Interestingly enough, I was just researching water harvesting in desert regions.
Here in Dallas, we're having a problem with the ponds drying up. I'm working on some ideas to help a local park (with their permission) and this
was one of the ones I looked at. It's not usable in a natural park, but I've found some other techniques that can save our ponds.
This kind of idea needs to be popularized among gardeners and organic growers. It does need modification (there are restrictions on how much water
you can take from the rivers -- and our rivers aren't particularly clean) but this combined with other ideas should be promoted to certain groups.