modflow-related freeware and shareware resources on the internet

6
MODFLOW-related freeware and shareware resources on the internet Richard B. Winston * 2145 Colts Neck Cl., Reston, VA 20191, USA Received 16 April 1998; received in revised form 10 June 1998; accepted 10 June 1998 Abstract MODFLOW (modular finite-dierence groundwater flow model), probably the most frequently used groundwater modeling program, is in the public domain and may be downloaded from the US Geological Survey (USGS) and other sites. In addition, freeware and shareware pre- and postprocessors are also available. Some of the original documentation can also be downloaded for free. A variety of other free or low-cost materials related to MODFLOW are also available. # 1999 Elsevier Science Ltd. All rights reserved. Keywords: Groundwater; Finite dierences 1. Introduction The modular finite-dierence groundwater flow model, frequently referred to as MODFLOW; (McDonald and Harbaugh, 1988; Harbaugh and McDonald, 1996a,b) is a program for simulating con- fined or unconfined, saturated flow in one, two, or three dimensions. It allows both steady-state and tran- sient simulations. At least with the public domain packages, it does not simulate unsaturated flow or solute and heat transport. However, MT3D (Zheng, 1990) and MOC3D (Konikow et al., 1996), both of which rely on MODFLOW, can simulate solute trans- port. MODFLOW is one of the most popular ground- water modeling programs in existence. In a compara- tively recent survey (Geragthty and Miller Software Newsletter, 1992), it was, by far, the most popular groundwater modeling program. Some reasons for this popularity may be: (1) the program is applicable to most types of groundwater modeling problems, (2) the original packages in the program are well structured and documented, (3) the source code is in the public domain and thus can be checked for errors and modi- fied by anyone with the necessary mathematical and programming skills, (4) the program is accepted by regulatory agencies and in litigation and (5) ongoing modifications of the program continue to increase its capabilities. Public domain and proprietary packages have been written for MODFLOW both within the US Geological Survey (USGS) where it was originally cre- ated and outside the USGS (Tables 1 and 2). Since MODFLOW was written, a variety of public-domain and proprietary programs have built upon it either by using the output of MODFLOW as the input for ad- ditional modeling or by extending the capabilities of MODFLOW. The public-domain programs that build upon MODFLOW include MT3D (Zheng, 1990), MODFLOWP (Hill, 1992, 1994) and MOC3D (Konikow et al., 1996). Before using any of the packages not currently sup- ported by the USGS, users should carefully read the documentation to ensure that the code has been thoroughly tested. If it has not been thoroughly tested, you should test it yourself before relying on it. Both MODFLOW itself and a variety of related programs are freely available on the Internet. The most prominent source is the USGS itself (http:// Computers & Geosciences 25 (1999) 377–382 0098-3004/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S0098-3004(98)00141-1 PERGAMON * E-mail: [email protected]; http://www.mind- spring.com/ 0rbwinston/

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MODFLOW-related freeware and shareware resources onthe internet

Richard B. Winston *

2145 Colts Neck Cl., Reston, VA 20191, USA

Received 16 April 1998; received in revised form 10 June 1998; accepted 10 June 1998

Abstract

MODFLOW (modular ®nite-di�erence groundwater ¯ow model), probably the most frequently used groundwater

modeling program, is in the public domain and may be downloaded from the US Geological Survey (USGS) andother sites. In addition, freeware and shareware pre- and postprocessors are also available. Some of the originaldocumentation can also be downloaded for free. A variety of other free or low-cost materials related toMODFLOW are also available. # 1999 Elsevier Science Ltd. All rights reserved.

Keywords: Groundwater; Finite di�erences

1. Introduction

The modular ®nite-di�erence groundwater ¯ow

model, frequently referred to as MODFLOW;

(McDonald and Harbaugh, 1988; Harbaugh and

McDonald, 1996a,b) is a program for simulating con-®ned or uncon®ned, saturated ¯ow in one, two, or

three dimensions. It allows both steady-state and tran-

sient simulations. At least with the public domain

packages, it does not simulate unsaturated ¯ow or

solute and heat transport. However, MT3D (Zheng,

1990) and MOC3D (Konikow et al., 1996), both of

which rely on MODFLOW, can simulate solute trans-

port.

MODFLOW is one of the most popular ground-

water modeling programs in existence. In a compara-

tively recent survey (Geragthty and Miller Software

Newsletter, 1992), it was, by far, the most popular

groundwater modeling program. Some reasons for this

popularity may be: (1) the program is applicable to

most types of groundwater modeling problems, (2) the

original packages in the program are well structured

and documented, (3) the source code is in the publicdomain and thus can be checked for errors and modi-

®ed by anyone with the necessary mathematical and

programming skills, (4) the program is accepted by

regulatory agencies and in litigation and (5) ongoingmodi®cations of the program continue to increase its

capabilities. Public domain and proprietary packages

have been written for MODFLOW both within the US

Geological Survey (USGS) where it was originally cre-

ated and outside the USGS (Tables 1 and 2). SinceMODFLOW was written, a variety of public-domain

and proprietary programs have built upon it either by

using the output of MODFLOW as the input for ad-

ditional modeling or by extending the capabilities of

MODFLOW. The public-domain programs that buildupon MODFLOW include MT3D (Zheng, 1990),

MODFLOWP (Hill, 1992, 1994) and MOC3D

(Konikow et al., 1996).

Before using any of the packages not currently sup-

ported by the USGS, users should carefully read the

documentation to ensure that the code has been

thoroughly tested. If it has not been thoroughly tested,you should test it yourself before relying on it.

Both MODFLOW itself and a variety of relatedprograms are freely available on the Internet. The

most prominent source is the USGS itself (http://

Computers & Geosciences 25 (1999) 377±382

0098-3004/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved.

PII: S0098-3004(98 )00141-1

PERGAMON

* E-mail: [email protected]; http://www.mind-

spring.com/0rbwinston/

Table

1

Publicdomain

packages

forMODFLOW

notin

originalversionofMODFLOW

Abbreviation

Packagename

Purpose

Reference

Sources

(see

Table

2)

PCG1

Preconditioned

Conjugate-GradientPackage1

usedto

solve®nite-di�erence

equations

Kuiper

(1987)

2,3

BCF2

Block-C

enteredFlow

2allowsdry

cellsto

becomewet

McD

onald

andHarbaugh(1992)

1,2,3

RIV

2River

Package2

usedforroutingriver

¯ow

downstream

from

one

river

reach

toanother

Miller(1988)

2

STR1

Stream¯ow-RoutingPackage

usedto

simulate

stream¯ow

routing

Prudic

(1989)

1,2,3

RIN

T1

River

InteractionsPackage

simulate

stream¯ow

routingandriver

interaction

withalluvialdeposits

SchenkandPoeter

(1990)

5

PCG2

Preconditioned

Conjugate-GradientPackage2

usedto

solve®nitedi�erence

equations

Hill(1990)

1,2,3

IBS1

Interbed

StoragePackage1

allowssimulationofwaterrelease

byinterbeds

LeakeandPrudic

(1991)

1,2

CHD1

Tim

e-VariantSpeci®ed-H

eadPackage1

usedforspeci®ed

headsthatvary

withtime

LeakeandPrudic

(1991)

1,2

BCF3

Block-C

enteredFlow

3allowsmore

accurate

simulations

GoodeandAppel

(1992)

1,2,3

GFD1

GeneralizedFinite-Di�erence

1allowsdirectspeci®cationofallintercell

conductances

Harbaugh(1992)

1,2

LAK1

LakePackage1

usedto

simulate

lakes

ChengandAnderson(1993)

6

none

Modi®ed

Stream

Package

usedto

simulate

stream¯ow

routingincluding

streamsthat¯ow

into

oroutoflakes

ChengandAnderson(1993)

6

HFB1

Horizontal-Flow

BarrierPackage1

simulatesthee�

ects

ofthin

verticalbarriers

to

horizontal¯ow

such

asintrusionsorfaults

Hsieh

andFreckleton(1993)

1,2,3

SHY1

HydrographPackage

saves

hydrographdata

forspeci®ed

cells

Plato

(1993)

7

BAR

andCUT

Flow-Barrier1andCanyon-C

utter

Packages

1together,thesepackages

simulate

pinchouts

andthe

e�ects

ofthin

verticalbarriers

tohorizontal¯ow

such

asintrusions,faultsorcanyons

Hansen(1993)

2

Hansen(1993)

TLK1

TransientLeakagePackage1

simulatesleakagefrom

con®ninglayersin

transient

quasi-three-dim

ensionalmodels

Leakeet

al.(1994)

1,2

DE45

Direct-SolutionPackage5

usedto

solve®nitedi�erence

equations

Harbaugh(1995)

1,2

RES1

ReservoirPackage1

usedto

simulate

¯ow

into

andoutofreservoirs

Fenskeet

al.(1996)

1,2

none

Spatialvariable

anisotropypackage

allowsspatiallyvariable

anisotropy

KladiasandRuskau�(1997)

4

FHB1

Flow

andHeadBoundary

Package1

usedfortransientspeci®ed

headandspeci®ed

¯ux

boundaries

LeakeandLilly

(1997)

1,2

R.B. Winston / Computers & Geosciences 25 (1999) 377±382378

water.usgs.gov/software/mod¯ow.htm1 or http://www.geogr.unijena.de/software/mod¯ow.html). How-

ever, a variety of other sites exist that have either thesource code or executable versions of MODFLOW(Table 3). In some instances the non-USGS versions

have extra capabilities that the USGS version lacks.

2. Preprocessors

Although MODFLOW is a powerful program, itcan hardly be described as user-friendly. All input for

the program is in the form of large text ®les thatdescribe the grid structure, hydraulic properties,boundary conditions and transient data. These ®les

must follow a strict format. If the format requirementsare violated MODFLOW will either not be able to runor will produce incorrect results. To alleviate this pro-

blem, a large number of preprocessors have beendeveloped that provide a graphical user interface forMODFLOW. In some cases, the programs are either

freeware or shareware.One shareware preprocessor is MODUSER which can

be obtained from the Computer Oriented GeologicalSociety ftp site among other places. (ftp://ftp.csn.org/

COGS/Hydrology/moduser.zip or http://sunsitc.un-c.edu/pub/academic/geology/COGS/Hydrology/). It is a

DOS program and has a US$10.00 registration fee. Itsupports the original MODFLOW-88 packages. It can

be used to set up a grid and assign values to cells byclicking on the cells. In a brief test of MODUSER, it was

not clear how to reenter data in order to correct mistakes.There is little documentation of the program making it

di�cult to use.UNCERT (http://uncert.mines.edu/, Wingle et al.,

1995; Wingle, 1997) is a free MODFLOW preproces-sor for Unix. It is reputed to do more than just act as

a MODFLOW preprocessor.MFI (http://water.usgs.gov/software/m®.html;

Harbaugh, 1994) is free. It supports MODFLOW-96,the stream package and MOC-3D. To use the DOS

version a spreadsheet program that can read and writeLotus 123.WK1 ®les is required, such as Microsoft

Excel. MFI requires a bit more work to install prop-erly than do most modern programs. After download-

ing and extracting the program, the Con®g.sys ®lemust be modi®ed and a batch ®le run. Every timeMFI is run, a batch ®le must be copied into the direc-

tory where MFI is installed. This batch ®le controlsthe interaction between MFI and the speadsheet pro-

Table 2

Sources for MODFLOW Packages

Reference

number Web page or email address or mailing address of MODFLOW package

1 http://water.usgs.gov/software/ground_water.html

2 http://water.usgs.gov/software/to_order.html

3 FTP://kilburn.keene.edu/Kilburn/ftp/GWM-L/

4 ftp://ftp.mindspring.com/users/rbwinston/incoming/varan3.zip

5 [email protected] (Judith A. Schenk) or [email protected] (Eileen Poeter)

6 [email protected] or [email protected] (Mary Anderson)

7 Arizona Department of Water Resources, Hydrology Division, Modeling Section, 15 S 15th Ave., Phoenix, AZ

85007, or Paul R. Plato, Harding Lawson Associates, 2800 N. 44th St. Ste. 500, Phoenix, AZ 85008

Table 3

Non USGS sources for free versions of MODFLOW

URL Added features

http://www.argusint.com/Mod¯ow.html or http://www.mindspring.com/

0rbwinston/ModDyn.htm

dynamic arrays, additional packages, link to MT3D

http://hydro.geo.ua.edu/mt3d/mt3d150d.htm link to MT3D, additional options for reading data

http://www.¯owpath.com/ additional packages

http://dino.wiz.uni-kassel.de/model_db/server.html no extra features

http://ourworld.compuserve.com/homepages/W_H_Chiang/ link to MT3D

FTP://kilburn.keene.edu/Kilburn/ftp/GWM-L/ no extra features

http://www.epa.gov/ada/models.html link to MT3D, additional options for reading data

(compiled version may not work on modern PCs)

R.B. Winston / Computers & Geosciences 25 (1999) 377±382 379

gram. MFI deletes this ®le when it exits, so it cannotbe left in the directory with MFI. MFI appears to be

an e�ective program for creating MODFLOW input®les. It is much less user-friendly than commercial pre-processors. The manual is available online at: http://

h2o.usgs.gov/software/m®_manual/ofr-94_468_1.html.The USGS also provides another free user interface

for MODFLOW. The `MODFLOW-GUI' (http://

water.usgs.gov/software/mod¯ow-gui.html, Shapiro etal., 1997) is a plug-in for Argus open numerical en-vironments (Argus ONE). Thus to use it, you must

have Argus ONE. I have written an updated version ofthe plug-in that supports MT3D in addition toMODFLOW. It is available for free from the ArgusWeb site (http://www.argusint.co). In theory some

other program besides Argus ONE might be adaptedto use either USGS or my version of the MODFLOWplug-in. However, this would probably be impractical.

The MODFLOW-GUI is more sophisticated thanMODUSER or MFI because the data de®ning themodel are independent of the grid. Thus, the grid can

be altered without requiring the user to reenter data.The MODFLOW-GUI also provides postprocessing ofMOFLOW data.

For users of Arc-Info, there is a public domain pro-gram (MODFLOWARC, Orzol and McGrath, 1992)that can be used to link Arc-Info to MODFLOW. It isa Unix program. The source code and documentation

are available from http://wwworegon.wr.usgs.gov/projs_dir/mod¯owarc/mod¯owarc.html.The USGS provides one additional preprocessor:

RADMOD (http://water.usgs.gov/software/rad-mod.html, Reilly and Harbaugh, 1993a,b). It is aspecial purpose tool that can be used to prepare

radially symmetrical models using the General-FiniteDi�erence Package. It only prepares the input ®le forthe General-Finite Di�erence Package and not theremaining MODFLOW packages.

3. Postprocessors

The USGS provides several programs for processingand display of the data from MODFLOW and relatedprograms

CONTOUR (http://water.usgs.gov/software/con-tour.html, Harbaugh, 1990a) is a Unix program forcreating contour maps from gridded data. I have

not tested it.MODPATH (Pollock, 1994) is a particle tracking

program for MODFLOW models. The USGS has

compiled versions for Unix at http://water.usgs.gov/software/modpath.html. I compiled a free versionfor DOS. At present, I do not have the disk space

on my server to keep it on line so you must contactme to get it.

ZONEBUDGET (http://water.usgs.gov/software/zonebdgt.html, Harbaugh, 1990b) is used to createwater budgets for particular zones in a

MODFLOW model. Versions for DOS and Unixare available from the USGS. It is easy to use ande�ective.

I have written a freeware program MF2Hydrograph(http://www.mindspring.com/0rbwinston/mf2hy-drogrgph.htm) that will extract hydrograph data for

individual cells from the formatted head and draw-down ®les created by MODFLOW-96.

4. Documentation

MODFLOW and related programs are exhaustivelydocumented in USGS publications which may be pur-

chased at nominal fees. Documentation for some ofthe newer packages can be downloaded from theUSGS MODFLOW page (http://water.usgs.gov/soft-ware/mod¯ow96.html) as Postscript or pdf ®les. These

documents provide the theoretical basis for the pro-grams, detailed explanations of the source code, inputformats and example applications. This documentation

is a critical reason for the success of MODFLOW,because is detailed enough to allow users to add ad-ditional packages to the program: something which

can be said of no other USGS groundwater modelingprogram. The documentation may, however, seemoverwhelming for beginners. The original documen-

tation (McDonald and Harbaugh, 1988) is 586 pageslong and represents about one third of the total docu-mentation now available. To provide a more succinctguide to MODFLOW, I have written a `Help File' for

it, comprising a series of linked Web pages that explainhow to use each of the packages. There is also a shorttutorial on MODFLOW and a Web page with links to

all the free and commercial versions of MODFLOWor MODFLOW-related programs (of which I amaware) on the Internet. The guide may be used on a

trial basis for up to 30 days after which users arerequired to pay a small registration fee. The guide maybe obtained from http://www.mindspring.com/0rbwinston/modhelp.htm.

Another useful resource for beginners is the manualof MODFLOW instructional problems from theEnvironmental Protection Agency (Andersen, 1993,

http://www.epa.gov/ada/mod¯mn.html). It gives 20examples of simple MODFLOW models each designedto illustrate how to use speci®c aspects of

MODFLOW. It is an excellent source of informationon how best to use MODFLOW and to avoid com-mon errors.

R.B. Winston / Computers & Geosciences 25 (1999) 377±382380

Environmental Simulations, Inc. (http://www.groundwatermodels.com/) has converted the

MODFLOW documentation to a pair of WindowsHelp Files. Strictly, these ®les are not sharewarebecause they cost US$25.00. These help ®les are

included with their preprocessor Groundwater Vistas,but may also be purchased separately.

5. Summary

MODFLOW is popular as a groundwater modelingprogram. This popularity stems from its power, and

excellent documentation, among othe factors. Not onlymay MODFLOW be obtained free from the USGS,but enhanced versions are also available from a varietyof other sites. Free, and low-cost, MODFLOW pre-

and postprocessors are available, as well as a numberof public domain models that use MODFLOW andprovide additional modeling capabilities. A variety of

free or low-cost documentation is also available.

References

Andersen, P.F., 1993. A manual of instructional problems for

the USGS MODFLOW model. Robert S. Kerr

Environmental Research Laboratory, O�ce of Research

and Development, US Environmental Protection Agency,

Ada, OK, EPA/600/R-93/010, 252 pp.

Cheng, X., Anderson, M.P., 1993. Numerical simulation of

groundwater interaction with lakes allowing for ¯uctuating

lake levels. Ground Water 31 (6), 020±933.

Fenske, J.P., Leake, S.A., Prudic, D.E., 1996. Documentation

of a computer program (RES1) to simulate leakage from

reservoirs using the modular ®nite-di�erence groundwater

¯ow model (MODFLOW). US Geological Survey Open-

File Report 96-364, 51 pp.

Geragthty and Miller Software Newsletter, 1992. Geragthty

and Miller survey results 4(summer), pp. 1±2.

Goode, D.J., Appel, C.A., 1992. Finite-di�erence interblock

transmissivity for uncon®ned aquifers and for aquifers hav-

ing smoothly varying transmissivity. US Geological Survey

Water Resources Investigations Report 92-4124, 79 pp.

Hansen, A.J., 1993. Modi®cations to the modular ®nite-di�er-

ence groundwater ¯ow model used for the Columbia Platea

region aquifer-system analysis, Washington, Oregon and

Idaho. US Geological Survey Open-File Report 91-532, 162

pp.

Harbaugh, A.W., 1990a. A simple contouring program for

gridded data. US Geological Survey Open-File Report 90-

144, 37 pp.

Harbaugh, A.W., 1990b. A computer program for calculating

subregional water budgets using results from the US

Geological Survey modular three-dimensional ®nite-di�er-

ence groundwater ¯ow model. US Geological Survey Open-

File Report 90-392, 46 pp.

Harbaugh, A.W., 1992. A generalized ®nite-di�erence formu-

lation for the US Geological Survey modular three-dimen-

sional ®nite-di�erence groundwater ¯ow model. US

Geological Survey Open-File Report 91-494, 60 pp.

Harbaugh, A.W., 1994. A data input program (MFI) for the

US Geological Survey modular ®nite-di�erence ground-

water ¯ow model. US Geological Survey Open-File Report

94-468, 24 pp.

Harbaugh, A.W., 1995. Direct solution package based on

alternating diagonal ordering for the US Geological Survey

modular three-dimensional ®nite-di�erence groundwater

¯ow model. US Geological Survey Open-File Report 95-

288, 46 pp.

Harbaugh, A.W., McDonald, M.G., 1996a. User's documen-

tation for MODFLOW-96: an update to the US Geological

Survey modular ®nite-di�erence groundwater ¯ow model.

US Geological Survey Open-File Report 96-485, 56 pp.

Harbaugh, A.W., McDonald, M.G., 1996b. Programmer's

documentation for MODFLOW-96: an update to the US

Geological Survey modular ®nite-di�erence groundwater

¯ow model. US Geological Survey Open-File Report 96-

486, 220 pp.

Hill, M.C., 1990. Preconditioned conjugate-gradient 2

(PCG2), a computer program for solving groundwater ¯ow

equations. US Geological Survey Water-Resources

Investigations Report 90-4048, 43 pp.

Hill, M.C., 1992. A computer program MODFLOWP for

estimating parameters of a transient, three-dimensional,

groundwater ¯ow model using nonlinear regression. US

Geological Survey Open-File Report 91-484.

Hill, M.C., 1994. Five computer programs for testing

weighted residuals and calculating linear con®dence and

prediction intervals on results from the groundwater par-

ameter-estimation computer program MODFLOWP. US

Geological Survey Open-File Report 93-481.

Hsieh, P.A. and Freckleton, J.R., 1993, Documentation of a

computer program to simulate horizontal-¯ow barriers

using the US Geological Survey modular three-dimensional-

®nite-di�erence groundwater ¯ow model. US Geological

Survey Open-File Report 92-477, 32 pp.

Kladias, M.P., Ruskau�, G.J., 1997. Implementing spatially

variable anisotropy in MODFLOW. Ground Water 35 (2),

368±370.

Konikow, L.F., Goode, D.J., Hornberger, G.Z., 1996. A

three-dimensional method-of-characteristics solute transport

model (MOC3D). US Geological Survey Water Resources

Investigations Report 96-4267, 87 pp.

Kuiper, L.K., 1987. Computer program for solving ground-

water ¯ow equations by the preconditioned conjugate gradi-

ent method. US Geological Survey Water Resources

Investigations Report 87-4091, 34 pp.

Leake, S.A., Leahy, P.P., Navoy, A.S., 1994. Documentation

of a computer program to simulate transient leakage from

con®ning units using the modular ®nite-di�erence ground-

water ¯ow model. US Geological Survey Open-File Report

94-59, 70 pp.

Leake, S.A., Lilly, M.R., 1997. Documentation of a computer

program FHB1 for assignment of transient speci®ed-¯ow

and speci®ed-head boundaries in applications of the modu-

lar ®nite-di�erence groundwater ¯ow model (MODFLOW).

US Geological Survey Open-File Report 97-571, 50 pp.

R.B. Winston / Computers & Geosciences 25 (1999) 377±382 381

Leake, S.A., Prudic, D.E., 1991. Documentation of a compu-

ter program to simulate aquifer-system compaction using

the modular ®nite-di�erence groundwater ¯ow model. US

Geological Survey Techniques of Water-Resources

Investigations, book 6, Chap. A2, 68 pp.

McDonald, M.G., Harbaugh, A.W., 1988. A modular three-

dimensional ®nite-di�erence groundwater ¯ow model. US

Geological Survey Techniques of Water-Resources

Investigations, book 6, Chap. A1, 586 pp.

McDonald, M.G., Harbaugh, A.W., Orr, B.R., Ackerman,

D.J., 1992, A method of converting no-¯ow cells to vari-

able-head cells for the US Geological Survey modular

®nite-di�erence groundwater ¯ow model. US Geological

Survey Open-File Report 91-536, 99 pp.

Miller, R.S., 1988. User's guide for Riv2: a package for rout-

ing and accounting of river discharge for a modular, three-

dimensional, ®nite-di�erence, groundwater ¯ow model. US

Geological Survey Open-File Report 88-345, 33 pp.

Orzol, L.L., McGrath, T.S., 1992. Modi®cations of the US

Geological Survey modular ®nite-di�erence groundwater

¯ow model to read and write Geographic Information

System ®les. US Geological Survey Open-File Report 92-

50, 202 pp.

Plato, P.R., 1993. Hydrograph package for MODFLOW.

Ground Water 31 (6), 1025±1028.

Pollock, D.W., 1994. User's guide for MODPATH/

MODPATH-PLOT, Version 3: a particle tracking postpro-

cessing package for MODFLOW, the US Geological

Survey ®nite-di�erence groundwater ¯ow model. US

Geological Survey Open-File Report 94-464, 6 ch.

Prudic, D.E., 1989. Documentation of a computer program to

simulate stream-aquifer relations using a modular, ®nite-

di�erence, groundwater ¯ow model. US Geological Survey

Open-File Report 88-729, 113 p.

Reilly, T.E., Harbaugh, A.W., 1993a. Simulation of cylindri-

cal ¯ow to a well using the US Geological Survey modular

®nite-di�erence groundwater ¯ow model. Ground Water 31

(3), 489±494.

Reilly, T.E., Harbaugh, A.W., 1993b. Source code for the

computer program and sample data set for the simulation

of cylindrical ¯ow to a well using the US Geological Survey

modular ®nite-di�erence groundwater ¯ow model. US

Geological Survey Open-File Report 92-659, 7 p.

Schenk, J., Poeter, E., 1990. Rivint: an improved code for

simulating surface/groundwater interactions with

MODFLOW. Colorado Water Resources Research

Institute, Completion Report, No. 155.

Shapiro, A.M., Margolin, J., Dolev, S., Ben-Israel, Y., 1997.

A graphical user interface for the US Geological Survey

modular three-dimensional ®nite-di�erence groundwater

¯ow model (MODFLOW-96) using Argus numerical en-

vironments. US Geological Survey Open-File Report 97-

121, 50 pp.

Wingle, W.L., 1997. Evaluating subsurface uncertainty using

modi®ed geostatistical techniques. Ph.D. thesis, #T-4595,

Department of Geology and Geological Engineering,

Colorado School of Mines, Golden, CO, 231 pp.

Wingle, W.L., Poeter, E.P., McKenna, S.A., 1995. UNCERT:

a geostatistical uncertainty analysis package applied to

groundwater ¯ow and contaminant transport modeling.

Colorado School of Mines, unpublished report, 464 pp.

Zheng, C., 1990. MT3D: a modular three-dimensional trans-

port model. S.S. Papadopulos and Associates, Bethesda,

MD, unpublished report.

R.B. Winston / Computers & Geosciences 25 (1999) 377±382382