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Monday, September 8, 2014

Southwest may face 'megadrought'

by Traci Eatherton, WLJ Managing Editor

California’s three years of drought conditions continue across the southern half of the state, with parched soils and destructive wildfires leaving thousands of acres basically void of vegetation, and according to a new study, the state may very well be in for more of the same—for several years.

Due to global warming, scientists say, the chances of the southwestern United States experiencing a decade long drought is at least 50 percent, and the chances of a “megadrought”—one that lasts over 30 years—ranges from 20 to 50 percent over the next century.

“For the southwestern U.S., I’m not optimistic about avoiding real megadroughts,” said Toby Ault, Cornell University Assistant Professor of Earth and Atmospheric Sciences and lead author of the paper. “As we add greenhouse gases into the atmosphere—and we haven’t put the brakes on stopping this—we are weighting the dice for megadrought conditions.”

As of mid-August, most of California sits in a D4 “exceptional drought,” which is in the most severe category. Oregon, Arizona, New Mexico, Oklahoma and Texas also loiter between moderate and exceptional drought. Ault says climatologists don’t know whether the severe western and southwestern drought will continue, but he said, “With ongoing climate change, this is a glimpse of things to come. It’s a preview of our future.”

Ault said that the West and Southwest must look for mitigation strategies to cope with looming long-drought scenarios. “This will be worse than anything seen during the last 2,000 years and would pose unprecedented challenges to water resources in the region,” he said.

In computer models, while California, Arizona and New Mexico will likely face drought, the researchers show the chances for drought in parts of Washington, Montana and Idaho may decrease.

Beyond the United States, southern Africa, Australia and the Amazon basin are also vulnerable to the possibility of a megadrought.

With increases in temperatures, drought severity will likely worsen, “implying that our results should be viewed as conservative,” the study reports.

“These results help us take the long view of future drought risk in the Southwest—and the picture is not pretty. We hope this opens up new discussions about how to best use and conserve the precious water that we have,” said Julia Cole, University of Arizona Professor of Geosciences and of Atmospheric Sciences.

The study, “Assessing the Risk of Persistent Drought Using Climate Model Simulations and Paleoclimate Data,” was also co-authored by Cole, David Meko and Jonathan Overpeck of University of Arizona; and Gregory Pederson of the U.S. Geological Survey.

The study by Cornell University, University of Arizona and U.S. Geological Survey researchers will be published in a forthcoming issue of the American Meteoro logical Society’s Journal of Climate.

The National Science Foundation, National Center for Atmospheric Research, the U.S. Geological Survey and the National Oceanic and Atmospheric Administration funded the research.

2014 drought

While the drought continues in some areas, others have been on the opposite end, at least at times, with monsoon rains and flooding.

The month of August finished up with an active weather pattern across the Northern Rockies, Northern Plains, and parts of the Midwest. In Montana, a slowmoving, low-pressure system delivered widespread heavy rainfall and flash flooding during the weekend. Across parts of the Southwest, eastern Great Basin, and intermountain West, locally heavy monsoon rains continued to provide short-term relief to the region.

In contrast, the far West remained in a dry pattern except for some isolated thunderstorm activity in parts of the Mojave Desert in southeastern California. Overall, the seven-day average temperatures in the western U.S. were generally below normal. East of the Rockies, temperatures for the week were above normal—especially across the Southern Plains, Texas, and portions of the Midwest while New England and the Mid-Atlantic states experienced slightly cooler than normal temperatures. In the Midwest, locally heavy rains fell across portions of Iowa, Illinois, Indiana, Kentucky, and Ohio bringing relief to scattered dry pockets in the region. In the Southeast, hot and dry conditions led to further deterioration of conditions across parts of Alabama and Georgia.

Grazing after drought and fires

As of last week, California still had two large fires burning in the northern part of the state. The Happy Camp Complex fire in Siskiyou County had burned over 66,500 acres, and was only 15 percent contained. The July Complex fire had burned over 40,286 acres in Siskiyou County, and was 78 percent contained. A little farther north, in Oregon, the South Fork fire consumed 66,179 acres, before it was completely contained. Three other fires in the state were coming up on 3,000 acres, and still not under control.

Between widespread drought and fires, public grazing in some areas has a new component for the antigrazing advocates. While the two-year rest minimum seems to be the common discussion, a number of states have set up their own regulations.

Nevada’s BLM will make livestock use adjustments due to drought on a case by case basis in compliance with its multiple use mandate and applicable regulations. The state plan is to work “cooperatively” with the “permittee, other stakeholders, and BLM at the local level” and come up with an agreement.

Nevada’s BLM office has some good pointers on discussing future leases—

“Discussions should begin early in the winter, at least three months before turn out or when changes need to be implemented, so the permittee can plan ahead.”

Some relevant topics may include:

• Current conditions, perennial plant production and vigor have been affected by two years of low precipitation. One good winter snowstorm does not negate the impacts of two years of drought.

• Areas not meeting rangeland health standards.

• Fire rehabilitation seedings and other burned areas that are two or three years old and might be opened for use in the coming year.

• Areas that had no or little annual production the previous year, especially due to drought.

• Areas with apparent plant mortality from any cause, persistent drought, Aroga moths, cheatgrass die off areas, uncertain causes.

• Areas with known poor conditions.

• Interactions among herbivores; wildlife, wild horses and burros, and livestock.

• Alternative sources of livestock range or forage.

“Human nature makes drought planning during the winter difficult. People are optimistic that it will rain and snow enough at the right times for a good year. This often results in putting off decisions until the last minute,” Nevada’s BLM points out. — Traci Eatherton, WLJ Editor

 
 


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