Lake Kegonsa

Lake Kegonsa earns a C — middle-of-the-pack water quality, with one or two parameters dragging the average down from a stronger grade. With clarity and phosphorus scored, the sub-grades cluster within a letter of each other, pointing to stable conditions rather than one specific stressor.

At a TSI of 61, Lake Kegonsa reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. A maximum depth of 32 ft puts Lake Kegonsa in the middle of Wisconsin's depth distribution. Lake Kegonsa covers 3,200 acres alongside partial shoreline records, large enough that conditions can vary meaningfully between bays. Among the 21 graded lakes in Dane County, Lake Kegonsa ranks 3 — in the top quartile locally.

Zebra mussels have been documented at Lake Kegonsa, which alters the filter-feeding balance and can paradoxically increase water clarity while disrupting the food web. The fishery includes walleye among the lake's 7 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.