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3.2 Model Grid and Solver Settings

In the top-left portion of the Default Parameters and Options menu, the user can select/input a number of
model grid options. This includes: the number of model nodes in the horizontal (west-east) direction (NX),
the number of sub-layers in the vertical direction (i.e., into the earth), matrix solver settings, and
multiplicative factors for spatially-explicit raster files of hydraulic conductivity and recharge (see Figure
3-2).

Figure 3-2: The Model Grid and Solver settings available in the Default Parameters and Options menu. Default
values/settings are shown.

The number of nodes in the north-south direction is automatically computed based on NX and the shape of
the model domain.

MAGNET allows for vertical discretization of geological (conceptual) layers into desired number of
computational layers. Subdividing can be done based on 1) the land surface as the top boundary surface
(this is the default setting); or 2) with a water table solved by a previously simulation within the study area
(check the box next to ‘SubLayers=’ to use this setting). In the latter case, the previous water table used for
sub-dividing must cover the entire model domain, but need not be the same size. However, what is most
common is to:
• first simulate the model domain without sub-dividing the aquifer in the vertical direction;
• then check the box next to ‘Water Table as Top’ in the Default Parameters and Options menu, save
the changes (click ‘OK’), and re-run the simulation.
In the Basic version of MAGNET, NX is limited to a maximum values of 40, and the number of geological
(conceptual layers) is restricted to one, and the number of computational layers is restricted to three. No
such restrictions apply for the Premium version of MAGNET. The Premium version does not limit grid
size nor the number of sub-layers in the vertical direction.
3.2.1 Zone Attributes Factors

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