TPO-12 Reading 3 阅读译文

Water in the Desert沙漠中的水源Rainfall isnot completelyabsent indesert areas,but itis highlyvariable.An annualrainfallof fourinches isoften usedto definethe limitsof adesert.The impactof rainfalluponthe surfacewater andgroundwater resourcesof thedesert isgreatly influencedbylandforms.Flats anddepressions wherewater cancollect arecommon features,but theymakeup only a smallpart of the landscape.沙漠中并不是完全没有降雨，只不过是变数很大通常一年以内降雨次数少于次4是定义沙漠的限定条件降水对沙漠地表和地底的水资源的影响很大程度上取决于地貌平原和洼地是水源聚集的共同地貌特征，不过他们只占地表的很小一部分Arid lands,surprisingly,contain someof the worlds largestriver systems,such astheMurray-Darling inAustralia,the RioGrande inNorth America,the Indusin Asia,and theNilein Africa.These rivers and riversystems are known asexogenous becausetheirsources lieoutside thearid zone.They arevital forsustaining lifein someof thedriestparts oftheworld.For centuries,the annualfloods ofthe Nile.Tigris,and Euphrates,forexample,has broughtfertile siltsand waterto theinhabitants oftheir lowervalleys.Today,river dischargesare increasinglycontrolled byhuman intervention,creating aneed forinternationalriver-basin agreements.The fillingoftheAtaturk andother damsin Turkeyhasprastically reducedflows inthe Euphrates,with potentiallyserious consequencesforSyria andIraq.令人惊奇的是，干旱地区往往都存在着世界上最大的河流流域，例如澳大利亚的墨累-达令河，北美洲的格兰德河，亚洲的印度河，以及非洲的尼罗河这些河流被称作和所在的流域因为河的源头在干旱地区以外而被称为“外流河二他们对于全世界沙漠地区的生命的存活至关重要几个世纪以来，尼罗河每年都会定期泛滥举个例子，幼发拉底河和底格里斯河都会把大量的肥沃的泥沙和水源带给下游低洼地带的居民现在，河水的流量越来越多的受到人类的干涉，产生了国际性的河流流域的协议阿卡杜克水坝以及其他一些建在土耳其境内的大坝就极大的减少了幼发拉底河的径流量，潜移默化的给叙利亚河和伊拉克造成了严重的后果The flowof exogenousrivers varieswith theseason.The desertsections oflong riversrespondseveral monthsafter rainhas fallenoutside thedesert,so thatpeak flowsmay beinthe dryseason.This isuseful forirrigation,but thehigh temperatures,low humidity,anddifferent daylengths ofthe dryseason,compared to the normalgrowing season,canpresent difficultieswith somecrops.外流河的径流量通常受季节影响雨季过后，从外部流入沙漠区域的长河可以持续好几个月，以便保持干旱时节的相对较少的径流量这虽然有助于灌溉，但是高温，低湿，以及干旱时节与众不同的日照时长，相比正常的生长季节也很难栽种一些作物Regularly flowingriversandstreams thatoriginate withinarid landsareknown asendogenous.These aregenerally fedby groundwatersprings,and manyissue fromlimestonemassifs,such asthe AtlasMountains inMorocco.Basaltic rocksalso supportsprings,notably atthe JabalAl-Arab onthe Jordan-Syria border.■Endogenous Riversoftendo notreach thesea butdrain intoinland basins,where thewater evaporatesor islostin theground.-Most desertstreambeds arenormally dry,but theyoccasionally receivelargeflows of water andsediment.■通常发源地在干旱地区的河流和溪水被称为“内流河”它们通常是又地下水的泉眼供给，也一些石灰岩断层中流出的水源供给，例如摩洛哥的阿特拉斯山岩石也提供源头水，比较著名的就是约旦和叙利亚交接的内Basaltic JabalAl-Arab.流河通常都不会到达大海而是注入内陆的低地的同时蒸发或者消失在地表大多数沙漠的河床通常都是干枯的，偶有比较大的径流和沉积物Deserts containlarge amountsof groundwaterwhen comparedtotheamounts theyhold insurfacestores such as lakesand rivers.-But onlya smallfraction of groundwater entersthehydrological cycle-feeding theflows ofstreams,maintaining lakelevels,and beingrechargedor refilledthrough surfaceflows andrainwater.In recentyears,groundwaterhas becomean increasinglyimportant sourceof freshwaterfor desertdwellers.The UnitedNationsEnvironment Programme andthe WorldBank havefunded attemptsto surveythegroundwater resourcesof arid lands andto developappropriate extractiontechniques.Such programsare muchneeded becausein manyaridlandsthere isonlyavague ideaofthe extentofgroundwaterresources.It is known,however,that thedistribution ofgroundwateris uneven,andthat muchof itlies atgreat depths.相比于地表所的湖泊和河流含有的水量，沙漠中地下水的贮藏量要大得多不过只有一小部分地下水参与了河流的水循环，保持湖泊的水位，并通过地表径流和降雨进行再造再注入近些年来，地下水作为沙漠住民的活水来源的重要性日益加重美国国家环境总署和世界银行开始拨款尝试调查统计干旱地区的地下水资源并发展合适的开采技术像这样的工程非常必要因为在干旱地区对于地下水资源的保有量的概念非常模糊然而可以确定的是，地下水资源的分布非常不均匀，且大多埋藏在很深的地底Groundwater isstored inthe porespaces andjoints ofrocks andunconsolidatedunsolidified sedimentsor inthe openingswidened throughfractures andweathering.Thewater-saturated rockor sedimentisknownas an aquifer”.Because theyare porous,sedimentary rocks,suchassandstones andconglomerates,are importantpotential sourcesofgroundwater.Large quantitiesofwatermay alsobe storedin limestones whenjointsand crackshave beenenlarged toform cavities.Most limestoneand sandstoneaquifers aredeepand extensivebut maycontain ground waters thatare notbeing recharged.Mostshallow aquifersin sandand graveldeposits producelower yields,but theycan berapidlyrecharged.Some deepaquifers areknownasfossil waters.The termfossil describeswaterthat hasbeen presentfor severalthousand years.These aquifersbecame saturatedmorethan10,000years agoand areno longerbeing recharged.地下水一般储存在多孔道的地区和连接岩层的未凝固沉积层或者是通过风华和断裂形成的宽阔的孔洞饱含水的岩石或沉积物被称为“蓄水层”因为沉积岩的多孔性，比如砂岩和砾岩，都是地下水的重要潜在源头大量的水资源也可能储存在石灰岩中，只要联结和裂口足够大到形成容器大多数石灰岩和砂岩蓄水层很深且广大，但是保有的水资源是不能再生的大多数沙石中的较浅的蓄水层只有较小的保有量，但是他们可以迅速的再生一些深层的蓄水曾被称为“化石水”“化石”的意思是说这里的水已经被保存了几千年之久这些蓄水层充满水起码已经万年以上了，而其他们在短期之内是无法再生的1Water doesnot remainimmobile inanaquiferbut canseep outat springsor leakinto otheraquifers.The rateof movementmay bevery slow:intheIndus plain,the movementofsaline saltygroundwatershas stillnot reachedequilibrium after70years ofbeing tapped.The mineralcontent ofgroundwater normallyincreases withthe depth,but evenquiteshallow aquiferscan behighly saline.水在贮存在蓄水层中不是保持不流动的，而是通过泉眼或是渗漏进入其他的蓄水层，可以流动的比例可能很低；在印度平原，流动的含盐地下水在开发了年以70后依旧不能达到平静矿石中保有的地下水通常会增加蓄水层的深度，但是较浅的安静蓄水层会饱含盐分。