New Study Ranks Cleanest and Dirtiest Lakes in America

Driving The News

Lake Louise in Florida takes the top spot as the cleanest lake in the USA, new research reveals. Meanwhile, Utah Lake, Utah’s largest freshwater lake, is America’s dirtiest lake. 

The study, conducted by vacation rental platform Lake.com, analyzed all the available chemical data from the National Water Quality Monitoring Council (NWQMC) for 276 US lakes, sampled at shallower depths, from January 1^st, 2023, until May 28^th, 2024. 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.  

Cleanest Lakes in America

Lake Louise, Isleworth, Florida, is America’s cleanest lake. Part of the Butler Chain of Lakes, it is located in an affluent residential area within the greater Orlando metropolitan area, home to Universal Studios Florida. 

Lake Louise’s pH level is 6.98, which is within the optimum range for high-quality aquatic life and human skin. It has an average of 8.26 mg of dissolved oxygen per liter. Acceptable levels of dissolved oxygen start at 6.5 mg/L. Levels below 2 mg/L makes the water hypoxic, causing fish to suffocate.  

Lake Louise has low levels of ammonia compared to other lakes, estimated at 0.004 mg/L. Ammonia is a toxin whose presence above 0.53 mg/L is considered harmful to fish. It also contains a small amount of lead, averaging to 0.20 ug/L.  

Axhandle Lake, Chippewa County, Wisconsin, is America’s second-cleanest lake. It has an incredibly low level of turbidity (1.05 NTU), which indicates the water’s clarity. The lower the turbidity level, the clearer the water. Sulfate levels of just 1.34 mg/L mean the water at Axhandle Lake is smell-free. Normally, these levels should be kept below 500 mg/L, while 1,000 mg/L is technically acceptable but has a cloudy aspect with purgative effects when ingested. 

Bear Gully Lake, Seminole County, Florida, is the third-cleanest lake in the United States. It has a below-average lowest level of Total Dissolved Solids (TDS) of all 276 lakes studied. TDS indicates the general quality of water and refers to the totality of minerals within water, such as sulfates, chlorides, calcium, magnesium, potassium, bicarbonates and sodium. At Bear Gully Lake, TDS averages 99.33 mg/L. The pH is at a healthy 7.57. The ideal pH range for fish to thrive in is between 6.5 up until 9. 

Other lakes named among America’s top ten cleanest include Lake Mooney (Virginia), Aberdeen Lake (Mississippi), Amory Lake (Florida), Lake Downey (Florida), Claytor Lake (Virginia), Sylvan Lake (Florida), and Lake Spivey (Florida). 

Top 10 Cleanest Lakes Ranked 

Dirtiest Lakes  

The title for America’s dirtiest lake goes to Utah Lake. It has an astounding amount of TDS, estimated at 1,221.73 mg/L on average, and a high turbidity of nearly 51 NTU. Sulfate levels here are especially high, averaging almost 268 mg/L. This likely gives it an unpleasant odor. 

The second dirtiest lake in America is Lake J B Thomas in Texas. Its oxygen-poor water is filled with minerals, as reflected in the above-average TDS levels.  

Lake Wichita in Texas is the third dirtiest lake in the US. The high TDS (140 NTU) means its water, whose samples were taken from near the dam, is generally cloudy. It has the most unclear water of all the lakes. 

Lead-contaminated cluster of lakes in Florida 

During their study, the researchers came across an alarming concentration of neighboring lakes in Casselberry, Florida, containing some of the highest levels of lead among all lakes in America sampled at depths up to 5 meters. These include Lake Yvonne, Lake Marie, Lost Lake, Triplet Lake, Secret Lake, Lake Kathryn, Lake Concord, Lake Lotus, Lake Ellen, Trout Lake and Lake Griffin. 

Lead often persists in drinking water due to old lead-based pipe infrastructure, but its presence in lakes is unnatural. Notably, only a fifth of the evaluated lakes had any lead data available. 

Eagle Falls Lake, in California, near the valley where the Coachella festival takes place, has the highest level of lead of all the 56 lakes with available lead data, estimated at a worrying 20 ug/L.  

Top 10 Dirtiest Lakes Ranked 

Side-by-Side Comparison of Cleanest and Dirties Lakes in the United States

National Median Averages 

The median average level of dissolved oxygen among all the 276 evaluated lakes stands at 7.76 mg/L. pH, measured for 270 lakes, deviates by 0.67 points from the ideal water pH of 7. The median average level of ammonia among 178 lakes that did have such data available is 0.017 mg/L.  

Excluding two lead-contaminated lakes – Eagle Falls Lake in California (20 ug/L) and Lake Roberta in Florida (11.59 ug/L) – the median average levels of lead across the remaining 54 lakes is 0.39 ug/L. 

Sulfate levels across 164 lakes averaged 16.94 mg/L. Meanwhile, the median average for TDS is 130.93 mg/L, based on the data for 210 of the evaluated lakes. Turbidity data for 262 lakes varies widely and averages 3.33 NTU, which means the human eye would perceive their water as being crystal-clear. 

David Ciccarelli, CEO of Lake.com, commented on the findings: “American lakes appear to be generally clean. If you are visiting a lake this summer, follow the signage installed nearby which should inform you of whether swimming is allowed and the circumstances in which this can take place.  

“Avoid ingesting any lake water because, while serious contamination instances are rare, some toxins or pH imbalances are not visible to the human eye.  

“Watch out for kids when they splash playfully. Smelly water, caused by high levels of sulfate, will likely have a purgative effect when ingested. Nothing cuts a holiday short like a group of kids feeling nauseous.” 

This study was conducted by Lake.com, a vacation rental platform offering lake houses, cabins and cottages for rent. 

Editors Note

The Methodology and Data Visualizations

Our Methodology

1. The study is based on chemical data from the National Water Quality Monitoring Council, for US lakes, reservoirs and impoundments, sampled between January 1^st, 2023, and May 28^th, 2024, available at: https://www.waterqualitydata.us/ (Accessed May 29^th, 2024); 

2. Eight characteristics reflecting water quality with sufficient data were shortlisted: dissolved oxygen, ammonia, lead, phosphorus, sulfate, total dissolved solids, turbidity and pH; 

3. The researchers converted characteristics results to uniform units or excluded unconvertible units (e.g. samples that express turbidity levels in FTU, rather than the more common NTU); 

4. They applied several filtering criteria, only focusing on locations that contained the word “lake”; whose samples were collected no deeper than at 5 meters due to certain characteristics varying greatly depending on the depth at which they are measured; and whose pH levels are outside the 4-10 range and dissolved oxygen is below 1 in order to eliminate likely human errors in the original data; 

5. Data for various parts of the same lake was combined and averaged, as were the results for characteristics measured several times during the analyzed period; 

6. The quality of pH levels was evaluated based on their difference from the ideal water pH of 7; 

7. The two-part weighting mechanism involves, firstly, a 0-10 scale to evaluate each characteristic compared to minimum and maximum levels for that indicator. To measure a lake’s overall final score, these individual 0-10 scores were then weighed against each characteristic’s worth, which is proportional to how much data was available. The more data points available, the higher the weighing; 

8. The ranking is based on the overall final score, so that the higher this score is, the cleaner the lake. 

Visualization of Cleanest Lake Data

Visualization of Dirtiest Lake Data

Editorial Notes

Because of the inconsistent ways of measuring water quality, the study shortlisted only the lakes with at least five of the aforementioned characteristics available. This resulted in a list of 276 lakes in total, whose cleanliness could be assessed. For the final ranking, each indicator was rated on a 0-10 scale, while the indicator itself was worth a percentage of the total score proportional to how commonly it is measured.