|
<br />f'lt. "~o
<br />
<br />.
<br />
<br />lhe md!l:e\ III muludCI.:adal dmlatl'
<br />variabillt). ahhough In a cllmplc:l way.
<br />From an interannual pcr..p.:clivc, t1lge
<br />l100ds and high runllff volumcs lypicall:.
<br />I'll,:cur during \Imng EI Nino conditions,
<br />whereas La :\ina l"oOlhlions Iyp!l:all)
<br />caus.c ]ow-l1ow nmdllion.. (Wehh and
<br />Betancourt. 14"12). Ikrcf.)rd and others
<br />(2002) show...d Ihat precipitalion on Ihe
<br />Colorado P]at...au IS relaled to both Ihe
<br />SOl and POO lOdices. Olher slali\lical
<br />analyses shoy, Ihat 110y,.. in Ihe ri\er
<br />Iln]y can Ix> panially e\pla1l11'd h~' the
<br />PDO (Hjdalgo and Dmcup. :!otJ..I). Our
<br />ahllil) 10 prcdi\:t "'ah.'r re",lurl'C\ in lhl'
<br />COI(lrad.1 River ha....in rcmalOS poor.
<br />^.. ,hown in Figure.t. \aria!lilit) In
<br />now of the Cnlorado Ri\er i" a I.:nmpk:l
<br />resf'll1\,,"e tll !loth the A....10 and PDO.
<br />Abu"...-a"eragc iloilo'S reliahly OCl.:ur when
<br />the AMO lmk\ 1\ negall\e and Ihe PDO
<br />index is belw...en --0.5 and +0.5. Below-
<br />a\erage Ilow, gt.'n...ral1) o\:I.:ur when the
<br />AMO is positiw (Fig. .t). The deepest
<br />dfLlughls app..'af stmngly relaled loa range
<br />in A!\lO index from -1.0 10 +1,0 lmo,,"lly
<br />from 0 10 + 1.0) and a PDO indn of
<br />apprm:im,lIdy ...{j.5. Figure -I un.kr\.t:Ufes
<br />Ihl' l'onl'epl Ih<ll dwughl re"ull.. fwm a
<br />o:-ompk:r.. "0:-1 of ehnl<llOlogil"a] fador"
<br />Ih:!t arc not ea.\ily prl'dKted oc e:lplained
<br />The y,ah.'r..hed nl Ihe ('nlocad,) River
<br />span" a larg... la1lludlllal range. and
<br />pre..:ipu3linn pallenh owr th<ll gradi..:nl
<br />do nOI r"'''f'llnd in t:on..:ert to {l'gltlna] ,IOd
<br />h,n mullid.....:adal dim<llil.: nuduatilln....
<br />AtlIlVc-awrag... runoll 10 part 01 the
<br />watt.'rsh...d (t'.~., the Ilonh..:rn half) may
<br />OWrCllllll' Iny,. runoff in lllhl'r pans (~.~..
<br />th... southcrn half! dunng S"l1Il' drought...
<br />For l'xample. thl' mld-n'ntury droughl.
<br />whi..:h y, a." ,.......'cre Ulllhl' Colorado PI;ltcau,
<br />..:.lUsedl11l1) \hghll),ht.'low-a\l'(;lgerunpll
<br />in the entire ha"in: Ihe awraf": rum'lI
<br />\'nlum..: during thIS periull wa.. I] I MAE
<br />Similar]y, Ihe ...arl\' 20'. century l!rought
<br />IFig, .lDl had an ;\...r.lg... runnif \(,Ium..:
<br />of \J.b ~1"\F. As a result. mUl.:h of th..:
<br />variahihl) III Ih... annual /low r"'l"\,rd
<br />(Fig. _'E-F) IS n,)1 ...a..i1y ""plainl'd hy
<br />the PDO and 1\~IO IIIdil-..... de"Plle some
<br />compdling graphit:al rdatil'"" (Fig. ..U,
<br />
<br />Dendrochronology and
<br />Colorado River Flows
<br />
<br />Tn:...-nng renlll...lrUl'lll'n" l.f COILlC<lJO
<br />Ri\er Illms pW\ldl' J IOIl1!-l'f-l..:rm nO"
<br />n~":I'rd Ih<ll ..:an ht.' u.....:d III a............' t1wught
<br />frctlu...n..:) Onl' 01 Ihe 1l111...t IIllpprtant
<br />cpndUSIOIl\ Ifllm .kndnxhrnnnlog) IS
<br />that Ih... po:mll! from j911tlthwugh 1l)~O.
<br />y,hiL'h ....a\ p<lnlan~' U'l"ll tL' dl'tcrmim'
<br />11.)w allo,:all('ns under Ih... Col,'rado River
<br />COffiP'll.:I. v.a..Ii\..c1) the hIgh....., p.:ri.ltJ of
<br />rumln 10 -150 )l';JP.; (Stl>t:\..ilm and j:]cooy.
<br />
<br />147tl). ThIS 'iugge\ts that Ih... mo..t
<br />unu..ual a"pcel of Colorado River runoff
<br />during the 20""cenluf} b th... high runoff
<br />\nlume 10 \:ertalO flt.'rilld.. (19flf,-1920.
<br />19!1.l-19K5), not the drought f'l'rilld....
<br />The de<:ade wilh the low,,"SI annual 110V0
<br />volume (averaging ahoul 9.71 ~IAFl
<br />fCt:onstrul.:led u..ing denJm..:hrouolllg)
<br />IlCI.:uITcd from AD. 15K4-159.\ (~tckll
<br />and others. 19(5). For comparison. Ihe
<br />1O-)ear pcnod of IW5 thwugh 200-1
<br />(2lX)..\ i.. a predi...-t...d volume) produces an
<br />average annual noY, volum... of 9.9 T\1AF
<br />lnol COIT..:..:leJ for up\trcalll di\'CrSlOn.. or
<br />II\C). Sirllllarly.the IL",.t,..1 5-ycar a~...rJge
<br />u..mg Ire... nng.. i\ 8.R-I MAF (AD. l'il)()-
<br />15')-1), l"llmpared '" lIh 7. II MAF lrom
<br />14W lhrnugh 200, The...... compari..on..
<br />~lIggc~t thaI lhe l'UITent drought may
<br />he ":ompar.lhlc 10 or lllor... "c\erc than
<br />Ihe large\t.knnv.n drnught in 50U )ears.
<br />The wid... range of prcdi(ljnns of the
<br />pcrsi\lenCC oflhe currell! drought retlct:t
<br />Ihe plltlr e'planalilln of pa.SI COlllr<lJI)
<br />RI\W l!ows u..ing dim<lti..: IOdit:cs. If
<br />Ihe primaf)' contro] on droughl in the
<br />Colorado River hasin i.. the A!\IO. Iht'n
<br />drnughl l'unJilion" might omlinul' fur
<br />"cv..:r.ll decades Ilwing tu the p..:r\l"lelll.:C
<br />1'1' SST ",arming 111 the AIlanlK (k..:an
<br />(\1cCahc and nlh..:r... :!OO.l). Simd;u
<br />argullll'lIh arc !l.bet! on pt.'rsi...lent:e Ill'
<br />thl' 1'00. although thl\ mJe:l IS I.:uITenlly
<br />posiliw (Fig. 3R), which suggC\IS ,hat
<br />a return III n\lrmal or ahtnc-avcr3ge
<br />Cl>ndilinn.. may be Il11mml'nl. A\
<br />indl..:alcd hy Ih... tree-nng re..:tlll~trudl"n\.
<br />droughts ..ddom f'l'rsisl for longer th,1O
<br />a de..:ad.... anll if thaI n'm.lln.. th..: I.:a\e,
<br />lhl' CUITent drought i" unly half o\'cr.
<br />
<br />Robt'rr /I. \~'t-bh. (;reROI)
<br />Ridlllrd lIneffw/. II/lfl
<br />Will.mnke
<br />
<br />J. -'keflhe,
<br />Chri,"(I'I,/if'r
<br />
<br />.
<br />1.5
<br />
<br />1.0
<br />
<br />.,.
<br />"... .
<br />_..~
<br />(...~'"
<br />
<br />Selected References
<br />
<br />C.l~Jn. UR. Redmund. t\T.. RidJle. L.G..
<br />1t)Qtj. E:-':SO Jnd h)dn,l"j:lc ,.~1rt:mcs III
<br />the "'o:~to:rn UnlledSlate,,; J Chm;ue 12
<br />2l'l~1-2lj').1.
<br />Enho:ld. UR. \k~la,.!\':ufief. :\.\1. Jnd
<br />Tnmlllc. P J. 2001. lllc :\!lamie
<br />mulw,J.,'I,.'adal .'......ll1all('" anti Il~ rrlmllln
<br />tll 1"3101311 .11Id nH:r 11."",,, 111 lhe
<br />l'onlm,'nl;.Il11 S Ge(lph~ ". Rc" LO:I..!S
<br />.!1)77.1(l~1l
<br />Ikrd"ru. K. Wellll. R II. and Grah~m.
<br />S, .:!OO.!, Prl'cipllJlltln hl'lO~ uf the
<br />C..]"raw PIJh:au rl'gh'n. 1900-.:!1J(M)
<br />U.S, Gn.] Sun. b.:t Shet'l IIQ.Ol.~ p.
<br />Ihd31go, 11 G. and Dra..:up. lA. 100,1,
<br />E\'IJen,',' l11 lhc ,lgll.lturl' "f :-':,mh
<br />Paclric mull1Jo,'1;.ldal pTl.....e~><:' un
<br />rreopllalll'n Jnd <lreamfl"" 'analllms
<br />to tnc uprcr C"l.'raoo R1\cr t-ao;tO. '"
<br />
<br />.
<br />B 0.5
<br />,
<br />~
<br />.
<br />o
<br />g
<br />~
<br />
<br />00
<br />
<br />.0.5
<br />
<br />-1.0
<br />
<br />.
<br />
<br />.1.5
<br />-1.5 ~ 1.0 .0.5 0.0 0.5 1.0 1.5
<br />AMO Dt>pilrturt>
<br />
<br />.1.0 0,0 1.0
<br />Anfluill Flow.Volumt> Dt'parturt>
<br />F>gure 4. Graph shoWing above and below
<br />average Cololado Rlverllows compared With ltla
<br />AtlaotlC Decadal Oscillation (AMO) and PacifIC
<br />Oecadal OscIllation (POOl. Flow magmtudes
<br />are IndICated by Clrcle COlOr and dlametel.
<br />
<br />Van Rlpn. C. III , arnIC,']e, K.L It'd...).
<br />The Colorad.. I'lareau: TUCS<lO. Unll'.
<br />Ant. Press. p. 257-265,
<br />LaRue. EC.. 11125. Wall'r power and 11000.1
<br />contn.l of CI,lora.t.> RI\'er hel"w Grcen
<br />Rl~cr. l"tah: tJ S Go:o! Sun' Water-
<br />Supplyl'apcr55h.17/ip
<br />\1JntU,I. :'oIJ" anJ Ilan:. SR,. 1002, The
<br />P3":lfi.: Jc.::a.I.\! 1""lllalhm: J (kcan 58:
<br />.15-12:.
<br />\kCat-.e. OJ.. Paled,l. \1,:\., ;lnd Iklan'::OUI1.
<br />JI.. 21)(~. l'a,'llil' .lOd :\llanllt' O":l'an
<br />IOtlucncc, "n mutlidL'l'adal dltlllghl
<br />Ire'lucnc~ to the l'mted St.\les; Prot:'.
<br />1\al.. A.:~J. Sci. 101. -I 1.~Ii-~ I~ I
<br />\kku, n.\L Slocktun, C.W.. and H(l~j:e~'.
<br />WR.. ['N5. Thc lree-nnj: rcnnJ 01
<br />","wee <u,lalOcJ Jmu!!ht: Water Rc".
<br />Rull. .11 71N-1I01
<br />:-':all"n31 O..:eanic anJ :\lmnspheril'
<br />AJmmlo;lrall"n. 2i)1~. ",v.wl.ncdc.lHMa.
<br />go,"/puNd:lIa/Clr<JJnNo-h rd"l.l\t
<br />S,'huhcn. S n.. Sum.'i. \l.J, P('glnn. PJ,
<br />Kmler, R n. and H;ICmel\ler. J.T.. 200.1.
<br />On the e<lU<C 1,1 lilt.. I <J1(k UU" Hoy, I-
<br />Sncon' ,1)1 1l'l~"i.JS~'1
<br />SIC\loan. IT. ('a~"n, n 1(" ;IIlJ [leulng...r.
<br />\1 D.. .!t.M)4.Change~ In 'lHrnmdt runoff
<br />111ll1llj: In \loC'lem ~"nh .-\merKa under
<br />a 'NJ"I!1C'" <li u"uaJ' chmalc .::hang"
<br />..,'enann: ('JI1I1al1.: Change. \. O.!. p.
<br />117..!.12.
<br />Stnd,I"n. CW and Ja"I*,~. G.c.. Jr.. 1970.
<br />L..n~-to:rm ..url31.:c-water ~lIrrl) and
<br />_lre3fTlfl<l\I, ITcnd~ m the upper Colnrado
<br />R",'r Il'Nn t't;I"f"ti on tr,'c-ring anJ.I~<t:\:
<br />Lalo: P"y,cl1 Rc, I'rtlJ' Hull. ;.o;n. IS. 71lp.
<br />\\etm, R 1\. and Hetanwun, J L. 1'N2.
<br />Chmdll, \Mlat'ttlU)' and IJ".>d
<br />In'IIWIlt..) <>1 th.: S.lnla eruf Rlle'r.
<br />PunJ ('ount). AMmnd: U.S Geol,
<br />Sun, WJlcr-Surrl~ P~pcl 1.17Q. ~o r
<br />
<br />@-......."""'.......
<br />
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