Zumwalde Lake

Zumwalde 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.

At a TSI of 65, Zumwalde Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. A maximum depth of 23 ft puts Zumwalde Lake in the middle of Minnesota's depth distribution. At 128 acres, Zumwalde Lake fits the Minnesota median for monitored lakes, with 4.6 miles of shoreline. Zumwalde Lake ranks 50 of 55 in Stearns County — at the lower end of the locally monitored distribution.

Zebra mussels have been documented at Zumwalde Lake, which alters the filter-feeding balance and can paradoxically increase water clarity while disrupting the food web. Walleye are documented at Zumwalde Lake, one of 18 fish species on record for the lake. The lake lacks a documented public access point, so visitor use is limited. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.