USGS

User Guide for the Drawdown-Limited, Multi-Node Well (MNW) Package for the U.S. Geological Survey's Modular Three-Dimensional Finite-Difference Ground-Water Flow Model, Versions MODFLOW-96 and MODFLOW-2000

By Keith J. Halford, and Randall T. Hanson

 

U.S. GEOLOGICAL SURVEY

Open-File Report 02-293

Sacramento, California 2002


Prepared in cooperation with the Santa Clara Valley Water District


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Abstract

A computer program called the drawdown-limited, Multi-Node Well (MNW) Package was developed for the U.S. Geological Survey three-dimensional finite-difference modular ground-water flow model, commonly referred to as MODFLOW. The MNW Package allows MODFLOW users to simulate wells that extend beyond a single model node. Multi-node wells can simulate wells that are completed in multiple aquifers or in a single heterogeneous aquifer, partially penetrating wells, and horizontal wells. Multi-aquifer wells dynamically distribute flow between nodes under pumping, recharging, or unpumped conditions. Variations in intraborehole flow can be simulated with the MNW Package, which is limited by how finely an aquifer system has been discretized vertically. Simulated discharge from single-node and multi-node wells also can be drawdown limited, which is user specified for pumping or recharging conditions. The MNW Package also has the ability to track potential mixes of a water-quality attribute. Simulated wellbore flow can be compared with measured wellbore flow, which provides another constraint for model calibration.

Table of Contents

Preface

Abstract

Introduction

Wellbore Flow in Analytic Solutions

Wellbore Flow Measurements

Significance of Nonuniform Wellbore Flow

Previous Modeling of Multi-Aquifer Wells

Modeling Multi-Aquifer Wells

Purpose and Scope

Multi-Node Well (MNW) Package Capabilities

Implementation of Drawdown-Limited, MNW Package

Drawdown-Pumping Constraints in MNW Package

Applicability and Limitations

Input Instructions for MNW Package

Input Data for MNW Package

Explanation of Fields Used in MNW Package Input

Ouput Data for MNW Package

Example Problem

MNW Data Input for Example Problem

Selected Model Output for Example Problem

References Cited

Appendix

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