According to an article that I read, it is currently illegal in many states to collect rainwater and use it on a persons property for the use of watering your own plants, lawn, or even use it for drinking water. See the article:
http://www.pakalertpress.com/2013/04/29/video-collecting-rainwater-now-i...
This means that the rain from the sky essentially belongs to someone else. These are state laws, but should be protected by the federal government to help the environment and reduce energy costs of having water fall from the sky, be diverted to an aquifer and then routed back to the source so that it can then water a persons lawn.