Boulder Lake
Hubbard County, Minnesota341 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Boulder Lake. Here is what has been measured.
- Mesotrophic
- Impaired · Mercury
- 28 ft max depth
- Public access
Boulder Lake in Hubbard County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 10.8 ft visibility. Phosphorus: 16 µg/L. Chlorophyll-a (algae): 6.2 µg/L. Maximum depth: 28 ft. Surface area: 340.54 acres.
Minnesota DNR's Standard Survey on August 21, 2023 caught 2.89 walleye per gill net at Boulder Lake. DNR survey details →
Boulder Lake is a 341-acre mesotrophic lake in Hubbard County, Minnesota with a maximum depth of 28 feet. Overall water quality is improving over recent sampling years. The lake supports 14 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 1 public boat landing. Compared to the 67 other monitored lakes in Hubbard County, Boulder Lake ranks #44 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-22. Methodology: how these readings are compared.
What Boulder Lake is good for
From access and monitoring records, not editorial picks.
- Clear water10.8 ft of visibility
- Boat launch1 documented ramp
- Fishing14 species recorded
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. Boulder Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether Boulder Lake is safe to swim in today is a call for the Minnesota Pollution Control Agency and the Minnesota DNR 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 Minnesota PCA 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 10.8 ft. Phosphorus 16 µg/L. Chlorophyll-a 6.2 µg/L. TSI 45.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 10.8ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 16µg/L | Good GoodFairPoor |
| Chlorophyll-a (algae) | 6.2µg/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. | 45 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Boulder Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Boulder Lake typically sits around 77°F at the surface in August. Summer average is about 74°F. Usually warmest in Aug (about 77°F) and coldest in May (about 57°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (57°F) to its warmest (77°F).
Typical surface water temperature by month, from 8 field readings (2011–2021) via the EPA Water Quality Portal. See the full Boulder Lake water temperature breakdown →
Minnesota DNR's Standard Survey on August 21, 2023 caught 2.89 walleye per gill net at 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.
DNR Fisheries Survey Summary
12 surveys on file from MN DNR Fisheries. Most recent: 2023-08-21 (Standard Survey).
12 surveys on file · most recent 2023-08-21 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluntnose Minnow | 19.11 | ||
| Largemouth Bass | 17.48 | 5–18 in 2023-08-21 | 0.78 lb |
| Yellow Perch | 12.56 | 5–10 in 2023-08-21 | 0.15 lb |
| Smallmouth Bass | 8.26 | 6–17 in 2023-08-21 | 0.71 lb |
| Bluegill | 6.36 | 2–8 in 2023-08-21 | 0.18 lb |
CPUE = catch per unit effort, fish caught per net per set in a standardised survey. It measures abundance, not size, and is not a weekly bite report.
Length Distributions
Number of fish caught at each inch class in the most recent survey that recorded lengths. Red dashed line marks an approximate trophy threshold for that species.
Largemouth Bass
Yellow Perch
Smallmouth Bass
Bluegill
From the 2023-08-21 survey
Boulder Lake is located in southern Hubbard County, 1.5 miles northeast of Dorset. Boulder has a surface area of 340 acres and a maximum depth of 28 feet. A public access with a concrete ramp is located on the west shore. Boulder provides angling opportunities for Walleye, Northern Pike, panfish, Largemouth Bass, and…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Boulder Lake. 4 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — BoulderFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Boulder (1303)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — BoulderFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — BoulderPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
28 ft
Surface area
341 acres
Shoreline
4.9 mi
Littoral zone
53%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
2 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,414 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Boulder LakePublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Boulder Lake
Compare lakeside cabins, hotels, and vacation rentals near Boulder Lake in Hubbard County, Minnesota — 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
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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
Improving6 years
Phosphorus
Improving-1.49 µg/L/yr6 years
Chlorophyll-a
Improving-0.8 µg/L/yr6 years
EPA Impairment Status
Boulder Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN29-0162-00 · Official waterbody report
Nearby Lakes in Hubbard County
Frequently asked questions about Boulder Lake
Where is Boulder Lake?
- Boulder Lake is a lake in Hubbard County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Boulder Lake?
- Boulder Lake in Hubbard County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 10.8 ft visibility. Phosphorus: 16 µg/L. Chlorophyll-a (algae): 6.2 µg/L. Maximum depth: 28 ft. Surface area: 340.54 acres.
Is Boulder Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Boulder Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
What is the water temperature of Boulder Lake?
- Boulder Lake typically sits around 77°F at the surface in August, from 8 EPA Water Quality Portal field readings (2011–2021). That is a typical value for the month, not a live reading.
How deep is Boulder Lake?
- Boulder Lake has a maximum depth of 28 feet. The lake covers 340.54 acres.
What fish are in Boulder Lake?
- Fish species found in Boulder Lake include black bullhead, black crappie, bluegill, brown bullhead, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, rock bass, smallmouth bass, walleye, white sucker, yellow bullhead, yellow perch. Boulder Lake is located in Hubbard County, Minnesota.
What did the DNR fisheries survey find at Boulder Lake?
- Minnesota DNR's Standard Survey on August 21, 2023 caught 2.89 walleye per gill net at 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.
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. 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 Minnesota's fish and wildlife agency, so check its current regulations before you go.
Explore Boulder Lake across LakeQuality
Depth, room, public access, and the state wake-sport rules
Fish species and the cleanest lakes across Minnesota
Fish species and best lakes in Hubbard County
Species activity outlook by water temperature and season
Top lakes and where to stay in the Park Rapids Area area
Where to stay at Minnesota's top lakes, each with its readings
Lakes in the Mississippi Headwaters, ranked by water quality
Minnesota's cleanest lakes, ranked on agency measurements
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State Parks Near Boulder Lake
Other Lakes in Minnesota
Mesotrophic Lakes in Minnesota
Where this data comes from
82 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA82 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Two Reagent Colorimetry
- 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
Impairment status from EPA ATTAINS 303(d) database
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory