The Current Drought In Context: A Tree-Ring Based Evaluation of Water Supply Variability for the Salt-Verde River Basin; 2008 Final Report to Salt River Project

Tree-ring cores collected in 2005 were combined with existing collections to produce a new tree-ring based streamflow reconstruction for the combined Salt+Verde+Tonto watershed covering the period 1330-2005. The new reconstruction reveals that recent individual years (1996 and 2002) were unsurpassed in terms of low flow, with 2002 having an unprecedented number of locally absent (missing) rings. The multi-year persistence of the current drought of 1996-2006 was not unprecedented in the reconstruction. The median interval between “drought relieving” wet years was 3 years, the longest interval was 22 years (1382-1403) and 28 other droughts were more continuously severe in terms of “consecutive years below normal.” The overall conclusion is that despite the single-year severity of 1996 and 2002, the current drought is by no means unique in the long-term record.