Flat Lake

On the LakeGrade rubric, Flat Lake pulls an A: clarity at 11.2 ft and 13 µg/L of phosphorus put it in the top bracket for Minnesota. 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.

A TSI near 42 places Flat Lake in the mesotrophic band — moderate productivity, with seasonal swings between clearer spring water and richer late-summer conditions. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. With 1,754 acres of surface and partial shoreline records, Flat Lake is a large water by Minnesota standards — recreational pressure is spread across a long shoreline. Among the 102 graded lakes in Becker County, Flat Lake sits at rank 36, above the county median.

No invasive species are currently listed at Flat Lake — the lake remains off the Minnesota infested-waters roster. The state fisheries records do not list documented species for Flat Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. No formal public access is documented at Flat Lake — most use is by shoreline residents and their guests. 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.