SC has one of the cleanest lakes in the US, study says. Here’s where to find it

One of the most popular lakes in the Southeast is also one of the cleanest in the United States, a recent study showed.

It’s Lake Hartwell, covering some 56,000 acres between South Carolina and Georgia on the Savannah, Tugaloo, and Seneca Rivers.

The cleanest lake in the U.S. is Lake Superior in Michigan, Minnesota and Wisconsin, according to Fishbox, a fishing forecast platform. Lake Superior is the largest freshwater lake in the world.

The dirtiest is Lake Okeechobee in Florida, which the study said was murky with too much lead.

Fishbox looked at the concentration of dissolved oxygen, ammonia, lead, sulfate, phosphorus, and other factors at 100 large lakes in the U.S., as reported by National Water Quality Monitoring Council samples from Jan. 1, 2020, and July 15, 2025.

The results were reported by Travel + Leisure.

“We are pleased to find that, generally speaking, large lakes remain very clean and safe to swim and fish 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,” Fishbox’s CEO Serge Selezen told T+L. “Clean water isn’t just about human recreation, it’s about maintaining the delicate balance that keeps our fish populations thriving.”

Lake Hartwell was Hartwell Dam and Lake Hartwell Lake was built by the U.S. Army Corps of Engineers between 1955 and 1963 for flood risk management, water quality, water supply, downstream navigation, hydropower production, fish and wildlife protection, and recreation.

The book “History of the Savannah District, 1829 – 1989” by Henry E. Barber and Allen R. Gann said the estimated cost was $68.4 million based on 1948 price levels and preliminary designs. It ultimately cost almost $90 million.

More than 10 million people visit the lake each year.

The town of Andersonville was flooded and according to the Lake Hartwell Guide is a “ghost town lost to time and legend.”

“Some say that parts of the town still exist intact beneath the lake’s depths — buildings, roads, and even a cemetery, untouched by time,” the Guide said. “There’s an eerie sense that Andersonville isn’t gone but merely hidden, slumbering below, waiting to be rediscovered.”

People have felt a strange presence or seen people walking along the shoreline, lights underwater.

But mostly, Lake Hartwell is about fishing, think black bass, striped and hybrid bass, black crappie, bream, and other recreation — swimming, camping, boating, waterskiing.

The average depth is 45 feet, maximum 185 feet. It has 45 boat ramps.

The hydroelectric facility is considered a “peaking power plant.”

“This means that power is not constantly generated. Instead, power is generated at times when electricity is in the greatest demand,” the Corps said.

It has 962 miles of shoreline and a state park just off of Interstate 85 at the South Carolina-Georgia border.

Lake Hartwell State Park has a basketball court, publicly accessible boat ramp and hiking.

“The park is one of a few in the state to offer the unique, single room camper cabins, which offer guests without camping gear an opportunity to experience the feel of camping on Lake Hartwell,” SC State Parks said. In the park are eight cabins, 109 paved campsites, 13 walk-in tent sites and a 140-foot fishing pier.

The other lakes on the cleanest list are:

2. Lake Chelan; Washington

4. Lake of the Ozarks; Missouri

5. Lake Pend Oreille; Idaho

6. Lake Winnibigoshish; Minnesota

7. Kentucky Lake; Kentucky, Tennessee

8. Lake Norman; North Carolina

9. Lake Mead; Arizona, Nevada

10. Flathead Lake; Montana