In the first tutorial about boundary conditions an outlet was created to let water flow out of the system. Outlets created with

outlet = p.NewOutlet('name',position=position)

are in fact DirichletBoundary objects. Most connection types can be used to connect on the right side with an outlet. However, some connections in are gradient based (eg. the lateral darcian connections). For these connections, the outlet position is meaningful for the calculation of the distance and the potential head of the boundary condition matters. By default, the head of an outlet equals its z position. If this does not match your model well, eg. your boundary is a river or lake with a more or less fixed water level, the potential of the boundary condition can be changed:

# Set the outlet 0.5 m above the outlet height

outlet.potential = outlet.position.z + 0.5

The potential of the outlet can be adjusted during run time in the run time loop by reading from a file of predefined heads or from another model running in the same run time loop.

But what happens if the potential of the left side of the connection is lower than the potential of the boundary condition? As a default, outlets are not a water source, therefore no flux occurs. In the case illustrated above, when the boundary condition is something carrying water (river, like, groundwater table) one might prefer to use the boundary condition not only as a sink, but also a source, depending on the state of the connected water storages. In this case, cmf needs to be informed to handle the boundary condition as a source:

outlet.is_source=True