Are you paying for that water you use to water your yard? Well if it rains anything like it does here in Seattle, you should be gathering that water for free. All you need to do is buy or make a rain barrel to collect the water. The rain barrel I use is a great rust orange color barrel that used to hold peppercinis. There are many types of rain barrels. You are bound to find one that will look nice in your yard. Place the rain barrel beneath the gutter spout and start collecting. IT IS THAT EASY. I bought a gutter extender so that I was able to properly route the water. Please don't drink the water as the run-off from your roof can add toxins, but it is great for most applications in the yard or your indoor plants.
Ideally having a cistern that will hold larger quantities of water is better, since there are times here in the summer where we don't see rain for weeks. Yes, don't laugh...that can happen here in Seattle. That way you will always have water available when you need it. You can also connect several rain barrels together to increase the amount of water you can collect. Make sure that your barrels come complete with mosquito netting as you don't want a breeding ground on your property.
Collecting rainwater has been enjoyable for me. Yes, I know I am probably not saving huge sums of money but to me it is the principle. Why pay for and use something that is given to us for free. There is something special about going over to my barrels, filling up the watering can (warning, it is slower than just turning on the hose spigot, but this reminds me to SLOW DOWN in life), and reusing the water in my garden. This water doesn't contain the added chlorine and flouride that the city puts in our water and the plants don't need it. They are happy, happy, happy with the recycled water they are given.