Unknown Lake
Unknown Lake in Grant County, Wisconsin has a water quality grade of D (Nutrient-rich). Water clarity: 2.4 ft visibility. Phosphorus: 135.5 µg/L.
- Clarity
- 2.4 ft
- Type
- Eutrophic
Grade D measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Unknown Lake →
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Unknown Lake is a productive, nutrient-rich eutrophic lake in Grant County, Wisconsin. Water quality is graded D based on 1 sampling years through 2022. Compared to the 2 other monitored lakes in Grant County, Unknown Lake ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2022-10-27. Grade methodology: LakeQuality methodology.
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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.
Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum
Water Quality Grade: D (Nutrient-rich)
Very murky, less than 2.4 ft of visibility. Phosphorus level: 135.5 µg/L. Trophic State Index: 70.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.4 ft | Not graded |
| Phosphorus | 135.5 µg/L | Poor |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 70 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Unknown Lake
Compare lakeside cabins, hotels, and vacation rentals near Unknown Lake in Grant 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. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Unknown Lake are listed below.
Top-rated places to stay near Unknown Lake
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Planning a whole trip? See where to stay at Wisconsin’s top lakes →
Fishing Unknown Lake
County Ranking
Ranked #3 of 3 lakes in Grant County
Nearby Lakes With Higher Grades
Unknown Lake holds Grade D. One nearby lake has a higher nutrient-and-algae grade — useful for a swim day, not a reason to skip lodging here.
Nearby Lakes in Grant County
Frequently asked questions about Unknown Lake
Where is Unknown Lake?
- Unknown Lake is a lake in Grant County, Wisconsin. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Unknown Lake?
- Unknown Lake in Grant County, Wisconsin has a water quality grade of D (Nutrient-rich). Water clarity: 2.4 ft visibility. Phosphorus: 135.5 µg/L.
Is Unknown Lake safe to swim in?
- Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum. Unknown Lake has a water quality grade of D (Nutrient-rich). Always check local health department advisories before swimming.
Explore Unknown Lake across LakeQuality
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Where this data comes from
24 measurements from 2 monitoring stations, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX24 samples · 2022
Analytical methods
- Phosphorus by Colorimetry
Monitoring station identifiers (2)
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.