A natural source of water

Homeowners can turn their yards into oases by capturing rainwater and recycling household water, explained Brad Lancaster, author of Rainwater Harvesting for Drylands.

He describes harvesting principles that allow plants to thrive and thus cool the area around homes, a form of climate control that becomes more crucial with temperatures rising and populations growing.

“We’re truly desertifying our so-called desert,” Lancaster said during a talk this year at The University of Arizona’s Water Resources Research Center. “Here’s where the rivers are today,” he added, showing a slide of a Tucson street flooded by monsoon rains.

Paved streets, concretized river banks, and hard bare soil all channel water away before it can soak into the ground—sometimes whisking it out of town even before it can recharge groundwater aquifers, he noted.

A permaculturist based in Tucson, Lancaster learned some of his techniques in Zimbabwe, which has a semi-arid climate similar to that in the Southwest. There, a man he calls Mr. Phiri taught him how to “plant water before planting trees” and other lessons. These include:

• Start by observing your landscape during rains, noticing how water moves and collects. Then revise after noticing what does and doesn’t work.
• Start at the top of your “watershed,” which on a residential lot may be a roof. Capture and/ordirect gutter water toward plants or into a storage tank.
• Start small. Use simple strategies that slow and spread the flow of water across the land, giving it time to seep down into soil.
• Maximize ground cover, especially living ground cover. Plants and mulch help soils quickly soak up water, so it won’t be available for mosquito breeding.

“If nothing else, raise your pathways and patios and sink your planting areas,” Lancaster suggested. That way plants will receive some of the water running off the impermeable surfaces.

During an early September tour of his yard, he pointed out a 1,200 gallon cistern— now full—that stores water channeled from his roof (Figure 1). A spigot on the side yields some of its contents with a turn of the faucet. A driveway and a strategically sliced curb pull in some of the street’s flow during monsoon rains, where native plants benefit from the spillover. Corrugated zinc on the roof of his workshop drains water in rivulets into an area sprouting orange and fig trees.

The thriving saplings also receive water every time Lancaster washes a load of clothes. Recycled water draining from showers, washing machines, and other household pipes is known as greywater.

Arizona has begun encouraging residents to use greywater for landscaping, as long as they avoid draining from kitchen sinks or, of course, toilets. In 2007, the state will start providing up to $1,000 in tax credits per household to help reimburse residents who set up greywater-harvesting systems.

When employing greywater, Lancaster recommends using liquid detergents rather than powders, which use salt as filler. Also, unlike rainwater, greywater should not be stored in a tank. Lancaster encourages people to deposit it directly into mulched and vegetated soil.

Water harvesting can make a crucial difference when living in any desert. Lancaster’s mentor, Mr. Phiri, became a role model for his village in Zimbabwe after turning a barren wasteland into a productive farm over the years.

“There are other people in his village literally dying of thirst in drought years, and he is raising fish,” Lancaster said. “And they could be doing the same.”

More information about the tax credit program, suitable detergents for greywater systems, and Lancaster’s book can be found at his website: http://www.harvestingrainwater.com.