There is a world out there, with people fairly like us (minor physical distinctions, irrelevant to the question), and with technology on par with ours, but with a very different religion.
The world (unified government) has this state religion. This religion is
- Based around water
- 'Good' deity lives in sky, 'bad' in the ocean
- Purification rituals are performed with holy (rain) water
- State church dispenses rituals
- Very lucrative - the ritual includes a tithe
- Tithe amounts to about $50 a year per person, consuming about 3 liters of rainwater a year per person
The government, in an attempt to increase profits, has set itself on the task of collecting more rainwater - more money! However, attaining enough rainwater to support the world population of 9,000,000,000 people is understandably difficult. So, the solution is determined to be a vast rainwater collecting scheme.
The location on the planet, with similar ecosystems to earth, and a similar rainfall capacity as earth, has not been set - the scheme could be anywhere or everywhere. Similarly, the method has not been decided upon.
Most importantly, the maximum amount of rainwater is to be delivered to cities, at distances of 250 km in rainforests, 100 km in temperate climates (prairies, deciduous forests, etc), 150 km in snowy climes, and 100 km (on average) from any other climate. No one should be harmed - that is bad publicity. The next goal (and the one the government is most willing to give up) is to hide the operation - there is a minute chance of people losing faith. But that faith can be recovered. As such the goal is expendable. Finally, the lowest cost in an economic system similar to ours is also a minor but desirable goal.
All in all, how might a government attain the greatest amount of rainwater, transport it with minimal loss in both rainwater and money, and deliver to cities at specified distances, all safe, cheap, and (hopefully) hidden?
Note Desalinating seawater is out of the question - tainted by the evil deity.
Note If rainwater touches the earth or any water that touches the earth it is rendered groundwater, however certain pools can be blessed if they are artificially constructed and do not touch the ground.