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

Mason County Lake Quality

Michigan, 31 lakes, average grade B (Good)

Mason County's 31 monitored lakes fall in the moderate-density bracket for Michigan. The county-level average smooths over real differences — a single agricultural watershed near the southwest corner can pull the average down even if the rest of the county runs clean. 3 of those lakes carry an A–F grade. The county-level summary describes that subset, not every water body listed. With an average grade of B, Mason County sits comfortably above the Michigan median.

The county's lakes lean shallow, which makes the grades sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest lake on the books is Gun Lake (A); the most-stressed is Upper Hamlin Lake (C).

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Where to stay near Mason County

Top-rated places to stay near Mason County

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Quick Answers for Mason County

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

Planning a trip? Check special fishing regulations for Gun Lake, whether the fish are safe to eat, and the best times to fish — or check the official Michigan fishing regulations.

Fishing in Mason County

Mason County Fishing Guide

Fish species and best-graded lakes in Mason County

All Lakes in Mason County

31 lakes · 3 graded, 28 not rated3 graded lakes · 28 not rated, hidden

#LakeGradeClarityPhosphorusAlgaeTrophicMax DepthAccess
1AGun LakeMasonA14 ft9 µg/L2.2 µg/LNo recent samples22 ft✓ Public
2CUpper Hamlin LakeMasonC6 ft29 µg/L6.2 µg/LNo recent samplesNo recent samplesNot recorded
3CLower Hamlin LakeMasonC11.5 ft26 µg/L3.3 µg/LNo recent samplesNo recent samples✓ Public
NRHamlin LakeMasonNR9 ftNo recent samplesNo recent samplesNo recent samples65 ft✓ Public
NRChancellor LakeMasonNR26 ftNo recent samplesNo recent samplesNo recent samples50 ftNot recorded
NRHoags LakeMasonNR11.5 ftNo recent samplesNo recent samplesNo recent samples18 ft✓ Public
NRThunder LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples30 ftNot recorded
NRFord LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples80 ft✓ Public
NRRound LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples10 ftNot recorded
NRTallman LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples5 ft✓ Public
NRHackert LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples15 ft✓ Public
NRLincoln LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples13 ftNot recorded
NRLong LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples33 ftNot recorded
NRPere Marquette LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples38 ft✓ Public
NREmerson LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples37 ftNot recorded
NRLudington Storage ReseMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRHopkins LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples25 ftNot recorded
NREden LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples38 ftNot recorded
NRWoodruff LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples37 ftNot recorded
NRPleiness LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples38 ftNot recorded
NRNorth Oxbow LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples27 ftNot recorded
NRBass LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples45 ftNot recorded
NRSaint Marys LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samples20 ftNot recorded
NRBartons LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRCartier LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRGooseneck LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRBatcheller LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRCasin LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRPicnic LakeMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRLost LakesMasonNRNo recent samplesNo recent samplesNo recent samplesNo recent samplesNo recent samplesNot recorded
NRSouth Oxbow LakeMasonNRNo 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 Mason 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.