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Digging Deep for AnswersEven if there were no such thing as global warming, the changing demographics of the West require a reassessment of water. The populations of Arizona and Nevada are expected to double in the next 30 years. To varying extents, each state considers groundwater as its ultimate fallback supply perhaps in error. Dettinger is among a growing number of researchers arguing that scientists need to take stock of the underground aquifers and springs socked away under mountains and desert floors that count as the West's strategic reserve of water.  
In recent decades, geochemists, hydrologists, and scientists in other fields of earth science have devised new ways to characterize aquifers. Most significantly they can tell more easily than before how long it took water to leach down into them, which indicates where the water came from. Unfortunately, the evidence suggests that groundwater stores are much more dependent on the West s dwindling supplies of snowmelt than previously thought. This important source will have a diminishing capacity to replenish underground stores of water. That apparent reality may foil the plans of a city like Las Vegas, which gets 90 percent of its water from Lake Mead. Even before Barnett and Pierce's study, the city saw plenty of reasons to adopt strong conservation measures and diversify its water portfolio. However, the city's exploration of aquifers to its north might put it on a course for conflict with other Nevada communities that currently rely on wells. 
If there is any bright spot in an otherwise dire groundwater situation, Dettinger notes, it's that the technology to reveal the existence of a problem is available now. Even if urban planning and agriculture can be said to have lagged behind the reality of climate change, advances in science have allowed scientists enough observational and predictive ability to define the problems it could create. The tiny streamflow gauges with which Dettinger and Cayan monitor Sierra rivers cost $600 each, a significant savings from the $12,000 units once used. Back at Scripps, Barnett and Pierce can tap into supercomputing power that doubles in capacity every few years. Barnett and Pierce point out that although there is a 50 percent chance that Lake Mead won't go dry by the time today's kindergarteners start college, they've given water districts more than a decade to develop contingency plans if it does. "I have every reason to believe people will be living happy and productive lives in the Southwest in 50 years but we'll be using water in a different way," said Pierce. "We'll need to get on the path toward that sooner rather than later." |
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