PHAST (PHREEQC And HST3D)
Criterion | Explanation |
General Description | PHAST simulates multi-component, reactive solute transport in three-dimensional saturated groundwater flow systems. |
Model Domain | Subsurface saturated zone |
Developer | US Geological Survey |
Hardware computing requirements | Can be run on most computer systems, including computers with Windows, Linus and Unix OS. PHAST may require large amounts of memory for execution (primarily dependent upon the number of nodes defined for the simulation grid). Run times may be long on single-processor machines. This is greatly reduced with the parallel (multiprocessor) version of PHAST, which requires libraries for MPI. |
Code language | Written in FORTRAN-90, C, and C++ |
Original applications | PHAST is a versatile groundwater flow and transport simulator that models a wide range of equilibrium and kinetic geochemical reactions. Applicable from laboratory-scale experiments to regional field scales. Used for studies in:
Not used for unsaturated-zone flow, multiphase flow, or density-dependent flow. |
Public/proprietary and cost | Public, No cost |
Physically or empirically based | Physically based |
Mathematical methods used | Flow and transport calculations are restricted to constant fluid density and constant temperature, based on a modified version of HST3D. Combined flow, transport, and geochemical processes are simulated by three sequential calculations for each time step:
The definition of leaky and flux boundary conditions select only exterior cell faces with a specified volume of the model domain, and boundary conditions are restricted to the area of definition, which may include fractions of cell faces. Data can be defined in a combination of map and grid coordinate systems, independent of a specific model grid. Two-dimensional interpolation is used to define top and bottom surfaces for 3D regions. An area-weighted scheme (natural neighbor interpolation) assigns elevation to a target point based on elevations at the nearest of scattered X, Y points. Three-dimensional interpolation assigns porous-media properties, boundary condition properties, or initial conditions of the closest scattered point to a target point. The interpolation allows for groundwater-level elevation and chemical data to be saved at the end of one run and used as initial conditions for a subsequent run, even if the grid spacing has been changed. |
Input data requirements | Node-by-node input is not required. Shape data can be imported from ArcInfo shapefiles and ASCII raster files, and from a simple X,Y,Z file format. Three required input files:
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Outputs | Data may be saved for:
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Pre-processing and post-processing tools | USGS Model Muse and Model Viewer |
Representation of uncertainty | The model does not have built-in uncertainty representation. This can be assessed for each specific case using sensitivity analysis. |
Prevalence | Mostly used in peer-reviewed work |
Ease of use for public entities | There are not barriers to public use. |
Ease of obtaining information and availability of technical support | A discussion forum and a mailing archive for questions and answers are accessible via https://wwwbrr.cr.usgs.gov/projects/GWC_coupled/phast/ Example problems are included in the examples directory of the installation. Bug reports and other comments can be submitted to h2osoft@usgs.gov. |
Source code availability | The source code is available in the /src directory of the application. |
Status of model development | Fully developed and ready for use |
Challenges for integration | Long run times when utilizing geochemical calculations make would make it difficult to couple with surface water models. It has never been used in the Delta. |
References
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. Available at: https://pubs.usgs.gov/tm/06A35/pdf/TM6-A35.pdf