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<br />. <br /> <br />SUM."1.ARY <br /> <br />- <br /> <br />This report, pr~pared and updated every 2 years, presents the <br />V.HIUUS impurtant water quality aspects vf the Colorado River. Althvugh <br />s<.'vt::lal waLt::l quality parameters .'Ie.:: disc.:ussed. the major part of the <br />repurL 15 .::dlvLted tu balinilj (t..,tal diss01ved solids) becaust:' it is <br />pl"':'t::ntly the must serious quality pr0blern in the river system. The <br />hlsluric.:al and ploj~cted fuLur", salinity conditions of the Colorado River <br />B~bin al~ plt'bt::nlt::d in this repurt. <br /> <br />.... <br />..;. <br />(;J <br /> <br />Tho.: hiblurical rt::cvrd ....as eValu<lled at Imperial Dam (see Figure <br />VI-2, pag.: :'6). Salinity was found to bt; increasing at a rate of 3.9 <br />mg/L pt::r yo:':H U...."'I the 1941 to 1981 pl::riod of record. This amounts <br />lu an intre.:lst;' In salinity at Impt'rial Dam of approximato:ly 152 mg/L, <br />StiJtistl\.al analysis of the trt:nd showed the annual salinity varying <br />...ithin th" 95 perLtmt (vnfidt::nce interval of +118 mg/L. The increase in <br />salinity is allr ibuti:lblt: tv many (.aust:s but primarily the increase is du€' <br />tv the d""v,dopm""nt ot the Colorado Hiver Basin, <br /> <br />. <br /> <br />The Coloradu klver SJrnulat ion System (CRSS) ....as used to predict the <br />~'ltlo'(.t luturt: develupment will have on salinity at various key stations <br />"'lthin the baSin (so:€ Table B, page 47 and Figure VII-I, page 43). CRSS <br />was al:;v u:;t:d to pr""dio.:t tht: salinity within the basin assuming the <br />...at",r quality imptuvemt:nt program shown in Figur"" VIII-I, page SO, IS <br />il1.t->lemlo'nt",d. Tho: l>alinity at Imperial Dam is pro:dicted to inl.r.::ase <br />110m 816 mg/L In 1981 tu 1,089 mg/L in 2010 without salinity control. <br />:-.allnlty control would It'duce the 20]0 predicted salinity to 894 mg/L <br />l~~'1o' FIgure VIII-2, page 51, for comparison). The annual damages to <br />Illw....r baSin watt'r users IS estimated to be $513,300 in 1982 dollars for <br />t::ah I mg/L Inctease at Imp~'rlal Dam when concentrations arl? within the <br />tange ut 675 mg/L to 1,225 mg/L. <br /> <br />Salinuy should remaIn within tht: salinity standards over the next <br />5 y~ars unl~ss several years of low flows occur. Should several years of <br />extrt:mt'ly high flows occur, spJlls I.o'ill be required and TDS would drop <br />slgn1l1Ulntly, baso:d on 1980 lunditions. Large spills clJuld reduce TDS <br />by Iliul~ than IUD Illg/L. <br /> <br />Futult: l>dlinity plvj",~tilJns using CRSS aro: dependt:llt un sch",duled <br />d"'l-ddiun~ ih_tually ou.urring. In the past thO:" predicted depletions <br />aSSOl iatt:d ","ith en~rgy development have oat occurred, and ther~fore <br />s811nit.... pr\.ljt:ltiuol> "'~re alsv high. Verification vf Sv!Dt' of the hydro- <br />;;dlirllty ni~\.hanisms used tv prt:dilt futurt: salinity conditions will <br />l",quif'" llbst:rvalllln 01 an actual p",riod of prolonged rest:rvoir drawdown. <br /> <br />. <br /> <br />DUI ing tn.- filling of the ClJlorBdu River reservoir system, highl:.'r <br />IlJS wat~T was stort"d while lo",'er TDS water \o,'as passed aownstream. Wtth <br />tht: r..!ioo'"rVOlr systpm at nl:'ar capacny, the possibility of high flows <br />!~qulrlng spIlls through the reservoir outlet works may flush higher TDS <br />...'at~l t10m th", res~n'lJirs. This "'I.m!d not be necessarily detrimental if <br /> <br />vu <br />