Friday, May 18, 2007

Colorado River streamflow history reveals megadrought before 1490
An epic drought during the mid-1100s dwarfs any drought previously documented for a region that includes areas of Arizona, Colorado, New Mexico, Utah and Wyoming. The six-decade-long drought was remarkable for the absence of very wet years. At the core of the drought was a period of 25 years in which Colorado River flow averaged 15 percent below normal.

The new tree-ring-based reconstruction documents the year-by-year natural variability of streamflows in the upper Colorado River basin back to A. D. 762, said the tree-ring scientists from The University of Arizona in Tucson who led the research team.

The work extends the continuous tree-ring record of upper Colorado streamflows back seven centuries earlier than previous reconstructions.

Smack in the middle of the Medieval Warm Period. I believe. . . .the Anasazi collapse was later than this. I recall that this Great Draught was supposedly blamed for the Anasazi collapse, but in recent years explanations have turned more towards social explanations. If they were this severe for an extended period of time, one might think that no social structure could keep things going for that long in such difficult conditions, so perhaps it was draught after all and the Anasazi just couldn't cope whatever they tried.