Upper Orono Lake

Upper Orono Lake grades an F: water clarity, phosphorus, and chlorophyll-a all rate poorly, placing it among the most stressed lakes monitored in Minnesota. 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.

At a TSI of 68, Upper Orono Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. 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 Orono Lake ranks 21 of 24 in Sherburne County — at the lower end of the locally monitored distribution.

Zebra mussel presence at Upper Orono Lake means the lake's clarity numbers carry an asterisk — filtered water is not the same as nutrient-poor water. The state fisheries records do not list documented species for Upper Orono Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. A documented public access point at Upper Orono Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. Ice-out has been recorded 5 times at Upper Orono Lake, with a median around Apr 3. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.