Grand Portage Lake
Grand Portage Lake in Iron County, Wisconsin has a water quality grade of B (Good). Water clarity: 11.7 ft visibility. Phosphorus: 12.4 µg/L. Maximum depth: 33 ft. Surface area: 148 acres.
Wisconsin DNR lists Musky as common on Grand Portage Lake. DNR survey details →
- Clarity
- 11.7 ft
- Typical in August
- 72°F
- Max depth
- 33 ft
- Area
- 148 acres
- Type
- Mesotrophic
- Trend
- ↑ Improving
- Public access
- Yes
Next lake in Iron County
Swipe left or right on this bar to open the next or previous lake.
Grand Portage Lake is a 148-acre mesotrophic lake in Iron County, Wisconsin with a maximum depth of 33 feet. Water quality is graded B based on 1 sampling years through 2026. Overall water quality is improving over recent sampling years. The lake supports 6 documented fish species including Musky, Panfish, and Largemouth Bass. Public access is available with 2 public boat landings. Compared to the 15 other monitored lakes in Iron County, Grand Portage Lake ranks #12 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-09. Grade methodology: LakeQuality methodology.
Watch Grand Portage Lake water quality
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
Swimming Safety
Grade onlyLimited data
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Good for swimming, clear water with low algae levels
Water Quality Grade: B (Good)
Good clarity, visible to about 11.7 ft. Phosphorus level: 12.4 µg/L. Trophic State Index: 41.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 11.7 ft | Not graded |
| Phosphorus | 12.4 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 41 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Grand Portage Lake
Compare lakeside cabins, hotels, and vacation rentals near Grand Portage Lake in Iron 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 Grand 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 Wisconsin’s top lakes →
Water Temperature
Grand Portage Lake typically sits around 72°F at the surface in August. Summer average is about 74°F. Usually warmest in Jul (about 76°F) and coldest in Apr (about 49°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 16 field readings (2024–2025) via the EPA Water Quality Portal. See the full Grand Portage Lake water temperature breakdown →
Wisconsin DNR lists Musky as common on Grand Portage Lake.
A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality grades Grand Portage Lake B from EPA Water Quality Portal chemistry, and the water-quality trend over 7 years of monitoring is improving. 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 2009. 2 stations on file (most recent sample 2025).
Fish Species (DNR-rated)
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 33 ft |
| Surface Area | 148 acres |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Echo LakePublic
- Grand Portage LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Grand 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.
Water Quality Trend: ↑ Improving
Based on 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | -0.136 m/yr | 6 |
| Phosphorus | ↑ Improving | -1.12 µg/L/yr | 7 |
County Ranking
Ranked #12 of 16 lakes in Iron County
Nearby Lakes in Iron County
Frequently asked questions about Grand Portage Lake
Where is Grand Portage Lake?
- Grand Portage Lake is a lake in Iron County, Wisconsin. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Grand Portage Lake?
- Grand Portage Lake in Iron County, Wisconsin has a water quality grade of B (Good). Water clarity: 11.7 ft visibility. Phosphorus: 12.4 µg/L. Maximum depth: 33 ft. Surface area: 148 acres.
Is Grand Portage Lake safe to swim in?
- Good for swimming, clear water with low algae levels. Grand Portage Lake has a water quality grade of B (Good). Always check local health department advisories before swimming.
What is the water temperature of Grand Portage Lake?
- Grand Portage Lake typically sits around 72°F at the surface in August, from 16 EPA Water Quality Portal field readings (2024–2025). That is a typical value for the month, not a live reading.
How deep is Grand Portage Lake?
- Grand Portage Lake has a maximum depth of 33 feet. The lake covers 148 acres.
What fish are in Grand Portage Lake?
- Fish species found in Grand Portage Lake include Musky, Panfish, Largemouth Bass, Smallmouth Bass, Northern Pike, Walleye. Grand Portage Lake is located in Iron County, Wisconsin.
What did the DNR fisheries survey find at Grand Portage Lake?
- Wisconsin DNR lists Musky as common on Grand Portage Lake. A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality grades Grand Portage Lake B from EPA Water Quality Portal chemistry, and the water-quality trend over 7 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
Are there boat ramps on Grand Portage Lake?
- Grand Portage Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Echo Lake, Grand Portage Lake. Public access is listed as yes.
Explore Grand Portage Lake across LakeQuality
Fish species and top-graded lakes across Wisconsin
Fish species and best lakes in Iron County
Species activity outlook by water temperature and season
Top lakes and where to stay in the Northwoods Wisconsin area
Where to stay at Wisconsin's top lakes, each with its grade
Lakes in the Lake Superior Basin (MN+WI), ranked by water quality
Moderate nutrients, good water quality
Wisconsin's cleanest and most-polluted lakes, ranked
More Wisconsin Lake Rankings
Other Grade B Lakes in Wisconsin
Mesotrophic Lakes in Wisconsin
Where this data comes from
38 measurements from 1 monitoring station, 2020–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX38 samples · 2020–2026
Analytical methods
- Phosphorus by Colorimetry
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)
Fish and recreation data from Wisconsin DNR Lakes
Named boat-access points from the USGS National Boat Ramps inventory