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<br />CHAPTER II. THE SAlINTY ISSUE
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<br />The walers of the COlorado River system serve millions
<br />of peOple In many Ways. " is il Vlra/link in SUSl<linillg
<br />cllies and farms, mines and industry, reca'aflona' spare
<br />and lVild'jf~. .Jnd ilreaS of great esthetIC value 10 Ihe
<br />Nation, The Woller is used for rrn9,H!f1'9 crops,
<br />prOdUCing ent'rgy. prOVIding recreallOn. $Uslam'ng
<br />livestock .md wildlife. SUPPOft,ng industry, ;J'ld
<br />SUPPlYing the commOn daily n{'eds of people II,s the
<br />SOurce of waler fOr Cities wllhln lhe basin .md larger
<br />metropolitan areas OUlslde Ille baSin. A Idr!Je Variety of
<br />crops. prOviding d needed diverSity 10 l~ n,Uronal diet,
<br />are Irrlgafed by iU 'Villers both Within ilnd OUTside the
<br />basm. But the concentratIon of drSSOflled ~lids If1 the
<br />river, now among the hlghesl of In!' great rl....en of
<br />NOtth America, ;s Increasing. The Increase 1'.';11 further
<br />imp.iII the usefulness of the warer.
<br />
<br />The fong'lerm 1941.1970 hlllorlc average ,mnual
<br />s..lmlr,. cona-ntratlon 0/ the COlorado River al ils
<br />h~'ad\Vaters IS less thJn 50 my/f, Ar Impenal Dam. the
<br />lasl malar diverSIQrl POIllI In the United Slares, the
<br />COncentrallon IS 757 mg/!. MOdifYIng Ihis hlStonc
<br />COndition 10 reflecr all uPstream ellisting prOlects to be
<br />In op.:raljon for the full Pt::rrOd 194] 1970 WOuld again
<br />show a conCl.'ntrJtlon ot less than 50 mgJl at
<br />head>....ill..rs ilnd a ~illue at 851 mg'l at ImPt'nal Dam.
<br />
<br />Rising h'gh II"! Ihl.' ROCky MounrJms, lhl' Calor deJa
<br />AI....el flo.....s for mOst of its lenglh thrOugh arid and
<br />semiarid legions of Ihe Unill'd Slates and MeXICO. The
<br />great liVer and lis l"t.lUtarles hiwt' cur mfO mOuntains
<br />and P/dleaus, fOrmro allUVial valfeys. CClrvcd
<br />ma9nllic~'1H canyons, and prOduced a highly prOductIve
<br />de",). In the wOCt'ss, ;ts walers aCcumUlate the SOlutiOn
<br />products ot erosion and weathering_ from hearJWqlers
<br />to mOuth. a dlstdflCt' of nearly '.400 miles. the salinity
<br />progreSSlveIY;nCreJSI'S,
<br />
<br />The riveT drams 242.000 SQuare mlles-lil2 lhe
<br />contermmous Jlea of the United Slales_a'ld 2,000
<br />SQUJle mifes In Mexico. The bdsm includes parts of
<br />seven SIJres-SOUthwesrern WYOming. weSlern
<br />COIOlddo, parts at Ulah, Nevdda, New Melllco, nearly
<br />alf 01 ArilonJ. and d small seCt/Ofl of Cal;/Offl'iI F rOlll
<br />Ihls "rea, It Cdffles a salinity burdell of 10 million fon~
<br />dflnuall~ Eilch SQuilre mile dOOve rhe Gt,lIld Canyon
<br />COnlritJules .m aVt-'r~ of a/JOul 70 IOns of s..lt ro lhe
<br />r;vel each year The Sillt lOading arlSl'S from borh
<br />naluraf Jnd rnanmadc soura.s The I..."ter IS USt'd and
<br />reused St'vera! r'Illes along ilS lengfh CillJSl/lg the volume
<br />of d~d'fable warer 10 decrt'ase While Ihe salilllty
<br />mcreases. The Potential dernands 01) Ille rr~er ellceed
<br />'IS denendablt' SUpply The mala/ oVerrrdlrlg iSSue On
<br />lhe Colorado AI...er l/1"'o"'es rhe mtelrl'li:ltt'd marter 01
<br />Inade(wac:'Y of Waler SlJppr... 10 meer all PfoPOsed uses
<br />and delf..'I'Ordtmg waler QU3Iil)i
<br />
<br />....O( un:.... OF '''\I.I\/n
<br />
<br />In an~' li...e/ system. sahn'ty concentrations arise trOlll d
<br />Sdlt loading effect dnd a salt con~ntrat,ng erlect. The
<br />salt 10<ldrn9 may be re9drdf'd as Ihe P'ckup of s.;ll due
<br />10 mmer.tl we,Hher,'lfl dnd diSSOlution of tht' solubl!'
<br />
<br />13
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<br />safts residIng In soil dnd substrata. The salt
<br />concentralmg is due to the evaPOlranspiration of lhe
<br />Wilter carrYing a lin;r" 5<llt load 0/ the ellpOrt of
<br />h'gh-qual;ty Wafer OUI of the basin, Generally, Ihe
<br />app!ICation of "rigarion water reSU!Is In increased sail
<br />Concenlratlons because of bolh load,ng Jnd
<br />COrlCenlrating. The evaPOraled or Iranspired Water is
<br />free of sdlt. henCl;', Iheg'Ound'water relurn flows carry
<br />Ihl' to tar salt burden. Under Some condiTions. however,
<br />salts md)i be preciPilaled and Slored in Ihe soil. These
<br />ProCt'sSt's OPera Ie Ihrough the 9'!Ocht'mical C'yc!e
<br />depiC1ed If} Figure 1. As Water IS evapOrated trom the
<br />ocean or Of her free Water surface-so Jlle/alions If) rhe
<br />COmposn'on an(1 conCentriltlOn of the dissolved
<br />contl\uents hegln to OCCur and COnlinue a~ the
<br />cona-nlralron progleSSlvely mcreases during movefl1t>nl
<br />IhrOugh the CYcle.
<br />
<br />While rhls proa-ss adds a farge variqy of diSSOlved
<br />n1.Jfll!r to Ihe Wilter. only 10 elements made up aboul
<br />99 percent 01 the d,ssofVed COnStituents. These are
<br />hYdroyen. SOdium, magnesium. POtassium. cafCium,
<br />sjjicon, chlorine, ollygen, carbon, and sulfur The
<br />erements OCCUr in solullOn as various ions. mOleCUles.
<br />01 radicals, Tht' major Pdl/ of the diSSOlved
<br />COrlstltuenls In COlorado R'ver Willer is made up Of thl;'
<br />calrons: calc,ufTl. magnesium, and SOdium; and Iht,
<br />aniOns: sU/fact', Chloride, and bicarOonJte. These. plus
<br />mlno, amOUnts of Other diSSOlved COnstituents. ate
<br />commonly referred to as ~dl;nllv. "Salt,'. dissolved
<br />solids. or dissolVed mineral OOnlent.
<br />
<br />Sru(jll'S of Ihe operallon of the geOchem'cal cYcle
<br />suqyest fhat .thou! halt Ihe salinity cOI1Ct'ntralion ill the
<br />Walers ill HOOII"'r Ddm ;s deriVed from natural sources
<br />dnd Ihe remdlf1lng hafl from manmilde uses. The orffel
<br />of magnitude frOm greafesr to leaSI is: natural Soura-s.
<br />Irrlgallon, reservoir ('Vaporallon, OUt'Ol.basin ellPorl,
<br />Jnd muniCIpal and industrlaf SOur~s.
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<br />....\I./\Irl U,\U.....
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<br />HISTORIC ANQ MODIFIED CONDITIONS
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