Some state political leaders, including Gov.-elect Nathan Deal, say the state needs to build more man-made lakes to store water. But reservoirs actually reduce water availability overall, especially for Atlanta's downstream neighbors in South Georgia, Alabama and Florida, according to the researchers. Because reservoirs contribute to water evaporation, less water finds its way downstream, said John Kominoski, a researcher in the UGA School of Ecology.
"We don't have canyons in the Southeast as they do in the Southwest, so our reservoirs are shallow and lose capacity more rapidly through evaporation," explained Kominoski, part of a group of scientists who analyzed freshwater resources in the Southwestern and Southeastern United States.
Their article, "Reclaiming freshwater sustainability in the Cadillac Desert," focused mainly on the Southwest and tested predictions in environmentalist Marc Reisner's book, "Cadillac Desert: The American West and Its Disappearing Water."
The scientists' analysis was published in a special edition of the journal Proceedings of the National Academy of Sciences. The study's authors also include University of South Carolina geographer William Graf and Tushar Sinha, a North Carolina State University research scientist. John Sabo of Arizona State University was the lead author.
For the most part, "Cadillac Desert" was on the mark, they said. The book predicted the West's water would be inadequate to meet the growing demands of cities, agriculture and industry, and those predictions are playing out as Reisner predicted.
But the scientists also found out that the Southeast also has a relatively low capacity for water storage, Graf said.
The group's calculations probably underestimate the water supply challenges of Georgia and other Southeastern states, Kominoski said. They used data from 1950 to 1999. But some of the highest temperatures and most extreme droughts ever recorded in the Southeast have come in the past decade.
Reservoirs - not just future man-made lakes, but those that already exist - also pose a threat to aquatic wildlife, Kominoski said.
Reservoirs change the water temperatures downstream as well as in the reservoirs themselves, and change the natural water flow patterns in rivers. Native species of fish have a harder time surviving under those circumstances, opening the door for invasive species to come in.
"Our current system doesn't support the needs of people, let alone ecosystems," Kominoski said. "Reservoirs and interbasin transfers don't increase the availability of water. They just change the location of the water."
Building reservoirs just means less water for those communities downstream or from nearby communities, if the water is piped from adjacent watersheds, he said.
Georgia and other Southeastern states need to find a new water strategy beyond reservoirs, Kominoski said - water conservation reclamation, more efficient use and even small-scale storage like underground cisterns that can collect rainwater from building roofs.
"Because we have mostly inland metropolitan areas in small watersheds, we need to use less water. Less water comes to us, and our ability to store water is challenged by our climate and geographic location," he said.