Oslo Lake

Oslo Lake earns a C — middle-of-the-pack water quality, with one or two parameters dragging the average down from a stronger grade. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

The lake sits in the mesotrophic zone — the band where most well-managed Minnesota lakes fall. A maximum depth of 36 ft puts Oslo Lake in the middle of Minnesota's depth distribution. Oslo Lake is small — 99 acres alongside 3.7 miles of shoreline — which makes it sensitive to even modest changes in watershed runoff or recreational pressure. Among the 187 graded lakes in St. Louis County, Oslo Lake sits at rank 87, above the county median.

No invasive species are currently listed at Oslo Lake — the lake remains off the Minnesota infested-waters roster. 2 fish species are documented at Oslo Lake, a mixed warm-water community typical for Minnesota lakes of this size. The lake lacks a documented public access point, so visitor use is limited. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.