Lake Superior Crowned Michigan’s Cleanest Lake in New Study

Photo by Timm Stein

Article courtesy of Lake.com. 

• A new study has revealed that Michigan is home to some of America’s cleanest lakes in 2026. 
• Lake Superior is revealed to have the second-lowest pollution score in the study, while Lake Michigan has the seventh-lowest score. 
• Lake Huron, which is located between Michigan and the Canadian province Ontario, is also revealed to have a low pollution score. 
• Meanwhile, Lake Erie is named the dirtiest lake in Michigan. 
• Overall, Lake Chelan is named the cleanest lake in America as of 2026, while Great Salt Lake is identified as the dirtiest. 
• Over 60 major lakes in America were assessed across eight different categories.

A new report has revealed the cleanest and dirtiest lakes in America, with Lake Chelan ranking as the cleanest while Great Salt Lake in Utah ranks as the dirtiest.

The study, conducted by vacation rental platform Lake.com, analyzed all the available chemical data from the National Water Quality Monitoring Council (NWQMC) for 100 of America’s largest lakes, sampled from January 1st, 2021, until July 30th, 2026. The study evaluated eight of the most commonly measured characteristics that can indicate a lake’s cleanliness level:

1. Dissolved oxygen
2. Ammonia
3. Lead
4. Phosphorus
5. Sulfate
6. Total dissolved solids
7. Turbidity
8. pH levels

A total of 67 lakes reported at least three of these pollution factors and therefore qualified for the study. The findings were put into an index to produce a pollution score out of 10 to determine the cleanest and dirtiest lakes based on hygiene, pollution, and more.

Michigan’s Findings: 

The study reveals that Michigan is home to three of America’s top 10 cleanest lakes.

Lake Superior, which is located along Michigan’s Upper Peninsula, has the second-lowest pollution score in the overall study.

The lake is revealed to have the lowest turbidity in the study (0.54 NTU), low TDS levels (74 mg/L), and high oxygen levels (10.58 mg/L).

This means that the lake has excellent water quality, with minimal algae growth, which helps to support a healthy aquatic ecosystem.

Overall, Lake Superior has a pollution score of just 0.28 out of 10.

Lake Michigan has the seventh-lowest pollution score in the study, with an overall score of 0.87 out of 10.

The lake has one of the highest dissolved oxygen levels in the study, with a concentration of 10.6 mg/L. Lakes with high oxygen levels can offer greater protection for aquatic life and also have improved water quality.

Lake Michigan also has low levels of phosphorus, with a concentration of just 0.013 mg/L. Lakes with high phosphorus levels often have excess algal growth, low oxygen levels, and degraded water quality.

Lake Huron, which is located between Michigan and the Canadian province Ontario, has the ninth-lowest pollution score in the study, with an overall rating of 1.07 out of 10.

The data reveals that the lake’s dissolved oxygen levels are notably high at 9.74 mg/L.

Notably, Lake Huron also has low ammonia and lead levels, with scores of 0.01mg/L and 0.081 µg/L, respectively.  Lakes with high ammonia and lead levels can be dangerous to fish, as well as human health.

Meanwhile, Lake Erie is named the dirtiest lake in Michigan, with a pollution score of 2.3. This is due to the fact that the lake’s dissolved oxygen levels are relatively low at 7.57 mg/L, which damages the water quality and the lake’s aquatic ecosystem.

Lake Erie also has a high turbidity score of 5.58 NTU, which negatively impacts water quality.

The top 10 cleanest lakes in America

Overall, Lake Chelan in Washington state is named the cleanest lake in America. Lake Chelan has a turbidity of just 2.00 NTU, meaning it’s extremely clear, and has one of the lowest TDS levels at 30.25 mg/L. Lake Chelan also experiences low sulfate levels of 3.65 mg/L.

Meanwhile, Great Salt Lake in Utah is America’s dirtiest lake. Its water carries an extremely high mineral load, with the total dissolved solids (TDS) of 134,500 mg/L, which is much more than any other lake in the study. TDS refers to the total minerals within water, including sulfates, chlorides, calcium, magnesium, potassium, bicarbonates, and sodium, and indicates the general quality of water. While not necessarily a direct indicator of pollution itself, the levels highlight how dangerous it could be to ingest any water from the Great Salt Lake due to its extreme chemistry.

The Great Salt Lake is also the most poorly oxygenated lake in the ranking, with dissolved oxygen of just 3.65 mg/L. It also reports the highest ammonia of any lake in the top ten dirtiest ranking at 0.92 mg/L, along with elevated lead at 2.09 µg/L. The Great Salt Lake is not a freshwater lake and is a terminal lake. Therefore, there is no outlet for any mineral or chemical buildup.

“America’s largest lakes remain, on the whole, clean and pleasant to swim in,” said David Ciccarelli, CEO of Lake.com. “Even the lakes at the top of our dirtiest table sit within the range you would expect for large natural bodies of water, which shows that there is good maintenance and care for them.

“With that in mind, some monitoring of lakes throughout the country is uneven from one lake to the next, so anyone looking to visit a lake needs to check any signage near their local swimming spot and follow the advice given to them. No lake in the ranking is inherently dangerous, but you could be at risk of a stomach bug.”

The rest of the study: 

The top 10 dirtiest lakes in America

Lake McConaughy in Nebraska and Lake Winnebago in Wisconsin rank second and third-dirtiest, respectively. Lake McConaughy has turbidity levels of 5.50 NTU, while Lake Winnebago, Wisconsin’s largest inland lake, receives a high pollution score in the study due to its high levels of phosphorus, which are 0.09 mg/L, along with a pH deviation of 1.58.

The fourth dirtiest lake in America is Lake Vermilion in Minnesota. Lake Vermilion is the second least oxygenated lake, behind Great Salt Lake, with dissolved oxygen of just 3.90 mg/L.

Devils Lake in North Dakota is the fifth dirtiest lake in the country and is likely to be the smelliest of all, as it has the highest levels of sulfate (639 mg/L) due to no natural outlet to dilute sulfates over time. The smell of sulfate is often described as similar to ‘rotten eggs’.

Despite ranking as the eighteenth dirtiest lake overall, Lake Moultrie in South Carolina is the most lead-contaminated lake included in the study, with samples detecting lead at 17.2 µg/L. There is no safe level of lead.

Lake Mattamuskeet in North Carolina shows the highest ammonia of any freshwater lake in the top ten, with a concentration of 0.67 mg/L. Ammonia should not be present at all in clean water, and when levels reach 0.53 mg/L, the water becomes harmful to fish.

The report was compiled by Lake.com, the vacation rental platform offering 75,000 properties near the water across North America and Europe, where families experience the great outdoors.

Sources:

Lake.com via the National Water Quality Monitoring Council.

Methodology:

1. This study uses data from waterqualitydata.us to rank the 100 largest US lakes by surface area based on how dirty they are.
2. Each lake was ranked using a score calculated with the following equally-weighted factors:

• Dissolved Oxygen Concentration;
• Ammonia Concentration;
• Lead Concentration;
• Phosphorus Concentration;
• Sulfate Concentration;
• Total Dissolved Solids;
• Turbidity;
• Difference from pH of 7.

3. The study used the most recent 12-month median for each indicator, drawn from data reported between January 1st, 2021 and July 30th, 2026.
4. Lakes with fewer than three factors available in the official data were excluded, resulting in a ranked list of 67 of the largest lakes in the US whose cleanliness could be measured.
5. The lakes were ranked based on a total pollution score, whereby the higher the pollution score – the dirtier the lake was considered.

The complete ranking (from dirtiest to cleanest) 

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