渠江富流滩船闸输水系统设计译文.docx

渠江富流滩船闸输水系统设计译文.docx

《渠江富流滩船闸输水系统设计译文.docx》由会员分享，可在线阅读，更多相关《渠江富流滩船闸输水系统设计译文.docx（9页珍藏版）》请在冰豆网上搜索。

渠江富流滩船闸输水系统设计译文

ⅠPlanningforWaterResourcesDevelopment

Planningcanbedefinedastheorderlyconsiderationofaprojectfromtheoriginalstatementofpurposethroughtheevaluationofalternativestothefinaldecisiononacourseofaction.Itincludesalltheworkassociatedwiththedesignofaprojectexceptthedetailedengineeringofthestructures.Itisthebasisforthedecisiontoproceedwith（ortoabandon）aproposedprojectandisthemostimportantaspectoftheengineeringfortheproject-Becauseeachwater-developmentprojectisuniqueinitsPhysicalandeconomicsetting,itisimpossibletodescribeasimpleprocessthatwillinevitablyleadtothebestdecision.Thereisnosubstitutefor"engineeringjudgment”intheselectionofthemethodofapproachtoprojectplanningbuteachindividualsteptowardthefinaldecisionshouldbesupportedbyquantitativeanalysisratherthanestimatesorjudgmentwheneverpossible.Oneoftenhearsthephrase“river-basinplanning”,buttheplanningphaseisnolessimportantinthecaseofthesmallestproject.Theplanningforanentireriverbasininvolvesamuchmorecomplexplanningeffortthanthesingleproject,butthedifficultiesinarrivingatthecorrectdecisionmaybejustasgreatfortheindividualproject.

Theterm“planning”carriesanotherconnotationwhichisdifferentfromthemeaningdescribedabove.Thisistheconceptoftheregionalmasterplanwhichattemptstodefinethemostdesirablefuturegrowthpatternforanarea.IfthemasterplanisinrealitythemostdesirablePatternofdevelopment，thenfuturegrowthshouldbeguidedtowardthispattern.Unfortunately,theconceptof“mostdesirable”issubjective,anditisdifficulttoassurethatanymasterplanmeetsthishighstandardwhenfirstdeveloped.Subsequentchangesintechnology,economicdevelopment,andpublicattitudeoftenmakeamasterplanobsoleteinarelativelyshorttime.Anyplanisbasedonassumptionsregardingthefuture,andiftheseassumptionsarenotrealizedtheplanmustberevised.Plansgenerallymustberevisedperiodically.

Anoverallregionalwater-managementplan,developedwithcareandcloselycoordinatedwithotherregionalplans,maybeausefultoolindeterminingwhichofmanypossibleactionsshouldbetaken.Butitmustalwaysbeconsideredsubjecttomodificationasthetechnological,economicandsocialenvironmentchangeorasnewfactualdatathataredeveloped.Amasterplanthatisnomorethancatalogofallphysicallyfeasibleactionsislikelytoproveoflittlevalue.

Planningoccursatmanylevelswithineachcountrywiththepurposeandnatureoftheplanningeffortdifferingateachlevel.Manycountrieshaveanationalplanningorganizationwiththegoalofenhancingtheeconomicgrowthandsocialconditionswithinthecountry．Evenifnosuchorganizationexists,thenationalgoalsremain,andsomeformofnationalplanningoccursinthelegislativeorexecutivebranchesofgovernment.Thenationalplanningorganizationwillrarelydealwithwaterproblemsdirectly,butinsettinggoalsforproductionoffood,energy,industrialgoodshousing,etc,itmayeffectivelyspecifytargetsforwatermanagement

Toallowfordifferencesbetweenthevariousregionsofthecountry,regionalplanninggroupsmayexistandequivalentregionalwaterplanningmayoccur.However,anatural“region”forwaterplanningistheriverbasinandthetendencyistocreateriverbasincommissions,orriverbasinmanagementunits（authorities）.Thesegroupsmustassurecoordinationbetweenthevariousactivitieswithintheriverbasin.Eachspecificactioninwatermanagementislikelytohaveconsequencesdownstream（andsometimesupstream）,andthusthesespecificactionsshouldnotbeplannedinisolationbutmustbecoordinated.

PlanningOfspecificactionsisthelowestlevelofplanning,butitisatthislevelthatimportantdecisionswhichdeterminetheeffectivenessofwatermanagementaremade.Thislevelisoftencalledprojectplanningalthoughaphysicalprojectmaynotnecessarilyresult.Forexample,astudyleadingtoaplanforflood-plainmanagementisalegitimateprojectplan.

Projectplanningusuallypassesthroughseveralphasesbeforethefinalplanemerges.Ineachcountrythereisaspecifiedsequencewithspecificnames.Thefirstphaseorreconnaissancestudyisusuallyacoarsescreenintendedtoeliminatethoseprojectsoractionswhichareclearlyinfeasiblewithoutextensivestudy,andhencetoidentifythoseactivitieswhichdeservefurtherstudy.Followingthereconnaissancephasemaybeoneormorephasesintendedtothoroughlyevaluatethefeasibilityoftheproposedactivityandintheprocesstoformulateadescriptionofthemostdesirableactions,i.e.theplan.Inmanycasesasinglefeasibilitystudyisadequatebecausethenatureoftheactionisrelativelyeasilyevaluated．Inothercasesoneormorepre-feasibilitystudiesmaybeundertakentoexaminevariousaspectsoftheproposal.Theideaofseveralsequentialstudiesistoreduceplanningcostsbytestingtheweakestaspectsoftheprojectfirst.IftheProjectiseliminatedbecauseofsomeaspect,theexpenseofstudyingallotheraspectswillhavebeenavoided.IftheSeriesofstudiesisallowedtobecomeaseriesofincreasinglymorethoroughreviewsofallaspectsoftheproject,thecostmaybeincreasedbecausemanythingswillhavebeenredonetwoormoretimes.

Thefeasibilitystudyusuallyrequiresthatthestructuraldetailsofaprojectbespecifiedinsufficientdetailtopermitanaccuratecostestimate.Inthefinalphaseoftheeffort,thedetailsofdesignmustbeexaminedcarefully,andtheconstructiondrawingsandspecificationsproduced.Although,inPrinciple,theissueoffeasibilitywasdecidedonthebasisofthefeasibilitystudy,thepossibilityalwaysexiststhatthemorethoroughstudymaydevelopinformationthataltersfeasibility.Consequently'thedecisiontoproceedshouldnotbemadeirrevocableuntilthefinaldesigniscomplete.

ⅡEngineeringEconomyinWaterResourcesPlanning

Waterresourcesplanninginvolvesmanychoicesamongphysicallyfeasiblealternatives.Generallyspeaking,eachchoiceamongalternativesshouldbemadeoneconomicgrounds.Eachalternativethatisgivenseriousconsiderationshouldbeexpressedinmoneyunits,beforethechoiceismade,Infact,unlessalternativescanbeexpressedinmoneyunits,theitemsinvolvedinsuchchoicesareincommensurable.Forinstance,themoneyunitistheonlymeasuringunitthatcanbeappliedtosuchdiverseitemsassteelpipe,kilowatt-hoursofelectricity,hoursofskilledandunskilledlabor,andreductionofthehazardofflooddamages.

WritersonengineeringeconomyoftenquotetheclassicquestionsthatGen.JohnJ.CarthappliedtoengineeringproposalswhenhewaschiefengineeroftheNewYorkTelephoneCompany,Thesequestionswerewhydoesthisatall?

Whydoitnow?

Whydoitthisway?

Thesemaybeviewedasdifferentaspectsofthegeneralquestion,willitpay?

Asthesequestionssuggest,mostengineeringproposalsinvolvemajorsetsofalternatives,withmanysubordinatesetsofalternativeinvolvedineachmajoralternative.Forexample,considerthequestionofwhethertousehydroorthermalpowertoaddneededcapacitytoanelectric-powersystem,forthehydroalternative,anumberofdifferentpossiblesitesmaybeavailable.Ataparticularsite,theremaybedifferentpossibledesignsforadiversiondam,differenttypeandsizesofconduittocarrywaterfromthepointofdiversiontothepowerplant,differentpossibilitiesfornumber,type,andsizeofturbinesatthepowerplant，andsoon.Eachsub-alternativeislikelytohaveitsownsub-alternatives.Ateverystageintheanalysis,itisnecessarytoconsiderrelativeeconomyinordertomakearationalchoiceamongthepossiblealternativesandthustoestablishthemostfavorableoverallplan.

Itishelpfultothinkofaneconomystudyasinvolvingthefollowingsteps:

（l）Eachalternativethatseemspromisingshouldbeidentifiedandclearlydefinedinphysicalterm.

（2）Insofaraspracticable,thephysicalestimatesforeachalternativeshouldbetranslatedintomoneyestimates.Generallyspeaking,moneyestimatesshouldbemadeofthosereceiptsanddisbursementswhichwillbeinfluencedbythechoiceamongthealternatives.Estimatesshouldbemadeofthedatesaswellasthemagnitudesofthereceiptsanddisbursements.Thisrequiresestimatesofthelivesandsalvagevalues,ifany,ofthestructuresandotherassetsrequiredforeachalternative.Italsocallsforadecisionregardingthelengthofthestudyperiod,theperiodoftimeforwhichtheeconomystudyistobemade.

（3）Usuallythemoneyestimatesneedtobeplacedonacomparablebasisbyappropriateinversionsthatmakeuseofthemathematicsofcompoundinterest.Thereconversionsshoulduseasaninterestratetheminimumattractiverateofreturnthatisappropriateintheparticularcircumstances.

（4）Achoice（orrecommendationforachoice）amongthealternativesmustbemade.Thisinfluencedbothbythecomparisonintermsofmoneyunitsandbyothermatterspracticabletoreducetomoneyterms.

Asimpleexampleofanannualcostcomparisonislistedbelow:

Twoalternativeplansareconsideredforasectionofanaqueduct.PlanAusesatunnel;planBusesasectionoflinedcanalandasectionofsteelflume.InplanA,theestimatedfirstcostofthetunnelis$450,000,itsestimatedannualmaintenancecostis$4,000,anditsestimatedlifeisl00yr.EstimatedfirstcostsandlivesfortheelementsofplanBarecanal（notincludinglining）,$120,000,00yr;canallining,$50,000,20yr;flume,$90,000,50yr.Theannualmaintenancecostis$10,500.Theinterest