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水利水电工程专业英语——灌溉与排水篇1.ConsumptiveUseofWater1.消耗性用水Consumptiveuseofwaterinvolvesproblemsofwatersupply,bothsurfaceandunderground,aswellasproblemsofmanagementandeconomicsofirrigationprojects.Consumptiveusehasbecomeahighlyimportantfactorinthearbitrationofcontroversiesovermajorstreamsystemswherethepublicwelfareofvalleys,states,andnationsisinvolved.Beforeavailablewaterresourcesofadrainagebasininaridandsemiaridregionscanbesatisfactorilyascertained,carefulconsiderationmustbegiventoconsumptiveuserequirementsforwaterinvarioussubbasins.消耗性用水涉及到地表和地下供水问题，也包括管理和灌溉工程的经济性问题。消耗性使用已经成为一个评判包含河谷、州和国家公共福利的主要河流系统争议的重要因素。在干旱和半干旱地区流域的可利用水资源被确定之前，必须仔细考虑各个子流域内对消耗性用水的需求。1.1DefinitionofConsumptiveUse1.1消耗性用水的定义Consumptiveuse,orevapotranspiration,isthesumoftwoterms:(1)transpiration,whichiswaterenteringplantrootsandusedtobuildplanttissueorbeingpassedthroughleavesofplantintotheatmosphere,(2)evaporation,whichiswaterevaporationfromadjacentsoil,watersurfaces,orfromthesurfacesofleavesoftheplant.Waterdepositedbydew,rainfall,orsprinklerirrigationandsubsequentlyevaporatingwithoutenteringtheplantsystemispartofconsumptiveuse.消耗性用水，或者说腾发量，是两项的总和：（1）蒸腾，即水分进入植物的根系用来构建植物体或者通过植物叶片被传输到大气中；（2）蒸发，即水分从邻近的土壤、水面或者从植物叶面蒸发的过程。通过露水、降雨或者喷灌储存，随后未经过植物体而蒸发也是消耗性用水的一部分。Consumptiveusecanapplytowaterrequirementsofacrop,afield,afarm,aproject,oravalley.Whentheconsumptiveuseofthecropisknown,thewateruseoflargerunitscanbecalculated.Hence,theterm“consumptiveuse”andthefollowingdiscussiongenerallyrefertothecrop.消耗性用水可以应用到一棵植物、一块土地、一片农场、一个项目或者一个河谷的用水需求中。当作物的消耗性用水为已知时，就可以计算更大单元的用水量。因此，术语“消耗性用水”和接下来的讨论主要是指作物。1.2ConditionsAffectingConsumptiveUseofWater1.2影响消费性用水的条件Evaportranspirationisinfluencedbytemperature,irrigationpractices,lengthofgrowingseason,precipitation,andotherfactors.Thevolumeofwatertranspiredbyplantsdependsinpartonthewaterattheirdisposal,andalsoontemperatureandhumidityoftheair,windmovement,intensityanddurationofsunlight,stageofdevelopmentoftheplant,typeoffoliage,andmatureoftheleaves.腾发量受到天气、灌溉方式、生长期长度、降水及其他因素影响。植物蒸腾的水量部分取决于其所处位置的水源，还有温度和空气的湿度、风运动、光照的强度和持续时间、植物生育阶段、叶片类型和叶片成熟度。Consumptiveusebynativevegetationofnoncroppedlandisfairlyconstantfromyeartoyearwherethewatersupplyisadequate,butsurfaceevaporationincreasesinwetyearsbecauseoftheexpansionofwatersurfaceandmoistsoilareas.Insomeirrigatedvalleysirrigationislavishwhenthewatersupplyisabundant,andincreasedwastewaterandreturnflowareconsequentlyavailablefornonproductiveconsumption.Also,evaporationisincreasedfromthecroppedlandsoils.Plantdiseasesandpestsreduceconsumptiveusebyinhibitingplantgrowth.Sizeofafarmmayaffectwaterusageappreciablysinceborders,sizeofstream,andcroprotationsmaybedifferent.原生植物的消耗性用水在水分供应充足地区每年是相当恒定的，但是在丰水年地表蒸发量却因为水面积和湿润土壤面积的扩大而增加。在一些灌溉河谷，当供水充足时灌溉是奢侈的，而且增加了废水量，因而回水可被用作非生产性耗水。并且，耕作区土壤的蒸发量也会增加。植物病虫害通过抑制植物的生长减少了消耗性用水。农场的大小可能会显著地影响水资源利用，因为边界、河流大小和植物轮作可能是不同的。1)Evapotraspirationfromsoils.Wherethewatertableisnearthegroundsurface,evaporationfromthesoilisalmostequaltoevaporationfromafreewatersurface;whereas,withwaterlevelsatgreaterdepthsbelowthesurface,evaporationfromsoildecreasesuntilitbecomesnegligiblewhenmoisturenolongerreachesthesurfacebycapillaryaction.1）土壤处的腾发。在地下水水位接近地表的地方，土壤蒸发量几乎与自由水面的蒸发量相同。而随着水位降低到距离地表更深处，土壤蒸发量就会随之减少，直到当水分不再能通过毛细作用到达地表时它便可以忽略不计。Whereirrigationwaterisappliedbyfloodingmethods,largeamountsofwaterarelostbydirectevaporationfromsoilsurfaceswithouthavingpassedthroughtheroots,stems,andleavesofplants.Afterlightshowersduringthegrowingseason,considerablerainfall,ifnotall,isretainedontheleaveswhereitsubsequentlyevaporateswithoutenteringtherootsoftheplants.Showersoflessthan5millimetersseldomenterthesoiltoasufficientdepthtobeusedbytheplants.Therefore,waterreceivedfromlightrainshowersorfromlightsprinklerirrigationmaynotbeusedbytheplantsinthetranspirationprocess.Subsequentdiscussionbasedupontheenergyavailableforevaporationshows,however,thatundernormalconditions,waterthatevaporatesdirectlyfromthesoilorleavesisbeneficiallyused,reducingbyalikeamountwaterthatwouldotherwisehavebeentranspiredbytheplants.Thisistrueprovidedanormalmaturecropexistsoverthesoilsurface.Earlyorlateinthegrowingperiod,whenthecropisnottranspiringmuchwater,evaporationfromawetsoilsurfacemayexceednormalconsumptiveuse.当灌溉水是通过漫灌的方式引入的时候，大量的水就会直接从土壤表面蒸发，而没有经过植物的根、茎和叶。在生长季节的小阵雨过后，至少相当部分的降雨被截留在叶面上并且随后从那里蒸发，并未经过植物的根系。小于5mm的降雨几乎不能进入到足够的深度而被植物利用。因此，从小阵雨或从轻微的喷灌中获得的水分可能不会被植物用到蒸腾过程中。基于蒸发使用能量的角度考虑的论述表明，尽管在正常情况下，直接从土壤和叶面蒸发的水分得到了充分的利用，这些水若不被蒸发则会被植物用作蒸腾。这真正地在土壤表面养活了一颗正常成熟的作物。在生长周期的早期或晚期，当作物蒸腾量不大时，从湿润土壤表面的蒸发可能会超过正常的消耗性用水。Therearestilldecideddifferencesinopinionontheeffectofcultivationondirectevaporationofwaterfromsoils.Recentstudiesseemtothrowconsiderabledoubtonadvantagesofsoilmulchesforconservingwaterthroughreductionofevaporationlossesfromsoilsthatarenotexcessivelywetorincontrastwithawatertableatashallowdepth.Therefore,broadgeneralconclusionsconcerninginfluenceofcultivationondirectevaporationlossesfromsoilsmaybemisleading.Thelargenumberofvariablefactorsinvolved-notablythedifferencesindistancestofree-watersources,inoriginalmoisturecontentofunsaturatedsoils,