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<br />~.39 FAX <br /> <br />140 J. $. Oovington and W. A. Hubert <br /> <br />Table 1~ Average summer wetted wJdths for eIght <br />study streamSI average deny f10ws (ADF) an'q period of <br />record for four gauged streams, and estimated ADF for <br />four ungauged streams in Salt River VeUey <br /> <br />Wetted Discharge (mB I~ec) <br />Str~~m width (n1.) ADF Period ~r record <br /> <br />Cau.~d sU"ea1U~ <br />SU'"awberry 8 l.95 193)-1943 <br />Swift 8 2:55 1943-1971 <br />CoottoQwood 7 L80 1933-1957 <br />Crow 8 1~9a 1947-1967 <br />Un.(g3"Uged .s(reams <br />U!'per SaJt 7 l~SO <br />Dry 6 O~6~ <br />Wi [Jaw 7 1.30 <br />Stw:up B OJi8 <br /> <br />~vift Creek \lIaS not Used because of the eft~c:ts of a <br />large s.prillg on disc:ha.rge, <br />We assumed that reductions from natural aYeragc <br />sumr.ner low flows would result in a linear decUne: in <br />bio1'naS5 of br-o\.vn c.rQUt (Wesche 19'14. 1'980, Ten'Ll1'.nt <br />1976, Jowett 1997). Tennant (1976) defined 10% of <br />average! daily flow (ADF) as a minimUID Ihnit [0 susmin <br />fish populations~ so we ~,~umcd t,har brovm troUt bio.. <br />ma..~ would be zero a~ 10% ADF. A'\Ierage na tul"al sUln- <br />mer flaws were esrimat~d to be 7.8% of AD,Ji 'Within the <br />study area. so we. assumed chat 100% of r.he me:t=lrl <br />biomass of brown trou.t w(Juld occur when 78% of ADF <br />was the: aVtrag~ summer flow (Tenn3.l~t 1976)~ We CCHn. <br />pUled a regression willi these Me) points to ob~Ain tl1e <br />equation that we 'I..1Sed to prom!; t tIle ptoportiona.( re.. <br />du c:tion in Inean bi 0 mass of [rOllt (%). from a ptOpO t""- <br />don of ADF (%): <br /> <br />Proportional redu.ction in bic'Jma.~.!-i :=; --14.71 <br /> <br />+ 1.47 (proportion of AOF) <br /> <br />Estimates for each reach W~ re S\.tM rned Ovc r each trib- <br />utary an d Eoe U ppe.- Salt .River to c:stimate biomass and <br />dtm.!$ity in ~ac:h SLTcat'l\; at diffetent ftows~ All eompu.ta- <br />tion.~ were perfonncd using a sprea~heet. <br /> <br /> <br />Application of Geographic jnformetlon System <br /> <br />Dar.a. we(.: c:onvertc:d tc) digital format for depiction <br />using a CIS. Dynamic segmentation '(.!(as u..r:;cd to define <br />U1C:: humogC'neou5 l't2ches on an emsong hydrography <br />covc;rage (E(]vironnlental Research SY5tems, Inc,. <br />1994a). Dam ,ver~ inlporr:.ed from a -5preadsbect Fi.le to <br />create an Arc/I.,ftJ (:ESRI. Redlands, California) at., <br />tribute. table for each rea.ch. ..A. customiJ{ed graphical <br />user interface was deveroped in he Vie\y S.l (.PC ver- <br />~jUQ) u~ing Avenue, an objecI-orient'cd scripting lao~ <br /> <br />II:bJ U.L.... <br /> <br />Table 2. Estimated biomass and densfty for reaches jn <br />study streams .and total slream esUmates or abundance <br />at natural average summer flows <br /> Reach I::.sr.Jnlale'S "totaJ ~trealll <br />Scream Mean R3.nge estimatc.ct' <br />Biol"ll~ (kg/ ha) <br />Sr:rawb~r.l'Y Creek ~.1 1 ~. ?-;3~.3 15fi <br />Willow Creek 2S,6 12.S-37~S 144 <br />Swift Creek 2!LO 1 L6-.3M.4 74 <br />Dry Creek 22.4- I 1.6-45.0 41 <br />Cottonwood Creek 2~t' 13.0-52..7 146 <br />U pp~r Salt 1Uver 23.5 9,,5--86/7 3S~ <br />CrotV Creek 25.0 9.3-$9.7 410 <br />StUJ'np CI"~elt. 1~t9 8.2-1 ;.0 64 <br />Dc:nshy (N/ha, <br />St1.id.wberry C"e~k 447 254-751 .9092 <br />WnJow Creek iBO 245-741 2826 <br />Swift Creek. 49Y 2~7-754 114.5 <br />Dry Greek 355 228-882 805 <br />COtlo&:l.wood Creek 662 2.54-1,,034 2B6D <br />Upper Salt Ri'Vtr 462 187-761 7487 <br />Crow Creek 487 180-778 H032 <br />S r.unrp Cl'"e~k 251 160-.8-20 1260 <br /> <br />j.E::dn1a(~ tOt i>ialn:t$S SI"e in kih;.gmfn:;- per" Ilr.;t:RfY': ~'frif1lftl~ for <br />dc~ity sr~ in Iltlm bct" per h ecure; ~u...d ~dm~te.5 fl?t' Lh~ t(JfAJ .sv"eatYi <br />~(t: .the nun\~r of 1;$11 QWl!!;'r !.il':: enth'o ::;tr'~m :,;.t:grncnt. AJI ~ti:ttU\tC'.5 <br />3rt: for brown trout ;::1 year old.. <br /> <br />guage (Environmental Research Systems, Inc.. 1994b). <br />Th is in terface allowed selection of specific srream <br />reaches and viewing of spa~ial disuihudons of ha.bitac <br />fe.atures and bro'Ylrl t,~U[ abunt.lancG es.timar~s. <br /> <br />Predictions tor Streem. Segments (n the Sait Rtver <br />Varley <br /> <br />Caw:r varied \Yidety over tbe length of the study <br />strc:arn.s,. whereas e]evationJl werted width. and Ghat':linel <br />gradient varied little. COnsequently, there was consld.. <br />erabte variation tn e.sd mated bi.oma..~s and abundan ce of <br />brown troUt among the .~eaches at natura] average 5um- <br />zner floM (Table 2). Figure 4 illustrates the longitudi- <br />n~al variation in estir.nated instrcanl cover at'ld brown <br />trout biomass and the clo.."ir: relationship bcnv~cn in... <br />4treatn cover a.n d brown lrour biomass for a portioll of <br />t.he tIpper Salt Rivet. Similar patterns. w(;r~ found <br />among :aU of the study streams. In reaches where in- <br />stream cover '1/as low (.5.2% of water. surface area" <br />brown trOUt biomass estlrl1ates wete JeS$ than 15 l(,g/ha~ <br />Convel"Sely, where instt'eam cover was moderately hien <br />(21 % J, brtnvn trOUt biomass estimates exceeded 30 <br />~/ha. <br />When re::lch estimates of bl"o\V1l trout biomass aIld <br />abundance at natt.lral aY~l"age $Umnlcr flows were <br />summed for dam st.\Zdy stteam~ esr:i~ate.s varied wi.d.ely <br /> <br />p.? <br /> <br /> <br />