River 包说明.doc
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River 包说明.doc

River包说明.doc

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River包说明Stream包General-Head(GHB)BoundaryConditionsTheprimarydifferencesbetweentheGeneral-HeadboundaryandtheConstantHeadboundaryare:themodelsolvesfortheheadvaluesintheGeneral-HeadgridcellswhereastheheadvaluesarespecifiedinConstantHeadcells.theGeneral-HeadgridcellsdonotactasinfinitesourcesofwaterwhereasConstantHeadcellscanprovideaninfiniteamountofwaterasrequiredtomaintainthespecifiedhead.Therefore,undersomecircumstances,theGeneral-Headgridcellsmaybecomedrycells.TheGeneral-HeadBoundaryPackagerequiresthefollowinginformationforeachGeneral-Headgridcell:BoundaryHead:Thisistheheadoftheexternalsource/sink.Thisheadmaybephysicallybased,suchasalargelake,ormaybeobtainedthroughmodelcalibration.Conductance:Theconductanceisanumericalparameterthatrepresentstheresistancetoflowbetweentheboundaryheadandthemodeldomain.Drain(DRN)BoundaryConditionsMODFLOW'sDrainPackageisdesignedtosimulatetheeffectsoffeaturessuchasagriculturaldrains,whichremovewaterfromtheaquiferatarateproportionaltothedifferencebetweentheheadintheaquiferandsomefixedheadorelevation.TheDrainpackageassumesthedrainhasnoeffectiftheheadintheaquiferfallsbelowthefixedheadofthedrain.TheDrainPackagerequiresthefollowinginformationasinputforeachcellcontainingthisboundarycondition:HeadElevation:Thedrainelevation,ordrainheadofthefreesurfaceofwaterwithinthedrain.Thedrainisassumedtorunonlypartiallyfull,sothattheheadwithinthedrainisapproximatelyequaltothemedianelevationofthedrain.BottomElevation:Elevationofthebottomofthedrain(forSEAWATsimulationsonly).Conductance:Thedrainconductanceisalumpedcoefficientdescribingtheheadlossbetweenthedrainandthegroundwatersystem.Thislossiscausedbyconvergingflowpatternsnearthedrain,thepresenceofforeignmaterialaroundthedrain,channelbedmaterials,thedrainwall,andthedegreetowhichthedrainpipeopeningsmaybeblockedbychemicalprecipitates,plantroots,etc.Thereisnogeneralformulationforcalculatingdrainconductance.Inmostsituations,thedetailedinformationrequiredtocalculatedrainconductanceisnotavai