I live in the inland part of SoCal. My city allows grey water systems. My biggest household water uses are the washing machine and tub and shower. These are plumbed into a cistern that pumps the non sewage uphill to irrigate about a quarter acre of native trees, fruit trees, and aloe that forms my fire break. Drinking water isn't used on the landscaping. No lawns in my neighborhood!
We're trying to figure out a companion system to gather what little rain runs off the roof to irrigate another quarter acre on the other side of the house. That won't work but a couple of months a year, but it's worth doing. Huge amounts of water run off the hill behind the house and onto the fire road at my property line, but that would require a Olympic swimming pool sized cistern, and I can't see myself ever making that happen.
Still, I'm trying to do my part.
there are a lot of things that you can do in an arid climate to grow plants and even vegetables, but you do have to be willing to do some actual work. there are plenty of good things to learn from permaculture and i'm glad to see that many of the things practiced by others in arid climates do actually get picked up and used in other places.
setting up your land to slow, spread and soak in whatever water that falls on it and to learn how to use different methods of doing that. the most basic point though is that you must make sure your geology won't slip away from beneath you if you super-saturate it with retained water. same for building any dams or water retention systems - there are some things you want to know first before building dams or other retaining walls.