GV?Gardeners: Nature Conservancy harvests rainwater

It may be hard to believe, but it takes only one inch of rainfall on a 1,000-square-foot roof to collect 600 gallons of water.

Additionally, because our “engineered lots” are designed to take rainwater off to the street, 80 percent will leave the property. Thereafter, it travels to and through washes, and crashes down arroyos to form creeks and streams.

These then empty into the river heading toward Tucson. Eventually, the water that started in your yard is north of the valley, spread onto the desert floor where most evaporates.

Tucson Chapter of The Nature Conservancy has developed a public rainwater harvesting demonstration site at its 1510 E. Fort Lowell Road location. In keeping with their conservation mission, members have cooperated with numerous local university and business partners, and with support from local and federal government agencies, to showcase a variety of techniques that home and business owners can utilize in the desert environment.

This project promotes sustainability and conservation using time-honored and technologically enhanced methods for harvesting the rain. Methods range from simple, quick fixes to sophisticated levels, encouraging everyone to try rainwater harvesting, regardless of budget or time constraints.

Rainwater harvesting captures precipitation and uses it as close as possible to where it falls. This is using rainwater supplements that would otherwise be drawn from the aquifer and diminish our groundwater supply.

Remember that rainwater is free, so collecting can reduce the cost of irrigating your landscape, often 30 percent-50 percent of residential water bills! Naturally occurring nutrients accumulated in the rainfall is an added benefit for the plants.

Previously discussed in this column has been the simplicity of building small berms at plants and basins around trees to slow rainwater movement, giving it a longer time to soak in. These methods are well demonstrated at the Conservancy site.

An interesting method shown is the building of rock-lined basins in the yard where water from the roofs is directed.

Water stands in the basin for about 24 hours, slowly soaking into the earth. Plants, shrubs, grasses and trees have been planted and are flourishing in these basins.

Among the plantings are desert willow, mesquite and palo verde trees; creosote, fern acacia, autumn sage, globe mallow, limberbush, penstemon, verbena, desert marigold, salt bush, and native bunch grasses such as Arizona cottontop.

At the Conservancy demonstration site are two cisterns collecting rainwater from smaller building rooftops. There is a 300-gallon polyethylene tank designed by a University of Arizona graduate student and a 564-gallon corrugated metal example. All rainwater is used for irrigation only.

Free, docent-led tours are given at 8 a.m. and last about one hour.

Remaining dates this summer are July 25, Aug. 5, Aug. 14, Aug. 16, and Aug. 22. Reservations are unnecessary; just meet

at the front entrance (northeast corner) of the Nature Conservancy building. It is a thought-provoking tour, and the simplistic ideas used will amaze.

For more in-depth data on the subject, a book called “Rainwater Harvesting for Drylands” by Brad Lancaster is recommended. He also has an informative Web site: www.harvestingrainwater.com.

The grounds around The Nature Conservancy site display many native Arizona and Sonoran Desert plants. Stop at the office and pick up a single-page guide to plant varieties and locations.

Started in 2000, the yard is maturing and will become more beautiful with age. There is also a rainwater harvesting sitemap and guide, so you can do a self-conducted tour when in the area. As it states in the brochure, “You are invited to visit, sit and enjoy anytime.”

Mary Kidnocker is a Master Gardener who writes frequently on the subject from a local perspective. Her columns are featured Sundays. She is president of The Green Valley Gardeners