Welcome to the New Normal

Welcome to the New Normal

Scripps Oceanography research suggests that climate change will require a complete rethinking of water delivery systems in the West.

That'll be step one.

April 2008


By Robert Monroe

Tim Barnett and David Pierce run computer simulations of current and future climate trends that require the processing of billions of data points and the harnessing of terabytes of computer storage.

But the latest analysis from the two climate researchers at Scripps Institution of Oceanography at UC San Diego reads more like a word problem that might be put to a grade school math class:

Lake Mead, a major source of water for desert Southwest cities such as Las Vegas and Phoenix, has 15 million acre feet of water. If one million more acre feet are taken out of the lake than are put in every year, how many years will it take for the lake to run dry?

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Like the thunderclaps that echo across southwestern deserts in summer, that question sent a rumble in February through lake-dependent metropolises when Barnett and Pierce released their analysis of the lake's potential future. While a handful of water district officials dismissed their central conclusion, most immediately took it as a cue to man their battle stations and brace for more fights in a water war that has existed almost as long as the West has been settled.

Barnett and Pierce's relatively simple computation used records from the federal Bureau of Reclamation, which manages the water supply at Lake Mead and at Lake Powell, located further north on the Colorado River. They compared the amount of water the bureau is scheduled to deliver to cities and agricultural users to the percentage that climate computer models say will probably be lost to global warming-related phenomena like increased evaporation. (An acre foot of water typically meets the needs of two households for a year.)

They found that a business-as-usual scenario could see Lake Mead effectively drained in little more than a decade and unable to generate power at Hoover Dam even sooner. Barnett and Pierce emphasized in their research paper and in the media interviews that followed its release that they used middle-of-the-road climate change estimates taken from a broad range of studies.

"If we stopped overdrafting, that would be a start, but that leaves the whole Colorado system still right on the edge of being unstable," Barnett said.

Dramatic as it was, Barnett and Pierce's work was merely the exclamation point on a statement about the West's water future that Scripps climate researchers have been writing and rewriting for several years. From a series of observational studies beginning in the 1990s describing shifts toward earlier spring onsets and a rising proportion of precipitation falling as rain rather than snow to projections of rising sea level and diminished spring snowpack, the scientists have described a system in crisis, one that will require fundamental changes immediately:

  • Aging levees, endangered species, and earlier snowmelts are a few of the factors threatening the Sacramento delta from which Southern California draws most of its water. A repeat of episodes during which drought caused Pacific Ocean seawater to flow as far inland as Sacramento city limits lingers as a possibility.
  • Groundwater, long considered the last bastion of water supply when lakes and other reservoirs begin to dry, turns out to be more dependent on fleeting sources such as snowpack. As cities like Las Vegas turn to aquifers for their drinking water, it's not clear how much water they will find and how long it will last.
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Other Scripps scientists, including Mike Dettinger, a U.S. Geological Survey hydrologist based at Scripps, credit Barnett and Pierce with taking climate change out of the realm of abstraction for residents of southwestern states. Here is a climate change phenomenon playing out in proximity to millions of Americans that they will watch year by year. The study could also lead water resource managers - a lot often conditioned to focus on just getting their customers from one dry summer to another - to take a longer view of what they're up against. "What Tim and Dave are telling them is that this is the new normal," said Dettinger.

Next page: Sacramento Underwater


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