Lab: Water runs dry across Ariz.

By Evan Pellegrino
Arizona Daily Wildcat
August 30, 2005

The UA Laboratory of Tree-Ring Research concluded that when one of Arizona's water sources runs dry, the state cannot depend on other sources to provide water.

The lab was paid $85,500 by the Salt River Project and the city of Phoenix to study the tree rings of Arizona's major water resources; the Salt, Verde and Colorado rivers.

Tree-ring researchers analyzed annual stream flow records preserved in the rings of trees. This data is supposed to help researchers better assess drought conditions and water management.

"Prior to the findings from this study, the conventional wisdom was the runoff from the Colorado River would be available to make up for deficits on the Salt and Verde rivers during time of extreme drought," said Charlie Ester, the project manager of Water Resource Operations, in a press release. "The bottom line is the Upper Colorado Basin and the Salt and Verde basins work together as one entire region."

The results of the study have shown droughts and floods in Arizona's water basins will not be saved by other water sources because they all depend on each other, according to a press release.

The Salt River Project is an Arizona political subdivision and is Phoenix's largest provider of water, according to the project Web site.

The UA researchers also examined Arizona's drought history to help officials manage water during the state's current and future droughts.

"The drought has eased quite a bit on the short term, "said David Meko, associate research professor at the lab. "But (the drought) could come right back."

Although the state has experienced adequate rainfall since the winter, the current weather conditions could be a wet year in the middle of a long string of dry years, said Katie Hirschboeck, associate professor of climatology.

Tree-ring analysis has proved this type of pattern has occurred before, meaning a wet year may not be the end of the drought.

"Tree rings are the only way to go back that far in time," said Jon Skindlove, a meteorologist for the Salt River Project.

The agencies were "concerned about the flow of the Colorado River," Skindlove said. "The results put things in context."

The last tree-ring samples studied from the Colorado River are from 1964, a time period that includes the biggest drought in the 20th century. The latest core samples from the Salt and Verde rivers ended in 1988.

After looking at the lab's results, the Salt River Project asked the UA to carry out an additional study that started this month. The funding, which is about $270,000, will allow researchers to collect updated core samples from trees in the Salt River Verde basin, Hirschboeck said.

This will allow scientists to see how trees respond to the situations of the current drought.

"Some trees may show narrow rings," Meko said. He also expects some trees may not gain a ring at all because of the drought.