Found
this website via Facebook (it's in Spanish but you can translate). Seems like a great idea in dry climates. Only thing I don't like is the release of BPAs from plastic. I'm trying to think of other things to reuse for this.
Glass beer bottles would work in the ground to hold the water (as long as you're careful and won't knock it with a wheelbarrow) but a larger glass container over it might be harder to find. I thought about burying the beer bottles a little underground and then putting a large mason jar over that. Still, I don't have too many mason jars lying around that I don't want to use for canning.
Anyone have an idea?