Catchment Runoff can be directed to a groundwater node by dragging the Runoff/Infiltration symbol from the legend in the Schematic view, dropping it on a catchment, then dragging to a groundwater node. A groundwater node can receive inflow from more than one Catchment, as well as return flows from demand sites.
If using the Soil Moisture (two-bucket) method to calculate Catchment Runoff, and Catchment Runoff is directed to a groundwater node from that Catchment, the Soil Moisture method becomes a "one-bucket" representation. (see Overview of Catchment Calculation Methods).
Catchments can contribute runoff to one or more river nodes, and zero or more groundwater nodes.