North Turtle Lake

North Turtle Lake earns a D — measurements through 2024 show persistent nutrient pressure that limits clarity through the summer. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

At a TSI of 61, North Turtle Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. A maximum depth of 19 ft puts North Turtle Lake in the middle of Minnesota's depth distribution. With 1,773 acres of surface and 22.9 miles of shoreline, North Turtle Lake is a large water by Minnesota standards — recreational pressure is spread across a long shoreline. Within the 97 graded lakes of Otter Tail County, North Turtle Lake sits at rank 93, near the bottom of the county list.

No invasive species are currently listed at North Turtle Lake — the lake remains off the Minnesota infested-waters roster. Walleye are documented at North Turtle Lake, one of 12 fish species on record for the lake. Public access is available — the lake is on the Minnesota PCA public-access list. 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.