Alternatives to MODFLOW for Demanding Situations: A Current Overview

Tuesday, April 21, 2009: 4:30 p.m.
Coronado I (Hilton Tucson El Conquistador Golf & Tennis Resort )
Peter A. Mock, Ph.D., RG., PH. , Peter Mock Groundwater Consulting Inc., Paradise Valley, AZ
There are specific processes and/or geometries that may be better answered by
models other than MODFLOW.  This paper takes a current look at alternative
simulation codes and a few selected situations for which they may be most
effective.  During remediation of significant spills of organic compounds,
the flows of water, gas and NAPL may each play important, linked roles and a
true multiphase simulator provides a comprehensive basis for evaluating such
situations.  For rigorous consideration of non-Newtonian fluids created with
surfactants and/or flow at very low or very high Reynolds numbers, a wide array
of petroleum industry simulation codes have been developed. Pore-scale
interactions and molecular dynamics may be important in some situations and
investigation of key controlling parameters can be assessed with specialized
simulation codes, including “multi-physics” codes.  If the movement of the
porous or fractured framework for flow is significant and affects the flow of
the enclosed water, such as stress-sensitive formations during pumping, then the
analysis can benefit from fully coupled geomechanical/fluid flow codes. Finally,
there is the issue of geometry. There are situations where both wellbore/near-
well radial (2-D) flow and its transition to regional (3-D) flow is important.
For these situations finite element or finite volume simulation codes are
preferable.  Finite element/finite volume simulation codes also adapt handily to
sinuous hydrogeologic features such as slurry walls, fault systems and stream
corridors.  Likewise, multiple isolated areas of focused interest are naturally
handled by finite elements/finite volume codes.  While many situations are
simulated easily with MODFLOW, an ever-expanding array of alternative simulation
codes can be considered for specialized or especially demanding hydrogeologic
situations.