The University of Melbourne has been studying the use of rainwater capture for irrigating vegetable gardens:
http://www.theage.com.au/national/education/voice/turning-stormwater-into-food-20130404-2h91j.html
and
http://www.landfood.unimelb.edu.au/green/water.html#vegetable.
[THIS IS A YOUTUBE PIECE ON JIM MERKEL WHO WROTE THE BOOK "RADICAL SIMPLICITY". HE HAS A 35 MINUTE DOCUMENTARY ON NETFLIX. REALLY A REMARKABLE MESSAGE.]
THIS IS A CLIP FROM THE ECOFARM CONFERENCE WEBSITE: Here is a link to the site.