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<br />
<br />I~ nraNl/lfu ~ an IInrm1[ 0 COlllro p OtJ J f('fllII'" fg
<br />ifislribu,,.lo'"}:,. amm"," uj.\und in/tl roJi~ and rdui/d ("rimed Joni'
<br />ian bu cn'licullJbject;l~ of rnearch and fnf.miloring in llr, Co/f/rad3
<br />, .
<br />Ril,t!T ('clJJ)"Jlem. dmnuueumfrom Glen Canyon Dum Aggradation
<br />~f !outld IxIn al high" dn'/lIitJrJj is dt>p('tltknt (In rhl!\O! and ahundull~
<br />o/.'iund temporaril)' .s/f1red tm fh,. channel bottom and ,hi' Juradon
<br />~nd Magt' (if ,Ir,. high u/t'Q.\t'. A'__ and ex;..!;,,!! deprnit... ar, lIalued
<br />Nlm/'flr/ent.' of lht' ril'erint' <<l1JJ"MenL They pmvidl' hum/at for nalil't'
<br />ulUllwn.nutivt'jhh. (hI! lulxtrult' for ripurirm W'KI'lution. no,sion-
<br />prrJIl"t'tion for urehevlngicul.\;ln. and are 1I.'Ot'd jur camping hy rb'n
<br />runnt'TS. The /995 Glm Canyon Dum Em;ronmt'nlallmpot.1SIIJ/,."..",
<br />rt'COmmt'nth ,,,('Jreduli'd high rrlrous of !J.hor1 durulion be implntJl'II1t'd
<br />for en)'ironmt'ntal purpO!f.t!j (U.S. Departmenl (if Inleriuro 1995).
<br />/labilal mtlinlenunc~ flOIn (lUff') urt' wilhin pll....erplunl capadlY
<br />(-940 m-~/f). ...'hl'rt'U_f Ihofl' ahm'I' 1M, din'hary:1! arl' bt'ach/hahitat_
<br />mli/dinK flo...', (8118 f). Tht.' pJrmt'r ...'t!fl! inlt'nJt't1ltJ mai"tai" exiMinK
<br />('ampi"K ht-achf"l uffd wili/life hahitat und lh", hmt'r 1/1 mllrl;' l'.\7t'J"i1'e~r
<br />modi/!' and {'reate 'and han. and rhln re\lore 10m.' of tht' dynamic..
<br />that r",'ull from fllH}dillK in the eCl}\)"Um.
<br />
<br />Flood Experiments n the Colorado
<br />River Ecosystem
<br />
<br />In thi~ !>Iud} Yoe ~valuate the elfec'-~ ofthn:e intentional. controlled
<br />11000.15 thai ....ere relca,>ed in 19<)6, 191)7. and 2000. We Ctlmpare the
<br />results tn a natural nooJ thai occurred in 199_l. lne first test of a 1111111'
<br />tx:curred in spring 199b, \\ith a 7-da} release of 1.274 mIls. :\ ll\lF
<br />tesl occulTed in '-'n\emtoet I'l"n. tollo....ing large sand inputs from the
<br />Paria River in late ..ummer 1997. lne t)hjecli\e of the 11)9711\11-' W;I"
<br />to tran"fcr somt' of the trihutal') supplil.J sand to the banl-s and hars
<br />before it \\,a... transpo.Jnl..J dtmnstnoam_ This rdea.sc h;ld a 2-Ja} dunllion
<br />ofR6S m.l,s. .-\ ..econd 11\11' e\pcrimenl O\:curred as pan nfthe 1.0\\
<br />Summl'r Ste;ld} F1o....s (LSSFI in 200(J (Fig. I I. flit: I.SS!' \\,as lksigned
<br />to test the henclib oflo\\' I1m\s on nali\e fishes ot'th~ Color;wn Ri\er
<br />hdow (,Ien Can~on O"m. rhe I.SSF \\,as pree....!ed in \l3} h~ a ~-da}
<br />spil-eofR5R ml\.lMrtl} mlendl..J In imp~\\ea4uatic n.1biUt to} n-building
<br />and rt"stnlcluringsand hars. In addili~ln. an unregulated Janual') 1t}<1]
<br />11,'ll~ on the Littl~ Col(lradll RiHr deli\cred I;~e ;tm~lunb of sand ,md
<br />inl'rcao;ed the JiSt:harge of the Col('rdllo Riwr to a pcak ofappnl\lmalel}
<br />1)50 m>s (Wi~1e et al.. I 'J<)fl I, rogelher. IheH' four Illluds 1.11' near
<br />pt'wcrplant cap;}~-ity or gn-ater pnl\ ide an tlppt1ttunit} Itl measutC sand
<br />har rcsJ'tlllsc 10 110\\, magnitude and the liming relati\e 10 lributa~
<br />sediment suppl~
<br />
<br />Hlg -Elevat on and Bars ere
<br />easured Before and After the Spring
<br />000 HMF
<br />
<br />In 1990. ,I project moniwring sand bars in th~ CQlurado RiH'r
<br />ecos} "'tern \\a<. initiated h} \."rthem :\rilllna l ni\ersily. Since then.
<br />the S1ud~ site", hale ht.-en monit~'red annua!l} and bc:lllr~ and alkr lluod
<br />e\ents_ Site locali,ln". m"'lhods. and results can bc: (tlund In J1aJ'~1 el
<br />al. ( 19')</) 1 he ",ite.. are representati\e 1.11' the dilf('renlt~ pcs l.f edd~
<br />",and hat"> and an' "'p;lliall} di_~tn"uted thrtlugh~lut the rOI~ltado Ri\er
<br />eC(lS~stl'm.
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<br />2000
<br />figure 1. Instantaneous discharge at USGS "rearntlow gaging sUllion
<br />COlorado R....er at Lees Ferry. ArllOna. Man;:h-June. 2000. The timing of
<br />measurements made befOre and atter the spring 2000 HMf are shown.
<br />
<br />We calculate the area. \olume :lnd thiel-n('s" ohand stored at high
<br />e1e\alion:lt each bar. We define hi\;!h-ele\atiun as the area that is
<br />emergent.1I a tl.m of 56(, m "~so a m..d~ratcl} high !lo\\,' in the pt)st dam
<br />era (IlMel et a1.. 191)91. (\reas helo\\, the \I;lge elevation reached b}
<br />this Ill'\\' ;Ire regular!} inundated and re\\orl-~d by dam rclea<.es and
<br />t}pkall} are nOI a\ailahle for camping or coloni/ation by plants.
<br />
<br />Long-Term Tren 5 In H g Elevat on
<br />Sand Bar Storage
<br />
<br />To id~nlil) long-term tr('nds. <lur approach i" to develop a time series
<br />oLIH'rage high-elevalion change tFig..n 'h~ sample population is
<br />div'idl'(l into sites in \lar"lc <'an}-on (upstrl'am from the Linle Coloradtl
<br />Ri\cn and thoSt: in Grand l;tn}On (do\~nsttl'am from Ihe Linle Colorado
<br />RiH'rJ. One site is lucated in Glen Canytlll. Ihe reach closest to Ihe
<br />dam. rigure ~ indicates Ihat the 1t}<)J Linle C{llorddo Rivet ll~'ll>d and
<br />Ihe 199(, BllBF wert.. Ihe onl~ high tlo\\,s to signilic3I1tly repleniSh sand
<br />in high dcv;ltion hars. Although r.!pid adjustmem ofnewl}-aggraded
<br />bars to normal dam relea.ses led to high rates uf em...ion following these
<br />e\em.... the rah.'S dl"Crea'-t...J \\'ith time. ,\fler mute Ih3I1 a year. on avcr.tge.
<br />the sand bars were <'Iilllargcr than the} had ht.'en before eilhcr the I'l"))
<br />11.1l>d llt the Il)t)o RIiBI-'.
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<br />2000_
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<br />19911992199319901 19951996 19971998 1999 2000
<br />
<br />Figure 2_ Average hlgh~le...atio" sand thiCkness changes vel'$US time.
<br />Error bars are sl.lndard error aboullhe mean.
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