St Olaf Lake
Waseca County, Minnesota91 acresView mapDirections
Minnesota PCA publishes the water-quality measurements for St Olaf Lake. Here is what has been measured.
- Impaired · Mercury
- 33 ft max depth
- Public access
- Limited data
St Olaf Lake in Waseca County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 5 ft visibility. Maximum depth: 33 ft. Surface area: 91.2 acres.
Minnesota DNR's Standard Survey on June 20, 2022 caught 5.67 northern pike per gill net at St Olaf Lake. DNR survey details →
St Olaf Lake is a 91-acre lake in Waseca County, Minnesota with a maximum depth of 33 feet. Overall water quality is declining over recent sampling years. The lake supports 11 documented fish species including black crappie, bluegill, and common carp. Public access is available.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-16. Methodology: how these readings are compared.
What St Olaf Lake is good for
From access and monitoring records, not editorial picks.
- Fishing11 species recorded
- Ice seasonIce-out around Mar 31
- Deep water33 ft surveyed max depth
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. St Olaf Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether St Olaf 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 St Olaf Lake
These are the measurements Minnesota PCA publishes for St Olaf Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 5 ft. TSI 54.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 5ft | 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. | 54 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about St Olaf Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
St Olaf Lake typically sits around 58°F at the surface in October. Summer average is about 66°F. Usually warmest in Jul (about 68°F) and coldest in Apr (about 47°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (47°F) to its warmest (68°F).
Typical surface water temperature by month, from 708 field readings (2010–2019) via the EPA Water Quality Portal. See the full St Olaf Lake water temperature breakdown →
Minnesota DNR's Standard Survey on June 20, 2022 caught 5.67 northern pike per gill net at St Olaf Lake.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows St Olaf 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
11 surveys on file from MN DNR Fisheries. Most recent: 2022-06-20 (Standard Survey).
11 surveys on file · most recent 2022-06-20 (Standard Survey)
| Species | Catch rate (CPUE) | Size | Avg weight |
|---|---|---|---|
| Bluntnose Minnow | 58.11 | ||
| Bluegill | 55.88 | 3–8 in 2022-06-20 | 0.14 lb |
| Largemouth Bass | 27.78 | 3–20 in 2022-06-20 | 1.18 lb |
| Black Crappie | 14.48 | 5–13 in 2022-06-20 | 0.18 lb |
| Black Bullhead | 10.12 | 9 in 2002-06-17 | 0.58 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
Largemouth Bass
Black Crappie
Black Bullhead
From the 2022-06-20 survey
St Olaf Lake is a 91-acre lake located approximately 3.5 miles east of the town of New Richland in Waseca County. The county-owned public access is located on the north shore off County Highway 8. St Olaf Lake has a maximum depth of 33 feet, with approximately 55% of the lake less than 15 feet. St Olaf Lake is…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for St Olaf Lake. 3 reports on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Fisheries Lake Survey — St. OlafFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — St. OlafFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — St. OlafPublic Water Access Sites · MN DNR LakeFinder
Lake Details
Max depth
33 ft
Surface area
91 acres
Shoreline
1.6 mi
Littoral zone
56%
Share shallower than 15 ft
Public access
Yes
Listed by Minnesota PCA
Lake Size & Watershed
Watershed (drainage) area
0 sq mi
HydroLAKES / HydroSHEDS
Elevation
1,191 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Stays via Stay22
Stays near St Olaf Lake
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Top-rated places to stay near St Olaf Lake
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Fish Species
Click a species to see every lake where it is documented.
Fishing St Olaf Lake
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Ice season
Typical ice-out
Mar 31
Earliest Mar 3, 2024 · Latest Apr 22, 2013
Typical ice-in
Dec 3
Earliest Nov 15, 2014 · Latest Dec 14, 2004
Most recent ice-out
Mar 21
2026
25 observations · Minnesota PCA ice records
Reservoir Info (USACE NID)
St Olaf Lake is a man-made reservoir impounded by the St. Olaf Lake (completed 1940), built primarily for recreation on the Le Sueur River-TR; other-type dam, 7 ft tall and 21 ft long.
- Surface area
- 90 ac
- Normal storage
- 1,245 ac-ft
- Max storage
- 1,494 ac-ft
- Drainage area
- 0.6 sq mi
- Hazard class
- Low
- Owner
- MNDNR
Source: USACE National Inventory of Dams, NID ID MN00109 · Operator website
EPA Impairment Status
St Olaf 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 MN81-0003-00 · Official waterbody report
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of St Olaf Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- New Richland WwtpNew Richland · 4.5 mi away · NPDES MN0021032Recent violation
- Cargill Animal NutritionNew Richland · 4.5 mi away · NPDES MN0071919
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
Nearby Lakes in Waseca County
Frequently asked questions about St Olaf Lake
Where is St Olaf Lake?
- St Olaf Lake is a lake in Waseca County, Minnesota. Its water-quality measurements are published by Minnesota PCA and shown on this page as reported.
What is the water quality of St Olaf Lake?
- St Olaf Lake in Waseca County, Minnesota has water-quality measurements published by Minnesota PCA, shown here as reported. Water clarity: 5 ft visibility. Maximum depth: 33 ft. Surface area: 91.2 acres.
Is St Olaf Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. St Olaf 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 St Olaf Lake?
- St Olaf Lake typically sits around 58°F at the surface in October, from 708 EPA Water Quality Portal field readings (2010–2019). That is a typical value for the month, not a live reading.
How deep is St Olaf Lake?
- St Olaf Lake has a maximum depth of 33 feet. The lake covers 91.2 acres.
What fish are in St Olaf Lake?
- Fish species found in St Olaf Lake include black crappie, bluegill, common carp, hybrid sunfish, largemouth bass, northern pike, pumpkinseed, white crappie, white sucker, yellow bullhead, yellow perch. St Olaf Lake is located in Waseca County, Minnesota.
What did the DNR fisheries survey find at St Olaf Lake?
- Minnesota DNR's Standard Survey on June 20, 2022 caught 5.67 northern pike per gill net at St Olaf Lake. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows St Olaf 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 St Olaf Lake thaw?
- St Olaf Lake typically has ice-out around Mar 31. Ice typically forms around Dec 3. The open water season is approximately 247 days.
Can I fish at St Olaf Lake?
- Public access to St Olaf 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 St Olaf Lake across LakeQuality
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Where this data comes from
98 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
MNPCA98 samples · 2020–2025
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
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Ice data from Minnesota DNR Climate