Zumbro Lake

Zumbro Lake pulls a D on the LakeGrade rubric — phosphorus loading and limited clarity hold it below the Minnesota average. Sub-grades cluster within a single letter of each other, which usually means the lake is in stable trophic balance rather than fighting one specific stressor.

Eutrophic conditions are the baseline here: clarity drops noticeably in late summer, and dissolved oxygen near the bottom can become a concern. A maximum depth of 43 ft puts Zumbro Lake in the middle of Minnesota's depth distribution. The lake's 715 acres and 22.8 miles of shoreline put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. Among the 5 graded lakes in Olmsted County, Zumbro Lake sits at rank 2, above the county median.

Zebra mussel presence at Zumbro Lake means the lake's clarity numbers carry an asterisk — filtered water is not the same as nutrient-poor water. Muskie are on the species list at Zumbro Lake, alongside the lake's 24 other documented fish. Public access is available — the lake is on the Minnesota PCA public-access list. Ice-out has been logged at Zumbro Lake more than two dozen times, putting the median around Mar 31 — a useful baseline for tracking climate trends. 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.