1、Designation: D 5447 04Standard Guide forApplication of a Ground-Water Flow Model to a Site-SpecificProblem1This standard is issued under the fixed designation D 5447; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、 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 the application and subsequent docu-mentation of a ground-water flow model to a particular site orprobl
3、em. In this context, “ground-water flow model” refers tothe application of a mathematical model to the solution of asite-specific ground-water flow problem.1.2 This guide illustrates the major steps to take in devel-oping a ground-water flow model that reproduces or simulatesan aquifer system that h
4、as been studied in the field. This guidedoes not identify particular computer codes, software, oralgorithms used in the modeling investigation.1.3 This guide is specifically written for saturated, isother-mal, ground-water flow models. The concepts are applicable toa wide range of models designed to
5、 simulate subsurfaceprocesses, such as variably saturated flow, flow in fracturedmedia, density-dependent flow, solute transport, and mul-tiphase transport phenomena; however, the details of theseother processes are not described in this guide.1.4 This guide is not intended to be all inclusive. Each
6、ground-water model is unique and may require additionalprocedures in its development and application. All such addi-tional analyses should be documented, however, in the modelreport.1.5 This guide is one of a series of standards on ground-water model applications. Other standards have been preparedo
7、n environmental modeling, such as Practice E 978.1.6 This standard does not purport to address all of thesafety problems, 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 re
8、gulatory limitations prior to us1.7 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 th
9、is 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 “S
10、tandard” in the title of thisdocument means only that the document has been approvedthrough the ASTM consensus process.2. Referenced Documents2.1 ASTM Standards:2D 653 Terminology Relating to Soil, Rock, and ContainedFluidsE 978 Practice for Evaluating Environmental Fate Modelsof Chemicals3. Termino
11、logy3.1 Definitions:3.1.1 application verificationusing the set of parametervalues and boundary conditions from a calibrated model toapproximate acceptably a second set of field data measuredunder similar hydrologic conditions.3.1.1.1 DiscussionApplication verification is to be distin-guished from c
12、ode verification, that refers to software testing,comparison with analytical solutions, and comparison withother similar codes to demonstrate that the code represents itsmathematical foundation.3.1.2 boundary conditiona mathematical expression of astate of the physical system that constrains the equ
13、ations of themathematical model.3.1.3 calibration (model application)the process of refin-ing the model representation of the hydrogeologic framework,hydraulic properties, and boundary conditions to achieve adesired degree of correspondence between the model simula-tion and observations of the groun
14、d-water flow system.1This guide is under the jurisdiction ofASTM Committee D18 on Soil and Rockand is the direct responsibility of Subcommittee D18.21 on Ground Water andVadose Zone Investigations.Current edition approved Nov. 1, 2004. Published November 2004. Originallyapproved in 1993. Discontinue
15、d in 2002 and reinstated in 2004 as D544704.2For 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.1Copyright ASTM I
16、nternational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.4 computer code (computer program)the assembly ofnumerical techniques, bookkeeping, and control language thatrepresents the model from acceptance of input data andinstructions to delivery of output.
17、3.1.5 conceptual modelan interpretation or working de-scription of the characteristics and dynamics of the physicalsystem.3.1.6 ground water flow modelapplication of a math-ematical model to represent a site-specific ground water flowsystem.3.1.7 mathematical modelmathematical equations ex-pressing
18、the physical system and including simplifying as-sumptions. The representation of a physical system by math-ematical expressions from which the behavior of the systemcan be deduced with known accuracy.3.1.8 modelan assembly of concepts in the form ofmathematical equations that portray understanding
19、of a naturalphenomenon.3.1.9 sensitivity (model application)the degree to whichthe model result is affected by changes in a selected modelinput representing hydrogeologic framework, hydraulic prop-erties, and boundary conditions.3.2 For definitions of other terms used in this guide, seeTerminology D
20、 653.4. Summary of Guide4.1 The application of a ground-water flow model ideallywould follow several basic steps to achieve an acceptablerepresentation of the physical hydrogeologic system and todocument the results of the model study to the end-user,decision-maker, or regulator. These primary steps
21、 include thefollowing:4.1.1 Define study objectives,4.1.2 Develop a conceptual model,4.1.3 Select a computer code,4.1.4 Construct a ground-water flow model,4.1.5 Calibrate model and perform sensitivity analysis,4.1.6 Make predictive simulations,4.1.7 Document modeling study, and4.1.8 Perform postaud
22、it.4.2 These steps are designed to ascertain and document anunderstanding of a system, the transition from conceptualmodel to mathematical model, and the degree of uncertainty inthe model predictions. The steps presented in this guide shouldgenerally be followed in the order they appear in the guide
23、;however, there is often significant iteration between steps. Allsteps outlined in this guide are required for a model thatsimulates measured field conditions. In cases where the modelis only used to understand a problem conceptually, not all stepsare necessary. For example, if no site-specific data
24、 are avail-able, the calibration step would be omitted.5. Significance and Use5.1 According to the National Research Council (1),3modelapplications are useful tools to:5.1.1 Assist in problem evaluation,5.1.2 Design remedial measures,5.1.3 Conceptualize and study ground-water flow processes,5.1.4 Pr
25、ovide additional information for decision making,and5.1.5 Recognize limitations in data and guide collection ofnew data.5.2 Ground-water models are routinely employed in makingenvironmental resource management decisions. The modelsupporting these decisions must be scientifically defensible anddecisi
26、on-makers must be informed of the degree of uncertaintyin the model predictions. This has prompted some stateagencies to develop standards for ground-water modeling (2).This guide provides a consistent framework within which todevelop, apply, and document a ground-water flow model.5.3 This guide pre
27、sents steps ideally followed whenever aground-water flow model is applied. The ground-water flowmodel will be based upon a mathematical model that may usenumerical, analytical, or any other appropriate technique.5.4 This guide should be used by practicing ground-watermodelers and by those wishing to
28、 provide consistency inmodeling efforts performed under their direction.5.5 Use of this guide to develop and document a ground-water flow model does not guarantee that the model is valid.This guide simply outlines the necessary steps to follow in themodeling process. For example, development of an e
29、quivalentporous media model in karst terrain may not be valid ifsignificant ground-water flow takes place in fractures andsolution channels. In this case, the modeler could follow allsteps in this guide and not end up with a defensible model.6. Procedure6.1 The procedure for applying a ground-water
30、modelincludes the following steps: define study objectives, develop aconceptual model, select a computer code or algorithm, con-struct a ground-water flow model, calibrate the model andperform sensitivity analysis, make predictive simulations,document the modeling process, and perform a postaudit.Th
31、ese steps are generally followed in order, however, there issubstantial overlap between steps, and previous steps are oftenrevisited as new concepts are explored or as new data areobtained. The iterative modeling approach may also require thereconceptualization of the problem. An example of thesefee
32、dback loops is shown in Fig. 1. These basic modeling stepsare discussed below.6.2 Definition of the study objectives is an important step inapplying a ground-water flow model. The objectives aid indetermining the level of detail and accuracy required in themodel simulation. Complete and detailed obj
33、ectives wouldideally be specified prior to any modeling activities.6.3 A conceptual model of a ground-water flow and hydro-logic system is an interpretation or working description of thecharacteristics and dynamics of the physical hydrogeologicsystem. The purpose of the conceptual model is to consol
34、idatesite and regional hydrogeologic and hydrologic data into a setof assumptions and concepts that can be evaluated quantita-tively. Development of the conceptual model requires thecollection and analysis of hydrogeologic and hydrologic datapertinent to the aquifer system under investigation. Stand
35、ard3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.D5447042guides and practices exist that describe methods for obtaininghydrogeologic and hydrologic data.6.3.1 The conceptual model identifies and describes impor-tant aspects of the physical hydrogeolo
36、gic system, including:geologic and hydrologic framework, media type (for example,fractured or porous), physical and chemical processes, hydrau-lic properties, and sources and sinks (water budget). Thesecomponents of the conceptual model may be described eitherin a separate document or as a chapter w
37、ithin the model report.Include illustrations, where appropriate, to support the narra-tive, for example, contour maps, cross sections, or blockdiagrams, or combination thereof. Each aspect of the concep-tual model is described as follows:6.3.1.1 Geologic framework is the distribution and configu-rat
38、on of aquifer and confining units. Of primary interest are thethickness, continuity, lithology, and geologic structure of thoseunits that are relevant to the purpose of the study. The aquifersystem domain, that may be composed of interconnectedaquifers and confining units, often extends beyond the d
39、omainof interest. In this case, describe the aquifer system in detailwithin the domain of interest and at least in general elsewhere.Analysis of the geologic framework results in listings, tabula-tions, or maps, or combination thereof, of the thickness, extent,and properties of each relevant aquifer
40、 and confining unit.6.3.1.2 Hydrologic framework in the conceptual modelincludes the physical extents of the aquifer system, hydrologicfeatures that impact or control the ground-water flow system,analysis of ground-water flow directions, and media type. Theconceptual model must address the degree to
41、 which the aquifersystem behaves as a porous media. If the aquifer system issignificantly fractured or solutioned, the conceptual modelmust address these issues. Hydrologic framework also includesflow system boundaries that may not be physical and canchange with time, such as ground-water divides. F
42、luid potential(head) measurements allow assessment of the rate and direc-tion of ground-water flow. In addition, the mathematical modelis typically calibrated against these values (see 6.5). Waterlevel measurements within the ground-water system are tabu-lated, both spatially and temporally. This an
43、alysis of the flowsystem includes the assessment of vertical and horizontalgradients, delineation of ground-water divides, and mapping offlow lines.6.3.1.3 Hydraulic properties include the transmissive andstorage characteristics of the aquifer system. Specific examplesof hydraulic properties include
44、 transmissivity, hydraulic con-ductivity, storativity, and specific yield. Hydraulic propertiesmay be homogeneous or heterogeneous throughout the modeldomain. Certain properties, such as hydraulic conductivity,may also have directionality, that is, the property may beanisotropic. It is important to
45、document field and laboratorymeasurements of these properties in the conceptual model toset bounds or acceptable ranges for guiding the model calibra-tion.6.3.1.4 Sources and sinks of water to the aquifer systemimpact the pattern of ground-water flow. The most commonexamples of sources and sinks inc
46、lude pumping or injectionwells, infiltration, evapotranspiration, drains, leakage acrossconfining layers and flow to or from surface water bodies.Identify and describe sources and sinks within the aquifersystem in the conceptual model. The description includes therates and the temporal variability o
47、f the sources and sinks. Awater budget should be developed as part of the conceptualmodel.6.3.2 Provide an analysis of data deficiencies and potentialsources of error with the conceptual model. The conceptualmodel usually contains areas of uncertainty due to the lack offield data. Identify these are
48、as and their significance to theconceptual model evaluated with respect to project objectives.In cases where the system may be conceptualized in more thanone way, these alternative conceptual models should be de-scribed and evaluated.6.4 Computer code selection is the process of choosing theappropri
49、ate software algorithm, or other analysis technique,capable of simulating the characteristics of the physical hydro-geologic system, as identified in the conceptual model. Thecomputer code must also be tested for the intended use and bewell documented (3-5).6.4.1 Other factors may also be considered in the decision-making process, such as model analysts experience and thosedescribed below for model construction. Important aspects ofthe model construction process, such as dimensionality, willdetermine the capabilities of the computer code required for themodel. Provide a nar
