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LakeQuality
D

Oak Leaf Lake

Nicollet County, MinnesotaEutrophic

Oak Leaf Lake earns a D — measurements through 2024 show persistent nutrient pressure that limits clarity through the summer. The lake's weakest score is on Secchi depth — the water looks more turbid than its phosphorus number alone would predict.

Eutrophic conditions are the baseline here: clarity drops noticeably in late summer, and dissolved oxygen near the bottom can become a concern. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake's surface area is not consistently recorded across state datasets — physical context remains partial. Within the 2 graded lakes of Nicollet County, Oak Leaf Lake sits at rank 2, near the bottom of the county list.

Oak Leaf Lake has no invasive species recorded in Minnesota state databases as of 2024, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Oak Leaf Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. Public access is available — the lake is on the Minnesota PCA public-access list. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.

Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2024-09-25. Grade methodology: LakeGrade methodology.

Swimming Safety

Swimming not recommended, poor water quality with high algae risk

Water Quality Grade: D, Poor

Very murky, less than 3.3 ft of visibility. Phosphorus level: 30 µg/L. Trophic State Index: 57.

MetricValueGrade
Water Clarity (Secchi Depth)3.3 ftF
Phosphorus30 µg/LC
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)57Eutrophic

High nutrients, frequent algae, reduced clarity

Location

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County Ranking

Ranked #2 of 2 lakes in Nicollet County

Nearby Lakes in Nicollet County

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.

Data Sources

Water quality data from the EPA Water Quality Portal

Grading methodology based on Metropolitan Council standards

Most recent sample: 2024-09-25

Monitoring stations: 1