Crystal Lake

On the LakeGrade scale Crystal Lake grades a B, with clarity at 10.2 ft and 20 µg/L of phosphorus placing it above the Minnesota median. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

A TSI near 46 places Crystal Lake in the mesotrophic band — moderate productivity, with seasonal swings between clearer spring water and richer late-summer conditions. At 55 ft of maximum depth, Crystal Lake stratifies reliably through the summer — the hypolimnion stays cooler and clearer than the surface layer suggests. At 1,413 acres, Crystal Lake is one of the larger lakes in Otter Tail County, with 8.9 miles of shoreline supporting multiple distinct use patterns. Within Otter Tail County's 97 graded lakes, Crystal Lake ranks 52 — below the local median, though not at the bottom.

Zebra mussels have been documented at Crystal Lake, which alters the filter-feeding balance and can paradoxically increase water clarity while disrupting the food web. Walleye are documented at Crystal Lake, one of 17 fish species on record for the lake. Public access is available — the lake is on the Minnesota PCA public-access list. 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.