South Turtle Lake

On the LakeGrade rubric, South Turtle Lake pulls an A: clarity at 26.2 ft and 17 µg/L of phosphorus put it in the top bracket for Wisconsin. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

A TSI value of 38 puts South Turtle Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. A maximum depth of 40 ft puts South Turtle Lake in the middle of Wisconsin's depth distribution. The lake's 466 acres and partial shoreline records put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. Among the 202 graded lakes in Vilas County, South Turtle Lake sits at rank 70, above the county median.

An invasive species record — Banded Mystery Snail — has been logged at South Turtle Lake; Wisconsin DNR maintains the official infested-waters list. Walleye are documented at South Turtle Lake, one of 6 fish species on record for the lake. Public access is available — the lake is on the Wisconsin DNR 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.