Today's technology allows to carry oil via pipelines over thousands of kilometers.
So, it is thus possible to use similar pipelines to carry water accross countries.
The idea is to have a network going, for instance, from Asia to Africa through Europe.
The energy to drive the pumps will come from stations (and why not cities) built in deserts.
The cost to build such a system is certainly high but will be less than the benefits on the long-run:
- It will mitigate the future disasters due to floods.
- It will help to regulate temperatures between the countries.
- If the network is connected to the seas, it will mitigate the raise of their levels.
- It will bring water in any areas.
- It will mitigate people's migration.
Of course, there will be political issues to solve.
It might be an utopia but it is worth exploring it.