Parallel Finite Element Model For Coupled Surface And Subsurface Flow In Hydrology: Province Of Santa Fe Basin, Absorbent

Abstract

The large spread in length scales present in the hydrological problems (i.e.
province of Santa Fe basin systems) requires a high degree of renement in the nite
element mesh and, then, requires very large computational resources. Also, in a 2D multiaquifer
model, the number of unknowns per surface node is, at least, equal to the number
of aquifers and aquitards. Moreover, if a pollutant transport model is used with the velocity
eld results, then it is desirable to have several sub-layers inside the aquifer in order
to recover the vertical gradient, which drives the transport of pollutant between aquifers.
This increases the number of unknowns and, also, the band-width of the associated FEM
matrix, so that the total computation time is roughly proportional to the square of the
number of vertical layers and sub-layers. Due to this fact, it is expected to have a very
high demand of CPU computation time, calling for parallel processing techniques.
A large scale C++ parallel FEM module using a general advection-diusion PETSc-FEM
code was written for hydrological problems. Several systems of aquifers/aquitards coupled
with a net of surface streams can be solved. The streams can be modelled with the
KWM (Kinematic Wave Model) approximation, 2D or 1D Saint-Venant model. There is
mass exchange between streams and aquifers through a resistance coecient at the stream
walls. Both Manning and Chezy friction models are available for the streams. Absorbent
boundary conditions are implemented in order to avoid wave re
ection for Saint-Venant
models.