( When it's dry it's dry all over accor...)Past droughts geographically widespread in the West, according to tree-ring data

By using data from tree rings, University of Arizona researchers conclude that water supply for those western rivers fluctuated in synchrony during periods of severe drought. The study goes back almost 800 years in the Salt-Verde basin and covers waterways from the states of Arizona, Colorado, New Mexico, Utah and Wyoming.

The project's overall conclusion is that severe droughts and low-flow conditions in one basin are unlikely to be offset by abundant streamflow in the other basin.

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

Tree-ring-based reconstructions of streamflow can peer back into time much further than the records available from stream-flow gauges. Ester said such reconstructions could provide important insights into the hydrologic variability of a river basin over time.

The findings represent just the first phase of a study partnered by SRP and The University of Arizona's Laboratory of Tree-Ring Research. UA scientists Katherine K. Hirschboeck, an associate professor of climatology, and David M. Meko, an associate research professor, conducted the tree-ring analysis.

The study's second phase, which will begin this month, will take a closer look at more recent history when scientists from the tree-ring lab will re-core trees in the Salt and Verde watersheds to gather new data from the last 40 years, a period when the watersheds have experienced both record wet and record dry episodes. The findings
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Source:University of Arizona