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Late afternoon sun over Slim Lake, scattering a bright path across wind-textured water
NR

Ontonagon County Lake Quality

Michigan, 14 lakes — no lake here has enough monitoring data for a grade

Ontonagon County holds 14 monitored lakes. With a sample that small the county-level summary describes those specific waters, not necessarily every water body in the county. No lake in Ontonagon County has enough sampling behind it for an A–F grade yet. The 14 monitored lakes below carry whatever clarity, phosphorus, and chlorophyll-a measurements exist.

Most of the county's monitored lakes are shallow, under 50 feet, which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed.

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Quick Answers for Ontonagon County

Cleanest lakes in Ontonagon County →Cleanest lakes in Michigan →Safest swimming lakes in Michigan →

Planning a trip? Check special fishing regulations for Clouds, Lake of the — or check the official Michigan fishing regulations.

All Lakes in Ontonagon County

14 lakes · 0 graded, 14 not rated0 graded lakes · 14 not rated, hidden

#LakeGradeClarityPhosphorusAlgaeTrophicMax DepthAccess
NRClouds, Lake of theOntonagonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples70 ftNot recorded
NRSixmile LakeOntonagonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples37 ftNot recorded
NRMirror LakeOntonagonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples33 ftNot recorded
NRVictoria ReservoirOntonagonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples67 ftNot recorded
NRClark LakeOntonagonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples25 ftNot recorded
NRBass LakeOntonagonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples28 ftNot recorded
NRBond Falls FlowageOntonagonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples28 ft✓ Public
NRDeadman LakeOntonagonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples35 ft✓ Public
NRSteusser LakeOntonagonNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNo recent samples✓ Public
NRCourtney LakeOntonagonNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRSudden LakeOntonagonNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNo recent samples✓ Public
NRVictoria ReservoirOntonagonNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRWeidman LakeOntonagonNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRMirror LakeOntonagonNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded

NR = not rated: there is not enough recent sampling to support a letter. That is EPA Integrated Reporting Category 3 (insufficient information), not a failing grade. How grading works.

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Other Counties in Michigan

Dickinson County

43 lakes · Avg grade A

Clare County

47 lakes · Avg grade A

Ogemaw County

50 lakes · Avg grade A

Cheboygan County

31 lakes · Avg grade A

Roscommon County

26 lakes · Avg grade A

Gladwin County

29 lakes · Avg grade A

See how Ontonagon County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all United States (49 states), Canada (Ontario, Québec, Nova Scotia, British Columbia and Newfoundland and Labrador), and 38 other country hubs..

Source: EPA National Aquatic Resource Surveys, 2026.