Release of New Report Entitled "SUTRA: Saturated-Unsaturated Transport, a finite-element simulation model for saturated-unsaturated, fluid- density-dependent ground water flow with energy transport or chemically-reactive single-species solute transport"



             UNITED STATES DEPARTMENT OF THE INTERIOR
                        GEOLOGICAL SURVEY
                        RESTON, VA. 22092

In Reply Refer To:                            June 18, 1985
WGS-Mail Stop 411


GROUND WATER BRANCH TECHNICAL MEMORANDUM NO. 85.03

Subject:  PUBLICATIONS--Release of New Report Entitled "SUTRA:
                        Saturated-Unsaturated Transport, a finite-
                        element simulation model for saturated-
                        unsaturated, fluid- density-dependent
                        ground water flow with energy  transport
                        or chemically-reactive single-species
                        solute transport" by Clifford I. Voss

The subject report has recently been approved and printed as
Water-Resources Investigations Report 84-4369.  Copies are being
sent under separate cover to all District Offices and some
Subdistricts.

The report documents a state-of-the-art ground-water transport-
simulation model known as SUTRA.  In addition, the report provides
an excellent description and explanation of the physics of ground-
water flow and transport.  We recommend that this very thorough
work be read by all individuals interested in attaining an
understanding of density-dependent ground-water flow and transport
in addition to those individuals interested in applying the
computer code.

Simulation using SUTRA is in two space dimensions in either the
areal plane or in a cross-sectional plane.  The third dimension is
accounted for by allowing the thickness to vary from point to
point.  The spatial coordinate system may be either Cartesian
(x,y) or radial-cylindrical (r,z).  Areal simulation is usually
physically unrealistic for two-dimensional variable-density fluid
problems.

Ground-water flow is simulated through numerical solution of a
fluid-mass-balance equation.  The ground-water system may be
either saturated, or partly or completely unsaturated.  Fluid
density may be constant, or vary as a function of either solute
concentrations or fluid temperature.

SUTRA tracks the transport of either solute mass or energy (heat)
in the flowing ground water through a unified equation which
represents the transport of either solute or energy.  Solute
transport is simulated through numerical solution of a solute-
mass-balance equation where solute concentration may affect fluid
density.  The single-solute species may be transported
conservatively, or it may undergo equilibrium sorption (through
linear, Freundlich, or Langmuir isotherms).  In addition, the
solute may be produced or decayed through first- or zero-order
processes.

Energy transport is simulated through numerical solution of an
energy-balance equation.  The solid grains of the aquifer matrix
and fluid are assumed to have equal temperature locally, and fluid
density and viscosity may be temperature dependent.

SUTRA is a very powerful, and accordingly very complex, numerical
simulator.  Because of the complexity of the physics governing the
systems and the approximations made by the numerical algorithms,
extreme care must be taken to properly use and interpret results
generated by this method.  The author provides some insight and
guidelines as to proper discretization and problem formulation for
optimal use of this numerical simulator.



                                   (s) Thomas E. Reilly
                                   Hydrologist

WRD Distribution:  A, B, S, FO, PO