Abstract:
New tree-ring records of ring-width from remnant preserved wood
are analyzed to extend the record of reconstructed annual flows
of the Colorado River at Lee Ferry into the Medieval Climate
Anomaly, when epic droughts are hypothesized from other
paleoclimatic evidence to have affected various parts of western
North America. The most extreme low-frequency feature
... of the new
reconstruction, covering A.D. 762-2005, is a hydrologic drought
in the mid-1100s. The drought is characterized by a decrease of
more than 15% in mean annual flow averaged over 25 years, and by
the absence of high annual flows over a longer period of about
six decades. The drought is consistent in timing with dry
conditions inferred from tree-ring data in the Great Basin and
Colorado Plateau, but regional differences in intensity emphasize
the importance of basin-specific paleoclimatic data in quantifying
likely effects of drought on water supply. 
