Upper South Long Lake

Upper South Long Lake comes in at a B on the grading rubric — a respectable showing for a Minnesota lake of its size and depth. Clarity is the limiting factor — phosphorus is reasonable but suspended particles or algal cells keep water transparency below Minnesota norms.

The lake sits in the mesotrophic zone — the band where most well-managed Minnesota lakes fall. The lake bottoms out at 47 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. At 804 acres, Upper South Long Lake fits the Minnesota median for monitored lakes, with 6.3 miles of shoreline. Upper South Long Lake ranks 91 of 120 in Crow Wing County — at the lower end of the locally monitored distribution.

Zebra mussels have been documented at Upper South Long Lake, which alters the filter-feeding balance and can paradoxically increase water clarity while disrupting the food web. Walleye are documented at Upper South Long Lake, one of 16 fish species on record for the lake. Public access is available — the lake is on the Minnesota PCA public-access list. The lake has a long ice-out record — 29 observations on file, with a median ice-out around Apr 15. 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.