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<br />
<br />
<br />W Values for intermediate locations in the river ar€' shown
<br />o in Table 2.
<br />I-
<br />
<br />,~
<br />-
<br />
<br />Table 2
<br />
<br />Water. GeneraHy. such crops hJve i:I low salt tolerance
<br />thus Yield is repressed by the salinity.
<br />
<br />With respeCt to crrteria for public Water supplres,
<br />desirable levels are specified as less than 200 mg/I and
<br />the recommended levt'I should nOt exceed 500 mg/I.
<br />From Table 2 it is apparent that some present s.aJin'ty
<br />levels exceed these values.
<br />
<br />It should be emphasized that when trme rntervals ale
<br />reduced to a mOrJthly basis. WIde fluctuations carJ be
<br />expecled. UrJder historic cOrJditions aT Imperial Dam,
<br />the salirJiry ConamtraT,on for January 1957 was 1.000
<br />rng/l and for December 1967 it was 992 mg/l. Six OTher
<br />months in the periOd 1941 to 1970 have had average
<br />conCemrations above 960 mg/l. Moreover, under
<br />present condiTrons of depletion, the mean mOnthly
<br />concentration of 1.000 mg/I at Imperial Dam WOuld
<br />have been eXceeded in 40 mOnths during the period
<br />1941.70. Such monthly salinity va!ues have grealer
<br />signrflcance than long. term means in relaTion to
<br />impacts on land and crops. water Qualily standards,
<br />and waTer Trealment.
<br />
<br />I'HOJf:cn:/I .- II.I\/Tl 1.1:1 f:I..-
<br />
<br />The sallnrty in the Colorado River has been the Oblt'ct
<br />of longstanding COnct'rn and Hudy. Sludies by various
<br />agenCies Convt.'rge to on.. srmple fact-s.aliniIY will
<br />increasl:' wiTh COntinued use dnd development of the
<br />aVdilable waTer supply unless comprehensive, basinwide
<br />water Quality management Dlannmg '5 implememed
<br />and sUPPOrted by the rnsTallaTion 01 structural and
<br />110nst'UCtural measures. ProJccted estimates by VdrlQUS
<br />entitles arc presented in Table 4 Thf;'SIc! eSllmates
<br />assume ThaT no measures ar!" undertaken to Control
<br />salrn'ty.
<br />
<br />The drffe/ences in the values 'epOrle,j by the various
<br />agencres arise from aSSumptions made regarding
<br />completion dates tor Winer development projeCTS,
<br />estrmates at the amOunt of salt loading or
<br />concentration effects prOduced by these proJects, the
<br />period of analysis used. and eSTimates at the t.me
<br />mvolved for the effeCls to emerge at Imperial Dam.
<br />
<br />It IS significant that all studies by the var,ous agenc.es
<br />predicted that prOPOsed de~elopments will cause a
<br />considerable rncrease rn the future salimly of the river.
<br />Even under Current saliniTY conditions, many irrigaTOrs
<br />are reSorting to SPE'cial practices In using the waTer to
<br />grow Salt'sensrtl~e CrOPS. Some areas have adverse
<br />drainage conditions which would be magnlf'eu if higher
<br />
<br />, "w"" Q"",,, C'i"",,, Repoil 01 <h, N",o"" T"ho,,-,, Ad."o"" Comm,,,,, '0 Ih, 5"",,,, 01 the 10''''0'.
<br />USDI, April 1968,
<br />
<br />HISTORIC AND PRESENT MODIFIED
<br />QUALITY OF WATER
<br />COLORADO RIVER-AVERAGE VALUES
<br />1941.1970
<br />
<br />Locatron
<br />
<br />Cono:>ntration
<br />1m II)
<br />Historic MOdified
<br />
<br />15
<br />
<br />
<br />GlenwOOd Springs. Colorado
<br />Cameo. Colorado
<br />C'sco, Utah
<br />Lees Ferry, Aflzona
<br />Grand Canyon, Arizona
<br />Hoover Dam. Arilona-Nevada
<br />Imperial Dam, Arizona.Cal,fornia
<br />
<br />271 310
<br />406 443
<br />613 662
<br />556 609
<br />617 669
<br />690 745
<br />757 851
<br />
<br />PHYSICAL INTERPRETATION
<br />
<br />Current Wdter Qualrty cr'terial specify Thatdetflmenldl
<br />effects will usudlly be nOTed on crops when
<br />concentrations in the irrigation water eXCf:'ed 500 mg/I
<br />of tOTal dissolved solids {TDSl. The suggested
<br />gUidelines far Salinity in irrigation WdTel dre:
<br />
<br />Taule 3
<br />
<br />SUGGESTED GUIDELINES FOR SALINITY
<br />IN IRRIGATION WATERr
<br />
<br />Crop response
<br />
<br />TDS (mg,.'IJ
<br />
<br />Water for which no detrrmental
<br />effects will usually be nOllO!d
<br />Water which can ha~e detriment.;!
<br />effects on sens,'ive crops
<br />Wate, That mavhaveadverseeffeclS
<br />on many ClOpS and requiring careful
<br />management praCTices
<br />Water that can be used fa, salT-
<br />tolerant pl;l'1ts on permeable sods
<br />\\11th cardul management practires
<br />
<br />0-500
<br />
<br />500.1,000
<br />
<br />1,000'2.000
<br />
<br />2.000-5.000
<br />
<br />A very complex relationship '5 invol~ed in relatmg
<br />salinity of irflgation water to crop yield Md!OI factors
<br />InVOlved are sod conditions. crop typ~' dnd variety,
<br />drainage. cllm<lle. ann cultural and rrrigaTrOn praCT'Di's.
<br />Mdny h'gh-va1ut.'d crops <Ire grown With Colorado River
<br />
<br />
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