WMOD00002

• Applicant: Western Weather Consultants
• Project Name: San Juan
• Date: 11/1/1984
• Weather Modification - Doc Type: Application

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.'n..... ...J..-''',A,'fr.:.. f: S.h..... C,,~Aro<..._~~+ . b7 L,,",~ t..,; l..)<.i!.;j b<....t;""r - 197y
2. At'glll('lIIillg ,he CP!c'l"{u/o Uil'i.'r by WQSA

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During winter in lh<: Uppl..'r Color:1do Ri\'<:r B:1sin. supt:rcookd clouds
~He f..mned o\"er the higher ek\';l1ions a~ llloisl air is forced by strong wind~
over Ihe major mountain masses. Under ct:rlain favorabk conditions as sum-
marized below. the prccipil;ltion that would occur natur:lll\' from these clouds
can be increased bv seedin~ with silver iodide smoke. The air mass must have a
high moisture contcnt. nnd the cloud. including ils upper boundary. should
be warmer thall - 20QC, The component of mrtlow perpendicular 10 the moun-
.tain rid~c must be rdatively' st-ron~. ~nd it must be possible to disperse stiver
iodide :Jrtides within the cloud in a pro riate numbers to serve as ice crystal
"nuclei." Silver iodidc sllloke from ereund-based !!enerators must e I use
by turbulence and lifted by airllO\: into cloud r~gions th:lt arc colde(' than
_IOoC. The ice erysuds formed mllst have lime 10 grow to a siz\: thai will fall
to carth before re:1chin,g the downdr:1flS that cxist on the br sid~ of the moun-
tain.
An operntion.al cltlUJ seeding system was postul:ued based on the tech.
nical det:1ils of these proCl'.<is<:s. Thc system consisls of et:ntralized mana~cm....nl
control. evaluation. :lnt! puhlil.: service funclions. with t:lrget area operalional
srrvices and maint....nance di:;tricls to el)\'Cr:l1l of the potentially useful seeding
. Sm~lI rarti\:l<'~ ~bou: ,,'hi,,!': i..:c nY'.I;,1 ftJrnl;lli"n ;Ind growth l..kcs pl:!c\:'.

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areas in the Upp..:r ColoraJo Basin. This system is eXfXeteJ 10 have J.n :lVerJ.ge
annuJI direct cost of 55.4 million for all of the potential larget areas in the
Upper Bnsin.
The postulated system is not expected to be made obsolete rapidly by
technologic:)J developments. M<ljor ch:mgcs <lre not expecred in ground.bMed
cloud seeding equipment in the near future but rather in the contrel and moni-
toring of cloud seeding operations. A mnjor improvement in meteorologicnl
information important 10 cloud seeding will be provided by the introouction
of improved weather and earth resources satellites.
As \VQSA rechnolo~y would he applied at the present time to the Upper
Colorado River Basin. the moSI probable lom~-teml aver:u~e increase in snow-
fall al devaliom; nhovc 8.000 feet that could be realized is in Ihe r:m~~ of 20
to 25 percent. The increrlSl.'S arc roduced mainl b chan2in hours in which
little snowfa I would h:lve occurred into periods of significant snow a1. n-
creases In snowfall were estlll1:lled by uSing hlstoncal data oblalned from The
U.s. Geological Survey and (he National Weather Service along with current
understanding of the physical phenomena associated with cloud seeding. These
cstim3tes were verified for three loc:nions in the Basin b:tscd on :t wintcroro:-
~phic cloud seeding model :tJevelopcd by Colorado Stolle University and da~
_p~ccipitation and upper air data for nine winter seasons beginning in 1951.
T"~~ estimatcd average mcrease In preCIpItatIon vanes from 25 percent In tne
sout~~~"I!...p'art of Ihe UaSlll to 15 percent m the northern and e:Jstern t:Jrg~.
~. Applying these faclors and Ihe :Jppropriale factors for converting cumu-
!ative prccipiGlion 10 streamflow to each part of Ihe Basin. it was found that an
augmented snow mell runolf of about 2.3 million acre feet could be produced
in.:J norm::l! yc:!r. TJlI.'t would vary Irom about l.l i\-bl In a low w.:Jter or (J,\;
year to 3.6 ~n a high wntcr or wet year. Since the elTects of the w<5SA
system would nOI be conlinedlo the Upper Basin. 0.5. 1.2. and 1.9 Maf could
be e.'(pccted in }'c:lrs eonsiLlered 10 produce low. normal. :Jnd high amouOls
of runoff from the WOSA precipitation Ihal falls outside Ihe Basin. (This
oUI-of-basin component could be increased by a change in system dcsi,gn.)
T!'C corres mdin~ normal ~'e:lr direcI cost 'r acre-foot is $2.37 far in-basin
~l!~~'J nnd S 1.51i f'lr 101:11 rlllllllf. The direct cost for producln~ \\'0 A water
i:~~k:~.~~I~~I~_~~~~~"r....:~~..v~cr rractical lIJ.:ans for producing. or bringinc: n('\~'
waf..:r intn lh~' ll:l~ill. II i~ ;d,,' ks<; than the Cll"t of mnsl means flro-~~f -lor

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