Ann Lake

Ann Lake earns a D — measurements through 2024 show persistent nutrient pressure that limits clarity through the summer. Phosphorus is the parameter holding the grade back — runoff from the surrounding watershed appears to keep nutrient levels elevated through the summer.

Hypereutrophic conditions mean the lake is operating at the upper end of the productivity scale, with all the bloom risk that implies. Ann Lake is a shallow lake at 14 ft maximum depth, which means it warms quickly, mixes constantly, and amplifies nutrient inputs. Ann Lake covers 370 acres alongside 3.4 miles of shoreline — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Within Pope County's 25 graded lakes, Ann Lake ranks 16 — below the local median, though not at the bottom.

No invasive species are currently listed at Ann Lake — the lake remains off the Minnesota infested-waters roster. The fishery includes walleye alongside the lake's other 10 documented species — a notable draw for Minnesota anglers. Public access is available — the lake is on the Minnesota PCA public-access list. 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.