Where is Big Portage Lake?

Big Portage Lake is a lake in Vilas County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.

What is the water temperature of Big Portage Lake?

Big Portage Lake typically sits around 66°F at the surface in September, from 36 EPA Water Quality Portal field readings (2024–2026). That is a typical value for the month, not a live reading.

How deep is Big Portage Lake?

Big Portage Lake has a maximum depth of 40 feet. The lake covers 586 acres.

What fish are in Big Portage Lake?

Fish species found in Big Portage Lake include Panfish, Largemouth Bass, Smallmouth Bass, Walleye. Big Portage Lake is located in Vilas County, Wisconsin.

Are there boat ramps on Big Portage Lake?

Big Portage Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Big Portage Lake. Public access is listed as yes.

Can I fish at Big Portage Lake?

Big 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 Wisconsin's fish and wildlife agency, so check its current regulations before you go.

Big Portage Lake

Vilas County, Wisconsin586 acresView map Directions

Wisconsin DNR publishes the water-quality measurements for Big Portage Lake. Here is what has been measured.

Clarity

18.5 ft

Clearer than most

Secchi · sampled 2026

Phosphorus

12 µg/L

Less phosphorus than most

Measured by Wisconsin DNR

Water temp

~66°F

Typical for Sep · EPA WQP

Max depth

40 ft

Bathymetric survey

Area

586 acres

Surface area

Type

Oligotrophic

Trophic class

Oligotrophic
Rusty Crayfish
40 ft max depth
Public access

See the measurements Directions Where to stay

Big Portage Lake in Vilas County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 18.5 ft visibility. Phosphorus: 12 µg/L. Maximum depth: 40 ft. Surface area: 586 acres.

Wisconsin DNR lists Smallmouth Bass as common on Big Portage Lake. DNR survey details →

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Big Portage Lake is a 586-acre cold, clear oligotrophic lake in Vilas County, Wisconsin with a maximum depth of 40 feet. Water clarity is improving over recent sampling years. The lake supports 4 documented fish species including Panfish, Largemouth Bass, and Smallmouth Bass. Public access is available with 1 public boat landing. Compared to the 102 other monitored lakes in Vilas County, Big Portage Lake ranks #33 for water quality.

Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-19. Methodology: how these readings are compared.

Big Portage Lake covers about 590 acres in Vilas County. It has one public boat landing. For a place on the water, look through cabin and lake-house rentals near Big Portage Lake on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.

What Big Portage Lake is good for

From access and monitoring records, not editorial picks.

Clear water18.5 ft of visibility
Boat launch1 documented ramp
Fishing4 species recorded
Deep water40 ft surveyed max depth

Swimming conditions

Readings only

Low 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 Big Portage Lake is safe to swim in today is a call for the Wisconsin Department of Natural Resources and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.

Compare swimming lakes near Eagle River →

Get alerts for Big Portage Lake →

Water quality measurements for Big Portage Lake

These are the measurements Wisconsin DNR publishes for Big 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 18.5 ft down. Phosphorus 12 µg/L. TSI 38.

Water quality readings
Measure	Reading	Where it sits
Water clarity (Secchi depth)	18.5ft	Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer.
Total phosphorus	12µg/L	Good GoodFairPoor
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.	38	Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic

Low nutrients, clear water. No reading is a swimming clearance.

Ask about Big Portage Lake

Answers come straight from the public measurements and survey records on this page.

Water Temperature

Big Portage Lake typically sits around 66°F at the surface in September. Summer average is about 71°F. Usually warmest in Jul (about 74°F) and coldest in May (about 61°F). These are typical values by month — not a live reading.

Jan

Feb

Mar

Apr

61°

May

70°

Jun

74°

Jul

70°

Aug

66°

Sep

Oct

Nov

Dec

Column height runs from this lake’s coldest month (61°F) to its warmest (74°F).

Typical surface water temperature by month, from 36 field readings (2024–2026) via the EPA Water Quality Portal. See the full Big Portage Lake water temperature breakdown →

Blue-Green Algae (Cyanobacteria)

No current satellite reading

There’s no recent EPA CyAN cyanobacteria estimate for Big Portage Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was moderate (82,414 cells/mL) on April 25, 2026.

Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗

DNR fisheries survey

Wisconsin DNR lists Smallmouth Bass as common on Big Portage Lake.

A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Big Portage Lake’s water-quality measurements separately, and the water-quality trend over 7 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.

WI DNR Lake Profile

Authoritative data from the Wisconsin DNR LakePages. Monitored by volunteers since 1991. 2 stations on file (most recent sample 2025).

DNR Assessment

Excellent · Deep Seepage lake

Trophic State Index 40 (oligotrophic) · 5-year average

Fish Species (DNR-rated)

Smallmouth Bass(Common)Walleye(Common)Panfish(Present)Largemouth Bass(Present)

Contour map (PDF) →Full WI DNR LakePage →Water quality stations →

Lake Details

Max depth

40 ft

Surface area

586 acres

Public access

Yes

Listed by Wisconsin DNR

Lake Size & Watershed

Watershed (drainage) area

5 sq mi

HydroLAKES / HydroSHEDS

Shoreline

6 mi

HydroLAKES / HydroSHEDS

Elevation

1,686 ft

Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).

Recreation & Access

Boat Landings

Yes

Public Access

Big 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 Big Portage Lake

Compare lakeside cabins, hotels, and vacation rentals near Big Portage Lake in Vilas County, Wisconsin — 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 Big Portage Lake

Prices for Oct 9–11, 4 adults. Change dates on the map below.

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 Wisconsin’s top lakes →

Follow Big Portage Lake’s readings

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Fish Species

Panfish Largemouth Bass Smallmouth Bass Walleye

Click a species to see every lake where it is documented.

Fishing Big Portage Lake

Invasive & Introduced Species

Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.

Banded Mystery SnailChinese Mystery SnailRusty Crayfish

Water Quality Trend: Stable

Based on 7 years of monitoring (2020–2026).

Water clarity
Improving
7 years
Phosphorus
Worsening
+2.88 µg/L/yr6 years

See year-by-year chart →

Nearby Lakes in Vilas County

Little Portage Lake6.4 ft clear · Mesotrophic—View →Deer Lake12 ft clear—View →Osceola Lake—View →Pinkeye Lake—View →Kenu Lake2.2 ft clear—View →Heart Lake—View →

Frequently asked questions about Big Portage Lake

Where is Big Portage Lake?: Big Portage Lake is a lake in Vilas County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.
What is the water quality of Big Portage Lake?: Big Portage Lake in Vilas County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 18.5 ft visibility. Phosphorus: 12 µg/L. Maximum depth: 40 ft. Surface area: 586 acres.
Is Big 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 Big Portage Lake?: Big Portage Lake typically sits around 66°F at the surface in September, from 36 EPA Water Quality Portal field readings (2024–2026). That is a typical value for the month, not a live reading.
How deep is Big Portage Lake?: Big Portage Lake has a maximum depth of 40 feet. The lake covers 586 acres.
What fish are in Big Portage Lake?: Fish species found in Big Portage Lake include Panfish, Largemouth Bass, Smallmouth Bass, Walleye. Big Portage Lake is located in Vilas County, Wisconsin.
What did the DNR fisheries survey find at Big Portage Lake?: Wisconsin DNR lists Smallmouth Bass as common on Big Portage Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Big Portage Lake’s water-quality measurements separately, and the water-quality trend over 7 years of monitoring is stable. Catch rate is not a swim clearance and is not a weekly bite report.
Does Big Portage Lake have blue-green algae?: There is no recent EPA CyAN cyanobacteria estimate for Big Portage Lake (clouds, ice, or an off-season gap). The most recent reading was moderate (82,414 cells/mL). Blue-green algae can appear and clear within days, so check Wisconsin's current advisory before swimming.
Are there boat ramps on Big Portage Lake?: Big Portage Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Big Portage Lake. Public access is listed as yes.
Can I fish at Big Portage Lake?: Big 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 Wisconsin's fish and wildlife agency, so check its current regulations before you go.

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Compare Big Portage Lake With Nearby Lakes

Big Portage Lake vs Boulder Lake

Vilas County · 5.6 ft

Where this data comes from

167 measurements from 2 monitoring stations, 2020–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.

Collected and reported by

Wisconsin Department of Natural ResourcesWIDNR_WQX167 samples · 2020–2026

Analytical methods

Phosphorus by Colorimetry

Monitoring station identifiers (2)

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)

Fish and recreation data from Wisconsin DNR Lakes

Named boat-access points from the USGS National Boat Ramps inventory