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<br />The Rocky Mountain National Park location had its nearest generator 17 miles to the <br />south-southwest, with no others within 20 miles. However, that intended control site received <br />some limited seeding silver with a concentration of 17.2. Only one target location had a higher <br />value. Figure I shows that several generators were within about 35 miles of the Rocky Mountain <br />sampling site (0.5 deg of latitude = 34.5 statute miles), a.'1d south to southwest of it. But some <br />AgI was apparently transported north and east to the Rocky Mountain site, located at 9180 it, <br />somewhat lower than the other control sites. Transport would have been necessary up the valley <br />containing US Highway 34, which is wider than the valley approaching Willow Creek Pass. It is <br />not known if such airflow occurred during storms, or in-between storms for cases with extended <br />low-level trapping. While Ag levels were relatively high at this intended control site, indicating <br />mistargeting or contamination, three of the target locations provided additional "control" values <br />since their Ag concentrations were no higher than about 3 ppt. <br /> <br />5.0 DISCUSSION <br /> <br />5.1 Estimation of Expected Ag Levels in the Snow pack <br /> <br />Examination of the generator network on Figure 1 suggests a typical spacing between <br />units in the 5-10 mile range, which could result in large gaps between adjacent AgI plumes. <br />However, at least for northwesterly and southeasterly flows, generators were sited at various <br />upwind distances. This should allow eventual merging of many plumes. But most of the target <br />had only a limited number of units, and wide spacing between them, for southwest flow. The <br />southern target portion had a similar situation for westerly flow. But with the wide range of <br />storm wind directions over the course of a winter, it seems unlikely that most target snow <br />samples would fail to have obvious silver enhancement because of generator spacing alone. Two <br />other factors must be considered. As discussed in Section 2 and also below, frequent trapping or <br />mistargeting of AgI plumes have been a serious problem for many programs. But the overall Ag <br />output wiJI be discussed first. <br /> <br />It is conceivable that inadequate AgI was released during the 2002/03 winter to enhance <br />the silver content of the snowpack appreciably. The authors are unaware of the AgI output of <br />Western Weather's generators, or of the average number of hours the generators were operated. <br />However, similar generators are known to output about 25 g h-I of AgI or about 12.5 g h" of Ag. <br />Assuming an average winter usage of 200 hours for the 43 generators yields a total seasonal <br />output of 1.1 X 105 g of Ag. This may be an underestimate because several additional generators <br />were operated for other projects, which could have affected the DWB target. <br /> <br />The precise area of the intended target is unknown, as is the actual targeted area, but the <br />former can be crudely estimated as about the area that would fill two of the 0.5 deg latitude X 0.5 <br />deg longitude rectangles of Figure 1. That is equivalent to 4.7 X 1013 cm2 (1,840 mi2). <br />Reference to a number of SNOTEL stations suggested the April 1, 2003, snowpack water <br />equivalent was about 50 em (19.7 inch) resulting in an estimated total water volume of 2.4 X <br />1015 cm3 (1.94 X 106 acre-feet) for the target area. Since a em3 of water is equivalent to a <br />milliliter (ml), dividing the total emitted Ag by the target area water volume on April 1st results <br /> <br />22 <br /> <br /> <br />