Jefferson Lake

Jefferson Lake earns an F: 90 µg/L of phosphorus and clarity at 2.0 ft signal heavy nutrient loading from the surrounding watershed. clarity and phosphorus rate similarly, so there is no obvious single lever to pull on watershed management.

At a TSI of 68, Jefferson Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake's 700 acres and partial shoreline records put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. Within the 14 graded lakes of Le Sueur County, Jefferson Lake sits at rank 12, near the bottom of the county list.

No invasive species are currently listed at Jefferson Lake — the lake remains off the Minnesota infested-waters roster. The state fisheries records do not list documented species for Jefferson Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. A documented public access point at Jefferson Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.