Portage Bay Lake

On the LakeGrade rubric, Portage Bay Lake pulls an A: clarity at 11.3 ft and phosphorus readings still being added put it in the top bracket for Minnesota. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

The lake sits in the mesotrophic zone — the band where most well-managed Minnesota lakes fall. 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. Portage Bay Lake sits at rank 77 of 133 in Cass County, in the lower half of the local distribution.

Zebra mussel presence at Portage Bay Lake means the lake's clarity numbers carry an asterisk — filtered water is not the same as nutrient-poor water. The state fisheries records do not list documented species for Portage Bay Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. Public access is available — the lake is on the Minnesota PCA public-access list. The lake has a long ice-out record — 71 observations on file, with a median ice-out around Apr 28. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.