The Drain Return package causes water the leave the groundwater system when the head in a cell with a drain-return boundary rises above the elevation of the drain-return boundary. It also allows some or all of the water that exited through the drain-return boundary to return to the groundwater system at some other location. The pane for the Drain Return package is on the MODFLOW Packages and Programs dialog box under Head Dependant Flux.
On the DRT: Drain Return package pane, the user can define parameters for the drain-return boundaries. These parameters will be multiplied by user-specified multipliers to determine the drain-return conductances defined by parameters. The user can also set up drain-return boundaries that do not involve parameters. Objects must be used to define the locations of the drain-return boundaries.
Parameters can also be edited in the Manage Parameters dialog box.
The Drain package is similar to the Drain-Return package except it does not allow any of the water that leaves through a drain to re-enter the groundwater system.
