One can directly list and edit the Upstream Nodes (in view of the network topology) by going in the Tools Menu > Upstream Nodes.

The Upstream-Downstream direction defined in Geometry Mode determines the steady flow calculation. In unsteady flow, the topological direction of the reaches doesn’t matter.

Upstream Boundary Conditions will be the ones available to bring flow into the network. These are the Boundary Conditions types:

• "imposed discharge (pump)" ($Q(t)$) with a positive or nul discharge
• "fixed elevation" ($Z(t)$) with an elevation requiring a positive discharge considering topographic and hydraulic conditions of the network.

The Upstream Boundary Condition of type "fixed elevation" ($Z(t)$) is available in steady flow calculation since version 5.27 of SIC. To the best of our knowledge, it is the only software of this type having this possibility.

N.B. : It is quite possible to mix offtakes with Upstream Boundary Conditions and offtakes with Downstream Boundary Conditions in an Upstream Node. This only necessary condition in steady flow will be that the balance of incoming and outgoing flows should be positive.