“We mainly wanted to measure the Savannah River’s metabolism,” said Flite, the Southeastern Natural Sciences Academy research vice president. “But along the way we came upon some other surprises.”
During a five-day float trip aboard a boat crammed with monitoring gear, Flite and his colleagues followed a column of river water from Augusta to a point 145 miles downstream, where tidal influences begin to alter its flow.
The idea, he said, was to determine if computer models used by environmental regulators to license industrial and municipal waste discharges could be improved.
“They put a parcel of water into the computer and add in the discharges and any changes that are proposed,” he said. “What we did was to mimic what the modelers do, but in the actual water that goes downriver.”
During the June voyage, constant readings were taken to measure dissolved oxygen, carbon dioxide, salinity, temperature and other factors.
Most studies don’t monitor so many parameters, he said, but taken together, the information helps define a living, breathing river that changes significantly as it moves downstream.
Although federal regulators have suggested that low oxygen levels in Savannah Harbor could be improved by limiting waste discharges far upstream in Augusta, monitoring data show water quality recovers, and in some cases improves, long before it reaches coastal waters.
The study also found that carbon dioxide levels were exceptionally high in Augusta – in fact, oversaturated to the point it was escaping from the water.
Downstream, however, levels were so low that the water was absorbing carbon dioxide from the atmosphere.
The changes, Flite said, might be due to photosynthesis in which algae consume carbon dioxide and release oxygen during the day. Then, at night, bacteria consume dissolved oxygen, but generate more carbon dioxide.
“Plants rule the day,” he said, “and bacteria rule the night.”
One of the most interesting surprises of the trip was a series of occasional – and unexpected – spikes in carbon dioxide levels in the water column.
The scientists noticed those anomalies occurred where large bluffs rise from one side of the channel. Those sites turned out to be the hidden locations where groundwater from subterranean aquifers empties into the Savannah River.
“Carbon dioxide is high in groundwater, naturally,” Flite said. “One of the things we’ve wondered is, where does natural material come in? We didn’t expect to see it in a CO2 survey but we did.”
Once compiled and validated, the data will be shared with Georgia’s Environmental Protection Division and the S.C. Department of Health & Environmental Control, which regulate dozens of waste generators vying for a share of the river’s limited assimilative capacity.
A second round of the ongoing experiment is planned for early next year, during the winter.