Edwin Dysinger, a master gardener and co-founder of Seedtime, a garden planning and management app, recommends rain barrels as a sustainable source of water for your garden. Set up to catch the runoff from the gutters on your roof, he says, “1 inch of rainfall on 1000 square feet of collection surface will provide 623 gallons of water.” Even on a dry day, you’ll have rainwater to use in your garden. It is a sustainable and free source of water that can work in most climates.