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3.4.1 Anisotropy Ratios

By default, the aquifer system is assumed to be isotropic (i.e., Kxx/Kzz = Kxx/Kyy = 1). To apply vertical
and/or anisotropy ratios, check the box(es) next ‘Kxx/Kyy’ and/or ‘Kxx/Kzz’ and enter the desired
ratio(s) in the text box(es) (see Figure 3-5).

3.5 Recharge and Surface Seepage

In MAGNET, water may be added to the aquifer through the top boundary as recharge
(precipitation/surface water that infiltrates down to the water table) or can be removed through the top
boundary as surface seepage (in the case where the hydraulic head is larger than the land surface
elevation).

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Recharge to the aquifer is treated as specified flux [L T ] that is constant in time . Users can specify a
single value to be applied through the model domain (default setting), or can use the spatially-variable
recharge raster available from the IGW server.
User raster files can also be used to assign recharge values across the model domain. To do this, check the
box next to the ‘Import’ link, then select the link to open a file browser. Browse to and select the appropriate
file for importing. A prompt with file metadata will appear after the file has been uploaded, and the file
path and name will appear in the text box next to ‘Import’. If the units of the recharge raster are not meters
per day, use the text-box next to ‘multiplier to m/day’ to enter the appropriate multiplier, e.g., to convert
from in./yr to m/day, enter 0.0000696, as 1 in./yr. = 6.96 x 10 m/day.
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Note that zones may be added in the model domain to assign a recharge value that overrides the value(s)
provided in the Default Parameters and Options menu (see Section 4.2)

Figure 3-6: Options for applying recharge along the top of the model boundary. Default values/settings are shown.

Surface seepage is computed as the amount of hydraulic head exceeding the land surface (computed as
aquifer head minus land elevation) multiplied by the leakancy (a factor representing hydraulic
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conductivity per unit thickness of the land surface). The default value is 1 day .
To remove surface seepage as a possible sink of groundwater for topmost model cells, set the leakancy to
zero.

3 Interactive Groundwater (IGW) includes a module for process-based and non-process-based watershed modeling,
which enables time-dependent recharge simulation.
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