Lake.com, home to vacation rentals on or near the water, today unveiled the findings of its newly released 2025 report ranking “America’s Cleanest and Dirtiest Lakes.” The comprehensive study, which evaluates 100 of the largest U.S. lakes using up-to-date chemical data, confirms Lake Superior as the cleanest, while Lake Okeechobee tops the list of lakes on the opposite side of the spectrum.
Key Highlights
• Lake Superior is the United States’ cleanest lake.
• Lake Okeechobee is the dirtiest lake in the US today.
• Out of the 100 largest lakes in America, 46 had up-to-date chemical composition data.
The study analyzed all available chemical data from the National Water Quality Monitoring Council (NWQMC) for 100 of America’s largest lakes, sampled from January 1, 2020, to July 15, 2025. The researchers evaluated eight of the most commonly measured characteristics that can suggest a lake’s cleanliness level: dissolved oxygen, ammonia, lead, phosphorus, sulfate, total dissolved solids, turbidity, and pH. They found that 46 lakes had at least three of these pollution factors measured within the indicated period.
Cleanest Lakes: A Testament to Crystal-Clear Quality
• Lake Superior stands out as the nation’s cleanest lake, showcasing exceptionally clear, healthy water with oxygen levels at 10.45 mg/L, turbidity at a mere 0.46 NTU, and total dissolved solids of just 44.04 mg/L.
• Close contenders such as Lake Chelan and Lake Hartwell also performed remarkably well, underlining the trend toward excellent water quality among America’s largest lakes.
• Overall, the report finds that many of the largest U.S. lakes maintain balanced pH levels (average 7.96), healthy dissolved oxygen (7.29 mg/L), and moderate turbidity (9.54 NTU).
“As part of our mission to foster sustainable enjoyment and awareness of lake environments, we’re proud to bring further clarity to America’s largest freshwater bodies,” said David Ciccarelli, CEO of Lake.com. “Accurate, respectful reporting, like the one in our 2025 Cleanest and Dirtiest Lakes report, enables communities to see where progress is thriving—and where collaboration can drive positive change.”
Having grown up on the cleanest lake’s Canadian shores, Ciccarelli adds, “Lake Superior truly lives up to its name—its crystal-clear, oxygen-rich waters make it America’s cleanest large lake.”
Dirtiest Lakes: Room for Improvement
• Lake Okeechobee, Florida, was named the dirtiest of the 100 evaluated, with lead contamination at 0.67 µg/L, turbidity of 34.36 NTU, and elevated phosphorus levels of 0.18 mg/L—a combination that contributes to murky appearance and potentially stimulates algae growth.
• Other lakes that ranked lower on the cleanliness scale include American Falls Reservoir (Idaho), due to detectable ammonia levels; Lake Texoma (Oklahoma–Texas), with low oxygen and high sulfate and dissolved solids; and Pyramid Lake (Nevada), with exceptionally high TDS and pH deviation.
• The report conveys this information with impartiality, avoiding any judgment, while offering a factual foundation for communities and agencies to address these concerns constructively.
Takeaways
“Compared to a similar study we carried out last year, comprising a different sample size, larger lakes seem to have three times less sulfates and nearly four times less TDS,” said David Ciccarelli. “However, ammonia concentrations were five times higher in the lakes it was measured, while lead contamination was slightly lower.
“Overall, America’s largest lakes this year are technically a little murkier compared to our measurements from 276 lakes last year, but this would not be visible to the human eye.
“We are pleased to find that, generally speaking, large lakes remain very clean and safe to swim in, though monitoring any signage near swimming spots and adhering to the indicated advice may save you from catching a rare but nasty stomach bug.”
To read the full report, visit:
https://www.lake.com/company/reports/cleanest-and-dirtiest-lakes-in-america/
About Lake.com
Lake.com specializes in family-friendly lake houses and vacation rentals within a 15-minute drive of lakes, bays, rivers, canals, and coasts. Focusing on family, friendship, and caring for the natural world, Lake.com blends tradition with technology, offering a return to the simple pleasures of life for families vacationing in the great outdoors. The platform provides detailed information on amenities, attractions, and local services to help families plan memorable vacations.