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<br />Table 4. Areas and water yields for 10% snowpack SWE increases from seeding, for existing <br />(operational) seeding targets and potential new targets. <br /> <br /> Area (km2) Aprill, 2004 Aprill, 2005 Mean Yield <br /> (Dry) Yield (Wet) Yield 04-05 (ac-ft) <br /> (ac-ft) ( ac-ft) <br />Existin2 Areas <br />Utah 12,992 128,902 294,527 211,715 <br />Colorado 17,767 240,852 499,190 370,021 <br />Total 30,759 369,754 793,717 581,736 <br />Potential Areas 13,611 217,890 352,978 285,434 <br />(All States) Total <br />Existing + 44,370 587,755 1,146,859 867,307 <br />Potential Areas <br />Total <br /> <br />It seems unlikely that two years of SNODAS data would convey the long-term <br />variance of precipitation across the Colorado River Basin, even if those two years <br />exhibited a large variation about the mean in precipitation amounts. Nevertheless, <br />SNODAS SWEs at the 16 Basin SNOTEL locations (see previous section) were <br />compared to the 30-year (1971-2000) SNOTEL SWE averages. The 2004 SNODAS <br />SWE mean for all sites was 12.5 inches and the 2005 mean 20.5 inches. The 30-year <br />average SNOTEL SWE for the sites is 17.9 inches, intermediate to the SNODAS SWE <br />for the two years, and close to their mean of 16.5 inches. This calculation lends <br />confidence that the target area-integrated means of the two-year SNODAS data represent <br />a climatologically average year. These means are presented in the right-most column of <br />Table 4. <br /> <br />It is instructive to compare these means with those of Table 1. The wet year <br />(2005) is close to the Stanford Research and Twelve Basin liberal figures, whereas the <br />mean is very close to the Twelve Basin conservative value. Using half of the Stanford <br />figures again, that report states that "One year out of three, it [the yield] might be either <br />lower than 550,000 or higher than 1,800,000 acre-feet." The dry snow accumulation year <br />ending April 1, 2004 is very close to the low figure of the Stanford study. The high <br />figure of that study seems optimistic, especially since both Colorado and Utah suspend <br />seeding operations when snowpack SWE exceeds certain percentages of normal. If one <br />attempts to account for seasonal snowmelt (see previous section), the mean yield at lower <br />right of Table 4 might be near 1 million acre-feet. This figure is close to that from the <br />Stanford study and is intermediate to the conservative and liberal Twelve Basin values. <br />This amount of water is significant for the Colorado River basin water balance; for <br />example, it is two-thirds of the 1.5 million acre-feet of the river's annual flow that is <br />legally obligated to Mexico. <br /> <br />These values should be considered approximate. Since they compare favorably to <br />the estimates of two earlier studies, however, we have more confidence in them. There <br />are many variables in determining the effectiveness of seeding, which could lead to <br />substantial deviations from the assumed 10% augmentation used herein. Besides the <br /> <br />7 <br />