Green Lake

Green Lake comes in at a B on the grading rubric — a respectable showing for a Wisconsin lake of its size and depth. 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 48 places Green 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 7,346 acres of surface and partial shoreline records, Green Lake is a large water by Wisconsin standards — recreational pressure is spread across a long shoreline. Within Green Lake County's 13 graded waters, Green Lake sits at rank 3, near the top of the local distribution.

Green Lake has no invasive species recorded in Wisconsin state databases as of 2025, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Green Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.