I kinda found the idea of an gigantic aqueduct strange and overkill - here is what came to my mind on reading the lore-stuff:
Das Tal is a canyon situated near the sea. It is difficult to access due to sheer cliffs. The river enters the canyon via waterfalls and exits it with very strong currents in multiple estuaries. Thus Das Tal is also inaccessible via the river or the sea. The most sensible way for easy access would be something like lifts or cablecars.
To make what we can do with the mapping easy and sensible:
The river has carved the valley into different plateaus at different levels that are partially separated by chasms. Something causes highly different regions - the substance generating ice-energy, heat-energy, posion-energy, wind-energy, ... ? (Would need to visualize that a bit - the substance comes with spirits/ghosts in my imagination ...)