Upper Estuary Lake

On the scoring rubric Upper Estuary Lake grades a D: clarity at 2.1 ft and 52 µg/L of phosphorus keep it in the lower bracket for Douglas County. Secchi readings are the weakest of the three parameters, suggesting suspended sediment or algal biomass dominates the optical signal.

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. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake's surface area is not consistently recorded across state datasets — physical context remains partial. Upper Estuary Lake sits at rank 32 of 44 in Douglas County, in the lower half of the local distribution.

Upper Estuary Lake has no invasive species recorded in Wisconsin state databases as of 2025, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Upper Estuary Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. 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.