1、Designation: D 5610 94 (Reapproved 2002)Standard Guide forDefining Initial Conditions in Ground-Water Flow Modeling1This standard is issued under the fixed designation D 5610; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers techniques and procedures used indefining initial conditions for modeling saturated ground-wat
3、erflow. The specification of initial conditions is an essential partof conceptualizing and modeling ground-water systems.1.2 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 orexpe
4、rience 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 th
5、isdocument 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:D 653 Terminology Relating to Soil, Rock, and Cont
6、ainedFluids2D 5447 Guide for Application of a Ground-Water FlowModel to a Site-Specific Problem3D 5609 Guide for Defining Boundary Conditions inGround-Water Flow Modeling33. Terminology3.1 Definitions:3.1.1 aquifer, confinedan aquifer bounded above andbelow by confining beds and in which the static
7、head is abovethe top of the aquifer.3.1.2 conceptual modelan interpretation or working de-scription of the characteristics of the physical system.3.1.3 fluxthe volume of fluid crossing a unit cross-sectional surface area per unit time.3.1.4 ground-water flow modelan application of a math-ematical mo
8、del to represent a ground-water flow system.3.1.5 hydraulic conductivity(field aquifer tests), the vol-ume of water at the existing kinematic viscosity that will movein a unit time under unit hydraulic gradient through a unit areameasured at right angles to the direction of flow.3.1.6 hydrologic con
9、ditiona set of ground-water inflowsor outflows, boundary conditions, and hydraulic properties thatcauses potentiometric heads to adopt a distinct pattern.3.1.7 simulationone complete execution of the computerprogram, including input and output.3.1.8 transmissivitythe volume of water at the existingk
10、inematic viscosity that will move in a unit time under a unithydraulic gradient through a unit width of the aquifer.3.1.9 unconfined aquiferan aquifer that has a water table.3.1.10 For definitions of other terms used in this testmethod, see Terminology D 653.4. Significance and Use4.1 Accurate defin
11、ition of initial hydrologic conditions is anessential part of conceptualizing and modeling transientground-water flow, because results of a simulation may beheavily dependent upon the initial conditions.5. Initial Conditions5.1 Initial hydrologic conditions for a flow system arerepresented by the he
12、ad distribution throughout the flowsystem at some particular time corresponding to the antecedenthydrologic conditions in the aquifer system.4The specifiedheads can be considered reference heads; calculated changes inhead through time will be relative to these given heads, and thetime represented by
13、 these heads becomes the reference time.As a convenience, this reference time is usually specified aszero time or initial time. Time is reckoned from this zero timeor initial time. In more formal terms, an initial condition giveshead as a function of position at t = 0; that is, h = f (x, y, z; t= 0)
14、. This notation suggests that, conceptually, initial condi-tions may be regarded as a boundary condition in time.6. Procedure6.1 The following procedures and requirements are pro-posed for establishing initial conditions at a specified time for1This guide is under the jurisdiction of ASTM Committee
15、D18 on Soil and Rockand is the direct responsibility of Subcommittee D18.21 on Ground Water andVadose Zone Investigations.Current edition approved Sept. 15, 1994. Published January 1995.2Annual Book of ASTM Standards, Vol 04.08.3Annual Book of ASTM Standards, Vol 04.09.4Franke, O. L., Reilly, T. E.,
16、 and Bennett, G. D., “Definition of Boundary andInitial Conditions in the Analysis of Ground-Water Flow SystemsAn Introduc-tion,” Techniques of Water-Resources Investigations of the United States GeologicalSurvey, Book 3, Chapter B5, 1987.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box
17、C700, West Conshohocken, PA 19428-2959, United States.the following conditions of model simulation.6.1.1 Defining Steady-State Initial Conditions for aTransient-State Simulation of Head DistributionSelect fieldconditions that represent, at least approximately, an equilib-rium condition. The steady-s
18、tate head distribution must besimulated by modeling hydrologic conditions, includingboundary conditions4that produced the observed distributionof heads. Exact representation of the field prototype flowsystem is not possible to achieve in practice, but an acceptablyclose representation may be used as
19、 the initial condition (seeGuide D 5447).NOTE 1The use of model-generated head values for initial conditionsfor the transient-state simulation assures that the initial heads and themodel boundary conditions and hydrologic parameters are consistent. Ifthe field-measured head values were used as initi
20、al conditions, the modelresponse in the early time steps would reflect not only the model stressunder study but the adjustment of model head values to offset the lack ofcorrespondence between model boundary conditions, aquifer hydraulicproperties, and the initial head values.6.1.2 Defining a Transie
21、nt-State Initial Condition for aTransient-State Simulation of Absolute HeadSimulatetransient-state absolute heads for field conditions by simulatingboundary conditions and hydraulic properties of the flowsystem. This period of absolute head simulation must besufficiently long that antecedent stresse
22、s, that is, stresses on thesystem predating the simulation period, are insignificant. Thesimulation period must be for a sufficiently long antecedentperiod that transient heads prior to the selected initial time areacceptably close to the field heads. The transient-state headdistribution is used as
23、initial conditions for absolute transienthead distribution with the new stress imposed.6.1.3 Defining the Initial Head for Steady- or Transient-State Simulation of Head Change in Response to a StressApply the principle of superposition and define the initial headin the flow system as zero. Superposi
24、tion modeling predictsonly the water-level changes related to a specific stress anddoes not predict absolute heads (heads referenced to a commondatum). If superposition is applicable to the problem, absoluteheads can be obtained by adding the head change obtained bysuperposition analysis to field he
25、ads. Superposition may beapplied only to systems that exhibit a linear response to stress.57. Report7.1 Completely document the definition of initial conditionsfor model simulation. Such documentation will be a part of theoverall documentation of the model. Include the followingitems pertaining to t
26、he formulation of initial conditions in themodel report:7.1.1 Describe the natural physical processes operating onthe system, and7.1.2 Describe the simulation of the system processes up tothe initial time (t = 0) representation of each boundary.Evaluate the sensitivity analysis of the boundaries and
27、 state theconditions of stress over which the modeled boundary condi-tions are appropriate.8. Keywords8.1 aquifers; boundary condition; ground water model;transmissivityASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin
28、this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must
29、 be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of ther
30、esponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700,
31、 West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).5Reilly, T. E., Franke, O. L., and Bennett, G. D., The Principle of Superpositionand its Application in Ground-Water Hydraulics, U.S. Geological Survey, Open-fileReport 84-459, 1984.D 5610 94 (2002)2
