South Turtle Lake

On the LakeGrade scale South Turtle Lake grades a B, with clarity at 14.1 ft and 20 µg/L of phosphorus placing it above the Minnesota median. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

Mesotrophic conditions dominate at South Turtle Lake: enough nutrients for a healthy fishery, not so much that algal blooms become a chronic problem. South Turtle Lake reaches 35 ft at its deepest point — typical for Minnesota mid-sized lakes, with seasonal stratification but limited cold-water refuge. At 837 acres, South Turtle Lake fits the Minnesota median for monitored lakes, with 11.0 miles of shoreline. Within Otter Tail County's 97 graded lakes, South Turtle Lake ranks 57 — below the local median, though not at the bottom.

South Turtle Lake has no invasive species recorded in Minnesota state databases as of 2024, though prevention practices still apply at all access points. The fishery includes walleye alongside the lake's other 13 documented species — a notable draw for Minnesota anglers. Public access is available — the lake is on the Minnesota PCA public-access list. The lake has a partial ice record — 9 observed ice-outs, centered near Apr 20. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.