The Heat- and Solute-Transport Program (HST3D) simulates ground-water flow and associated heat and solute transport in three dimensions (Cartesian or cylindrical coordinates). The three governing equations are coupled through the interstitial pore velocity, the dependence of the fluid viscosity on temperature and solute concentration, and the dependence of the fluid density on pressure, temperature, and solute concentration. The solute-transport is given for a single solute species with possible linear-equilibrium sorption and first-order decay. Numerical solution are obtained for the dependent variables: pressure (relative to atmospheric pressure), temperature, and solute concentration (mass fraction).

The basic source-sink term represents wells. A complex well-flow model may be used to simulate specified flow rate and pressure conditions at the land surface or within the aquifer, with or without pressure and flow-rate constraints. Boundary-condition types offered include specified value, specified flux, generalized and river leakage, heat conduction, an approximate free surface (water-table), and two types of aquifer-influence functions. All boundary conditions can be functions of time.

The code calculates global flow, heat and solute balances, including fluxes through specified pressure, temperature and mass-fraction boundaries. Finite-difference techniques are used for spatial and temporal discretization of the governing equations. The flow, and heat- and solute-transport equations are solved after a partial Gauss-reduction scheme is used to modify them. The modified equations are more tightly coupled and have better stability for the numerical solutions.

Two techniques are available for solution of the finite-difference matrix equations. One technique is a direct-elimination solver, using equations reordered by alternating diagonal planes. The other technique is an iterative solver, using two-line successive overrelaxation. A restart option is available for storing intermediate time with modified boundary conditions.

Data input and output may be in metric (SI) units or inch-pound units. Output may include tables of dependent variables and parameters, zoned-contour maps (using character-based line printer plots), and line printer plots of the dependent variables versus time. Text output files may be edited for further postprocessing with independent graphic software.

SYSTEM REQUIREMENTS

Intel 80386/80486 based computer, 6.5 Mb of free RAM, at least 2 Mb of free disk space, DOS 3.0 or higher, math coprocessor.

Developer: K.L. Kipp (U.S. Geological Survey)