I would like to use the information from the Swedish SMHI related with their hydrological model elements (catchment areas) that have a Containment hierarchy structure, each element has the information about its dowstream element, to select or highlight a whole catchment area like in the picture below:
The first step is to select them, but once that is done, of course there are other question.
Each element, among other data, has
AROID (the ID of the element) and
OMRID_NED (the ID of the element downstream).
I would like to do this in QGIS in a simple way, like a click in one element.