Designation:D5880−95(Reapproved2006)StandardGuideforSubsurfaceFlowandTransportModeling1ThisstandardisissuedunderthefixeddesignationD5880;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thisguidecoversanoverviewofsubsurfacefluid-flow(groundwater)modeling.Thetermsubsurfacefluidflowisusedtoreducemisunderstandingregardinggroundwater,soilwater,vaporsincludingairinsubsurfacepores,andnon-aqueousphaseliquids.Increasedunderstandingoffluid-flowphenomenaisthecombinedresultoffieldinvestigationsandtheoreticaldevelopmentofmathematicalmethodstodescribetheobservations.Theresultsaremethodsformodelingviscousfluidsandairflow,inadditiontowater,thatarepracticalandappropriate.1.2Thisguideincludesmanytermstoassisttheuserinunderstandingtheinformationpresentedhere.Agroundwatersystem(soilsandwater)mayberepresentedbyaphysical,electrical,ormathematicalmodel,asdescribedin6.4.3.Thisguidefocusesonmathematicalmodels.Thetermmathematicalmodelisdefinedin3.1.11;however,itwillbemostoftenusedtorefertothesubsetofmodelsrequiringacomputer.1.3Thisguideintroducestopicsforwhichotherstandardshavebeendeveloped.TheprocessofapplyingagroundwaterflowmodelisdescribedinGuideD5447.Theprocessincludesdefiningboundaryconditions(GuideD5609),initialconditions(GuideD5610),performingasensitivityanalysis(GuideD5611),anddocumentingaflowmodelapplication(GuideD5718).Otherstepsincludedevelopingaconceptualmodelandcalibratingthemodel.Aspartofcalibration,simulationsarecomparedtosite-specificinformation(GuideD5490),suchaswaterlevels.1.4Modeluseandmisuse,limitations,andsourcesoferrorinmodelingarediscussedinthisstandard.Thisguidedoesnotendorseparticularcomputersoftwareoralgorithmsusedinthemodelinginvestigation.However,thisguidedoesprovidereferencestosomeparticularcodesthatarerepresentativeofdifferenttypesofmodels.1.5...
