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Simulated multi-scale watershed runoff and sediment production based on GeoWEPP model

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Simulated multi-scale watershed runoff and sediment production based on GeoWEPP modelon,and,based,Based

    Simulated multi-scale watershed runoff and sediment production based on GeoWEPP

    model

    Availableonlineatwww.sciencedirect.com

    ,

    ,ScienceDirect

    InternationalJournalofSedimentResearch24(2009)465-478

    Simulatedmulti.scalewatershedrunoff

    andsedimentproductionbasedonGeoWEPPmodel

    YUXinxiao,ZHANGXiaomingandNIULili

    INT1RNATIONAL

    JOURNALOF

    SEDIME卜丁T

    RESEARCH

    Abstract

    TherunofrandsedimentyielddatafromtheQiaozidonggou,Qiaozixigou,andLu'ergouwatersheds,

    intheLoessPlateauofChinaareusedtocalibrateandvalidatetherunoffandsedimentyield simulatedbvGeoWEPPmodeIoftheWEPPModelatwatershedscale.Theindicesofrelativeerror,R,

    correlationcoefficient,R,andNash.Suttclifreefficiencycoe

    cientEnareusedtoevaluatethe

    mode1fit.TheCCO

    hydrologicalresponsesintheLuoyugouandLu'ergouwatershedsarealsoforecast basedontheWEPPMode1.Meanwhile.therelationbetweenvegetationpaRernchangesandsediment

    yieldinthewatershedisdiscussed.andtheresponsesofrunoffandsedimentyieldinthewatersheds

    concerningforestgrowthstagesarestudied.Theresultsshowthattherelativeerrorsofsimulated

    valuesofrunoffandsedimentyieldarebelow30%.thecorrelationcoe

    cientsareabove0.9O.and

    theNash.Suttclifieefficiencycoe

    cientsarcabove0.80.Thesimulationresultspresentsatisfactory

    performance.thus.themodelcouldbeusedtosimulatetherunofrandsedimentyieldinthesesmall

    watersheds.Itisalsoobservedthatsoilerosiontendedtobecomesevereasprecipitationincreasedin

    thewatershed.whilesoilerosionhasadecreasingtrendasforestcoverincreasesandvegetation

    pa~emisoptimized.?

    enthewatershedisfullycoveredbyforest.erosionandsedimentyieldare

    minimized.Whentheforestcoverisabout30%andevenlydistributedinthewatershed,theerosion

    intensityislowerthaniftheforestcoveriscollectivelydistributedinthewatershed.Erosionvaries

    withdifFerentforestgrowthstagesinthewatershed;itismoreseriousattheyoungandnearplanting

    stageandisthesmallestatthematureforeststage.

    KeyWords:GeoWEPPmodel,Eco

    hydrologicalresponse,Watershedrunoif,Sedimentyield,

    Modelcalibration,Erosionmodeling

    tedijsrc

    1Introducti0n

    Thestudyofeco..hydrologicalprocessesfordifferenttime..spacescalesandseriesofenvironmental

    conditionsisoneofthefocifortheMAB(ManandBiosphere)andtheIHP(InternationalHydrological

    Program)researchprograms(Janaue~2000,Tianeta1.,2007,Wgeta1.,2008).Theresearchon

    eco.hydrologicalprocessesatthewatershedscalecombineshydrologicalelementsandthebiological

    systemespeciallyforvegetation(Weieta1.,2008),withtheaimtoachieveasustainableecological

    systemintheLoessPlateauofChina.andthenrevealstheevolutionprocessandmechanismsamongin

    responsetothedrivingforcesofhumanactivesandnature(Osterkampeta1.,2007,Zalewski,2000,Fang

    eta1.,2008).Therefore,theestablishmentofeco.hydrologicalmodelplaysacrucialroleinthede

    Prof.Dr..KeyLaboratoryofSoilandWterConservationandDesertificationCombating,MinistryofEducation,

    SchoolofSoilandWaterConservation,BeijingForestryUniversity,Beijing100083,China,Email:

    ,

    yuxinxiao@bjfu.edu.ca

    Dr.ChinaInstituteofferResourceandHydropowerResearchBeijing100048.China

    Dr.,KeyLaboratoryofSoiland

    ?,aterConservationandDesertificationCombating,MinistryofEducation, SchoolofSoilandWaterConservation.BeijingForestryUniversity,Beijing100083.China Nore:TheoriginalmanuscriptofthisPaDerwasreceivedinAug.2008.TherevisedversionwasreceivedinAug.

    2009.DiscussionopenuntilDec.2O10.

    InternationalJournalofSedimentResearch,vo1.24,No.4,2009,PP.465-478465

    塑一

developmentofeco

    hydrologybecauseitcouldbeRerillustratetheintrinsicmechanism(Xiaeta1..2004. Yaneta1.,2005,Mekouneneta1.,2007,Alekseevskiyeta1.,2008).Atpresent,hydrologica1modelsat

    watershedscalearegenerallyclassifledintotwotypes:lumpedanddistributedmodels,theformermainly

    includes:(1)theXinAnjiangmodelbelongstothegroupthatisappliedtosimulateeco.hydrologyinthe

    watershed(Wangeta1.,2001;Zhang,1994);(2)modelsfocusingonlpeal1andunitstosimulate

    eco.hydrologicalprocesssuchastheW_AVES(Huangeta1.,200l1,SWIMV2.1,PATTERN.SPAC(soil

    plantandatmospherecontinuum).andSVAT(soilvegetationandatmospheretransmission)modelsthat

    simulatethevegetationinter-phaseprocess(Wangeta1.,2001,IUGG1999);f3)modelsapplicableto

    foresteco

    hydrologicalprocessessuchasRITTER,MASSMAN,Gash,Dalton,DCA(Distributed CommunicationArchitecture),Philip,andsoon(Zhangeta1.,2003).Withregardtodistributedmodels,

    tlleyconsideradequatelythevarl'abilityofhydrologicalparametersspatially,and,thus,couldbetterdeal

    withthehydrologica1responsesatasmallsparialscale.Researchondistributedmodelsbeganin1969

    whenFreezeandHarland(FreezeandHarland,1969)publishedthearticle''theblueprintofadistributed

    physicallybasedmodellingsystem''.Subsequently,W

    geta1.(20o4)amongothersproposed

    improvementstodistributephysicallybasedmodeling.JeffArnoldandhiscolleaguesdevelopedthe

    S,ATmodel(Neitscheta1..2000).Gragsoneta1.proposedtheTHALESmodel(Yangeta1..2004).

    YangandHerath001)developedalarge.scaledistributedmodelbasedona10kmnetwork,other

    distributedmodelsinclude:theUSGSmodel,WATFLOODmodel,SLURPmodel,PRM,Vicmodeletc.

    WEPPisacomputermodelwhichcansimulatethemostcomplexphysicalprocessesrelatedtosoil

    erosion(Nearingeta1..1989).Itissuitabletostudysystematicenvironmenta1variationsandtheir

    responsetohydrologica1changes.AmericanscientistscombinedWEPPwithaGeographicalInformation

    System(GIS).developingtheGeoWEPPmodel.henceenlargingtheapplicationscopeof,?

    EPP(Zhang

    eta1..2004a).,^PPhasbeenusedforthepredictionofsoilerosionduetorainfallandrunoft.Ithasbeen

    usedforsimulationofnon-pointpollution(Niueta1.,2001)anderosionpredictiononthesoilslope

    surface(Cheneta1.,2003).Meanwhile.ithasalsobeenappliedtocomparevarioussoilconservation

    schemesintheLoessPlateaufMo,2004).Chinesescholars(Leieta1.,200l:Zhangeta1.,2004b;Miaoet

    a1.,2004)haveresearchedverificationandcalibrationofthemodel,andtheyhaveanalyzedtherelatively

    importantparametersoftheWEPPmodel(J.M.Lafien,1997).

    Thestudyrepoaedhereselectswatershedrunoffandsedimentyieldtakenfromtypicalwatershedsin

    theLoessPlateautocalibrateandverifythesimulatedwarershedrunoffandsedimentyieldbyGeoWEPP

mode1.ThecomplexityofsoilcompositionandclimateintheLoessPlateauregionaddtodi

    cultyof

    typicalapplicationofthemode1.Anddifferenttypica1watershedelementsfromtheGeoWEPPmodelare

    adoptedtoprovidescientificbasesformtionaIlayoutofforestvegetationtocon~olsoilerosionproblems

    intheLoessPlateauregionwhereagriculturalproductionisamajorsourceofemployment. 2Methodology

    2.1Thegeneralconditionsoftheregionunderstudy

    ThecityofTianshuiisakeyregionandalsoasensitiveoneinthewestofChinaecologicalsystem.

    Tianshuiis1ocatedinthesoutheasternpartoftheGansuProvince.Itissituatednearthecommon

    boundaryofShaanxi.GansuandSichuanprovinces.Itislocatedat104.35'to106.44'Elongitude,and

    34.05'tO35.l0'Nlatitude.TllisregionstretchesacrosstheYangtzeRiverandtheYellowRiver.It

    includesaportionofthewleiheRivercatchmentoftheYellowRiversystemandwestQinlinMountainis

    takenasthedivideinthenortherndirection.TheTianshuiregionbelongstothethirdsubregionofthe

    LoessHillyandGulliedregionoftheLoessPlateau.ThestudyareaincludesfourwatershedsLu'ergou.

    LuoyugouandQiaozidonggouandQiaozixigou.witIldifferentsizes.Thelpcationsofthesefour

    walcershedsareshowninFig.1.TheLu'ergouwatershedissituatedsouthofTianshuiwithalong.narrow

    beltshape,whichcoversanareaof12.01km.TheLuoyugouwatershedissituatednorthofTianshui.and

    itsgullysystemiSdk,;tributedinafeathershapeandcoversanareaof72.79l(rTTheQiaozidon

ggou

    watershedhasasemi.feathershapeandcoversanareaof1.36km.andtheQiaozixigouwatershedhasa

    feathershapeandcoversanareaOf1.09kin~.Themaintopographiccharacteristicsofthefourwatersheds

    arelistedinTable1.

    Theclimateofthese4watershedsiswarm,andhasevidentdifferencesindifferentseasons.Theaverage

    ..

    466..InternationalJournalofSedimentResearch,Vo1.24,No.4,2009,PP.465_478 annualprecipitationiS491mm.TheextremehightemperatureiS38.2?andtheextremelow

    temperatureis.17.4?.Thesoiltypesinthesewatershedsaremainlythemountgrayloamysoil,loess

    graysoil,andtheloessloamysoil.ThesesoiltypesarerepresentativeintheLoessPlateauregion.All

    treesareplantedbyhumans.ThemainspeciesareS8}

    maIsudamaRoidz,Robniapseudoaccaeia,Pines

    cabulaeforaiesplalyeladusorientates,Populusdavidiana,USpumila,andPrunusarmoniaccvar.

    anses.Theshrubsgrownaturally,andthemainspeciesaresophoravieiifaliahouses,Arunorphia

    fruiticosa,lemthoxynumbungtanumMaxim,etc.Orchardsincludemainlyapple,apricot,pear,peanuts,

    etc.

    Fig.1Locationsofwatershedsunderstudy

    Mea1)SlopeDifiefenceDeI1sity

    NameofAreaShapeofLengthofwidthofShape1ninof

    watershedLocation(km2)watershedwatershedwatershedcoefficientgullyelevationgullies

    (km)0on)(%)(m)(km/km2)

Northof72

    .

    79Feather

    LuoyugouTianshuishaped21.633-37O.112.52753.54

    SouthofNa~ow

    Lu'ergoul2.01beltTi

    anshui6.911.739.257.2l5323.82

    shaped

    InsideS

    emifanQiaozidonggouLuoyugoul-36

    watershedshaped2.0OO.650.348.O3775.13

    InsideF

    eatherQiaozixigouLuoyugou1

    .O9

    watershedsbaped2.18O.5OO_238.03775.O9

    2.2Methodology

    2.2.1GeoPPmodel

    TheGeoWEPPmodelcombinestheWEPPmodelwithtopography,landuseandsoilpropertiesinaGIS

    topredictsoilerosioninthewatershed.InordertopredictsoilerosionusingtheWEPPmode1.itis

    necessarytosupplytherelevantinputdata.

    InternationalJournalofSedimentResearch,Vo1.24,No.4,2009,PP.465_478..467.. GeoWEPPincludes3parts:GISmodel;TOPAZ:andTopWEPRItsfundamentalprocessesareas

    follows.Firstly,establishthegraphsofadigitalelevationmap(DEM),landuse,andsoildistribution

    throughuseofthefunctionofspatialanalysisinArcView3.2.ThenanalyzetheDEMdatabyusing

    TOPAZafterthedataareinputtoGeoWEPPwiththeaimofforminganaccordantiunctionnet

workin

    thewatershed.Subsequently,overlaylanduseormanagementwhichrer)resentslandu,seplanningand

    practicesunderhumanactivities.soilmaps.andtheDEMtoproducethebasicunitofthewatershed.That

    iS,subcatchments(Fig.2).Finally,inputtheparametersofsoilandvegetationinthesub

    catchments

    underTop?Pandruntheprogramtoobtainthesimulationresultsig.31.

    Fig.2Theprocessofcreatingasub-catchment

    Fig.3TherunningprocessofGeoWEP

    ll

    2.2.2Evaluationofindicesofmodel-fitquality

    Inthisstudy,thetelativeerror,R,the1inearcorrelationcoecient,R,andthemodel-fitefficiency

    coefficient,En,oftheNashandSutcliffe(1970)areselectedtoevaluatethequ~ityofthemodel application.TherelativeerroriScomputedasfoUows:

    p一门

    R=—兰X100%

    Qr

    whereP1isthesimulatedvalueandOistheobservedvalue.

    Thelinearcorrelationcoefficient.R.canbefoundbythelinearregressionmethod.Rcanbeusedto

    furtherevaluatethecoincidencebetweentheobservedthesimulatedvalueswhereR=0meansthetwo

    valuescoincideperfectly,andwhenR<1,thelowervaluereflectsthelesserdegreeofagreement

    betweenthesimulatedandobservedvalues.

    ..

    468..InternationalJournalofSedimentResearch,Vo1.24,No.4,2009,pp.465-478

    TheformulafortheNashandSutcliffecoefficientofmodel

    fitefficiency,En,isgivenasfollows

    ?(Q,)

    En1{=L——一

    ?(一‰)

    wherepistheobservedvalue;pisthemeanobservedvalueandnisthenumberofobservations. WhenQr=P,,En=1.isthefractionofthevarianceintheobservationexplainedbythemodel,a highvalueindicatesanaccuratemode1.

    Inmisstudy,threewatershedsareselectedtocalibrateandverifytheGeoWEPPmodelparameters:

    Qiaozidonggou,Qiaozixigou,andLu'ergou.ConsideringthatQiaozidonggouandQiaozixigouaresub

    watershedsintheLuoyugouwatershed,whiletheLu'ergouwatershed,isanindependentwatershed

    exclusiveoftheLuoyugouwatershed.thisstudyshouldbeaninterestingtestofthemodelandcalibration.

    Inordertomakecalibratedparametersaccurateandreliable.theperiodfrom1985tol990ischosenfor

    theQiaozidonggouandQiaozixigouwatershedsasthecalibrationperiodtosimulatethehydrological

    processintheLuoyugouwatershed.andtheperiodfrom1991to2004ischosenforvalidation.With

    respecttotheLu'ergouwatershed.theperiodfrom1982tol986ischosenforcalibrationtosimulatethe

    hydrologicalprocess.andtheperiodfroml987to2004ischosenforvalidation. 2.2.3Thesimulationofhydrologicalresponses

    ThestudyreportedhereappliestheGeoWEPPmodeltoautomaticallyextractthehydrologicalelements

    fortheLuoyugouandLu'ergouwatershedstodeterminetypicalwatershedelementsatvariou

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