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<br />Selenium in Western Colorado
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<br />Selenium. a nalUrally occurring trace element. is common throughout
<br />[he Wl:slem United Stales in marine \eJimcntary rock:,.. It is an essential
<br />mjcronutricnl for birds, fish. and animals (!\.tayland. 1994) but al high
<br />concemrations can be highly to:..ic 10 fish and wildlife. Selenium can be
<br />vcry mobile in tht;> environment and the mobility can be accelerated by
<br />Irrigation. As inigation water i.. appli~d 10 soils cuntaining "denium.
<br />the selenium i~ leached out of the soib and into surface and ground
<br />Water. Selenium in wetlands. pond:'>. and lakes is incorporated into bc-d
<br />sediment and can be bioaccumuhtted by wildlife. including fish and
<br />hird~ (Ohlendorf and others. 1986;. Areas of the Western United State...
<br />susceptible to seh.-nium contamination from irrigation. which include
<br />me Grand and
<br />Uncompahgre Val-
<br />leys in western Colo.
<br />rado, have been
<br />identified by Seiler
<br />and otlwrs (1999).
<br />Extensivcirri.
<br />gated agriculture if.
<br />present in me Grand
<br />and Uncompahgre
<br />Valleys of the Colo-
<br />rado Plateau in we"t.
<br />,'~~:'" em Colorado (tlg. 6),
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<br />v.'-- ,~ Irrigation drainage
<br />· J:.::kIto from these areas may
<br />, account for as milch
<br />1 ~uwn ~ - ~,: as 75 percent of the
<br />~ GrMd ~ <ielenium load in the
<br />~V""'" V*J t_
<br />5_. 7_' ColorJdo Rivt'r near
<br />'o.l<I!",.,,8uee<..-dOlhel$..liXl6 the Colorado-Utah
<br />State line (Butler and omers. 1996). II is estimated that 61 pCf(.'ent of the
<br />selenium load to Lake Powell in Utah onginates from these agricultural
<br />areas in me UeOL (Engberg. 1999). Primary source areas of selenium
<br />in wt'slem Colorado are the western one-half of the Gmnd Valley and
<br />the e.!'>lem ....ide of the Uncompahgre River Valley where lht' re:o.idual
<br />soils and alluvium arc denved primarily from the ~1anco" Shale, a
<br />marine shale containing selcnium.
<br />A :o.ludy in 1991 ~9J of irrigation drainage in the Grand and
<br />Uncompahgre River Valleys detected relati\cly high concentration" of
<br />selenium in many surfal.'C-\\'alL'r and strcambt'd-sl..-dimcm .samples
<br />(Butler and others, 1996). Concentrations of selenium greater man the
<br />aquatic-life guidelincs were also delected in the liCOL surface-watcr
<br />sampling in agricultural an~a.. during 1995-98 and at (,me strt'amhcd-
<br />sediment -;ampling site in 1995. lnwstigation.s of selenium in we!>!L'Ol
<br />Colorado for remediation planning are continuing through the U.S,
<br />DepartmL'nt of the Interior National Irrigation Water Quality Program
<br />and thc Gunnison Basin Selenium Ta..k Force.
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<br />SURfACE WATER
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<br />Water.Quality Characteristics
<br />of Agricultural Areas
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<br />Agrkultural land u'-e con,-titule,
<br />abuut 5 perc<..'1ll of thc Study Cnit
<br />area I fig. h L Within lhe Southern
<br />Kllcky ~t\1Ul1lain~. agric.ultural land
<br />J' almlht e\du~l\'dy hay mead-
<br />O\\~. The agn<..:ultulal ale~b of the
<br />ColoraJo Plal\.'au lprlnnp'-llly the
<br />Gr~lIlJ Valley lll'ar Grand Jllll<..:tion
<br />III .\ll''-:I Ct\Ul1t~ and {ill'
<br />Un<...llmpahgr\.' \.alky n\.'ar Ddla
<br />and .\Iplltro~\.' ill lJe1t;.t Jilt! ~lun-
<br />trt)~C Coulltie~. fig. hj rrlldui.."c h<.ty.
<br />corn. ,,>mall gr.ll/h. Jr~ hean'-.
<br />union,. llldon,. fruit. anJ grapt::-..
<br />Th~ Gr.mJ VaJlc~ h.l~ ;lhllU( 70.0UO
<br />a<..T\.'~ uf irri~al<...d land, anJ lhe
<br />Un<":lIrnp.lhgr~ \'al1\.'~ c"l1tain..
<br />ah\luI I'III.II()/) Irrigat<..'d 3<.."I'l" Illutkr
<br />and ullla,. t 99ft I, The market
<br />\'alll~ of agri<...llltural producb prn-
<br />duced III [)dlil. .\1~'-a. anJ .\lon-
<br />110,\.' C,'U1HIl"' \\i1~ ~lhl)Ul 1-15
<br />1l1lJliun dulJar<; in Jql'~ I HuTt.,;)u of
<br />lhl' C\'n,us. 199-11. 1\:,ticiJl'~.
<br />nutrient:-.. <lIlJ ~eJilllcllt art' water-
<br />'lualilY i"u\.'~ \,:tlllllllonly a"l\<..'i.
<br />at\.'d with aglll"lJlttJral land u~c:,
<br />I't"tkidt., \\ l'n' S;lIl1l)lt'd in dir-
<br />l"t'n'lIl Illl'dia, l'e'tkiJ('~ WCTl'
<br />1Il\<..'~tig,ll\.'d in ~urf.l<...c water by
<br />peri,lt,lic tllllrlltnring at ~ agricul-
<br />lur;tl ,lIC' and a 0111>tll11(' ,ynoptk
<br />~<lll1rJing al -L~ agrkultural sile~_
<br />Fi...h \\ ere colJcded ')11<":(' al lhrce
<br />agn<...ultural 'ltl'~ <lIlJ Ih\.' Ih<iUl'~
<br />analY/cd for ,)rgal1ot.:hlnrine re:-,ti-
<br />tiJe" Orgalllll'hlllrinl' [X"ticIJ<.." in
<br />~tr\.'arnbeJ 'c:JIlTlent' \\erc ..ampled
<br />(IIKt.' al ~i\ agrlculrural ,ile,.
<br />GnlunJ.W;Jtl'1 ';lInrk'~ ,..ere nol
<br />l.ol!eCll'd III tht.' ilgriculrural ar('a~
<br />of the L'COL net.:.llbc ground water
<br />I" genl'rillly Ill)l u~t.'d fw public
<br />water :-,urpty illlhe~(' ,lrea,.
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<br />.\ 1aJur Finding' 15
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