Rat Lake

Rat Lake earns a D — measurements through 2024 show persistent nutrient pressure that limits clarity through the summer. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

At a TSI of 54, Rat Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. Rat Lake reaches 21 ft at its deepest point — typical for Minnesota mid-sized lakes, with seasonal stratification but limited cold-water refuge. The lake's 431 acres and 4.7 miles of shoreline put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. Within the 53 graded lakes of Aitkin County, Rat Lake sits at rank 46, near the bottom of the county list.

No invasive species are currently listed at Rat Lake — the lake remains off the Minnesota infested-waters roster. Walleye are documented at Rat Lake, one of 13 fish species on record for the lake. No formal public access is documented at Rat Lake — most use is by shoreline residents and their guests. The lake has a partial ice record — 5 observed ice-outs, centered near Apr 12. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.