1
BWillow Lake
Harrison County, Iowa · 26.9 mi from Blue Lake
- +Two grade letters higher (F → B)
- ++3.9 ft water clarity
- +Lower phosphorus (35 vs 194.5 µg/L)
Cleaner Lakes Than Blue Lake
2 higher-graded lakes within 30 miles, ranked by grade improvement and proximity.
Blue Lake carries a Grade F (Algae-prone) water quality score. Within 30 miles, 2 lakes hold a higher grade. Willow Lake (Harrison County, Grade B, 26.9 mi away) is the closest meaningful upgrade.
Reviewed by LakeQuality Editorial Team · Updated
2
COldham Lake
Monona County, Iowa · 19.1 mi from Blue Lake
- +Two grade letters higher (F → C)
- ++4.2 ft water clarity
- +Lower phosphorus (46 vs 194.5 µg/L)
Reading the cohort
Within 30 miles of Blue Lake, 2 lakes score higher on EPA water-quality metrics than its Grade F. The short list means the alternatives are real upgrades but not interchangeable — each carries its own access, size, and species mix worth checking before substituting it into a weekend plan.
The nearest cleaner alternative — Willow Lake in Harrison County — sits 26.9 miles from Blue 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, Blue 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.