As I’ve been following the discussions about Clarks Hill Lake’s water levels, it seems like the water is finally rising after having been down forever. I’m not getting into the issues involving the U.S. Army corps of Engineers. Instead, I want to bring up a surprising scenario involving the lake at full level.
You could say it’s a pressing matter.
When the powers that be decide to build huge reservoirs like Clarks Hill Lake, they do so with good intentions: flood control and power production. Other reasons for building large lakes include fisheries and leisure activities such as boating and camping. All kinds of studies, forethought, and precautions go into the selection of a dam site. But maybe there’s something critical they gloss over or plain out miss.
Bear with me as I turn back time. My sisters and I had a small inflatable swimming pool when we were kids. It was blue and yellow and round, the tiniest of man-made water bodies. Dad put it in the front yard but soon realized it would kill the grass if he didn’t move it. He tried to pull it to a new spot but it wouldn’t budge. He had to drain it to move it. Water is heavy stuff, and therein lies a tale of destruction.
Clarks Hill Lake holds 71,535 acres of water. Precisely 325,851 gallons of water are in one acre-foot of water. A gallon of water weighs 8.34 pounds. Do the math. That’s an astronomical amount of weight pressing on the rock strata beneath the counties the lake covers. Since the dam is a gravity-type dam, it has to weigh more than the water pressing against it. The dam contains more than 3 million pounds of reinforcing steel and 1 million cubic yards of concrete. Along with the lake, add the dam’s weight onto the strata below. All that weight wasn’t part of nature’s plan, you know. Something’s got to give.
Not that long ago, an earthquake in China’s Sichuan Province left 80,000 people dead or missing. Well, guess what: A growing number of scientists believe a nearby reservoir triggered the disaster. A Columbia University scientist believes the 320 million tons of water in the Zipingpu Reservoir less than a mile from a major fault caused the quake.
Here’s another case of what is known as Reservoir Induced Seismicity. Back in 1959, engineers dammed the Zambezi River to create Lake Kariba. With good intentions, they created the lake to provide electricity to Northern and Southern Rhodesia’s mines.
At the time it was a major engineering feat, but there was a problem – a big problem: The Lake Kariba area forms part of the east African Rift System and a network of faults runs through the region. Before the lake backed up, the earthquake intensity was very low. As the lake began to fill, earthquake activity increased due to the extra weight of the water. The ground had to adjust to Lake Kariba’s weight.
In 1967, the Koyna earthquake killed more than 200 people in Maharashtra, India. Just like that, thousands were homeless. The epicenter was just three miles from the largest dam in Maharashtra.
There’s plenty of evidence out there that says lake levels and earthquake activity correlate. So, while the debate over the lake levels goes on, here’s something to ponder: Is Lincoln County susceptible to a major earthquake? Small quakes are nothing new. A few years back on a Sunday morning, a tremor hit the county. I happened to be there when it hit.
Of Georgia’s 13 seismic areas, most are near Lincoln County. A Georgia seismicity map reveals six areas of activity all around the lake. The county’s geology is unique, as Graves Mountain proves. (Go to www.usgs.gov and check out the Georgia earthquake records. It’ll give you something to think about.)
On March 13, 2007, a large boom and a succession of vibrations hit eastern Georgia, especially Evans. Sure enough, a map in The Emergency Manager’s Guide to Earthquakes in Georgia, prepared in February 1999, reveals a fault line running through Columbia County, not far from the dam.
So while the debate over lake levels goes on, at least the lake isn’t as heavy as it could be and no one is claiming a reservoir-induced quake is imminent. No one can predict earthquakes, not yet anyway. Of course, psychics, cranks and self-deluded people have long tried to predict quakes.
I’ve been researching the matter for a book I’m working on and I stumbled across some curious information. Studies have proven that an increase in “lost pet” notices takes place prior to a big quake. Folks go looking for their missing dog, but Fido, having senses we don’t, realizes a quake is coming and heads off to a safer place.
So, when the lake does fill, and some day it will, you might want to keep a closer eye on your dog’s whereabouts. And if you notice a slew of dogs heading out of the county, you might just find yourself on shaky ground.
(Tom Poland is a South Carolina writer and University of Georgia graduate who writes a weekly column about the South.)