Avoca Lake

On the scoring rubric Avoca Lake grades a D: clarity at 6.6 ft and 81 µg/L of phosphorus keep it in the lower bracket for Iowa County. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

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 alongside the lake's other 4 documented species — a notable draw for Wisconsin anglers. Public access is available — the lake is on the Wisconsin DNR public-access list. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.