Right now, my garden is getting a lovely watering. We're fortunate to be enjoying a summer with a nice mix of rain and sun. I know many people all over the world right now are suffering through a hot, dry summer, and often, serious local drought. This is a real problem - the Southwestern Drought is essentially expected not to end in our lifetimes. Much of the best farmland in the world is now in drought conditions. We're deeply grateful that our land is pretty well situated for water. Still, we don't take it for granted. We mulch our gardens, pour our dishwashing liquid and cooled cooking water on the potted plants, use a composting toilet and otherwise focus a lot of energy on the conservation of water, simply because we don't like waste, and because the time may come when these practices will be necessary.
Which is why it is so urgent that, whenever possible, we keep collect water off our roofs. Water that hits asphalt or gravel represents a real management problem for towns and cities, causing flooding, and when it soaks into sewers, it is contaminated. It would be wiser to catch water as much as possible where it strikes the ground and make the best use we can of it - for irrigation, clothes washing, hair washing. I was horrified to learn that some American cities prohibit rainbarrels - personally, I think this is madness. I understand that dry areas depend on their runoff, but in many cases, such a large portion is lost or contaminated in heavy rainfall that allowing homeowners to capture a few hundred gallons would represent a signficant net benefit. And because industrial agriculture always uses more water than growing your own food, if people are capturing rain water for irrigation, that has even greater net benefits. We simply can't afford to let this resource go.
The simplest option here is a rainbarrel - any food grade plastic barrel will do, and there are cheap ones out there, or you can get something pretty and fancy that will make your homeowner's association happy. Hook it up to your gutters, and you are set to go. A few more and you've got more. You can put a couple on your barn, or your garage as well, or even your garden shed, so water things there.
Even better for us, is the cistern. This house came with an old one, but after several failed attempts to fix it, we're waiting to have the gentleman come and dig us another one. The beauty of the cistern is that it can collect vastly more water (5,000 gallons - our rainbarrels together can only collect 200), and because it is set in the ground below the frost line, won't freeze. The whole set up, including a hand pump for our kitchen sink costs about $1800 dollars - not cheap, but worth it for the security of non-electric, soft water (our well water is hard as nails and has sulfur and iron galore) that comes into the house without going out with a bucket. It cost only a little more than a manual pump on our drilled well.
Rainwater is great for irrigation, and some people even raise fish in their rain barrels. I can't help you much there, but I do know that I love the way my hair feels when it is washed with rainwater. I can't wait for the cistern to be finished!