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COnion Valley Reservoir @ Dam
Humboldt County, Nevada · 3.4 mi from Knott Creek Reservoir
- +Two grade letters higher (F → C)
- +Lower phosphorus (50 vs 145 µg/L)
Cleaner Lakes Than Knott Creek Reservoir
1 higher-graded lake within 30 miles, ranked by grade improvement and proximity.
Knott Creek Reservoir carries a Grade F (Algae-prone) water quality score. Within 30 miles, 1 lake holds a higher grade. Onion Valley Reservoir @ Dam (Humboldt County, Grade C, 3.4 mi away) is the closest meaningful upgrade.
Reviewed by LakeQuality Editorial Team · Updated
Reading the cohort
Just one nearby water body scores higher than Knott Creek 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 closest cleaner alternative — Onion Valley Reservoir @ Dam in Humboldt County, Grade C — sits 3.4 miles from Knott Creek Reservoir. 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 Onion Valley Reservoir @ Dam is mostly a habit change rather than a logistics change.
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.