Diamond Lake

Diamond Lake earns an F: 96 µg/L of phosphorus and clarity readings still being added signal heavy nutrient loading from the surrounding watershed. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

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. At only 6 ft deep, Diamond Lake is shallow — wind keeps the water column mixed and sediment resuspension drives phosphorus levels harder to manage. Diamond Lake is small — 52 acres alongside 1.2 miles of shoreline — which makes it sensitive to even modest changes in watershed runoff or recreational pressure. Within the 95 graded lakes of Hennepin County, Diamond Lake sits at rank 72, near the bottom of the county list.

Diamond Lake has no invasive species recorded in Minnesota state databases as of 2023, though prevention practices still apply at all access points. 7 fish species are on record, with panfish making up the recreational core. No formal public access is documented at Diamond Lake — most use is by shoreline residents and their guests. The lake has a partial ice record — 10 observed ice-outs, centered near Mar 26. 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.