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Techniques and Methods 6-A30

Revised Multi-Node Well (MNW2) Package for MODFLOW Ground-Water Flow Model

By Leonard F. Konikow, George Z. Hornberger, Keith J. Halford, and Randall T. Hanson
with a section (appendix 3) by Arlen W. Harbaugh

Chapter 6 of
Section A, Ground water
Book 30, Modeling Techniques
Version 1.1

Thumbnail of and link to report PDF (3.12 MB)Abstract

Wells that are open to multiple aquifers can provide preferential pathways to flow and solute transport that short-circuit normal fluid flowlines. Representing these features in a regional flow model can produce a more realistic and reliable simulation model. This report describes modifications to the Multi-Node Well (MNW) Package of the U.S. Geological Survey (USGS) three-dimensional ground-water flow model (MODFLOW). The modifications build on a previous version and add several new features, processes, and input and output options. The input structure of the revised MNW (MNW2) is more well-centered than the original verion of MNW (MNW1) and allows the user to easily define hydraulic characteristics of each multi-node well. MNW2 also allows calculations of additional head changes due to partial penetration effects, flow into a borehole through a seepage face, changes in well discharge related to changes in lift for a given pump, and intraborehole flows with a pump intake located at any specified depth within the well. MNW2 also offers an improved capability to simulate nonvertical wells. A new output option allows selected multi-node wells to be designated as “observation wells” for which changes in selected variables with time will be written to separate output files to facilitate postprocessing. MNW2 is compatible with the MODFLOW–2000 and MODFLOW–2005 versions of MODFLOW and with the version of MODFLOW that includes the Ground-Water Transport process (MODFLOW–GWT).

Posted August 2009

Revised February 18, 2010

For additional information, please contact Leonard F. Konikow.

Part or all of this report is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of Adobe Reader, free of charge.


Suggested citation:

Konikow, L.F., Hornberger, G.Z., Halford, K.J., and Hanson, R.T., 2009, Revised multi-node well (MNW2) package for MODFLOW ground-water flow model: U.S. Geological Survey Techniques and Methods 6–A30, 67 p.



Contents

Preface

Abstract.

Introduction

Conceptual Model and Numerical Implementation

Simulation of Pumping and Nonpumping Wells

Head Loss Terms

Calculation of Water Level and Flow in the Multi-Node Well

Specifying the Location of Multi-Node Wells

Model Features and Processes

Description of Test Problems

Fully Penetrating Pumped Well in Ideal Confined Aquifer (Lohman Problem)

Long, Unpumped Observation Well (Reilly Problem)

Partial Penetration

Seepage Face

Constraints on Pumping Rate

Flowing Wells: Special Application of Constraints on Pumping Rate

Pump Capacity

Horizontal and Slanted Wells

Well Screen Variability

Flow Routing in Borehole

Solute Transport

Code Efficiency

Summary and Conclusions

Acknowledgments

References Cited

Appendix 1—Data Input Instructions for Multi-Node Well (MNW2) Package

Appendix 2—Selected Input Data and Printed Results for Sample Problem

Appendix 3—Program to Convert MNW1 Input Data to MNW2 Input Data



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