The Utopians are a wise and benevolent civilization with Ancient Rome-like technology. Unfortunately, they are so peaceful that they are constantly on the verge of being conquered by the neighboring and envious barbaric tribes.
So the Utopians prayed to their gods and they looked with favor to the poor mortals. And the Utopians were all raptured to the skies on Tolkien-like eagles and were given the magic substance: Handwavium.
When Handwavium is dropped on a cloud, the cloud becomes solid. It doesn't change shape anymore and you can walk on it and build with it. It also becomes fertile with handwave fruit trees and eddible handwave cereals. However, it still keeps afloat somehow.
The Utopians rejoice and start building their new city up there on a cumulus on the lowest étage (ca. 1.900-2.000 m high).
Unfortunately, they soon find the gods' blessing to be a curse. Even though they built their city on the lowest étage, it seems that all the rain falls from below their altitude, not from above them (I may be wrong on this one... if I am, please tell me, for I would like to be wrong), so they can't collect rainwater.
Handwavium, OTOH, has poisoned the water on the cloud they built in, so they can't collect water directly from their own cloud.
Also, as a roman-like civilization, they were very savvy on building aqueducts... but water doesn't flow upwards, as you all know. Using Archimedes' screws or drums lifted with cranes from that altitude is impossible and would never be able to supply a whole city.
The gods, when questioned, just shrug and say: "You can't wish for more wishes".
Is there any way to save Utopia from abandonment or catastrophe, all by the Utopians own devices?
Some help: There is a slight possibility that Handwavium may make the cloud a little heavier and so the city could drop some meters... how much of a drop would suffice?