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MODFLOW-2005 : the U.S. Geological Survey modular ground-water model--the ground-water flow process

Techniques and Methods 6-A16

Code and documentation for other water models are available at http://water.usgs.gov/software/ground_water.html .
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Abstract

This report presents MODFLOW-2005, which is a new version of the finite-difference ground-water model commonly called MODFLOW. Ground-water flow is simulated using a block-centered finite-difference approach. Layers can be simulated as confined or unconfined. Flow associated with external stresses, such as wells, areal recharge, evapotranspiration, drains, and rivers, also can be simulated. The report includes detailed explanations of physical and mathematical concepts on which the model is based, an explanation of how those concepts are incorporated in the modular structure of the computer program, instructions for using the model, and details of the computer code. The modular structure consists of a MAIN Program and a series of highly independent subroutines. The subroutines are grouped into 'packages.' Each package deals with a specific feature of the hydrologic system that is to be simulated, such as flow from rivers or flow into drains, or with a specific method of solving the set of simultaneous equations resulting from the finite-difference method. Several solution methods are incorporated, including the Preconditioned Conjugate-Gradient method. The division of the program into packages permits the user to examine specific hydrologic features of the model independently. This also facilitates development of additional capabilities because new packages can be added to the program without modifying the existing packages. The input and output systems of the computer program also are designed to permit maximum flexibility. The program is designed to allow other capabilities, such as transport and optimization, to be incorporated, but this report is limited to describing the ground-water flow capability. The program is written in Fortran 90 and will run without modification on most computers that have a Fortran 90 compiler.

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
MODFLOW-2005 : the U.S. Geological Survey modular ground-water model--the ground-water flow process
Series title:
Techniques and Methods
Series number:
6-A16
Edition:
-
Year Published:
2005
Language:
ENGLISH
Description:
1 v. (various pagings) : ill. ; 28 cm.
Larger Work Type:
Report
Larger Work Subtype:
USGS Numbered Series
Larger Work Title:
Book 6: Modeling techniques, Section A. Ground-water