SUTRA (Saturated-Unsaturated TRAnsport) is a computer program which simulates fluid movement and the transport of either energy or dissolved substances in a subsurface environment. The model employs a two-dimensional hybrid finite-element and integrated-finite-difference method to approximate the governing equations. SUTRA provides, as the primary calculated results: time-varying fluid pressures, and either solute concentrations or temperatures. SUTRA may also be used to simulate simpler subsets of the above processes.

SUTRA flow simulation may be employed for areal and cross-sectional modeling of saturated ground-water flow systems, and for cross-sectional modeling of unsaturated zone flow.

Solute transport is restricted to a single reacting species and accounts for solute sorption (linear, Freundlich or Langmuir equilibrium isotherm), zero- and first-order decay and zero order production, hydrodynamic dispersion (including corrections for anisotropy), and molecular diffusion. The code also supports varying density solute transport (i.e., coupling between flow and transport), and simulation of salt-water intrusion with either a dispersed or a sharp interface.

The simulation of energy transport is based on the change in time of the energy stored in both the solid matrix and the fluid. It includes heat advection (due to flow of water), effects of injection of water with a temperature different than the ambient temperature, water storage effects, thermal conduction (or heat diffusion), and energy dispersion.

Boundary conditions, sources, and sinks may be time-dependent. An option is available for storing intermediate results and restarting at the intermediate time. Options are also available to print fluid velocities in the system, to print fluid mass and solute mass or energy budgets for the system, and to make temporal observations at points in the system.

The model employs quadrilateral elements providing great flexibility in covering highly irregular model domains. The mesh may be coarsened using pinch nodes. The model supports anisotropy of permeability and heterogeneity with respect to most flow and transport parameters.

SUTRA has been modified by IGWMC to include three options for the moisture-characteristic curve during simulation unsaturated flow. These are: van Genuchten (1980), Brooks and Corey (1964), and input of tabular data for pressure, relative hydraulic conductivity, and moisture content.

SUTRA, as distributed by IGWMC, is a DOS-based program requiring Fortran-style input files. A graphical post-processor, SUTRA-PLOT, is distributed with SUTRA. SUTRA-PLOT can draw the finite element mesh, the model region boundary, and fluid velocity vectors. SUTRA-PLOT can plot contours of pressure, saturation, concentration and temperature within the model region. To run, SUTRA-PLOT requires only SUTRA input and output files. SUTRA is available in standard and extended memory versions. For SUTRA-PLOT, a standard runtime version is available; for extended memory versions, the program needs to be compiled with an appropriate compiler. You also can use a commercial contouring program to display results.

The public domain SUTRA package includes source code, executable image, and example data sets. The documentation contains installation procedures, instructions for input data format, the USGS SUTRA manual, change notices from Version 1.0 to 2.0, and the USGS user's manual for the SUTRA-PLOT contouring package.

SYSTEM REQUIREMENTS

Standard version: Intel 80i86 based computer, 640 Kb RAM, hard drive with about 3 Mb free disk space, DOS 3.0 or higher, math coprocessor.

Extended memory version: Intel 80386/80486 based computer, 4 Mb RAM, hard drive with about 3 Mb free disk space, DOS 3.0 or higher, math coprocessor; to run SUTRA-PLOT requires compiling with GKS drivers.

Author: C.I. Voss (U.S. Geological Survey).