There's Plenty Of Water In The Desert--For Those Who Know How To Grab It.
By Kay Sather
AUGUST 24, 1998: IT WAS A situation that may have made the Tucson Water employee a bit nervous.
As he approached the meter, a tall, long-haired and bushy-bearded man appeared from an overgrown corner of the yard.
"We think it isn't working right," the city employee explained quickly. "I'm just here to test it."
The tall man broke into a grin, instantly dissolving any possibility that his unpruned appearance belonged to the kind of guy who might, say, mail out dangerous packages from a cabin in the woods. He was definitely more the friendly farmer type.
"So are you saying," he asked, "that my meter isn't measuring a normal water flow to my house?"
"That's probably because with all the rain we've had lately, we haven't needed to use much."
He should have been able to say Well, duh. El Niño had just dumped so much rain on this city that every gringo in town learned to say at least two words of Spanish. But with all that free water, most Tucsonans continued to pay to have their water pumped up as usual from deep underground, not expecting it to make much of a dent in their water bill.
BRAD LANCASTER, THE homeowner in this story, is one of a growing number of desert dwellers who've begun to look at rainwater as a resource instead of a nuisance to be sent down to the streets. His water bill (for himself and his brother) actually read "0 gallons used" for two out of the previous four months. For each of the other two months, it read "748 gallons"--100 cubic feet, the water company's smallest measured unit. In other words, it took two months for their water use to reach that minimum each time.
Sitting on his porch, surrounded by trees and gardens, Lancaster dismisses any belief that he's achieved some kind of miracle.
"It's mostly common sense," he says, citing the relevant figures off the top of his head: An average Tucson family of three uses 120,000 gallons of water a year, with about half of that going to outdoor use for landscaping, gardening, washing the car. Though rainfall can vary quite a bit from year to year, a quarter-acre lot will receive, on average, 67,000 gallons of water annually--more than enough to satisfy those exterior needs if the rainwater is kept on site. And it doesn't have to be complicated or expensive to do so.
"People think that to harvest water you have to have cisterns," he says, "but you don't. It's easier to store water in the soil. You can exceed your outdoor needs with nothing more than earthworks."
Perhaps the simplest example of Lancaster's "earthworks" is a vegetable plot on the north side of the house which receives rainwater directly from an unguttered roof surface. The garden has been dug low so that the slope carries the runoff down into it, away from the house. Shadecloth stretched overhead from the house to the garage-turned-workshop cuts down on evaporation from the area and shields people, too, from the harsh sun.
Both the house and the workshop are lower than the street, and rainstorms bring gutter flow onto the property through what used to be the driveway opening. Instead of seeing this as a potential flooding problem, Lancaster uses the water to his advantage. By placing a crescent-shaped mound of earth strategically across its path, he has constructed a swale--an area where water is slowed down to allow infiltration and plant uptake. Even in the desert, many trees and other perennials need nothing more than this occasional deep watering.
At another opening from the street, water is captured in a french drain--a gravel-filled trench that secretly holds water while allowing unsuspecting humans to walk safely (and dryly) on its surface. As inconspicuous as a french drain may be, it's remarkable to see one in action. One Green Valley resident dug a "french trench" across a slope where water from her neighbor's yard was flowing into her driveway. A fill of 3/4-inch gravel concealed her work, and now when it rains, the rivulet of water from next door seems to magically disappear into the earth. Of course, the water hasn't vanished. The thriving vegetation at the spot has obviously found it.
Water-harvesting techniques often yield this double benefit--solving a problem such as erosion while conserving a resource. Lancaster recently saw a chance to split the benefits with a next-door neighbor who came to him because his foundation was being "eaten away" by runaway storm water. In exchange for installing gutters to solve the problem, Lancaster got to divert the water onto his own property.
It's easy to safeguard against flooding, he says, by following a few basic principles. "Design your system to harvest water, but don't destroy any natural drainage. And always have an emergency overflow to the street." Swales should not be built to collect water near the house; he says a 10-foot distance is safe.
DOESN'T ALL THIS water hoarding create prime real estate for mosquitoes?
Not with enough roots in the soil to draw in the water. And not with liberal use of the magic ingredient: mulch. By holding onto water, mulch prevents it from puddling or causing erosion while keeping it in the soil. The trees that shade his porch and yard are testimony to the effectiveness of mulching, Lancaster says.
"When we bought the house three years ago, all the trees were on the verge of dying," he says. Using "anything we could find that was free," including palm fronds, bark, straw, aged manure, and even rocks, Lancaster and his brother covered the soil around the trees, creating a layer of mulch a foot thick. "Then we watered everything really well. Once." With no additional water other than rainfall, the trees--planted in the '60s--not only recovered but doubled in size.
Laying down mulch starts a cycle that eventually takes care of itself. By retaining water it improves the soil, encouraging plant growth that contributes more mulch in the form of leaf drop or its own mass at the end of the season, further enriching the soil and increasing its ability to hold water. Planted areas, where water is needed, should be mulched and dug lower than walkways or other surfaces where water is unwanted. For Lancaster, every planted area is a sunken mulch basin--a water-harvesting system.
Unlike trees, vegetables and other garden annuals grown in the desert need water between rain events. So do people. This is where cisterns come in.
The largest of Lancaster's cisterns is a 1,200-gallon concrete tank he had built by a local septic tank company. It sits on a mound of earth near the house, higher than the rest of the property but lower than the roof that feeds it. Kids can climb onto it, but they can't fall in because the top is a concrete slab and the cistern has only three small openings: one where the downspout enters, one at the spigot, and one for overflow. The whole setup has no moving parts and requires no maintenance. Algae growth isn't a problem, since the cistern is closed off to light, and mosquitoes don't make it past the screen that covers the downspout opening. But the initial investment of $600 was considerable.
Lancaster says that more than one observer, on hearing this figure, has pointed out that the tank could be filled with groundwater for a few pennies. But for him and for others who capture rainwater, it's not primarily about saving money on water bills. It's about conserving Tucson's groundwater. It's about sustainability, water quality and realistic planning for the future. It's about saving our last remaining riparian areas, which (like the Santa Cruz River decades ago) are dying as the water table drops. And it can take the guilt out of desert gardening.
Besides, cisterns don't have to be expensive. To store runoff from his workshop roof, Lancaster built a cistern of several 55-gallon drums, connecting them with pipe so they function as one large tank. The drums come with 2-inch threaded holes that make the plumbing easy, and they're available from local bakeries for $3 to $5 each. The bricks and planks needed to support and elevate the system are easily salvaged.
Step-by-step instructions for building another inexpensive cistern are available from the Arizona Department of Water Resources. This 550-gallon cylindrical tank, designed by local builder Dan Dorsey, uses materials that can be salvaged or purchased at a hardware store for about $65--field fencing, plastic sheeting, and chipboard or old carpet. Dorsey uses this cistern himself, along with two others he built from wood and steel strapping (the kind used on shipping crates). Large volumes of water can exert tremendous pressure on the sides of a tank--7 1/2 to 8 1/2 pounds per gallon--so it's probably best not to experiment with your own design unless you have some idea of the physics involved.
Dorsey echoes Lancaster's message about earthworks. "All you really need is a $3 shovel," he says. His home sits down-slope from the alley behind him. Before he bought the property, water cut through the backyard via a ditch it had carved with erosive force. The Realtor was apologetic. As a result of the water "problem," Dorsey was able to negotiate a better price on the house. And now a series of swales, each emptying into the next when it fills, manage the flow and capture water for fruit trees, edible greens, amaranth, and other crops.
HOMEBUILDER AND WATER harvester Dave Taggett isn't especially interested in fruit trees or vegetables. But his passion for flowers is dramatically obvious to anyone passing by his yard.
He nourishes them with rainwater stored in a cistern made from a section of silvery, spiral-ribbed storm-sewer culvert. The culvert comes in three, four, and five-foot diameters, and really isn't that expensive--$15-$25 per foot plus cutting and delivery charges. He orders a 10- or 12-foot section, upends it into a bed of cement with the necessary plumbing, and runs the gutter downspout into the top. The column has a space-age elegance, and provides plenty of water pressure--"as much as you'd get from a faucet, maybe more," he says, opening the spigot full-force into a bucket to demonstrate.
Taggett has a strong sense of water ethics.
"I don't need a house this big," he says, glancing at his well-built, roomy home. "And I don't need all these little guys." He fingers an orange poppy with an affection that almost makes you question his statement. "I'm not going to take the water away from someone else."
For Taggett, Dorsey, Lancaster, and perhaps for water harvesters in general, living by a desert water ethic seems to be an adventure rather than a dreary or difficult moral obligation. Taggett tells the story of a young couple who pulled up to his curb one day in a yuppie-model car and called him over to talk. Taggett didn't remember the man, but the man knew Taggett.
"You got me into collecting my rainwater," the man said, "and I wanted to thank you."
"Yes, thanks," said the woman, rolling her eyes.
Taggett caught the gesture. "Let me guess. He's out in the rain at 3 a.m., checking the tank in his underwear."
"Exactly," the woman replied.
Taggett now builds rainwater storage systems (along with other earth-friendly, handicap-sensitive and energy-efficient amenities) into all of his homes. By choice, he no longer builds conventional houses. "It would be going backward, and I have no desire to do that."
THE DECISION TO collect the rainwater that falls on one's yard or rooftops may be a solitary one. But many properties, such as those of Lancaster and Dorsey, receive water from rain that has fallen elsewhere. What one does--or doesn't do--with rainwater inevitably affects someone else on the watershed.
Aren't water harvesters simply "stealing" water from their neighbors? Aren't they, ultimately, robbing the aquifer they're trying to protect?
Probably not significantly. Most of the water that falls on Tucson residences never reaches the underground reservoir they draw from. What doesn't immediately evaporate will flow into city streets, storm sewers, washes, and finally into the Rillito and Santa Cruz river beds. More than half of this flow infiltrates the streambeds, with about 90 percent of the infiltrated water eventually reaching the aquifer. But much of the infiltration occurs north of Tucson, contributing nothing to our central well field, where the water deficit is growing most rapidly.
Home-harvesting would have no effect on the volume of mountainfront seepage, a very important form of natural recharge for the Tucson Basin. And, unfortunately, some of the water in our aquifer will never be naturally replenished--ancient layers that lie under impermeable rock, for example, or vast areas of soaked clay that will collapse (subside) and lose permeability once drained.
And those neighbors may actually benefit from upslope harvesting. What's left in the ground after the water harvester's gardens have had their fill will continue to travel subsurface, protected from evaporation.
That's important, since evaporation rates for desert climates are high. In the Sonoran Desert, where 8 to 16 inches of rain may fall in a year, the evaporation rate may be 100 or more inches per year. One UA study of the area surrounding the San Pedro River concluded that a full 95 percent of the rain that falls there evaporates. Getting rainwater into the soil or into a closed tank as soon as possible after it falls is clearly the most efficient, least wasteful way to obtain water in the desert. When this rainwater is used instead of groundwater, it's making a very real contribution to the water supply. Everyone benefits.
PRESENTLY, WITH GROUNDWATER still supplying the city's needs, few Tucsonans are worried about losing rainwater to their upslope neighbors. Most developers, engineers and architects are more concerned with avoiding flooding than with the benefits of keeping water on site.
Barbara Rose would like to see this change. Rose lives on 20 acres in the Tucson Mountains and receives runoff from about 30 acres of watershed on the east side of the ridge above her home.
"I get about 15 million gallons of water a year moving across my land," she says. "I currently harvest 900,000 on the acre around the house." Rose uses techniques already mentioned: swales, french drains, basins, and cisterns. Her several tanks include a rammed-earth cistern that she designed and built with local rammed-earth specialist Quentin Branch. She also uses gabions--cages of rock--as porous mini-dams to slow the flow of her natural drainages and to check erosion of the hillside.
But when looking at the plans for a new development across the road, Rose realized it was the water she (and her neighbors) did not harvest that would affect the project's design--and ultimately the neighborhood. The engineers, using the conventional approach to flood control, had designed a cement-walled channel to contain the runoff from her watershed and direct it past the development. Harvesting techniques used higher on the watershed could eliminate the need for the channel, leaving that strip of desert undisturbed to serve as a buffer zone.
Rose has seen a growing interest in water harvesting on the part of professional engineers, architects and planners. "Planning developments that benefit from rainwater use on site can reduce the costs of typical grading and channeling, as well as add to the real value of the development for future residents," she says.
With funding provided by PRO Neighborhoods, Pima County, and the Town of Marana, Rose is organizing a series of workshops that will include training in water harvesting for the professionals involved in shaping the imminent development of her area, as well as for homeowners. She hopes the classes will foster an understanding that existing washes, and the desert vegetation associated with them, are at the heart of sustainability for the Tucson Basin, and should be preserved as functional.
IN A DESERT, SAYS Brad Lancaster, "there should be no such thing as a flood. The Flood of '83 should have been the Bountiful Harvest of '83."
He believes city streets should drain into tree wells instead of the storm sewer. A study in Davis, California, showed that the planting of roadside trees in one neighborhood reduced the ambient temperature by an astounding 10 degrees. Such studies suggest that downtown Tucson might still avoid becoming a "heat island" if simple water harvesting for vegetation and trees was used consistently. Dissolved pollutants from asphalt and cars may not be safe to feed to an edible garden, but native trees and even fruit trees can handle them just fine, Lancaster says.
Unless it picks up surface pollutants, rainwater is in a class by itself when it comes to what we call "quality." Not only is it missing the high--and rising--concentration of salts found in groundwater, it also contains nitrogen created by lightning. Anyone who's observed the joyous green response of a garden to a good rain, as compared to the results of even a generous dousing with groundwater, knows that from a plant's perspective the difference in composition is real. Evaporative coolers can also benefit. When his gardens permit, Taggett runs rainwater through his cooler for awhile, flushing out the salts and postponing maintenance.
Rainwater is actually better for people, too. According to the UA Department of Atmospheric Sciences, it's 100 to 1,000 times purer than our groundwater. Though roof surfaces of asphalt or lead paint can contaminate it, metal, slate, mission tile, and even reflective-paint-coated surfaces (if recoated yearly) are safe for collecting drinking water. And a few weeks of cistern storage can actually improve the water. Microorganisms associated with the organic matter at the bottom of the tank work to purify it. To avoid disturbing this settled organic material, cisterns should be designed with the spigot an inch or two above the floor.
Rainwater is the only source of drinking water in many parts of the world, including some areas of Mount Lemmon. Anyone who has doubts about the safety of rainwater can have it tested, for a fee. (Analytical laboratories are listed in the Yellow Pages.)
It might be tempting to take a look at the Central Arizona Project from a water harvester's point of view, and ask whether we could have done without it. But the taxpayer dollars have already been spent, the acres of desert paved. However, consumers who object to the prospect of CAP on tap might be comforted to know they have an alternate source for drinking water. More importantly, anyone who owns a surface that rain falls on has the power to reduce, if not eliminate, their dependence on the city water supply--not a bad idea, given the uncertainty of Tucson's water future.
Our summer monsoon season is drawing to a close. Probably, most of the rainwater that fell on your roof and yard escaped to the street, turning it into an undriveable river while leaving your landscape high and almost dry. But the winter rains are only a few months away. You should have enough time to install those gutters and hook up your cistern of choice. Or just grab a shovel and start moving dirt around. It might be the most radical political act you'll ever commit.
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