You'd be surprised how much water you can collect from your roof after a good rain. Here are step by step instructions how to build a rain barrel from a 55 gallon plastic drum.
Multiple rain barrels stacked for higher water pressure (& greater storage volume) (And anyone who's ever planted a garden and tried to use a rainbarrel for it KNOWS that one is definitely not enough!
Global Buckets: Olla Irrigation describes a DIY method of using terra cotta pots to make a "olla" or slow irrigation container to add to your garden plants or other containers. The best part is that water is released to the plants on demand, as needed.
Self Watering Garden Via Homemade Ollas -- water seeps through porous clay pots buried within the root zones of plants providing a continuous supply of water to the plants. No Evaporation!
Homemade Ollas ( info: ollas ) (pronounced OH-yas) the tops extend above the top of the ground so you may refill with water. The water slowly seeps out.