By Bill Rankin, The Atlanta Journal-Constitution

The federal appeals court in Atlanta on Tuesday handed Georgia an enormous victory in the tri-state water litigation, overturning rulings by a federal judge that could have had catastrophic consequences for the metro area.

The court threw out a 2009 ruling by Senior U.S. District Judge Paul Magnuson, who had found it was illegal for the Corps of Engineers to draw water from Lake Lanier to meet the needs of 3 million metro residents. In its decision, the 11th U.S. Circuit Court of Appeals found that a purpose of the man-made reservoir was to supply water to the Atlanta region.

Magnuson had also set a doomsday clock ticking for Georgia, Alabama and Florida to arrive at a water-sharing agreement. If the states could not reach a settlement by July 2012, Magnuson said, metro Atlanta would only be allowed to take the same amount of water it received in the mid-1970s — when the population was less than one-third its current size.

That deadline is no longer in effect.

Instead, the 11th U.S. Circuit Court of Appeals set a new deadline. It gave the Corps one year to make a final determination over water allocation from Lake Lanier. And the court reminded the Corps that the water litigation has already been going on for more than two decades.

“Progress towards a determination of the Buford Dam’s future operations is of the utmost importance to the millions of power customers and water users that are affected by the operations of the project,” the court said. “The stakes are extremely high, and all parties are entitled to a prompt resolution. Accordingly, the process for arriving at a conclusion of the bounds of the Corps’ authority should be as swift as possible without sacrificing thoroughness and thoughtfulness.”

“At first glance it appears that the state of Georgia has won a great victory,” said a statement issued by the office of Gov. Nathan Deal. “The 11th Circuit panel has ruled unanimously that Lake Lanier was built for the purpose of water supply for the metro Atlanta area. This means that the lake will continue to be available to meet Georgia’s needs.”

The 95-page ruling, issued by a three-judge panel that heard arguments over the dispute in March, was unanimous.

In their ruling, the judges made important findings. Among them: they determined Magnuson erred in concluding that water supply was not an authorized purpose of the Buford Dam project.

“It’s a very good day for the state of Georgia,” lawyer Patricia Barmeyer, who represents the Atlanta Regional Commission, said.

The ruling is “a complete victory for Georgia,” said Todd Silliman, one of the lawyers representing Georgia.

“My initial reaction is that it helps put us on a more level playing field in negotiations,” said state Rep. Buzz Brockway, R-Lawrenceville. “We definitely had the most to lose.”

Staff writer Aaron Gould Sheinin contributed to this article.