Drought conditions affect more than a third of the U.S.

We all know how bad the drought is in California. I never found out the precise differences among the terms “severe,” “extreme,” and “exceptional” drought, but every single part of California is now facing one of these official classifications, according to the U.S. Drought Monitor – the first time that's happened since the monitor's creation 15 years ago.

However, drought conditions extend considerably past the borders of The Golden State and into most of the Southwest, up to the Northwest and out to the Plains States, and have done so for years. Over the past decade, droughts in some regions have rivaled the epic dry spells of the 1930s and 1950s. Currently, 37 percent of the contiguous United States was in at least a moderate drought as of last April, according to Drought Monitor statistics.

But, that tally was even worse last year when the partnership of the U.S. Department of Agriculture, the National Oceanic and Atmospheric Administration (NOAA) and the University of Nebraska, said half of the U.S. was experiencing some level of drought.

"For the Plains and Southwest," the organization said, "it's a pattern that has been persistent for much of the past several years."

At that time, Kansas set the western edge of the drought that was projected to be pushing farther north. The story was even bleaker in the Southern Plains States, "where the heat and drought are even more pronounced and entrenched across western Oklahoma and much of Texas."

Meanwhile, flows in the region's rivers and levels of groundwater "are hurting given the long duration and sustained intensity of this drought, which is now going on close to four years."

The Drought Monitor contains data going back to 2000. Go back further in time and conditions don't sound any better. The Palmer Index from another group within the NOAA stretches back more than a century. According to this index, any 10-year average has been increasing for most of the past 20 years, which, as The New York Times put it recently, is to say, " the country is in the midst of one of its most sustained periods of increasing droughts on record."

Southwest woes

Most of last century’s engineering marvels of dams and reservoirs that helped build a metropolis like Los Angeles out of what was essentially a desert are exactly what helped the rest of the Southwest flourish. No surprise then that the prolonged dry spell and relentless demand for more and more water that's hobbled California are having just as much natural consequences for this part of the U.S.

For example, figures from a researcher named Dean Farr at Western Water (www.deanfarr.com) show huge drops in capacity at Western reservoirs after years of drought. Go online to Farr's site and you'll see dots of various colors speckling California. Each represents a reservoir and the color denotes a percentage of capacity.

But, nothing in California is on par to the size of the two huge red circles in Arizona: Those would be Lake Mead and Lake Powell, the major source of water for farms and cities throughout the Southwest.

When Lake Mead is full, the reservoir reaches an elevation of more than 1,200 feet. But this spring, Lake Mead set a record-low of 1,079 feet. Marinas look like dry dock and mineral lines that show just how far the lake has fallen ring the banks like a bathtub ring. The low marks this year put the reservoir at only 38 percent of its capacity. Officials expect the level to continue to fall with projections showing a drop of another 5 feet by the fall. If the water level stays at this point by next January, officials say they will be forced to ration the amount of water delivered to Arizona and Nevada is much the same way officials in California are doling out water.

Water from Lake Mead and Lake Powell gets divvied up to those two states with Las Vegas obtaining 90 percent of its water from these reservoirs. Also, Arizona may find itself it in a tough bind as a result of federal back-room political dealings made back in 1968 that created the Central Arizona Project, a series of canals that carry water from the Colorado River throughout Arizona. To win support from California, Arizona legislators at the time gave California first dibs on the river's water in the event of a water shortage. For the first time, that shortage looks very real.

Journalist John Fleck (www.inkstain.net) has covered the region's water issues for years. A recent report outlines a few of the effects of such a shortage:

• California, with enough to worry about, won't get any less of its share.

• Las Vegas knows the desert is just at the edge of its entire existence and has already cut water use by around a third in the past 10 years. The city's water authorities have also been busy installing an expensive new intake system that rests lower in the water of Lake Mead in order to continue to tap the water if, as is likely, the reservoir drops lower and puts the original system above the lake.

• In any event, Arizona won't be caught by surprise. Officials have already outlined a plan that would continue to pump water to Phoenix and agriculture, but cut back elsewhere, such as delaying the replenishment of groundwater storage.

The rest of the West

While a lack of rainfall immediately comes to mind when thinking about droughts, water takes on more than one guise than just fluid.

Consider the impact of its somewhat more solid shape for a moment. The U.S. western mountain snowpack, a key source of fresh surface water for the area, were at record low levels due to meager precipitation and a premature spring thaw, said the U.S. Department of Agriculture's Natural Resources Conservation Service last April.

Typically, early April should be the peak time for the amount of snowpack. As a result, many Western states will experience reduced stream flows from runoff leaving the area's already below-average reservoirs for several states running even further on empty. For example, the snowpack by April was nearly gone in Nevada and Utah. In Oregon, more than half of all mountain measurements taken on April 1 recorded bare ground with snowpack in the Cascades having peaked as much as 90 percent below a typical winter's marks.

All this has left reservoir storage as of April 1 at below average in Arizona, Nevada, New Mexico, Oregon and Utah.

Worse before it's better

As dire as the current situation sounds, some researchers sound downright apocalyptic when discussing the future. Droughts in the U.S. Southwest and Central Plains during the last half of this century could be drier and longer than drought conditions seen in those regions in the last 1,000 years, according to a NASA study released last February.

The study is based on projections from several climate models, including one sponsored by NASA. The research found continued increases in human-produced greenhouse gas emissions drives up the risk of severe droughts in these regions.

"Natural droughts like the 1930s Dust Bowl and the current drought in the Southwest have historically lasted maybe a decade or a little less," said Ben Cook, climate scientist at NASA's Goddard Institute for Space Studies and the Lamont-Doherty Earth Observatory at Columbia University in New York City, and lead author of the study. "What these results are saying is we're going to get a drought similar to those events, but it is probably going to last at least 30 to 35 years."

According to Cook, the current likelihood of a “megadrought,” a drought lasting more than three decades, is 12 percent.

If greenhouse gas emissions stop increasing in the mid-21st century, Cook and his colleagues project the likelihood of a megadrought to reach more than 60 percent. However, if greenhouse gas emissions continue to increase along current trajectories throughout the 21st century, there is an 80 percent likelihood of a decades-long megadrought in the Southwest and Central Plains between the years 2050 and 2099.

The scientists analyzed a drought severity index and two soil moisture data sets from 17 climate models that were run for both emissions scenarios. The high emissions scenario projects the equivalent of an atmospheric carbon dioxide concentration of 1,370 parts per million by 2100, while the moderate emissions scenario projects the equivalent of 650 ppm by 2100. Currently, the atmosphere contains 400 ppm of CO2.

In the Southwest, climate change would likely cause reduced rainfall and increased temperatures that will evaporate more water from the soil. In the Central Plains, drying would largely be caused by the same temperature-driven increase in evaporation. This study also is the first to compare future drought projections directly to drought records from the last 1,000 years.

Until this study, much of the previous research included analysis of only one drought indicator and results from fewer climate models, Cook said, making this a more robust drought projection than any previously published. 

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