Marion Lake

On the scoring rubric Marion Lake grades a D: clarity readings still being added and 71 µg/L of phosphorus keep it in the lower bracket for McLeod County.

A TSI in the eutrophic range signals a lake doing what nutrient-loaded waters do — supporting an active algal community at the cost of clear water. A maximum depth of 15 ft puts Marion Lake in the middle of Minnesota's depth distribution. At 520 acres, Marion Lake fits the Minnesota median for monitored lakes, with 6.7 miles of shoreline. Marion Lake ranks 1 of 5 in McLeod County, putting it in the upper tier of locally monitored lakes.

Marion Lake has no invasive species recorded in Minnesota state databases as of 2021, though prevention practices still apply at all access points. The fishery includes walleye among the lake's 13 documented species — a notable draw for Minnesota anglers. 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.