User's guide of Proceessing Modflow 5.0

100 Processing Modflow
stresses (excitations) represented in the model, e.g., pumping well or recharge; (2) cell-by-
cell storage terms, which give the rate of accummulation or depletion of storage in an
individual cell; (3) cell-by-cell constant-head flow terms, which give the net flow to or from
individual constant-head cells; and (4) internal cell-by-cell flows, which are the flows across
individual cell faces, that is, between adjacent model cells. The cell-by-cell flow terms are
used for calculating water budgets and for particle tracking and transport simulations by
PMPATH and MOC3D. The cell-by-cell flow terms are saved in the unformatted (binary)
file BUDGET.DAT.
< Subsidence is the sum of the compaction of all model layers, for which the interbed strorage
calculation is turned on (see Layer Type in section 3.4).
< Compaction of individual layers is the sum of the calculated compaction and the user-
specified starting compaction in each layer.
< Preconsolidation head is the previous minimum head value in the aquifer. For model cells
in which the specified preconsolidation head is greater than the corresponding value of
starting head, the preconsolidation head will be set to the starting head. Subsidence,
compaction and preconsolidation head are saved in the unformatted (binary) file
INTERBED.DAT.
< Interface file to MT3D is an unformatted (binary) file containing the computed heads,
fluxes across cell interfaces in all directions and locations and flow rates of the various
sinks/sources. The interface file is created by the LKMT package provided by MT3D or
MT3DMS. There are three versions of the LKMT package, which are incorporated in the
versions of MODFLOW contained in the PMWIN (see MODFLOW < Run... below). The
LKMT1 package creates interface file to the version 1.xx of MT3D. The LKMT2 package
creates interface file to MT3D96 and MT3D_Dod_1.5. The LKMT3 package creates
interface file to MT3DMS.
To check the simulation results, MODFLOW calculates a volumetric water budget for the entire
model at the end of each time step, and saves the results in the simulation record file
OUTPUT.DAT. A water budget provides an indication of the overall acceptability of the
numerical solution. In numerical solution techniques, the system of equations solved by a model
actually consists of a flow continuity statement for each model cell. Continuity should therefore
also exist for the total flows into and out of the entire model or a sub-region. This means that the
difference between total inflow and total outflow should equal the total change in storage. It is
recommended to read the record file. The record file also contains other essential information.
In case of difficulties, this supplementary information could be very helpful.
3.6.1 MODFLOW