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W05415 WOODHOUSE ET AL.: UPDATED COLORADO RIVER RECONSTRUCTIONS W05415 Table 7. Ranked Subbasin Flows During Lowest 5-year. 10-year, and 20-year Moving Averages of Reconstmcted Flow at Lees Ferrya 5-year Average 10-year Average 20-year Average Lees Rank 5 year GR Rank CC Rank SJ Rank 10 year GR Rank CC Rank SJ Rank 20 year GR Rank CC Rank SJ Rank " I 1848 I , 17 1631 71 6 3 1592 6 1 48 -, 2 1626 63 2 1 1782 9 8 17 1593 7 2 82 3 1847 8 8 9 1592 5 3 57 1641 57 ]4 13 4 1846 3 12 54 1632 40 1 2 ]889 2 9 5 5 1759 24 16 29 178] II 9 ]2 ]598 3 3 97 6 1686 11 6 22 1593 I 7 92 1890 1 15 20 7 1584 ]6 I 8 1883 -, 25 4 1671 13 16 45 8 1883 7 36 2 1737 43 10 16 1638 52 55 28 9 1668 2 13 44 1879 4 26 18 ]639 66 57 25 10 1902 10 5 3 1880 2 18 24 1640 77 64 21 "The ending years of the 10 lowest-flow periods at Lees Ferry are listed under "5 year," "10 year," and "20 year." Subbasin gauges are Green River at Green River (GR). Colorado near Cisco (CC), and San Juan near Bluff (SJ). tercile. However, in four of the eight periods when Green River is low and the San Juan river is high, flow at Lees Ferry is in the driest tercile, and except for one of the eight periods, Lees Ferry flow is lower than the median. This suggests that low-flow conditions in the Green River can override wet conditions in the San Juan, and to some extent, moderate conditions in the Colorado-Cisco, to influence Lees Ferry flows. Greater sensitivity of Lees Ferry flow to a. Colorado at Lees Ferry, AZ 2 ~ 4 m 8 .,:, 16 "C 32 .g 64 Q) 128 l1. 256 1600 1800 1900 1700 c. Colorado near Cisco, UT 2 Iii 4 ... m 8 ~ 16 "C 32 o 't: 64 :. 128 256 1600 1700 1800 Year AD I I o 5 1900 the Green than to the San Juan is of course expected, given the much larger percentage of flow contribution from the Green (Tables 1 and 6). [35] As shown in the spectral analysis (section 4.1), streamflow at Lees Ferry and the three subbasins also varies significantly over multidecadal timescales. To highlight this lower-frequency variability, each of the reconstructions was smoothed with a SO-year cubic spline (Figure 9). The b. Green at Green River, UT 2 4 8 16 32 64 128 256 2000 1600 1700 1800 1900 2000 d. San Juan near Bluff, UT 2 4 J" 8 16 32 64 128 256 2000 1600 1700 1800 Year AD 1900 2000 1.'8~Jl;';lfiil!7~'~tJli'!t' 25 50 75 % Total Wavelet Power Figure 8. Wavelet power spectra ofreconstmcted flows for (a) the Colorado River at Lee's Ferry, Utah, (b) Green River at Green River, Utah, (c) Colorado River near Cisco, Utah, and (d) San Juan River near Bluff, Utah. A derivative of the Gaussian wavelet ("Mexican Hat"; see Torrence and Compo [1998]) was used under red noise assumptions, and each reconstruction was padded with zeros to avoid wraparound effects. Black contours in the power spectra represent the 95% confidence level compared to red noise. The cone-shaped net shows portions of the spectrum where power may be reduced through the effects of zero padding [Torrence and Compo, 1998]. All spectra cover the common period from IS69 to 1997. 10 of 16