ATLANTA (AP) - The U.S. Supreme Court said Monday it will not intervene in a tri-state water dispute between Alabama, Florida and Georgia that until a year ago threatened to severely restrict the Atlanta area's access to its main water supply for roughly 3 million people.

The decision to stay out of the long-running legal feud means that an appeals decision favorable to the metro Atlanta area will stand, a situation bound to frustrate authorities in Florida, Alabama and even southern Georgia who complain Atlanta uses too much water upstream at the expense of wildlife, fisheries and people downstream on the Chattahoochee River.

That river basin serves multiple states. From Atlanta, the Chattahoochee flows south, running along the border of Alabama and Georgia. It merges with the Flint River at the Florida border and becomes the Apalachicola River, which cuts south across the Florida Panhandle and empties into the Gulf of Mexico.

Communities in Alabama and Florida have argued that Atlanta has no legal right to take water from Lake Lanier, a federal reservoir on the Chattahoochee that sits northeast of the city, and that Atlanta's water usage harms fisheries and drinking water supplies downstream.

In 2009, U.S. District Court Judge Paul Magnuson ruled against Atlanta and signed an order that would have severely restricted the city's withdrawals from the reservoir to levels last seen in the 1970s - when the city was a fraction of its current size - unless the political leaders of Alabama, Florida and Georgia struck a deal ending the impasse.

No deal has been struck.

But last year, the 11th U.S. Circuit Court of Appeals overturned the looming water cutoff and found that Atlanta had a claim to water from the reservoir. The court instructed the U.S. Army Corps of Engineers to determine how much water the city can use.