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<br />~
<br />o
<br />OJ
<br />w
<br />
<br />Equation 2, with L = 585 cal/cmB and a Bowen Ratio (R) of
<br />-0.108, this would be equivalent to a decrease in reservoir
<br />evaporation rates of -0.07395 em/day or -26.99 cm/yr (-10.6
<br />inches/yr). At the average lake elevations for 1977-78 (1186
<br />ft), this would result in an annual reduction in water loss
<br />of 119,779 acre-feet (1.48 x 108mB). The approach used to
<br />derive this estimate is very simplified in that other varia-
<br />bles in the heat budget were not included in the calcula-
<br />tions. It was assumed that solar radiation, net radiation
<br />and change in energy storage would be similar regardless of
<br />discharge depth. As was pointed out by U.S. Bureau of Recla-
<br />mation scientists in their review of a previous report [10J,
<br />these assumptions may not be entirely valid. Extensive stud-
<br />ies will be required to determine how other variables in the
<br />heat budget will change with discharge depth. Nonetheless,
<br />j;he ostimate appears to be a reasonable approximation of
<br />waLdr loss savings based on conclusions from earlier studies
<br />on J,"ke l~ead. Harbeck et a1. [4 J made similar estimates with
<br />data collected in 1952-53 and concluded that a surface dis-
<br />charge would reduce evaporation in Lake Mead by 72,000 acre-
<br />feet (8.9 x 107mB)/yr at lake elevations of 1174 ft (358 m).
<br />This is similar to the present estimate if differences in
<br />lake elevations are taken into consideration.
<br />
<br />Table II. Net Advective Energy Estimates in Lake Mead
<br />For a Surface and Hypolimnion Discharge at
<br />Hoover Dam [5J.
<br />
<br /> Colorad<>AI..r Hoovo,P.'" la.. ~..d
<br />~\onlh Infl",,1 Dlsch.r~e Enorgy~ HypolllM.2 Eplll.....2 Ol.ch.rgo Hy""ll"".~ Surfa.e4 Surf.ce Hypoll""',OI'OO"9" Epill"",Ol"h"ge
<br /> T...p, DIscharge DI'charg" Discharge Oi5ch.rge M.. Net Ad"ot. Enern tlotM.ecl.Eoo'gy
<br /> Temp. T."p, Ene.gy E"ergy
<br /> tOe) (..3.10a) (c.lxI01b) ("c) (OC) (m)xI03) (<.1~I016) (C'1~I016) (en2xT01Z) (cat'c",-2'day") ("I_em-2'dey-1)
<br />0.. n 1).0 '" 0.447 12.0 22.) ,., 0.40J 0.949 5.J~ +2.6& -30.l0
<br />10. n 12.~l ... 0.334 U.O 20.5 ,.' 0.420 0.902 5.31 '2.64 -]2.52
<br />)ec71 lLS ,., 0.675 12.0J 16.6J ,., 0.448 D.nO 5.l5 +1;.69 -2.71
<br />Jon1S Ill.' 10.9 0.109 !l.0 12.1 ,., o.no 0.2~1 5.~6 +28.89 +1.65
<br />f,'b78 11.0 ,.' 0.1069 11.0 11., '., O.~03 0.~19 5.50 .~.19 +2.60
<br />';,,'8 11.0' ,., 0.701 12.1 16.~ ,., 0.101 I.on 5.55 +0.35 -n,'8
<br />","18 1).0 ,., 0.507 11.7 15.1 n.l 0.810 1.188 5.46 -18.50 -~1 .5f:
<br />loy1S 12.03 .., 0.514 12.0 19.) 10.6 0.80fi 1.519 5.~6 -16.H -62.33
<br />Jun78 11.0 ,., o.MIo II.] n.n .., 0.6~O I .~16 5.4~ -1.59 -1'9.57
<br />'"' " 15.8 ... 1.072 11.0 17.0 10.3 /).783 2.)18 5.)6 >17.39 -75.59
<br />""178 I~ .1 1].2 1.360 n.o 24.8 11.0 0.636 2.2~~ 5.31 +]1.106 -53.10
<br />Sep76 110.1 11.5 1.288 11.3 21.5 .., 0.~90 loin 5.~1 ~ ~
<br /> +9.M" -29.55'
<br /> ^Ave'aqo
<br />
<br />Ilnfl"", ''''''pe,atu'e - (T +1.600 _ 0.010 (T) _ (2.1 n 10-5 nq)
<br />
<br />201 'o~",go temper.tuee. aC~ the l~~e Ilead te<-'p<catu,"' at .O<h depth
<br />pf dl.cha,ge ne.r tno Hoovee D." ;n<a~e teMe". la~e Heod .",f..o
<br />'"0 hy~ll"",lo" (90..) te~P.cot"'e' fe"," U~lV dH'.
<br />
<br />Whe'. 1 ond q oce Crond ~onyon to,.".'Mu'o
<br />I"OC.nd.....ndi.O"Mg. ,nC,S (>Iarb.tk
<br />...1. 1958}. OrondCMyon'.mperotu,o
<br />fr.,,-. USOS data.
<br />
<br />'Avo'ogeof p'ecodlngO"d fOllo..lng""'Mh,.
<br />
<br />4Ad..cted .""rgy C""'pu"o rde'Me. 4.4"~.
<br />
<br />12
<br />
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