When I lived in Tucson a few years ago, I had a rainwater collection cistern and a passive rainwater harvesting system in my home landscape. The people who helped design these simple yet powerful techniques formed a larger organization called the American Rainwater Catchment Systems Association. There are some big names in the field who generally gather in these conferences. For those of you interested in rainwater harvesting, I would recommend attending, and if you can afford it, participating in one of the workshops they offer in conjunction with the event.
American Rainwater Catchment Systems Association 2011 National Conference
September 27 – 29