Chemical data from the National Water Quality Monitoring Council (NWQMC) sampled 100 of America’s largest lakes from January 1st, 2020, until July 15th, 2025. The researchers evaluated a lake’s cleanliness level: dissolved oxygen, ammonia, lead, phosphorus, sulfate, total dissolved solids, and turbidity.
What they found was that Lake Superior was the cleanest, and the title for America’s dirtiest lake went to Florida’s Lake Okeechobee.
One cause for the murky appearance of Lake Okeechobee may be the high levels of phosphorus, estimated at 0.18 mg/L, which stimulates algae growth.
“Overall, America’s largest lakes like Okeechobee are technically a little murkier compared to our measurements from 276 lakes last year, but this would not be visible to the human eye,” said David Ciccarelli, CEO of Lake.com.
Each lake was ranked using a score calculated with the following equally-weighed factors:
• Dissolved Oxygen Concentration;
• Ammonia Concentration;
• Lead Concentration;
• Phosphorus Concentration;
• Sulfate Concentration;
• Total Dissolved Solids;
• Turbidity;
• Difference from pH of 7.
The lakes were ranked based on a total pollution score, whereby the higher the pollution score – the dirtier the lake was considered.
Looking at the report, Everglades Foundation CEO Eric Eikenberg said the continuing funding of cleaning Lake Okeechobee is now more important than ever.
“Jeb Bush signed legislation in 2001 establishing a Total Maximum Daily Load (TMDL) of Phosphorus entering Lake O at 140 metric tons. We’ve never come close to meeting the pollution limit over these 20 plus years. The lake is no longer a sponge. It is now a source of excess algae outbreak,” said Eikenberg.
This year. Governor Ron DeSantis signed a budget that allocates over $1.4 billion for Everglades restoration and water quality initiatives and President Trump has been an active proponent of federal funding for Everglades restoration, and a budget request for fiscal year 2026 seeks a record-high amount of $446 million dollars for project dealing with Everglades restoration.
