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<br />eatcgories: I) addition of different types or greater numbcrs of sceding equipment and amount of <br />secding. and 2) extension of seasonal opcrational pcriods. <br /> <br />There are sevcral possibilities under the first catcgory. Ilerhaps the addition of higher <br />elevation. remotcly-controlled silver iodide generators would be desirable. Additional ground <br />generators may be added to an existing program if the spacing bet\veen generators is not <br />sufficiently close to produce consistently overlapping seeding plumes in the seedable cloud <br />regions. <br /> <br />lllC addition of one or more sceding aircraft may be appropriate. although this decision is <br />drivcn by the characteristics of the individual target areas. If there are mountain ranges up\'..-ind <br />of the existing target areas. this may mean that aircraft cannot be Ilo\vn low enough in order for <br />the sceding material to enter the desired cloud rcgions. which are typically found at 100v <br />elevations on the windward sides of the target barriers. Two areas that may benefit from the <br />addition of seeding aircraft arc the San Juan Mountains of southwestcrn Colorado and thc south <br />slope of the Uinta Mountains of northeastern Utah. There are no major upwind barriers that <br />could prcsent safety considcrations for thcse t\VO areas and both .lreas gcnerate considerable <br />runoff. <br /> <br />Some programs. due to funding constraints. may be unable to operatc for thc cntire winter <br />season. Such programs will be typically opcrated during thc "best'" period bascd upon <br />climatology. For example. a program may be currently opcrating from Dcecmber through March. <br />Additional prccipitation could probably be produccd ifthc program \'ias expanded to operate <br />during the months of October. November and April provided that suitable conditions (e.g.. <br />tempcratures and presence of supercooled liquid water) exist for signilicant durations during <br />these months. <br /> <br />(2.0 Potential Impacts during nl")., Normal and \Vet Winters <br /> <br />A question that is asked rather frequcntly is "\Vhat arc the potential effects of cloud <br />sceding in dry. nonllal. and wct years?" This question is often asked during a drought pcriod that <br />is affecting a given area. This is certainly a legitimate qucstion. Those \'..-ho have sufficient <br />knowledge of cloud seeding will not advocate the technology as one that is going to "bust'" or <br />"solvc" the drought problem. Our currcnt ability to modify the weathcr is dcpendent upon having <br />the right types of clouds occurring naturally. Studics of clouds during drought vcrsus non- <br />drought pcriods typically indicatc that the clouds during thc two periods arc quite similar. <br />During drought periods. however. such clouds occur less frequcntly than in nonnal or wct <br />periods. So while it may be possiblc to produce incrcases in precipitation of approximately 10% <br />in dry. normal and wet periods thc actualmagnitudc ofaccumulatcd seasonal increases from <br />sceding would be reduced during drought pcriods. This fact has \cd some to statc. perhaps <br />justiliably. that"a 10% increase of nothing is nothing:' This attitude may be some\" hat extrcme. <br />howevcr. if the value of the water during drought periods is taken into account. Interestingly. <br />there is a suggestion in one long-tcrm program being conducted by North American Weather <br />Consultants in ccntral and southcrn Utah that the seeding increases expressed as a percentage <br />may be higher in below normal winters. It is probably safc to concludc that the "biggest bang for <br />the buck" from cloud sceding programs will occur during nonnal to wet water ycars. The <br />