Long Lake

On the scoring rubric Long Lake grades a D: clarity at 2.8 ft and 66 µg/L of phosphorus keep it in the lower bracket for Watonwan 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.

At a TSI of 63, Long Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. At only 13 ft deep, Long Lake is shallow — wind keeps the water column mixed and sediment resuspension drives phosphorus levels harder to manage. At 263 acres, Long Lake fits the Minnesota median for monitored lakes, with 4.7 miles of shoreline. Within Watonwan County's 5 graded lakes, Long Lake ranks 3 — below the local median, though not at the bottom.

Long Lake has no invasive species recorded in Minnesota state databases as of 2024, though prevention practices still apply at all access points. Walleye are documented at Long Lake, one of 13 fish species on record for the lake. A documented public access point at Long Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.