User's guide of Proceessing Modflow 5.0

Processing Modflow 79
3.6 The Models Menu
3.6.1 MODFLOW
MODFLOW < Density
Using the Density package (Schaars and van Gerven, 1997), the water density of a “density-
layer” may differ from cell for cell. During a flow simulation the density-dependent flows will
be adapted into the system of flow equations and the hydraulic heads are calculated. It is assumed
that the density distribution and the internodal transmissivities remain constant during a flow
simulation. Therefore, density layers may only be used in combination with layers of the types
0 or 2 (confined). A density-layer is marked by using the Layer Options dialog box.
The density package requires the input of a reference density (which is normally set to the
density of freshwater) and the density distritution within the density-layers. These values are
specified by using the Data Editor:
-3
- Reference density (REFRHO) [ML ] and
-3
- Cell-Density [ML ].
Note that the Density package is supported only if you select the MODFLOW version
“MODFLOW + Density package from KIWA” in the Run Modflow dialog box. See
MODFLOW < Run... for more about the versions of MODFLOW.
MODFLOW < Drain
A drain is defined by using the Data Editor to assign three values to a model cell:
2 -1
- Drain hydraulic conductance (C d)
[L T ],
- Elevation of the Drain (d) [L] and
- Parameter Number [-]
The values C and d and the paramter number are shown from left to right on the status bar. The
d
parameter number is used to assign C as a parameter for an automatic calibration by the inverse
d
models PEST or UCODE, see PEST < Parameter List... or UCODE < Parameter List.... These
values are constant during a given stress period. For transient flow simulations involving several
stress periods, these values can be different from period to period.
3.6.1 MODFLOW