Cottonwood Lake

Cottonwood Lake grades an F: water clarity, phosphorus, and chlorophyll-a all rate poorly, placing it among the most stressed lakes monitored in Minnesota. 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.

Hypereutrophic conditions mean the lake is operating at the upper end of the productivity scale, with all the bloom risk that implies. At only 7 ft deep, Cottonwood Lake is shallow — wind keeps the water column mixed and sediment resuspension drives phosphorus levels harder to manage. The lake's 383 acres and 3.8 miles of shoreline put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. Cottonwood Lake ranks 2 of 5 in Lyon County — solidly in the upper half of the local distribution.

No invasive species are currently listed at Cottonwood Lake — the lake remains off the Minnesota infested-waters roster. Walleye are documented at Cottonwood Lake, one of 10 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 5 times at Cottonwood Lake, with a median around Mar 21. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.