. The lake covers 360.65 acres.
What fish are in Portage Lake?
- Fish species found in Portage Lake include black crappie, bluegill, bowfin (dogfish), hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, smallmouth bass, tullibee (cisco), walleye, white sucker, yellow perch. Portage Lake is located in Cass County, Minnesota.
When does Portage Lake thaw?
- Portage Lake typically has ice-out around Apr 20.
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 moderate (23,768 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 Steamboat Lake. Public access is listed as yes.
Explore Portage Lake across LakeGrade
Fish species and top-graded lakes across Minnesota
Fish species and best lakes in Cass County
Species activity outlook by water temperature and season
Top lakes and where to stay in the Brainerd Lakes area
Where to stay at Minnesota's top lakes, each with its grade
Lakes in the Mississippi Headwaters, ranked by water quality
Lakes in the Pine River Watersheds (Brainerd Lakes), ranked by water quality
Minnesota's cleanest and most-polluted lakes, ranked
More Minnesota Lake Rankings
State Parks Near Portage Lake
Other Lakes in Minnesota
Mesotrophic Lakes in Minnesota
Where this data comes from
10 measurements from 1 monitoring station, 2020–2021. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA10 samples · 2020–2021
Analytical methods
- Field measurement/observation, generic method
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory
Ice data from Minnesota DNR Climate