We all know that the world has a huge problem with water. We don't have enough of it in the places we need it. There are at least three solutions that could change this, and could be available by the middle of this century: we could make water, seed clouds and scale up desalination programs. But each of these solutions has massive problems that need to be solved before they're usable.
However we do it, we will have to ensure we do not reach the end of water. That would be the end of life.