Big Round Lake

The LakeGrade rubric puts Big Round Lake at a C: clarity at 5.0 ft, 27 µg/L of phosphorus, and a TSI of 55 signal an intermediate trophic state. Clarity is the limiting factor — phosphorus is reasonable but suspended particles or algal cells keep water transparency below Wisconsin norms.

At a TSI of 55, Big Round Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. Big Round Lake reaches 17 ft at its deepest point — typical for Wisconsin mid-sized lakes, with seasonal stratification but limited cold-water refuge. With 1,014 acres of surface and partial shoreline records, Big Round Lake is a large water by Wisconsin standards — recreational pressure is spread across a long shoreline. Within Polk County's 74 graded lakes, Big Round Lake ranks 48 — below the local median, though not at the bottom.

Big Round Lake has at least one documented invasive species (Banded Mystery Snail), so boaters and anglers should observe clean-drain-dry steps when leaving the lake. Walleye are documented at Big Round Lake, one of 5 fish species on record for the lake. A documented public access point at Big Round Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. Multiple sampling years from the Wisconsin DNR Citizen Lake Monitoring Network back the grade, so the letter should hold steady absent a major watershed shift.