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1、托托网托福模拟考试软件2.0配套资料托福TPO24真题全阅读文本附答案译文下载地址http://www.tuotuowang.comLakeWaterWheredoesthewaterinalakecomefrom,andhowdoeswaterleaveit?Waterentersalakefrominflowingrivers,fromunderwaterseepsandsprings,fromoverlandflowoffthesurroundingland,andfromrainfallingdirectlyonthelakesurface.Waterleavesalakevi
2、aoutflowingrivers,bysoakingintothebedofthelake,andbyevaporation.Somuchisobvious.Thequestionsbecomemorecomplicatedwhenactualvolumesofwaterareconsidered:howmuchwaterentersandleavesbyeachroute?Discoveringtheinputsandoutputsofriversisamatterofmeasuringthedischargesofeveryinflowingandoutflowingstream
3、andriver.Thenexchangeswiththeatmospherearecalculatedbyfindingthedifferencebetweenthegainsfromrain,asmeasured(ratherroughly)byramgauges,andthelossesbyevaporation,measuredwithmodelsthatcorrectfortheothersourcesofwaterloss.Forthemajorityoflakes,certainlythosesurroundedbyforests,inputfromoverlandflo
4、wistoosmalltohaveanoticeableeffect.Changesinlakelevelnotexplainedbyriverflowsplusexchangeswiththeatmospheremustbeduetothenetdifferencebetweenwhatseepsintothelakefromthegroundwaterandwhatleaksintothegroundwater.Notetheword“net”:measuringtheactualamountsofgroundwaterseepageintothelakeandoutofthela
5、keisamuchmorecomplicatedmatterthanmerelyinferringtheirdifference.Onceallthisinformationhasbeengathered,itbecomespossibletojudgewhetheralake'sflowismainlyduetoitssurfaceinputsandoutputsortoitsundergroundinputsandoutputs.■Iftheformeraregreater,thelakeisasurface-water-dominatedlake;ifthelatter,itis
6、aseepage-dominatedlake.■Occasionally,commonsensetellsyouwhichofthesetwopossibilitiesapplies.■Forexample,apondinhillycountrythatmaintainsasteadywaterlevel1托托网（www.tuotuowang.com）模考软件真实iBT机考界面托福考试复习模拟的好帮手高分利器托托网托福模拟考试软件2.0配套资料托福TPO24真题全阅读文本附答案译文下载地址http://www.tuotuowang.comallthroughadrysummerinsp
7、iteofhavingnostreamsflowingintoitmustobviouslybeseepagedominated.Conversely,apondwithastreamflowinginoneendandouttheother,whichdriesupwhenthestreamdriesup,isclearlysurfacewaterdominated.■Bywhatevermeans,alakeisconstantlygain
