Rincon Institute
Ecology in Focus - The Essence of Life: Water in the Sonoran Desert

For the past 2 months or so, the discussion around the Rincon Institute water cooler for has been about the lack of rain and whether or not there really is enough water to sustain both the growing human settlement of Tucson and the biodiversity of the Sonoran Desert. Our partners at Pima County, Tucson Water, and the ranchers and farmers with whom we work are all anxiously scanning the horizon for what one Arizona rancher calls, “pennies from heaven.”

pools of water
Photo By: Michelle Berry
Headline after headline in the Arizona Daily Star proclaim the prolonged and profound drought gripping our region. Living in such an arid region as the desert southwest (where we receive an average of 12 inches of rain per year in the lower elevations), it is easy to forget that even life here requires H2O. But it seems that during a drought, especially one in which the winter rains simply do not come, we pay a bit more attention to water than we usually do when it is more plentiful. So this month, in our Ecology in Focus column, we thought we’d offer some thoughts about the essence of life in the desert. The majority of the earth’s water supply is found in the oceans and is too salty for much of earth’s plant and animal life to utilize. In fact, if the world’s entire water supply were represented by 1 gallon, the supply usable by human beings (and much of the planet’s life forms) would be only one drop. Of that drop, the available amounts are stored in the ground as groundwater and in freshwater lakes and rivers (the remaining “fresh water” is trapped in ice caps and glaciers). In Tucson, we rely both on the pumping of groundwater as well as the long transportation of the Colorado River for our water. Every time we use water we draw down the aquifer (and the water table). As the water table drops, the native plants that rely on a high water table for survival become more vulnerable.

Velvet Mesquites, for example, have a root system that allows them to reach deep into the earth for groundwater – this system purportedly helps the trees to withstand drought. However, 90% of the mesquite’s root system is actually in the upper 3 feet of soil, and so the lower the water table drops, the more difficult it is for the mesquite to survive. And the more water we all use without being aware of our actions, the harder it is for all living things in the desert to survive. Mesquites, like so many plant species adapted to this arid place, provide shade, help clean the air, and cool off the heat-filled desert. Our lives are better off when these plants not only survive, but thrive. That’s why at the Rincon Institute, we believe it’s essential that we each do our part to conserve water – using it as wisely as we possible can. Every day each Tucsonan uses an average of 177 gallons of water (that adds up to about 64,000 gallons/person/year and over a quarter of million gallons of water per four-person household/year). The number of gallons used in total continues to rise in spite of Tucson’s well-known water conservation ethic. In fact, we are currently drawing water from the aquifer two-and-a-half times faster than it is replenished. That means we must do more. Here are some ideas for water conservation in our homes – the places where we all consume the most water and have the biggest opportunity to do our part.


  • Take shorter showers – it is estimated that in homes with older showerheads, that run 5 gallons of water/minute, an average shower uses 50 gallons.
  • Turn off the water when you brush your teeth – a normal sink faucet runs about 3.5 gallons/minute.
  • Install low-flow fixtures in your home.
  • Run only FULL loads in your dishwasher and/or washing machine.
  • Set your washing machine on the lowest load level to use only the amount of water you need.
  • Plant native desert plants whose genetics enable them to withstand the cyclic droughts.
  • Install a rain harvesting system at your home in order to capture rain water for your landscaping.


Graph from Water Plan: 2000-2050, 2-7
Graph from Water Plan: 2000-2050, 2-7
Not long ago someone said to us that “domestic” water use is not the cause of water troubles in Tucson, but that instead we should be “blaming” agriculture. While it’s true that agriculture uses the lion’s share of water in Arizona, we can still each do our part. After all, a bucketful of water begins with a single drop. In 1962, Rachel Carson wrote a little book called Silent Spring. Carson explained to her readers, “Of all our natural resources water has become the most precious...[but] has become the victim of [man’s] indifference.” She could well have been referring to the desert southwest in 2006. The current drought is not necessarily within our control, but our indifference is. In these dry, dry days, the Rincon Institute hopes you’ll think often of your water use and when you do strive to conserve so that life, both animal and plant, in the Sonoran Desert can continue.

Sources: Carson Rachel. Silent Spring. New York: Houghton Mifflin, 1962.
Phillips, Steven, ed. A Natural History of the Sonoran Desert. Tucson: Arizona Sonora Desert Museum, 2000.
Tucson Water. Water Plan: 2000-2050. Tucson, 2004.
For Information on how to Use Water Wisely, contact Tucson Water - www.ci.tucson.az.us/water/
For More Information on Rain Water Harvesting please contact the Water Resources Research Center at the University of Arizona - www.ag.arizona.edu/AZWATER/