America’s Cleanest Lakes Have Changed Dramatically, Only 4 Of Last Year’s Top 10 Remain
America has a new cleanest lake. Lake Chelan in Washington has overtaken Lake Superior to lead Lake.com’s 2026 ranking of the cleanest lakes in the United States.
Lake.com, a travel platform dedicated exclusively to stays and experiences by the water, released its findings on August 27 to coincide with the United Nations’ World Lake Day.
“Lakes have always been places where people go to swim, boat, fish, explore and spend meaningful time together, and World Lake Day gives us an opportunity to celebrate them while also paying attention to their health,” says David Ciccarelli, founder and CEO of Lake.com, in the official press release.
But the new winner is only part of the story. The other part is that the top 10 list is no longer the same. Only four of last year’s cleanest lakes remained in this year’s ranking.
World Lake Day Returns For Its Second Year
The United Nations designated August 27 at the end of 2024, choosing the anniversary of the first World Lake Conference, held in 1984, to raise awareness about the importance of lakes and the need to protect and restore them.
Pristine clear waters of Lake Superior near Munising, Michigan U.S.
The United Nations Environment Programme (UNEP) monitors 4,000 large lakes and reports that more than a quarter are becoming increasingly turbid, while almost 15% show rising levels of organic matter.
Through the UN Decade on Ecosystem Restoration, countries are encouraged to improve monitoring, reduce pollution and restore freshwater ecosystems.
“Today, some of the world’s best-known and most important lakes are a shadow of what they were just a few decades ago,” says Dianna Kopansky, the head of the Freshwater Ecosystems and Wetlands Unit of UNEP, in last year’s official statement.
“We need to reverse this decline. If we don’t, it could be calamitous for the hundreds of millions of people who rely on lakes for their survival,” she adds.
How America’s Cleanest Lakes Were Ranked
The Lake.com report examined data from the National Water Quality Monitoring Council for 100 of America’s largest lakes by surface area.
A sailboat on Lake Martin in Alabama, U.S.
Researchers assessed eight indicators: dissolved oxygen, ammonia, lead, phosphorus, sulfate, total dissolved solids, turbidity and deviation from a neutral pH of 7. They used the most recent 12-month median for each indicator, drawing from data reported between January 1, 2021, and July 30, 2026.
Lakes needed data for at least three indicators to qualify. Sixty-seven met that requirement, up from 46 in the 2025 report.
Researchers combined the available indicators into a pollution score ranging from 0 to 10, with lower scores indicating cleaner water, to determine the cleanest and dirtiest lakes.
The annual results do not prove that lakes that dropped out of the ranking suddenly became cleaner or dirtier. The qualifying pool expanded from 46 to 67 lakes, and the methodology also changed. Travelers should still consult local water-quality reports because conditions can vary by location and date.
The 10 Cleanest Lakes In America In 2026
Lake Chelan is the cleanest with a pollution score of 0, while Lake Superior ranked second with a score of 0.28. Lake Martin in Alabama completed the top three.
Sunny day at Lake Chelan, Washington
Rainy Lake, Minnesota; Franklin D. Roosevelt Lake, Washington; Lake Koocanusa, Montana; Lake Michigan; Lake Hartwell, Georgia–South Carolina; Lake Huron, Michigan; and Kentucky Lake, Kentucky–Tennessee ranked in the top 10.
Only Four Lakes Remained In The Top 10
Lake Chelan, Lake Superior, Lake Hartwell and Kentucky Lake are the only returning members of the 2025 top 10.
“What’s encouraging is that many of the largest lakes in the U.S. are, on the whole, clean and enjoyable places to visit. The differences we see from lake to lake also reinforce the importance of continued monitoring and care for these incredible natural resources,” says Ciccarelli.
Lake of the Ozarks in Missouri, Lake Pend Oreille in Idaho, Lake Winnibigoshish in Minnesota, Lake Norman in North Carolina, Lake Mead in Arizona and Nevada and Flathead Lake in Montana dropped out of the top 10 in this year’s ranking.
The 10 Dirtiest Lakes In America In 2026
Great Salt Lake received the maximum pollution score of 10. However, since it is a naturally saline lake with no outlet, evaporation leaves salts and minerals behind in high concentration. Its saltiness is natural rather than caused by pollution.
Lake McConaughy in Nebraska ranked second-dirtiest, partly due to its cloudy water and an unbalanced pH, while high phosphorus levels and a similar pH imbalance pushed Wisconsin’s Lake Winnebago into third place. Lake Vermilion in Minnesota ranked fourth, largely because it had the second-lowest oxygen level in the study.
Devils Lake in North Dakota ranks fifth. It is also a saline lake, but nowhere near as salty as Great Salt Lake.
Lake Mattamuskeet recorded the highest ammonia level among the freshwater lakes in the bottom 10, while Lake Moultrie in South Carolina ranked 18th dirtiest overall due to its highest lead measurement.
This article was originally published on Forbes.com