Cleaner Lakes Than Mayo Reservoir
1 higher-graded lake within 30 miles, ranked by grade improvement and proximity.
Mayo Reservoir carries a Grade C (Fair) water quality score. Within 30 miles, 1 lake holds a higher grade. Lake Butner (Granville County, Grade B, 22.8 mi away) is the closest meaningful upgrade.
Reading the cohort
Just one nearby water body scores higher than Mayo Reservoir 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 nearest cleaner alternative — Lake Butner in Granville County — sits 22.8 miles from Mayo Reservoir, putting it firmly in "destination trip" rather than "neighborhood swap" range. The water-quality gap has to be the deciding factor; for a casual outing, Mayo Reservoir is the practical choice and the cleaner options are reserved for purpose-specific visits.
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
Every lake on LakeQuality has a calculated grade from EPA Water Quality Portal samples — secchi depth, total phosphorus, and chlorophyll-a measured against Metropolitan Council thresholds. 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.