Cleaner Lakes Than Manito Lake by Dam

Reading the cohort

Only 2 lakes within a 30-mile radius score better than Manito Lake by Dam's Grade D. The narrow set of options reflects either a fairly clean lake to begin with or a region without a wide range of cleaner alternatives — the trip-planning decision is more constrained than the headline "cleaner lakes nearby" suggests.

The nearest cleaner alternative — Crystal-Morgan Lake in Morgan County — sits 15.6 miles from Manito Lake by Dam, 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, Manito Lake by Dam 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.