St. Olaf Lake
Waseca County, MinnesotaLimited DataEutrophic
On the scoring rubric St. Olaf Lake grades a D: clarity at 5.0 ft and phosphorus readings still being added keep it in the lower bracket for Waseca County.
Eutrophic conditions are the baseline here: clarity drops noticeably in late summer, and dissolved oxygen near the bottom can become a concern. St. Olaf Lake reaches 33 ft at its deepest point — typical for Minnesota mid-sized lakes, with seasonal stratification but limited cold-water refuge. At 91 acres, St. Olaf Lake sits below the Minnesota median: a small water where shoreline activity has an outsized effect on water quality. St. Olaf Lake ranks 2 of 6 in Waseca County — solidly in the upper half of the local distribution.
No invasive species are currently listed at St. Olaf Lake — the lake remains off the Minnesota infested-waters roster. The fishery is bass-led, with 11 documented species across the lake's records. Public access is available — the lake is on the Minnesota PCA public-access list. The lake has a partial ice record — 15 observed ice-outs, centered near Mar 31. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-09-05. Grade methodology: LakeGrade methodology.
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Swimming Safety
Swimming not recommended, poor water quality with high algae risk
Water Quality Grade: D, Poor
Murky, only visible to about 5 ft. Trophic State Index: 54.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5 ft | D |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 54 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 33 ft |
| Surface Area | 91.2 acres |
| Shoreline Length | 1.6 mi |
| Littoral Zone | 56% |
| Public Access | Yes |
Fish Species
Click a species to see all Minnesota and Wisconsin lakes where it is found.
→ Best fishing times for St. Olaf Lake (14-day solunar calendar)
→ Is it safe to eat fish from St. Olaf Lake? (mercury & PFAS guide)
→ St. Olaf Lake fishing regulations (limits, seasons, special rules)
Water Quality Trend: ↑ Improving
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.047 m/yr | 5 |
Ice Season
Historical ice data from Minnesota DNR (25 observations).
Estimated open water season: 247 days
| Earliest | Latest | |
|---|---|---|
| Ice-Out | 2024-03-03 (2024) | 2013-04-22 (2013) |
| Ice-In | 2014-11-15 (2014) | 2004-12-14 (2004) |
Most recent ice-out: 2026-03-21
Location
County Ranking
Ranked #2 of 6 lakes in Waseca County
Cleaner Lakes Within 30 Miles
St. Olaf Lake holds Grade D. One nearby lake has a higher grade.
Nearby Lakes in Waseca County
More Minnesota Lake Rankings
State Parks Near St. Olaf Lake
Other Grade D Lakes in Minnesota
Eutrophic Lakes in Minnesota
DNR Fisheries Survey Summary
11 surveys on file from MN DNR Fisheries. Most recent: 2022-06-20 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluntnose Minnow | 58.11 | — |
| Bluegill | 55.88 | 0.14 lb |
| Largemouth Bass | 27.78 | 1.18 lb |
| Black Crappie | 14.48 | 0.18 lb |
| JND | 11.88 | — |
| Black Bullhead | 10.12 | 0.58 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
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.
- —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
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
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN81-0003-00 · Official waterbody report
Data Sources
Water quality data from the EPA Water Quality Portal
Impairment status from EPA ATTAINS 303(d) database
Grading methodology based on Metropolitan Council standards
Lake details from Minnesota DNR LakeFinder
Ice data from Minnesota DNR Climate
Most recent sample: 2024-09-05
Monitoring stations: 1