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1、Relationsbetweentriazineflux,catchmenttopographyanddistancebetweenmaizefieldsandthedrainagenetworkF.Colina,*,C.Puecha,G.deMarsilyb,1aUMR“Syste`mesetStructuresSpattiaux”,Cemagref-ENGREF500,rueJ.F.Breton34093,MontpellierCedex05,FrancebUMR“StructureetFonctionementdes
2、Syste`mesHydriquesContinentaux”,Universite′P.etM.Curie4,Pl.Jussieu75252,ParisCedex05,FranceReceived5October1999;revised27April2000;accepted19June2000AbstractThispaperputsforwardamethodologypermittingtheidentificationoffarmingplotscontributingtothepollutionofsurfac
3、ewaterinordertodefinethezonesmostatriskfrompesticidepollution.Weworkedatthescaleofthesmallagriculturalcatchment(0.2–7.5km2)asitrepresentstheappropriateleveloforganisationforagriculturalland.Thehypothesistestedwas:thefartherafieldundergoingapesticidetreatmentisfrom
4、achannelnetwork,theloweritsimpactonpollutionatthecatchmentoutlet.Thestudyarea,theSoussoncatchment(120km2,Gers,France),hasa“herringbone”structure:50independenttributariessupplythemaindrain.Pesticidesalesshowthatatrazineisthemostfrequentlyusedcompoundalthoughitisonl
5、yusedfortreatingmaizeplotsandthatitsapplicationrateisconstant.Intwowinterinter-stormmeasurementexercises,triazinefluxvalueswerecollectedatabout30independentsub-basinoutlets.Thecontributoryareasaredefined,withtheaidofaGIS,asdifferentstripsaroundthechannelnetwork.Th
6、ecorrelationbetweenplotsundermaizeincontributoryzonesandtriazinefluxatrelatedsub-basinoutletsisstudiedbyusingnon-parametricandlinearcorrelationcoefficients.Finally,themostpertinentcontributoryzoneisassociatedwiththebestcorrelationlevel.Acatchmenttypology,basedonas
7、lopecriterion,allowsustoconcludethatinsteepslopecatchments,thecontributoryareaisbestdefinedasa50mwidestriparoundthechannelnetwork.Inflatzones,theagriculturaldrainagenetworkisparticularlywelldeveloped:artificialdrainsextendthechannelnetworkextractedfromthe1/25.000s
8、caletopographicmap,andthetotalsurfaceareaofthecatchmentmustbetakentoaccount.q2000ElsevierScienceB.V.Allrightsreserved.Keywords:Pesticidecatchment;GISart
