March20thisWorldWaterDayeveryyear.AccordingtoareportfromtheUnitedNationsmorethanhalfoftheworld'smajorrivershaveseriouswaterlossandarepolluted.TheYellowRivertheworld'sfifthlongestriverwateredsomeofth

　　March20thisWorldWaterDayeveryyear.AccordingtoareportfromtheUnitedNationsmorethanhalfoftheworld'smajorrivershaveseriouswaterlossandarepolluted.

　　TheYellowRivertheworld'sfifthlongestriverwateredsomeoftheoldestfarmsonearth.Butnowithasaseriousproblem.   1.   Inmostofthepast35yearsitdidn'treachthesea.

　　TheNileinEgyptrunning6650kmisthelongestriverintheworld.2.Nowitisdownto2billionm'orso. Australia'sMurrayRiverreachestheseaonlyeveryotheryear. OnefifthofAmerica'sRioGrandehasnowatereither.

　　____3.   

　　Mostlyit'sdamming(筑坝)andglobalwarmingthatmakeriversdry.

　　____4.   Nowabout45000ofthemlieacrosstheworld'srivers.Theyholdbackaround15%oftheworld'sfreshwaterfromrunningtothesea.

　　Globalwarmingismakingthingsworse.Warmerweathertakeswateraway. Theglacier(冰川)arebecomingsmaller.  5.   Globalwarminghashadcertaineffectsonwatersources(源头).Droughts(干旱)happeningaroundtheworldmakepeoplepaymoreattentiontothisfact.

　　A.Damsholdwatertoirrigate(灌溉)fieldsandmakepower.

　　B.ThesourceoftheYellowRiverisdryingupbecauseofit.

　　C.Itusedtocarry32billionm'ofwaterayear.

　　D.Howdoesithappen?

　　E.Factoriespourwastewaterintoriversdirectly.

　　F.ItssourceonQinghai-TibetPlateauisdryingup.