1、Designation: D6170 17Standard Guide forSelecting a Groundwater Modeling Code1This standard is issued under the fixed designation D6170; 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 parenthe
2、ses 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 a systematic approach to the determi-nation of the requirements for and the selection of computercodes used in a groundwater modeling
3、project. Due to thecomplex nature of fluid flow and biotic and chemical transportin the subsurface, many different groundwater modeling codesexist, each having specific capabilities and limitations.Furthermore, a wide variety of situations may be encounteredin projects where groundwater models are u
4、sed. Determiningthe most appropriate code for a particular application requiresa thorough 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 in this guideconsists of
5、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 selection process. Fig.1 is p
6、rovided 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 groundwatermodeling codes and their applications, such as Guides D5447,D5490, D5609, D5610, D5611, D5718, and D6025.
7、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 this guide may be applicable inall c
8、ircumstances. 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 the title of this documentmeans onl
9、y 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 and health practices and determine t
10、he applica-bility of regulatory limitations prior to use.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 ProblemD5490 Guide for Comparing Groundwater Flow ModelSimulations
11、 to Site-Specific InformationD5609 Guide for Defining Boundary Conditions in Ground-water Flow ModelingD5610 Guide for Defining Initial Conditions in GroundwaterFlow ModelingD5611 Guide for Conducting a Sensitivity Analysis for aGroundwater Flow Model ApplicationD5718 Guide for Documenting a Groundw
12、ater Flow ModelApplicationD6025 Guide for Developing and Evaluating GroundwaterModeling Codes (Withdrawn 2017)33. Terminology3.1 For definitions of other terms used in this guide, seeTerminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 analytical modelin groundwater modeling, a
13、modelthat uses closed form solutions to the governing equationsapplicable to groundwater flow and transport processes.3.2.2 code selectionthe process of choosing the appropri-ate computer code, algorithm, or other analysis techniquecapable of simulating those characteristics of the physicalsystem to
14、 fulfill the modeling projects objective(s).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 Jan. 1, 2017. Published January 2017. Originallyapprove
15、d in 1997. Last previous edition approved in 2010 as D6170 97 (2010).DOI: 10.1520/D6170-17.2For 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 Su
16、mmary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.*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 StatesThis int
17、ernational standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) C
18、ommittee.1FIG. 1 Checklist for Groundwater Modeling Needs and Code FunctionalityD6170 172FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)D6170 173FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)D6170 174FIG. 1 Checklist for Groundwa
19、ter Modeling Needs and Code Functionality (continued)D6170 175FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)D6170 176FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)D6170 177FIG. 1 Checklist for Groundwater Modeling Needs and Code
20、 Functionality (continued)D6170 178FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)D6170 179FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)D6170 1710FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)
21、D6170 1711FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)D6170 1712FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)D6170 1713FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)D6170 17143.2.3 conceptu
22、al modelan interpretation or working de-scription of the characteristics and dynamics of the physicalsystem.3.2.4 functionalityof a groundwater modeling code, theset of functions and features the code offers the user in terms ofmodel framework geometry, simulated processes, boundaryconditions, and a
23、nalytical and operational capabilities.3.2.5 groundwater modeling codethe non-parameterizedcomputer code used in groundwater modeling to represent anon-unique, simplified mathematical description of the physi-cal framework, geometry, active processes, and boundaryconditions present in a reference su
24、bsurface hydrologic system.FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)D6170 17153.2.6 mathematical model(a) mathematical equations ex-pressing the physical system and including simplifying as-sumptions; (b) the representation of a physical system bymathematical
25、 expressions from which the behavior of thesystem can be deduced with known accuracy.3.2.7 model constructionthe process of transforming theconceptual model into a parameterized mathematical form; asparametrization requires assumptions regarding spatial andtemporal discretization, model construction
26、 requires a prioriselection of a computer code.3.2.8 model schematizationsimplification of a conceptual-ized groundwater system for quantitative, model-based analy-sis commensurate with project objectives and constraints.3.2.9 numerical modelin groundwater modeling, a modelthat uses numerical method
27、s to solve the governing equationsof the applicable problem.3.2.10 semi-analytical modela mathematical model inwhich complex analytical solutions are evaluated using ap-proximate techniques, resulting in a solution discrete in eitherthe space or time domain.4. Significance and Use4.1 Groundwater mod
28、eling has become an important meth-odology in support of the planning and decision-makingprocesses involved in groundwater management. Groundwatermodels provide an analytical framework for obtaining anunderstanding of the mechanisms and controls of groundwatersystems and the processes that influence
29、 their quality, espe-cially those caused by human intervention in such systems.Increasingly, models are an integral part of water resourcesassessment, protection, and restoration studies, and provideneeded and cost-effective support for planning and screening ofalternative policies, regulations, and
30、 engineering designs af-fecting groundwater.44.2 Many different groundwater modeling codes areavailable, each with their own capabilities, operational charac-teristics and limitations. Furthermore, each groundwater proj-ect has its own requirements with respect to modeling.Therefore, it is important
31、 that the most appropriate code isselected for a particular project. This is even more importantfor projects that require extensive modeling, or where costlydecisions are based, in part, on the outcome of modeling-basedanalysis.4.3 Systematic and comprehensive description of projectrequirements and
32、code features provides the necessary basis forefficient selection of a groundwater modeling code. 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 cod
33、e selection process.5. Code Selection Process in Groundwater Modeling5.1 Code selection in groundwater modeling is a crucial stepin the application of groundwater models (see Guide D5447).Each groundwater project in which computer-based modelingis performed should include a code selection phase.5.2
34、Code selection is in essence the process of matching aprojects modeling needs with the documented capabilities ofexisting computer codes.5.3 Selecting an appropriate code requires analysis andsystematic description of both the modeling needs and thecharacteristics of existing groundwater modeling co
35、des.5.4 A perfect match rarely exists between desired codecharacteristics or selection criteria 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
36、candidatecode does not include the essential capabilities, it should beremoved from consideration.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 on
37、e to five according to their relativeimportance). Although such weighing factors are often 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
38、 procedure; if a match is difficult to obtain,reassessment of these factors may be necessary. 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 necessary for an optimaltrade-off betw
39、een effort and result in a modeling project. Theresult can be expressed as the expected 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 cons
40、truction, and model-based scenario analysis. Suchcosts should not be considered independently from those offield data acquisition, especially those needed for the modelingeffort. For a proper assessment of modeling cost, considerationshould be given to the choice of developing a new code (ormodifyin
41、g an existing one) versus acquisition of an existingcode, the implementation 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
42、 a pre-chosen code requiringsignificantly more preparation in data gathering 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.NO
43、TE 2The belief that use of the “best” or most mathematicallyadvanced codes will automatically provide predictive reliability andscientific credibility is false. The technical capability of the modeler or themodeling team involved in the modeling project has the greatest impact onthe overall results.
44、54National Research Council (NRC), Committee on Ground Water ModelingAssessment, Water Science and Technology Board, Ground Water Models: Scientificand Regulatory Applications, National Academy Press, Washington, DC, 1990.5Simmons, C. R., and Cole, C. R., Guidelines for Selecting Codes forGround-Wat
45、er Transport Modeling of Low-Level Waste Burial Sites; Volume 1 Guideline Approach, PNL-4980 Vol 1, Pacific Northwest Laboratory, Richland, WA,1985.D6170 17165.7 If different project questions need to be addressed, morethan one code might be needed or different combinations offunctions of a single c
46、ode 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 screen
47、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 D6025).6. Defin
48、ing 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 incorrect or i
49、mprecise answers (that is, accept-able level of uncertainty); conceptualizing and characterizingthe groundwater 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 sites for locating facilities that mayinteract with the groundwater system, risk assessment forexisting or planned facilities, site performance assessmentbased on technical design, environmental impact assessment,optimal control of facility operation
