Cosgrove Lake

Cosgrove Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Florence County. 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 value of 28 puts Cosgrove Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake's surface area is not consistently recorded across state datasets — physical context remains partial. Within Florence County's 39 graded lakes, Cosgrove Lake ranks 27 — below the local median, though not at the bottom.

No invasive species are currently listed at Cosgrove Lake — the lake remains off the Wisconsin infested-waters roster. The state fisheries records do not list documented species for Cosgrove 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.