文档介绍：SeverityLevelofNo-flowEventsintheYellowRiverZhenghanQian1,2,JinrenNi1,2,AnXue1*2,SilkeWieprecht3/DeptofEnvironmentalEngineering,PekingUniversity,Beijing100871,ChinaTheKeyLaboratoryofWaterandSedimentSciences,,KoblenzI)・56068,GermanyAbstract:Withthemeasureddataonno-floweventsintheLowerYellowRiversince1972,thispaperpresentsanapproachtodescribetheno--,ingwaterfromupstreamanditsvarianceiswellestablishedwithaBP-work(ANN),-:YellowRiver,no-flowevent,severitylevel,classification,ANNIntroductionNo-floweventsintheLowerYellowRiverhavecausedalotofimpositionsonsociety,economyandeco-urrencein1972(Xu,2002).Thecausesofno-floweventsaremany-sided,whichispossiblyrelatedtothevariationofnaturalconditionssuchasclimatechange(Caruso,2002;MimikouetaL,2000),butitmightbemoreimportantlyrelatedtohumanactivities(Dakavaetal.,2000;Ren,1999;Xu,2002).Owingtothevarietyofdirectimpacts,low-,eintermittent(Smakhtin,2001).No-flowevents,withzerodischargeinthechannel,,whicharelocatedinaridorsemi-aridregions,suchastheNileRiverandColoradoRiver,haveundergoneasubstantialrunoffdecreasedownstreamaftertheconstructionofdamsanddiversionworksintheupperreach(aL,1992;Petts,1984).Nevertheless,itisunusualthatalargeriverliketheYellowRiverissufferingfromtheimpactofno-(Dakavaetal.,2000;Gottschalketal.,1997;Smakhtin,2001).However,onlyfewstudieshavebeenconductedonno-,