地下水水文学(麻省理工讲义)

1.72,GroundwaterHydrologyProf.CharlesHarvey1.72,GroundwaterHydrologyProf.CharlesHarveyLecturePacket1Pageof15Polarfront/subarcticlowSpatialdistributionofenergyandtemperaturedrivescirculationbothglobalandlocal:PolarHighPolareasterliesPolarfront/subarcticlow\WesterliesSubtropicalhigh,,PolareasterliesPolarHighWesterliesTradeWindsTradewinds:Polarfront/subarcticlowSpatialdistributionofenergyandtemperaturedrivescirculationbothglobalandlocal:PolarHighPolareasterliesPolarfront/subarcticlow\WesterliesSubtropicalhigh,,PolareasterliesPolarHighWesterliesTradeWindsTradewinds:M:卜EquitoriallowWesterliesTradeWindsTradewindsSubtropicalhighCoupledEarthCyclesEnergyCycleEnergyCycleEstimatesfromriveroutflowsindicate17x109Tons/YearofmaterialistransportedintotheOcean.Another2or3x109Tons/Yearistrappedinreservoirs.80%ofmaterialtransportedisparticulate20%isdissolved0.05mm/yr(mayhavebeenacceleratedbyman,andactualratesmaybemuchlarger)Localratesdependonrelief,precipitation,androcktype.

Localratesdependonrelief,precipitation,androcktype.GlacierseshWaterAtmosphereOceansativevolumesofwateringlaciers,freshwater,

atmosphereandoceans.GlacierseshWaterAtmosphereOceansEstimateoftheWorldWaterBalanceParameterSurfacearea(km2)X106Volume(km3)X106Volume%Equivalentdepth(m)ResidenceTimeOceansandseas3611370942500~4000yearsLakesandreservoirs水库1.550.13<0.010.25~10yearsSwamps湿地<0.1<0.01<0.010.0071-10yearsRiverchannels<0.1<0.01<0.010.003~2weeksSoilmoisture土壤湿度1300.07<0.010.132weeks1yearGroundwater1306041202weeks10,000yearsIcecaps冰盖andglaciers冰川17.83026010-1000yearsAtmosphericwater5040.01<0.010.025~10daysBiosphericwater<0.1<0.01<0.010.001~1weekAmazonis6,000km3/yr(~5xmorethanZaire-Congo)0.0003%ispotableandavailable.Whatarewaterneedsforhumans?Primitiveconditions3to5gallons/dayUrbanuse150gallons/dayUSFreshWaterUse1,340gallons/dayWheredoesthewatergo?omakethingstocleanthingsItemGallons1poundofcotton2,0001poundofgrain-fedbeef8001loafofbread1501car100,000

1kilowattofelectricity801poundofrubber1001poundofsteel251gallonofgasoline101loadoflaundry601ten-minuteshower25-50Somepoints:Alotofwaterisusedforagricultureo56%(76BGD)isconsumptiveuseo20%(28BGD)islostinconveyanceo24%(33BGD)isreturnflowAlotofwaterisusedforthermoelectricpowergenerationo87%ofallindustrialwateruseAsmallsavingsineitherofthesecategorieswouldfreeupsignificantquantitiesforpublicsuppliesWaterUseintheUSin1990FreshWaterUse1990Total339BGDCalifornia35.1Texas20.1Idaho19.7Illinois18.0Colorado12.7Louisiana11.7Michigan11.6NewYork10.5Pennsylvania9.8Indiana9.4Montana9.3Fourstatesaccountfor27%11statesaccountfor50%

Analysisofhumanappropriationofrenewablefreshwatersupply(RFSW)onland.FigureadaptedfromPosteletal.,Science,(271)p.758,Feb.9,1996Posteletal.’sCalculationsCalculationofappropriatedETindirect132billiontonsofbiomassproducedayear(Vitousek,1992).30%usedbypeople.ApproimatepeoplesuseofETfromtheproportionofbiomass30%.Subtractagriculturalirrigation(2,000km3/year)andassumehalfthewater.fromparksandlawnsisirrigation(80km3/year).Inaccessiblerunoff95oftheAmazon,HalfoftheZaire-CongoandallofthePolarrivers7774.km3/year(didnotconsiderothernorthernriversconservative?).Floodwater.11,100km3/yearofrunoffisbaseflow(6).Capacityofman-madereservoirsis5,500km3/year.•Accessiblerunoff=Baseflow+reservoircapacity=12,500.adjustedforaccessible

Withdrawals(consumed)12,000m3/haaverageirrigationwaterapplication.240,000,000haofworldirrigatedarea.2,880km3/year.65%consumed=1,870km3/year.Industrialuse:975km3/year,9%consumed,90km3/year.Municipaluse:300km3/year,17%consumed,50km3/year.Reservoirlosses5%loss,275km3/year.Totalconsumed=2,285km3/year.4)Instreamuse•28.3L/sper1,000population,appliedto1990population,4,700km3/year.•Assuming50%ofwastegetstreatment2,350km3/year.•Neglectsdispersedpollution(agricultural)andfloodwaters.EstimatedwateruseintheUnitedStates,billiongallonsperday(bgd),fordomesticandcommercialpurposes.AdaptedfromSolley,Pierce,andPerlman,1993.RelativeMeritsofSurfaceandSubsurfaceReservoirsSurfaceReservoirsSubsurfaceReservoirsDisadvantagesAdvantagesFewnewsitesfree(inUSA)Manylarge-capacitysitesavailableHighevaporativeloss,evenwherehumidclimateprevailsPracticallynoevaporativelossNeedlargeareasoflandNeedverysmallareasoflandMayfailcatastrophicallyPracticallynodangeroffailureVaryingwatertemperatureWatertemperatureuniformEasilypollutedUsuallyhighbiologicalpurity,althoughpollutioncanoccur

EasilycontaminatedbyradioactivefalloutWatermustbeconveyedNotrapidlycontaminatedbyradioactivefalloutEasilycontaminatedbyradioactivefalloutWatermustbeconveyedActasconveyancesystems,thusobviatingtheneedforpipesorcanalsWatershedHydrologicBudgetsDelineationofawatershed(drainagebasin,riverbasin,catchment)Areathattopographicallyappearstocontributeallthewaterthatflowsthroughagivencrosssectionofastream.Inotherwords,theareaoverwhichwaterflowingalongthesurfacewilleventuallyreachthestream,upstreamofthecross-section.Horizontalprojectionofthisareaisthedrainagearea.Theboundariesofawatershedarecalledadivide,andcanbetracedonatopographicmapbystartingatthelocationofthestreamcross-sectionthendrawingalineawayfromthestreamthatintersectsallcontourlinesatrightangles.Ifyoudothisright,thelinesdrawnfrombothsidesofthestreamshouldintersect.MovingtoeithersideWaterBalanceEquationdtPGin-WaterBalanceEquationdtPGin-QET+GoutdSAtsteady-state:一0dtPG+PG+in+QET+GoutHydrologicProductionRunoff,orHydrologicHydrologicProductionCirculationQandParetheonlyquantitiesthatwecantrytomeasuredirectly.Ifsteadystateisassumed,thesemeasurementscanbeusedtocalibratemodelsofevapotranspirationandgroundwaterflow.

FromandengineeringpointofviewweareinterestedinunderstandingwhatcontrolsQ.Q=P+(Gin-Gout)-ETHowmuchofQisavailabletohumanuse?HowcanweincreaseQ?LakeParabola(Asimplequadraticmodelofthecrosssectionofacircularlake)Hcr2Annr2_HcJ"HJ"Hdh—2nCH2VH()Hdh—2nCH2DischargeintoLakeParabolaIfthereisconstantvolumefluxQm3/dayintothelake,howdoesthedepthdependontime?(Attime0,thedepthisHom)Sincethereisnooutflow,thechargeinstoragemustequaltheinflowMass-balance(waterbalance)equationdVH()ndH(2)ndHQH——dt2cdtcdtThisdifferentialequationcanbesolvedbyseparationofvariables

THcQo_nd/hdhcQH2H2——T=———n22H=2cQnQ=10[m3/day]c=0.1[1/m]0246810121432H[m]T[days]DischargeintoandEvaporationoutofLakeParabolae=rateofevaporation[L/T]dVH()n口=Q-Ae=Q-_HedtcndHndHQc=H-=Q-He=-ecdt_ct/HTH

108Q=10[m3/day]c=0.1[1/m]e=0.03[m/day]Q=10[m3/day]c=0.1[1/m]e=0.03[m/day]4202004006008001000T[days]dHQcSteadyStateSolution=□-—eSteadyStateSolutiondtnHQc(10)(0.1)H=口近10.6mTTen(0.03)Discharge,evapor