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
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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