The choice of reaches is principally linked to the hydraulic constraints. In order to let the user visualize portions of the canal that he wants to treat together, he may group a number of reaches into a branch. A branch is therefore a group of reaches serially linked to one another.

Illustration of how a canal network is subdivided into reaches and branches.

If the canal is not looped nor branched, the division into reaches and branches is thus simplified to the scheme shown in Figure 2 (in this example the system has been divided into two branches).