给排水专业英语-Unit-1ppt课件.ppt

1 市政工程给排水科学与工程专业英语 2 Unit1HydrologicCycle ImportantWordsandExpressionshydrologyn 水文学 水文地理学reservoirn 蓄水池 贮液器 储藏 蓄积evaporationn 蒸发 发散 消失condensationn 冷凝 冷凝液 凝结的水珠 节略precipitationn 匆促 沉淀 雨等 降落 某地区降雨等的量figuren 数字 算术 图解 轮廓vt 估计 推测 认为 3 replenishvt 补充 重新装满 把 装满sedimentationn 沉淀 沉降evaportranspirationn 作物腾发量sublimaten 升华物vt 使某物质 升华 使净化 纯化infiltrationn 渗透residencetime停留时间deforestationn 采伐森林 森林开伐afforestationn 造林 造林地区aquifern 地下蓄水层 砂石含水层 4 Thehydrologiccycle alsoknownasthewatercycleorH2Ocycle describesthecontinuousmovementofwateron aboveandbelowthesurfaceoftheearth Watercanchangestatesamongliquid vapour andsolidatvariousplacesinthewatercycle AlthoughthebalanceofwateronEarthremainsfairlyconstantovertime individualwatermoleculescancomeandgo inandoutoftheatmosphere Thewatermovesfromonereservoirtoanother suchasfromrivertoocean orfromtheoceantotheatmosphere bythephysicalprocessesofevaporation condensation precipitation infiltration runoff andsubsurfaceflow 1 Insodoing thewatergoesthroughdifferentphases liquid solid andgas 5 Thewatercycleinvolvestheexchangeofheatenergy whichleadstotemperaturechanges Forinstance intheprocessofevaporation watertakesupenergyfromthesurroundingsandcoolstheenvironment Conversely intheprocessofcondensation waterreleasesenergytoitssurroundings warmingtheenvironment ThewatercyclefiguressignificantlyinthemaintenanceoflifeandecosystemsonEarth Evenaswaterineachreservoirplaysanimportantrole thewatercyclebringsaddedsignificancetothepresenceofwateronourplanet 6 Bytransferringwaterfromonereservoirtoanother thewatercyclepurifieswater replenishesthelandwithfreshwater andtransportsmineralstodifferentpartsoftheglobe 2 ItisalsoinvolvedinreshapingthegeologicalfeaturesoftheEarth throughsuchprocessesaserosionandsedimentation Inaddition asthewatercyclealsoinvolvesheatexchange itexertsaninfluenceonclimateaswell 7 Thesun whichdrivesthewatercycle heatswaterinoceansandseas Waterevaporatesaswatervaporintotheair Iceandsnowcansublimatedirectlyintowatervapor Evapotranspirationiswatertranspiredfromplantsandevaporatedfromthesoil Risingaircurrentstakethevaporupintotheatmospherewherecoolertemperaturescauseittocondenseintoclouds Aircurrentsmovewatervaporaroundtheglobe cloudparticlescollide grow andfalloutoftheskyasprecipitation 8 Someprecipitationfallsassnoworhail sleet andcanaccumulateasicecapsandglaciers whichcanstorefrozenwaterforthousandsofyears Mostwaterfallsbackintotheoceansorontolandasrain wherethewaterflowsoverthegroundassurfacerunoff Aportionofrunoffentersriversinvalleysinthelandscape withstreamflowmovingwatertowardstheoceans Runoffandgroundwaterarestoredasfreshwaterinlakes 9 Notallrunoffflowsintorivers muchofitsoaksintothegroundasinfiltration Somewaterinfiltratesdeepintothegroundandreplenishesaquifers whichstorefreshwaterforlongperiodsoftime Someinfiltrationstaysclosetothelandsurfaceandcanseepbackintosurface waterbodies andtheocean asgroundwaterdischarge Somegroundwaterfindsopeningsinthelandsurfaceandcomesoutasfreshwatersprings Overtime thewaterreturnstotheocean whereourwatercyclestarted 10 Theresidencetimeofareservoirwithinthehydrologiccycleistheaveragetimeawatermoleculewillspendinthatreseroir Itisameasureoftheaverageageofthewaterinthatreservoir Groundwatercanspendover10 000yearsbeneathEarth ssurfacebeforeleaving Particularlyoldgroundwateriscalledfossilwater Waterstoredinthesoilremainsthereverybriefly becauseitisspreadthinlyacrosstheEarth andisreadilylostbyevaporation transpiration streamflow orgroundwaterrecharge 3 11 Afterevaporating theresidencetimeintheatmosphereisabout9daysbeforecondensingandfallingtotheEarthasprecipitation Themajoricesheet AntarcticaandGreenland storeiceareforverylongperiods IcefromAntarcticahasbeenreliablydatedto800 000yearsbeforepresent thoughtheaverageresidencetimeisshorter 12 Inhydrology residencetimescanbeestimatedintwoways Themorecommonmethodreliesontheprincipleofconservationofmassandassumestheamountofwaterinagivenreservoirisroughlyconstant Withthismethod residencetimesareestimatedbydividingthevolumeofthereservoirbytheratebywhichwatereitherentersorexitsthereservoir 13 Conceptually thisisequivalenttotiminghowlongitwouldtakethereservoirtobecomefilledfromemptyifnowaterweretoleave orhowlongitwouldtakethereservoirtoemptyfromfullifnowaterweretoenter Analternativemethodtoestimateresidencetimes whichisgaininginpopularityfordatinggroundwater istheuseofisotopictechniques Thisisdoneinthesubfieldofisotopehydrology 14 Humanactivitiesthatalterthewatercycleinclude AgricultureIndustryAlterationofthechemicalcompositionoftheatmosphereConstructionofdamsDeforestationandafforestationRemovalofgroundwaterfromwellsWaterabstractionfromriversUrbanization 15 Effectsonclimate Thewatercycleispoweredfromsolarenergy 86 oftheglobalevaporationoccursfromtheoceans reducingtheirtemperaturebyevaporativecooling Withoutthecooling theeffectofevaporationonthegreenhouseeffectwouldleadtoamuchhighersurfacetemperatureof67 153 andawarmerplanet 16 AquiferdrawdownoroverdraftingandthepumpingoffossilwaterincreasesthetotalamountofwaterinthehydrospherethatissubjecttotranspirationandevaporationtherebycausingaccretioninwatervapourandcloudcoverwhicharetheprimaryabsorbersofinfraredradiationintheEarth satmosphere 4 Addingwatertothesystemhasaforcingeffectonthewholeearthsystem anaccurateestimate