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: 21 ft visibility. Maximum depth: 84 ft. Surface area: 277.27 acres.
- Clarity
- 21 ft
- Max depth
- 84 ft
- Area
- 277 acres
- Trend
- → Stable
- Public access
- No
- Ice-out
- Apr 27
- Open water
- 217 days
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 277-acre lake in Cass County, Minnesota with a maximum depth of 84 feet. The lake supports 10 documented fish species including black crappie, bluegill, and hybrid sunfish. No public access — the lake is private or restricted.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-08-12. Grade methodology: LakeGrade methodology.
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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.
Crystal clear, you can see 21 ft down. Trophic State Index: 33.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 21 ft | Not graded |
| Phosphorus | No recent samples | |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 33 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
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
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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 (21,281 cells/mL) on June 6, 2026.
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 | 84 ft |
| Surface Area | 277 acres |
| Shoreline Length | 3.1 mi |
| Littoral Zone | 34% |
| Public Access | No |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Portage Lake
DNR Fisheries Survey Summary
13 surveys on file from MN DNR Fisheries. Most recent: 2025-07-07 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluntnose Minnow | 32.39 | — |
| MMS | 22.41 | — |
| Largemouth Bass | 18.00 | 0.85 lb |
| Bluegill | 15.43 | 0.11 lb |
| JND | 8.99 | — |
| Smallmouth Bass | 6.07 | 1.09 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.
Largemouth Bass
Bluegill
JND
Smallmouth Bass
From the 2025-07-07 survey
Portage Lake (DOW# 11-0476; Lake Class 23) is a 277-acre lake with 95 littoral acres, 3.1 miles of shoreline and a maximum depth of 84 feet located near Hackensack, MN. A US Forest Service owned public access is located on the south shore. The Minnesota Department of Natural Resources has classified Minnesota's lakes…
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 (1460)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — PortageFish Stocking History · MN DNR LakeFinder
Water Quality Trend: → Stable
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.039 m/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (12 observations).
Estimated open water season: 217 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2007-04-21 (2007) | 2004-05-19 (2004) |
| Ice-In | 2002-11-24 (2002) | 2004-12-14 (2004) |
Most recent ice-out: 2020-04-26
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
Source: EPA ATTAINS assessment unit MN11-0476-00 · Official waterbody report
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: 21 ft visibility. Maximum depth: 84 ft. Surface area: 277.27 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 84 feet. The lake covers 277.27 acres.
What fish are in Portage Lake?
- Fish species found in Portage Lake include black crappie, bluegill, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, smallmouth bass, 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 27. Ice typically forms around Nov 30. The open water season is approximately 217 days.
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 (21,281 cells/mL). Blue-green algae can appear and clear within days, so check Minnesota's current advisory before swimming.
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Where this data comes from
33 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA33 samples · 2020–2025
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
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Ice data from Minnesota DNR Climate