GoPhast is a graphical user interface (GUI) for the USGS model PHAST.
PHAST simulates multicomponent, reactive solute transport in three-
dimensional, saturated, ground-water flow systems. PHAST can model both
equilibrium and kinetic geochemical reactions. PHAST is derived from 
HST3D (flow and transport) and PHREEQC (geochemical calculations). The 
flow and transport calculations are restricted to constant fluid density 
and constant temperature. The complexity of the input required by PHAST 
makes manual construction of its input files tedious and error-prone. 
GoPhast streamlines the creation of the input file and helps reduce 
errors. GoPhast allows the user to define the spatial input for the PHAST 
flow and transport data file by drawing points, lines, or polygons on 
top, front, and side views of the model domain. These objects can have up 
to two associated formulas that define their extent perpendicular to the 
view plane, allowing the objects to be three-dimensional. Formulas are 
also used to specify the values of spatial data (data sets) both globally 
and for individual objects. Objects can be used to specify the values of 
data sets independent of the spatial and temporal discretization of the 
model. Thus, the grid and simulation periods for the model can be changed 
without respecifying spatial data pertaining to the hydrogeologic 
framework and boundary conditions. This report describes the operation of 
GoPhast and demonstrates its use with examples. GoPhast runs on Windows 
2000, Windows XP, and Linux operating systems.