Washburn Lake

On the LakeGrade rubric, Washburn Lake pulls an A: clarity at 14.0 ft and 11 µg/L of phosphorus put it in the top bracket for Minnesota. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

A TSI value of 39 puts Washburn Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. Washburn Lake is unusually deep for Minnesota at 111 ft, which buffers the lake against summer warming and helps the deep water stay oxygenated. At 1,590 acres, Washburn Lake is one of the larger lakes in Cass County, with 19.8 miles of shoreline supporting multiple distinct use patterns. Among the 133 graded lakes in Cass County, Washburn Lake sits at rank 53, above the county median.

Eurasian watermilfoil has been documented at Washburn Lake, requiring shoreline management to keep dense mats from crowding native vegetation. The fishery includes walleye alongside the lake's other 21 documented species — a notable draw for Minnesota anglers. Public access is available — the lake is on the Minnesota PCA public-access list. Ice-out has been logged at Washburn Lake more than two dozen times, putting the median around Apr 19 — a useful baseline for tracking climate trends. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.