Devil'S Lake
Forest County, WisconsinView mapDirections
Wisconsin DNR publishes the water-quality measurements for Devil'S Lake. Here is what has been measured.
- Mesotrophic
- 24 ft max depth
Devil'S Lake in Forest County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Phosphorus: 22 µg/L. Chlorophyll-a (algae): 2.5 µg/L.
Devil'S Lake is a mesotrophic lake in Forest County, Wisconsin with an estimated average depth of about 24 feet. Overall water quality is declining over recent sampling years. Compared to the 22 other monitored lakes in Forest County, Devil'S Lake ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2025-10-22. Methodology: how these readings are compared.
Swimming conditions
Readings onlyBacteria tested: low
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.
Based on E. coli testing, Devil'S Lake never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 12 samples across 5 seasons.
This is a historical summary of past testing, not a current condition — bacteria levels change quickly, especially after rain. Always check Wisconsin’s current beach and health-department advisories before swimming.
Whether Devil'S 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.
Water quality measurements for Devil'S Lake
These are the measurements Wisconsin DNR publishes for Devil'S Lake, 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 22 µg/L. Chlorophyll-a 2.5 µg/L. TSI 44.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | No reading How deep a black-and-white disk stays visible from the surface. Higher is clearer. | |
| Total phosphorus | 22µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 2.5µg/L | Good GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 44 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Devil'S Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Devil'S Lake typically sits around 48°F at the surface in October. Summer average is about 53°F. Usually warmest in Jul (about 55°F) and coldest in Apr (about 46°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (46°F) to its warmest (55°F).
Typical surface water temperature by month, from 80 field readings (2024–2025) via the EPA Water Quality Portal. See the full Devil'S Lake water temperature breakdown →
Lake Details
Max depth
~24 ft est.
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Wisconsin has not published bathymetry for Devil'S Lake.
Lake Size & Watershed
Watershed (drainage) area
0 sq mi
HydroLAKES / HydroSHEDS
Surface area
30 acres
HydroLAKES / HydroSHEDS
Shoreline
0.9 mi
HydroLAKES / HydroSHEDS
Elevation
1,726 ft
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.
Stays via Stay22
Stays near Devil'S Lake
Compare lakeside cabins, hotels, and vacation rentals near Devil'S Lake in Forest 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 Devil'S Lake
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Fishing Devil'S Lake
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Phosphorus
Worsening+1.04 µg/L/yr6 years
Chlorophyll-a
Worsening+0.43 µg/L/yr6 years
Nearby Lakes in Forest County
Frequently asked questions about Devil'S Lake
Where is Devil'S Lake?
- Devil'S Lake is a lake in Forest County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.
What is the water quality of Devil'S Lake?
- Devil'S Lake in Forest County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Phosphorus: 22 µg/L. Chlorophyll-a (algae): 2.5 µg/L.
Is Devil'S Lake safe to swim in?
- Based on E. coli testing, Devil'S Lake never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 12 samples across 5 seasons. That is a historical summary of past bacteria testing, not a current reading and not a swimming clearance. Bacteria levels can spike quickly after heavy rain, so whether Devil'S Lake is safe to swim in today is a call for Wisconsin's water agency and the county health department; check their current beach advisories before you swim.
What is the water temperature of Devil'S Lake?
- Devil'S Lake typically sits around 48°F at the surface in October, from 80 EPA Water Quality Portal field readings (2024–2025). That is a typical value for the month, not a live reading.
How deep is Devil'S Lake?
- No published bathymetric survey covers Devil'S Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 24 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
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Where this data comes from
80 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Forest County Potawatomi Community (Tribal)
FCPOTAWATOMI_WQX80 samples · 2020–2025
Analytical methods
- 4500 P E ~ Phosphorus in Water by Colorimetry- Ascorbic Acid Method
- 4500 P F ~ Phosphorus in Water by Colorimetry Automated Ascorbic Acid Method
- 10200 H ~ Chlorophyll a-b-c Determination
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
Lake size & watershed from HydroLAKES (HydroSHEDS)