Boulder Lake
Boulder Lake in Hubbard County, Minnesota has a water quality grade of A (Excellent). 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.
- Clarity
- 10.8 ft
- Typical in August
- 77°F
- Max depth
- 28 ft
- Area
- 341 acres
- Type
- Mesotrophic
- Trend
- ↑ Improving
- Public access
- Yes
Next lake in Hubbard County
Boulder Lake is a 341-acre mesotrophic lake in Hubbard County, Minnesota with a maximum depth of 28 feet. Water quality is graded A based on 2 sampling years through 2025. 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. Grade methodology: LakeGrade methodology.
Watch Boulder Lake water quality
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
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.
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A (Excellent)
Good clarity, visible to about 10.8 ft. Phosphorus level: 16 µg/L. Chlorophyll-a: 6.2 µg/L. Trophic State Index: 45.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 10.8 ft | Not graded |
| Phosphorus | 16 µg/L | Good |
| Chlorophyll-a (Algae) | 6.2 µg/L | Good |
| Trophic State Index (TSI) | 45 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay 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
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 Minnesota’s top lakes →
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.
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 →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 28 ft |
| Surface Area | 341 acres |
| Shoreline Length | 4.9 mi |
| Littoral Zone | 53% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Boulder LakePublic
Fish Species
Click a species to see every graded 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.
DNR Fisheries Survey Summary
12 surveys on file from MN DNR Fisheries. Most recent: 2023-08-21 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluntnose Minnow | 19.11 | — |
| Largemouth Bass | 17.48 | 0.78 lb |
| JND | 16.38 | — |
| Yellow Perch | 12.56 | 0.15 lb |
| Smallmouth Bass | 8.26 | 0.71 lb |
| Bluegill | 6.36 | 0.18 lb |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
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
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.174 m/yr | 6 |
| Phosphorus | ↑ Improving | -1.49 µg/L/yr | 6 |
| Chlorophyll-a | ↑ Improving | -0.8 µg/L/yr | 6 |
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
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN29-0162-00 · Official waterbody report
County Ranking
Ranked #44 of 68 lakes in Hubbard County
Nearby Lakes in Hubbard County
Frequently asked questions about Boulder Lake
What is the water quality grade for Boulder Lake?
- Boulder Lake in Hubbard County, Minnesota has a water quality grade of A (Excellent). 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?
- Excellent for swimming, crystal clear water with minimal algae. Boulder Lake has a water quality grade of A (Excellent). Algae concentration (chlorophyll-a) is 6.2 µg/L. Always check local health department advisories before swimming.
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.
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.
Explore Boulder Lake across LakeGrade
Depth, room, public access, and the state wake-sport rules
Fish species and top-graded 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 grade
Lakes in the Mississippi Headwaters, ranked by water quality
Moderate nutrients, good water quality
Minnesota's cleanest and most-polluted lakes, ranked
More Minnesota Lake Rankings
State Parks Near Boulder Lake
Other Grade A 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)
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
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