Ottawa Lake

Ottawa Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Waukesha County. Sub-grades cluster within a single letter of each other, which usually means the lake is in stable trophic balance rather than fighting one specific stressor.

A TSI value of 33 puts Ottawa Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake is compact at 17 acres, with partial shoreline records and little volume to buffer nutrient inputs. Among the 48 graded lakes in Waukesha County, Ottawa Lake ranks 12 — in the top quartile locally.

An invasive species record — Curly-Leaf Pondweed — has been logged at Ottawa Lake; Wisconsin DNR maintains the official infested-waters list. Walleye are documented at Ottawa Lake, one of 4 fish species on record for the lake. A documented public access point at Ottawa Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. 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.