A Good Soaking
An introduction to water harvesting in the Southwest.
By Ann Phillips

Why go to the trouble of harvesting rainwater when it rarely rains in the desert? When people ask me this question during water harvesting talks I give in Tucson, Arizona (average rainfall 12 inches per year), I answer with another question: In a desert, how can you afford not to harvest rain when it finally falls?

Two wired gablons placed in a series slow down the flow of street runoff in a roadside ditch. Ann Phillips

To understand water harvesting, get a cupcake pan and turn it upside down. This simulates the popular mounded landscape design seen on commercial properties, residences, and road medians that have been professionally landscaped in the Southwest. When you “rain” on this upside-down pan with a watering can, water is deflected away from the mounds and flows off the pan. Now turn the cupcake pan right-side up and “rain” again. The depressions in the pan collect most of the water, and just a fraction drains away. This is water harvesting at its most basic. Water harvesting landscapes are creative variations on this theme.

According to the City of Tucson Water Harvesting Guidance Manual (2003), water harvesting is the “process of intercepting stormwater from a surface such as a roof, parking area, or land surface, and putting it to beneficial use.” Stormwater can be intercepted in shaped earthworks where it directly infiltrates the soil at a site and becomes immediately available for plant roots to access it, or it can be harvested in tanks and stored for later use. In either case, the goal of water harvesting is to put the water to good use to improve the site where it was harvested.

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