Deep Portage Lake
Cass County, Minnesota129 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Deep Portage Lake. Here is what has been measured.
- Oligotrophic
- 105 ft max depth
Deep Portage Lake in Cass County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 15.4 ft visibility. Phosphorus: 9 µg/L. Chlorophyll-a (algae): 1.6 µg/L. Maximum depth: 105 ft. Surface area: 129.02 acres.
Minnesota DNR's Targeted Survey on August 9, 2017 caught 1.50 walleye per gill net at Deep Portage Lake. Length samples in the latest survey that recorded them ran 20–26 inches. DNR survey details →
Deep Portage Lake is a 129-acre cold, clear oligotrophic lake in Cass County, Minnesota with a maximum depth of 105 feet (40-foot average). Overall water quality is improving over recent sampling years. The lake supports 9 documented fish species including black crappie, bluegill, and largemouth bass. No public access — the lake is private or restricted. Compared to the 103 other monitored lakes in Cass County, Deep Portage Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-02. Methodology: how these readings are compared.
Deep Portage Lake covers about 130 acres in Cass County. For a place on the water, look through cabin and lake-house rentals near Deep Portage Lake on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.
What Deep Portage Lake is good for
From access and monitoring records, not editorial picks.
- Clear water15.4 ft of visibility
- Fishing9 species recorded
- Deep water105 ft surveyed max depth
Swimming conditions
Readings onlyLow algae
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 Deep 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 Deep Portage Lake
These are the measurements Minnesota PCA publishes for Deep Portage Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Crystal clear, you can see 15.4 ft down. Phosphorus 9 µg/L. Chlorophyll-a 1.6 µg/L. TSI 36.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 15.4ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 9µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 1.6µg/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. | 36 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Deep Portage Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Deep Portage Lake typically sits around 57°F at the surface in October. Summer average is about 66°F. Usually warmest in Jul (about 73°F) and coldest in Aug (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 (73°F).
Typical surface water temperature by month, from 84 field readings (2011–2025) via the EPA Water Quality Portal. See the full Deep Portage Lake water temperature breakdown →
Minnesota DNR's Targeted Survey on August 9, 2017 caught 1.50 walleye per gill net at Deep Portage Lake. Length samples in the latest survey that recorded them ran 20–26 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Deep Portage Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
5 surveys on file from MN DNR Fisheries. Most recent: 2024-08-01 (Targeted Survey).
5 surveys on file · most recent 2024-08-01 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Northern Pike | 7.70 | 14–30 in 2017-08-09 | 1.65 lb |
| Yellow Perch | 3.24 | 5 in 2001-08-13 | 0.13 lb |
| Walleye | 1.84 | 20–26 in 2017-08-09 | 3.1 lb |
| Bluegill | 1.74 | 4–7 in 2017-08-09 | 0.13 lb |
| Largemouth Bass | 1.55 | 7–15 in 2017-08-09 | 0.65 lb |
| Tullibee (Cisco) | 1.53 | 9 in 2017-08-09 | 0.32 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.
Northern Pike
Yellow Perch
Walleye
Bluegill
From the 2024-08-01 survey
Temperature and dissolved oxygen profiles were collected in the deepest basin in Deep Portage Lake on August 1, 2024, to evaluate the quantity and quality of cold, oxygenated water (i.e., oxythermal habitat) available to Cisco, also known as Tullibee, the most sensitive coldwater species present in this lake. Cisco…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Deep Portage Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — Deep PortageFisheries Lake Survey · MN DNR LakeFinder
Lake Details
Max depth
105 ft
Average depth
40 ft
Surface area
129 acres
Shoreline
1.8 mi
Littoral zone
24%
Share shallower than 15 ft
Public access
No
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
2 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,319 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Stays via Stay22
Stays near Deep Portage Lake
Compare lakeside cabins, hotels, and vacation rentals near Deep 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 Deep Portage Lake
Prices for Oct 9–11, 4 adults. Change dates on the map below.
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Follow Deep Portage Lake’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing Deep Portage Lake
- → Deep Portage Lake fishing: DNR survey catch rates, species & stocking
- → Deep Portage Lake fishing forecast & best times (species outlook + 14-day solunar calendar)
- → Deep Portage Lake fishing regulations (limits, seasons, special rules)
- → Is it safe to eat fish from Deep Portage Lake? (mercury & PFAS guide)
Water Quality Trend: Improving
Based on 6 years of monitoring (2020–2025).
Water clarity
Stable6 years
Phosphorus
Improving-0.81 µg/L/yr6 years
Chlorophyll-a
Stable-0.04 µg/L/yr6 years
Nearby Lakes in Cass County
Frequently asked questions about Deep Portage Lake
Where is Deep Portage Lake?
- Deep Portage Lake is a lake in Cass County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Deep Portage Lake?
- Deep Portage Lake in Cass County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 15.4 ft visibility. Phosphorus: 9 µg/L. Chlorophyll-a (algae): 1.6 µg/L. Maximum depth: 105 ft. Surface area: 129.02 acres.
Is Deep 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 Deep Portage Lake?
- Deep Portage Lake typically sits around 57°F at the surface in October, from 84 EPA Water Quality Portal field readings (2011–2025). That is a typical value for the month, not a live reading.
How deep is Deep Portage Lake?
- Deep Portage Lake has a maximum depth of 105 feet and an average depth of 40 feet. The lake covers 129.02 acres.
What fish are in Deep Portage Lake?
- Fish species found in Deep Portage Lake include black crappie, bluegill, largemouth bass, northern pike, pumpkinseed, rock bass, tullibee (cisco), walleye, yellow bullhead. Deep Portage Lake is located in Cass County, Minnesota.
What did the DNR fisheries survey find at Deep Portage Lake?
- Minnesota DNR's Targeted Survey on August 9, 2017 caught 1.50 walleye per gill net at Deep Portage Lake. Length samples in the latest survey that recorded them ran 20–26 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Deep Portage Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
Can I fish at Deep Portage Lake?
- Public access to Deep 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.
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Where this data comes from
42 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
MNPCA42 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 10200 H 2 ~ Chlorophyll a-b-c Determination by spectrophotometer
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