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<br />time observations of SL W, using icing rate meters and radiometers. Rapid response seeding ~an be done <br />with remote-controlled generators. <br /> <br />The previous discussion concerning total SL W flux per storm episode may give the impression that the <br />only periods worth seeding have large amounts of vertically integrated SL W. In fact, Super and Boe <br />(1988) examined the 2 mo of hourly (not storm total) microwave radiometer data from the Mogollon Rim <br />to show that 44 pet of the total flux for the season was due to the 81 pet of all hours with mean cloud <br />liquid water amounts of only 0.15 mm or less. Their study also showed that the 5 pct of all hours with <br />liquid amounts in excess of Q.3 5 mm yielded almost 30 pet of the total flux. Similar results were shown <br />for the Grand Mesa (Boe and Super 1986). These studies suggest that seeding may be appropriate both <br />when SL W is abundant and when it is limited. Hours with large SL W amounts produce significant flux <br />but are relatively rare. The numerous hours with small SL W amounts also produce significant flux over <br />an entire winter. <br /> <br />8.9. Super,A. B., and J. T. McPartland, 1993: Preliminary estimates of increased runoff from <br />additional high elevation snowfall in the Upper Colorado River Basin. J. Weather Modification, 25, <br />74-81. <br /> <br />ABSTRACT <br /> <br />"" <br /> <br />Evaluations of winter orographic cloud seeding projects often have been based on precipitation because of <br />difficulties associated with evaluation by stream flow at many locations. But most sponsors are primarily <br />interested in the amount of additional streamflow that might be expected from successful cloud seeding. <br />Preliminary estimates have been made of the percentage increases in streamflow that might result from <br />increased snow water equivalent in the Upper Colorado River Basin. This was done by fitting linear <br />regression equations to paired streamflow and snow water equivalent observations from several mountain <br />watersheds for which streamflow was not significantly affected by transbasin diversions or upstream <br />regulation of flows. The regression equations were used to predict percentage seasonal and annual <br />streamflow enhancements for a 10 pet increase in mean April 1 snow water equivalent. <br /> <br />Predicted seasonal streamflow increases ranged from 6 to 21 pet, with most drainages estimated to have <br />10 pet or more additional runoff. Possible reasons for differences in predicted streamflow are discussed. <br />The reasons include snow water equivalent measurements that are unrepresentative of the watersheds, <br />variations in geology and vegetation, and drainage slope and aspect which affect incoming solar radiation. <br />It is suggested that as cloud seeding technology improves, more attention should be given to targeting <br />areas that maximize streamflow enhancement. <br /> <br />SUMMARY <br /> <br />This study estimated the percentage increases in runoff that might be expected from 10 pet snowpack <br />increases in unregulated mountain watersheds in the Upper Colorado River Basin. April 1 SWE data <br />collected by the SCS were used together with GS stream gauge observations to develop snowpack-runoff <br />relationships for 16 individual drainages. Observations from two small experimental watersheds were <br />also used to develop linear regression equations between streamflow and near-maximum SWE. These <br />relationships ~ere used to estimate the percentage increase in runoff predicted for a 10 pct increase in <br />snow accumulation during a mean season. <br /> <br />49 <br /> <br />