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Home/Trend Reports

Updated August 2026

Trend Reports

Data-driven reports highlighting the biggest changes and notable findings.

Snapshot10 entities

Cleanest Lakes

The highest-graded lakes in Minnesota and Wisconsin

Decline10 entities

Most Polluted Lakes

Lakes with the worst water quality grades

Water quality report cards for lakes across 49 US states. A–F letters are US. Ontario and Québec have 0 letters. Country hubs publish official ratings that are not LakeQuality A–F grades. Graded A–F on phosphorus, nitrogen, algae, and turbidity, plus water clarity, depth, and fish from EPA and state agency data.

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CanadaCanada

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Lake Water Quality by CountryLakes by Country

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Supported by advertising. LakeQuality is free to read; ads never influence our grades or rankings — see our editorial policy.

Lodging results and prices come from Stay22, which sources live availability from Booking.com, Vrbo, and Expedia. Booking through those links may earn us a commission at no extra cost to you, and never changes a lake’s grade or where it ranks.

US lake grades use EPA National Lakes Assessment ecoregion condition classes on samples from the EPA Water Quality Portal and state agencies. Canadian measurements come from provincial open-data programmes, not the EPA. EU bathing waters use the EEA Bathing Water Directive. International named-lake chemistry is attributed on each country page. See data sources and methodology. Not affiliated with any government agency.

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