Many scientists feared a now-scuttled plan to mine next to the Okefenokee Swamp would alter the water levels of the refuge.
The mining company itself disputed those claims, arguing the water it planned to pump from the underlying aquifer would have a negligible impact on the swamp. By releasing preliminary permits for the mine in early 2023, the Georgia Environmental Protection Division seemed to agree.
Now, a new study published last week raises questions about the company and the agency’s conclusions, and the impact any future mining proposals could have on the pristine wetland.
University of Georgia researchers have found that the Okefenokee is more closely tied to the vast aquifer beneath it, suggesting changes in or around the swamp could affect groundwater supplies relied on by millions of people.
Credit: HYOSUB SHIN / AJC
Credit: HYOSUB SHIN / AJC
The findings were published Dec. 9 in the peer-reviewed scientific journal “Environmental Research: Water.”
The Okefenokee Swamp is the largest blackwater wetland in North America and one of the most intact wetland ecosystems left on Earth. It is home to thousands of types of plants and animals, including endangered and threatened species. It also holds millions of tons of peat, a type of decaying plant matter that keeps greenhouse gases out of the atmosphere.
The swamp covers about 700 square miles in southeast Georgia, but below it lies the much larger Floridan aquifer, which stretches 100,000 square miles beneath all of Florida and parts of Alabama, Georgia, Mississippi and South Carolina. Along with irrigating tens of thousands of acres of farmland, the aquifer is the main drinking water source for at least 10 million people, according to the U.S. Geological Survey.
A landmark conservation deal to buy out the company behind the mine, Twin Pines Minerals, put an end for now to the plans to mine on the ecologically fragile eastern edge of the swamp. But other groups have continued to express interest in mining the area.
Scientists say the decades-old conventional wisdom was that the Okefenokee and the Floridan were distinct hydrological systems, separated by a layer of clay known as the Hawthorn Formation. It was believed this largely impermeable layer was a bathtub liner of sorts beneath the Okefenokee, keeping most water from the rain-fed swamp from trickling into the aquifer.
Credit: HYOSUB SHIN / AJC
Credit: HYOSUB SHIN / AJC
The study found the relationship between the two is likely much more complex.
To make that determination, UGA scientists collected and analyzed water pulled from the swamp and groundwater wells nearby for isotopes of hydrogen and oxygen. The presence of these “heavier” isotopes that have more mass can be used to trace water flow.
Credit: HYOSUB SHIN / AJC
Credit: HYOSUB SHIN / AJC
The scientists found groundwater upstream of the Okefenokee was “lighter” than what’s in the swamp, but in parts of the aquifer beneath the refuge, they found “heavier” water. That’s “exactly what one would expect if swamp water were leaking downward and dominating the (aquifer) recharge under the swamp,” the study says.
To further investigate swamp-aquifer ties, the scientists analyzed historical water level data. What they found is that when water levels in the swamp changed, the Floridan aquifer responded about a month later. It’s another sign the two are connected, said Jaivime Evaristo, one of the study’s co-authors and an assistant professor of hydrology and water resources at UGA.
“We see the swamp’s isotopic ‘fingerprint’ showing up in the aquifer beneath and near the swamp, and we see aquifer water levels rising and falling in step with the swamp, just with about a one-month lag,” Evaristo said.
Jordan Clark, a professor of environmental studies at the University of California, Santa Barbara, who was not part of the study, said the findings appear to confirm his long-held view that there is significant interplay between the aquifer and the swamp.
“It must be leaking at some point,” said Clark, who studied southeast Georgia’s hydrology earlier in his career.
Credit: HYOSUB SHIN / AJC
Credit: HYOSUB SHIN / AJC
Twin Pines had requested permission to pull roughly 1.5 million gallons of groundwater from the aquifer each day for its mine, an amount the company claimed would not diminish water levels in the Okefenokee. The study authors say their findings undermine that assertion.
“This withdrawal would have formed a cone of depression in the aquifer that increases vertical leakage and reduces swamp water levels,” said Todd Rasmussen, another of the study’s co-authors and a professor emeritus at UGA.
Efforts to reach Twin Pines’ representatives for comment were unsuccessful. The company’s business registration in Georgia was revoked by the secretary of state’s office earlier this year.
The study has implications for regulators at the Georgia Environmental Protection Division, the authors said.
Since Twin Pines’ plans fizzled this summer, no new proposals to mine the mineral-rich dunes on the swamp’s eastern flank known as Trail Ridge have emerged. But there are still tens of thousands of acres of private land in the area, and some property owners have voiced interest in mining their land, if it’s proved it can be done safely.
This study should change how future water withdrawals near the Okefenokee — and across coastal Georgia — are evaluated, the authors say.
“The swamp is not an isolated ‘bathtub,’ but rather a leaky reservoir intimately linked to the Floridan aquifer,” the study states. “A stress to one will affect the other.”
Asked about the findings, EPD spokeswoman Sara Lips said the agency has highly trained professionals on staff who are capable of evaluating water withdrawal impacts.
“EPD is committed to transparency in decision-making and welcomes technical discussions on water withdrawal permitting,” Lips added.
Josh Marks, the president of Georgians for the Okefenokee, disagrees, calling the study evidence that EPD is “simply incapable of regulating mining at the Okefenokee.”
“Accordingly, it’s time for Gov. (Brian) Kemp and the (Georgia) Legislature to step in and finally pass the Okefenokee Protection Act to prohibit mining on Trail Ridge once and for all,” Marks said.
The Okefenokee Protection Act — House Bill 561 — was introduced last legislative session and would prohibit state regulators from issuing, modifying or renewing any mining permits on Trail Ridge. Environmentalists have pushed to pass the bill and others like it for several years, but the measures have been held up in committee.
A spokesman for Kemp declined to comment, saying the office does not comment on proposed or pending legislation.
A note of disclosure
This coverage is supported by a partnership with Green South Foundation and Journalism Funding Partners. You can learn more and support our climate reporting by donating at AJC.com/donate/climate.
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