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Documentation for the State Variables Package for the Groundwater-Management Process of MODFLOW-2005 (GWM-2005)

By David P. Ahlfeld,¹ Paul M. Barlow,² and Kristine M. Baker<sup>1

1</sup>University of Massachusetts
²U.S. Geological Survey

ABSTRACT Many groundwater-management problems are concerned with the control of one or more variables that reflect the state of a groundwater-flow system or a coupled groundwater/surface-water system. These system state variables include the distribution of heads within an aquifer, streamflow rates within a hydraulically connected stream, and flow rates into or out of aquifer storage. This report documents the new State Variables Package for the Groundwater-Management Process of MODFLOW-2005 (GWM-2005). The new package provides a means to explicitly represent heads, streamflows, and changes in aquifer storage as state variables in a GWM-2005 simulation. The availability of these state variables makes it possible to include system state in the objective function and enhances existing capabilities for constructing constraint sets for a groundwater-management formulation. The new package can be used to address groundwater-management problems such as the determination of withdrawal strategies that meet water-supply demands while simultaneously maximizing heads or streamflows, or minimizing changes in aquifer storage. Four sample problems are provided to demonstrate use of the new package for typical groundwater-management applications.

First posted March 7, 2011 Report PDF (1.11 MB) For additional information contact: U.S. Geological Survey Office of Groundwater 411 Federal Center Reston, VA 20192 (703)642-5001 http://water.usgs.gov/ogw/ 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:

Ahlfeld, D.P., Barlow, P.M., and Baker, K.M., 2011, Documentation for the State Variables Package for the Groundwater-Management Process of MODFLOW-2005 (GWM-2005): U.S. Geological Survey Techniques and Methods 6-A36, 45 p., at https://pubs.usgs.gov/tm/tm6-a36/.

Contents

Preface

Abstract

Introduction

Description of the State Variables Package

Definition of State Variables

State Variables in a GWM Formulation

Implementation of State Variables in GWM

Additional Extensions to GWM-2005 Necessary for the State Variables Package

Extended Definitions of External Variables

Extended Definitions of Objective-Function Types

Sample Problems

DEWATER-SV: Minimize Cost of Lowering Groundwater Levels

Groundwater-Management Problem

Selected Input and Output Files

MAXIMIN: Maximize the Minimum Hydraulic Head

Maximin and Minimax Formulations in Groundwater Management

Groundwater-Management Problem

Selected Input and Output Files

STREAMFLOW: Maximize Summer Streamflow

Groundwater-Management Problem

Selected Input and Output Files

STORAGE: Control Changes in Aquifer Storage

Groundwater-Management Problem

Selected Input and Output Files

Acknowledgments

References Cited

Appendix 1. Data-Input Instructions and Output Files

Appendix 2. Programmers' Guide to Implementation of State Variables in GWM-2005