User's guide of Proceessing Modflow 5.0

Processing Modflow 83
boundaries between pairs of adjacent cells in the finite-difference grid. Refer to Hsieh and
Freckleton (1993) for the numerical implementation of the Horizontal-Flow Barrier package.
A horizontal-flow barrier is defined by assigning the following values to a model cell in the
Horizontal-Flow Barrier Package dialog box (Fig. 3.18):
- Barrier Direction [-]; and
-1
- (Hydraulic Conductivity/Thickness) of the barrier TDW [T ] for unconfined layers or
-1
(Transmissivity/Thickness) of the barrier TDW [LT ] for confined layers.
Fig. 3.18 The Horizontal-Flow Barrier Package dialog box
The barrier direction indicates the cell face where the barrier is located. To erase an existing
barrier, use zero for the barrier direction. The second value TDW gives the hydraulic
characteristic of the barrier. If a layer is unconfined (type 1 or 3), TDW is the barrier hydraulic
conductivity divided by the thickness of the barrier. If a layer is confined (type 0 or 2), TDW is
the barrier transmissivity divided by the thickness of the barrier. The barrier thickness is included
implicitly in TDW.
MODFLOW < Interbed Storage
For steady state flow simulations, this menu item is not used and is therefore dimmed.
Groundwater is released from storage under conditions of decreasing hydraulic head. The
released water volume is proportional to the compressibility of the soil matrix and water, because
a reduction of the hydraulic head results in an increase in the effective stress on the soil skeleton
and a decrease of the water pressure. Increasing effective stress on the soil skeleton results to
deformation (compaction) of the soil matrix. The Interbed Storage package (Leake and Prudic,
1991) calculates the water volume released from storage and simulates elastic and inelastic
3.6.1 MODFLOW