With drought tightening its grip on the Southeast, the Atlanta area's reservoirs are almost down to the dregs — the dirtier, more bacteria-laden water close to the bottom — and it's going to require more aggressive and more expensive purification.
Some communities are buying stronger water-treatment chemicals and looking into other measures to make the water drinkable.
The problem is that the water levels on Lakes Lanier and Allatoona, the main sources of water for metropolitan Atlanta's 5 million residents, have descended almost to the "dead zone," a layer low in oxygen and high in organic material — that is, dead and decaying plants and animals.
Even with standard treatment, the water at that level can have a strong odor, taste and color. State officials consider the water "suspect" at best.
"Is there water there that could be used? Yes," said Carol Couch, Georgia's top environmental official. "But it's not exactly high quality."
Officials vow to do 'whatever it takes'
The dropping of the water levels into the dead zone won't have a major effect on the city of Atlanta, because it does not draw its water straight from Lake Lanier, but from the Chattahoochee River, which is fed by Lanier.
By the time Atlanta takes its water from the Chattahoochee, it has been circulating for a while and has been exposed to more oxygen, and is thus not as dirty.
But the booming suburbs to the north draw their water directly from Lanier and Allatoona.
The water utility in Cumming, a northern Atlanta suburb on the banks of Lanier, has brokered a deal to buy a new chemical — potassium permanganate — to treat the water pumped from the depths, and is planning to dredge silt and sediment from the bottom of the lake in search of cleaner water.
"The city will go after the water no matter how far the lake recedes," said Jonathon Heard, the city's director of utilities. "We intend to provide water for the citizens of this area, whatever it takes."
Gwinnett County, the state's second most populous county, has an intake pipe that is about 15 feet down into the dead pool. It plans to spend more money on ozonation, or the infusing of ozone gas into the water to destroy bacteria and other microorganisms. More ozonation will require more electricity.
In Forsyth County, a suburb on the lake's western shore, officials are buying more chemicals to treat the dirtier water.
State: About 80 days of clean water left
The state warns that Lake Lanier could have less than 80 days of water stored in its conservation pool, the main area from which communities typically draw their water. Below that level is the dead pool.
The Army Corps of Engineers predicts there is at least 120 days of water left, but that includes the water in the dead pool.
Jim Connaughton, chairman of the White House council on environmental quality, said Washington is helping governments plan in case they have to tap the depths, but he did not elaborate.
"We want to plan for the worst but be prepared to take advantage of what could be the best," he said.
On Friday, the Corps announced a plan to reduce the amount of water released downstream from Lake Lanier. That could help communities that draw their water straight from the reservoirs. But it is unlikely to do much more than slow the falling levels of the lake, since a dry winter is forecast.
"I think we can muddle through this winter with good conservation and good water management. But the big question is: Will we have enough rainfall to build up our reserves for next summer?" said Georgia state climatologist David Stooksbury. "The hopes are dim."
At Lanier, Allatoona and some smaller reservoirs, the water has already dropped so much that it has fallen below at least some of the intake pipes.
The water utility in Cumming has installed an emergency pump to deal with the problem, while other local governments, including heavily populated Cobb County, are scrambling to figure out what to do to reach the water.