ASTM D5447-17

Standard Guide for Application of a Numerical Groundwater Flow Model to a Site-Specific Problem

SIGNIFICANCE AND USE
5.1 Model applications (1),4 are useful tools to:  
5.1.1 Assist in problem evaluation,  
5.1.2 Design remedial measures,  
5.1.3 Conceptualize and study groundwater flow processes,  
5.1.4 Provide additional information for decision making, and  
5.1.5 Recognize limitations in data and guide collection of new data.  
5.2 Groundwater models are routinely employed in making environmental resource management decisions. The model supporting these decisions should be scientifically defensible and decision-makers informed of the degree of uncertainty in the model predictions. This has prompted some state agencies to develop standards for groundwater modeling (2). This guide provides a consistent framework within which to develop, apply, and document a groundwater flow model.  
5.3 This guide presents steps ideally followed whenever a groundwater flow model is applied. The groundwater flow model will be based upon a mathematical model that may use numerical, analytical, or other appropriate technique.  
5.4 This guide should be used by practicing groundwater modelers and by those wishing to provide consistency in modeling efforts performed under their direction.  
5.5 Use of this guide to develop and document a groundwater flow model does not guarantee that the model is valid. This guide simply outlines the necessary steps to follow in the modeling process. For example, development of an equivalent porous media model in karst terrain may not be valid if significant groundwater flow takes place in fractures and solution channels. In this case, the modeler could follow the steps in this guide and not end up with a defensible model.
SCOPE
1.1 This guide covers the application and subsequent documentation of a groundwater flow model to a particular site or problem. In this context, “groundwater flow model” refers to the application of a mathematical model to the solution of a site-specific groundwater flow problem.  
1.2 This guide illustrates the major steps to take in developing a groundwater flow model that reproduces or simulates an aquifer system that has been studied in the field. This guide does not identify particular computer codes, software, or algorithms used in the modeling investigation.  
1.3 This guide is specifically written for saturated, isothermal, groundwater flow models. The concepts are applicable to a wide range of models designed to simulate subsurface processes, such as variably saturated flow, flow in fractured media, density-dependent flow, solute transport, and multiphase transport phenomena; however, the details of these other processes are not described in this guide.  
1.4 This guide is not intended to be all inclusive. Each groundwater model is unique and may require additional procedures in its development and application. All such additional analyses should be documented, however, in the model report.  
1.5 This guide is one of a series of standards on groundwater model applications. Other standards include D5981, D5490, D5609, D5610, D5611, and D6033.  
1.6 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.7 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances. This ASTM standard 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 document be applied without consideration of a project's many unique aspects. The word “Standard” in the title of this docume...

General Information

• Status: Published
• Publication Date: 14-Dec-2017
• ICS: 13.060.10 - Water of natural resources
• Technical Committee: D18 - Soil and Rock
• Drafting Committee: D18.21 - Groundwater and Vadose Zone Investigations

Relations

• Replaces: ASTM D5447-04(2010) - Standard Guide for Application of a Groundwater Flow Model to a Site-Specific Problem
• Effective Date: 15-Dec-2017
• Refers: ASTM D6033-16 - Standard Guide for Describing the Functionality of a Groundwater Modeling Code
• Effective Date: 01-Jul-2016
• Refers: ASTM D5609-16 - Standard Guide for Defining Boundary Conditions in Groundwater Flow Modeling
• Effective Date: 01-Mar-2016
• Refers: ASTM D5611-94(2016) - Standard Guide for Conducting a Sensitivity Analysis for a Groundwater Flow Model Application
• Effective Date: 01-Jan-2016
• Refers: ASTM D653-14 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Aug-2014
• Refers: ASTM D653-11 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Sep-2011
• Refers: ASTM D653-09 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Jan-2009
• Refers: ASTM D653-08a - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Dec-2008
• Refers: ASTM D653-08 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Nov-2008
• Refers: ASTM D5609-94(2015)e1 - Standard Guide for Defining Boundary Conditions in Groundwater Flow Modeling
• Effective Date: 15-Sep-2008
• Refers: ASTM D6033-96(2008) - Standard Guide for Describing the Functionality of a Groundwater Modeling Code
• Effective Date: 15-Sep-2008
• Refers: ASTM D5609-94(2008) - Standard Guide for Defining Boundary Conditions in Groundwater Flow Modeling
• Effective Date: 15-Sep-2008
• Refers: ASTM D5490-93(2008) - Standard Guide for Comparing Groundwater Flow Model Simulations to Site-Specific Information
• Effective Date: 15-Sep-2008
• Refers: ASTM D5981-96(2008) - Standard Guide for Calibrating a Groundwater Flow Model Application (Withdrawn 2017)
• Effective Date: 15-Sep-2008
• Refers: ASTM D5611-94(2008) - Standard Guide for Conducting a Sensitivity Analysis for a Groundwater Flow Model Application
• Effective Date: 15-Sep-2008

Overview

ASTM D5447-17: Standard Guide for Application of a Numerical Groundwater Flow Model to a Site-Specific Problem provides a comprehensive framework for developing, applying, and documenting numerical groundwater flow models tailored to specific sites. Published by ASTM International, this standard is instrumental for environmental professionals, hydrogeologists, consultants, and regulatory agencies engaged in groundwater studies, resource management, and remediation planning.

Groundwater flow models are powerful tools for analyzing how water moves through saturated subsurface environments. ISO-compliant modeling methods help stakeholders make scientifically defensible decisions, assess environmental impacts, and design effective remedial interventions. ASTM D5447-17 structures the modeling process to promote consistency, transparency, and robust documentation of site-specific analyses.

Key Topics

ASTM D5447-17 outlines the essential steps for numerical groundwater flow modeling, ensuring clarity and consistency:

• Defining Study Objectives: Clearly outlining the goals and requirements of the groundwater modeling project.
• Conceptual Model Development: Building an understanding of the physical characteristics and dynamics of the groundwater system, including geologic frameworks and hydrologic features.
• Selection of Computer Code: Choosing suitable software or analytical techniques to simulate identified hydrogeological processes.
• Construction of Numerical Model: Translating conceptual understanding into a numerical or mathematical format, including appropriate discretization, boundary, and initial conditions.
• Model Calibration and Sensitivity Analysis: Adjusting model parameters to achieve correspondence with observed data, and assessing how variations in input parameters affect model results.
• Predictive Simulations: Running model scenarios to predict groundwater responses under various conditions or management strategies.
• Documentation and Post-Audit: Preparing detailed reports for stakeholders and, when feasible, conducting post-audits to verify predictive performance.

These steps foster rigorous project execution and ensure decision-makers are informed of uncertainties and data limitations inherent in groundwater modeling.

Applications

ASTM D5447-17 is widely applicable in the following areas:

• Environmental Site Assessments: Evaluating contamination migration, plume evolution, and the effectiveness of remedial measures at hazardous waste sites or brownfields.
• Water Resource Management: Supporting sustainable groundwater extraction policies, aquifer recharge studies, and wellfield design.
• Regulatory Compliance: Assisting agencies and industries in meeting environmental regulations that require scientifically defensible groundwater assessments.
• Infrastructure Planning: Informing the design and placement of infrastructure such as landfills, dams, and tunnels, where groundwater flow may present risks or influence project feasibility.
• Research and Education: Serving as a reference framework for academic studies and the professional development of groundwater modelers.

The guide emphasizes that, while it sets out best practices, judgment and adaptation are essential, as each site presents unique challenges and data needs.

Related Standards

ASTM D5447-17 is part of a suite of standards designed to improve groundwater modeling quality and reliability. Related standards include:

• ASTM D653: Terminology Relating to Soil, Rock, and Contained Fluids
• ASTM D5490: Guide for Comparing Groundwater Flow Model Simulations to Site-Specific Information
• ASTM D5609: Guide for Defining Boundary Conditions in Groundwater Flow Modeling
• ASTM D5610: Guide for Defining Initial Conditions in Groundwater Flow Modeling
• ASTM D5611: Guide for Conducting a Sensitivity Analysis for a Groundwater Flow Model Application
• ASTM D6033: Guide for Describing the Functionality of a Groundwater Modeling Code

Referencing and integrating these standards ensures a consistent, high-quality approach to groundwater modeling across diverse projects.

---

Keywords: ASTM D5447-17, numerical groundwater flow model, groundwater modeling, environmental site assessment, hydrogeology, resource management, model calibration, sensitivity analysis, ASTM groundwater standards.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:D5447 −17
Standard Guide for
Application of a Numerical Groundwater Flow Model to a
Site-Specific Problem
This standard is issued under the fixed designation D5447; 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* experienceandshouldbeusedinconjunctionwithprofessional
judgment. Not all aspects of this guide may be applicable in all
1.1 This guide covers the application and subsequent docu-
circumstances. This ASTM standard is not intended to repre-
mentation of a groundwater flow model to a particular site or
sent or replace the standard of care by which the adequacy of
problem. In this context, “groundwater flow model” refers to
a given professional service must be judged, nor should this
the application of a mathematical model to the solution of a
document be applied without consideration of a project’s many
site-specific groundwater flow problem.
unique aspects. The word “Standard” in the title of this
1.2 This guide illustrates the major steps to take in devel-
document means only that the document has been approved
oping a groundwater flow model that reproduces or simulates
through the ASTM consensus process.
an aquifer system that has been studied in the field. This guide
1.8 This international standard was developed in accor-
does not identify particular computer codes, software, or
dance with internationally recognized principles on standard-
algorithms used in the modeling investigation.
ization established in the Decision on Principles for the
1.3 This guide is specifically written for saturated,
Development of International Standards, Guides and Recom-
isothermal, groundwater flow models. The concepts are appli-
mendations issued by the World Trade Organization Technical
cable to a wide range of models designed to simulate subsur-
Barriers to Trade (TBT) Committee.
face processes, such as variably saturated flow, flow in frac-
tured media, density-dependent flow, solute transport, and
2. Referenced Documents
multiphase transport phenomena; however, the details of these
2.1 ASTM Standards:
other processes are not described in this guide.
D653 Terminology Relating to Soil, Rock, and Contained
1.4 This guide is not intended to be all inclusive. Each
Fluids
groundwater model is unique and may require additional
D5490 Guide for Comparing Groundwater Flow Model
procedures in its development and application. All such addi-
Simulations to Site-Specific Information
tional analyses should be documented, however, in the model
D5609 Guide for Defining Boundary Conditions in Ground-
report.
water Flow Modeling
D5610 GuideforDefiningInitialConditionsinGroundwater
1.5 This guide is one of a series of standards on groundwa-
Flow Modeling
termodelapplications.OtherstandardsincludeD5981,D5490,
D5611 Guide for Conducting a Sensitivity Analysis for a
D5609, D5610, D5611, and D6033.
Groundwater Flow Model Application
1.6 This standard does not purport to address all of the
D5981 Guide for Calibrating a Groundwater Flow Model
safety concerns, if any, associated with its use. It is the
Application (Withdrawn 2017)
responsibility of the user of this standard to establish appro-
D6033 Guide for Describing the Functionality of a Ground-
priate safety, health, and environmental practices and deter-
water Modeling Code
mine the applicability of regulatory limitations prior to use.
1.7 This guide offers an organized collection of information
3. Terminology
or a series of options and does not recommend a specific
3.1 Definitions:
course of action. This document cannot replace education or
1 2
This guide is under the jurisdiction ofASTM CommitteeD18 on Soil and Rock For referenced ASTM standards, visit the ASTM website, www.astm.org, or
and is the direct responsibility of Subcommittee D18.21 on Groundwater and contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Vadose Zone Investigations. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Dec. 15, 2017. Published January 2018. Originally the ASTM website.
approved in 1993. Last previous edition approved in 2010 as D5447–04(2010). The last approved version of this historical standard is referenced on
DOI: 10.1520/D5447-17. www.astm.org.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5447−17
3.1.1 For commondefinitionsoftechnicaltermsusedinthis 5. Significance and Use
standard, refer to Terminology D653. 4
5.1 Model applications (1), are useful tools to:
3.2 Definitions of Terms Specific to This Standard: 5.1.1 Assist in problem evaluation,
5.1.2 Design remedial measures,
3.2.1 boundary condition, n—in hydrogeologic properties,a
mathematical expression that constrains the equations of the 5.1.3 Conceptualize and study groundwater flow processes,
5.1.4 Provide additional information for decision making,
mathematical model to account for the addition or removal of
fluid or solutes to or from the mathematical model. and
5.1.5 Recognize limitations in data and guide collection of
3.2.2 calibration (model application), n—in hydrogeologic
new data.
properties, the process of refining the model representation of
the hydrogeologic framework, hydraulic properties, and
5.2 Groundwater models are routinely employed in making
boundary conditions to achieve a desired degree of correspon- environmental resource management decisions. The model
dence between the model simulation and observations of the
supporting these decisions should be scientifically defensible
groundwater flow system. and decision-makers informed of the degree of uncertainty in
the model predictions. This has prompted some state agencies
3.2.3 groundwater flow model, n—in hydrogeologic
to develop standards for groundwater modeling (2). This guide
properties, application of a mathematical model to represent a
provides a consistent framework within which to develop,
site-specific groundwater flow system.
apply, and document a groundwater flow model.
3.2.4 model,n—inhydrogeologicproperties,anassemblyof
5.3 This guide presents steps ideally followed whenever a
concepts in the form of mathematical equations that portray
groundwater flow model is applied. The groundwater flow
understanding of a natural phenomenon.
model will be based upon a mathematical model that may use
3.2.5 sensitivity (model application), n—in hydrogeologic
numerical, analytical, or other appropriate technique.
properties, the degree to which the model result is affected by
5.4 This guide should be used by practicing groundwater
changes in a selected model input representing hydrogeologic
modelers and by those wishing to provide consistency in
framework, hydraulic properties, and boundary conditions.
modeling efforts performed under their direction.
3.3 The following terms are contained in Terminology
5.5 Use of this guide to develop and document a ground-
D653, but are included here for the convenience of the user:
water flow model does not guarantee that the model is valid.
3.3.1 conceptual model, n—in hydrogeologic properties,an
This guide simply outlines the necessary steps to follow in the
interpretation or working description of the characteristics and
modeling process. For example, development of an equivalent
dynamics of the physical system.
porous media model in karst terrain may not be valid if
significant groundwater flow takes place in fractures and
4. Summary of Guide
solution channels. In this case, the modeler could follow the
4.1 The application of a groundwater flow model ideally
steps in this guide and not end up with a defensible model.
would follow several basic steps to achieve an acceptable
representation of the physical hydrogeologic system and to
6. Procedure
document the results of the model study to the end-user,
6.1 The procedure for applying a groundwater model in-
decision-maker, or regulator. These primary steps include the
cludes the following steps: define study objectives, develop a
following:
conceptual model, select a computer code or algorithm, con-
4.1.1 Define study objectives,
struct a groundwater flow model, calibrate the model and
4.1.2 Develop a conceptual model,
perform sensitivity analysis, make predictive simulations,
4.1.3 Select a computer code,
document the modeling process, and perform a post-audit.
4.1.4 Construct a groundwater flow model,
These steps are generally followed in order, however, there is
4.1.5 Calibrate model and perform sensitivity analysis,
substantial overlap between steps, and previous steps are often
4.1.6 Make predictive simulations,
revisited as new concepts are explored or as new data are
4.1.7 Document modeling study, and obtained.Theiterativemodelingapproachmayalsorequirethe
reconceptualization of the problem. An example of these
4.1.8 Perform postaudit.
feedback loops is shown in Fig. 1. These basic modeling steps
4.2 These steps are designed to ascertain and document an
are discussed below.
understanding of a system, the transition from conceptual
6.2 Definition of the study objectives is an important step in
model to mathematical model, and the degree of uncertainty in
applying a groundwater flow model. The objectives aid in
the model predictions.The steps presented in this guide should
determining the level of detail and accuracy needed in the
generally be followed in the order they appear in the guide;
model simulation. Complete and detailed objectives would
however, there is often significant iteration between steps. All
ideally be specified prior to modeling activities.
of the steps outlined in this guide are required for a model that
simulates measured field conditions. In cases where the model
is only used to understand a problem conceptually, some steps
are unnecessary. For example, if no site-specific data are
The boldface numbers in parentheses refer to the list of references at the end of
available, the calibration step would be omitted. this standard.
D5447−17
domain of interest. In this case, describe the aquifer system in
detail within the domain of interest and at least in general
elsewhere. Analysis of the geologic framework results in
listings, tabulations, or maps, or combination thereof, of the
thickness, extent, and properties of each relevant aquifer and
confining unit.
6.3.1.2 Hydrologic framework in the conceptual model
includes the physical extents of the aquifer system, hydrologic
features that impact or control the groundwater flow system,
analysis of groundwater flow directions, and media type. The
conceptual model should address the degree to which the
aquifer system behaves as a porous media. If the aquifer
system is significantly fractured or solutioned, the conceptual
model should address these issues. Hydrologic framework also
includes flow system boundaries that may not be physical and
can change with time, such as groundwater divides. Fluid
potential(head)measurementsallowassessmentoftherateand
direction of groundwater flow. In addition, the mathematical
model is typically calibrated against these values (see 6.5).
Water level measurements within the groundwater system are
tabulated, both spatially and temporally. This analysis of the
flow system includes the assessment of vertical and horizontal
gradients, delineation of groundwater divides, and mapping of
flow lines.
6.3.1.3 Hydraulic properties include the transmissive and
storage characteristics of the aquifer system. Specific examples
of hydraulic properties include transmissivity, hydraulic
conductivity, storativity, and specific yield. Hydraulic proper-
FIG. 1 Flow Chart of the Modeling Process
ties may be homogeneous or heterogeneous throughout the
model domain. Certain properties, such as hydraulic
conductivity, may also have directionality, that is, the property
6.3 A conceptual model of a groundwater flow and hydro-
may be anisotropic. It is important to document field and
logic system is an interpretation or working description of the
laboratory measurements of these properties in the conceptual
characteristics and dynamics of the physical hydrogeologic
modeltosetboundsoracceptablerangesforguidingthemodel
system. The purpose of the conceptual model is to consolidate
calibration.
site and regional hydrogeologic and hydrologic data into a set
of assumptions and concepts that can be evaluated quantita-
6.3.1.4 Sources and sinks of water to the aquifer system
tively. Development of the conceptual model requires the
impact the pattern of groundwater flow. The most common
collection and analysis of hydrogeologic and hydrologic data
examples of sources and sinks include pumping or injection
pertinent to the aquifer system under investigation. Standard
wells, infiltration, evapotranspiration, drains, leakage across
guides and practices exist that describe methods for obtaining
confining layers and flow to or from surface water bodies.
hydrogeologic and hydrologic data.
Identify and describe sources and sinks within the aquifer
6.3.1 The conceptual model identifies and describes impor-
system in the conceptual model. The description includes the
tant aspects of the physical hydrogeologic system, including:
rates and the temporal variability of the sources and sinks. A
geologic and hydrologic framework, media type (for example,
water budget should be developed as part of the conceptual
fractured or porous), physical and chemical processes, hydrau-
model.
lic properties, and sources and sinks (water budget). These
6.3.2 Provide an analysis of data deficiencies and potential
components of the conceptual model may be described either
sources of error with the conceptual model. The conceptual
in a separate document or as a chapter within the model report.
model usually contains areas of uncertainty due to the lack of
Include illustrations, where appropriate, to support the
field data. Identify these areas and their significance to the
narrative, for example, contour maps, cross sections, or block
conceptual model evaluated with respect to project objectives.
diagrams, or combination thereof. Each aspect of the concep-
In cases where the system may be conceptualized in more than
tual model is described as follows:
one way, these alternative conceptual models should be de-
6.3.1.1 Geologic framework is the distribution and configu-
scribed and evaluated.
ration of aquifer and confining units. Of primary interest are
6.4 Computer code selection is the process of choosing the
the thickness, continuity, lithology, and geologic structure of
those units that are relevant to the purpose of the study. The appropriate software algorithm, or other analysis technique,
capable of simulating the characteristics of the physical hydro-
aquifer system domain, that may be composed of intercon-
nected aquifers and confining units, often extends beyond the geologic system, as identified in the conceptual model. The
D5447−17
computercodeshouldalsobetestedfortheintendeduseandbe along the three-dimensional boundary surface of the aquifer
well documented (2-4). system and to internal sources and sinks (8). Boundary
conditions fall into one of five categories: specified head or
6.4.1 Other factors may also be considered in the decision-
Dirichlet, specified flux or Neumann, and mixed or Cauchy
making process, such as model analyst’s experience and those
described below for model construction. Important aspects of boundary conditions, free surface boundary, and seepage face.
It is desirable to include only natural hydrologic boundaries as
the model construction process, such as dimensionality, will
determine the capabilities of the computer code needed for the boundary conditions in the model. Most numerical models,
model.Provideanarrativeinthemodelingreportjustifyingthe however, employ a grid that has to end somewhere. Thus, it is
computer code selected for the model study. often unavoidable to specify artificial boundaries at the edges
of the model. When these grid boundaries are sufficiently
6.5 Groundwater flow m
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D5447 − 04 (Reapproved 2010) D5447 − 17
Standard Guide for
Application of a Numerical Groundwater Flow Model to a
Site-Specific Problem
This standard is issued under the fixed designation D5447; 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 Scope*
1.1 This guide covers the application and subsequent documentation of a groundwater flow model to a particular site or
problem. In this context, “groundwater flow model” refers to the application of a mathematical model to the solution of a
site-specific groundwater flow problem.
1.2 This guide illustrates the major steps to take in developing a groundwater flow model that reproduces or simulates an aquifer
system that has been studied in the field. This guide does not identify particular computer codes, software, or algorithms used in
the modeling investigation.
1.3 This guide is specifically written for saturated, isothermal, groundwater flow models. The concepts are applicable to a wide
range of models designed to simulate subsurface processes, such as variably saturated flow, flow in fractured media,
density-dependent flow, solute transport, and multiphase transport phenomena; however, the details of these other processes are
not described in this guide.
1.4 This guide is not intended to be all inclusive. Each groundwater model is unique and may require additional procedures in
its development and application. All such additional analyses should be documented, however, in the model report.
1.5 This guide is one of a series of standards on groundwater model applications. Other standards haveinclude D5981been,
D5490prepared, D5609on, D5610environmental, D5611modeling, such as Practice , and E978D6033.
1.6 This standard does not purport to address all of the safety problems,concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and
determine the applicability of regulatory limitations prior to ususe.
1.7 This guide offers an organized collection of information or a series of options and does not recommend a specific course
of action. This document cannot replace education or experience and should be used in conjunction with professional judgment.
Not all aspects of this guide may be applicable in all circumstances. This ASTM standard 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 document 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.
1.8 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D653 Terminology Relating to Soil, Rock, and Contained Fluids
D5490 Guide for Comparing Groundwater Flow Model Simulations to Site-Specific Information
D5609 Guide for Defining Boundary Conditions in Groundwater Flow Modeling
D5610 Guide for Defining Initial Conditions in Groundwater Flow Modeling
D5611 Guide for Conducting a Sensitivity Analysis for a Groundwater Flow Model Application
This guide is under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.21 on Groundwater and Vadose
Zone Investigations.
Current edition approved Aug. 1, 2010Dec. 15, 2017. Published September 2010January 2018. Originally approved in 1993. Discontinued in 2002 and reinstated in 2004
as D5447–04. Last previous edition approved in 20042010 as D5447D5447–04(2010).–04. DOI: 10.1520/D5447-04(2010).10.1520/D5447-17.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5447 − 17
E978D5981 Practice for Evaluating Mathematical Models for the Environmental Fate of ChemicalsGuide for Calibrating a
Groundwater Flow Model Application (Withdrawn 2002)2017)
D6033 Guide for Describing the Functionality of a Groundwater Modeling Code
3. Terminology
3.1 Definitions:
3.1.1 For common definitions of technical terms used in this standard, refer to Terminology D653.
3.2 Definitions:Definitions of Terms Specific to This Standard:
3.1.1 application verification—using the set of parameter values and boundary conditions from a calibrated model to
approximate acceptably a second set of field data measured under similar hydrologic conditions.
3.1.1.1 Discussion—
Application verification is to be distinguished from code verification, that refers to software testing, comparison with analytical
solutions, and comparison with other similar codes to demonstrate that the code represents its mathematical foundation.
3.2.1 boundary condition—condition, n—in hydrogeologic properties, a mathematical expression of a state of the physical
system that constrains the equations of the mathematical model to account for the addition or removal of fluid or solutes to or from
the mathematical model.
3.2.2 calibration (model application)—application), n—in hydrogeologic properties, the process of refining the model
representation of the hydrogeologic framework, hydraulic properties, and boundary conditions to achieve a desired degree of
correspondence between the model simulation and observations of the groundwater flow system.
3.1.4 computer code (computer program)—the assembly of numerical techniques, bookkeeping, and control language that
represents the model from acceptance of input data and instructions to delivery of output.
3.1.5 conceptual model—an interpretation or working description of the characteristics and dynamics of the physical system.
3.2.3 groundwater flow model—model, n—in hydrogeologic properties, application of a mathematical model to represent a
site-specific groundwater flow system.
3.1.7 mathematical model—mathematical equations expressing the physical system and including simplifying assumptions. The
representation of a physical system by mathematical expressions from which the behavior of the system can be deduced with
known accuracy.
3.2.4 model—model, n—in hydrogeologic properties, an assembly of concepts in the form of mathematical equations that
portray understanding of a natural phenomenon.
3.2.5 sensitivity (model application)—application), n—in hydrogeologic properties, the degree to which the model result is
affected by changes in a selected model input representing hydrogeologic framework, hydraulic properties, and boundary
conditions.
3.3 For definitions of other terms used in this guide, see The following terms are contained in Terminology D653., but are
included here for the convenience of the user:
3.3.1 conceptual model, n—in hydrogeologic properties, an interpretation or working description of the characteristics and
dynamics of the physical system.
4. Summary of Guide
4.1 The application of a groundwater flow model ideally would follow several basic steps to achieve an acceptable
representation of the physical hydrogeologic system and to document the results of the model study to the end-user,
decision-maker, or regulator. These primary steps include the following:
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 groundwater flow model,
4.1.5 Calibrate model and perform sensitivity analysis,
4.1.6 Make predictive simulations,
4.1.7 Document modeling study, and
4.1.8 Perform postaudit.
4.2 These steps are designed to ascertain and document an understanding of a system, the transition from conceptual model to
mathematical model, and the degree of uncertainty in the model predictions. The steps presented in this guide should generally be
The last approved version of this historical standard is referenced on www.astm.org.
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followed in the order they appear in the guide; however, there is often significant iteration between steps. All of the steps outlined
in this guide are required for a model that simulates measured field conditions. In cases where the model is only used to understand
a problem conceptually, not all some steps are necessary.unnecessary. For example, if no site-specific data are available, the
calibration step would be omitted.
5. Significance and Use
5.1 According to the National Research Council Model applications (1), model applications are useful tools to:
5.1.1 Assist in problem evaluation,
5.1.2 Design remedial measures,
5.1.3 Conceptualize and study groundwater flow processes,
5.1.4 Provide additional information for decision making, and
5.1.5 Recognize limitations in data and guide collection of new data.
5.2 Groundwater models are routinely employed in making environmental resource management decisions. The model
supporting these decisions mustshould be scientifically defensible and decision-makers must be informed of the degree of
uncertainty in the model predictions. This has prompted some state agencies to develop standards for groundwater modeling (2).
This guide provides a consistent framework within which to develop, apply, and document a groundwater flow model.
5.3 This guide presents steps ideally followed whenever a groundwater flow model is applied. The groundwater flow model will
be based upon a mathematical model that may use numerical, analytical, or any other appropriate technique.
5.4 This guide should be used by practicing groundwater modelers and by those wishing to provide consistency in modeling
efforts performed under their direction.
5.5 Use of this guide to develop and document a groundwater flow model does not guarantee that the model is valid. This guide
simply outlines the necessary steps to follow in the modeling process. For example, development of an equivalent porous media
model in karst terrain may not be valid if significant groundwater flow takes place in fractures and solution channels. In this case,
the modeler could follow allthe steps in this guide and not end up with a defensible model.
6. Procedure
6.1 The procedure for applying a groundwater model includes the following steps: define study objectives, develop a conceptual
model, select a computer code or algorithm, construct a groundwater flow model, calibrate the model and perform sensitivity
analysis, make predictive simulations, document the modeling process, and perform a postaudit.post-audit. These steps are
generally followed in order, however, there is substantial overlap between steps, and previous steps are often revisited as new
concepts are explored or as new data are obtained. The iterative modeling approach may also require the reconceptualization of
the problem. An example of these feedback loops is shown in Fig. 1. These basic modeling steps are discussed below.
6.2 Definition of the study objectives is an important step in applying a groundwater flow model. The objectives aid in
determining the level of detail and accuracy requiredneeded in the model simulation. Complete and detailed objectives would
ideally be specified prior to any modeling activities.
6.3 A conceptual model of a groundwater flow and hydrologic system is an interpretation or working description of the
characteristics and dynamics of the physical hydrogeologic system. The purpose of the conceptual model is to consolidate site and
regional hydrogeologic and hydrologic data into a set of assumptions and concepts that can be evaluated quantitatively.
Development of the conceptual model requires the collection and analysis of hydrogeologic and hydrologic data pertinent to the
aquifer system under investigation. Standard guides and practices exist that describe methods for obtaining hydrogeologic and
hydrologic data.
6.3.1 The conceptual model identifies and describes important aspects of the physical hydrogeologic system, including:
geologic and hydrologic framework, media type (for example, fractured or porous), physical and chemical processes, hydraulic
properties, and sources and sinks (water budget). These components of the conceptual model may be described either in a separate
document or as a chapter within the model report. Include illustrations, where appropriate, to support the narrative, for example,
contour maps, cross sections, or block diagrams, or combination thereof. Each aspect of the conceptual model is described as
follows:
6.3.1.1 Geologic framework is the distribution and configuratonconfiguration of aquifer and confining units. Of primary interest
are the thickness, continuity, lithology, and geologic structure of those units that are relevant to the purpose of the study. The
aquifer system domain, that may be composed of interconnected aquifers and confining units, often extends beyond the domain
of interest. In this case, describe the aquifer system in detail within the domain of interest and at least in general elsewhere.
Analysis of the geologic framework results in listings, tabulations, or maps, or combination thereof, of the thickness, extent, and
properties of each relevant aquifer and confining unit.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
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FIG. 1 Flow Chart of the Modeling Process
6.3.1.2 Hydrologic framework in the conceptual model includes the physical extents of the aquifer system, hydrologic features
that impact or control the groundwater flow system, analysis of groundwater flow directions, and media type. The conceptual
model mustshould address the degree to which the aquifer system behaves as a porous media. If the aquifer system is significantly
fractured or solutioned, the conceptual model mustshould address these issues. Hydrologic framework also includes flow system
boundaries that may not be physical and can change with time, such as groundwater divides. Fluid potential (head) measurements
allow assessment of the rate and direction of groundwater flow. In addition, the mathematical model is typically calibrated against
these values (see 6.5). Water level measurements within the groundwater system are tabulated, both spatially and temporally. This
analysis of the flow system includes the assessment of vertical and horizontal gradients, delineation of groundwater divides, and
mapping of flow lines.
6.3.1.3 Hydraulic properties include the transmissive and storage characteristics of the aquifer system. Specific examples of
hydraulic properties include transmissivity, hydraulic conductivity, storativity, and specific yield. Hydraulic properties may be
homogeneous or heterogeneous throughout the model domain. Certain properties, such as hydraulic conductivity, may also have
directionality, that is, the property may be anisotropic. It is important to document field and laboratory measurements of these
properties in the conceptual model to set bounds or acceptable ranges for guiding the model calibration.
6.3.1.4 Sources and sinks of water to the aquifer system impact the pattern of groundwater flow. The most common examples
of sources and sinks include pumping or injection wells, infiltration, evapotranspiration, drains, leakage across confining layers and
flow to or from surface water bodies. Identify and describe sources and sinks within the aquifer system in the conceptual model.
The description includes the rates and the temporal variability of the sources and sinks. A water budget should be developed as
part of the conceptual model.
6.3.2 Provide an analysis of data deficiencies and potential sources of error with the conceptual model. The conceptual model
usually contains areas of uncertainty due to the lack of field data. Identify these areas and their significance to the conceptual model
evaluated with respect to project objectives. In cases where the system may be conceptualized in more than one way, these
alternative conceptual models should be described and evaluated.
6.4 Computer code selection is the process of choosing the appropriate software algorithm, or other analysis technique, capable
of simulating the characteristics of the physical hydrogeologic system, as identified in the conceptual model. The computer code
mustshould also be tested for the intended use and be well documented (3-2-54).
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6.4.1 Other factors may also be considered in the decision-making process, such as model analyst’s experience and those
described below for model construction. Important aspects of the model construction process, such as dimensionality, will
determine the capabilities of the computer code requiredneeded for the model. Provide a narrative in the modeling report justifying
the computer code selected for the model study.
6.5 Groundwater flow model construction is the process of transforming the conceptual model into a mathematical form. The
groundwater flow model typically consists of two parts, the data set and the computer code. The model construction process
includes building the data set utilized by the computer code. Fundamental components of the groundwater flow model include:
dimensionality, discretization, boundary and initial conditions, and hydraulic properties.
6.5.1 Spatial dimensionality is determined both by t
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