1、Designation: D5447 04 (2010)Standard Guide forApplication of a Ground-Water Flow Model to a Site-SpecificProblem1This 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 of
2、 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. Scope1.1 This guide covers the application and subsequent docu-mentation of a groundwater flow model to a particular site orpr
3、oblem. 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 that h
4、as 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, isother-mal, groundwater flow models. The concepts are applicable toa wide range of models designed to
5、simulate subsurfaceprocesses, such as variably saturated flow, flow in fracturedmedia, density-dependent flow, solute transport, and mul-tiphase 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. Eachg
6、roundwater 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 have been prepared on
7、environmental modeling, such as Practice E978.1.6 This standard does not purport to address all of thesafety problems, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regul
8、atory limitations prior to us1.7 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 of this
9、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 word “Stan
10、dard” in the title of thisdocument means only that the document has been approvedthrough the ASTM consensus process.2. Referenced Documents2.1 ASTM Standards:2D653 Terminology Relating to Soil, Rock, and ContainedFluidsE978 Practice for Evaluating Mathematical Models for theEnvironmental Fate of Che
11、micals33. Terminology3.1 Definitions:3.1.1 application verificationusing the set of parametervalues and boundary conditions from a calibrated model toapproximate acceptably a second set of field data measuredunder similar hydrologic conditions.3.1.1.1 DiscussionApplication verification is to be dist
12、in-guished from code verification, that refers to software testing,comparison with analytical solutions, and comparison withother similar codes to demonstrate that the code represents itsmathematical foundation.3.1.2 boundary conditiona mathematical expression of astate of the physical system that c
13、onstrains the equations of themathematical model.3.1.3 calibration (model application)the process of refin-ing the model representation of the hydrogeologic framework,hydraulic properties, and boundary conditions to achieve a1This guide is under the jurisdiction ofASTM Committee D18 on Soil and Rock
14、and is the direct responsibility of Subcommittee D18.21 on Ground Water andVadose Zone Investigations.Current edition approved Aug. 1, 2010. Published September 2010. Originallyapproved in 1993. Discontinued in 2002 and reinstated in 2004 as D544704. Lastprevious edition approved in 2004 as D544704.
15、 DOI: 10.1520/D5447-04(2010).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn. The last approved ve
16、rsion of this historical standard is referencedon www.astm.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.desired degree of correspondence between the model simula-tion and observations of the groundwater flow system.3.1.4 compu
17、ter code (computer program)the assembly ofnumerical techniques, bookkeeping, and control language thatrepresents the model from acceptance of input data andinstructions to delivery of output.3.1.5 conceptual modelan interpretation or working de-scription of the characteristics and dynamics of the ph
18、ysicalsystem.3.1.6 groundwater flow modelapplication of a mathemati-cal model to represent a site-specific groundwater flow system.3.1.7 mathematical modelmathematical equations ex-pressing the physical system and including simplifying as-sumptions. The representation of a physical system by math-em
19、atical expressions from which the behavior of the systemcan be deduced with known accuracy.3.1.8 modelan assembly of concepts in the form ofmathematical equations that portray understanding of a naturalphenomenon.3.1.9 sensitivity (model application)the degree to whichthe model result is affected by
20、 changes in a selected modelinput representing hydrogeologic framework, hydraulic prop-erties, and boundary conditions.3.2 For definitions of other terms used in this guide, seeTerminology D653.4. Summary of Guide4.1 The application of a groundwater flow model ideallywould follow several basic steps
21、 to achieve an acceptablerepresentation of the physical hydrogeologic system and 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 cod
22、e,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, and4.1.8 Perform postaudit.4.2 These steps are designed to ascertain and document anunderstanding of a system, the transition from concep
23、tualmodel to mathematical model, and the degree of uncertainty inthe model predictions. 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. Allsteps outlined in this guide are required for a
24、model thatsimulates measured field conditions. In cases where the modelis only used to understand a problem conceptually, not all stepsare necessary. For example, if no site-specific data are avail-able, the calibration step would be omitted.5. Significance and Use5.1 According to the National Resea
25、rch Council (1),4modelapplications 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,and5.1.5 Recognize limitations in data and guide collection ofnew
26、 data.5.2 Groundwater models are routinely employed in makingenvironmental resource management decisions. The modelsupporting these decisions must be scientifically defensible anddecision-makers must be informed of the degree of uncertaintyin the model predictions. This has prompted some stateagenci
27、es to develop standards for groundwater modeling (2).This guide provides a consistent framework within which todevelop, apply, 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 upo
28、n a mathematical model that may usenumerical, analytical, or any other appropriate technique.5.4 This guide should be used by practicing 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
29、ground-water flow model does not guarantee that the model is valid.This guide simply outlines the necessary steps to follow in themodeling process. For example, development of an equivalentporous media model in karst terrain may not be valid ifsignificant groundwater flow takes place in fractures an
30、dsolution channels. In this case, the modeler could follow allsteps in this guide and not end up with a defensible model.6. Procedure6.1 The procedure for applying a groundwater model in-cludes the following steps: define study objectives, develop aconceptual model, select a computer code or algorit
31、hm, con-struct a groundwater flow model, calibrate the model andperform sensitivity analysis, make predictive simulations,document the modeling process, and perform a postaudit.These steps are generally followed in order, however, there issubstantial overlap between steps, and previous steps are oft
32、enrevisited as new concepts are explored or as new data areobtained. The iterative modeling approach may also require thereconceptualization 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 a
33、n important step inapplying a groundwater flow model. The objectives aid indetermining the level of detail and accuracy required in themodel simulation. Complete and detailed objectives wouldideally be specified prior to any modeling activities.6.3 A conceptual model of a groundwater flow and hydro-
34、logic system is an interpretation 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 quanti
35、ta-tively. Development of the conceptual model requires thecollection and analysis of hydrogeologic and hydrologic datapertinent to the aquifer system under investigation. Standard4The boldface numbers in parentheses refer to the list of references at the end ofthis standard.D5447 04 (2010)2guides a
36、nd practices exist that describe methods for obtaininghydrogeologic and hydrologic data.6.3.1 The conceptual model identifies and describes impor-tant aspects of the physical hydrogeologic system, including:geologic and hydrologic framework, media type (for example,fractured or porous), physical and
37、 chemical processes, hydrau-lic properties, and sources and sinks (water budget). Thesecomponents of the conceptual model may be described eitherin a separate document or as a chapter within the model report.Include illustrations, where appropriate, to support the narra-tive, for example, contour ma
38、ps, cross sections, or blockdiagrams, or combination thereof. Each aspect of the concep-tual model is described as follows:6.3.1.1 Geologic framework is the distribution and configu-raton of aquifer and confining units. Of primary interest are thethickness, continuity, lithology, and geologic struct
39、ure of thoseunits that are relevant to the purpose of the study. The aquifersystem domain, that may be composed of interconnectedaquifers and confining units, often extends beyond the domainof interest. In this case, describe the aquifer system in detailwithin the domain of interest and at least in
40、general elsewhere.Analysis of the geologic framework results in listings, tabula-tions, 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 modelincludes the physical extents of the aquife
41、r system, hydrologicfeatures that impact or control the groundwater flow system,analysis of groundwater flow directions, and media type. Theconceptual model must address the degree to which the aquifersystem behaves as a porous media. If the aquifer system issignificantly fractured or solutioned, th
42、e conceptual modelmust address these issues. Hydrologic framework also includesflow system boundaries that may not be physical and canchange with time, such as groundwater divides. Fluid potential(head) measurements allow assessment of the rate and direc-tion of groundwater flow. In addition, the ma
43、thematical modelis typically calibrated against these values (see 6.5). Waterlevel measurements within the groundwater system are tabu-lated, both spatially and temporally. This analysis of the flowsystem includes the assessment of vertical and horizontalgradients, delineation of groundwater divides
44、, and mapping offlow lines.6.3.1.3 Hydraulic properties include the transmissive andstorage characteristics of the aquifer system. Specific examplesof hydraulic properties include transmissivity, hydraulic con-ductivity, storativity, and specific yield. Hydraulic propertiesmay be homogeneous or hete
45、rogeneous throughout the modeldomain. Certain properties, such as hydraulic conductivity,may also have directionality, that is, the property may beanisotropic. It is important to document field and laboratorymeasurements of these properties in the conceptual model toset bounds or acceptable ranges f
46、or guiding the model calibra-tion.6.3.1.4 Sources and sinks of water to the aquifer systemimpact the pattern of groundwater flow. The most commonexamples of sources and sinks include pumping or injectionwells, infiltration, evapotranspiration, drains, leakage acrossconfining layers and flow to or fr
47、om surface water bodies.Identify and describe sources and sinks within the aquifersystem in the conceptual model. The description includes therates 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 dat
48、a 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 ma
49、y be conceptualized in more thanone way, these alternative conceptual models should be de-scribed and evaluated.6.4 Computer code selection is the process of choosing theappropriate software algorithm, or other analysis technique,capable of simulating the characteristics of the physical hydro-geologic system, as identified in the conceptual model. Thecomputer code must also be tested for the intended use and bewell documented (3-5).6.4.1 Other factors may also be considered in the decision-making process, such as model analysts experience and thosedescribed below for mod
