Tree Lake
Tree Lake in Portage County, Wisconsin has a water quality grade of B (Good). Water clarity: 7.4 ft visibility. Phosphorus: 20.1 µg/L. Maximum depth: 33 ft. Surface area: 73 acres.
Wisconsin DNR lists Largemouth Bass as common on Tree Lake. DNR survey details →
- Clarity
- 7.4 ft
- Typical in August
- 75°F
- Max depth
- 33 ft
- Area
- 73 acres
- Type
- Mesotrophic
- Trend
- ↓ Declining
- Public access
- Yes
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Tree Lake is a 73-acre mesotrophic lake in Portage 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 declining over recent sampling years. The lake supports 3 documented fish species including Panfish, Largemouth Bass, and Northern Pike. Public access is available with 1 public boat landing. Compared to the 13 other monitored lakes in Portage County, Tree Lake ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-22. Grade methodology: LakeQuality methodology.
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Swimming Safety
Grade onlyLow algae
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)
Moderate clarity, visible to about 7.4 ft. Phosphorus level: 20.1 µg/L. Trophic State Index: 48.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 7.4 ft | Not graded |
| Phosphorus | 20.1 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 48 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Tree Lake
Compare lakeside cabins, hotels, and vacation rentals near Tree Lake in Portage 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 Tree Lake
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Planning a whole trip? See where to stay at Wisconsin’s top lakes →
Water Temperature
Tree Lake typically sits around 75°F at the surface in August. Summer average is about 76°F. Usually warmest in Jul (about 79°F) and coldest in Feb (about 34°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 62 field readings (2024–2026) via the EPA Water Quality Portal. See the full Tree Lake water temperature breakdown →
Wisconsin DNR lists Largemouth Bass as common on Tree Lake.
A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality grades Tree Lake B from EPA Water Quality Portal chemistry, and the water-quality trend over 7 years of monitoring is declining. 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 1990. 1 station on file (most recent sample 2026).
Fish Species (DNR-rated)
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 33 ft |
| Surface Area | 73 acres |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Tree 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 Tree 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: ↓ Declining
Based on 7 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.3 m/yr | 7 |
| Phosphorus | ↓ Declining | +6.26 µg/L/yr | 4 |
County Ranking
Ranked #4 of 14 lakes in Portage County
Nearby Lakes in Portage County
Frequently asked questions about Tree Lake
Where is Tree Lake?
- Tree Lake is a lake in Portage County, Wisconsin. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Tree Lake?
- Tree Lake in Portage County, Wisconsin has a water quality grade of B (Good). Water clarity: 7.4 ft visibility. Phosphorus: 20.1 µg/L. Maximum depth: 33 ft. Surface area: 73 acres.
Is Tree Lake safe to swim in?
- Good for swimming, clear water with low algae levels. Tree Lake has a water quality grade of B (Good). Always check local health department advisories before swimming.
What is the water temperature of Tree Lake?
- Tree Lake typically sits around 75°F at the surface in August, from 62 EPA Water Quality Portal field readings (2024–2026). That is a typical value for the month, not a live reading.
How deep is Tree Lake?
- Tree Lake has a maximum depth of 33 feet. The lake covers 73 acres.
What fish are in Tree Lake?
- Fish species found in Tree Lake include Panfish, Largemouth Bass, Northern Pike. Tree Lake is located in Portage County, Wisconsin.
What did the DNR fisheries survey find at Tree Lake?
- Wisconsin DNR lists Largemouth Bass as common on Tree Lake. A DNR fisheries survey reports fish abundance and catch rates, not a water-quality grade. LakeQuality grades Tree Lake B from EPA Water Quality Portal chemistry, and the water-quality trend over 7 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
Are there boat ramps on Tree Lake?
- Tree Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Tree Lake. Public access is listed as yes.
Explore Tree Lake across LakeQuality
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Species activity outlook by water temperature and season
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Moderate nutrients, good water quality
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State Parks Near Tree Lake
Other Grade B Lakes in Wisconsin
Mesotrophic Lakes in Wisconsin
Where this data comes from
40 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_WQX40 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