Boulder Lake
Oconto County, Wisconsin370 acresView mapDirections
Wisconsin DNR publishes the water-quality measurements for Boulder Lake. Here is what has been measured.
- Mesotrophic
- 11 ft max depth
- Public access
Boulder Lake in Oconto County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 11 ft visibility. Phosphorus: 13.3 µg/L. Maximum depth: 11 ft. Surface area: 370 acres.
Wisconsin DNR lists Panfish as common on Boulder Lake. DNR survey details →
Boulder Lake is a 370-acre mesotrophic lake in Oconto County, Wisconsin with a maximum depth of 11 feet. Overall water quality is improving over recent sampling years. The lake supports 5 documented fish species including Panfish, Largemouth Bass, and Smallmouth Bass. Public access is available with 1 public boat landing. Compared to the 38 other monitored lakes in Oconto County, Boulder Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-05-31. Methodology: how these readings are compared.
Boulder Lake covers about 370 acres in Oconto County. It has one public boat landing. If you are planning to stay, you can search lake houses and cabins around Boulder Lake on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.
What Boulder Lake is good for
From access and monitoring records, not editorial picks.
- Clear water11 ft of visibility
- Boat launch1 documented ramp
- Fishing5 species recorded
- Camping1 public campground nearby
Swimming conditions
Readings onlyLow algae
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.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Boulder 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 Boulder Lake
These are the measurements Wisconsin DNR publishes for Boulder Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Good clarity, visible to about 11 ft. Phosphorus 13.3 µg/L. TSI 42.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 11ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 13.3µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 42 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Boulder Lake
Answers come straight from the public measurements and survey records on this page.
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Boulder Lake — clouds, ice, or an off-season gap in coverage. The most recent reading was high (178,649 cells/mL) on May 16, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Wisconsin DNR lists Panfish as common on Boulder Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Boulder Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is improving. 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 2003. 1 station on file (most recent sample 2025).
Fish Species (DNR-rated)
DNR Reports & Resources
Wisconsin DNR Fisheries scientists publish multi-year survey reports for Boulder Lake covering fish populations, stocking, water quality, and management. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- 2021Boulder Lake comprehensive summary report, 2021Comprehensive Survey · WI DNR · 2021 (PDF)
Lake Details
Max depth
11 ft
Surface area
370 acres
Public access
Yes
Listed by Wisconsin DNR
Lake Size & Watershed
Watershed (drainage) area
2 sq mi
HydroLAKES / HydroSHEDS
Shoreline
3.4 mi
HydroLAKES / HydroSHEDS
Elevation
1,106 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Boulder Lake CampgroundPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Public campgrounds near Boulder Lake
- Boulder Lake1.0 km
Nearest public campgrounds in the USGS National Map inventory, within about 3 miles. An empty list means USGS records no campground that close, which is not the same as camping being unavailable. Where the source gives an official reservation link, it is used; the cabin and hotel search does not cover campsites. More camping lakes
Stays via Stay22
Stays near Boulder Lake
Compare lakeside cabins, hotels, and vacation rentals near Boulder Lake in Oconto 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 Boulder Lake
Prices for Oct 16–18, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a whole trip? See where to stay at Wisconsin’s top lakes →
Follow Boulder Lake’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing Boulder 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: Improving
Based on 6 years of monitoring (2020–2025).
Water clarity
Stable6 years
Phosphorus
Improving-0.43 µg/L/yr6 years
Nearby Lakes in Oconto County
Frequently asked questions about Boulder Lake
Where is Boulder Lake?
- Boulder Lake is a lake in Oconto County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.
What is the water quality of Boulder Lake?
- Boulder Lake in Oconto County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 11 ft visibility. Phosphorus: 13.3 µg/L. Maximum depth: 11 ft. Surface area: 370 acres.
Is Boulder Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
How deep is Boulder Lake?
- Boulder Lake has a maximum depth of 11 feet. The lake covers 370 acres.
What fish are in Boulder Lake?
- Fish species found in Boulder Lake include Panfish, Largemouth Bass, Smallmouth Bass, Northern Pike, Walleye. Boulder Lake is located in Oconto County, Wisconsin.
What did the DNR fisheries survey find at Boulder Lake?
- Wisconsin DNR lists Panfish as common on Boulder Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Boulder Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is improving. Catch rate is not a swim clearance and is not a weekly bite report.
Does Boulder Lake have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Boulder Lake (clouds, ice, or an off-season gap). The most recent reading was high (178,649 cells/mL). Blue-green algae can appear and clear within days, so check Wisconsin's current advisory before swimming.
Are there boat ramps on Boulder Lake?
- Boulder Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Boulder Lake Campground. Public access is listed as yes.
Can I fish at Boulder Lake?
- Boulder Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Wisconsin's fish and wildlife agency, so check its current regulations before you go.
Are there campgrounds on Boulder Lake?
- Boulder Lake has 1 public campground from USGS The National Map within 5 km, including Boulder Lake. This is a location join, not a booking. Cabins and hotels are listed separately; campsite reservations use the official link when the source provides one.
Explore Boulder Lake across LakeQuality
Fish species and the cleanest lakes across Wisconsin
Fish species and best lakes in Oconto County
Species activity outlook by water temperature and season
Where to stay at Wisconsin's top lakes, each with its readings
Wisconsin's cleanest lakes, ranked on agency measurements
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State Parks Near Boulder Lake
Other Lakes in Wisconsin
Mesotrophic Lakes in Wisconsin
Where this data comes from
46 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_WQX46 samples · 2020–2026
Analytical methods
- Phosphorus by Colorimetry
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)
Fish and recreation data from Wisconsin DNR Lakes
Named boat-access points from the USGS National Boat Ramps inventory
Public campgrounds from USGS The National Map Structures, within about 3 miles