Portage Lake

Portage Lake carries a solid B grade — strong on most parameters, with measurements that hold up well across the summer season. Clarity is the limiting factor — phosphorus is reasonable but suspended particles or algal cells keep water transparency below Minnesota norms.

The lake sits in the mesotrophic zone — the band where most well-managed Minnesota lakes fall. The lake's 55 ft maximum depth is in the upper tier for Minnesota — deep enough for cold-water fish to find refuge in summer. At 128 acres, Portage Lake fits the Minnesota median for monitored lakes, with 6.3 miles of shoreline. Among the 128 graded lakes in Cook County, Portage Lake sits at rank 40, above the county median.

No invasive species are currently listed at Portage Lake — the lake remains off the Minnesota infested-waters roster. 3 fish species are on record, with panfish making up the recreational core. 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.