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<br />
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<br />en
<br />00
<br />~)1
<br />
<br />Thc ma\imum. mean. and minimum annu-
<br />al di!>sol\"ed-\olid~ load for the 26 sites in the
<br />Colorado Ri\er ba~in are summarized graph-
<br />ically in figure 44. In the upper Colorado River
<br />basin. the mean annual di\sol\'ed-~olids load~
<br />increase in a dO\..nstream direction. The dis-
<br />ml\'ed-\olid~ load.. also increase in a down-
<br />stream direction in the IOYoer Colorado RiveT
<br />basin, except at site 2..t belov. Hoover Dam.
<br />Do\\mtr('am from Hoover Dam. the dis-
<br />solved-solids load actually decreases. due large-
<br />ly (0 decrease.. of waler discharge in the lower
<br />Colorado Rhcr basin as a result of increased
<br />di\l:r..iom behind Parker (site 25) and Imperial
<br />(sile 26) Oams, Although the dissoh'cd-solids
<br />load and wat('T discharge decrea..e progrc.ssively
<br />dowmtream in the lower Colorado Ri\er basin,
<br />the dissol\ed-solid~ concentrations increase
<br />(fig. 45: tablc.tl.
<br />The concenlration of dis~ol\ed solids often
<br />is a h~,tler index for locating sources and re-
<br />gions of poor water quality than is the dis-
<br />sol\f:d-s(\lids load. \Iaximum, mean, and mini-
<br />mum annual dissol\ed-solids concentrations
<br />for the ~fo stations are shown in figure .t5.
<br />.\Iean dissol\ ed-solids cOIll'entrations arc great-
<br />er than ~,500 mg/L at only ~ of the ~6 stations
<br />in the Colorado Ri\er basin-sitc lfo, the Price
<br />Ri\er at Woodside, Utah (2,720 mgJL), and
<br />sile 18, the San Rafael Ri\er near the Green
<br />Rher. Utah (2,500 mg/U. These large concen-
<br />
<br />.
<br />
<br />National Water Summary 1984-Water.Ouality Issues
<br />
<br />75
<br />
<br />trations art' 311ributable primarily to dissolved
<br />solids gained as ....ater no....s through the irrigat-
<br />ed areas of these drainage basin~. A smaller
<br />contribution is due to overland no.... from
<br />desert-rangeland areas in these basim.
<br />
<br />TRENDS IN DISSOLVED-SOLIDS
<br />CONCENTRATIONS
<br />
<br />Trend~ in dissolved-solids concentrations
<br />have been investigated at 2fo stations in the
<br />Colorado Ri\er basin to determine if changes
<br />h:ne o(curred hetween 1965 and 1983 (fig. .tfoJ.
<br />Concentrations ....ere adjusted for now to mini-
<br />mile Ihe impacts of changes in 110.... 011 concen-
<br />trations and 10 give a more reliable indication
<br />of the actual changes in the processes that
<br />deli\er dissohed solids 10 the streams (Craw-
<br />ford and others, 1983). The trend~ were .stalis-
<br />tically tesled al the 9O-percent ..-onfidcnce level.
<br />Data from 23 .,lations show a ~ignifi....-afll Irend
<br />in the ....-oncentrallon of di~soh'ed solids (fig.
<br />.th), DC'\.'reasing !rend.. .....ere detected at 20
<br />.,tations on the main stem of the Colorado or on
<br />major lribularie... Increasing Iremh \~ere
<br />delecled for only Ihree .,itcs 011 tribulary
<br />slreams: ,ile 5. on Ihe Dolores River near
<br />Ci..1..'o, Utah; site 1.3, on the Little Snake RivC'r
<br />near Lily, Colo.: and .,ile 23, on the Virgin
<br />Rivcr al Littlefield. Ariz. Only 3 of the 2fo
<br />staliom .,how no trend...
<br />
<br />Table 4. Mean annual water discharge, dlssolved.solids load. and dissolved.sollds concentration for 26
<br />stations in Ihe Colorado River basin. water years 1965 to 198310ctober 1964-September 19831
<br />
<br />111'/S" ,'II!>1( f~~l per -..:,'oml: m~ 1 = mllll~rdm' f1.:r liler; '1>n. \r 1""_ per 'carl
<br />
<br />Slle Dissolved solids
<br />number Station name Water Load
<br />00 discharge lmil1ion Concentration
<br />fig " (ftJ,s) tonlyr) (mg/L)
<br /> ('otoradt'R"crar 11"1 Sllll'hllrSl'rin!!,. Colo,- :'3U 0.0:' ~.
<br />, ("olorad" Il,,,cr ncal (ikn.."...)tfSrring'. C"lo.- :',:'():) .~(, 1.10
<br />, C"torad,~ Il,"CI neal Cam~.. (""Iu. l,7(~' t.4~ ~.lH
<br />, tillnni-.on Ri,'er near Glan(] Jlln(lI<'l1.l"lu.. :',.ltXl Ul 130
<br />-< n..lnrC" Riu:r nCilr Ci-..:... UI;lh ~" .51 I.MO
<br />, Col"lJdtlRI'crnearC;"o. L'(ah 1>,700 1.i~ ~70
<br />, Gr<<n R"er J.l Warren BrJ.;I~e near Damd. W~o.- 5:'0 .117 :'~O
<br />, (irct'n RI\Cr t:>c:lo'" ~onlcnclle Re,enou. ,""l._ 1,71M\ ,,< :'.10
<br />, Gu...n R"cr ncar(irC'Cn Rivcr. .....~.o. , 1.'YllIl <, -"10
<br /> -'
<br />II> Bla,~, hll~ near I Illlc ."merica, Wytl. Pel .:'1 ~1n
<br />II Glc.:nR"ernear(irC'Cndalc.L'(ah :'.:'llll l.cl~ ~CMI
<br />" "amra Ri'erno:-ar'l;l\I.dl.Colo. 1.t>t...1 " :'l\()
<br />" tlllleSna~e R"t't near IiI.. lul.. "'" .13 "-',
<br />" t)u.;hc,n.'R"cr ncal Randlcu.Lilah ~,{l ,- 1.010
<br />I' Whllc Rl'er near \\al,,-'n. l'lah , MO :'7 ,.,
<br />" f'rl.:cRI,eraIW,,,)tf,,dc,Ulah , - "" " ':-.7~O
<br />" (irn:n Ri_n'lI Gre.:-n Ri,C'r, L:(dh n,t.1I1 :'.7< ~~il
<br />I> "'..nRaraclRI\Crnear(,rC<'IIR"er,l:[ah 130 I' :'Y"l
<br />I' <;anJuan Ri'ernC'31 ,'\rchuleta, ~ \"'\. 1,:'1.) ,I' t70
<br />:'0 "nJuan R"",rnear BllIff.Cull. :',:'Il) l.iW) <<0
<br />" ("tll''1ad.' R"et alt en ~en', Ani. 1:'.1\1-"1 ~,Ot> ~Il(l
<br /> l"ulotaJd Ri'cr near Gran<J Can\'l'n. '\rir. 1.1.1111) S,I"'1 h1n
<br />~.I \'lrgIllRl\Clalt;nler,cld,\ri/._ :'7(1 T 1.l\'Yl)
<br />" ('olt.r..d" f{l\cr t>cl"", HOt)'el Dam..'\nt.-l'ooe' I:'JIIXI l'.ll :lll
<br />:'~ (""k,raJ'.Il".....r ne.u I'ar~..r Dan1. Ari/..Catir.. IO,IUJ ~ :'t ~~O
<br />" ("otllr"J,' Ri'er aNwC' Impe-riat Dam, .-\ril.-la1if. ~.s{1I1 - " ~~O
<br />
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