Lake Keesus

Lake Keesus earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Waukesha County. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

A TSI value of 37 puts Lake Keesus in the oligotrophic range, where biological productivity stays low and the water column remains clear. Lake Keesus reaches 42 ft at its deepest point — typical for Wisconsin mid-sized lakes, with seasonal stratification but limited cold-water refuge. Lake Keesus covers 235 acres alongside partial shoreline records — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Within Waukesha County's 48 graded waters, Lake Keesus sits at rank 7, near the top of the local distribution.

Zebra mussel presence at Lake Keesus 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. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.