Mazaska Lake
Mazaska Lake in Rice County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 2.5 ft visibility. Phosphorus: 89 µg/L. Chlorophyll-a (algae): 51.3 µg/L. Maximum depth: 50 ft. Surface area: 687.68 acres.
- Clarity
- 2.5 ft
- Typical in August
- 72°F
- Max depth
- 50 ft
- Area
- 688 acres
- Type
- Eutrophic
- Trend
- ↓ Declining
- Public access
- Yes
- Ice-out
- Apr 6
- Open water
- 239 days
Grade F measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Mazaska Lake →
Next lake in Rice County
Mazaska Lake is a 688-acre productive, nutrient-rich eutrophic lake in Rice County, Minnesota with a maximum depth of 50 feet (13-foot average). Water quality is graded F based on 2 sampling years through 2025. Overall water quality is declining over recent sampling years. The lake supports 17 documented fish species including black bullhead, black crappie, and bluegill. Public access is available with 2 public boat landings. Compared to the 13 other monitored lakes in Rice County, Mazaska Lake ranks #8 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-10-02. Grade methodology: LakeGrade methodology.
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Swimming Safety
Grade onlyLimited data
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.
Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom
Water Quality Grade: F (Algae-prone)
Very murky, less than 2.5 ft of visibility. Phosphorus level: 89 µg/L. Chlorophyll-a: 51.3 µg/L. Trophic State Index: 67.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.5 ft | Not graded |
| Phosphorus | 89 µg/L | Poor |
| Chlorophyll-a (Algae) | 51.3 µg/L | Poor |
| Trophic State Index (TSI) | 67 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Mazaska Lake
Compare lakeside cabins, hotels, and vacation rentals near Mazaska Lake in Rice 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. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Mazaska Lake are listed below.
Top-rated places to stay near Mazaska Lake
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Planning a whole trip? See where to stay at Minnesota’s top lakes →
Water Temperature
Mazaska Lake typically sits around 72°F at the surface in August. Summer average is about 69°F. Usually warmest in Aug (about 72°F) and coldest in May (about 54°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 99 field readings (2022–2025) via the EPA Water Quality Portal. See the full Mazaska Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 50 ft |
| Average Depth | 13 ft |
| Surface Area | 688 acres |
| Shoreline Length | 4.9 mi |
| Littoral Zone | 49% |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Mazaska Lake (Southwest)Public
- Mazaska Lake (Southeast)Public
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Mazaska 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
17 surveys on file from MN DNR Fisheries. Most recent: 2023-09-12 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluegill | 8722.68 | 0.21 lb |
| Black Crappie | 16.05 | 0.26 lb |
| Largemouth Bass | 10.91 | 1.29 lb |
| White Crappie | 10.03 | 0.28 lb |
| Yellow Perch | 8.91 | 0.12 lb |
| Freshwater Drum | 7.01 | 1.38 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.
Bluegill
Black Crappie
Largemouth Bass
White Crappie
From the 2023-09-12 survey
Minnesota DNR Fisheries IBI program staff delineated the floating leaf and emergent aquatic vegetation of Mazaska lake 09/12/2023, following the protocols listed in the MN DNR Lake Plant Mapping Manual. There were a total of 46.7 acres of floating and emergent plants mapped. This consisted of 1.9 acres of emergent…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Mazaska Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — MazaskaFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — MazaskaFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — MazaskaPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.031 m/yr | 6 |
Ice Season
Historical ice data from Minnesota DNR (27 observations).
Estimated open water season: 239 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2024-03-02 (2024) | 2018-04-30 (2018) |
| Ice-In | 1992-11-25 (1992) | 2017-12-07 (2017) |
Most recent ice-out: 2026-03-26
EPA Impairment Status
Mazaska Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN66-0039-00 · Official waterbody report
County Ranking
Ranked #8 of 14 lakes in Rice County
Nearby Lakes With Higher Grades
Mazaska Lake holds Grade F. 2 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
Nearby Lakes in Rice County
Frequently asked questions about Mazaska Lake
What is the water quality grade for Mazaska Lake?
- Mazaska Lake in Rice County, Minnesota has a water quality grade of F (Algae-prone). Water clarity: 2.5 ft visibility. Phosphorus: 89 µg/L. Chlorophyll-a (algae): 51.3 µg/L. Maximum depth: 50 ft. Surface area: 687.68 acres.
Is Mazaska Lake safe to swim in?
- Algae and nutrients are often high — check current advisories before swimming. Skip the water if you see scum or a paint-like bloom. Mazaska Lake has a water quality grade of F (Algae-prone). Algae concentration (chlorophyll-a) is 51.3 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Mazaska Lake?
- Mazaska Lake typically sits around 72°F at the surface in August, from 99 EPA Water Quality Portal field readings (2022–2025). That is a typical value for the month, not a live reading.
How deep is Mazaska Lake?
- Mazaska Lake has a maximum depth of 50 feet and an average depth of 13 feet. The lake covers 687.68 acres.
What fish are in Mazaska Lake?
- Fish species found in Mazaska Lake include black bullhead, black crappie, bluegill, bowfin (dogfish), brown bullhead, common carp, freshwater drum, largemouth bass, longnose gar, northern pike, pumpkinseed, walleye, white bass, white crappie, white sucker, yellow bullhead, yellow perch. Mazaska Lake is located in Rice County, Minnesota.
When does Mazaska Lake thaw?
- Mazaska Lake typically has ice-out around Apr 6. Ice typically forms around Dec 1. The open water season is approximately 239 days.
Are there boat ramps on Mazaska Lake?
- Mazaska Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Mazaska Lake (Southwest), Mazaska Lake (Southeast). Public access is listed as yes.
Explore Mazaska 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 Rice County
Species activity outlook by water temperature and season
Where to stay at Minnesota's top lakes, each with its grade
High nutrients, frequent algae, reduced clarity
Minnesota's cleanest and most-polluted lakes, ranked
More Minnesota Lake Rankings
State Parks Near Mazaska Lake
Other Grade F Lakes in Minnesota
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Where this data comes from
81 measurements from 2 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA81 samples · 2020–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (2)
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
Ice data from Minnesota DNR Climate