Study quantifies climate change impact on U.S. Southwest water crisis

Written by Marion Davis

Thursday, 10 February 2011 02:00

A cotton field in Arizona, one of the most arid U.S. states. Photo: Flickr/Evelyn Priomos

Arizona, California, Nevada, New Mexico, and Utah will face a combined shortfall of 1,815 MAF from population and income growth, plus up to 439 MAF more from climate change – at a combined cost of as much as USD $5 trillion.

Water is already a major concern in the Southwest, where homes, businesses and farms use far more water than is produced by rain and snowfall, and groundwater reserves are shrinking.

Climate change, a new study from SEI’s U.S. Center shows, will make the Southwest’s water problems even worse, increasing the long-term shortfall by up to a quarter and adding up to $1 trillion in extra costs by 2110. Rising temperatures will drive up demand across the board, especially in agriculture, and create intense competition for dwindling resources.

Without prompt action to address this problem, the authors estimate, Arizona, California, Nevada, New Mexico, and Utah will face a combined shortfall of 1,815 million acre feet from population and income growth alone, plus 282 million to 439 million more from climate change.

The bottom line
Based on the current cost of adding reservoir capacity in California, meeting the baseline shortfall would cost $2.3 trillion, plus another $353 billion to $549 billion when you add the impact of climate change. Using a higher water price, the average cost of water delivery in 12 Southwestern municipalities, the costs rise to $4 billion for the baseline shortfall, plus an additional $623 billion to $970 billion for the impact of climate change.

And that’s if the shortfall can be made up at all. As conventional water sources dry up, the Southwest could find itself facing serious water crises in dry years, with unexpected disruptions that could devastate agriculture and affect homes and businesses as well.

“Climate change is affecting Americans in many areas; the water crisis in the Southwest is one of the clearest examples,” said Frank Ackerman, director of the Climate Economics Group at SEI-U.S. and lead author of the study. “Climate policy choices we make today are not just about exotic environments and far-future generations – they will help determine how easy or hard it is to create a sustainable water system in the most arid region of the country.”

A new way to look at the problem
The Southwest’s water troubles are well known, but this study provides new insights by using county and state-level data to offer more depth than national or regional studies, but also a “big-picture” perspective. It also looks beyond the immediate future, because, as Ackerman noted, “the choices we make now on climate change will affect our future, over a century and more.”

The authors evaluate potential ways to meet the shortfall, including water imports, desalination and additional groundwater extraction, and conclude that none can solve the problem. To avoid serious water crises, they recommend, the Southwestern states should promptly implement substantial conservation and efficiency measures as well as price increases for both urban and agricultural users. They also advise phasing out low-value crops, some of which are worth less than the water used to grow them.

Click on the title to learn more and download the report, The Last Drop: Climate Change and the Southwest Water Crisis.