Reply To: ethics, practical questions

Here’s an article about someone who harvests rainwater in Africa: http://www.theecologist.org/take_action/local_hero/270547/the_man_who_farms_water.html
It doesn’t go into a lot of detail about how the farmer accomplishes it, but the author of the article, Brad Lancaster, also wrote a book called Rainwater Harvesting for Drylands and Beyond. It’s worth reading.
As Jason mentioned, permaculture is a good source of info. I think all the books by Bill Mollison have a section on water in general and on drylands, and you can probably find at least one of the books at the library.
Look into the concept of permaculture zones, as well. When I was working in Reno, we usually did use some form of irrigation, even if it was temporary. But we divided the plants by irrigation zones. The ones that needed the most maintenance and water went around entrances and other places of importance where they would actually be used and enjoyed. The ones that needed no or very little irrigation went to natural areas or gardens that would get less attention.