June 06, 2011

Water harvesting: sustainability’s newest kid on the block

This might be an answer for the parched West

By Joan Melcher

The future of water management might look a little like Kate Flax’s front yard in Tucson.  It sports a 12 x 15 x 9 ft corrugated steel “roof” for a 10,000-gallon buried cistern. Surrounded by desert plantings, the cistern fits seamlessly into the landscape.

On each side of her ranch style house are 620-gallon “Slimlines,” where water is caught from a 4,000 square foot roof and gravity-fed through underground pipes to the underground cistern. Water is pumped from there to a set of five filters that treat the water before it enters her house. Other water is directed to landscape plantings and a swimming pool.

To the side of one Slimline are a chicken coop and a vegetable garden. In the back, a small pool and Jacuzzi are worked into the rock and stone of a pretty patio. On the roof are solar collectors and a solar water heater. Soon a solar carport will be constructed on the other side of the house to power the pumps for the pool and the water system.

Flax has invested in all this, she said, because of an interest in conservation. “I like the idea of being sustainable,” she said, adding “when I was in college 40 years ago it became eminently clear to me that water was a valuable commodity. But life gets in the way. It took me 40 years to walk my talk.”

And doing that she is. Her system is now supplying all her water needs. Although Tucson has been in a drought, she’s been collecting water over several months and her underground cistern has plenty of supply.

Lincoln Perino, a consultant for Tucson’s Technician for Sustainability, which installed the system, says the payback period is long, mainly because there are few financial incentives to conserve water, even in Tucson, which has been known for years as a water-conscious city.

Water prices have been kept low in Tucson, partly due to the agriculture lobby, he noted. A water bill can be as low as $30 to $50 a month in Tucson, although the water table has been falling and those drilling wells often have to go 300 feet or more, when not long ago water was hit at 50 feet.

Solar has both state and federal tax credits, but water harvesting has yet to gain significant attention. Flax will get a $1,000 federal tax credit for her $20,000 water harvesting investment, which is also the extent of the credit for a commercial-grade system.

Tucson passed a law last year that requires that all new commercial construction get 50 percent of landscape water use from passive or active water harvesting. It also requires that all new residential stub outs for bathrooms, sink and shower and laundry rooms have a separate pipe that will allow connection for greywater.

Perino noted that so far it seems commercial developers are opting to put in xeriscape gardens, with heavy use of cacti and other drought-tolerant natives rather than trying to capture water that could be directed to trees and natives that require more moisture. He’s concerned because with growing development and more streets and asphalt, Tucson, like Phoenix, experiences the heat island effect. He said more trees and plants help to cool the environment.

Water catchment is definitely the new kid on the sustainability block, but more cities, states and countries are getting in the act. Perino noted that in Australia,  the driest continent, it’s common to see water catchment systems on structures. Texas and Hawaii have been leaders in this country.

Perino takes me to another project, this one the first water catchment project TFS designed. It’s at La Paloma Family Services and features five cisterns ranging in capacity from 600 gallons to 2,300 gallons for a total of about 5,000 gallons of storage.  The smaller tanks collect water from butterfly-designed roofs and gravity feed it to the 2,300-gallon cistern, where water is pumped to the landscape. He tells me of problems with the system here as well as at Flax’s home.

There they were deciding how to address an elevated pH level in the filtered water before allowing it into the house for drinking. A few weeks later Flax reported the pH level had been addressed and she was drinking the water, put through intensive filtering, from her cistern catchment.

At La Paloma water wasn’t getting where it needs to go, although a recent drought means there’s little in water storage. He will check back later to see what can be done. He notes that there are learning curves with the technology and TFS is committed to correcting them and learning from mistakes. Currently, water catchment pioneers continue to keep their connections to the Tucson water utility for indoor use and for landscaping, when “catched” water is depleted. Generally from 45 to 60 percent of water used residentially is for landscaping.

One TFS design maxim is to use passive technology, such as designing gravity-fed systems that require little in mechanical workings. “We try to do systems as passively as possible,” he said. “There is very low maintenance on our systems because with more maintenance, a lot more can go wrong.”

He noted that water harvesting needs to be tailored to each environment. For instance, it’s enjoying a surge in Seattle, where cisterns can be as small as 200 gallons.  When it rains nearly every day, catchment need not be large.

In contrast, Tucson typically gets around 6 inches of rains in the July and August monsoons and another 6 inches (if it’s lucky) in the winter months. Cisterns need to be quite large to hold the water over a period of time.

That’s why Flax has 10,000 gallons. “I feel very fortunate to be where I am,” she said. “I look forward to a real paradigm shift — so when I pick up the real estate section I don’t read another story on granite countertops. Instead I learn about the new green systems people have incorporated into their homes.”