RECONSTRUCTING STREAMFLOW TIME-SERIES IN CENTRAL ARIZONA USING MONTHLY PRECIPITATION AND TREE-RING RECORDS

An adaptive, three-way interpolation model based on multiple discrimin ant analysis, multiple linear regression, and normal ratio methods was used to reconstruct streamflows for three gauges in central Arizona f or the period from 1580, using available annual tree ring indices and monthly precipitation. The reduction in mean absolute error compared t o the use of the long-term mean for the period reconstructed from tree ring data only (1580-1863) was roughly 30% for both annual and spring streamflow; the corresponding reduction in mean absolute error when m onthly precipitation values were included was roughly 60%. The reconst ruction procedures were noted to produce a negative bias due to the po sitive skewness of the streamflow values. Procedures to correct for th is bias and restore the variance of the streamflow time series are des cribed. Reconstructed and adjusted annual and spring (February-May) st reamflows are provided for the Verde and Salt Rivers and the Tonto Cre ek. A harmonic analysis of the reconstructed and adjusted annual strea mflow time series from 1848 through 1989 shows a 70-year cycle (P-valu e > 99.5%) and a 5.2-year cycle (P-value > 99.9%) for each of the thre e gauges. Correlation coefficients between the 70-year-cycle-projected streamflow and the reconstructed and adjusted streamflow for the peri od 1589-1847 were between 14.6% and 20.5% for the three gauges, all si gnificant at P-value > 99%.