The MODFLOW Layer Groups dialog box is used to define the layer structure of a MODFLOW model. The MODFLOW Layer Groups dialog box is displayed by selecting Model|MODFLOW Layer Groups...

In the Layer Property Flow package in MODFLOW, layers can be either confined or convertible. Cells in convertible layers will either be confined or unconfined depending on whether the head is above or below the top of the cell. In addition, it is possible to have quasi-3-D models in which there is a gap between the layers. In such cases, the vertical hydraulic conductivity of the missing material is used to help calculate the conductance between the layers. Both the missing material and the model layers are represented in ModelMuse by layer groups. Layer group that represent model layers can be subdivided into multiple layers. This can simplify the process of defining layers when it is important to simulate vertical flow within an aquifer or if solute transport is simulated. More typically, however, each aquifer in the model will be represented by a single layer.

To define the layer structure of a MODFLOW model, the user adds or removes layer groups using the Add layer group , Insert layer group , and Delete layer group buttons on the left hand side of the MODFLOW Layer Groups dialog box.

The main properties of each the layer group is specified by selecting the layer group in the list of layer groups on the left and entering appropriate values on the tabs to the right. The user can select multiple layer groups by holding down the Ctrl key when selecting layer groups.

The MODFLOW Layer Groups dialog box has two tabs that are always visible, the Basics tab and the Discretization tab. If the SUB package is active, two more tabs, the No-Delay Beds and Delay Beds tabs, are visible. If the SWT package, the SWT tab is visible. If the Dispersion package in MT3DMS is selected, the Dispersion tab is visible.