When at least one generating unit is defined for the power plant <Waterway designer> can be started.
The <Waterway designer> will initially offer a default waterway. 
The default waterway is modified by a "drag and drop technique" and "clicking" items to match the actual power plant. Typically tunnels are "dragged" between nodes.

Waterway designer; connection between headwater, brook intake, node and plant.

Clicking the different symbols windows for adding or modifying data will be opened. The intake dam and gate window are shown. The arrow-symbols indicate tunnels.

Headwater. Diagram; relation between area and surface level