Mountain Lake
Minnesota1,344 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Mountain Lake. Here is what has been measured.
- 130 ft max depth
- Public access
- Limited data
Mountain Lake in Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 19 ft visibility. Maximum depth: 130 ft. Surface area: 1344.33 acres.
Minnesota DNR's Standard Survey on August 3, 2020 caught 1.50 smallmouth bass per gill net at Mountain Lake. Length samples in the latest survey that recorded them ran 7–18 inches. DNR survey details →
Mountain Lake is a 1,344-acre lake in Unknown County, Minnesota with a maximum depth of 130 feet (42-foot average). Overall water quality is declining over recent sampling years. The lake supports 7 documented fish species including burbot, cisco species, and green sunfish. Public access is available.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-07-31. Methodology: how these readings are compared.
What Mountain Lake is good for
From access and monitoring records, not editorial picks.
- Clear water19 ft of visibility
- Fishing7 species recorded
- Ice seasonIce-out around May 5
- Deep water130 ft surveyed max depth
- Big water1,344 acres
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Mountain 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 Mountain Lake
These are the measurements Minnesota PCA publishes for Mountain Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Crystal clear, you can see 19 ft down. TSI 35.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 19ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | No reading The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. | |
| 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. | 35 | Oligotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Low nutrients, clear water. No reading is a swimming clearance.
Ask about Mountain Lake
Answers come straight from the public measurements and survey records on this page.
Minnesota DNR's Standard Survey on August 3, 2020 caught 1.50 smallmouth bass per gill net at Mountain Lake. Length samples in the latest survey that recorded them ran 7–18 inches.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Mountain Lake’s water-quality measurements separately, and the water-quality trend over 5 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
15 surveys on file from MN DNR Fisheries. Most recent: 2025-08-11 (Targeted Survey).
15 surveys on file · most recent 2025-08-11 (Targeted Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Tullibee (Cisco) | 9.17 | 8–20 in 2005-07-18 | 0.69 lb |
| Yellow Perch | 2.78 | 6–11 in 2020-08-03 | 0.24 lb |
| Smallmouth Bass | 2.61 | 7–18 in 2020-08-03 | 0.6 lb |
| Lake Trout | 2.54 | 8–39 in 2020-08-03 | 1.74 lb |
| White Sucker | 1.62 | 11–22 in 2020-08-03 | 2.05 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.
Tullibee (Cisco)
Yellow Perch
Smallmouth Bass
Lake Trout
From the 2025-08-11 survey
Temperature and dissolved oxygen measurements were collected from the deepest basin in Clearwater Lake on August 11th, 2025. This was done to evaluate the quantity and quality of cold, oxygenated water (i.e., oxythermal habitat) available to Lake Trout, the most sensitive coldwater species present in this lake (Cisco,…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Mountain Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — ClearwaterFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Clearwater (1828)Aquatic Plant Report · MN DNR LakeFinder
- —Public Water Access Sites — ClearwaterPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
130 ft
Average depth
42 ft
Surface area
1,344 acres
Shoreline
18.5 mi
Littoral zone
19%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
16 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,647 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Stays via Stay22
Stays near Mountain Lake
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Top-rated places to stay near Mountain Lake
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Follow Mountain Lake’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing Mountain Lake
Water Quality Trend: Worsening
Based on 5 years of monitoring (2020–2025).
Water clarity
Worsening5 years
Ice season
Typical ice-out
May 5
Earliest Apr 3, 2012 · Latest May 20, 2014
Typical ice-in
Dec 8
Earliest Nov 20, 2018 · Latest Dec 26, 2015
Most recent ice-out
Apr 26
2024
51 observations · Minnesota PCA ice records
Nearby Lakes in Minnesota
Frequently asked questions about Mountain Lake
Where is Mountain Lake?
- Mountain Lake is a lake in Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Mountain Lake?
- Mountain Lake in Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 19 ft visibility. Maximum depth: 130 ft. Surface area: 1344.33 acres.
Is Mountain Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
How deep is Mountain Lake?
- Mountain Lake has a maximum depth of 130 feet and an average depth of 42 feet. The lake covers 1344.33 acres.
What fish are in Mountain Lake?
- Fish species found in Mountain Lake include burbot, cisco species, green sunfish, lake trout, smallmouth bass, white sucker, yellow perch. Mountain Lake is located in Minnesota.
What did the DNR fisheries survey find at Mountain Lake?
- Minnesota DNR's Standard Survey on August 3, 2020 caught 1.50 smallmouth bass per gill net at Mountain Lake. Length samples in the latest survey that recorded them ran 7–18 inches. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Mountain Lake’s water-quality measurements separately, and the water-quality trend over 5 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
When does Mountain Lake thaw?
- Mountain Lake typically has ice-out around May 5. Ice typically forms around Dec 8. The open water season is approximately 217 days.
Can I fish at Mountain Lake?
- Public access to Mountain Lake is listed as yes on the lake record. 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 Mountain 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 Unknown County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its readings
Minnesota's cleanest lakes, ranked on agency measurements
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State Parks Near Mountain Lake
Other Lakes in Minnesota
Oligotrophic Lakes in Minnesota
Where this data comes from
1 measurement from 1 monitoring station, 2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA1 sample · 2024
Analytical methods
- Field measurement/observation, generic method
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)
Lake details from Minnesota DNR LakeFinder
Ice data from Minnesota DNR Climate