Oak Leaf Lake
Oak Leaf Lake in Nicollet County, Minnesota has a water quality grade of C (Fair). Water clarity: 3.9 ft visibility. Phosphorus: 30 µg/L. Chlorophyll-a (algae): 4.9 µg/L.
- Clarity
- 3.9 ft
- Typical in August
- 75°F
- Mean depth
- ~7 ft est.
- Type
- Eutrophic
- Trend
- ↑ Improving
- Public access
- Yes
Next lake in Nicollet County
Oak Leaf Lake is a productive, nutrient-rich eutrophic lake in Nicollet County, Minnesota with an estimated average depth of about 7 feet. Water quality is graded C based on 2 sampling years through 2025. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 1 other monitored lakes in Nicollet County, Oak Leaf Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-22. 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.
Generally safe for swimming, moderate water quality
Water Quality Grade: C (Fair)
Murky, only visible to about 3.9 ft. Phosphorus level: 30 µg/L. Chlorophyll-a: 4.9 µg/L. Trophic State Index: 52.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.9 ft | Not graded |
| Phosphorus | 30 µg/L | Fair |
| Chlorophyll-a (Algae) | 4.9 µg/L | Good |
| Trophic State Index (TSI) | 52 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Oak Leaf Lake
Compare lakeside cabins, hotels, and vacation rentals near Oak Leaf Lake in Nicollet 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.
Top-rated places to stay near Oak Leaf Lake
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Water Temperature
Oak Leaf Lake typically sits around 75°F at the surface in August. Summer average is about 71°F. Usually warmest in Aug (about 75°F) and coldest in Sep (about 64°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 13 field readings (2024–2025) via the EPA Water Quality Portal. See the full Oak Leaf Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Average Depth | ~7 ft est. |
| Public Access | Yes |
Depth marked “est.” is a modeled estimate from HydroLAKES, not a measured survey. Minnesota has not published bathymetry for Oak Leaf Lake.
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Recreation & Access
- Oak Leaf LakePublic
Fishing Oak Leaf Lake
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Oak Leaf Lake. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- —Public Water Access Sites — Oak LeafPublic Water Access Sites · MN DNR LakeFinder
Water Quality Trend: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.2 m/yr | 2 |
| Phosphorus | ↓ Declining | +3 µg/L/yr | 2 |
| Chlorophyll-a | ↑ Improving | -3.5 µg/L/yr | 2 |
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Oak Leaf Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Iron Oak Sand Llc - KasotaKasota · 2.8 mi away · NPDES MN0053082Recent violation
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.
County Ranking
Ranked #2 of 2 lakes in Nicollet County
Nearby Lakes With Higher Grades
Oak Leaf Lake holds Grade C. One nearby lake has a higher nutrient-and-algae grade — useful for a swim day, not a reason to skip lodging here.
Nearby Lakes in Nicollet County
Frequently asked questions about Oak Leaf Lake
What is the water quality grade for Oak Leaf Lake?
- Oak Leaf Lake in Nicollet County, Minnesota has a water quality grade of C (Fair). Water clarity: 3.9 ft visibility. Phosphorus: 30 µg/L. Chlorophyll-a (algae): 4.9 µg/L.
Is Oak Leaf Lake safe to swim in?
- Generally safe for swimming, moderate water quality. Oak Leaf Lake has a water quality grade of C (Fair). Algae concentration (chlorophyll-a) is 4.9 µg/L. Always check local health department advisories before swimming.
What is the water temperature of Oak Leaf Lake?
- Oak Leaf Lake typically sits around 75°F at the surface in August, from 13 EPA Water Quality Portal field readings (2024–2025). That is a typical value for the month, not a live reading.
How deep is Oak Leaf Lake?
- No published bathymetric survey covers Oak Leaf Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 7 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Are there boat ramps on Oak Leaf Lake?
- Oak Leaf Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Oak Leaf Lake. Public access is listed as yes.
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Where this data comes from
21 measurements from 1 monitoring station, 2024–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Minnesota Pollution Control Agency - Ambient Surface Water
MNPCA21 samples · 2024–2025
Analytical methods
- Field measurement/observation, generic method
- Phosphorus by Colorimetry
- 10200 H ~ Chlorophyll a-b-c Determination
Monitoring station identifiers (1)
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Lake details from Minnesota DNR LakeFinder
Named boat-access points from the USGS National Boat Ramps inventory