Tree rings show Southwest may not be done with drought

TUCSON, Ariz. (AP) — A vigorously wet winter has buoyed spirits in Arizona and other Southwest states parched by drought. But history recorded in tree rings suggests it's far too soon to even think the region is near an end to its long dry spell.

Researchers say tree rings have shown that wet periods aren't uncommon during droughts. So the wet weather that has greened up Arizona, made dry rivers run and even caused flooding isn't necessarily a sign of things to come.

Wet breaks in past big droughts usually have lasted only a year or two before a return to dry conditions, said David Meko, a principal researcher at the University of Arizona's Laboratory of Tree-Ring Research.

Scientists can see a historical record of past droughts by looking at the thickness of a tree's rings. Since trees grow more during wet periods, the rings will grow thicker at those times. Trees grow less in dry times so those rings will be thinner.

According to tree ring analysis, there have been numerous extended droughts throughout the West over the last 500 years. The current drought has been partly blamed for the proliferation of tree-killing insects and has contributed to enormous wildfires of recent years.

How long it takes to overcome a drought varies.

Building up depleted reservoirs, restoring soil moisture and allowing vegetation to recover, particularly trees whose crowns and roots have been damaged by prolonged lack of water, could take years, said Thomas Swetnam, director of the tree ring laboratory.

"This is a deep deficit, many years in the making," said Kelly Redmond, Nevada state climatologist with the Western Regional Climate Center in Reno.

"You wouldn't want to see the kind of thing that would get you out of it in one year," because it would mean inundation and massive flooding, with its own consequences, he said.

Besides, Redmond said, only part of the West has really seen strong rain or snowfall: California, most of Utah and Nevada, Arizona, New Mexico and southern Colorado. Elsewhere, it's been lackluster at best, he said.

Still, some people are just happy to see the wet weather that has been moving regularly through the area in recent months.

"The lakes are filling and it looks pretty promising," said Bob Prosser, who runs the Bar-T-Bar Ranch in northern Arizona. "I think it's late enough and wet enough that it'll certainly do some good."

At a minimum, he said, he'll have a good forage crop for his cattle this spring.

Bob Ginn, a retired Air Force colonel and flight instructor in Tucson, said he sees the rainfall "as a definite plus."

"I like the rain as a change from normal Tucson, dry and windy, and I like what it does because we garden, and I'm somewhat of a nature photographer so I expect a lot of wildflowers," Ginn said.