Lower Nashotah Lake

Lower Nashotah Lake sits at the top of the Wisconsin DNR grading rubric with an A, a mark reached by the cleanest lakes in Wisconsin. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

A TSI value of 34 puts Lower Nashotah Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. Lower Nashotah Lake reaches 43 ft at its deepest point — typical for Wisconsin mid-sized lakes, with seasonal stratification but limited cold-water refuge. The lake is compact at 93 acres, with partial shoreline records and little volume to buffer nutrient inputs. Lower Nashotah Lake ranks 11 of 48 in Waukesha County, putting it in the upper tier of locally monitored lakes.

Lower Nashotah Lake is on the Wisconsin infested-waters list for zebra mussels — boaters should follow clean-drain-dry protocols when moving gear to or from the lake. The fishery includes walleye alongside the lake's other 6 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.