User's guide of Proceessing Modflow 5.0

Processing Modflow 115
MOC3D < Strong/Weak Flag
A flag is required for each cell with the transport subgrid. Where fluid source is strong, new
particles are added to replace old particles as they are advected out of that cell. Where a fluid sink
is strong, particles are removed after they enter that cell and their effect accounted for. Where
sources or sinks are weak, particles are neither added nor removed, and the source/sink effects
are incorporated directly into appropriate changes in particle positions and concentrations. A
strong source or sink cell is indicated by the cell value of 1.
MOC3D < Observation Wells
Cells of the transport subgrid can be designated as observation wells by assign the value of 1 to
the cells. At each observation well, the time, head, and concentration after each particle move
will be written to the separate output file MOCOBS.OUT saved in the same folder as your model
data. Note that this feature is to facilitate graphical postprocessing of the calculated data using
other software package outside of PMWIN.
MOC3D < Sink/Source Concentration
This menu is used for specifying the concentrations of point or areally-distributed sources,
including fixed-head cells, general-head boundary cells, rivers, wells and recharge cells. Except
the concentrations associated with fixed-head cells, all source concentrations are specified by
using the Data Editor. If the concentration of a fluid source is not specified, the default value
for the concentration is zero. The source concentration associated with the fixed-head cells are
specified in the Source Concentration (Fixed-Head) dialog box (Fig. 3.37). The fixed-head
cells are grouped into zones, which are defined by specifying unique negative values to the
IBOUND array (see section 3.4). Each zone has an associated source concentration.
The concentration in the fluid leaving the aquifer at fluid sinks is assumed to have the same
concentration as the fluid in the aquifer. However, if the fluid sink is associated with evaporation
or transpiration, it is assumed that the fluid discharge mechanism will exclude dissolved
chemicals, which results in an increase in concentration at the location of the sink.
Items of this menu are dimmed if the corresponding hydraulic features given in the
Models