Crystal Lake

Crystal Lake grades an F: water clarity, phosphorus, and chlorophyll-a all rate poorly, placing it among the most stressed lakes monitored in Minnesota. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

The hypereutrophic status — TSI 75 — reflects sustained heavy nutrient loading from the surrounding watershed and frequent algal pressure. Crystal Lake is a shallow lake at 8 ft maximum depth, which means it warms quickly, mixes constantly, and amplifies nutrient inputs. The lake's 379 acres and 5.5 miles of shoreline put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. Within the 9 graded lakes of Blue Earth County, Crystal Lake sits at rank 7, near the bottom of the county list.

Crystal 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 Crystal Lake, one of 12 fish species on record for the lake. Public access is available — the lake is on the Minnesota PCA public-access list. Ice-out has been recorded 12 times at Crystal Lake, with a median around Apr 1. 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.