Lower Nemahbin Lake

On the LakeGrade rubric, Lower Nemahbin Lake pulls an A: clarity at 10.9 ft and 11 µg/L of phosphorus put it in the top bracket for Wisconsin. 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.

The lake sits in the mesotrophic zone — the band where most well-managed Wisconsin lakes fall. A maximum depth of 36 ft puts Lower Nemahbin Lake in the middle of Wisconsin's depth distribution. The lake's 239 acres and partial shoreline records put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. Among the 45 graded lakes in Waukesha County, Lower Nemahbin Lake sits at rank 16, above the county median.

Zebra mussels have been documented at Lower Nemahbin Lake, which alters the filter-feeding balance and can paradoxically increase water clarity while disrupting the food web. Walleye are documented at Lower Nemahbin Lake, one of 5 fish species on record for the lake. A documented public access point at Lower Nemahbin 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.