The desert Southwest: Oasis or mirage?May 9, 2012 By Pete Zrioka in Earth / Environment
(Phys.org) -- The American West has a drinking problem. On farms and in cities, we are guzzling water at an alarming rate.
The water supports the populations of California, Arizona, Nevada, Utah, New Mexico, Colorado and Wyoming, providing for agriculture and cities. With a changing climate and continued population growth, increasing demand for water may make this vital resource increasingly scarce.
There are some safeguards in place against water scarcity. The reservoir Lakes Mead and Powell can provide approximately five years of average annual stream flow at full capacity for insurance against low rainfall years.
But John Sabo, an associate professor in Arizona State Universitys School of Life Sciences, believes that 50 years in the future rather than five should be the planning mark for water usage.
My take on that is were already beyond the point where we have enough insurance against the bad years, which is why a year and a half ago we started talking about water rationing before it started raining in December, says Sabo, who is also director of research development in ASUs Global Institute of Sustainability.
After dipping to a record low in 2011, Lake Mead presently sits at below half capacity, and thats with favorable rainfall and snowpack accumulating in the Rocky Mountains, which feed the Colorado.
Also, to our detriment, there is a culture dedicated to creating an oasis in the Southwests arid environment. Most of the Wests water falls in the mountains, where it slowly melts, We collect it and then spread it thin across the deserts. Moving water from wet areas to dry areas makes people feel safe, according to Sabo.
We have lawns, palm trees and lush green parks because we store water from far away to offset the arid reality of the desert, he says.
Regardless of how much our lawns guzzle, the largest use of water isnt in urban areas but in agriculture. Farming uses 77 percent of the water allocated for human use in Arizona, according to the Morrison Institute for Public Policys publication Watering the Sun Corridor.
For example, Southwestern farms produce approximately 75,000 acres of lettuce annually. As much as 55,000 acres of that is grown in Arizona, according to University of Arizona publications. Of Arizonas lettuce, 95 percent is grown in the southwestern corner, in Yuma county, which receives an average rainfall of about 3.6 inches.
People might ask, why are we growing lettuce in Arizona? questions Sabo. Well, its because its warm here in the winter and people want salads in the winter. And if you want a salad in the winter and you dont want to wait for natural salad season to come around, youve got a tradeoff, and that tradeoff is the water footprint.
The water footprint of produce isnt often taken into consideration, however.
Theres this eat local movement that has done a great job to educate people about how your decisions at the supermarket relate to your carbon footprint and climate change, says Sabo. But theres nothing like that for water, and I think there needs to be.
Since most water isnt used for cities, urban lifestyle changes arent going to do much to solve the problem. Shorter showers and eco-friendly appliances arent enough to make a significant impact on our massive water use.
Sabo proposes that the Southwest cuts its water use to 60 percent. To get there, it comes down to policy and investment in infrastructure for the future.
You would never know we had a water shortage here, says Sabo. We dont pay a lot for it, we dont expect pay a lot for it and we dont expect to have to conserve it.
David White, co-director of ASUs Decision Center for a Desert City (DCDC), says that Arizona water policy has done a good job of providing adequate supplies for the growth of the region up to this point. But environmental and demographic factors will likely require changes in that system. The DCDC uses research to inform environmental policy in times of uncertainty.
Weve been able to deliver a consistent and reliable amount of water to residents even though the amount of water that comes into our system fluctuates wildly, says White. That system has been effective over the past 100 years under a set of conditions and assumptions that may be changing due to climate change, extended and prolonged droughts, and increased demand as a result of population growth. It faces new challenges, adds White.
Home to more than half of Arizonas population, Maricopa County grew by 24 percent from 2000 to 2010, according to U.S. Census Bureau data. Additionally, Watering the Sun Corridor, projects the 2030 population of Phoenix and Tucson to exceed 7.8 million.
One way to reduce water use is through the addition of more sustainable infrastructure. According to Sabo, this would be most effective in areas of growth and expansion, such as Ahwatukee, Anthem and Sunrise.
Retrofitting historical Phoenix would be a pain in the neck, says Sabo. The idea is to build sustainable infrastructure as we build out. Reclaimed water is cheaper to add in to unbuilt suburbs than to retrofit in older cities. When the time comes for refurbishing the old potable infrastructure in the central city, then we can consider retrofitting for dual distribution of potable water for drinking and reclaimed water for landscape irrigation at home.
Such changes would help us follow Whites recommendation to stop siphoning our limited groundwater sources and live off of renewable surface water instead. Groundwater is water that is stored in underground aquifers. Although it is replenished by rainfall, we use it much faster than it can be replaced.
Groundwater supplies a bank or a backup of water, says White. But by and large its a nonrenewable source and we should try to live within our means.
Its unlikely that the Southwest would run out of water. But as temperatures rise and population swells, how we value our water supply is going to change.
Youre either going to have to pay more for it or youre going to have to pay more for your winter salad, says Sabo. Either the farms or the luxury to use water the way we do in cities is going to go.
Provided by Arizona State University
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