So SpaceX and the like are well underway to colonizing the Moon, but they've hit a snag. The colonists, of course, need water--and lots of it, for drinking, preparing food, growing plants, breathing, and other important stuff. Originally, the plan was to "mine" the lunar regolith, which contains a small amount of liquid water which could be extracted.
Unfortunately, the International Court of Justice recently ruled that the Outer Space Treaty prevents the mining of the Moon, which means that the lunar colonists must now find another way to obtain water. (Assume that the legal ruling cannot be overturned in any way, I'm more interested in the scientific possibilities.)
- The method of delivery should be both "reliable" and regular--it shouldn't only work half the times it's expected to, and the colonists should be able to expect when it comes so they don't get stranded without water.
- The method of delivery should be scientifically plausible within more or less the limits of cutting-edge technology, with reasonable extrapolations. This is in the near-future, so physics as we know it has not been massively overturned, and the rocket equation is tyrannical as ever. Assume that the cost of sending 1 kilogram of payload to the Moon is approximately 2500 USD.
- The method of delivery should be scalable to large populations (>10,000 people). As the colony grows, they don't want to have to keep changing their water supply methods, and would much rather pick one method and stick with it.