Lake Superior
Douglas County, WisconsinView mapDirections
Wisconsin DNR publishes the water-quality measurements for Lake Superior. Here is what has been measured.
- Impaired · Mercury
- Limited data
Ask about Lake Superior
Answers come straight from the public measurements and survey records on this page.
Lake Superior in Douglas County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Phosphorus: 29 µg/L.
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Lake Superior is a lake in Douglas County, Wisconsin. Water clarity is declining over recent sampling years. Public access is available with 1 public boat landing.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2022-08-26. Grade methodology: LakeQuality methodology.
What Lake Superior is good for
From access and monitoring records, not editorial picks.
- Boat launch1 documented ramp
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Lake Superior is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, pFAS, pCBs. Check local advisories before you swim.
Whether Lake Superior 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.
Water quality measurements for Lake Superior
These are the measurements Wisconsin DNR publishes for Lake Superior, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. Phosphorus 29 µg/L. TSI 53.
| Metric | Value | EPA condition class |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 29 µg/L | Measured, not scored |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 53 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Recreation & Access
- Amnicon RiverSemi-private
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Lake Superior
Water Quality Trend: → Stable
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -3.7 m/yr | 2 |
| Phosphorus | ↑ Improving | -1 µg/L/yr | 5 |
EPA Impairment Status
Lake Superior 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 WI10008955 · Official waterbody report
Nearby Lakes in Douglas County
Frequently asked questions about Lake Superior
Where is Lake Superior?
- Lake Superior is a lake in Douglas County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.
What is the water quality of Lake Superior?
- Lake Superior in Douglas County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Phosphorus: 29 µg/L.
Is Lake Superior safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Lake Superior is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, pFAS, pCBs. Check local advisories before you swim.
Are there boat ramps on Lake Superior?
- Lake Superior has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Amnicon River.
Explore Lake Superior across LakeQuality
2 documented falls within 6 mi, nearest Upper Falls (Amnicon Falls State Park)
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Where this data comes from
1 measurement from 1 monitoring station, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- USGS Wisconsin Water Science Center
USGS-WI1 sample · 2022
Analytical methods
- Phosphorus, wu,FIA EPA365.4 (WI)
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
Impairment status from EPA ATTAINS 303(d) database
Fish and recreation data from Wisconsin DNR Lakes
Named boat-access points from the USGS National Boat Ramps inventory