Updated Aug 2026
Ontario Lake Water Quality
Water-quality measurements for 2,766 lakes across 40 counties.
Lake Map
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Divisions
Ontario is in Canada, with measurements from the provincial agency. Compare with other Canadian provinces or open the country hubs.
All 2,766 Ontario lakes in this index carry recent water-quality measurements from the Ontario Ministry of the Environment, Conservation and Parks, spread across 40 counties.
Lake Match
Which lake suits how you actually use one?
Six questions — swimming, fishing, quiet, cabins, drive time — and a shortlist of lakes that fit, with the water quality behind each one.
Source: the Ontario Ministry of the Environment, Conservation and Parks, not the EPA. See data sources.