VS2DI — The Complete Guide: 2D Unsaturated Flow and Solute Transport
VS2DI is a USGS package for simulating water flow through variably saturated porous media in a 2D cross-section. It contains two simulators — VS2DTI for solute transport and VS2DHI for heat transport — and a program for viewing results. You draw the section, assign layers and boundary conditions, and run it all from the same interface, without writing input files by hand.
VS2DI
U.S. Geological Survey (USGS)
Graphical package for 2D simulation of unsaturated flow with solute or heat transport.
Get it from the vendorWhat you get
- Saturated and unsaturated flow — following the wetting front through the soil down to the water table.
- Solute transport — how a contaminant moves downward from the surface.
- Heat transport — soil and water temperature alongside the flow.
- Graphical editor — the section, soil layers and boundary conditions drawn with the mouse.
- Results viewer — maps and animations of moisture, concentration and temperature.
Who it suits and its limits
Water and environmental engineers looking at infiltration basins, leakage from a pond or seepage beneath an earth embankment, and lecturers teaching unsaturated flow. It is 2D only and runs on Windows only. The latest version (1.3) dates from 2018 and was tested on Windows 7, so newer systems may show issues.
Related tools
For variable-density flow and transport, including seawater intrusion — SUTRA. For regional groundwater models — MODFLOW 6. For contaminant transport in a MODFLOW model — MT3D-USGS.
SUTRA
U.S. Geological Survey (USGS)
Finite-element simulator for saturated–unsaturated, variable-density groundwater flow with solute or heat transport.
Get it from the vendor
MODFLOW 6
U.S. Geological Survey (USGS)
The world standard for groundwater flow and solute transport modelling, from the USGS.
Get it from the vendor
MT3D-USGS
U.S. Geological Survey (USGS)
Groundwater solute and contaminant transport simulator driven by MODFLOW flow results.
Get it from the vendorGSFLOW
U.S. Geological Survey (USGS)
Coupled groundwater and surface-water model for whole watersheds, linking PRMS with MODFLOW.
Get it from the vendorThe bottom line
VS2DI is one of the most approachable tools for understanding unsaturated flow in a cross-section. It is old and limited to 2D, but completely free and easy to learn.