Avoca Lake

On the scoring rubric Avoca Lake grades a D: clarity at 2.0 ft and 81 µg/L of phosphorus keep it in the lower bracket for Iowa County. The two scored sub-grades — clarity and phosphorus — track close together, so neither one is dragging the average down.

A TSI in the eutrophic range signals a lake doing what nutrient-loaded waters do — supporting an active algal community at the cost of clear water. Avoca Lake is a shallow lake at 10 ft maximum depth, which means it warms quickly, mixes constantly, and amplifies nutrient inputs. Avoca Lake is small — 63 acres alongside partial shoreline records — which makes it sensitive to even modest changes in watershed runoff or recreational pressure. Within the 6 graded lakes of Iowa County, Avoca Lake sits at rank 5, near the bottom of the county list.

Zebra mussel presence at Avoca Lake means the lake's clarity numbers carry an asterisk — filtered water is not the same as nutrient-poor water. The fishery includes walleye among the lake's 4 documented species — a notable draw for Wisconsin anglers. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.