Lilly Lake

On the LakeGrade rubric Lilly Lake fails the cutoffs — a TSI of 72 and persistent algal pressure put it in the bottom tier. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

A TSI above 70 puts Lilly Lake in hypereutrophic territory: visible blooms are common, and clarity rarely climbs even in early summer. A maximum depth of just 8 ft means sediment-bound phosphorus releases back into the water column whenever wind stirs the bottom — a classic shallow-lake dynamic. At 8 acres, Lilly Lake sits below the Minnesota median: a small water where shoreline activity has an outsized effect on water quality. Within the 48 graded lakes of Dakota County, Lilly Lake sits at rank 48, near the bottom of the county list.

Eurasian watermilfoil has been documented at Lilly Lake, requiring shoreline management to keep dense mats from crowding native vegetation. The state fisheries records do not list documented species for Lilly Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. The lake lacks a documented public access point, so visitor use is limited. Multiple sampling years from Minnesota PCA volunteers and partner agencies back the grade, so the letter should hold steady absent a major watershed shift.