What is the cleanest lake near Hannen Lake?

Kent Park Lake in Johnson County holds a Grade B water quality score and is 22 miles from Hannen Lake.

Why is Hannen Lake not Grade A?

Hannen Lake holds Grade F, with about 1.2 ft of water clarity and 141 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 Hannen Lake in Iowa, with strictly higher numeric grade scores and sufficient monitoring data.

Cleaner Lakes Than Hannen Lake, Top 1 Within 30 Miles

Reading the cohort

Just one nearby water body scores higher than Hannen 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 nearest cleaner alternative — Kent Park Lake in Johnson County — sits 22 miles from Hannen Lake, 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, Hannen Lake is the practical choice and the cleaner options are reserved for purpose-specific visits.

Lakes are graded A to F on nutrients and algae — total phosphorus, total nitrogen, chlorophyll-a, and turbidity — measured against the EPA National Lakes Assessment 2022 condition classes for that lake's own ecoregion, so a lake is judged against the lakes it would naturally resemble. A higher letter reflects measurably lower nutrient and algae levels, 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. The full grading formula is on our methodology page.

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.