Outlet of Onamia Lake on the Rum River

On the LakeGrade rubric, Outlet of Onamia Lake on the Rum River pulls an A: clarity readings still being added and 25 µg/L of phosphorus put it in the top bracket for Minnesota. With phosphorus and chlorophyll-a scored, the sub-grades cluster within a letter of each other, pointing to stable conditions rather than one specific stressor.

Trophically, Outlet of Onamia Lake on the Rum River reads as oligotrophic — nutrient-poor, clear, and ecologically more sensitive to disturbance than richer lakes. At only 10 ft deep, Outlet of Onamia Lake on the Rum River is shallow — wind keeps the water column mixed and sediment resuspension drives phosphorus levels harder to manage. At 1,044 acres, Outlet of Onamia Lake on the Rum River is one of the larger lakes in Mille Lacs County, with 17.8 miles of shoreline supporting multiple distinct use patterns. Among the 11 graded lakes in Mille Lacs County, Outlet of Onamia Lake on the Rum River ranks 1 — in the top quartile locally.

Zebra mussels have been documented at Outlet of Onamia Lake on the Rum River, which alters the filter-feeding balance and can paradoxically increase water clarity while disrupting the food web. The state fisheries records do not list documented species for Outlet of Onamia Lake on the Rum River, which usually reflects a lack of formal fisheries survey work rather than an empty lake. No formal public access is documented at Outlet of Onamia Lake on the Rum River — most use is by shoreline residents and their guests. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.