Monday, March 3, 2008

Will there be enough of the Colorado River by the time it gets to Texas?

Austin-American Statesmen (Texas): The news from around the nation has been grim: Lake Mead, the reservoir that sustains Phoenix and Las Vegas, could dry up in the next 13 years. Lake Lanier, Atlanta's main source of drinking water, is perilously low, and there is no end in sight for the drought that has seized the Southeast.

Could Central Texas find itself in a similar situation? The Lower Colorado River Authority says no. But some of the factors that have caused water crises in Arizona and Georgia — rampant growth, exceptional drought, increasing reliance on water from lakes and rivers — are at play here.

…The LCRA, like all river authorities, uses complicated modeling algorithms to predict river flow during drought. Those water availability models, or WAMs as they are known in hydrological parlance, determine how much water the river authority can commit to one of the fastest-growing regions of Texas.

The forecasts are not foolproof. For one, they're based on a benchmark barely a half-century old: the seven-year drought Texas experienced in the 1950s. For another, they typically don't take into account long-term predictions of climate change. Finally, the calculations might be skewed by a policy of selling as much water as possible. Though the LCRA insists that its water models are independent of such policy pressures, others disagree.

...Last April, the agency convened a meeting of water planners from California and Arizona, as well as from El Paso, to talk about drought preparedness. "Those eastern states are used to a wetter climate," said Mark Jordan, the LCRA's river operations manager. During hard times in the West, river managers secure more water for firm customers by systematically cutting off "interruptible" users, who pay less because their water supply is not guaranteed. On the Lower Colorado, these are chiefly rice farmers near the Gulf Coast.

…Computer simulations of various rainfall scenarios show that the LCRA could supply its water customers even in a drought as bad as the one that plagued Texas in the 1950s, says James Kowis, the agency's manager of water supply planning. The problem is, Central Texas might be in for far worse droughts.

…A drought that hit Texas from 1856 to 1865 was more severe, said Richard Seager, a senior research scientist at Columbia University's Lamont-Doherty Earth Observatory.

Last year, Seager co-wrote an article for Science magazine predicting that the levels of aridity seen in the Dust Bowl and 1950s droughts "will become the new climatology of the American Southwest." The wet spells that allow river systems to recover from drought will grow shorter, he said, thus giving the lie to all water models based on 20th century data. "There's going to be a new mean climate," Seager said….

View of Austin, Texas, from Town Lake, which is a section of the Colorado River created by the Longhorn Dam, "Arvindn," Wikimedia Commons

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