Ideas for Passive Rainwater Harvesting

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At first glance Beverly and Ron Wilson’s front yard looks like a typical desert landscape.
But upon closer inspection, you’ll see the swaths of rock, gravel, dirt mounds and boulders have been carefully and precisely placed to serve an important purpose.
With the monsoon season about to arrive, the Wilsons are well positioned to capture rainwater and retain it on their property to irrigate their trees and plants, without the aid of any water barrels.
Instead, the couple prefers to practice passive rainwater harvesting, which they say anyone can easily and cheaply do.
“There are so many things you can do that will make a difference to both rainwater and groundwater,” Beverly said.
The process of developing a passive rainwater system at their one-acre property on South Bannock Avenue, Sierra Vista, has been ongoing for the Wilsons, and they encourage first timers to tackle their own projects one step at a time.
That’s something Tim Cervantes, administrative director of The Cochise Water Project, a non-profit whose sole purpose is to help prevent water being drawn from the aquifer, agrees with.
“You don’t have to spend a lot of money or take on the whole yard, just do it a little section at a time,” he said. “Start with maybe one tree and create a saturation zone.”
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This, he adds, can be achieved by simply raking existing gravel to form a basin around the tree, thereby stopping rainwater from flowing away and evaporating.
When the Wilsons observed excessive amounts of rainwater flowing from the metal roof on their home onto the patio they decided to turn it to their advantage.
Rather than see the water wasted, they installed underground drains in the patio to capture it. That water now flows into a nearby pit that irrigates a number of mesquite trees.
They also ripped out grassed areas planted by their home’s previous owners and replaced it with astro turf.
But the biggest project was tackling and replacing the large areas of concrete rock and underlying plastic – a common feature of older homes like theirs.
“We took out hundreds of tons of concrete rock and plastic,” recalls Beverly, the Director of Cochise County’s Planning Division. “We got rid of the plastic and replaced the rock with decomposed granite.”
Water loving juniper bushes and roses were switched out for low water, native plants, many of which were placed in areas that directly capture rainfall, such as along the roofline of the house.
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The yard was subtly graded to direct rainwater flow into swales (rock filled trenches) throughout the property. The water helps irrigate bordering plants and is retained in basins, instead of flowing out onto the street.
The area is also dotted with berms (dirt removed from the swales and formed into mounds) that are strategically placed to again direct water flow for irrigation.
As a landscape architect, Beverly made a point of learning about passive rainwater harvesting, but she believes anyone can do it successfully.
‘You have to understand that the whole passive thing is about shaping dirt,” she said. “Just start simply with a basin around a tree and start by looking at where the water can flow to get to that basin.
“It’s also a matter of being observant. When you see the rainwater come down, look at where the natural swales might be and the different grades. Look at where the water is really running and then how it can be directed.”
And removing plastic from under your yard’s gravel can also make an impact, adds Cervantes.
“Find out if you have plastic and if potentially you can pull it out, even just a bit at a time. All the plastic is doing is preventing the water from soaking back into the ground,” he said.
Those worried about being inundated with weeds should not be, said Beverly.
“We get a lot of dust blowing here, especially this past spring, and it settles on top of the plastic, fills in the rock and creates its own earth,” she said. “The weeds are going to grow anyway.
“Passive rainwater harvesting isn’t hard to do and you can still have trees and plants. It’s just about not taking the water out.”
For more information on rainwater harvesting and other ways to save water visit
www.thecochisewaterproject.com