A Brief Introduction to GFLOW

GFLOW is an analytical groundwater modeling program that was developed in 1995 by H.M. Haitjema. Haitjema presented the theoretical background for GFLOW in the book Analytic Element Modeling of Groundwater Flow. Analytical-element models serve as an alternative to the traditional numerical methods, and may be more computationally efficient in some situations. In analytical modeling, the groundwater-flow differential-equations can be solved exactly, whereas in numerical modeling, a small amount of error is generated.¹

GFLOW was used as the computational engine in the EPA’s Wellhead Analytic Element Model (WhAEM2000), and an open source version of the program is available from the EPA at: ftp://ftp.epa.gov/sandyrun/pub/WhAEM3_Development/

A professional version of GFLOW is available from the Haitjema Software (http://www.haitjema.com/). The newest version, GFLOW 2.1.2, includes a Windows based Graphical User Interface, and will generate MODFLOW files for areas of interest for detailed localized modeling.²

The analytical-element groundwater flow modeling method was originated by Otto Strack in the 1970s. Instead of setting up the groundwater flow problem based on the groundwater heads present in the aquifer, discharge potential terms are developed for the aquifer. Discharge potentials can be applied to confined, unconfined, homogeneous, and heterogeneous aquifers. Although the aquifer is not discretized in analytical-element methods, the surface water features are broken up into unique reaches and areas. These elements are all superimposed in order to obtain the final solution.³

1. Haitjema, H.M. 1995. Analytic element modeling of groundwater flow. San Diego, CA: Academic Press, 394 pp.

2. Haitjema Software. 2007. GFLOW. Available at: http://www.haitjema.com/

3. Kraemer, Stephen. 2005. WhAEM 2000:Analytic Elements Frequently Asked Questions (FAQ). Environmental Protection Agency: Office of Water. Available at: http://www.epa.gov/athens/software/whaem/press.html