|
<br />,TME PROBLEM'
<br />
<br />The Colorado' River Basin enc:ompass1!s por_-,
<br />tioons of severi states. 'nufrivl;!r tiaws' over
<br />1,400 miles frOOl headwaters in the,-;Upper Basin-'-- .'
<br />'in Wyoming and 'Colorado,-jofns:with tribll-
<br />tades in Uta~ and, New Mexico;-_ flri'i!s: throtlgh
<br />the Lower Basin belo,w Glen.Canyon Dan ,and- the
<br />siates of Nevada, Ar,izona, 'aor;! Califorrfla. and
<br />terminates in the Gulf of Cal.ifo'rnfa_ in- the
<br />Republic of Mexico..- '., .
<br />
<br />Use of the river's water now and in t,lle future
<br />has bee!,! allocated througti a long history of.
<br />negotiations t:hat. include j:ompacts.- litiga-
<br />Uon, legislation-,_ and in~ernational treaties.
<br />
<br />About half Of the present salinity cQncentra-
<br />tion in the, Color'ado River: at Hoover Oarr near'
<br />Las Vegas i~' attributed to natural sources. '
<br />The remaining half is man-indUClOd as indicated
<br />in th'echart.
<br />
<br />SalimtySourC2s
<br />
<br />
<br />,\
<br />
<br />47% Natural:?ources-
<br />-31%'lmgailon
<br />12% ReSery';Hr
<br />, ,Evaootation
<br />J%.E:xo'OrlS
<br />1'"1.M&!
<br />
<br />,
<br />"
<br />
<br />iil
<br />j'
<br />
<br />. .
<br />Fo~ irrig,ato'rs. the ,_h.igher .conce~trat ions
<br />cause decreased. crqp yields, altered ,crop
<br />patterns, inc.reased leaching and drainage,
<br />requirsnents. and: increased. managenent costs.
<br />Agricultural losses (either through lower
<br />ytelds or increased production/m~nagenent
<br />costs) begin when sal inity levels of applfed
<br />irrigat ion water reath 700.to 850 mg/l-,
<br />depending upon .soil conditions dfid type of
<br />crop grown. A slJJlmary of the effects:is
<br />presented below:
<br />
<br />mg/l
<br />
<br />Effect
<br />
<br />Below 500
<br />Above 500
<br />
<br />Good drinldr'!g w_ater
<br />Municipal and industrial
<br />losses
<br />AgriCl,Jltural losses
<br />
<br />700-850 and
<br />above
<br />
<br />The Colorado River, at its headwaters in the
<br />mountains of north-,c-entral Colorado, has a
<br />salinity (dissolved minerals) concentration of
<br />only about 50 mg/L. The salinity conce'ntra-
<br />tions progressively increase downstream_as a
<br />result of water diversions, and salt 'conttibu-
<br />ti'ons frOOl a variety of sour:ce.s~ In 1919, the
<br />sal inity concentration averaged about 810 mg/l
<br />at Imperial Oilll. the last major diversion
<br />pOlnt on the Colorado River in the United
<br />States. Without control measur'e!i, the concen-
<br />tration is projected to increase, possibly
<br />reaching a level-of 1140 mg/l at !mperial Oan
<br />by around the tu~n of the century.
<br />
<br />.-' .' .'
<br />. .
<br />Sal inlty ,hicre_ases res.ult from two prp.ces.ses:
<br />::;salt- .loading an.d salt concentration-. Salt
<br />-,l.o,-ading inc'reasEH> th.e .(IJI\lunt of. salt'_for-_a
<br />','-give'n iIlIoun't of water;-'and-'salt con'centration
<br />'~,de,creases: HIe anount 'Of di lut.jng water_ for a
<br />"g\v-e:n .o'JlIount of-salt. . SJlt loading_ is the
<br /><:add1-tion to ,the ri-v_er systsn of mineral salts
<br />"f,iQrn' natural and manmade'"sources.' Salt'
<br />..'_~p:l}centr'at ion, is the r:is-~ in sal j'nity through
<br />:st_l'eamflow depletions _I<ttlich conC'-E!ntrate the.
<br />:,$a_lt'burden into a lesse"(" volume Qf water in,
<br />_:'t,he' fiver- syst61l,' Gi!Oerall'y. the application
<br />: ,of:: ir.rigation water_ resul.ts in increased salt
<br />::_<:;bncentratj.ons because or both _loading and,
<br />'FqnslIIlptive.use. The:salt load fluctuates .
<br />;"a~nually with the 'overafl Basin water supply,
<br />
<br />.. .
<br />'- . - - ' . .
<br />'-Ai the fo'l1owing graph- i-llustrates, since 1949'
<br />,t_he genera'} trend in salinity concentrations
<br />. at Imperial Dam has' been upward, and the
<br />projected'levels throu9h the year 2010 (with-
<br />'.ou_t water qual ity improvanent units)' are
<br />e-xJleded to follow the -oyera 1.1 ris ing trend,
<br />
<br />TI~e ;osses' associated' with municipal and
<br />-frio_ustrial 'use occur: primarily from increqsed
<br />"ilater'treatment costs, accelerated -pipe
<br />,_corrosion and dPpliance wear,' increased soap
<br />dnd detergent 'needs, and decreased water
<br />'-pa.-latabil-ity, . The EnvirOnmental Protection
<br />Agency -recommends' drinking' \Il~ter contain -no
<br />'_ mQr_e than 500 mg/l of TDS (-total dissolved
<br />'s9-lids). -
<br />
<br />OIRECi AGRICUlTlJRAl'LO'SSES
<br />./ $23,600 .
<br />//\~"~~.'..,' . ."
<br />'~GI~NAL- \
<br />1:-_.... - A.GR.ICULTURAl \
<br />. '_, lOSSES \
<br />!- ' $1~~:~00 \! -,
<br />~J )
<br />.-------
<br />',--------:-
<br />.---- MUNICIPAL AND INDUSTRIAL lOSSES
<br />5330,400
<br />
<br />1.:1%
<br />
<br />rOTAl i.OS.s :.. ~472,OOO iter mgjl (1981 dollars)
<br />
<br />~8fJ~
<br />
<br />"OO.~
<br />'00 "
<br />,
<br />~' I
<br />_ 000;-
<br />,
<br />l!l .00:......oIC ^ ^ ~
<br />~ 'JI_i' '----
<br />'0' ;"\ iJ ~
<br />"', "'0 _ ,
<br />g
<br /><l '00'"
<br />2'
<br />
<br />_:--,-
<br />
<br />/
<br />/
<br />/
<br />,
<br />,
<br />,
<br />,
<br />,
<br />
<br />__ _ ~..".... J.
<br />
<br />,,;,;'
<br />"0 ,~
<br />
<br />'"
<br />
<br />'~~~
<br />
<br />:J ..,<" ""'''''''' ,_...~."' ,...".
<br />
<br />The h~9h salt, lo,ad ~f 10 million tons annually
<br />entering lake Mead 1n the'Lower ColoradO R-iver
<br />,Basin adversely affects more than 10 million
<br />,people {Of 14.5 million total} and 1 million
<br />acres.of irrigated fannlano in the United
<br />States: O<rnages in_ the iIlIount of $472 000
<br />occur for each increase of 1 mg/L at I~perial
<br />DaJI. ..(n.lg81, danages were approximately ,
<br />S96 ml1110n. U,nless controls are implanented,
<br />the danages wuld rise to 5237 million by the
<br />year 2000. . ,
<br />
<br />In the-late 1960's and early 1970'_s leader's at
<br />the regional -and natiGnal level began to
<br />recog~ize the problem and seek solut ions,
<br />
<br />
|