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<br />Heather 1:Jgdificci,ti2i'
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<br />Ac"ci vi L,:i_(~f:)
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<br />The activities ir.'!olved in setti:"i"0 EP the eel.orado [,ivel- Basin
<br />Pilot P:-oject and the results of tte fin;1; t\,/O YCi-lTS::>i' op3:'ations
<br />are described in the 1970, 1971, and 19,/2 A~'nu9,l ;?eports of the
<br />Colorado River Board. T!'.'~s pilot proj8cc, loc3.ced in the San Juan
<br />r~ountains of south1:18ste:>:,n Colore.do, is desiGned to dej',8rmine t.he
<br />amount of additionaJ. stre3.!TIflc"c1 t!!C1.~G ca... i]<; e:<pect.:od from increasing
<br />the winter sn011lpack, the cost 0" '<;;1e cc.dcl:LtioD,:;.l ,'Jater, the bor.efits
<br />that can be expected, and the impa.ct of tr\e additi'<lilal snm'rcal::' and
<br />runoff on the envir'onment. T.he experimental area covers 1,200 squa:'e
<br />miles, is not d8nscly popnJated, and is located ,'rhere seedable storn15
<br />occur frequently 8.nd \'ll1ere mc;.ch of thc S110''1pac'': shotrs up as spring
<br />runoff into t.he CoJ.ori-ldo Ri.ver.
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<br />S!>eding ope:"ations beGan in th!> 1970-71 "linter season, following
<br />several yeQt's of equipment installa'GiOil and 'cescing. 1(0 statistically
<br />significant results WE,re obtainp.d from the first, second., and third
<br />yea:>:,s of operation. ;'ITlile nut of ,q;reat statistical sig"if::'cance, it
<br />is '1ev8rthe!.0ss interest-i;;!!; to note tHat t:le average moisture measured
<br />in sno"1 gaU[;ClS insj ci.c t,he target area ,'JaS greater than thClt meClsured
<br />outside the tarGet area. The third wi.nter season produced sno\'ls 150
<br />percent of normal, \'Ihich halted the project for six weeks.
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<br />The three "linter seasons have provided fe\'le:" days suit8ble for
<br />seeding than was al1ticipated, and the Bureau of Heclamation states
<br />th,'\t it may be necessary to extend operations for one or t-v1O addi-
<br />tional years beyond the four years originally planned in order to
<br />obtain statistically significant data.
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<br />W.ndflow and other factors are used to identify sec:daiJle stanuc,
<br />but temperatures are the critical indicat-ors. If t,he snOi'! producing
<br />portion of the cloud is vlarmer than minus 23 degrees cen:;ir:rade,
<br />seeding should produce an' increase in precipitation. Seec:El'i::; a colder
<br />cloud, however, may decrease the precipitation.
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<br />Improved forecastir:g techniqv.es '1.re 8;labling lllzteor'):'.ogjs',;-; to
<br />predic:t shifts in cloud temperaj~'E'e ,';i tll ,;reater accur<:1cy. Il'. the
<br />past there have been occ'1.5ions \'111.3n sC'2'."'ilc[; contil1.1wd after tCJTljJer-
<br />I.'.tu::-es cJrop;:Jed belo\'1 the critical 10"01 cf mi'-"FS 23 degrees c21"\tigrade.
<br />Viflich cortributed substantially t,oc-raru cl:i...ninishing the net ef:"ect of
<br />s'~ec.ing "
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<br />Aerom~t:~':;"c PesGarch~ Inc ~, of 2Cl:~"t..'1 D;:'l:"baJ."fl, Califo:i."nj.a, lias
<br />r.~tainecl for a detailed, c,6t;ical, 8'ld il'::l.epender.t ,'waluilGicn of the
<br />pr'oject, to be completed a YGiH" aft",,, t.he 3eec~in[', project ends. The
<br />P'lreau of Reclamation has 8,lso aE:ced for an assessment vf th," first
<br />t;hr38 SedGCr:s 0
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<br />A l"ece'1tly completed cH":,'i8s of experiments with the micro-
<br />crganisms ,iLich h31p li ves1;ock 2'1.d wildlL'e digest their iooo. indicate
<br />the concentratiops of silver i.odide used in Heather modification have
<br />no ef:ect on 0.i8e5tion.
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