Spirit River Flowage Lake

The LakeGrade rubric puts Spirit River Flowage Lake at a C: clarity at 6.6 ft, 49 µg/L of phosphorus, and a TSI of 55 signal an intermediate trophic state. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

At a TSI of 55, Spirit River Flowage Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. Spirit River Flowage Lake reaches 25 ft at its deepest point — typical for Wisconsin mid-sized lakes, with seasonal stratification but limited cold-water refuge. At 1,220 acres, Spirit River Flowage Lake is one of the larger lakes in Lincoln County, with partial shoreline records supporting multiple distinct use patterns. Within the 21 graded lakes of Lincoln County, Spirit River Flowage Lake sits at rank 20, near the bottom of the county list.

An invasive species record — Purple Loosestrife — has been logged at Spirit River Flowage Lake; Wisconsin DNR maintains the official infested-waters list. Walleye are documented at Spirit River Flowage Lake, one of 6 fish species on record for the lake. Public access is available — the lake is on the Wisconsin DNR public-access list. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.