1、Designation: D5447 17Standard Guide forApplication of a Numerical Groundwater Flow Model to aSite-Specific Problem1This standard is issued under the fixed designation D5447; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This guide covers the application and subsequent docu-mentation of a groundwater flow model to a particular site o
3、rproblem. In this context, “groundwater flow model” refers tothe application of a mathematical model to the solution of asite-specific groundwater flow problem.1.2 This guide illustrates the major steps to take in devel-oping a groundwater flow model that reproduces or simulatesan aquifer system tha
4、t has been studied in the field. This guidedoes not identify particular computer codes, software, oralgorithms used in the modeling investigation.1.3 This guide is specifically written for saturated,isothermal, groundwater flow models. The concepts are appli-cable to a wide range of models designed
5、to simulate subsur-face processes, such as variably saturated flow, flow in frac-tured media, density-dependent flow, solute transport, andmultiphase transport phenomena; however, the details of theseother processes are not described in this guide.1.4 This guide is not intended to be all inclusive.
6、Eachgroundwater model is unique and may require additionalprocedures in its development and application. All such addi-tional analyses should be documented, however, in the modelreport.1.5 This guide is one of a series of standards on groundwa-ter model applications. Other standards include D5981, D
7、5490,D5609, D5610, D5611, and D6033.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of
8、 regulatory limitations prior to use.1.7 This guide offers an organized collection of informationor a series of options and does not recommend a specificcourse of action. This document cannot replace education orexperience and should be used in conjunction with professionaljudgment. Not all aspects
9、of this guide may be applicable in allcircumstances. This ASTM standard is not intended to repre-sent or replace the standard of care by which the adequacy ofa given professional service must be judged, nor should thisdocument be applied without consideration of a projects manyunique aspects. The wo
10、rd “Standard” in the title of thisdocument means only that the document has been approvedthrough the ASTM consensus process.1.8 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDev
11、elopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D653 Terminology Relating to Soil, Rock, and ContainedFluidsD5490 Guide for Comparing Groundwater Flow ModelSi
12、mulations to Site-Specific InformationD5609 Guide for Defining Boundary Conditions in Ground-water Flow ModelingD5610 Guide for Defining Initial Conditions in GroundwaterFlow ModelingD5611 Guide for Conducting a Sensitivity Analysis for aGroundwater Flow Model ApplicationD5981 Guide for Calibrating
13、a Groundwater Flow ModelApplication (Withdrawn 2017)3D6033 Guide for Describing the Functionality of a Ground-water Modeling Code3. Terminology3.1 Definitions:1This guide is under the jurisdiction ofASTM Committee D18 on Soil and Rockand is the direct responsibility of Subcommittee D18.21 on Groundw
14、ater andVadose Zone Investigations.Current edition approved Dec. 15, 2017. Published January 2018. Originallyapproved in 1993. Last previous edition approved in 2010 as D544704(2010).DOI: 10.1520/D5447-17.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer S
15、ervice at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.*A Summary of Changes section appears at the end of this standardCopyrig
16、ht ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of Internationa
17、l Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.1.1 For common definitions of technical terms used in thisstandard, refer to Terminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 boundary condition, nin
18、 hydrogeologic properties,amathematical expression that constrains the equations of themathematical model to account for the addition or removal offluid or solutes to or from the mathematical model.3.2.2 calibration (model application), nin hydrogeologicproperties, the process of refining the model
19、representation ofthe hydrogeologic framework, hydraulic properties, andboundary conditions to achieve a desired degree of correspon-dence between the model simulation and observations of thegroundwater flow system.3.2.3 groundwater flow model, nin hydrogeologicproperties, application of a mathematic
20、al model to represent asite-specific groundwater flow system.3.2.4 model, nin hydrogeologic properties, an assembly ofconcepts in the form of mathematical equations that portrayunderstanding of a natural phenomenon.3.2.5 sensitivity (model application), nin hydrogeologicproperties, the degree to whi
21、ch the model result is affected bychanges in a selected model input representing hydrogeologicframework, hydraulic properties, and boundary conditions.3.3 The following terms are contained in TerminologyD653, but are included here for the convenience of the user:3.3.1 conceptual model, nin hydrogeol
22、ogic properties,aninterpretation or working description of the characteristics anddynamics of the physical system.4. Summary of Guide4.1 The application of a groundwater flow model ideallywould follow several basic steps to achieve an acceptablerepresentation of the physical hydrogeologic system and
23、 todocument the results of the model study to the end-user,decision-maker, or regulator. These primary steps include thefollowing: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 sen
24、sitivity analysis,4.1.6 Make predictive simulations,4.1.7 Document modeling study, and4.1.8 Perform postaudit.4.2 These steps are designed to ascertain and document anunderstanding of a system, the transition from conceptualmodel to mathematical model, and the degree of uncertainty inthe model predi
25、ctions. The steps presented in this guide shouldgenerally be followed in the order they appear in the guide;however, there is often significant iteration between steps. Allof the steps outlined in this guide are required for a model thatsimulates measured field conditions. In cases where the modelis
26、 only used to understand a problem conceptually, some stepsare unnecessary. For example, if no site-specific data areavailable, the calibration step would be omitted.5. Significance and Use5.1 Model applications (1),4are useful tools to:5.1.1 Assist in problem evaluation,5.1.2 Design remedial measur
27、es,5.1.3 Conceptualize and study groundwater flow processes,5.1.4 Provide additional information for decision making,and5.1.5 Recognize limitations in data and guide collection ofnew data.5.2 Groundwater models are routinely employed in makingenvironmental resource management decisions. The modelsup
28、porting these decisions should be scientifically defensibleand decision-makers informed of the degree of uncertainty inthe model predictions. This has prompted some state agenciesto develop standards for groundwater modeling (2). This guideprovides a consistent framework within which to develop,appl
29、y, and document a groundwater flow model.5.3 This guide presents steps ideally followed whenever agroundwater flow model is applied. The groundwater flowmodel will be based upon a mathematical model that may usenumerical, analytical, or other appropriate technique.5.4 This guide should be used by pr
30、acticing groundwatermodelers and by those wishing to provide consistency inmodeling efforts performed under their direction.5.5 Use of this guide to develop and document a ground-water flow model does not guarantee that the model is valid.This guide simply outlines the necessary steps to follow in t
31、hemodeling process. For example, development of an equivalentporous media model in karst terrain may not be valid ifsignificant groundwater flow takes place in fractures andsolution channels. In this case, the modeler could follow thesteps in this guide and not end up with a defensible model.6. Proc
32、edure6.1 The procedure for applying a groundwater model in-cludes the following steps: define study objectives, develop aconceptual model, select a computer code or algorithm, con-struct a groundwater flow model, calibrate the model andperform sensitivity analysis, make predictive simulations,docume
33、nt the modeling process, and perform a post-audit.These steps are generally followed in order, however, there issubstantial overlap between steps, and previous steps are oftenrevisited as new concepts are explored or as new data areobtained. The iterative modeling approach may also require thereconc
34、eptualization of the problem. An example of thesefeedback loops is shown in Fig. 1. These basic modeling stepsare discussed below.6.2 Definition of the study objectives is an important step inapplying a groundwater flow model. The objectives aid indetermining the level of detail and accuracy needed
35、in themodel simulation. Complete and detailed objectives wouldideally be specified prior to modeling activities.4The boldface numbers in parentheses refer to the list of references at the end ofthis standard.D5447 1726.3 A conceptual model of a groundwater flow and hydro-logic system is an interpret
36、ation or working description of thecharacteristics and dynamics of the physical hydrogeologicsystem. The purpose of the conceptual model is to consolidatesite and regional hydrogeologic and hydrologic data into a setof assumptions and concepts that can be evaluated quantita-tively. Development of th
37、e conceptual model requires thecollection and analysis of hydrogeologic and hydrologic datapertinent to the aquifer system under investigation. Standardguides and practices exist that describe methods for obtaininghydrogeologic and hydrologic data.6.3.1 The conceptual model identifies and describes
38、impor-tant aspects of the physical hydrogeologic system, including:geologic and hydrologic framework, media type (for example,fractured or porous), physical and chemical processes, hydrau-lic properties, and sources and sinks (water budget). Thesecomponents of the conceptual model may be described e
39、itherin a separate document or as a chapter within the model report.Include illustrations, where appropriate, to support thenarrative, for example, contour maps, cross sections, or blockdiagrams, or combination thereof. Each aspect of the concep-tual model is described as follows:6.3.1.1 Geologic fr
40、amework is the distribution and configu-ration of aquifer and confining units. Of primary interest arethe thickness, continuity, lithology, and geologic structure ofthose units that are relevant to the purpose of the study. Theaquifer system domain, that may be composed of intercon-nected aquifers a
41、nd confining units, often extends beyond thedomain of interest. In this case, describe the aquifer system indetail within the domain of interest and at least in generalelsewhere. Analysis of the geologic framework results inlistings, tabulations, or maps, or combination thereof, of thethickness, ext
42、ent, and properties of each relevant aquifer andconfining unit.6.3.1.2 Hydrologic framework in the conceptual modelincludes the physical extents of the aquifer system, hydrologicfeatures that impact or control the groundwater flow system,analysis of groundwater flow directions, and media type. Theco
43、nceptual model should address the degree to which theaquifer system behaves as a porous media. If the aquifersystem is significantly fractured or solutioned, the conceptualmodel should address these issues. Hydrologic framework alsoincludes flow system boundaries that may not be physical andcan chan
44、ge with time, such as groundwater divides. Fluidpotential (head) measurements allow assessment of the rate anddirection of groundwater flow. In addition, the mathematicalmodel is typically calibrated against these values (see 6.5).Water level measurements within the groundwater system aretabulated,
45、both spatially and temporally. This analysis of theflow system includes the assessment of vertical and horizontalgradients, delineation of groundwater divides, and mapping offlow lines.6.3.1.3 Hydraulic properties include the transmissive andstorage characteristics of the aquifer system. Specific ex
46、amplesof hydraulic properties include transmissivity, hydraulicconductivity, storativity, and specific yield. Hydraulic proper-ties may be homogeneous or heterogeneous throughout themodel domain. Certain properties, such as hydraulicconductivity, may also have directionality, that is, the propertyma
47、y be anisotropic. It is important to document field andlaboratory measurements of these properties in the conceptualmodel to set bounds or acceptable ranges for guiding the modelcalibration.6.3.1.4 Sources and sinks of water to the aquifer systemimpact the pattern of groundwater flow. The most commo
48、nexamples of sources and sinks include pumping or injectionwells, infiltration, evapotranspiration, drains, leakage acrossconfining layers and flow to or from surface water bodies.Identify and describe sources and sinks within the aquifersystem in the conceptual model. The description includes thera
49、tes and the temporal variability of the sources and sinks. Awater budget should be developed as part of the conceptualmodel.6.3.2 Provide an analysis of data deficiencies and potentialsources of error with the conceptual model. The conceptualmodel usually contains areas of uncertainty due to the lack offield data. Identify these areas and their significance to theconceptual model evaluated with respect to project objectives.In cases where the system may be conceptualized in more thanone way, these alternative conceptual models should be de-scribed and evaluated.6.4 C
