Markham Lake

Markham Lake grades an F: water clarity, phosphorus, and chlorophyll-a all rate poorly, placing it among the most stressed lakes monitored in Minnesota. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

A TSI in the eutrophic range signals a lake doing what nutrient-loaded waters do — supporting an active algal community at the cost of clear water. Markham Lake reaches 29 ft at its deepest point — typical for Minnesota mid-sized lakes, with seasonal stratification but limited cold-water refuge. At 229 acres, Markham Lake fits the Minnesota median for monitored lakes, with 3.7 miles of shoreline. Markham Lake ranks 186 of 187 in St. Louis County — at the lower end of the locally monitored distribution.

Markham Lake has no invasive species recorded in Minnesota state databases as of 2023, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Markham Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. The lake lacks a documented public access point, so visitor use is limited. 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.