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Orj~"l '-J ......_~ -.. .. f / \ Figure IS. Map showing location of the 121 tree ring sites used in drought analyses. Figure 16a. Time series plot of regional-average tree-ring index for West and Southwest regions for the period A.D. 1600-1800. Horizontal line marks the value of tree-ring index exceeded 80% of the time over 363 years (A.D. 1600-1962) Figure 16b. Same as 16a but covering the period A.D. 1800-1962. Figure 17a. Same as 16a except for cell-averages rather than regional-average tree- ring indices. Cell R7 (Top) is located in central California (see Figure 14) and N7 (Bottom) in nonh-central New Mexico and south-central Colorado. Figure 17b. Same as 17a but covering period A.D. 1800-1962. ( Figure 18. Map showing severity of drought by individual cells in ye:lJ' 1670 (Topi and 1843 (Boltom). Filled circles indicate cell-average cree-ring indices with following exceedance possibilities: 0.99 < r extremely dry; 0.95 < r < = 0.99 very dry; 0.80 < r < = 0.95 dry; r < 0.50 wetter than normal; r < 0.05 very wet. Cells left blank are drier (lower index) than the median value but nO[ the 80% exceedance probability as a drought threshold. Solid black cells contain no tree ring data. ( Figure 19. Twenty-year moving averages of reconstrUcted annual flow for the Colorado River at Lee Ferry, AZ (top), and the Four Rivers Index of California. Data are plotted at the beginning year of each 20-year period. Original annual values were taken from appendixes in Stockton and Jacoby (1976) and Earle and Fritts (1986). Figure 20. Non-overlapping ten-year means of reconstrUcted and actual annual namral flow for the Colorado River at Lee Ferry, Arizona. Beginning years of each 20-year period are listed along the abscissa. Actual data are from the U.S. Bureau of Reclamation (unpublished); annual reconstrUcted values are from Stockton and Jacoby (1976). v