If common sense didn’t do it, maybe the realization that if metro Atlanta can’t tap its main reservoir for water, it will be too costly for Georgia to go any other route than negotiate with its neighboring states on a water-sharing agreement.

That was the conclusion of a task force asked by Georgia Gov. Sonny Perdue to investigate the possibility of bringing new reservoirs into the system. The task force reported that it would take a minimum of eight years and cost hundreds of millions of dollars to bring the new reservoirs online.

That certainly exceeds a federal judge’s deadline of 2012 for Georgia, Florida and Alabama to come to an agreement over water sharing. The judge ruled that Georgia had minimal rights to use water from Lake Lanier for its drinking water supply, and that puts the state in a desperate hunt for water.

It also should place Gov. Perdue in a more accommodating mood to negotiate, since the judge also ordered that if no agreement is reached, it sends Atlanta’s withdrawals back to the levels they were in the 1970s – a time when the city was much, much smaller.

“Georgia absolutely must negotiate with the two other states,” Sally Bethea, director of the Upper Chattahoochee Riverkeeper, said.

She’s right. This war over water has spanned decades without resolution. It is long past time to come to the negotiating table with serious recommendations and an agreement all three states can live with.