Monday, October 22, 2007

Climate: Is The Future Drying Up? (The American West)

The following are some excerpts from a recent article in the NY Times online magazine. The subject is the problem of water supply in the American West. It is, I think an excellent article, quite lengthy, but well worth reading. A link to the article is here. My comments are in italics.
Draining The 100-foot-high bathtub ring left by the dwindling waters of Lake Mead, behind Hoover Dam.

The Future Is Drying Up
Published: October 21, 2007
"But recent studies of tree rings, in which academics drill core samples from the oldest Ponderosa pines or Douglas firs they can find in order to determine moisture levels hundreds of years ago, indicate that the dry times of the 1950s were mild and brief compared with other historical droughts. The latest research effort, published in the journal Geophysical Research Letters in late May, identified the existence of an epochal Southwestern megadrought that, if it recurred, would prove calamitous."

An even darker possibility is that a Western drought caused by climatic variation and a drought caused by global warming could arrive at the same time. Or perhaps they already have.

Climatologists seem to agree that global warming means the earth will, on average, get wetter. According to Richard Seager, a scientist at Columbia University’s Lamont Doherty Earth Observatory who published a study on the Southwest last spring, more rain and snow will fall in those regions closer to the poles and more precipitation is likely to fall during sporadic, intense storms rather than from smaller, more frequent storms. But many subtropical regions closer to the equator will dry out.

Mulroy is not gambling the entire future of Las Vegas on this project. One catchphrase of the water trade is that water flows uphill toward money, which is another way of saying that a city with ample funds can, at least theoretically, augment its supplies indefinitely. In a tight water market like that of the West, this isn’t an absolute truth, but in many instances money can move rivers.

Even if drought conditions ease over the next year or two, several people I spoke with think the odds are greater that Lake Powell, the 27-million-acre-foot reservoir that supplies Lake Mead, will drop to unusable levels before it ever fills again. Mulroy didn’t immediately dismiss the possibility; she is certain that the reduced circumstances of the two big Western reservoirs are tied to global warming and that Las Vegas is this country’s first victim of climate change. An empty Lake Mead, she began, would mean there is nothing in Lake Powell.

This is an old prophecy, dating back more than a century to one of the original American explorers of the West, John Wesley Powell, who doubted the territory could support large populations and intense development. (Powell presciently argued that river basins, not arbitrary mapmakers, should determine the boundaries of the Western states, in order to avoid inevitable conflicts over water.) An earlier explorer, J. C. Ives, visited the present location of Hoover Dam, between Arizona and Nevada, in 1857. The desiccated landscape was “valueless,” Ives reported. “There is nothing there to do but leave.”

Indeed, any conversations about the one will in short order expand to include the other, Binney went on to say. Many water managers have known this for a while. The two problems — water and energy — are so intimately linked as to make it exceedingly difficult to tackle one without the other. It isn’t just the matter of growing corn for ethanol, which is already straining water supplies. The less water in our rivers, for instance, the less hydropower our dams produce. The further the water tables sink, the more power it takes to pump water up. The more we depend on coal and nuclear power plants, which require huge amounts of water for cooling, the larger the burden we place on supplies.

Meanwhile, it is a perverse side effect of global warming that we may have to emit large volumes of carbon dioxide to obtain the clean water that is becoming scarcer because of the carbon dioxide we’ve already put into the atmosphere. A dry region that turns to desalination, for example, would need vast amounts of energy (and money) to purify its water. While wind-powered desalination could perhaps meet this challenge — such a plant was recently built outside Perth, Australia — it isn’t clear that coastal residents in, say, California would welcome such projects. Unclear, too, is how dumping the brine that is a by-product of the process back into the ocean would affect ecosystems.

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