Mille Lacs Lake

Mille Lacs Lake sits at a C on the grading scale — not impaired, not pristine, with summer measurements that vary year to year. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

A TSI near 45 places Mille Lacs Lake in the mesotrophic band — moderate productivity, with seasonal swings between clearer spring water and richer late-summer conditions. The lake bottoms out at 42 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. With 128,250 acres of surface and 105.5 miles of shoreline, Mille Lacs Lake is a large water by Minnesota standards — recreational pressure is spread across a long shoreline. Within the 11 graded lakes of Mille Lacs County, Mille Lacs Lake sits at rank 10, near the bottom of the county list.

Zebra mussel presence at Mille Lacs Lake means the lake's clarity numbers carry an asterisk — filtered water is not the same as nutrient-poor water. Mille Lacs Lake's fishery is anchored by muskellunge, with 21 documented species in total — a destination water for muskie anglers. Public access is available — the lake is on the Minnesota PCA public-access list. Ice-out has been logged at Mille Lacs Lake more than two dozen times, putting the median around Apr 25 — 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.