ASTM D6170-97(2010)
(Guide)Standard Guide for Selecting a Groundwater Modeling Code
Standard Guide for Selecting a Groundwater Modeling Code
SIGNIFICANCE AND USE
Groundwater modeling has become an important methodology in support of the planning and decision-making processes involved in groundwater management. Groundwater models provide an analytical framework for obtaining an understanding of the mechanisms and controls of groundwater systems and the processes that influence their quality, especially those caused by human intervention in such systems. Increasingly, models are an integral part of water resources assessment, protection, and restoration studies, and provide essential and cost-effective support for planning and screening of alternative policies, regulations, and engineering designs affecting groundwater.
Many different groundwater modeling codes are available, each with their own capabilities, operational characteristics and limitations. Furthermore, each groundwater project has its own requirements with respect to modeling. Therefore, it is important that the most appropriate code is selected for a particular project. This is even more important for projects that require extensive modeling, or where costly decisions are based, in part, on the outcome of modeling-based analysis.
Systematic and comprehensive description of project requirements and code features provides the necessary basis for efficient selection of a groundwater modeling code. This standard guide is intended to encourage comprehensive and consistent description of code capabilities and code requirements in the code selection process, as well as thorough documentation of the code selection process.
SCOPE
1.1 This guide covers a systematic approach to the determination of the requirements for and the selection of computer codes used in a groundwater modeling project. Due to the complex nature of fluid flow and biotic and chemical transport in the subsurface, many different groundwater modeling codes exist, each having specific capabilities and limitations. Furthermore, a wide variety of situations may be encountered in projects where groundwater models are used. Determining the most appropriate code for a particular application requires a thorough analysis of the problem at hand and the required and available resources, as well as detailed description of the functionality of candidate codes.
1.2 The code selection process described in this guide consists of systematic analysis of project requirements and careful evaluation of the match between project needs and the capabilities of candidate codes. Insufficiently documented capabilities of candidate codes may require additional analysis of code functionality as part of the code selection process. Fig. 1 is provided to assist with the determination of project needs in terms of code capabilities, and, if necessary, to determine code capabilities.
1.3 This guide is one of a series of guides on groundwater modeling codes and their applications, such as Guides D5447, D5490, D5609, D5610, D5611, D5718, and D6025 .
1.4 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This guide cannot replace education or experience and should be used in conjunction with professional judgement. Not all aspects of this guide may be applicable in all circumstances. This guide is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this guide be applied without consideration of a project's many unique aspects. The word “Standard” in the title of this document means only that the document has been approved through the ASTM consensus process.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
FIG. 1 Checklist for Groundwater Modeling Nee...
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D6170 − 97 (Reapproved 2010)
Standard Guide for
Selecting a Groundwater Modeling Code
This standard is issued under the fixed designation D6170; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This guide covers a systematic approach to the determi-
responsibility of the user of this standard to establish appro-
nation of the requirements for and the selection of computer
priate safety and health practices and determine the applica-
codes used in a groundwater modeling project. Due to the
bility of regulatory limitations prior to use.
complex nature of fluid flow and biotic and chemical transport
in the subsurface, many different groundwater modeling codes
2. Referenced Documents
exist, each having specific capabilities and limitations.
2.1 ASTM Standards:
Furthermore, a wide variety of situations may be encountered
D653 Terminology Relating to Soil, Rock, and Contained
in projects where groundwater models are used. Determining
Fluids
the most appropriate code for a particular application requires
D5447 Guide forApplication of a Groundwater Flow Model
athoroughanalysisoftheproblemathandandtherequiredand
to a Site-Specific Problem
available resources, as well as detailed description of the
D5490 Guide for Comparing Groundwater Flow Model
functionality of candidate codes.
Simulations to Site-Specific Information
1.2 The code selection process described in this guide
D5609 Guide for Defining Boundary Conditions in Ground-
consists of systematic analysis of project requirements and
water Flow Modeling
careful evaluation of the match between project needs and the
D5610 GuideforDefiningInitialConditionsinGroundwater
capabilities of candidate codes. Insufficiently documented
Flow Modeling
capabilities of candidate codes may require additional analysis
D5611 Guide for Conducting a Sensitivity Analysis for a
of code functionality as part of the code selection process. Fig.
Groundwater Flow Model Application
1 is provided to assist with the determination of project needs
D5718 Guide for Documenting a Groundwater Flow Model
in terms of code capabilities, and, if necessary, to determine
Application
code capabilities.
D6025 Guide for Developing and Evaluating Groundwater
1.3 This guide is one of a series of guides on groundwater
Modeling Codes
modeling codes and their applications, such as Guides D5447,
D5490, D5609, D5610, D5611, D5718, and D6025.
3. Terminology
1.4 This guide offers an organized collection of information
3.1 Definitions of Terms Specific to This Standard:
or a series of options and does not recommend a specific
3.1.1 analytical model—in groundwater modeling, a model
course of action. This guide cannot replace education or
that uses closed form solutions to the governing equations
experience and should be used in conjunction with professional
applicable to groundwater flow and transport processes.
judgement. Not all aspects of this guide may be applicable in
3.1.2 code selection—the process of choosing the appropri-
all circumstances. This guide is not intended to represent or
ate computer code, algorithm, or other analysis technique
replace the standard of care by which the adequacy of a given
capable of simulating those characteristics of the physical
professional service must be judged, nor should this guide be
system required to fulfill the modeling project’s objective(s).
applied without consideration of a project’s many unique
3.1.3 computer code (computer program)—assembly of nu-
aspects. The word “Standard” in the title of this document
merical techniques, bookkeeping, and control language that
means only that the document has been approved through the
represents the model from acceptance of input data and
ASTM consensus process.
instructions to delivery of output.
This guide is under the jurisdiction ofASTM Committee D18 on Soil and Rock
and is the direct responsibility of Subcommittee D18.21 on Groundwater and
Vadose Zone Investigations. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved July 1, 2010. Published September 2010. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1997. Last previous edition approved in 2004 as D6170 – 97 (2004). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/D6170-97R10. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6170 − 97 (2010)
FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality
D6170 − 97 (2010)
FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)
D6170 − 97 (2010)
FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)
D6170 − 97 (2010)
FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)
D6170 − 97 (2010)
FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)
D6170 − 97 (2010)
FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)
D6170 − 97 (2010)
FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)
D6170 − 97 (2010)
FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)
D6170 − 97 (2010)
FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)
D6170 − 97 (2010)
FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)
D6170 − 97 (2010)
FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)
D6170 − 97 (2010)
FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)
D6170 − 97 (2010)
FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)
D6170 − 97 (2010)
FIG. 1 Checklist for Groundwater Modeling Needs and Code Functionality (continued)
3.1.4 conceptual model—an interpretation or working de- 3.1.6 groundwater modeling code—the non-parameterized
scription of the characteristics and dynamics of the physical
computer code used in groundwater modeling to represent a
system.
non-unique, simplified mathematical description of the physi-
cal framework, geometry, active processes, and boundary
3.1.5 functionality—of a groundwater modeling code, the
conditionspresentinareferencesubsurfacehydrologicsystem.
setoffunctionsandfeaturesthecodeofferstheuserintermsof
model framework geometry, simulated processes, boundary
conditions, and analytical and operational capabilities.
D6170 − 97 (2010)
3.1.7 mathematical model—(a) mathematical equations ex- 5. Code Selection Process in Groundwater Modeling
pressing the physical system and including simplifying as-
5.1 Codeselectioningroundwatermodelingisacrucialstep
sumptions; (b) the representation of a physical system by
in the application of groundwater models (see Guide D5447).
mathematical expressions from which the behavior of the
Each groundwater project in which computer-based modeling
system can be deduced with known accuracy.
is performed should include a code selection phase.
3.1.8 model construction—the process of transforming the
conceptual model into a parameterized mathematical form; as
5.2 Code selection is in essence the process of matching a
parametrization requires assumptions regarding spatial and
project’s modeling needs with the documented capabilities of
temporal discretization, model construction requires a priori
existing computer codes.
selection of a computer code.
5.3 Selecting an appropriate code requires analysis and
3.1.9 model schematization—simplification of a conceptual-
systematic description of both the modeling needs and the
ized groundwater system for quantitative, model-based analy-
characteristics of existing groundwater modeling codes.
sis commensurate with project objectives and constraints.
5.4 A perfect match rarely exists between desired code
3.1.10 numerical model—in groundwater modeling,a
characteristics or selection criteria and the capabilities or
model that uses numerical methods to solve the governing
functionality of available codes. Therefore, the selection crite-
equations of the applicable problem.
ria are divided into the following two groups: essential code
3.1.11 semi-analytical model—a mathematical model in
capabilities and non-essential code capabilities. If a candidate
which complex analytical solutions are evaluated using ap-
code does not include the essential capabilities, it should be
proximate techniques, resulting in a solution discrete in either
removed from consideration.
the space or time domain.
3.2 For definitions of other terms used in this guide, see 5.5 The relative importance of the non-essential code capa-
Terminology D653.
bilities needs to be assessed. This may be done by assigning
weighting factors to the considered capabilities (for example,
4. Significance and Use
using weights from one to five according to their relative
4.1 Groundwater modeling has become an important meth- importance). Although such weighing factors are often not
odology in support of the planning and decision-making explicitly mentioned in the code selection process, candidate
processes involved in groundwater management. Groundwater
codes are often ranked implicitly using some kind of weighting
models provide an analytical framework for obtaining an
of the non-essential capabilities.Assigning weighting factors is
understanding of the mechanisms and controls of groundwater
a rather subjective procedure; if a match is difficult to obtain,
systems and the processes that influence their quality, espe-
reassessment of these factors may be necessary. Hence, code
cially those caused by human intervention in such systems.
selection may turn out to be a rather iterative process requiring
Increasingly, models are an integral part of water resources
a significant level of professional judgment and experience.
assessment, protection, and restoration studies, and provide
5.6 Selectingtherightcodeiscriticalinensuringanoptimal
essential and cost-effective support for planning and screening
trade-off between effort and result in a modeling project. The
of alternative policies, regulations, and engineering designs
result can be expressed as the expected effectiveness of the
affecting groundwater.
modeling tasks in terms of prediction accuracy. The effort is
4.2 Many different groundwater modeling codes are
basicallyrepresentedbythemodelingcosts,suchasincurredin
available, each with their own capabilities, operational charac-
becoming familiar with the code, model schematization and
teristics and limitations. Furthermore, each groundwater proj-
model construction, and model-based scenario analysis. Such
ect has its own requirements with respect to modeling.
costs should not be considered independently from those of
Therefore, it is important that the most appropriate code is
field data acquisition, especially those required for the model-
selected for a particular project. This is even more important
ing effort. For a proper assessment of modeling cost, consid-
for projects that require extensive modeling, or where costly
eration should be given to the choice of developing a new code
decisions are based, in part, on the outcome of modeling-based
(ormodifyinganexistingone)versusacquisitionofanexisting
analysis.
code, the implementation and maintenance of the code, com-
4.3 Systematic and comprehensive description of project
puter platform requirements, and the development and main-
requirementsandcodefeaturesprovidesthenecessarybasisfor
tenance of databases.
efficient selection of a groundwater modeling code. This
standard guide is intended to encourage comprehensive and
NOTE 1—The availability of or familiarity with a particular code, or
consistent description of code capabilities and code require-
both, may lead to modeling overkill by using a pre-chosen code requiring
ments in the code selection process, as well as thorough
significantly more preparation in data gathering and model construction
documentation of the code selection process. than necessary for the project. Such modeling overkill may also result
from the user’s inability to limit the number of “essential” code features,
or to discriminate between non-essential code features.
NOTE 2—The belief that use of the “best” or most mathematically
National Research Council (NRC), Committee on Ground Water Modeling
advanced codes will automatically provide predictive reliability and
Assessment,WaterScienceandTechnologyBoard,GroundWaterModels:Scientific
and Regulatory Applications, National Academy Press, Washington, DC, 1990. scientific credibility is false.The technical capability of the modeler or the
D6170 − 97 (2010)
modelingteaminvolvedinthemodelingprojecthasthegreatestimpacton
6.4 The conceptual model, no matter how complex, will
the overall results.
always be a simplified representation of the groundwater
5.7 If different project questions need to be addressed, more system. Furthermore, current limitations in scientific theories
than one code might be needed or different combinations of (and their mathematical representation) and computer capabili-
functions of a single code may be utilized. This is often the ties may require additional simplifications in the conceptual
case when models are used in different stages of the project. model to facilitate computer modeling. Combining the de-
For example, in an early stage of a remediation project, a scription of the conceptual mod
...
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