PHAST (Parkhurst et al., 2010) is a program for simulating groundwater flow, solute transport, and multicomponent geochemical reactions in three-dimensional saturated groundwater flow systems. It can calculate a wide range of equilibrium and kinetic geochemical reactions. Flow and transport calculations are based on a modified version of HST3D, and geochemical reactions are calculatedwith the geochemical model PHREEQC.
Fig. 1: Example of a transport simulation usind PHAST. The pH value is shown in a range between 6.99 (blue) and 8.28 (red) after 100.000 s model time and assuming an inflow from the left and an outflow on the right.
The most recent version of PHAST may be obtained from the USGS here.
Parkhurst, D.L., Kipp, K.L., and Charlton, S.R., 2010, PHAST Version 2 - A program for simulating groundwater flow, solute transport, and multicomponent geochemical reactions: U.S. Geological Survey Techniques and Methods 6–A35, 235 p.