ASTM D5447-04(2010)
(Guide)Standard Guide for Application of a Groundwater Flow Model to a Site-Specific Problem
Standard Guide for Application of a Groundwater Flow Model to a Site-Specific Problem
SIGNIFICANCE AND USE
According to the National Research Council (1), model applications are useful tools to:
Assist in problem evaluation,
Design remedial measures,
Conceptualize and study groundwater flow processes,
Provide additional information for decision making, and
Recognize limitations in data and guide collection of new data.
Groundwater models are routinely employed in making environmental resource management decisions. The model supporting these decisions must 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.
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.
This guide should be used by practicing groundwater modelers and by those wishing to provide consistency in modeling efforts performed under their direction.
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 all 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 have been prepared on environmental modeling, such as Practice E978.
1.6 This standard does not purport to address all of the safety problems, 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 us
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 t...
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Designation:D5447 −04 (Reapproved 2010)
Standard Guide for
Application of a 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
does not identify particular computer codes, software, or 2. Referenced Documents
algorithms used in the modeling investigation. 2
2.1 ASTM Standards:
1.3 This guide is specifically written for saturated, D653 Terminology Relating to Soil, Rock, and Contained
isothermal, groundwater flow models. The concepts are appli- Fluids
cable to a wide range of models designed to simulate subsur- E978 Practice for Evaluating Mathematical Models for the
face processes, such as variably saturated flow, flow in frac- Environmental Fate of Chemicals (Withdrawn 2002)
tured media, density-dependent flow, solute transport, and
3. Terminology
multiphase transport phenomena; however, the details of these
other processes are not described in this guide.
3.1 Definitions:
3.1.1 application verification—using the set of parameter
1.4 This guide is not intended to be all inclusive. Each
values and boundary conditions from a calibrated model to
groundwater model is unique and may require additional
approximate acceptably a second set of field data measured
procedures in its development and application. All such addi-
under similar hydrologic conditions.
tional analyses should be documented, however, in the model
3.1.1.1 Discussion—Application verification is to be distin-
report.
guished from code verification, that refers to software testing,
1.5 This guide is one of a series of standards on groundwa-
comparison with analytical solutions, and comparison with
ter model applications. Other standards have been prepared on
other similar codes to demonstrate that the code represents its
environmental modeling, such as Practice E978.
mathematical foundation.
1.6 This standard does not purport to address all of the
3.1.2 boundary condition—a mathematical expression of a
safety problems, if any, associated with its use. It is the
state of the physical system that constrains the equations of the
responsibility of the user of this standard to establish appro-
mathematical model.
priate safety and health practices and determine the applica-
3.1.3 calibration (model application)—the process of refin-
bility of regulatory limitations prior to us
ing the model representation of the hydrogeologic framework,
1.7 This guide offers an organized collection of information
hydraulic properties, and boundary conditions to achieve a
or a series of options and does not recommend a specific
desired degree of correspondence between the model simula-
course of action. This document cannot replace education or
tion and observations of the groundwater flow system.
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 service@astm.org. For Annual Book of ASTM
Vadose Zone Investigations. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Aug. 1, 2010. Published September 2010. Originally the ASTM website.
approved in 1993. Discontinued in 2002 and reinstated in 2004 as D5447–04. Last The last approved version of this historical standard is referenced on
previous edition approved in 2004 as D5447–04. DOI: 10.1520/D5447-04(2010). www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5447−04 (2010)
3.1.4 computer code (computer program)—the assembly of 5.1.1 Assist in problem evaluation,
numerical techniques, bookkeeping, and control language that
5.1.2 Design remedial measures,
represents the model from acceptance of input data and
5.1.3 Conceptualize and study groundwater flow processes,
instructions to delivery of output.
5.1.4 Provide additional information for decision making,
3.1.5 conceptual model—an interpretation or working de-
and
scription of the characteristics and dynamics of the physical
5.1.5 Recognize limitations in data and guide collection of
system.
new data.
3.1.6 groundwater flow model—application of a mathemati-
5.2 Groundwater models are routinely employed in making
cal model to represent a site-specific groundwater flow system.
environmental resource management decisions. The model
3.1.7 mathematical model—mathematical equations ex-
supportingthesedecisionsmustbescientificallydefensibleand
pressing the physical system and including simplifying as-
decision-makers must be informed of the degree of uncertainty
sumptions. The representation of a physical system by math-
in the model predictions. This has prompted some state
ematical expressions from which the behavior of the system
agencies to develop standards for groundwater modeling (2).
can be deduced with known accuracy.
This guide provides a consistent framework within which to
develop, apply, and document a groundwater flow model.
3.1.8 model—an assembly of concepts in the form of
mathematical equations that portray understanding of a natural
5.3 This guide presents steps ideally followed whenever a
phenomenon.
groundwater flow model is applied. The groundwater flow
3.1.9 sensitivity (model application)—the degree to which
model will be based upon a mathematical model that may use
the model result is affected by changes in a selected model
numerical, analytical, or any other appropriate technique.
input representing hydrogeologic framework, hydraulic
5.4 This guide should be used by practicing groundwater
properties, and boundary conditions.
modelers and by those wishing to provide consistency in
3.2 For definitions of other terms used in this guide, see
modeling efforts performed under their direction.
Terminology D653.
5.5 Use of this guide to develop and document a ground-
4. Summary of Guide
water flow model does not guarantee that the model is valid.
This guide simply outlines the necessary steps to follow in the
4.1 The application of a groundwater flow model ideally
modeling process. For example, development of an equivalent
would follow several basic steps to achieve an acceptable
porous media model in karst terrain may not be valid if
representation of the physical hydrogeologic system and to
significant groundwater flow takes place in fractures and
document the results of the model study to the end-user,
solution channels. In this case, the modeler could follow all
decision-maker, or regulator. These primary steps include the
steps in this guide and not end up with a defensible model.
following:
4.1.1 Define study objectives,
6. Procedure
4.1.2 Develop a conceptual model,
4.1.3 Select a computer code,
6.1 The procedure for applying a groundwater model in-
4.1.4 Construct a groundwater flow model,
cludes the following steps: define study objectives, develop a
4.1.5 Calibrate model and perform sensitivity analysis,
conceptual model, select a computer code or algorithm, con-
4.1.6 Make predictive simulations,
struct a groundwater flow model, calibrate the model and
4.1.7 Document modeling study, and
perform sensitivity analysis, make predictive simulations,
4.1.8 Perform postaudit.
document the modeling process, and perform a postaudit.
4.2 These steps are designed to ascertain and document an These steps are generally followed in order, however, there is
substantial overlap between steps, and previous steps are often
understanding of a system, the transition from conceptual
revisited as new concepts are explored or as new data are
model to mathematical model, and the degree of uncertainty in
obtained.Theiterativemodelingapproachmayalsorequirethe
the model predictions.The steps presented in this guide should
reconceptualization of the problem. An example of these
generally be followed in the order they appear in the guide;
feedback loops is shown in Fig. 1. These basic modeling steps
however, there is often significant iteration between steps. All
are discussed below.
steps outlined in this guide are required for a model that
simulates measured field conditions. In cases where the model
6.2 Definition of the study objectives is an important step in
is only used to understand a problem conceptually, not all steps
applying a groundwater flow model. The objectives aid in
are necessary. For example, if no site-specific data are
determining the level of detail and accuracy required in the
available, the calibration step would be omitted.
model simulation. Complete and detailed objectives would
ideally be specified prior to any modeling activities.
5. Significance and Use
6.3 A conceptual model of a groundwater flow and hydro-
5.1 According to the National Research Council (1), model
applications are useful tools to: logic 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
The boldface numbers in parentheses refer to the list of references at the end of
this standard. site and regional hydrogeologic and hydrologic data into a set
D5447−04 (2010)
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 must 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
mustaddresstheseissues.Hydrologicframework alsoincludes
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 direc-
tion 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-
ties 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
FIG. 1 Flow Chart of the Modeling Process
laboratory measurements of these properties in the conceptual
modeltosetboundsoracceptablerangesforguidingthemodel
calibration.
6.3.1.4 Sources and sinks of water to the aquifer system
of assumptions and concepts that can be evaluated quantita-
impact the pattern of groundwater flow. The most common
tively. Development of the conceptual model requires the
examples of sources and sinks include pumping or injection
collection and analysis of hydrogeologic and hydrologic data
wells, infiltration, evapotranspiration, drains, leakage across
pertinent to the aquifer system under investigation. Standard
confining layers and flow to or from surface water bodies.
guides and practices exist that describe methods for obtaining
Identify and describe sources and sinks within the aquifer
hydrogeologic and hydrologic data.
system in the conceptual model. The description includes the
6.3.1 The conceptual model identifies and describes impor-
rates and the temporal variability of the sources and sinks. A
tant aspects of the physical hydrogeologic system, including:
water budget should be developed as part of the conceptual
geologic and hydrologic framework, media type (for example,
model.
fractured or porous), physical and chemical processes, hydrau-
6.3.2 Provide an analysis of data deficiencies and potential
lic properties, and sources and sinks (water budget). These
sources of error with the conceptual model. The conceptual
components of the conceptual model may be described either
model usually contains areas of uncertainty due to the lack of
in a separate document or as a chapter within the model report.
field data. Identify these areas and their significance to the
Include illustrations, where appropriate, to support the
conceptual model evaluated with respect to project objectives.
narrative, for example, contour maps, cross sections, or block
In cases where the system may be conceptualized in more than
diagrams, or combination thereof. Each aspect of the concep-
one way, these alternative conceptual models should be de-
tual model is described as follows:
scribed and evaluated.
6.3.1.1 Geologic framework is the distribution and configu-
6.4 Computer code selection is the process of choosing the
raton of aquifer and confining units. Of primary interest are the
appropriate software algorithm, or other analysis technique,
thickness, continuity, lithology, and geologic structure of those
capable of simulating the characteristics of the physical hydro-
units that are relevant to the purpose of the study. The aquifer
geologic system, as identified in the conceptual model. The
system domai
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