User's guide of Proceessing Modflow 5.0

Processing Modflow 133
< Weighting Scheme is needed only when the implicit finite-difference method is used, i.e.,
the solution scheme is finite-difference and the iterative GCG solver is used. In the finite-
difference method, when computing the mass flux into a model cell by advection, the
concentration values at the cell interfaces between two neighboring cells are used. For the
upstream weighting scheme, the interface concentration in a particilar direction is equal to
the concentration at the upstream node along the same direction. For the central-in-space
weighting scheme, the interface concentration is obtained by linear interpolation of the
concentrations at the two neighboring cells.
As denoted in Zheng and Wang (1998), the central-in-space does not lead to any
numerical dispersion when the grid spacing is regular. However, if transport is dominated
by advection, the upstream weighting is preferred, as the central-in-space weighting scheme
can lead to excessive artificial oscillation.
< Particle Tracking Algorithm is used in combination with the method of characteristics.
The particle tracking options are the same as provided in MT3D.
MT3DMS < Dispersion...
MT3DMS and MT3D share the same dispersion paramters. See MT3D