PUBLICATIONS--Release of two new reports documenting numerical models for the analysis of solute transport in ground-water systems

                        GEOLOGICAL SURVEY
                        RESTON, VA. 22092

In Reply Refer To:                           June 2, 1987
WGS-Mail Stop 411


Subject:  PUBLICATIONS--Release of two new reports documenting
                        numerical models for the analysis of
                        solute transport in ground-water systems

The two subject reports are:

1.   Kipp, Kenneth L., 1987, HST3D:  A computer code for
     simulation of heat and solute transport in three-dimensional
     ground-water flow systems:  U.S. Geological Survey Water-
     Resources Investigations Report 86-4095, 517 p.

2.   Lewis, Frank M., Voss, Clifford I., and Rubin, Jacob, 1986,
     Numerical simulation of advective-dispersive multisolute
     transport with sorption, ion exchange and equilibrium
     chemistry:  U.S. Geological Survey Water-Resources
     Investigations Report 86-4022, 165 p.

Both reports document powerful numerical simulators that represent
the state-of-the-art of documented computer models in the U.S.
Geological Survey.  As such, both computer models are intended are
research endeavors, where use and interpretation of the code and
results is primarily the responsibility of the investigator.

The first report, the Heat- and Solute-Transport Program (HST3D)
simulates ground-water flow and associated heat and solute
transport in three dimensions.  The HST3D program may be used for
analysis of problems such as those related to subsurface-waste
injection, landfill leaching, saltwater intrusion, freshwater
recharge and recovery, radioactive-waste disposal, hot-water
geothermal systems, and subsurface-energy storage.  The three
governing equations are coupled through the interstitial pore
velocity, the dependence of the fluid density on pressure,
temperature, and solute-mass fraction, and the dependence of the
fluid viscosity on temperature and solute-mass fraction.  The
solute-transport equation is for only a single, solute species
with possible linear-equilibrium sorption and linear decay.

The HST3D code uses finite-difference techniques to discretize the
governing equations using a point-distributed grid.  The flow-,
heat-, and solute-transport equations are solved, in turn, 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.  It
is important to note that the computer storage and time demand of
three-dimensional transport codes, such as HST3D, is significant
and is much greater than most ground-water flow codes.

The second report, known as SATRA-CHEM, simulates fully saturated
two-dimensional transient or steady-state areal or cross-sectional
constant-density ground-water flow and multisolute transport.  The
options for transport under the condition of local equilibrium
are:  (a) linear sorption and up to two aqueous complexations, and
(b) binary ion exchange and a single complexation reaction
involving one of the exchanging species.  SATRA-CHEM is a modified
version of the computer code SATRA, which itself is a simplified
version of the flow and solute-transport model SUTRA (Voss, 1984).
A finite-element Galerkin scheme is used for spatial
approximations of the dependent variable and backwards finite-
differencing for its time derivative.  Hydraulic conductivities
can be anisotropic and variable in direction and magnitude on an
element wise basis.

One copy of each report is being sent under separate cover to all
District Offices and some Subdistricts in order that these
powerful tools will be available.  The HST3D code is available
from the SOFTEX system on the Prime (ID# VAKLK00001), and SATRA-
CHEM is available from Clifford Voss.  As the physics, chemistry,
and numerical techniques are nontrivial, a substantial time
investment is required to use these tools appropriately.  Thus, we
do not envision the use of these tools in routine or short-term
projects.  Projects planning to use either of these models must be
thoroughly planned and take into account the time required and the
possibility (which exists in all research work) of unforeseen
difficulties which may limit the use of these tools.

                                   (s) Thomas E. Reilly
                                   for Eugene P. Patten
                                   Chief, Office of Ground Water

WRD Distribution:  A, B, S, FO PO