1、Designation: D 6170 97 (Reapproved 2004)Standard Guide forSelecting a Ground-Water Modeling Code1This standard is issued under the fixed designation D 6170; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、 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 a systematic approach to the determi-nation of the requirements for and the selection of computercodes used in a
3、ground-water modeling project. Due to thecomplex nature of fluid flow and biotic and chemical transportin the subsurface, many different ground-water modeling codesexist, each having specific capabilities and limitations. Further-more, a wide variety of situations may be encountered inprojects where
4、 ground-water models are used. Determining themost appropriate code for a particular application requires athorough analysis of the problem at hand and the required andavailable resources, as well as detailed description of thefunctionality of candidate codes.1.2 The code selection process described
5、 in this guideconsists of systematic analysis of project requirements andcareful evaluation of the match between project needs and thecapabilities of candidate codes. Insufficiently documentedcapabilities of candidate codes may require additional analysisof code functionality as part of the code sel
6、ection process. Fig.1 is provided to assist with the determination of project needsin terms of code capabilities, and, if necessary, to determinecode capabilities.1.3 This guide is one of a series of guides on ground-watermodeling codes and their applications, such as Guides D 5447,D 5490, D 5609, D
7、 5610, D 5611, D 5718, and D 6025 .1.4 This guide offers an organized collection of informationor a series of options and does not recommend a specificcourse of action. This guide cannot replace education orexperience and should be used in conjunction with professionaljudgement. Not all aspects of t
8、his guide may be applicable inall circumstances. This guide is not intended to represent orreplace the standard of care by which the adequacy of a givenprofessional service must be judged, nor should this guide beapplied without consideration of a projects many uniqueaspects. The word “Standard” in
9、the title of this documentmeans only that the document has been approved through theASTM consensus process.1.5 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 a
10、nd health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 5447 Guide for Application of a Ground-Water FlowModel to a Site-Specific Problem3D 5490 Guide for Com
11、paring Ground-Water Flow ModelSimulations to Site-Specific InformationD 5609 Guide for Defining Boundary Conditions inGround-Water Flow ModelingD 5610 Guide for Defining Initial Conditions in Ground-Water Flow ModelingD 5611 Guide for Conducting a Sensitivity Analysis for aGround-Water Flow Model Ap
12、plicationD 5718 Guide for Documenting a Ground-Water FlowModel ApplicationD 6025 Guide for Developing and Evaluating Ground-Water Modeling Codes3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 analytical modelin ground-water modeling, a modelthat uses closed form solutions to t
13、he governing equationsapplicable to ground-water flow and transport processes.3.1.2 code selectionthe process of choosing the appropri-ate computer code, algorithm, or other analysis techniquecapable of simulating those characteristics of the physicalsystem required to fulfill the modeling projects
14、objective(s).3.1.3 computer code (computer program)assembly ofnumerical techniques, bookkeeping, and control language thatrepresents the model from acceptance of input data andinstructions to delivery of output.3.1.4 conceptual modelan interpretation or working de-scription of the characteristics an
15、d dynamics of the physicalsystem.1This guide is under the jurisdiction of ASTM Committee D18 on Soil and Rockand is the direct responsibility of Subcommittee D18.21 on Ground Water andVadose Zone Investigations.Current edition approved May 1, 2004. Published June 2004. Originallyapproved in 1997. La
16、st previous edition approved in 1997 as D 6170 - 97e1.2For 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.3Withdr
17、awn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.5 functionalityof a ground-water modeling code, theset of functions and features the code offers the user in terms ofmodel framework geometry, simulated processes, boundarycondi
18、tions, and analytical and operational capabilities.FIG. 1 Checklist for Ground-Water Modeling Needs and Code FunctionalityD 6170 97 (2004)2FIG. 1 Checklist for Ground-Water Modeling Needs and Code Functionality (continued)D 6170 97 (2004)3FIG. 1 Checklist for Ground-Water Modeling Needs and Code Fun
19、ctionality (continued)D 6170 97 (2004)4FIG. 1 Checklist for Ground-Water Modeling Needs and Code Functionality (continued)D 6170 97 (2004)5FIG. 1 Checklist for Ground-Water Modeling Needs and Code Functionality (continued)D 6170 97 (2004)6FIG. 1 Checklist for Ground-Water Modeling Needs and Code Fun
20、ctionality (continued)D 6170 97 (2004)7FIG. 1 Checklist for Ground-Water Modeling Needs and Code Functionality (continued)D 6170 97 (2004)8FIG. 1 Checklist for Ground-Water Modeling Needs and Code Functionality (continued)D 6170 97 (2004)9FIG. 1 Checklist for Ground-Water Modeling Needs and Code Fun
21、ctionality (continued)D 6170 97 (2004)10FIG. 1 Checklist for Ground-Water Modeling Needs and Code Functionality (continued)D 6170 97 (2004)11FIG. 1 Checklist for Ground-Water Modeling Needs and Code Functionality (continued)D 6170 97 (2004)12FIG. 1 Checklist for Ground-Water Modeling Needs and Code
22、Functionality (continued)D 6170 97 (2004)13FIG. 1 Checklist for Ground-Water Modeling Needs and Code Functionality (continued)D 6170 97 (2004)14FIG. 1 Checklist for Ground-Water Modeling Needs and Code Functionality (continued)D 6170 97 (2004)153.1.6 ground-water modeling codethe non-parameterizedco
23、mputer code used in ground-water modeling to represent anon-unique, simplified mathematical description of the physi-cal framework, geometry, active processes, and boundaryconditions present in a reference subsurface hydrologic system.3.1.7 mathematical model(a) mathematical equations ex-pressing th
24、e physical system and including simplifying as-sumptions; (b) the representation of a physical system bymathematical expressions from which the behavior of thesystem can be deduced with known accuracy.3.1.8 model constructionthe process of transforming theconceptual model into a parameterized mathem
25、atical form; asparametrization requires assumptions regarding spatial andtemporal discretization, model construction requires a prioriselection of a computer code.3.1.9 model schematizationsimplification of a conceptu-alized ground-water system for quantitative, model-basedanalysis commensurate with
26、 project objectives and constraints.3.1.10 numerical modelin ground-water modeling,amodel that uses numerical methods to solve the governingequations of the applicable problem.3.1.11 semi-analytical modela mathematical model inwhich complex analytical solutions are evaluated using ap-proximate techn
27、iques, resulting in a solution discrete in eitherthe space or time domain.3.2 For definitions of other terms used in this guide, seeTerminology D 653.4. Significance and Use4.1 Ground-water modeling has become an important meth-odology in support of the planning and decision-makingprocesses involved
28、 in ground-water management. Ground-water models provide an analytical framework for obtaining anunderstanding of the mechanisms and controls of ground-watersystems and the processes that influence their quality, espe-cially those caused by human intervention in such systems.Increasingly, models are
29、 an integral part of water resourcesassessment, protection, and restoration studies, and provideessential and cost-effective support for planning and screeningof alternative policies, regulations, and engineering designsaffecting ground water.44.2 Many different ground-water modeling codes are avail
30、-able, each with their own capabilities, operational characteris-tics and limitations. Furthermore, each ground-water projecthas its own requirements with respect to modeling. Therefore,it is important that the most appropriate code is selected for aparticular project. This is even more important fo
31、r projects thatrequire extensive modeling, or where costly decisions arebased, in part, on the outcome of modeling-based analysis.4.3 Systematic and comprehensive description of projectrequirements and code features provides the necessary basis forefficient selection of a ground-water modeling code.
32、 Thisstandard guide is intended to encourage comprehensive andconsistent description of code capabilities and code require-ments in the code selection process, as well as thoroughdocumentation of the code selection process.5. Code Selection Process in Ground-Water Modeling5.1 Code selection in groun
33、d-water modeling is a crucialstep in the application of ground-water models (see Guide D5447). Each ground-water project in which computer-basedmodeling is performed should include a code selection phase.5.2 Code selection is in essence the process of matching aprojects modeling needs with the docum
34、ented capabilities ofexisting computer codes.5.3 Selecting an appropriate code requires analysis andsystematic description of both the modeling needs and thecharacteristics of existing ground-water modeling codes.5.4 A perfect match rarely exists between desired codecharacteristics or selection crit
35、eria and the capabilities orfunctionality of available codes. Therefore, the selection crite-ria are divided into the following two groups: essential codecapabilities and non-essential code capabilities. If a candidatecode does not include the essential capabilities, it should beremoved from conside
36、ration.5.5 The relative importance of the non-essential code capa-bilities needs to be assessed. This may be done by assigningweighting factors to the considered capabilities (for example,using weights from one to five according to their relativeimportance). Although such weighing factors are often
37、notexplicitly mentioned in the code selection process, candidatecodes are often ranked implicitly using some kind of weightingof the non-essential capabilities. Assigning weighting factors isa rather subjective procedure; if a match is difficult to obtain,reassessment of these factors may be necessa
38、ry. Hence, codeselection may turn out to be a rather iterative process requiringa significant level of professional judgment and experience.5.6 Selecting the right code is critical in ensuring an optimaltrade-off between effort and result in a modeling project. Theresult can be expressed as the expe
39、cted effectiveness of themodeling tasks in terms of prediction accuracy. The effort isbasically represented by the modeling costs, such as incurred inbecoming familiar with the code, model schematization andmodel construction, and model-based scenario analysis. Suchcosts should not be considered ind
40、ependently from those offield data acquisition, especially those required for the model-ing effort. For a proper assessment of modeling cost, consid-eration should be given to the choice of developing a new code(or modifying an existing one) versus acquisition of an existingcode, the implementation
41、and maintenance of the code, com-puter platform requirements, and the development and main-tenance of databases.NOTE 1The availability of or familiarity with a particular code, orboth, may lead to modeling overkill by using a pre-chosen code requiringsignificantly more preparation in data gathering
42、and model constructionthan necessary for the project. Such modeling overkill may also resultfrom the users inability to limit the number of “essential” code features,or to discriminate between non-essential code features.NOTE 2The belief that use of the “best” or most mathematicallyadvanced codes wi
43、ll automatically provide predictive reliability and4National Research Council (NRC), Committee on Ground Water ModelingAssessment, Water Science and Technology Board, Ground Water Models: Scientificand Regulatory Applications, National Academy Press, Washington, DC, 1990.D 6170 97 (2004)16scientific
44、 credibility is false. The technical capability of the modeler or themodeling team involved in the modeling project has the greatest impact onthe overall results.55.7 If different project questions need to be addressed, morethan one code might be needed or different combinations offunctions of a sin
45、gle code may be utilized. This is often thecase when models are used in different stages of the project.For example, in an early stage of a remediation project, amodel is used to assist in problem scoping and systemconceptualization, while during the design phase of the project,a model is used to sc
46、reen between alternative remediationtechniques and to detail the selected remediation approach.5.8 If, as a result of the code selection process, a code isselected that requires modification, proper quality assuranceprocedures for code development and testing need to befollowed (see Guide D 6025).6.
47、 Defining Modeling Needs6.1 Following are major steps in evaluating modeling needs:formulating the project-related modeling objectives; determin-ing the required level of analysis (that is, modeling complexity)and reliability in terms of prediction accuracy and sensitivity ofthe project for incorrec
48、t or imprecise answers (that is, accept-able level of uncertainty); conceptualizing and characterizingthe ground-water system involved; and analyzing the con-straints in human and material resources available for thestudy.6.2 Project-related modeling objectives may include: pre-liminary screening of
49、 sites for locating facilities that mayinteract with the ground-water system, risk assessment forexisting or planned facilities, site performance assessmentbased on technical design, environmental impact assessment,optimal control of facility operation, and design of monitoringnetwork.5Modeling objectives often constitute a subset of theproject objectives; some of the project objectives may notrequire examination by means of computer simulation. Projectobjectives are translated into modeling objectives by formulat-ing model (or stress) scena
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