Mandall Lake

Mandall Lake pulls a D on the LakeGrade rubric — phosphorus loading and limited clarity hold it below the Minnesota average. The lake's weakest score is on Secchi depth — the water looks more turbid than its phosphorus number alone would predict.

Eutrophic conditions are the baseline here: clarity drops noticeably in late summer, and dissolved oxygen near the bottom can become a concern. A maximum depth of 26 ft puts Mandall Lake in the middle of Minnesota's depth distribution. The lake is compact at 47 acres, with 1.2 miles of shoreline and little volume to buffer nutrient inputs. Within Chisago County's 31 graded lakes, Mandall Lake ranks 21 — below the local median, though not at the bottom.

Eurasian watermilfoil is established at Mandall Lake, which can dampen recreational access and pressure the native plant community. Walleye are documented at Mandall Lake, one of 5 fish species on record for the lake. No formal public access is documented at Mandall Lake — most use is by shoreline residents and their guests. Ice-out has been logged at Mandall Lake more than two dozen times, putting the median around Apr 7 — a useful baseline for tracking climate trends. The grade is supported by multiple sampling years from Minnesota PCA volunteers and partner agencies, giving the letter a reasonably stable foundation.