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<br /> <br />(,") <br />U.. <br /> <br />CAUSES OF SALDlIIT <br /> <br />-- <br />,'. <br /> <br />o The ~mall a::J.ount 0:" Jata present~' &\'ailable ~=i yes i!:riicatior::s of <br />much variation in tile '3..-n01l..'1.t of pier-.up :'ro!!. land 'iue to irrigaticr.. The <br />esti~bted salt picku~ i~ this report is Lasea O~ v~lues of zero and 2 tons <br />per acre :.ror.: ne.....l:,' irriiated land. '::::'ero aT !)",irjicr\lIT_ conditions oc::ur gen- <br />erall:>' after initial leaching in areas ..l:ere soils 2re loose arid cor,~ain <br />'ler-J little salt. The 2-tor:-per-acre value ...'as selet.:te1 as the hig.l--Jer er.d <br />0:' the range ::.or the average pickur o','er a rro~~ct are!;.. It ...:as also <br />a::s"J.:ted in Hils repo!"t. no <J,.j-jitior,al riel-,up ',;oulj !'esult :'rorr, s.J.pplcz;iental <br />'''''f:Lter applie-l to preser:tly irrVatei lan<ls. <br /> <br />~. <br /> <br />;,u.r:icipal ~nd Ir.hstrial ~)ources 0:' Salinity <br /> <br />Salt loads contributed to ,,!-,e Colorad::l River :T'Jster.. by ~......,icipal <br />ar.::i industrill sources in ger,er9..l are minor. totr~ling about 1 percent of <br />the ba::::in ::::alt loa::i. Future increases if, salt lC9..::is 1'ro:r. these sources <br />are expected to be s:r.all relative to the total t,o,sir. salt. b.,rrier. and <br />~ill have only a ~ncr elfect on sali~i~! levels, <br /> <br />With the ex~eption of concentrated return flows from the Ias Vegas <br />~ea. ~ost municipal and industrial wastes are relatively lo~ in total <br />salt load in co~parison with ~atural and agri~ultlU'al sources, ~nd ~om- <br />plete elirr.ination of such ...aste ::iischar,:es would have Ii ttle e~fect on <br />salir.ity concent,r3.t,ions in the IT'sin river ~.iste:-;. fi!":ce -::.he:oe \o'o.stes <br />are point sources of salinity, control of a 2a~ce could Le achieved. if <br />salinity levels it:. tne ."<loste being J:ischarged (i.e.. i!;'Llstrial brines) <br />.,;arrant such control. <br /> <br />b. Salt Conce:n.raLng <br /> <br />AJditior: 0:. salts to the river system is not the only cause of in- <br />crehsed salinity cOf:centratiop.s. The ie-pleticr. 01' ...."'.ter c:' higher qual- <br />ity tha.'"! in :iowT:strea::n reaches ;,roduces 8. concer.tr'itio" e:'fect or: the <br />~aters of the downstre~. reaches, ~his concentr~tion e~:ect occurs to a <br />greater del7ee ...'hen the diverted salt:,: retur:, "':-0 the river than -..then <br />they are ::iepleted along ...:i ii, the '..ll. ter. <br /> <br />Ir.-basir. Depletions <br /> <br />Con~~ptive use oi -,.;ater ior irrigatio~ ~ith:~ the basir. is respon- <br />sible for the largest iepIeticr.s .,.,hile cor:sunptive use for ll:'.m.icipal and <br />iniustrial purposes ac~ounts ~or ~ ~ch s~~ller depletion. Svapcration <br />:ro~ reservoir anJ strea.~ surfaces also produces large depletior:s. ?hre- <br />atop~es, too. ~ause sigr.i~icant ...~ter losse~ by evapotranspiration. <br />especial~. in the Lo....er Basin bel e'..' Hoover Ja::. Ir: =,ost C!'ises ....here in- <br />basin ieple:ior.s occur. salts retur:1 to the ri-;er syste::" s.djing signi:~- <br />icar.tl~y to the salt concent~9.tion increase, <br /> <br />2e <br /> <br />