ASTM D6025-96(2008)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D6025 − 96 (Reapproved 2008)
Standard Guide for
Developing and Evaluating Groundwater Modeling Codes
This standard is issued under the fixed designation D6025; 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 software design, programming, testing, and use, but also for
code maintenance and updating.
1.1 This guide covers a systematic approach to the
development, testing, evaluation, and documentation of
1.5 Quality assurance in the development of groundwater
groundwater modeling codes. The procedures presented con-
modeling codes cannot guarantee acceptable quality of the
stitute the quality assurance framework for a groundwater
code or a groundwater modeling study in which the code has
modeling code. They include code review, testing, and evalu-
been used. However, adequate quality assurance can provide
ation using quantitative and qualitative measures. This guide
safeguards against the use in a modeling study of faulty codes
applies to both the initial development and the subsequent
or incorrect theoretical considerations and assumptions.
maintenance and updating of groundwater modeling codes. Furthermore, there is no way to guarantee that modeling-based
advice is entirely correct, nor that the groundwater model used
1.2 When the development of a groundwater modeling code
in the preparation of the advice (or any scientific model or
is initiated, procedures are formulated to ensure that the final
theory, for that matter) can ever be proven to be entirely
product conforms with the design objectives and specifications
correct. Rather, a model can only be invalidated by disagree-
and that it correctly performs the incorporated functions.These
ment of its predictions with independently derived observa-
procedures cover the formulation and evaluation of the code’s
tions of the studied system because of incorrect application of
theoretical foundation and code design criteria, the application
the selected code, the selection of an inappropriate code, the
of coding standards and practices, and the establishment of the
use of an inadequately tested code, or invalidity of or errors in
code’s credentials through review and systematic testing of its
the underlying theoretical framework.
functional design and through evaluation of its performance
characteristics.
1.6 This guide is one of a series of guides on groundwater
modeling codes and their applications, such as Guides D5447,
1.3 Thecode’sfunctionalityneedstobedefinedinsufficient
D5490, D5611, D5609, D5610, and D5718. Other standards
detail for potential users to assess the code’s utility as well as
have been prepared on environmental modeling, such as
to enable the code developers to design a meaningful code
Practice E978.
testing strategy. Comprehensive testing of a code’s function-
ality and performance is accomplished through a variety of test
1.7 Complete adherence to this guide may not always be
methods. Determining the importance of the tested functions
feasible.Ifthisguideisnotintegrallyfollowed,theelementsof
and the ratio of tested versus non-tested functions provides an
noncompliance should be clearly identified and the reasons for
indication of the completeness of the testing.
the partial compliance should be given. For example, partial
compliance might result from inadequacy of existing field
1.4 Groundwater modeling codes are subject to the software
techniques for measuring relevant model parameters, specifi-
life cycle concept that consists of a design phase, a develop-
cally in complex systems.
ment phase, and an operational phase. During the operational
phase the software is maintained, evaluated regularly, and
1.8 This guide offers an organized collection of information
changed as additional requirements are identified. Therefore,
or a series of options and does not recommend a specific
qualityassuranceproceduresshouldnotonlybeestablishedfor
course of action. This document cannot replace education or
experienceandshouldbeusedinconjunctionwithprofessional
judgment. Not all aspects of this guide may be applicable in all
circumstances. This ASTM standard is not intended to repre-
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
sent or replace the standard of care by which the adequacy of
Vadose Zone Investigations.
a given professional service must be judged, nor should this
Current edition approved Sept. 15, 2008. Published November 2008. Originally
document be applied without consideration of a project’s many
approved in 1996. Last previous edition approved in 1996 as D6025 – 96 (2002).
unique aspects. The word “Standard” in the title of this
DOI: 10.1520/D6025-96R08.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6025 − 96 (2008)
document means only that the document has been approved verifieddoesnotimplythatagroundwatermodelapplication
through the ASTM consensus process. constructed with the code is verified.
NOTE 1—In groundwater modeling, the term “validation” is sometimes
2. Referenced Documents
used to describe the process of determining how well a groundwater
2.1 ASTM Standards:
modeling code’s theoretical foundation and computer implementation
D653 Terminology Relating to Soil, Rock, and Contained describe actual system behavior in terms of the degree of correlation
between calculated and independently observed cause-and-effect re-
Fluids
sponses of the reference groundwater system for which the code has been
D5447 Guide forApplication of a Groundwater Flow Model
developed (1,3). This process is also referred to as field demonstration,
to a Site-Specific Problem
field comparison, or extended verification (4).
D5490 Guide for Comparing Groundwater Flow Model
NOTE 2—Validation as described in Note 1 is by nature a subjective and
Simulations to Site-Specific Information
open-ended process. As there is no practical way to determine that a
D5609 Guide for Defining Boundary Conditions in Ground- groundwater modeling code correctly represents the reference system, the
code can never be considered “validated.” Therefore, this guide does not
water Flow Modeling
endorse the use of the term validation in the context of groundwater
D5610 GuideforDefiningInitialConditionsinGroundwater
modeling (1,3,4).
Flow Modeling
3.1.2 computer code (computer program), n— the assembly
D5611 Guide for Conducting a Sensitivity Analysis for a
of numerical techniques, bookkeeping, and control language
Groundwater Flow Model Application
that represents a model from acceptance of input data and
D5718 Guide for Documenting a Groundwater Flow Model
Application instructions to delivery of output.
E978 Practice for Evaluating Mathematical Models for the
3.1.3 functionality, n— of a groundwater modeling code,the
Environmental Fate of Chemicals (Withdrawn 2002)
setoffunctionsandfeaturesthecodeofferstheuserintermsof
model framework geometry, simulated processes, boundary
3. Terminology
conditions, and analytical and operational capabilities.
3.1 Definitions:
3.1.4 groundwater model application, n— a nonunique,
3.1.1 code verification, n— in groundwater modeling, the
simplified mathematical description of one or more subsurface
process of demonstrating the consistency, completeness,
components of a local or regional hydrologic system, coded in
correctness, and accuracy of a groundwater modeling code
a computer programing language, together with a quantifica-
with respect to its design criteria by evaluating the functional-
tion of the simulated system in the form of framework
ity and operational characteristics of the code and testing
geometry, boundary conditions, system and process
embedded algorithms and internal data transfers through ex-
parameters, and system stresses.
ecution of problems for which independent benchmarks are
available (1). 3.1.4.1 Discussion—As defined in 3.1.4, a groundwater
3.1.1.1 Discussion—In software engineering, verification is model application is a representation of an actual hydrologic
the process of demonstrating consistency, completeness, and system; it should not be confused with the generic computer
correctness of the software (2). Practice E978 defines verifica- code used in formulating the groundwater model. This guide
tion as “.the examination of the numerical technique in the
concerns only the development, testing, and documentation of
computer code to ascertain that it truly represents the concep- generic simulation computer codes, not groundwater model
tual model and that there are no inherent problems with
applications.
obtaining a solution.” In this guide, the term code verification
3.1.5 groundwater modeling, n—the process of developing
is used. The objective of the code verification process is
groundwater models.
threefold: (1) to check the correctness of the program logic and
the computational accuracy of the algorithms used to solve the 3.1.6 groundwater modeling code, n—the nonparametrized
governing equations; (2) to ensure that the computer code is
computer code used in groundwater modeling to represent a
fully operational (no programming errors); and (3) to evaluate nonunique, simplified mathematical description of the physical
the performance of the code with respect to all of its designed
framework, geometry, active processes, and boundary condi-
and inherent functions (1).
tions present in a reference subsurface hydrologic system.
Acode can be considered “verified” when all its functions
3.1.6.1 Discussion—The term “nonparameterized computer
and operational characteristics have been tested and have
code” refers to a generalized computer program in which
met specific performance criteria, established at the begin-
values of parameters can be specified by the user.
ning of the verification procedure. Considering a code
3.1.7 quality assurance (QA), n—in the development of a
groundwater modeling code, the procedural and operational
framework put in place by the organization managing the code
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
development project, to ensure technically and scientifically
Standards volume information, refer to the standard’s Document Summary page on
adequate execution of all project tasks, and to ensure that the
the ASTM website.
resulting software product is functional and reliable.
The last approved version of this historical standard is referenced on
www.astm.org.
4 3.2 For definitions of other terms used in this guide, see
The boldface numbers in parentheses refer to a list of references at the end of
this standard. Terminology D653.
D6025 − 96 (2008)
4. Significance and Use 5.2.2 Assumptions made in deriving the mathematical
framework,
4.1 Groundwater modeling has become an important meth-
5.2.3 Dimensionality, and spatial and temporal
odology in support of the planning and decision-making
discretization,
processes involved in groundwater management. Groundwater
5.2.4 Type and form of computed entities,
models provide an analytical framework for obtaining an
5.2.5 Type and form of code operation control,
understanding of the mechanisms and controls of groundwater
5.2.6 Code structure, and programming language,
systems and the processes that influence their quality, espe-
5.2.7 Input/output structure and applicable data exchange
cially those caused by human intervention in such systems.
formats,
Increasingly, models are an integral part of water resources
5.2.8 User interface,
assessment, protection, and restoration studies and provide
5.2.9 Computer platforms for implementation, and
essential and cost-effective support for planning and screening
5.2.10 Type, contents, structure, and level of detail of
of alternative policies, regulations, and engineering designs
documentation.
affecting groundwater. It is therefore important that before
groundwater modeling codes are used as planning and 5.3 The development of a specific groundwater modeling
code may be part of a research or development project, based
decision-making tools, their credentials are established and
onanexistingmathematicalmodel,orderivedfromanexisting
their suitability determined through systematic evaluation of
set of modeling codes.
their correctness, performance characteristics, and applicabil-
5.3.1 Code development in groundwater modeling is often
ity. This becomes even more important because of the increas-
ing complexity of the hydrologic systems for which new part of research aimed at acquiring new, quantitative knowl-
edge about nature through observation, hypothesizing, and
modeling codes are being developed.
verifyingdeducedrelationships,leadingtotheestablishmentof
4.2 Qualityassuranceingroundwatermodelingprovidesthe
a credible theoretical framework for the observed phenomena.
mechanisms and framework to ensure that the analytic tools
The resulting research model represents a fundamental under-
used in preparing decisions are based on the best available
standing of the studied groundwater system.
techniques and methods. A well-executed quality assurance
5.3.2 The object for model research in groundwater is a
program in groundwater modeling provides the information
subset of the hydrologic system, called the reference system. It
necessary to evaluate the reliability of the performed analysis
contains selected elements of the global hydrologic system.
andtheleveltowhichtheresultingadvicemaybeincorporated
The selection of a particular reference system is influenced by
in decision-making regarding the management of groundwater
regulatory and management priorities, and by the nature of the
resources.
hydrologic system (Fig. 1). The conceptual model of the
4.3 This guide is intended to encourage consistency and
selected reference system forms the basis for quantifying the
completeness in the development and evaluation of existing
causal relationships among various components of this system,
and new groundwater modeling codes by describing appropri-
and between this system and its environment. These relation-
ate code development and quality assurance procedures and
ships are defined mathematically, resulting in a mathematical
techniques.
model. If the solution of the mathematical equations is com-
plex or when many repetitious calculations are required, the
4.4 In the past, some groundwater modeling codes have
use of computers is essential. Thi
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