現(xiàn)代大學英語精讀4第二版Unit 5A For Want of a Drink課文原文

現(xiàn)代大學英語精讀4第二版Unit5AForWantofaDrink課文原文現(xiàn)代大學英語精讀4第二版Unit5AForWantofaDrink課文原文現(xiàn)代大學英語精讀4第二版Unit5AForWantofaDrink課文原文資料僅供參考文件編號：2022年4月現(xiàn)代大學英語精讀4第二版Unit5AForWantofaDrink課文原文版本號：A修改號：1頁次：1.0審核：批準:發(fā)布日期：ForWantofaDrinkWhenthewordwaterappearsinprintnowadays,crisisisrarelyfarbehind.Water,itissaid,isthenewoil:aresourcelongsquandered,nowgrowingexpensiveandsoontobeoverwhelmedbyinsatiabledemand.Aquifersarefalling,glaciersvanishing,reservoirsdryingupandriversnolongerflowingtothesea.Climatechangethreatenstomaketheproblemworse.Everyonemustuselesswateriffamine,pestilenceandmassmigrationarenottosweeptheglobe.2.Thelanguageisoftenoverblown,andtheremediessometimesill-conceived,butthebasicmessageisnotwrong.Waterisindeedscarceinmanyplaces,andwillgrowscarcer.Bringingsupplyanddemandintoequilibriumwillbepainful,andpoliticaldisputesmayincreaseinnumberandintensifyintheircapacitytocausetrouble.Tocarryonwithpresentpracticewouldindeedbetoinvitedisaster.3.Why

Thedifficultiesstartwiththesheernumberofpeopleusingthestuff.When,60yearsago,theworld'spopulationwasabout2.5billion,worriesaboutwatersupplyaffectedrelativelyfewpeople.Bothdroughtandhungerexisted,astheyhavethroughouthistory,butmostpeoplecouldbefedwithoutirrigatedfarming.Thenthegreenrevolution,inaninspiredcombinationofnewcropbreeds,fertilizersandwater,madepossibleahugeriseinthepopulation.ThenumberofpeopleonEarthroseto6billionin2000,nearly7billiontoday,andisheadingfor9billionin2050.Theareaunderirrigationhasdoubledandtheamountofwaterdrawnforfarminghastripled.Theproportionofpeoplelivingincountrieschronicallyshortofwaterissettorisefrom8%attheturnofthe21stcenturyto45%by2050.4.Farmers'increasingdemandforwateriscausednotonlybythegrowingnumberofmouthstobefedbutalsobypeople'sdesireforbetter-tasting,moreinterestingfood.Unfortunately,ittakesnearlytwiceasmuchwatertogrowakiloofpeanutsasakiloofsoybeans,nearlyfourtimesasmuchwatertoproduceakiloofbeefasakiloofchicken.With2billionpeoplearoundtheworldabouttoenterthemiddleclass,theagriculturaldemandsonwaterwouldincreaseevenifthepopulationstoodstill.5.Industry,too,needswater.Ittakesabout22%oftheworld'swithdrawals.Domesticactivitiestaketheother8%.Together,thedemandsofthesetwocategoriesquadrupledinthesecondhalfofthe20thcentury,growingtwiceasfastasthoseoffarming.6.Meetingthatdemandisadifficulttask.Onereasonisthatthesupplyofwaterisfinite.Theworldwillhavenomoreofitin2025or2050thanithastoday,orwhenitlappedatthesidesofNoah'sArk.Thisisbecausethelawofconservationofmasssays,broadly,thathoweveryouuseit,youcannotdestroythestuff.Neithercanyoureadilymakeit.Ifsomeofitseemstocomefromtheskies,thatisbecauseithasevaporatedfromtheEarth'ssurface,condensedandreturned.7.Mostofthissurfaceissea,andthewaterbelowit—over97%ofthetotalonEarth—issalty.Inprinciple,thesaltcanberemovedtoincreasethesupplyoffreshwater,butatpresentdesalinationisexpensiveanduseslotsofenergy.8.Ofthe2.5%ofwaterthatisnotsalty,about70%isfrozen,eitheratthepoles,inglaciersorinpermafrost.Soalllivingthings,exceptthoseinthesea,haveabout0.75%ofthetotaltosurviveon.Mostofthisavailablewaterisunderground,inaquifersorsimilarformations.Therestisfallingasrain,sittinginlakesandreservoirsorflowinginriverswhereitis,withluck,replacedbyrainfallandmeltingsnowandice.Thereisalso,takenote,watervaporintheatmosphere.9.Thevalueofwaterasacommodityofcoursevariesaccordingtolocality,purposeandcircumstance.Takelocalityfirst.Waterisnotevenlydistributed—justninecountriesaccountfor60%ofallavailablefreshsupplies—andamongthemonlyBrazil,Canada,Colombia,Congo,IndonesiaandRussiahaveanabundance.Americaisrelativelywelloff,butChinaandIndia,withoverathirdoftheworld'spopulationbetweenthem,havelessthan10%ofitswater.10.Evenwithincountriesthevariationsmaybehuge.TheaverageannualrainfallinIndia'snortheastis110timesthatinitswesterndesert.Andmanyplaceshaveplentyofwater,orevenfartoomuch.Floodingisroutine,andmaybecomemorefrequentanddamagingwithclimatechange.11.Scarceorplentiful,waterisabovealllocal.Itisheavy—onecubicwaterweighsatonne—,soexpensivetomove.Surfacewater—mostlyrivers,lakesandreservoirs—willnotflowfromonebasinintoanotherwithoutartificialdiversion,andusuallyonlywithpumping.Withinabasin,thewaterupstreammaybeusefulforirrigation,industrialordomesticuse.Asitnearsthesea,though,theopportunitiesdiminishtothepointwhereithasnousesexcepttosustaindeltas,wetlandsandtocarrysiltouttosea.12.Theseshouldnotbeoverlooked.Ifriversdonotflow,nothingcanliveinthem.Overafifthoftheworld'sfreshwaterfishspeciesofacenturyagoarenowendangeredorextinct.Halftheworld'swetlandshavealsodisappearedoverthepast200years.Thepointis,though,thatevenwithinabasinwaterismorevaluableinsomeplacesthaninothers.13.Almostanywherearid,thewaterunderground,oncelargelyignored,hascometobeseenasespeciallyvaluableasthedemandsoffarmershaveoutgrowntheirsuppliesofrainandsurfacewater.Groundwaterhascometotherescue,andforawhileitseemedamiraculoussolution:drillaborehole,pumpthestuffupfrombelowandinduecourseitwillbereplaced.Inmanyplaces,however,fromtheUnitedStatestoIndiaandChina,thequantitiesbeingwithdrawnexceedtheannualrecharge.Thisisseriousformillionsofpeoplenotjustinthecountrybutalsoinmanyoftheworld'sbiggestcities,whichoftendependonaquifersfortheirdrinkingwater.14.The20millioninhabitantsofMexicoCityanditssurroundingarea,forexample,drawover70%oftheirwaterfromanaquiferthatwillrundrywithin200years,maybesooner.Alreadythecityissinkingasaresult.IntheHairiverbasininChina,deep-groundwatertableshavedroppedbyupto90meters.15.Partofthebeautyoftheboreholeisthatitrequiresnoelaborateapparatus.Asinglefarmermaybeabletosinkhisowntubewellandstartpumping.ThatiswhyIndiaandChinaarenowperforatedwithmillionsofirrigationwells,eachdrawingonthecommonresource.Sometimesthisresourcemaybehuge.Butevenbigaquifersarenotimmunetothelawsofphysics.Manyplacesareseriouslyoverdrawn.Inthoseplaces,farmersprobablyhavetopaysomethingfortherighttodrawgroundwater.Butalmostnowherewillthepricereflectscarcity,andoftenthereisnochargeatallandnoonemeasureshowmuchwaterisbeingtaken.16.Pricedornot,wateriscertainlyvalued,andthatvaluedependsontheusetowhichitisharnessed.Waterisusednotjusttogrowfoodbuttomakeeverykindofproduct,frommicrochipstosteelgirders.Thelargestindustrialpurposetowhichitisputiscoolinginthermalpowergeneration,butitisalsousedindrillingforandextractingoil,themakingofpetroleumproductsandethanol,andtheproductionofhydroelectricity.Someoftheprocessesinvolved,suchashydropowergeneration,consumelittlewater(afterdrivingtheturbines,mostisreturnedtotheriver),butsome,suchasthetechniquesusedtoextractoilfromsands,arebigconsumers.17.Industrialusetakesabout60%ofwaterinrichcountriesand10%intherest.Thedifferenceindomesticuseismuchsmaller,11%and8%respectively.Someofthevariationisexplainedbycapaciousbaths,powershowersandflushlavatoriesintherichworld.Allhumans,however,needabasicminimumoftwolitresofwaterinfoodordrinkeachday,andforthisthereisnosubstitute.NoonesurvivedintheruinsofPort-au-PrinceformorethanafewdaysafterJanuary'searthquakeunlesstheyhadaccesstosomewater-basedfoodordrink.Thatiswhymanypeopleinpoorandaridcountries—usuallywomenorchildren—setoffearlyeachmorningtotrudgetothenearestwellandreturnfiveorsixhourslaterburdenedwithprecioussupplies.Thatiswhymanypeoplebelievewatertobeahumanright,anecessitymorebasicthanbreadoraroofoverthehead.18.Fromthismuchfollows.Oneconsequenceisawidespreadbeliefthatnooneshouldhave