Spirit River Flowage Lake

On the scoring rubric Spirit River Flowage Lake grades a D: clarity at 3.0 ft and 49 µg/L of phosphorus keep it in the lower bracket for Lincoln County. Clarity is the limiting factor — phosphorus is reasonable but suspended particles or algal cells keep water transparency below Wisconsin norms.

At a TSI of 61, 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 19 graded lakes of Lincoln County, Spirit River Flowage Lake sits at rank 19, 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.