In arid climates country houses were often built with a roof
catchment tank built in. Modern houses usually have roof guttering and can be easily adapted.
It works, we’ve done it for years! Though you need to filter the water for drinking, and those plastic tanks don’t keep water fresh. This is Ch 7 but the whole book is on the blog..
Fun feature i have been playing with here lately at the lake to help get off us off the grid for water. Had to do some Kentucky style jerry rigging, but when in Rome do as the Romans do! Our latest EDU release, this one from the water chapter. http://treeyopermacultureedu.wordpress.com/chapter-7-water/roof-water-catchment-and-tanks/