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History of our water source

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POSTED: October 13, 2011 3:30 p.m.

the water I drink comes from a large limestone aquifer called the Floridan that underlies all of Florida, past Charleston, almost to Macon and past Mobile.
How was it formed, how safe is it and how long will it last? I am sure it would take volumes and a lifetime of study to answer these three questions completely, but in a thumbnail, here goes.
A very long time ago, the Appalachian mountain chain was as high as the Alps. The earth went through – and continues to go through – periods of global warming and cooling that have nothing to do with human activity. During periods of warming, the polar ice caps melt, sea level rises and the oceans warm.
The shells of generation after generation of sea life accumulate to form a thick layer of calcareous shells many yards deep on the sea floor. Change comes as it always does. The earth cools, more water accumulates in the polar ice caps, which grow larger and bring on the glaciers of the ice ages.
Sea level recedes, exposing all of the continental shelf off Georgia to the sky. Weather erodes the mountains, and the sediment washes over the sea bed and accumulates over it. Change comes again, the world warms, sea levels rise and the warm oceans return and shell accumulation begins again. Sea level rise in the past was much higher than it is today. Waycross used to be beachfront living.
This process is repeated many times. The world is not static. The collision of tectonic plates causes some areas to rise and others to sink. Out in West Georgia, the uplift has exposed the Floridan aquifer to the surface. Groundwater in the limestone layer flows downhill toward the Georgia coast.
The acidic rainwater slowly dissolves the limestone rock to create voids like one finds in Swiss cheese. The rate of flow toward the coast is slow, only inches per year, like water through a sponge.
The water taken from Floridan wells to serve Savannah last fell as rain some 5,000 years ago. When were the pyramids built? A Floridan well I inspected with a video camera to a depth of 450 feet in Camden County yields water about 23,000 years old since it fell as rain. The water in the Floridan aquifer has been cleaned by Mother Nature for thousands of years, and I have no doubts about its safety.
When European explorers came to this area, they found blue holes of clean fresh drinking water welling up offshore of Georgia. Ships could just pull up alongside, drop their pails in and pull up drinking water out of the ocean. When this happens on land, we call it artesian springs.
The historic district homes of Savannah are three stories tall, but not four stories because three stories was as high as the artesian pressure would push water through the pipes. The Forsyth Park Fountain ran on artesian spring pressure when it was installed. Think about it – there were no electric motors to power water pumps in 1858. The pressure was so great that the original pool surrounding the fountain had to be enlarged because it sprayed outside the pool and showered the strolling public.
How long will the aquifer continue to provide excellent drinking quality water for the people of southern and coastal Georgia? Forever – if we take care of it.
And that will take two basic tactics. First, don’t suck so much water out so fast that aquifer water pressure cannot keep out the seawater. Once seawater contaminates the limestone, the stone will grab the sodium, turning the contaminated part of the aquifer brackish for years or generations.
This is the main concern fueling the debate over the locations and withdrawal limits from the Floridan along the Georgia coast. There are so many straws in the Floridan in Savannah, mostly around the paper plant, that instead of water shooting three stories into the air, we now have to pull it up from 250 feet down.
The second area of concern is what we put on and into the ground in West Georgia, where the aquifer is exposed at the surface. We are concerned not only about what farmers apply to their fields, but also where industrial and municipal operations locate the outfalls for their waste streams. Yes, the earth can and does clean the water, but we can overload the system capacity and break it.
The Chinese did it to their groundwater resources and have rendered many of them unfit for human consumption. Those who do not learn from or remember history are doomed to repeat it.

Gardner is the University of Georgia extension agent for Bryan County and can be reached at dgardner@uga.edu.

 

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