TheDujiangyanDam,45kmnorthofChengdu,isanancienttechnologicalwonderofthecountry.Morethan2000yersago,LiBing(250-200BC),asalocalgovernoroftheShuState,designedthiswatercontrolandirrigationdamandorganizedthousandsoflocalpeopletocompletetheprojecttochecktheMingjiangRiver.Formanyyearstheriver,floodedtheChengduagriculturalareaandlocalfarmerssufferedalotfromthewaterdisaster.Duetothesuccessoftheproject,thedamautomaticallydivertstheMingjiangRiverandchannelsitintoirrigationcanals.Formanyyearsthedamhascontinuedtomakethemostofthewaterconservancyworks.

　　Expansionhasbeenundertakensince1949andatpresentthesystemdoesagoodjobofirrigatingfarminglandacross33countiesofthewesternpartofSichuanProvince.Localpeoplefeelproudofthesystembecaudeithassupportedalargeamountofpeopleintheirdailylife.

　　Whatmakesthissystemsogood?

　　Thesystemisalargehydraulicwaterprojectwhichconsistsofthreemainparts:theFishMouthWater-DividingDam,theFlyingSandFence,andtheBottle-NeckChannel.

　　TheFishmouthfunctionstodividetheflowofwaterintoaninnerriverandanouterriver.Longago,whenLiBingworkedasthelocalgovernoroftheShuState,hefoundtheoldrivercanalwastoonarrowtoholdmuchwater,whichoftenoverflowedthebanksandcauseddisastrousflood.Basedonnaturalgeographicconditions,heorganizedthepeopletobuildaman-madedam.Thewholedamlookslikeafish,andthefrontdamhasacircularconeshapedlikeafishmouth.Itisthedamthatchannelswaterintoanoutercanalandaninnercanal.Theouterwatercanalfunctionsasthemainstreamandholdssixtypercentofwaterintheriver.TheextrawatergoesthroughtheinnercanalforirrigationinChengduareas.

　　TheFlyingSandFencejoinstheinnerandoutercanals.Thefencefunctionstocontrolltheflowofwateranddischargeexcessintotheinnercanalfromthemainstream.Duringthedryseasonthefencedoesn'tworkmuch,butwhenfloodsoccur,theriverrushesforwardalongtheoutercanal.Asitapproachesthefence,thefence,theriverbeginstoturnroundfastandsoonmanywhirlpoolsareformed.Thevolatilewhirlpoolssweepawaysandandpebblesand,throwthemintotheoutercanal.Formanyyearshugebamboobasketswereusedasthefence.Theywerefilledwithstonesandpebbles.However,atpresent,reinforcedconcreteweirhasreplacedtheancientfence.

　　Sonow,let'sdiscusstheBottle-NeckChannel.Atrunkcanalwascutthroughthemountainintotwopartswhichlinkuptheinnercanalforirrigation.ThesmallpartislatercalledLiDui,whichmeansanisolatedhill.Chengdulookslikealargebottleandthetrunkcanalbetweenthemountainandthehilltakesshapeofthebottleneck.Thetrunkcanaltechnicallyhastwofunctions:First,itleadsthewatertoirrigatethefarminglandinwesternSichujan;Secondly,thetrunkcasnalworkstogetherwiththeFlyingSandWeirtokeeptheflowbelowacertainpointintheinnercanalduringfloodseason.Somestonetablets,whichstandontheisolatedhill,areengravedinBuddhistSanskrit.ThelocalpeoplehopethattheBuddhisttabletscanexerttheBuddhistsuperpowertoharnessflooddisaster.Forovertwothousandyears,infact,theFishMouthWater-DividingDam,theFlyingSandWeir,andtheBottle-neckChannelautomaticallyworktogethertocontrolfoodsandsweepawaysandandstonesinthemai