现代大学英语精读4第二版Unit 5A For Want of a Drink 课文原文

ForWantofaDrink

Whenthewordwaterappearsinprintnowadays,crisisisrarely

farbehind.Water,itissaid,isthenewoil:aresourcelong

squandered,nowgrowingexpensiveandsoontobe

overwhelmedbyinsatiabledemand.Aquifersarefalling,

glaciersvanishing,reservoirsdryingupandriversnolonger

flowingtothesea.Climatechangethreatenstomakethe

problemworse.Everyonemustuselesswateriffamine,

pestilenceandmassmigrationarenottosweeptheglobe.

2.Thelanguageisoftenoverblown,andtheremedies

sometimesill-conceived,butthebasicmessageisnotwrong.

Waterisindeedscarceinmanyplaces,andwillgrowscarcer.

Bringingsupplyanddemandintoequilibriumwillbepainful,

andpoliticaldisputesmayincreaseinnumberandintensifyin

theircapacitytocausetrouble.Tocarryonwithpresent

practicewouldindeedbetoinvitedisaster.

3.Why?Thedifficultiesstartwiththesheernumberofpeople

usingthestuff.When,60yearsago,theworld'spopulationwas

about2.5billion,worriesaboutwatersupplyaffectedrelatively

fewpeople.Bothdroughtandhungerexisted,astheyhave

throughouthistory,butmostpeoplecouldbefedwithout

irrigatedfarming.Thenthegreenrevolution,inaninspired

combinationofnewcropbreeds,fertilizersandwater,made

possibleahugeriseinthepopulation.Thenumberofpeople

onEarthroseto6billionin2000,nearly7billiontoday,andis

headingfor9billionin2050.Theareaunderirrigationhas

doubledandtheamountofwaterdrawnforfarminghastripled.

Theproportionofpeoplelivingincountrieschronicallyshortof

waterissettorisefrom8%attheturnofthe21stcenturyto

45%by2050.

4.Farmers'increasingdemandforwateriscausednotonlyby

thegrowingnumberofmouthstobefedbutalsobypeople's

desireforbetter-tasting,moreinterestingfood.Unfortunately,

ittakesnearlytwiceasmuchwatertogrowakiloofpeanutsas

akiloofsoybeans,nearlyfourtimesasmuchwatertoproduce

akiloofbeefasakiloofchicken.With2billionpeoplearound

theworldabouttoenterthemiddleclass,theagricultural

demandsonwaterwouldincreaseevenifthepopulationstood

still.

5.Industry,too,needswater.Ittakesabout22%oftheworld's

withdrawals.Domesticactivitiestaketheother8%.Together,

thedemandsofthesetwocategoriesquadrupledinthesecond

halfofthe20thcentury,growingtwiceasfastasthoseof

farming.

6.Meetingthatdemandisadifficulttask.Onereasonisthatthe

supplyofwaterisfinite.Theworldwillhavenomoreofitin

2025or2050thanithastoday,orwhenitlappedatthesidesof

Noah'sArk.Thisisbecausethelawofconservationofmasssays,

broadly,thathoweveryouuseit,youcannotdestroythestuff.

Neithercanyoureadilymakeit.Ifsomeofitseemstocome

fromtheskies,thatisbecauseithasevaporatedfromthe

Earth'ssurface,condensedandreturned.

7.Mostofthissurfaceissea,andthewaterbelowit—over97%

ofthetotalonEarth—issalty.Inprinciple,thesaltcanbe

removedtoincreasethesupplyoffreshwater,butatpresent

desalinationisexpensiveanduseslotsofenergy.

8.Ofthe2.5%ofwaterthatisnotsalty,about70%isfrozen,

eitheratthepoles,inglaciersorinpermafrost.Soallliving

things,exceptthoseinthesea,haveabout0.75%ofthetotalto

surviveon.Mostofthisavailablewaterisunderground,in

aquifersorsimilarformations.Therestisfallingasrain,sitting

inlakesandreservoirsorflowinginriverswhereitis,withluck,

replacedbyrainfallandmeltingsnowandice.Thereisalso,

takenote,watervaporintheatmosphere.

9.Thevalueofwaterasacommodityofcoursevariesaccording

tolocality,purposeandcircumstance.Takelocalityfirst.Water

isnotevenlydistributed—justninecountriesaccountfor60%

ofallavailablefreshsupplies—andamongthemonlyBrazil,

Canada,Colombia,Congo,IndonesiaandRussiahavean

abundance.Americaisrelativelywelloff,butChinaandIndia,

withoverathirdoftheworld'spopulationbetweenthem,have

lessthan10%ofitswater.

10.Evenwithincountriesthevariationsmaybehuge.The

averageannualrainfallinIndia'snortheastis110timesthatin

itswesterndesert.Andmanyplaceshaveplentyofwater;or

evenfartoomuch.Floodingisroutine,andmaybecomemore

frequentanddamagingwithclimatechange.

ll.Scarceorplentiful,waterisabovealllocal.Itisheavy—one

cubicwaterweighsatonne—,soexpensivetomove.Surface

water—mostlyrivers,lakesandreservoirs—willnotflowfrom

onebasinintoanotherwithoutartificialdiversion,andusually

onlywithpumping.Withinabasin,thewaterupstreammaybe

usefulforirrigation,industrialordomesticuse.Asitnearsthe

sea,though,theopportunitiesdiminishtothepointwhereit

hasnousesexcepttosustaindeltas,wetlandsandtocarrysilt

outtosea.

12.Theseshouldnotbeoverlooked.Ifriversdonotflow,

nothingcanliveinthem.Overafifthoftheworld'sfreshwater

fishspeciesofacenturyagoarenowendangeredorextinct.

Halftheworld'swetlandshavealsodisappearedoverthepast

200years.Thepointis,though,thatevenwithinabasinwater

ismorevaluableinsomeplacesthaninothers.

13.Almostanywherearid,thewaterunderground,oncelargely

ignored,hascometobeseenasespeciallyvaluableasthe

demandsoffarmershaveoutgrowntheirsuppliesofrainand

surfacewater.Groundwaterhascometotherescue,andfora

whileitseemedamiraculoussolution:drillaborehole,pump

thestuffupfrombelowandinduecourseitwillbereplaced.In

manyplaces,however,fromtheUnitedStatestoIndiaand

China,thequantitiesbeingwithdrawnexceedtheannual

recharge.Thisisseriousformillionsofpeoplenotjustinthe

countrybutalsoinmanyoftheworld'sbiggestcities,which

oftendependonaquifersfortheirdrinkingwater.

14.The20millioninhabitantsofMexicoCityanditssurrounding

area,forexample,drawover70%oftheirwaterfromanaquifer

thatwillrundrywithin200years,maybesooner.Alreadythe

cityissinkingasaresult.IntheHairiverbasininChina,

deep-groundwatertableshavedroppedbyupto90meters.

15.Partofthebeautyoftheboreholeisthatitrequiresno

elaborateapparatus.Asinglefarmermaybeabletosinkhis

owntubewellandstartpumping.ThatiswhyIndiaandChina

arenowperforatedwithmillionsofirrigationwells,each

drawingonthecommonresource.Sometimesthisresource

maybehuge.Butevenbigaquifersarenotimmunetothelaws

ofphysics.Manyplacesareseriouslyoverdrawn.Inthoseplaces,

farmersprobablyhavetopaysomethingfortherighttodraw

groundwater.Butalmostnowherewillthepricereflectscarcity,

andoftenthereisnochargeatallandnoonemeasureshow

muchwaterisbeingtaken.

16.Pricedornot,wateriscertainlyvalued,andthatvalue

dependsontheusetowhichitisharnessed.Waterisusednot

justtogrowfoodbuttomakeeverykindofproduct,from

microchipstosteelgirders.Thelargestindustrialpurposeto

whichitisputiscoolinginthermalpowergeneration,butitis

alsousedindrillingforandextractingoil,themakingof

petroleumproductsandethanol,andtheproductionof

hydroelectricity.Someoftheprocessesinvolved,suchashydro

powergeneration,consumelittlewater(afterdrivingthe

turbines,mostisreturnedtotheriver),butsome,suchasthe

techniquesusedtoextractoilfromsands,arebigconsumers.

17.Industrialusetakesabout60%ofwaterinrichcountriesand

10%intherest.Thedifferenceindomesticuseismuchsmaller,

11%and8%respectively.Someofthevariationisexplainedby

capaciousbaths,powershowersandflushlavatoriesintherich

world.Allhumans,however;needabasicminimumoftwolitres

ofwaterinfoodordrinkeachday,andforthisthereisno

substitute.NoonesurvivedintheruinsofPort-au-Princefor

morethanafewdaysafterJanuary'searthquakeunlessthey

hadaccesstosomewater-basedfoodordrink.Thatiswhy

manypeopleinpoorandaridcountries—usuallywomenor

children—setoffearlyeachmorningtotrudgetothenearest

wellandreturnfiveorsixhourslaterburdenedwithprecious

supplies.Thatiswhymanypeoplebelievewatertobeahuman

right,anecessitymorebasicthanbreadoraroofoverthehead.

18.Fromthismuchfollows.Oneconsequenceisawidespread

beliefthatnooneshouldhavetopayforwater.TheByzantine