Mazaska Lake
Rice County, Minnesota688 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for Mazaska Lake. Here is what has been measured.
- Eutrophic
- Impaired · Mercury
- Eurasian watermilfoil
- 50 ft max depth
- Public access
- Limited data
Mazaska Lake in Rice County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. 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.
Minnesota DNR's Standard Survey on July 21, 2025 caught 4.25 walleye per gill net at Mazaska Lake. DNR survey details →
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). 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. Methodology: how these readings are compared.
Mazaska Lake covers about 690 acres in Rice County. It has 2 public boat landings, so a lakefront rental is not the only way to get a boat on the water. The median ice-out date is April 6, which is when the open-water season begins. For a place on the water, look through cabin and lake-house rentals near Mazaska Lake on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.
What Mazaska Lake is good for
From access and monitoring records, not editorial picks.
- Boat launch2 documented ramps
- Fishing17 species recorded
- Ice seasonIce-out around Apr 6
- Deep water50 ft surveyed max depth
Swimming conditions
Readings onlyRecreation use not supported
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. Mazaska Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Mazaska 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 Mazaska Lake
These are the measurements Minnesota PCA publishes for Mazaska Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 2.5 ft of visibility. Phosphorus 89 µg/L. Chlorophyll-a 51.3 µg/L. TSI 67.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 89µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 51.3µg/L | Poor GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 67 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Mazaska Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Mazaska Lake typically sits around 71°F at the surface in September. 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.
Column height runs from this lake’s coldest month (54°F) to its warmest (72°F).
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 →
Minnesota DNR's Standard Survey on July 21, 2025 caught 4.25 walleye per gill net at Mazaska Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Mazaska Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
DNR Fisheries Survey Summary
18 surveys on file from MN DNR Fisheries. Most recent: 2025-07-21 (Standard Survey).
18 surveys on file · most recent 2025-07-21 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluegill | 8194.43 | 3–10 in 2025-07-21 | 0.21 lb |
| Black Crappie | 15.11 | 4–12 in 2025-07-21 | 0.26 lb |
| Largemouth Bass | 11.70 | 3–18 in 2025-07-21 | 1.38 lb |
| White Crappie | 9.25 | 3–14 in 2025-07-21 | 0.29 lb |
| Yellow Perch | 8.30 | 6–7 in 2025-07-21 | 0.12 lb |
| Freshwater Drum | 7.10 | 9–22 in 2025-07-21 | 1.45 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.
Bluegill
Black Crappie
Largemouth Bass
White Crappie
From the 2025-07-21 survey
Lake Mazaska is a 672-acre lake located northeast of Shieldsville in Rice County. There is a county-owned access located off Lake Mazaska Trail on the southwest shore and a state-owned access located off Highway 21 on the southeast shore. Lake Mazaska has a maximum depth of 50 feet, with approximately 50% of the lake…
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
Lake Details
Max depth
50 ft
Average depth
13 ft
Surface area
688 acres
Shoreline
4.9 mi
Littoral zone
49%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
5 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,063 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Mazaska Lake (Southwest)Public
- Mazaska Lake (Southeast)Public
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays 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 readings cover nutrients and algae, not lodging. Cabins and rentals around Mazaska Lake are listed below.
Top-rated places to stay near Mazaska Lake
Prices for Oct 9–11, 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 Minnesota’s top lakes →
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Fish Species
Click a species to see every 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.
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Ice season
Typical ice-out
Apr 6
Earliest Mar 2, 2024 · Latest Apr 30, 2018
Typical ice-in
Dec 1
Earliest Nov 25, 1992 · Latest Dec 7, 2017
Most recent ice-out
Mar 26
2026
27 observations · Minnesota PCA ice records
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
Designated uses not supporting: Fish consumption, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN66-0039-00 · Official waterbody report
Nearby Lakes in Rice County
Frequently asked questions about Mazaska Lake
Where is Mazaska Lake?
- Mazaska Lake is a lake in Rice County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of Mazaska Lake?
- Mazaska Lake in Rice County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. 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?
- Nutrient and algae readings are not a swimming clearance. Mazaska Lake is listed impaired under Clean Water Act §303(d) (IR 5) for mercury, nutrients (phosphorus, nitrogen). Check local advisories before you swim.
What is the water temperature of Mazaska Lake?
- Mazaska Lake typically sits around 71°F at the surface in September, 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.
What did the DNR fisheries survey find at Mazaska Lake?
- Minnesota DNR's Standard Survey on July 21, 2025 caught 4.25 walleye per gill net at Mazaska Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Mazaska Lake’s water-quality measurements separately, and the water-quality trend over 6 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
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.
Can I fish at Mazaska Lake?
- Mazaska Lake has 2 documented boat landings 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 Mazaska 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 Rice 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
More lakes in Minnesota
State Parks Near Mazaska Lake
Other Lakes in Minnesota
Eutrophic Lakes in Minnesota
Compare Mazaska Lake With Nearby Lakes
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)
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
Ice data from Minnesota DNR Climate