ASTM_D_5609_-_16.pdf

Designation:D560916Standard Guide forDefining Boundary Conditions in Groundwater FlowModeling1This standard is issued under the fixed designation D5609;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope*1.1 This guide covers the specification of appropriateboundary conditions that are to be considered part of concep-tualizing and modeling groundwater systems.This guide de-scribes techniques that can be used in defining boundaryconditions and their appropriate application for modelingsaturated groundwater flow model simulations.1.2 This guide is one of a series of standards on groundwa-ter flow model applications.Defining boundary conditions is astep in the design and construction of a model that is treatedgenerally in Guide D5447.1.3 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.4 This guide offers an organized collection of informationor a series of options and does not recommend a specificcourse of action.This document cannot replace education orexperience and should be used in conjunction with professionaljudgment.Not all aspects of this guide may be applicable in allcircumstances.This ASTM standard is not intended to repre-sent or replace the standard of care by which the adequacy ofa given professional service must be judged,nor should thisdocument be applied without consideration of a projects manyunique aspects.The word“Standard”in the title of thisdocument means only that the document has been approvedthrough the ASTM consensus process.2.Referenced Documents2.1 ASTM Standards:2D653 Terminology Relating to Soil,Rock,and ContainedFluidsD5447 Guide for Application of a Groundwater Flow Modelto a Site-Specific Problem3.Terminology3.1 For common definitions of terms in this standard,referto Terminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 confined aquiferin hydrogeology,an aquiferbounded above and below by confining beds and in which thestatic head is above the top of the aquifer3.2.2 boundaryin hydrogeology,the geometrical configu-ration of the surface enclosing the model domain.3.2.3 boundary conditionin hydrogeology,a mathematicalexpression of the state of the physical system that constrainsthe equations of the mathematical model.3.2.4 fluxin hydrogeology,the volume of fluid crossing aunit cross-sectional surface area per unit time.3.2.5 groundwater flow modelin groundwater hydraulics,an application of a mathematical model to the solution of agroundwater flow problem.3.2.6 hydrologic conditionin groundwater hydraulics,aset of groundwater inflows or outflows,boundary conditions,and hydraulic properties that cause potentiometric heads toadopt a distinct pattern.4.Significance and Use4.1 Accurate definition of boundary conditions is an impor-tant part of conceptualizing and modeling groundwater flowsystems.This guide describes the properties of the mostcommon boundary conditions encountered in groundwatersystems and discusses major aspects of their definition andapplication in groundwater models.It also discusses thesignificance and specification of boundary conditions for somefield situations and some common errors in specifying bound-ary conditions in groundwater models.5.Types of Boundaries5.1 The flow of groundwater is described in the general caseby partial differential equations.Quantitative modeling of agroundwater system entails the solution of those equationssubject to site-specific boundary conditions.1This guide is under the jurisdiction ofASTM Committee D18 on Soil and Rockand is the direct responsibility of Subcommittee D18.21 on Groundwater andVadose Zone Investigations.Current edition approved March 1,2016.Published March 2016.Originallyapproved in 1994.Last previous edition approved in 2015 as D5609 94(2015)1.DOI:10.1520/D5609-16.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.2 Types of Modeled Boundary ConditionsFlow modelboundary conditions can be classified as specified head orDirichlet,specified flux or Neumann,a combination of speci-fied head and flux,or Cauchy,free surface boundary,andseepage-face.Each of these types of boundaries and some oftheir variations are discussed below.5.2.1 Specified Head,or Dirichlet,Boundary TypeAs