Douglas County, Wisconsin · Water Quality Report Card
Lake Superior
Lake Superior in Douglas County, Wisconsin is not rated for water quality — its monitoring record does not meet the evidence bar. Phosphorus: 29 µg/L.
- Mean depth
- ~481 ft est.
- Type
- Eutrophic
- Trend
- → Stable
Lake Superior is a productive, nutrient-rich eutrophic lake in Douglas County, Wisconsin with an estimated average depth of about 481 feet. Water clarity is declining over recent sampling years.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2022-08-26. Grade methodology: LakeGrade methodology.
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Swimming Safety
Not rated for swimming — there is not enough monitoring data to judge this lake
Water Quality Grade: Not rated
No clarity data. Phosphorus level: 29 µg/L. Trophic State Index: 53.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No data | |
| Phosphorus | 29 µg/L | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 53 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Average Depth | ~481 ft est. |
Depth marked “est.” is a modeled estimate from HydroLAKES, not a measured survey. Wisconsin has not published bathymetry for Lake Superior.
Where to stay near Lake Superior
Compare lakeside cabins, hotels, and vacation rentals near Lake Superior in Douglas 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.
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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 |
Location
Nearby Lakes in Douglas County
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2 documented falls within 6 mi, nearest Upper Falls (Amnicon Falls State Park)
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High nutrients, frequent algae, reduced clarity
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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
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
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)
Grade thresholds come from the U.S. EPA National Lakes Assessment 2022 Technical Support Document (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated.
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion
Fish and recreation data from Wisconsin DNR Lakes
Most recent sample: 2022-08-26
Monitoring stations: 1