Unexpected sedimentation patterns upstream and downstream of the Three Gorges Reservoir: Future risks

(整期优先)网络出版时间:2019-02-12
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Thispapersummarizesthelatestdevelopments,futureprospects,andproposedcountermeasuresofreservoirsedimentationandchannelscourdownstreamoftheThreeGorgesReservoir(TGR)ontheYangtzeRiverinChina.Threekeyresultshavebeenfound.(1)TheincomingsedimentloadtotheTGRhasbeensignificantlylowerthanexpected.(2)TheaccumulatedvolumeofsedimentdepositionintheTGRissmallerthanexpectedbecausetheoverallsedimentdeliveryratioisrelativelylow,andthedepositioninthenear-damareaoftheTGRisstilldeveloping.(3)RiverbedscourintheriverreachesdownstreamoftheGezhoubaDamisstilloccurringandchannelscourhasextendedtoreachesasfardownstreamastheHukoureach.Significantly,sedimentationoftheTGRislessproblematicthanexpectedsincethestartofoperationoftheTGRontheonehand;ontheotherhand,thepossibleincreasesinsedimentrisksfromdependenceonupstreamsedimentcontrol,depositioninthereservoir,andscouralongmiddleYangtzeRivershouldbepaidmoreattention.(1)SedimenttrappedbydamsbuiltalongtheupperYangtzeRiverandbilliontonsofloosematerialsonunstableslopesproducedbytheWenchuanEarthquakecouldbenewsedimentsourcesfortheupperYangtzeRiver.Moreseriously,possiblereleaseofthissedimentintotheupperYangtzeRiverduetonewearthquakesorextremeclimateeventscouldoverwhelmtheriversystem,andproducecatastrophicconsequences.(2)IncreasingsedimentdepositionintheTGRisharmfultothesafetyandefficiencyofprojectoperationandnavigation.(3)ThedrasticscouralongthemiddleYangtzeRiverhasintensifiedthedown-cuttingoftheriverbedanderosionofrevetment,ithasalreadyledtoincreasingrisktofloodcontrolstructuresandecologicalsafety.ItissuggestedtocontinuetheFieldObservationProgram,toinitiateresearchprogramsandtofocusonrisksofsedimentation.