Portage Lake

On the LakeGrade scale Portage Lake grades a B, with clarity at 13.3 ft and phosphorus readings still being added placing it above the Minnesota median.

Trophically, Portage Lake reads as oligotrophic — nutrient-poor, clear, and ecologically more sensitive to disturbance than richer lakes. A maximum depth of 45 ft puts Portage Lake in the middle of Minnesota's depth distribution. Portage Lake is small — 64 acres alongside 2.0 miles of shoreline — which makes it sensitive to even modest changes in watershed runoff or recreational pressure. Among the 142 graded lakes in Lake County, Portage Lake sits at rank 37, above the county median.

Portage Lake has no invasive species recorded in Minnesota state databases as of 2020, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Portage Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. No formal public access is documented at Portage Lake — most use is by shoreline residents and their guests. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.