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MODFLOW 6, the newest version of the world’s most widely used groundwater modeling software, is now available for download from the U.S. Geological Survey (USGS). Redesigned to improve user experience and accommodate future features, MODFLOW 6 introduces a model coupling framework to the program that, according to USGS, has been used by academics, private consultants, and government scientists for more than 30 years to accurately, reliably, and efficiently simulate groundwater flow.

Originally released in 1984 and updated in 1988, 1996, 2000, and 2005, the sixth core version of MODFLOW was redesigned from the ground up to incorporate many of the new advances in groundwater modeling developed during the last decade. Many of these new advances are based on the use of more flexible grids to discretize an aquifer system or the capability to couple other hydrologic processes with groundwater flow.

MODFLOW 6 uses an object-oriented framework that allows new packages and models to be added to the software and allows any number of models to be tightly coupled together at the matrix level, with special emphasis placed on designing a program that can be expanded in the future.

The groundwater flow model is the first to be released in the MODFLOW 6 framework. It supports regular MODFLOW grids consisting of layers, rows, and columns, and it also supports more flexible grids that may conform to irregular boundaries or have increased resolution in areas of interest. Solutions for solving groundwater flow can be formulated using a Newton-Raphson approach or the traditional approach available in previous versions. There are also methods for handling full three-dimensional anisotropy.

To modernize user interaction with the program, the MODFLOW 6 input structure was redesigned. Within package input files, information is divided into blocks, and informative keywords are used to label numeric data and activate options. This new input structure was designed to make it easier for users to adjust simulation options in an intuitive manner, reduce user input errors, and allow new capabilities to be added without causing problems with backward compatibility.

The USGS is beginning to transition to the MODFLOW 6 model code for the simulation of groundwater systems.  The program has been rigorously tested and reviewed, and new capabilities are under development. It is expected that this new version will keep MODFLOW as the simulation code of choice by the groundwater community.

MODFLOW 6 software and user guides are available for download at https://water.usgs.gov/ogw/modflow/MODFLOW.html.

Information provided by the U.S. Geological Survey (www.usgs.gov).