Untitled DocumentEvaluation of paleodata to determine past, present, and future hydrologic variability in Arizona
Macro Theme Area:
River Systems [Project ID: R28]
PI:
Juan Valdes
CO-PI(s):
Vic Baker, David Meko
Basin focus:
Colorado
Specific area in
basin /
field sites:
N/A
Summary/Goals: The research is TRIF-supported (beginning in 2003 for 3 years) and has three interrelated activities: a) development of paleohydrologic records based on tree-rings for the case study region. This work will include field collection of new tree-ring chronologies from hydrologically targeted areas and synthesis of the resulting data with pre-existing tree-ring records; b)development of hydroclimatic records of floods for the case study region; and c)statistical characterization of droughts. Based on instrumental records and paleo records resulting from the tasks above we will estimate the bivariate probability distributions of extreme events, particularly droughts, including both severity and duration. The risk function will also result from this task
Even though the results of the project will be applicable to the entire state, particular emphasis will be given to the Salt-Verde basin.
Activities and outcomes during past year:
Significant correlations of our tree-ring indices to stream flow at Horseshoe Dam and for the entire Verde mean. The preliminary results show (a) that we will get some pretty good reconstructions, and (b) that July-Oct. is not correlated with the tree-rings at all.
Our statistical studies showed that Colorado River Basin precipitation is sensitive to climatic fluctuations associated with El Nino-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) at oscillations of five and 15 years. The occurrence of extreme SPI (Standardized Precipitation Index) associated with ENSO and PDO as a common product of these indices that highlights moisture conditions affected by common enhancement phases of ENSO and PDO. We found that in southern Arizona, for example, drier than normal conditions prevail during the high SOI phase (corresponding to a La Nina event). The low PDO phase is thought to enhance the dry condition in Arizona during the high SOI phase.
Plans for the upcoming year:
We will continue doing research on droughts in the Colorado River Basin and Arizona after the completion of this TRIF supported project
Organization Involvement:
The Tree-Ring Lab is doing the work described in section a) of the sumary: development of paleohydrologic records based on tree-rings for the case study region.
