What is the cleanest lake near Ann Lake?

Ml-Thains Lake in Mille Lacs County holds a Grade C water quality score and is null miles from Ann Lake.

Why is Ann Lake not Grade A?

Ann Lake holds Grade F, with about 2 ft of water clarity and 73.5 µg/L of phosphorus. The letter is nutrients and algae against that lake’s EPA ecoregion classes. Clarity is shown separately. Cleaner alternatives nearby have a strictly higher nutrient-and-algae score.

Are these recommendations based on real data?

Yes. Every grade is calculated from EPA Water Quality Portal samples for the lake. Recommendations are limited to lakes within 30 miles of Ann Lake in Minnesota, with strictly higher numeric grade scores and sufficient monitoring data.

Cleaner Lakes Than Ann Lake, Top 1 Within 30 Miles

Cleaner Lakes Than Ann Lake

1 higher-graded lake within 30 miles, ranked by grade improvement and proximity.

Ann Lake carries a Grade F (Algae-prone) water quality score. Within 30 miles, 1 lake holds a higher grade. Ml-Thains Lake (Mille Lacs County, Grade C, null mi away) is the closest meaningful upgrade.

Ml-Thains Lake

Mille Lacs County, Minnesota · mi from Ann Lake

+Two grade letters higher (F → C)
++3.3 ft water clarity
+Lower phosphorus (27 vs 73.5 µg/L)

Reading the cohort

Just one nearby water body scores higher than Ann Lake on the EPA metrics within a 30-mile radius. The single cleaner option (below) is the practical alternative; beyond that, the next-cleanest lakes sit farther out and warrant a longer drive only if the water-quality difference is the deciding factor.

The closest cleaner alternative — Ml-Thains Lake in Mille Lacs County, Grade C — sits miles from Ann Lake. At that distance, the substitution cost is essentially zero: same drive time, same regional access, demonstrably cleaner water on the EPA indicators. For repeat visitors who care about clarity or phosphorus levels, swapping the routine to Ml-Thains Lake is mostly a habit change rather than a logistics change.

The EPA water-quality grading combines clarity (Secchi depth), phosphorus, and chlorophyll-a measurements from state environmental sampling. A higher letter grade reflects measurably cleaner water on those indicators, not subjective beauty or access quality — a Grade A lake might have worse boat-launch facilities or shoreline access than a Grade C neighbor, so the ranking is one input alongside the rest of trip planning. See the methodology page for the full grading formula.

How this list is built

Rated lakes on LakeQuality have a letter from EPA Water Quality Portal samples — nutrients and algae measured against EPA National Lakes Assessment ecoregion classes. Secchi is shown, not scored. To suggest cleaner alternatives, we filter lakes within 30 miles to those with a strictly higher numeric score, then rank by grade improvement with a small proximity tiebreak. Cross-state and limited-data lakes are excluded so the list stays locally relevant.