You can buy a water butt that collects rain water from the guttering. I have one next to my garage.
Also, the guttering on my house is blocked (by moss, not intentionally) and I notice the water falls onto the paving slabs and runs into the lawn... which is bad on one level (lazy me!) but it goes back into the water table rather than running away into the drainage system, which is a problem over here as so many people put concrete over their drives. Ok, I'm rambling now.