Washington Lake

Washington Lake earns an F: 116 µg/L of phosphorus and clarity at 4.5 ft signal heavy nutrient loading from the surrounding watershed. 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.

A TSI in the eutrophic range signals a lake doing what nutrient-loaded waters do — supporting an active algal community at the cost of clear water. Washington Lake is unusually deep for Minnesota at 51 ft, which buffers the lake against summer warming and helps the deep water stay oxygenated. With 1,516 acres of surface and 12.1 miles of shoreline, Washington Lake is a large water by Minnesota standards — recreational pressure is spread across a long shoreline. Washington Lake sits at rank 9 of 14 in Le Sueur County, in the lower half of the local distribution.

Washington 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 Washington Lake, one of 18 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 — 78 observations on file, with a median ice-out around Apr 4. The grade is supported by multiple sampling years from Minnesota PCA volunteers and partner agencies, giving the letter a reasonably stable foundation.